10kWh LifePO4 DIY Battery Addition..... Here is my write up.

Sligobuck

There are way too many blanket statements thrown around in these threads about passive (dissipative) and active (nondissipative) balancing, as in passive BAD and Active GOOD.

The real driver on whether you would need to choose an Active balancer over a Passive balancer is the approach you take to your battery build. There is a clear divide across threads between 2 camps where people decide to go down the route of either one of the following:

The first route is to buy the cheapest battery pack comprising of cells which may come from various different lots with different age/use history and will have different energy capacities when fully charged. With this strategy even with initial top balancing of the pack, you most definitely will need an Active balancer which will need to work hard to maintain balance across these differing cells during their remaining charge and discharge lifecycle.

The second route is to buy a battery pack of high quality cells which cost a little more but will come with real stated energy capacities and be very tight in their comparative energy capacities. With this strategy and after initial top balancing a passive balancer works perfectly since the energy required to keep them in balance by dissipating watts is tiny, this is where passive balancers like the Seplos come into their own.

The energy dissipated by a passive balancer on a good quality battery pack is often less than an active balancer of a lower quality battery pack.

unkel

https://www.boards.ie/discussion/comment/121194051#Comment_121194051

Not sure who that is aimed at, but if at me, then you clearly didn't get my point at all. Even with perfect cells, top balancing them by parallelling will take a very long time. Even with a single paralell cell (so 15 or 16 cells typically, not double, treble, quadruple that, etc.) it will take many weeks. If you have an active balancing BMS, you can just skip this step, bang the cells into the battery in series and let the active balancer balance them over time. This simply is not an option with a passive balancing BMS as it would take months.

johndoe11

This doesnt happen with the Solis S5-EH1P6K-L 6KW inverter, I charged it this morning and it maintained 100a charging for over an hour.

graememk

https://www.boards.ie/discussion/comment/121196181#Comment_121196181

what Software version are you on?, I might see if I can the one i have updated.

irishchris

https://www.boards.ie/discussion/comment/121196181#Comment_121196181

Must be new firmware as I had that particular model and would always throttle back after 15 mins making it effectively a 65a charger for the remaining 2 hours of my smart plan charging.

Contacted solis support several times who tried to convince me that all inverters do this and it was a hardware design that couldn't be changed.

Works you mind putting up screenshot of the hour long amps charging from the app or home assistant as be good to see it in action

I ended up upgrading to sofar hybrid and 100a continuous charging since then without a problem.

Sligobuck

https://www.boards.ie/discussion/comment/121195920#Comment_121195920

Its aimed at everyone who makes blanket statements with regard to active and passive balancing without qualifying the use cases, and you just did above in regards to Top Balancing!

Let me make my argument clear again as applied to top balancing your new pack before building your battery.

Your response above is perfectly reasonable and correct when applied to the first use case which I referred to as "the first route where you buy the cheapest battery cells" in my previous post. Top balancing cells with uneven capacities in a pack is a nightmare and you can just shortcut the process and build the battery with an active balancer and live with reduced capacity until the active balancer eventually gets the best out of a poor batch of cells.

What you left out is that in the second use case which I referred to as "the second route where you buy high quality cells" in my previous post. In this use case Top Balancing these cells with even capacities is way easier and quicker before building the battery. You still need to give yourself about 2 days to do it right but it is worth the effort as you have a high capacity battery once you build it and it takes very little to keep it balanced and this is where you can use an passive balancer to good effect.

unkel

https://www.boards.ie/discussion/comment/121197235#Comment_121197235

2 days to charge and top balance 16 * 300Ah cells in parallel? You obviously have never tried to do this before

Sligobuck

https://www.boards.ie/discussion/comment/121197323#Comment_121197323

Blanket statement's without facts seems to be the default position these days!

I have already done it 4 times on 4 x 280Ah packs and all running fine on Passive balancing for 9 months. A Wanptek 20a 60v charger and good quality EV cells and Bob's yer Unkel....then again maybe not!

Plenty of videos showing how with a 2 step approach, Charge to high state (get into the steep curve) in series checking individual cell voltages with voltmeter as you get there then switch to parallel for final balance.

I'm can already hear the next reply coming saying not everyone can afford to go this route and that is true, but the point I am making which gets lost here is that it can be done and has been done.

unkel

https://www.boards.ie/discussion/comment/121197936#Comment_121197936

I got 5kWh CALBS (8 * 200Ah or thereabouts LOL you got a point there) for what you paid for that charger. Most people who don't have infinite means and do have to care about the pay back time of their system use €40 bench power supplies. And then it takes many weeks to top balance even the best of cells, as pretty much all of us have reported here over the years.

By the way, I simply don't believe you that it only took you 2 days from opening up the cell boxes to having them all at 3.65V, even with that fancy charger you have.

on_the_roots

https://www.boards.ie/discussion/comment/121196181#Comment_121196181

Would you give more details about the firmware version you have please? Seems that you don't have the weakest point of these Solis inverter, which is great.

johndoe11

The firmware is 470044, only got it updated recently as was having some issues. I looked at again on home assistant when I got home, soliscloud seem to show a flat line. It charged at 5kw for about 45mins, then it seemed to move down to charge at 4kw. I couldn't see this on soliscloud.

Jonathan

https://www.boards.ie/discussion/comment/121199866#Comment_121199866

Can you show the battery amps rather than power?

unkel

Better to see the amps as @Jonathan says, but from that graph alone it seems fairly clear you are being throttled after not much more than 30 minutes, albeit not as badly as many others reported.

I didn't realise but someone told me recently the Solis hybrids don't have fans, so passive cooling only? Then surely it is the software that is programmed in such a way that the power is throttled as temp thresholds are being reached. There are only 3 outcomes here:

1. This is genuine, the temps should be adhered to, so it is what it is. Leave it
2. This is genuine, the temps should be adhered to, so a fan needs to be fitted to dissapate the heat better
3. These temps are a bit conservative, so the software (firmware) can be adjusted

SD_DRACULA

https://www.boards.ie/discussion/comment/121200305#Comment_121200305

It is FW limited for sure, it was confirmed by solis support to me back when I had one.

I also had a few fans on top of it keeping it around 40c max even when charging/discharging and still throttled.

But funny enough they did mention it can be "tweaked" via FW so maybe if one cries a lot... 🤣

on_the_roots

Another user reporting 90A continuously for 3 hours with the recent firmware 470044. Seems that this version improves this limitation by quite a bit.

Not sure however if the limitation is only for the value 100A.

https://www.boards.ie/discussion/comment/121196138/#Comment_121196138

https://www.boards.ie/discussion/comment/121200305#Comment_121200305

Solis has confirmed the throttling happens by time (15 min), not by the actual temperature measured, which seems a pretty odd design. I saw some reports from people fitting external fans but makes no difference. This is a hard limitation on the firmware.

johndoe11

Sure here it is, the flat line is 90amps. On reflection, It may have been the BMS reducing the charge rate as the battery was getting close to full.

I'll do it again from empty and see what happens.

Also temperature.

johndoe11

As an aside, solar assistant now supports Solis (with some limitations), so you can now get live data and ditch solis cloud. You just have to build your own cable.

unkel

@johndoe11 - those temps are fairly hot!

johndoe11

It's out in the shed as well - not subject to any additional heating, hopefully once the weather cools down a bit at night they'll drop a bit!

irishchris

https://www.boards.ie/discussion/comment/121200710#Comment_121200710

I would be inclined to put a fan above it linked to home assistant, simple temp stat or on a smart plug toner.

Even when heavily charging my batteries with my old 5G solis the temps peaked at 40-50c.

AmpMan

https://www.boards.ie/discussion/comment/121217348#Comment_121217348

Recently put one of the the sonoff temp controllers in the greenhouse.

Really handy yoke, going to install one at my solar gear when its up and running.

Not sure if sonoff ever sorted their home assistant game out, stopped using it ages ago.

https://itead.cc/product/sonoff-th-elite-smart-temperature-and-humidity-monitoring-switch/

mcmorrowg

Hi All,

I have an offer of $1,505 DDP for 16 REPT280 grade A. Whats your thoughts?

What DIY battery kit would you recommend as the best option for a newbie?

Im considering one of the seplos ones.

Gavin

graememk

https://www.boards.ie/discussion/comment/121237952#Comment_121237952

Just over €100 per kWh that's a good price.

The seplos one is a good kit, how much for that?

on_the_roots

https://www.boards.ie/discussion/comment/121237952#Comment_121237952

Is this price already including import fees + VAT into IE?

slave1

It's DDP so yes, all fees and taxes the responsibility of seller

mcmorrowg

I havent sourced a seplos kit yet. Something like this but hoping to get a better price.

https://www.fogstar.co.uk/products/seplos-tall-48v-280ah-diy-kit-14-3kwh?variant=41178807140411

With a kit like this do you still need to top balance the cells?

Thanks

mcmorrowg

https://www.boards.ie/discussion/comment/121241594#Comment_121241594

Hi, yes its an all in price. The cells are based in EU and only 3-5 days delivery time.

With DDP the seller pays all the shipping, duties and Vat.

graememk

DPP stands for Delivery Duty Paid if anyone is curious

ddonq1412

There is a lot of varients of the seplos mason box. To get it from china or eu there is not much of a price difference than what fogstar delivers them for. Eel do a version similar that comes with a 4amp active balancer fitted to inside of box for 744 EU warehouse. I'm looking at.

bullit_dodger

https://www.boards.ie/discussion/comment/121242650#Comment_121242650

Interesting - if you pull the trigger on that, let us know how you get on.