Jump Stop

Really I should know better than tinkering with vehicle electrics 400km from home at 22:00 after work, in a car park, but alas, no I don't.

I've been using the alternator to charge my leisure batteries as a back up.
By means of running the positives (one from the starter the other from the leisure batteries) to a switch in the dash with the grounds permanently linked. I monitor this with a cigarette-lighter-socket-voltmeter, and regulate it by turning stuff on.
It occured to me last night that because this is a DC system then perhaps linking the negatives may be harmful for the leisure batteries.
I've been noticing a diminished capacity lately, although this "daylight stealing time" may be a factor.
I suspect this is normal as they're nigh on their third year of everyday use and have been much abused from time to time.

Can anyone verify if permanently linking the negatives is harmful and why? (I was working under AC assumptions 'til it dawned on me; DC's an altogether different beast....that and the price of copper)

Meanwhile in another part of town the switch I was using is a 10A 240V 6-pole 4-throw (with only one connection utilised thus far) so I decided earlier to connect up the ground to the counter-part throw enabling a positive and negative make / break. (all concerning wiring on 200A cable). This resulted in my jump stop and some arcing sparking noises.
Followed by a dead ignition, no working lights (off the engine side of things), readings between 30v and 0.8v from the cigarette lighter socket (wired from the hazard lights (always on)). Readings at the battery terminals were 12.4.
I'm inclined to blame the switch because the only modification I made was to the ground and a short in this department would only go back to ground which is what I initially started with. I'll suss it closer to home in a few days. I've checked the continuity of the switch and there's no cross connections.
Good news is; disconnecting EVERYTHING involved and reconnecting only the starter battery to the engine electrics solved the problem (which I also think is strange because I have no EDU to reset, just relays (disconnecting EVERYTHING involved except the starter battery did not work)).
No blown fuses...which reminds me, I ought to put one on the line for the rebuild...say, if I was to use this circuit to jump-start myself off the leisure batteries should the need arise... how big a fuse would I need here? It's a 2.3L engine.

By the way I sincerely believe having terminated jump leads popping out of custom holes in your dash-board is a highly effective theft deterrent for those of you contemplating expensive alarm installations.

Aidan_M_M

Sir Liamalot wrote: »

Really I should know better than tinkering with vehicle electrics 400km from home at 22:00 after work, in a car park, but alas, no I don't.

I've been using the alternator to charge my leisure batteries as a back up.
By means of running the positives (one from the starter the other from the leisure batteries) to a switch in the dash with the grounds permanently linked. I monitor this with a cigarette-lighter-socket-voltmeter, and regulate it by turning stuff on.
It occured to me last night that because this is a DC system then perhaps linking the negatives may be harmful for the leisure batteries.
I've been noticing a diminished capacity lately, although this "daylight stealing time" may be a factor.
I suspect this is normal as they're nigh on their third year of everyday use and have been much abused from time to time.

Can anyone verify if permanently linking the negatives is harmful and why? (I was working under AC assumptions 'til it dawned on me; DC's an altogether different beast....that and the price of copper)

Meanwhile in another part of town the switch I was using is a 10A 240V 6-pole 4-throw (with only one connection utilised thus far) so I decided earlier to connect up the ground to the counter-part throw enabling a positive and negative make / break. (all concerning wiring on 200A cable). This resulted in my jump stop and some arcing sparking noises.
Followed by a dead ignition, no working lights (off the engine side of things), readings between 30v and 0.8v from the cigarette lighter socket (wired from the hazard lights (always on)). Readings at the battery terminals were 12.4.
I'm inclined to blame the switch because the only modification I made was to the ground and a short in this department would only go back to ground which is what I initially started with. I'll suss it closer to home in a few days. I've checked the continuity of the switch and there's no cross connections.
Good news is; disconnecting EVERYTHING involved and reconnecting only the starter battery to the engine electrics solved the problem (which I also think is strange because I have no EDU to reset, just relays (disconnecting EVERYTHING involved except the starter battery did not work)).
No blown fuses...which reminds me, I ought to put one on the line for the rebuild...say, if I was to use this circuit to jump-start myself off the leisure batteries should the need arise... how big a fuse would I need here? It's a 2.3L engine.

By the way I sincerely believe having terminated jump leads popping out of custom holes in your dash-board is a highly effective theft deterrent for those of you contemplating expensive alarm installations.

It makes no difference whether you link both battery's negatives together, or have both of them connected to good permanent chassis earth , which is more usual. Also 220v switches often don't work in my experience. 12v stuff only needs + and - , no "ground". And you should have both batteries fused on the joining link close tongue positive pole. Why not just wire in a heavy duty relay to charge the 2nd battery, switched from the alternator? Safe the other messing. That's the way factory builds are done.

And unless the cabling between the leisure battery and its earth, and to the starter battery is proper heavy stuff like the starter motor cable , you shouldn't use it to jump start the engine. Unless you want a fire.... And you'd need a fuse something in the region of 100-150 amp on the line.

Weird voltage readings of 0.8 to 30 at the cig lighter socket is a sure fire pointer to a bad earthing connection.

And re an alarm alternative , all you need do on an older diesel is put a hidden switch on the wire to the diesel pump. You could use your terminated plug as a switch.

Thanks for the reply Aidan.

The reason for my endeavors was (purely speculative as usual) that the cathodes of the leisure batteries are passively connected to the van electrics potentially increasing their working lifespan unnecessarily, and quickening the DOD. Is this incorrect? (pertaining to the "...and why?", part of the initial query or why not? albeit the case).

When I say ground in reference to DC I mean the negative terminal, direct or indirect connection to it, sorry if that's confusing I thought it was convention. I understand this is closer to the neutral of an AC circuit than the namesake.

Cabling to the switch and returns were starter motor cable...adapted 200amp jump leads (3 x sets (two sends two returns)), although point noted I have 400amp leads ready to go in the toolkit.

The issue with the cigarette lighter voltage is not the earthing it has been working problem free before and since for years...I'm imagining it's relating to a damaged relay between the battery fuse-board end of affairs, or an unfused short elsewhere (athough I'm pretty sure I tested all the haves and have-nots).
The 240v switch being inappropriate makes sense though, perhaps the short was the created by the starter firing, and overwhelming the switch poles.
The weird readings only manifest when the ignition is unresponsive.

Wouldn't start this morning until I reset the battery again so maybe some damage is done, considering the DIY electrics are all disconnected now. If it persists to be an issue I may replace the starter relay (if there is one..) they're a pain to pull out so hopefully it'll behave if I just put it back the way I had it originally (funny how often I experimentally apply that logic).

Reasons I don't want a heavy duty relay, wait...actually I'm the heavy duty relay!

...electronic ones;

- Don't allow for deep cycle charging shortening lifespan of deep cycle batteries.
- Vehicle battery charge regulators overcharge leisure batteries.
- Added stress to alternator beyond spec (kindof-ish...), resultant higher fuel consumption, and more frequent replacement of brushes.
- Starter battery not adequately charging when faced with a series of short runs.
- No excuse to put a big red missile toggle switch on the dash.
- I already bought one that's inappropriate for vehicle applications (despite stating otherwise on the box) and I'm determined to find a use for the one I have before I invest in another.

Aidan_M_M

Sir Liamalot wrote: »

Thanks for the reply Aidan.
1.
The reason for my endeavors was (purely speculative as usual) that the cathodes of the leisure batteries are passively connected to the van electrics potentially increasing their working lifespan unnecessarily, and quickening the DOD. Is this incorrect? (pertaining to the "...and why?", part of the initial query or why not? albeit the case).

1. Another reason why manufacturers never link the batteries when at rest, only when charging from 12v.



2. When I say ground in reference to DC I mean the negative terminal, direct or indirect connection to it, sorry if that's confusing I thought it was convention. I understand this is closer to the neutral of an AC circuit than the namesake.

2. Correct, although I'm much more tuned into DC than AC!





3. The issue with the cigarette lighter voltage is not the earthing it has been working problem free before and since for years...I'm imagining it's relating to a damaged relay between the battery fuse-board end of affairs, or an unfused short elsewhere (athough I'm pretty sure I tested all the haves and have-nots).

3. It worked fine til the other night? I'd still suspect a bad or burnt connection if you're getting weird voltage readings. Try test the voltage with a load applied, ie phone charger, and using its own earth and then an independent one, key switch is a safe one.



4. The 240v switch being inappropriate makes sense though, perhaps the short was the created by the starter firing, and overwhelming the switch poles.

4. Could be likely. 220v would use a lot less amps for the same

5.Wouldn't start this morning until I reset the battery again ....

5. How do you "reset the battery"?



Reasons I don't want a heavy duty relay, wait...actually I'm the heavy duty relay!

...electronic ones;

- Don't allow for deep cycle charging shortening lifespan of deep cycle batteries.
Yes they do, sure they only link the batteries on 12v, not 22ov, and the alternator won't do a deep cycle charge anyways unless you fit a charge controller.

- Vehicle battery charge regulators overcharge leisure batteries.
Only really a problem with dry cell, gel batteries, and when they are being charged from very low states.


- Added stress to alternator beyond spec (kindof-ish...), resultant higher fuel consumption, and more frequent replacement of brushes.
I doubt the Merc has a bad alternator , but I've only gotten probably 10 alternators rebuilt in the last 10 yrs, and none of them were heavy duty. Most alternators are under stressed.
Fuel consumption is nit an issue , friends with panel vans are not noticing any difference to friends with campers in mpg. It'd be no worse than driving with the lights on. Remember you're only heavily charging the battery for a short time, not constantly on a run.

- Starter battery not adequately charging when faced with a series of short runs.
Again not an issue unless you've a bad alternator. They give the same output at Idke as at high rpm.


- No excuse to put a big red missile toggle switch on the dash.

True ,.... Tho u could use it for isolating the ejector seats ? Lol


- I already bought one that's inappropriate for vehicle applications (despite stating otherwise on the box) and I'm determined to find a use for the one I have before I invest in another.

Bloody phone , couldn't quote and breakdown your post.

1. The reason for my endeavors was (purely speculative as usual) that the cathodes of the leisure batteries are passively connected to the van electrics potentially increasing their working lifespan unnecessarily, and quickening the DOD. Is this incorrect? (pertaining to the "...and why?", part of the initial query or why not? albeit the case).

1. Another reason why manufacturers never link the batteries when at rest, only when charging from 12v.



* Sorry yeah that was perhaps vague. By endeavours I mean adding a make/break ground to my already existing switch.
Hold on, does that mean you are now agreeing that permanent linking the grounds is harmful...I'm confused? Or that I wasn't explaining myself very well.
I'm still hoping for a scientific explanation for this be it yes or no.
Niloc? Any thoughts if you see this?
By cathodes I mean the negative terminals while the battery is discharging.


2. ... I'm much more tuned into DC than AC!

* Vice versa



3. The issue with the cigarette lighter voltage is not the earthing it has been working problem free before and since for years...I'm imagining it's relating to a damaged relay between the battery fuse-board end of affairs, or an unfused short elsewhere (athough I'm pretty sure I tested all the haves and have-nots).

3. It worked fine til the other night? I'd still suspect a bad or burnt connection if you're getting weird voltage readings. Try test the voltage with a load applied, ie phone charger, and using its own earth and then an independent one, key switch is a safe one.

* Perhaps it worked fine at the time too I suspect I may have wired the equivalent of a spanner across the battery terminals.

* It's returned to an anticipated healthy range after I charged up the starter battery, and pulled out the sheniganary.
...which key switch?
Honestly forget about the cigarette lighter, imagine it as a post electrical distribution meter point, it's an isolated circuit from the one I'm struggling with. It was anamalous concurrently with everything else electrical at the time.


The 240v switch being inappropriate makes sense though, perhaps the short was the created by the starter firing, and overwhelming the switch poles.

4. Could be likely. 220v would use a lot less amps for the same

* Indeed.
It's worked fine until I put the ground link in on a seperate throw...induction maybe?
It was in the off position at the time.
I've used it before starting the engine (without the ground throw) no probs.

5. How do you "reset the battery"?

*Perhaps reset the everything connected to the battery is more accurate.

Disconnect the battery terminals to the engine wait a moment, reconnect, cross fingers, turn ignition.


...electronic ones;

Don't allow for deep cycle charging shortening lifespan of deep cycle batteries.
Yes they do, sure they only link the batteries on 12v, not 22ov, and the alternator won't do a deep cycle charge anyways unless you fit a charge controller.

* Deep cycle batteries need to be run down before recharge; topping them up every-time you turn the engine on ultimately damages their memory and longevity.


- Vehicle battery charge regulators overcharge leisure batteries.
Only really a problem with dry cell, gel batteries, and when they are being charged from very low states.

* hrmmm...
...because of the heat?
I rather use the right tool for the job thus have preference for mains charging with engine charging only in times of need.

I doubt the Merc has a bad alternator , but I've only gotten probably 10 alternators rebuilt in the last 10 yrs, and none of them were heavy duty. Most alternators are under stressed.

* Me neither I replaced it 4 month's ago.
and it's a 65amp more than capable...however it's wear and tear.

Fuel consumption is nit an issue , friends with panel vans are not noticing any difference to friends with campers in mpg. It'd be no worse than driving with the lights on. Remember you're only heavily charging the battery for a short time, not constantly on a run.

* I agree it's negligable but still ecological. That's enough for me.


- Starter battery not adequately charging when faced with a series of short runs.
Again not an issue unless you've a bad alternator. They give the same output at Idke as at high rpm.

* I mean starting and stopping frequently where the current drawn is not replaced in charge time causing plate sulphation.

- No excuse to put a big red missile toggle switch on the dash.

True ,.... Tho u could use it for isolating the ejector seats ? Lol




Basically I don't want a relay, I want a user controlled system that does the same job with more discretion.

I wasn't emphasising the gravity of these issues so much as stating they were concerns. Some obviously more than others.


Bloody phone , couldn't quote and breakdown your post.

Ha, mine neither!

The penny just dropped.
It's the cold weather that's reducing the capacity...ah...gobsh1te!
Right back to plan A. (switched live only)

Aidan_M_M

Sir Liamalot wrote: »

1. Another reason why manufacturers never link the batteries when at rest, only when charging from 12v.



* Sorry yeah that was perhaps vague. ..
Hold on, does that mean you are now agreeing that permanent linking the grounds is harmful...I'm confused?
By cathodes I mean the negative terminals while the battery is discharging.

No , I meant only the Positives are linked whilst charging from the alternator , the negs are attached to permanent chassis earths , and hence constantly connected .


The 240v switch being inappropriate makes sense though, perhaps the short was the created by the starter firing, and overwhelming the switch poles.

4. Could be likely. 220v would use a lot less amps for the same

* Indeed.
It's worked fine until I put the ground link in on a seperate throw...induction maybe?
It was in the off position at the time.
I've used it before starting the engine (without the ground throw) no probs.

Sorry , ground throw? Not being an AC man , what's that? Just curious..



...electronic ones;

Don't allow for deep cycle charging shortening lifespan of deep cycle batteries.
Yes they do, sure they only link the batteries on 12v, not 22ov, and the alternator won't do a deep cycle charge anyways unless you fit a charge controller.

* Deep cycle batteries need to be run down before recharge; topping them up every-time you turn the engine on ultimately damages their memory and longevity.

TBH , that's the letter of the law according to the battery suppliers , but sometimes what we see in the "real world" contradicts that!
Although I'm not a fan of true deep cycle gel batteries , I find the Lead Acid ones more stable in the long term . And they're still fitted by lots of factory manufacturers.


- Vehicle battery charge regulators overcharge leisure batteries.
Only really a problem with dry cell, gel batteries, and when they are being charged from very low states.

* hrmmm...
...because of the heat?
I rather use the right tool for the job thus have preference for mains charging with engine charging only in times of need.

I doubt the Merc has a bad alternator , but I've only gotten probably 10 alternators rebuilt in the last 10 yrs, and none of them were heavy duty. Most alternators are under stressed.

* Me neither I replaced it 4 month's ago.
and it's a 65amp more than capable...however it's wear and tear.

Fuel consumption is nit an issue , friends with panel vans are not noticing any difference to friends with campers in mpg. It'd be no worse than driving with the lights on. Remember you're only heavily charging the battery for a short time, not constantly on a run.

* I agree it's negligable but still ecological. That's enough for me.

Point taken , You'll be happy to hear my pet projects are water harvesting , and replacing lamps with LEDs and lo-energy bulbs!


- Starter battery not adequately charging when faced with a series of short runs.
Again not an issue unless you've a bad alternator. They give the same output at Idke as at high rpm.

* I mean starting and stopping frequently where the current drawn is not replaced in charge time causing plate sulphation.

but realistically , do you do a lot of short hops?

-!

I've a feeling if we got sitting down we could bounce ideas and opinions off one another for ages....:)

Sorry , ground throw? Not being an AC man , what's that? Just curious..

I was still referring to DC here.
The switch (designed for AC while being used for DC) has 6 poles (contacts)
allowing two on positions on four circuits. 1 (up), 0 (centre), 1 (down) (where 1 is on and 0 is off).
Lets the call the contacts the 1-6.
And they appear;

1 2
3 4
5 6

In the Up position 1 & 3 are enabled (on) and 2 & 4 are enabled (throws 1 and 2)
In the Mid position everything is off
In the Down position 3 & 5 are enabled and 4 & 6 (throws 3 and 4)

This allows for the wiring of 4 circuits if they can share a positive or negative.
I call the switch making/breaking a circuit a throw.
Now in this case I have only used one (currently...just the positives).

Disaster arose as per first post when I connected the grounds (negative terminals) via the switch (ground make/break "circuit" or throw) beside the the positives.
So positives on throw 1 and negatives on throw 2.

I now believe the fault was the switch that the internal contacts were too thin and proximate and flattened the starter battery by short circuiting via arcing.

My terminology is probably not the best I as I've not formally studied any of this I just more often than not end up opening broken things to fix them.

TBH , that's the letter of the law according to the battery suppliers , but sometimes what we see in the "real world" contradicts that!
Although I'm not a fan of true deep cycle gel batteries , I find the Lead Acid ones more stable in the long term . And they're still fitted by lots of factory manufacturers.

I'll generally get a extra day from a mains charge than an engine equilavent.
Conditioning charges are important I've been watching the life cycles for years now.
Also the systems are not entirely compatible; starter batteries complete charge at 14.7v (although I've seen my alternator flash 15.0v (the old one))
whereas Deep Cycle want no more than 14.4v.
I use additional dipped lights and/or a laptop charger to keep the output down about 14.1v.

Point taken , You'll be happy to hear my pet projects are water harvesting , and replacing lamps with LEDs and lo-energy bulbs!

tehehe...fair dues
Careful with those low energy bulbs though, some of them are bloody awful looking. Tungsten has the best colour temperature still.
Best not to go for too many white lights as they tend towards the green or blue spectrum.
Natural light is yellow.
Better stick to warm light in dwellings.
The colour of light effects us all psychologically.

I'm getting into wind turbines soon as I get an opportunity. It's still very much in the backyard shed stages.

but realistically , do you do a lot of short hops?

In short yes, but I try to leave the engine running when I can. I've been wild camping for years, and between houses again (too much work to spend time looking at the moment).
Here's an example of what I mean.
Often I find that without a "residence" to fall back on it can be 10+ starts a day to get to and from work sometimes involving warehouse runs, groceries (small fridge), fresh water (once every 4-5 days), responsibly dispose of cold ash/grey water/rubbish/recycling and maybe a social call, maybe diesel, maybe bank etc.
Now say for instance my leisure batteries were 12.2v (25%) and my starter battery is 12.9 (100%). My leisure batteries are 250ah whereas my starter is 75ah. If I was to use a relay instead of a switch let's face it the starter battery is doing all the work turning the engine, on top of this the bulk of the charge going to the leisure batteries is not from the alternator but from the starter battery until they balance themselves out which will not sufficiently happen in 30 minutes and compounding this the leisure batteries are soaking up the charge coming off the alternator too.
And whereas my carbon-fiber deep cycle batteries don't care about being lowered to 12.0v (as long as they are charged within a few days or maybe a week) the starter is getting thrashed below 12.3v/12.4v and reducing capacity from sulphation.

I intend to have all my batteries working for the promised 5 years.


I've a feeling if we got sitting down we could bounce ideas and opinions off one another for ages....

...likely so...did I mention I have a fridge needs a service soon...great craic getting at the back of that:rolleyes:

Aidan_M_M

I've small fingers! and if all else fails any fridge that was installed , can be un-installed!

It can be uninstalled alright with a crowbar, along with a cabinet, gas hobs, oven, even a kitchen sink .
I didn't know they had to be serviced when I fitted it. The vents aren't detachable I recall losing patience at that point and driving them home with a plank and a lump hammer.

I'll pm you once we get the right side of Christmas.