Another 12v Upgrade thread...

CubicleDweller

Hi All,

I'm looking to upgrade the leisure battery and the associated gubbins in my motorhome, and I'm hoping to get some advice on how to proceed. It may be a small job or a much larger one, if it includes solar panels, controllers, chargers and what-not.

First, let me describe the current setup:

The van is an old one - a 1994 Hymer S580. It's built on a Mercedes chassis - I think it may be a 310D, I'm not sure. It has automatic transmission and a 2.9 litre 5-cylinder diesel engine which is supposed to be bullet-proof. No turbo.

One unusual feature of the van is the fridge; it's a 12v compression fridge, rather than the usual 3-way absorption type. It works really well, and I want to keep it - but it needs a lot of 12v capacity. It's rated at 5A, but it's hard to know what it's actual usage over a 24-hour period is.

We would like to be able to spend several days wild-camping without driving. (Let's say three days at a time.) As well as the fridge we have a 12v TV (rated at 50W max) that we'd like to be able to use for a couple of hours each evening, and the usual phones and laptops that need charging, along with LED lighting and a water pump.

The current leisure battery is just a standard starter battery and I think it needs replacing. I flattened it a couple of times in the past - down below 11 volts - and I think it has lost a lot of capacity. In any case it was never big enough to keep things running for as long as we'd like.

The battery is charged from 3 different sources; alternator, mains charger and solar panels.

I think there is a split charge relay that lets the alternator charge the leisure battery after the started battery is charged.

The mains charger is old, like the van; it's a Schaudt "LA 140 Z". I've downloaded a PDF manual, but it's in German. The charging current seems to be "7A arithm. Mittelwert, 10A eff". And the faceplate has "IWUoUW" which I gather is some sort of charging characteristic, whatever that is.

The solar panels are also fairly antique. There are two of them. They're Siemens brand and the model is "ProCharger PC-4JF". The rated current, voltage and power of each is 4.4A, 17V and 75W. They're big - 47.3" by 20.8". (Yes, the manual has measurements in inches. Quaint, eh?) They seem to be connected through two separate devices labelled "Laderegler mit Gasungssteuerung" which google translates as "charge controller with gas control". I haven't been able to find any manual or specs for those.

So - I have a nominal 150W of solar power from two big panels, and charge controllers and a mains charger that are probably fairly dumb and low-powered. I've attached a few photos showing parts of the system.

I can see various ways of improving this system:

• replace the single leisure battery with two or more deep-cycle batteries. There is a low-level cupboard that we don't use - close to the existing battery compartment - which could hold a couple of batteries. But what type to buy? Which make/model and how many?
  
• replace the solar panels with higher-powered modern versions. Can I get ones that are the same size, so that I can re-use the mounting brackets without making more holes in the roof? Would the existing cabling be up to it?
  
• replace the mains charger with a modern "smart" one, with higher capacity.
  
• replace the charge controllers with a more modern one. MPPT? Which make/model?

What parts of this system should I upgrade, and how, to get the most bang for my buck? I'm willing to do most of the work myself, so it's mainly about the cost of the parts. And it would be good to know where to get the parts, of course.

I realise that there are many possible answers, depending on how much I want to spend. So, lets say I had a budget of 500 euro - what would be the best way to spend that? What would a "no expense spared" version look like, and what would it cost?

Any and all suggestions are welcome. Please try to keep it simple, though - I'm fairly new to this stuff...

Thanks, in advance, for any information you can share!

jace_da_face

Well allow me to break the awkward silence until Liam gets here. As your fridge could be consuming about 30Ah/ day - assuming compressor runs for about a quarter of the time - upgrading your solar and adding new batteries is a great start.

You could replace your current panels with two 100W panels. A common form factor on 100W panels is about 1050 mm x 540 mm. If my conversions are correct, such a panel is about 15 cm shorter, and 1 cm wider, than your existing ones. Judging by the photo of your roof, they should sit in place of yours. At 1 cm wider it doesn’t look like there would be an overhang. But measure again just to be sure. It also looks like you could add another two over the cab area too. That would give 400Watts. You could also just keep your existing panels and add two 100W. That would still give 350W , not bad, and the satisfaction of reusing your existing panels. But if maximum watts per square foot is what you want, then replace. The charge controller arrangement would depend a lot on what you ended up with in terms of panel types. If all panel voltage specifications matched, everything could run of one charge controller for example. If your current panels and controllers are working, I would just add two new panels on a dedicated controller.

You might be able to reuse a couple of your mounting brackets on the inside but be prepared to remove and reposition brackets. I personally wouldn’t drill holes for the brackets. I used an adhesive - Sikaflex 521 - to stick down PVC corner brackets and for extra measure I mounted some aluminum brackets with 3M VHB tape to the roof which were drill screw fastened to the panel. In hindsight, one of those methods by itself would probably have done the job. But that is your choice, I take no responsibility for any panel that could come unstuck as a result of this advise. I know mine is not coming off anytime soon.

Best of luck.

Awkward silence? P-sah weather's lovely in the south of France!:P
I don't do long replies on phones.

How much do you think you will use the system and how much autonomy do you need CD? What's the expected daily loads.

€500 will get you a DIY battery and a solar controller.
No expense spared well...probably around €8k I'd start running outtov ideas

After a brief look I'd keep the solar panels but mount them where they're not shaded. I'd overhaul the rest. No offence none of if looks inspiring it's heavy handedly undercharging.

Normal services will resume in a week.

CubicleDweller

Thanks for the replies, folks.

jace_da_face wrote: »

Well allow me to break the awkward silence until Liam gets here.

Glad you did. I was beginning to wonder...

As your fridge could be consuming about 30Ah/ day - assuming compressor runs for about a quarter of the time - upgrading your solar and adding new batteries is a great start.

Yes, I think a bigger battery bank and more solar are essential.

The charge controller arrangement would depend a lot on what you ended up with in terms of panel types. If all panel voltage specifications matched, everything could run of one charge controller for example. If your current panels and controllers are working, I would just add two new panels on a dedicated controller.

Ah, now this the stuff I don't understand very well. Is it okay to have more than one controller feeding into the same battery? How would that work? If they independently decide to charge the battery at different voltages, does the higher voltage just overrule the lower one, rendering some of the panels useless? Or do they somehow settle on a compromise voltage, and both supply some current?

The controllers I have are pretty ancient so I don't feel they owe me anything. Is there any type of modern controller that is able to make good use of a combination of different panel types?

You might be able to reuse a couple of your mounting brackets on the inside but be prepared to remove and reposition brackets. I personally wouldn’t drill holes for the brackets. I used an adhesive - Sikaflex 521 - to stick down PVC corner brackets...

Yes. I'd be happy to use a good adhesive, especially if I can reuse the existing brackets on one side. Filling the holes left by the brackets I remove will be a job for another Sikaflex number, I imagine.

Best of luck.

Thanks!

Sir Liamalot wrote: »

Awkward silence? P-sah weather's lovely in the south of France!:P
I don't do long replies on phones.

Don't blame you - neither do I. Glad you're getting good weather there. Are you in your van? Your batteries must be chokka with all that lovely solar...

How much do you think you will use the system and how much autonomy do you need CD? What's the expected daily loads.

We mostly use the van just at weekends, with a few longer trips of a week or more each year. (This year we're planning our longest trip yet, going to Spain for the month of September.) Daily load is hard to quantify. I'm planning to install a battery monitoring system soon so that I can get some solid numbers on that. But assuming jace_da_face is right about a 25% duty cycle for the fridge - that would give 30Ah/day. Two hours of TV at 50W would be about 8.5Ah if I have my sums right. I don't know how much to allow for lights, phones and laptops. Let's say 50 or 60Ah/day total. Is that reasonable?

We'd like to be able to wildcamp for (let's say) at least 3 nights without EHU or driving. So that would suggest we need a usable capacity of 150 to 180Ah if we want to do that in winter or cloudy weather. Does that equate to a nominal battery capacity of twice that? 300 to 360Ah? Actually, that doesn't sound too bad...

The more the merrier, I suppose, but perhaps 300Ah is a good minimum to set for the battery capacity.

€500 will get you a DIY battery and a solar controller.
No expense spared well...probably around €8k I'd start running outtov ideas

Yes, I think 500 may have been too low to be useful. Maybe a grand is more realistic? I don't think I want to go anywhere near 8K though...

After a brief look I'd keep the solar panels but mount them where they're not shaded.

Yes, that satellite antenna can shade one of the panels. I don't even know if it works, it was on the van when I got it. Spent an hour faffing around with a small satellite tuner once without managing to pick up a signal, but that may be because I just didn't know what I was doing. If I knew for sure that it doesn't work I'd be happy to get rid of it. I have a "flying saucer" style antenna for Saorview that I haven't fitted yet - I'll probably put that nearer the back of the van, unless I put new panels down there. Not sure if it would work in Spain. (Spanish TV is quite useful since they went digital - lots of imported shows and movies have an english audio track available as well as Spanish.)

I'd overhaul the rest. No offence none of if looks inspiring it's heavy handedly undercharging.

None taken. I know it's a fairly poor setup, it's what was on the van when I bought it. I'm keen to update or replace it with a much better system, which is why I'm here.

Normal services will resume in a week.

Enjoy the rest of the holiday! Thanks again.

jace_da_face

CubicleDweller wrote: »

Ah, now this the stuff I don't understand very well. Is it okay to have more than one controller feeding into the same battery? How would that work?.

Yes it is. The battery will accept the sum of currents from both chargers.

CubicleDweller wrote: »

If they independently decide to charge the battery at different voltages, does the higher voltage just overrule the lower one, rendering some of the panels useless? Or do they somehow settle on a compromise voltage, and both supply some current?

I wouldn't try to think too hard about the little dance that takes place between the two controllers. One could just be entering a float stage and the other still in absorption, etc.. It should be of little consequence and the controllers should keep pretty synchronised. It is tried and tested.

CubicleDweller wrote: »

The controllers I have are pretty ancient so I don't feel they owe me anything.
Is there any type of modern controller that is able to make good use of a combination of different panel types?

As in accept input from different arrays? I have no idea. I would keep your existing panels. But if you have an opportunity to dump your existing controllers, I'm sure with the addition of two similar panels to your existing i.e. Vmp 17V at say 100W, you could manage with one controller and 4 panels in parallel. The controller would need to be rated for the sum currents (Imp) of all 4 panels.

If your are consuming 60Ah/ day, and you have 300Ah of capacity, you can easily last 3 or 4 days once you start out with a fully charged battery. And that is without any solar. Anything the solar adds above that is a bonus and will help keep your batteries from discharging.

CubicleDweller

jace_da_face wrote: »

Yes it is. The battery will accept the sum of currents from both chargers.
<snip>
It is tried and tested.

Thanks, jace_da_face, that's good to know.

As in accept input from different arrays? I have no idea. I would keep your existing panels. But if you have an opportunity to dump your existing controllers, I'm sure with the addition of two similar panels to your existing i.e. Vmp 17V at say 100W, you could manage with one controller and 4 panels in parallel. The controller would need to be rated for the sum currents (Imp) of all 4 panels.

Yes, that sounds reasonable.

If your are consuming 60Ah/ day, and you have 300Ah of capacity, you can easily last 3 or 4 days once you start out with a fully charged battery. And that is without any solar. Anything the solar adds above that is a bonus and will help keep your batteries from discharging.

Yes, I probably should have made that clear. I was trying to calculate the capacity required to do three nights with no significant solarp - in the worst case scenario. With good weather, I'd hope to get to five nights or more - though the fridge might be working harder in warmer weather, so we won't know till we try it, I guess.

Thanks again.

autumnalcore

CubicleDweller wrote: »

Thanks, jace_da_face, that's good to know.

Yes, that sounds reasonable.


Yes, I probably should have made that clear. I was trying to calculate the capacity required to do three nights with no significant solarp - in the worst case scenario. With good weather, I'd hope to get to five nights or more - though the fridge might be working harder in warmer weather, so we won't know till we try it, I guess.

Thanks again.

From experience for 3 days add iceblocks from your freezer at home and if its a short journey precool the fridge on hookup before you leave this reduces the number of Ah consumed significantly. In warmer weather the additional solar will usually outweigh the additional cooling.

rustynutz

Not trying to hijack your thread OP but I'm in a similar situation to you, I have an old 99 Rimor and I wanted to add solar to charge the leisure battery. I'd rather not replace the original controller/ charger which is an Asilicia unit as it's working fine and controls everything else.

Although the existing controller has an input for a solar panel, I'm guessing that because it's so old, that a modern solar controller would be far more efficient. My question is, can I just set up my solar panels and new controller, and run them alongside the existing charging system? Is there anything I would need to consider? And finally, can anyone recommend a good controller & solar panel set up?

CubicleDweller

autumnalcore wrote: »

From experience for 3 days add iceblocks from your freezer at home and if its a short journey precool the fridge on hookup before you leave this reduces the number of Ah consumed significantly. In warmer weather the additional solar will usually outweigh the additional cooling.

Thanks autumnalcore. Good tips, those. Yes, I need to remember to bring iceblocks, I usually forget that. Unfortunately we don't have the van on hook-up at home; we live in a terraced house and have to keep the van in storage some distance away, with no mains power. But to be honest, the fridge cools down quickly during the initial drive to wherever we're going, without really drawing much from the battery, just running off the alternator. That's a good thing about the compressor fridge; it cools quickly if the power is available.

rustynutz wrote: »

Not trying to hijack your thread OP but I'm in a similar situation to you, I have an old 99 Rimor and I wanted to add solar to charge the leisure battery. I'd rather not replace the original controller/ charger which is an Asilicia unit as it's working fine and controls everything else.

Although the existing controller has an input for a solar panel, I'm guessing that because it's so old, that a modern solar controller would be far more efficient. My question is, can I just set up my solar panels and new controller, and run them alongside the existing charging system? Is there anything I would need to consider? And finally, can anyone recommend a good controller & solar panel set up?

No problem, rustynuts. I'll be interested in seeing any answers you get, as I need recommendations for panels and controllers, too.

jace_da_face

rustynutz wrote: »

Not trying to hijack your thread OP but I'm in a similar situation to you, I have an old 99 Rimor and I wanted to add solar to charge the leisure battery. I'd rather not replace the original controller/ charger which is an Asilicia unit as it's working fine and controls everything else.

Although the existing controller has an input for a solar panel, I'm guessing that because it's so old, that a modern solar controller would be far more efficient. My question is, can I just set up my solar panels and new controller, and run them alongside the existing charging system? Is there anything I would need to consider? And finally, can anyone recommend a good controller & solar panel set up?

Just to be clear, but do you have existing solar panels(s) rustynuts? If not, you can absolutely add solar charging to compliment your charging system. And if you do already have solar charging, you can still add additional panels. I’m guessing that you have a charger that can accept solar input but you do not have solar panels? If so, I would add solar panel(s) with your existing charger and see how it goes. But you might find that to buy a solar setup, that you’re getting a good deal to include a new charge controller. In which case it would just compliment what you already have.

CubicleDweller

CubicleDweller wrote: »

it's a 12v compression fridge, rather than the usual 3-way absorption type. It works really well, and I want to keep it - but it needs a lot of 12v capacity.

You'll need 10x more energy capacity to run absorption.

CubicleDweller wrote: »

It's rated at 5A, but it's hard to know what it's actual usage over a 24-hour period is.

15Ah to 40Ah depending on climate, usage, ventilation and added insulation.

CubicleDweller wrote: »

(Let's say three days at a time.)

Easy peasy.

CubicleDweller wrote: »

The current leisure battery is just a standard starter battery ...
In any case it was never big enough to keep things running for as long as we'd like.

Sadly batteries get an awful bad rep. Usually, the charger/base load/design load is to blame for poor capacity.

CubicleDweller wrote: »

I think there is a split charge relay that lets the alternator charge the leisure battery after the started battery is charged.

Probably runs between 7A & 15A @ 13.6V before hab loads.
You could get a 5X improvement without too much trouble.

CubicleDweller wrote: »

The charging current seems to be "7A arithm. Mittelwert, 10A eff". And the faceplate has "IWUoUW" which I gather is some sort of charging characteristic, whatever that is.

It'll probably deliver that as load current but not charge. I delete them they're not worth keeping.
IUoU means 3 stage....doesn't mean it's good just that it's not a linear PSU.

CubicleDweller wrote: »

I haven't been able to find any manual or specs for those.

I can tell from the photo they're not worth salvaging. A good one will absorb at 14.8V

CubicleDweller wrote: »

But what type to buy? Which make/model and how many?

I'd go for
2 x Flooded Crown or Trojan 6V.
220Ah + 150W PV with a MorningStar charge controller + Ctek MXS 7. Isolate PV when mains charging.

CubicleDweller wrote: »

• Would the existing cabling be up to it?

What is the existing cabling?

CubicleDweller wrote: »

• replace the mains charger with a modern "smart" one, with higher capacity.

If you find one let me know.

CubicleDweller wrote: »

• replace the charge controllers with a more modern one. MPPT? Which make/model?

MorningStar

CubicleDweller wrote: »

What parts of this system should I upgrade, and how, to get the most bang for my buck?

Demount roof hardware casting shadows on PV or move PV.
New PV Charge controller (15A PWM (225W PV) beats 10A MPPT (150W PV))
Split Charge Cable & Contactor Upgrade
12V laptop PSUs
Mains Charger with load compensation upgrade.
Fridge Insulation.

CubicleDweller wrote: »

it would be good to know where to get the parts, of course.

I use;

Ebay.co.uk
Electrical Wholesalers
Auto-electrical wholesalers
Radionics
Amazon.co.uk
Co-op Stores

Avoid rip-off merchants camping & caravan stores, halfrauds or marine chandlers

CubicleDweller wrote: »

Is it okay to have more than one controller feeding into the same battery? How would that work? If they independently decide to charge the battery at different voltages, does the higher voltage just overrule the lower one, rendering some of the panels useless? Or do they somehow settle on a compromise voltage, and both supply some current?

Yes if they are the same with the same settings. Otherwise, it gets messy performs absorption poorly. It kindov works but will cause premature battery failure.

CubicleDweller wrote: »

Your batteries must be chokka with all that lovely solar...

~50Ah a day from 150Wp

CubicleDweller wrote: »

50 or 60Ah/day total. Is that reasonable?

Entirely doable but frugal for two
+15Ah for an inverter

If you fix the PV it should give you at least 30Ah a day most days.

CubicleDweller wrote: »

The more the merrier, I suppose, but perhaps 300Ah is a good minimum to set for the battery capacity.

I run 365days from 235Ah + 150W solar + I can pull 90A continuous to the service battery from a 150A alternator.
I'm adding 110W solar to support a compressor fridge.

CubicleDweller wrote: »

Yes, that satellite antenna can shade one of the panels. I don't even know if it works,

Delete it so, it's fouling half your array.


The battery compartment is a mess. The isolator is a liability, there's too many cables on the posts, not enough fuses, the colours are incorrect, the gauges don't match and there's no cable stress relief or labels.

Try to keep it to one large (power) cable and one or less small (sense) cable per post in the battery locker and do the rest from bus bars. Every +ive needs a fuse appropriate to the conductor CSA.

jace_da_face wrote: »

you can easily last 3 or 4 days once you start out with a fully charged battery.

Fully charging lead acid is no easy task the legacy kit only goes to 75% SOC, I've never seen a mains charger do better than 95%, alternators simply don't run long enough.

rustynutz wrote: »

Although the existing controller has an input for a solar panel, I'm guessing that because it's so old, that a modern solar controller would be far more efficient.

Age isn't the issue. It's the hardware architecture that's the problem they're woefully poor.

rustynutz wrote: »

My question is, can I just set up my solar panels and new controller, and run them alongside the existing charging system? Is there anything I would need to consider?

Yes.
Unplug the mains.
Get a battery monitor.

jace_da_face

Sir Liamalot wrote: »

Fully charging lead acid is no easy task the legacy kit only goes to 75% SOC, I've never seen a mains charger do better than 95%, alternators simply don't run long enough.

Be that as it may, the premise of the statement is true, “if you start out with a full battery”. Attention just needs to go to ensuring a full battery at the start of a road trip. If the van is parked up for days between trips, the solar should be getting the battery fully charged. Verified of coarse with a battery monitor you trust.

In an ideal world with honest manufacturers that would be the case but given that solar controllers are only as good as the design engineer's opinion of how to charge a battery the real world applications vary greatly.

All battery monitors I know of with the exceptions of SmartGauge, Reddarc BMS and the TriMetric 2030 with the SC2030 reset their 100% full setpoint when they read the charger transition from absorption to float.

This means that the battery monitor is calibrated by the charger which might charge to 100% or 75%. In a lot of circumstances, false positives are triggered by dusk light conditions and solar pv.

First one has to verify their charger fidelity with specific gravity readings, then ensure the monitor corroborates this, then trust the meter.

Battery monitors are entirely fallible as they are logical devices monitoring chemical reactions.
A battery efficiency is influenced by depth of discharge, temperature, discharge rate, interval between full charges, age, coulombic efficiency, surface charge/charge rate, battery chemistry, charger absorption set-points, parasitic load etc. etc...

The only way to ensure the battery is fully charged is chemically ie. specific gravity readings.

The upshot of which is I know my battery is fully charged when I use Morningstar Controllers and my monitor reads float at SOC 105% > 120%.
Then I manually reset the counter to 100% at commencement of discharge/departure from dock.

It took me a year to calibrate my TriMetric to hold accuracy over 3 weeks use.

jace_da_face

Well said. To truly understand this dilemma is to realize it is art meets science. Art because it involves intuition on behalf of the observer, followed by reasonable judgement. Battery monitors are just not equipped enough and are not presented with all the parameters needed to judge SOC.

Is it time for smart batteries? Tiny refractometers sitting in each battery cell, measuring electrolyte chemistry and communicating to whoever wants to listen, perhaps?

It's been tried and never took off.
Electronics don't do well in acid baths with corrosive vapours.

It's actually really simple.
Keep buying chargers and binning them until you find one that works as described.
Set up a battery monitor 1:1 efficiency with manual reset, derate plated capacity by 10% (temp. derating & overhead). Ensure it reads zero when zero.
If the battery is old and sulphated you can further compensate efficiency accordingly.

Most monitors are reasonably accurate for a few days between charges. Any minor drift isn't observable until day four and after.

Never trust a meter or charger to tell you what charged is unless verified against your installation.

Once setup correctly there's very little to worry about.

Having said that the TriMetric is the only battery monitor I've used that doesn't annoy me.

jace_da_face

The Sun Gods did speak today so I decided to do a little experiment to demonstrate the effects of partially shading a PV panel.



This is a 60 cell panel, with Isc 9.15 Amps.



With panel resting on one that is already tilted to the sun, I measure a short circuit current of 8.0 Amps. Not bad. The effect of inserting an ammeter across the terminals is to short it out. This will produce the maximum current the panel can produce with the available sunlight. This is quite safe to do as the panel is producing no power. Max current and no power? The magic of current sources!

So with 60 cells wired in series, surely covering just one will bring the circuit current down to a fraction?



Nope. The panel's internal bypass diodes kick into operation and do what they were designed to do. Still getting 8 Amps.



With just a single row (5 cells) shaded, we are down to 22mA!!!



I had to un-shade just 3 cells to get the current back.

The bottom line: A small amount of shading on a single panel can your take your panel offline. If you have more than one panel wired in series, a small amount of shading of just one panel can bring your system performance down to near zero. So watch out for obstacles like roof lights. And unless there is a really good reason, keep your panels wired in parallel.

It'll be more significant under load.

CubicleDweller

Thanks jace_de_face and Sir Liamalot for those informative posts. This stuff looks like it can get really complicated if you want to get into it in detail.

That experiment with covering up parts of a panel is very interesting. I had heard that even partial shading can have a dramatic effect on output, but that shows it very well. Thanks for taking the time to do that.

I'm not sure what to do yet. I think I need to spend more time at the van with a multimeter and see what the existing panels are doing. (I'll also look at removing that satellite antenna.)

In the short term I'll probably replace the leisure battery with something of much higher capacity - two or three batteries for a total of 300Ah or so. That should mean that we can do two or three days easily if we start with them fully charged. And yes, the solar should mean that we always start out with a reasonably good charge. On longer trips I suppose we can spend one night in a campsite with EHU every 3 or 4 days if the solar and alternator aren't doing enough. Then I can see how that goes and decide if more solar is worth investing in.

One thing worries me a little; if I spend a fair amount of money on new batteries and don't upgrade anything else (for now), is there a danger that the existing mains charger or solar setup will somehow damage the new batteries? If they're going to be okay - just not charged as quickly as I'd like - then I'm happy to live with that for a while. I can keep a close eye on them and avoid discharging them too far. But if they're likely to have their life shortened by being used with that old charging setup then I'll have to consider upgrading more stuff right from the start.

Can anyone recommend a supplier to buy new batteries from, by the way?

Again, thanks for all of the answers. This thread has been an education already!

Yurp that gubbins will absolutely cause battery atrophy. It's "designed" to be on perma-mains not cyclic use. Your battery will lead a life of degenerative cycling & diminishing returns. Your absorption setting is too low, too short and non- adjustable. It'll take months to charge.

All you need to start is to get a decent solar controller and worry about the rest later. The solar will remedy the short-comings of the rest in the downtime as long as you park it with some solar exposure on the roof and the shadows to the North.

Most people seem to spend a lot on PV and then get the cheapest controller they can find. This is like getting a sports car and saving money on tyres.

The antenna isn't the only issue. The PV ought to be at least level with the skylight. If you open it you'll have more shading issues.

CubicleDweller

Sir Liamalot wrote: »

Yurp that gubbins will absolutely cause battery atrophy. It's "designed" to be on perma-mains not cyclic use. Your battery will lead a life of degenerative cycling & diminishing returns. Your absorption setting is too low, too short and non- adjustable. It'll take months to charge.

Dammit. I'm glad I asked.

All you need to start is to get a decent solar controller and worry about the rest later. The solar will remedy the short-comings of the rest in the downtime as long as you park it with some solar exposure on the roof and the shadows to the North.

Okay - some good news. What should I be looking for in a controller? Could you recommend a particular brand or model?

Most people seem to spend a lot on PV and then get the cheapest controller they can find. This is like getting a sports car and saving money on tyres.

That makes sense.

The antenna isn't the only issue. The PV ought to be at least level with the skylight. If you open it you'll have more shading issues.

Good point - hadn't thought of that. Will see if I can raise them somehow.

Thanks again.

CubicleDweller

CubicleDweller wrote: »

Could you recommend a particular brand or model?

CubicleDweller

Thanks, Sir Liamalot.

I've had a look online - first place I found that has the 30A metered version for GBP 100. Not too bad.
http://www.windandsun.co.uk/products/Solar-Charge-Controllers-/Morningstar-Charge-Controllers#13518

I like the idea of the built-in meter.

The whole PWM/MPPT debate has me confused. Some say the extra cost of MPPT is not worth it, others swear by it. One argument I've seen is that in poor lighting conditions - when the output of the panel falls below some threshold or other - the PWM will produce nothing whereas the MPPT will at least provide a small trickle of current. I take it you're not convinced about that? I'm skeptical myself...

autumnalcore

If you have the space for the price difference of PWM vs MPPT you could get another 100w of panel which probably exceeds any gain with mppt unless you have a large array.

On the plus side you can drive a morningstar mppt controller with a dc power supply to double up as an excellent quality mains charger. with fancy metering.

Furthermore in most instances gains better than MPPT can often be achieved by simply using more energy efficient appliances/power supplies and reduction of the base load.
I don't generally advocate solar controllers with display meters for the simple reason that if they are installed correctly they are not useful because they ought to be mounted next to the battery to mitigate regulated voltage drop rather than anywhere visable.
The other drawback of solar controller meters is they can't show you the whole system info like a battery monitor can.

In the case of the ecoflex the display can be used for editing custom profiles which will save you ~€80 in USB interfaces.

The remote temperature sensor is an essential piece of kit. I notice up to 15°C disparity between my controller temp sensor and my remote temp sensor. This translates to 0.45V error which is highly significant.

This is because a lump of lead takes a lot longer to heat up than free flowing air in my leckytronics department.

There's a lot of manufacturers that don't have this facility, it's a sure sign they're spoofers not serious contenders and they only include them so they can claim the feature in their schlick sell sheets. Ironically I've seen certain offending manufacturers offer add-on temp sensors for their meters but not their chargers. :rolleyes: Isn't that right Victron?

I make MS temp sensors for <€1.
I may also have the world's only sunsaver with an operational remote transistor temp sensor. :cool:

10A is all you need for your existing array. You won't see more than 8A flat mounted and that gives you 20% overhead. If you want upgradeability or need higher capacity on LVD/HVD then 20A is a good choice.

CubicleDweller

autumnalcore wrote: »

If you have the space for the price difference of PWM vs MPPT you could get another 100w of panel which probably exceeds any gain with mppt unless you have a large array.

Fair point. My roof's not full yet. But if MPPT meant you'd have even a small trickle of current on a winter's day in Ireland when PWM would produce nothing, maybe it's worth the extra? Or am I just kidding myself, and the best-case power from a reasonable setup under those conditions is still negligible?

On the plus side you can drive a morningstar mppt controller with a dc power supply to double up as an excellent quality mains charger. with fancy metering.

Oh, that's interesting - I hadn't heard that before. What kind of DC power supply would be suitable for use like that? Would an old PC PSU work? I may have a few of those knocking around. If I can use a dumb, cheap (free?) PSU and avail of the "smarts" in a single charging controller, that's an appealing option. (Some info on ATX PSUs:http://web2.murraystate.edu/andy.batts/ps/PowerRatings.htm
https://makezine.com/projects/computer-power-supply-to-bench-power-supply-adapter/) The produce several voltages, but the highest is +12V. Could an MPPT controller do anything uselful with that?

Sir Liamalot wrote: »

Furthermore in most instances gains better than MPPT can often be achieved by simply using more energy efficient appliances/power supplies and reduction of the base load.

True, I guess. I'm replacing lightbulbs with LEDs and so on. The notorious fridge is the big thing, and I don't want to replace that. But I've been learning by trial and error that you don't need to have it turned up to full blast all the time, and pre-frozen stuff from home is useful, and so on.

I don't generally advocate solar controllers with display meters for the simple reason that if they are installed correctly they are not useful because they ought to be mounted next to the battery to mitigate regulated voltage drop rather than anywhere visable.

That makes sense. I suppose a compromise might be to put the controller as close as possible to the battery while still being visible fairly easily - maybe with a bit of neck-craning. And heavy cables...

The other drawback of solar controller meters is they can't show you the whole system info like a battery monitor can.

Battery monitors - I know very little about those. Before I started reading up on this stuff I was actually planning to build something like a primitive battery monitor using a Raspberry Pi and an ADC with a current shunt. (A Pi is more power-hungry than I'd like - an Arduino might be more suitable - but I know how to work with a Pi, and how to hook it up to the internet using an old Android phone. Remote battery monitoring would be handy given that the van is usually in storage about 40 minutes' drive from home.) I'm not sure if that approach is viable. Apart from the Pi's power consumption, the circuitry needed started getting complicated pretty quickly when I looked into it. Instrumentation amplifiers and special ICs called "coulomb counters" came into it. I'll probably build something just for interest, but I doubt it will work as well as a commercial product. Can you recommend one?

In the case of the ecoflex the display can be used for editing custom profiles which will save you ~€80 in USB interfaces.

The remote temperature sensor is an essential piece of kit. I notice up to 10°C disparity between my controller temp sensor and my remote temp sensor. This translates to 0.3V error which is highly significant.

This is because a lump of lead takes a lot longer to heat up than free flowing air in my leckytronics department.

I guess this sensor lets the controller accurately measure the battery's temperature, so it can properly calculate its state of charge? (I'm learning, slowly... )

There's a lot of manufacturers that don't have this facility, it's a sure sign they're spoofers not serious contenders and they only include them so they can claim the feature in their schlick sell sheets. Ironically I've seen certain offending manufacturers offer add-on temp sensors for their meters but not their chargers. :rolleyes: Isn't that right Victron?

I make MS temp sensors for <€1.
I may also have the world's only sunsaver with an operational remote transistor temp sensor. :cool:

10A is all you need for your existing array. You won't see more than 8A flat mounted and that gives you 20% overhead. If you want upgradeability or need higher capacity on LVD/HVD then 20A is a good choice.

Okay, you got me - what's the "MS" stand for? I managed to find LVD/HVD on Google, but MS stumped me...

Thanks again, as ever...

autumnalcore

CubicleDweller wrote: »

Okay, you got me - what's the "MS" stand for? I managed to find LVD/HVD on Google, but MS stumped me...

Thanks again, as ever...

Morningstar

CubicleDweller

autumnalcore wrote: »

Morningstar

Doh!

Thanks.:D

autumnalcore

CubicleDweller wrote: »

Would an old PC PSU work? I may have a few of those knocking around

The morningstar mppt controller can only buck not boost so voltage would have to be higher than the charging voltage plus whatever voltage drop is internally you'd probably want 17+ volts. You can connect two atx supplies in series if the 12v grounds are not earthed but then you're looking at two fans etc. Could probably get something quality ex industrial / automation like siemens, weidmuller 24v supply used on ebay cheap if you're not in a rush.

Theres also lost of info on boosting the output voltage from atx supplies on the rc forums, I've never boosted one past 16v volts though you might need to uprate the electrolytics to go to 18v. https://www.rcgroups.com/forums/showthread.php?1383368-PC-ATX-power-supply-unit-18V-400W

CubicleDweller

CubicleDweller wrote: »

But if MPPT meant you'd have even a small trickle of current on a winter's day in Ireland when PWM would produce nothing, maybe it's worth the extra?

A MorningStar PWM controller is probably 400% better than what you have. A MorningStar MPPT controller is 15% better than their PWM controllers by their own claims (which probably means 10% in the real word)

Invest the saving in split charge and mains and you'll have a much better ROI.

I use MPPT it's great but I've exhausted all the low hanging fruit upgrades. My alternator can produce 1.2kW after engine loads, mains works better than any off the shelf solution, everything is led with proportional control & I don't run an inverter for anything but a stoopid absorption fridge.

Remote meters are the solution to solar controller monitoring. Battery monitors are the solution to battery monitoring. The cables between the controller and battery need to be big enough to be <0.4% voltage drop. The further you displace it the less likely they'll fit in the terminals.

CubicleDweller

autumnalcore wrote: »

The morningstar mppt controller can only buck not boost so voltage would have to be higher than the charging voltage plus whatever voltage drop is internally you'd probably want 17+ volts. You can connect two atx supplies in series if the 12v grounds are not earthed but then you're looking at two fans etc. Could probably get something quality ex industrial / automation like siemens, weidmuller 24v supply used on ebay cheap if you're not in a rush.

Ah, I see. I'll have a look on ebay and see what I can find

Theres also lost of info on boosting the output voltage from atx supplies on the rc forums, I've never boosted one past 16v volts though you might need to uprate the electrolytics to go to 18v. https://www.rcgroups.com/forums/showthread.php?1383368-PC-ATX-power-supply-unit-18V-400W

Thanks, but that sounds like more hassle than I'd want. The only thing I seem to remember about electrolytic capacitors is that they can explode if you get the polarity wrong. Distant memories of a very loud bang in a college lab once...:eek:

Sir Liamalot wrote: »

A MorningStar PWM controller is probably 400% better than what you have. A MorningStar MPPT controller is 15% better than their PWM controllers by their own claims (which probably means 10% in the real word)

I'm sure that's true but at this stage I think what I have is fairly irrelevant, it's getting replaced anyway. But I understand what you're saying, it's probably splitting hairs to worry about PWM vs MPPT at this stage. I just worry about spending a fair chunk of money only to later wish that I'd spent some of it on a different controller. Probably worrying too much about this one aspect of the project.

Invest the saving in split charge and mains and you'll have a much better ROI.

Okay. By investing in split charge, do you mean upgrading the alternator? Or are there "smart" versions of the split charge relay? I'm not even sure that I *have* a split charge relay but I've been assuming that I do and that it (and the alternator) can be left as-is.

And for mains: autumnalcore's suggestion of using a fairly dumb DC supply with an MPPT controller has got me wondering. Does that approach only work with MPPT controllers, or could that work with a PWM controller, too? Or what other options would give good results without a huge budget?

I use MPPT it's great but I've exhausted all the low hanging fruit upgrades. My alternator can produce 1.2kW after engine loads, mains works better than any off the shelf solution, everything is led with proportional control & I don't run an inverter for anything but a stoopid absorption fridge.

Remote meters are the solution to solar controller monitoring. Battery monitors are the solution to battery monitoring. The cables between the controller and battery need to be big enough to be <0.4% voltage drop. The further you displace it the less likely they'll fit in the terminals.

Right. Im hoping the leads from the controller to the battery will be under a meter long. Haven't worked out the exact layout yet, though.

Thanks again!

autumnalcore

CubicleDweller wrote: »

Does that approach only work with MPPT controllers, or could that work with a PWM controller, too? Or what other options would give good results without a huge budget?

You'd need a current limited supply otherwise your pwm will lightly go poof.

Solar controller metering in a system with alternator and mains charging reminds me of the life of the Life of Brian 'How many have gone through jailer'