48V/280A LifePo4 powerwall - BMS recommendation


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duclos_laurent

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Hello to all,

I purchase 16 LifePo4 cells for building a 48V/280A power wall.
I'm now using an hybrid inverter WKS 5kVA/48V and 12 x 300W full black modul.
The 12 solar panel are now on configration : 3S4P due to limitaiotn on the max voltage admissible : 60 - 115VDC so in PV entry : 90VDC/40A
The specification of the hybrid inverter is the following :
- Max charge from AC : 60A
- Max charge from DC solar : 80A

Which kind of BMS (Charge/decharge, common/separate port) can you advise to me?

Thanks to all for your answers.
 

OffGridInTheCity

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For heavy duty - Batrium is a winner for me. I use WM4 with 84 longmons (80kwh battery bank) and have had 2 yrs of good results so far.

For lighter duty.... ($150 range)....
Was going to start a thread, but this one will do. I've been trying to use Chargery 8T, 16T but after 2 failures in 2 days - I'm moving on and interested in responses here.

-----------------------------------------
Unfortunately - I can no longer recommend Chargery...

I recently went with Chargery because I want to see what's happening (voltage per cell) and using a phone app is not OK for me.

* Wednesday- one of 2 Cargery 16T I have on APC 3000(wiredto outside the APC at 75F room temp) became 'overly hot' as intoo hot to hold the blue box. The unit reported4.5v on cell 8 and 1.2v on cell 12 (out of 14s) and instead ofturning off the relay (cutting power from the battery) it went into a cycle where it would turn off the external relay, and then after couple of mins - turn on again and repeat. Research showedno problem with the battery/cells/sense-leadsafterindependent measurement.

* Yesterday - After finding the battery OK and concluding the Chargery unit was the problem, I replaced it with a back up Chargery 16T - which reported all OK. Unfortunately, when I poked the temp sensor into the case the tip brushed against a battery and 'sparked'. *This kill the unit! My bad but the temp sensor appeared to electrically protected? - clearly not good as I do better with units that have a littleprotection against myself :)

1/2 of this is dueto a failed unit and 1/2 to a combination of 'a bit sloppy on my part' + unexpected finicky temp sensor. I can't afford this. Andwhat really bothers me is the failed unit didn't just disconnect thebattery - but rather when into an on/off loop. The whole point of a BMS is to disconnect the battery if the BMS thinks there is a problem - what if there had been an actual problem with the battery?.
-------------------------------------------------
 

duclos_laurent

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Thanks OffGridInTheCity for your reply but my "small" battery can not affrod a Batrium BMS... it is more or less 1/3 of the total price of my battery installation...
Never try or no feedback about Dali BMS or equivalent model sold on chinese market?
 

OffGridInTheCity

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duclos_laurent said:
Thanks OffGridInTheCity for your reply but my "small" battery can not affrod a Batrium BMS... it is more or less 1/3 of the total price of my battery installation...
Never try or no feedback about Dali BMS or equivalent model sold on chinese market?
Do you mean "Daly" - like this? -https://www.aliexpress.com/item/32921429106.html?src=google&src=google&albch=shopping&acnt=494-037-6276&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&&albagn=888888&albcp=9765122064&albag=101238896618&trgt=892975210062&crea=en32921429106&netw=u&device=c&albpg=892975210062&albpd=en32921429106&gclid=EAIaIQobChMI06-ika3m6gIV0RZ9Ch0wEQo6EAQYAiABEgKVy_D_BwE&gclsrc=aw.ds

Don't have any info beyond random youtubes here and there- but Daly doesn't have visuals so its no good for me.I'm sure you'll get some advice on what you'relooking for:)
 

OffGridInTheCity

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Don't mean to hi-jack your thread - but to follow up on Chargery 16T fail described above... just opened it up and you can see 'burnt component'! It just flakes off as you pick at it and is the source of the burning smell.

image_golyil.jpg
 

gauss163

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OffGridInTheCity said:
Don't mean to hi-jack your thread - but to follow up on Chargery 16T fail described above... just opened it up and you can see 'burnt component'! It just flakes off as you pick at it and is the source of the burning smell.

That's not the first time I've heard ofproblems with Chargery BMS/chargers, e.g. below fromEndlessSphere

ElectricGod said:
I can't in good faith recommend that anyone buy this balance charger (Chargery C4012B). I wouldn't buy one and I've had 3 of them. I'm really disappointed in this charger!!! It is dangerous and can't be trusted [...]

It lasted less than an hour before it shut down for no apparent reason. I pulled the power chord, let it sit a while and plugged it back in. Everything seemed fine so I proceeded to test at 12S again...same thing...shut down in the middle of a charge, but now it wouldn't power up again. OK...time to take it apart and see what happened. I found that a heat sink with a single transistor on it got so hot that it melted the wires that were touching it. This created a short between the balancing board and the transistor and pitted the heat sink. That was the end of the beta version charger. I sent it back with the expectation of what I found receiving some form of correction. In a later version of the charger, I opened it up and found that the "solution" was a piece of kapton tape stuck over the heat sink. Really? Don't fix the over heating problem, just throw a band-aide on it. Well that was disappointing! This was the first hint I had that these chargers are garbage

Designing and testing Li-ion BMS & chargersrequires a largeamount of expertise and resources - which are often lacking in very small companies like Chargery. Thecompany is reportedlya one-man show according to comments there, viz. "Chargery is a small company and had initial problems bringing both products to market early.Being a one man show means Jason is responsive to requests for small change". When it comes to matters of safety, do you really wish to trust a "one man show"?




Re: bargain-basement vs. reputableBMS. Likely many readers are not aware of the immenseeffort involved in thedesign of a top-tier BMS, e.g.those used in laptop battery packs. The safety standards used in designing such packs are extremely comprehensive, using industry standard methods of risk analysis such as FTA (fault-tree analysis),FMEA (failure mode and effects analysis), etc. The design typicallyincorporatesmultiple levels of failsafe redundancy. For example, the safety standards employed for laptop batteries consider hundreds of possible cases, even the case that a pet urinates on a PC, e.g. below from the IEEE 1625 Standard forRechargeable Batteries for Portable Computing

image_nqsmws.jpg

For example, to protect against overcharge there are at least two independent circuits monitoring each cell's voltage. Each IC has the capability to turn off the charge MOSFET and, if that fails (e.g. FET failed short), they can then blow a special type of fuse (chemical / 3-terminal) to disconnect the cells. Such fuses require only a small voltage on a 3rd terminal to trigger a disconnect. Because it requires only a small voltage to blow, it can function even when the battery voltage has dropped very low (e.g. due to a short-circuit). Analogous redundancy exists for other protection mechanisms (overcurrent, overtemperature, etc).

The probability of safety failure of a laptop battery is greatly reduced due to these multiple levels of redundant protection. By contrast, there is significantly less protection provided by protected cells and standalone chargers. Protected cells can fail simply from static shock (ESD), mechanical shock (drops), etc. Indeed, there are many reports on CPF and BLF of failed protection circuits on cells. Standalone chargers typically have little if anyredundantprotection, and are not designed to meet any reputable international standards

There is little chance that a small company has the expertise and resources in-house to reach similar levels of safety. So be careful with bargain-basement solutions.
 

duclos_laurent

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@OffGridInTheCity,

According to your experience and power storage capacity, do you have some trouble or power pack misfuncton due to temperature too high?
My concern is that I will implement my cells inside the swimming pool house (5m = 50sqft) on which during summer, the swimmng pool pump heat the swiming pool house and i feear that temperature will go over 45C.
Do you have a system to cool down your batery or maybe to warm up if temperature is below 0C?
 

gauss163

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^^^ Higher temperatures greatly accelerate degradion. If you can't reduce temps then to help offset such you should considerchargingto less than 100% SOC inorder to help prolong life. For example, see the graphs below and note how much faster the cells degrade (lose capacity and IR increases) while aging at very high SOC.See here for furtherdiscussion and links


image_miqjtg.jpg

Also, be careful that the entire pack is kept at uniform temperature, else you may suffer from the same problem many laptop packs did - that some part of the pack is heated more than othersso it degrades more quickly than others (why you often find both good and bad cells when harvesting used laptop packs), e.g. see the thermal image below.

image_wezmot.jpg

Image excerpted fromBattery Monitoring Basics - TI training, by Texas Instruments.
 

OffGridInTheCity

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duclos_laurent said:
@OffGridInTheCity,

According to your experience and power storage capacity, do you have some trouble or power pack misfuncton due to temperature too high?
My concern is that I will implement my cells inside the swimming pool house (5m = 50sqft) on which during summer, the swimmng pool pump heat the swiming pool house and i feear that temperature will go over 45C.
Do you have a system to cool down your batery or maybe to warm up if temperature is below 0C?
My batteries are all under or in the house with a temp range of55F - 75F. Yes - 45C+ (115F+) is pretty warm and while that might be 'within max specs' of your cellsI would make effort to cool things down to 80F.Even 90F is better than 115F.

At least a fan and measure the temps to see what's actually happening.

OR

Perpahs a cheap ($250) AC like this -https://www.amazon.com/dp/B07RDM6RBZ/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=vehicledwelling-20&linkId=bbd877674f88573bfd89455184121223&language=en_US
Here's a youtuber @DIY Solar Power with Will Prowse with a set of youtubes on this AC in his shed in Nevada (sunny/warm)... only 1.5kwh / day if I remember correctly
Part 1: [color=var(--yt-endpoint-visited-color, var(--yt-spec-call-to-action))]https://youtu.be/2Qh14pX3IxA[/color]
Part 2:
[color=var(--yt-endpoint-visited-color, var(--yt-spec-call-to-action))]https://youtu.be/kclLbSPtI7E[/color]
Part 3:
 

duclos_laurent

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Thanks OffGridInTheCity and gauss163 for your advice.
Yes I plan to let a little space between each cell and put 2 or 3 computer fan to cool down the pack, take air from outside (I have to make a hole inside the wall) and extract the warm air from inside the box on which I will put the battery cells.
All will be managed according to temperature sensor inside the box and fans will be start/stop automatically.
Air conditioner will be the last solution if the temperature goes too high.
Limit the SOC is also planned, maybe not to go higher than 75%

And what about the minus temperature, in our region the minimum temperature can reach minus -10C but I think that internal cell temp can prevent from freezing
 

OffGridInTheCity

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duclos_laurent said:
And what about the minus temperature, in our region the minimum temperature can reach minus -10C but I think that internal cell temp can prevent from freezing
Typically - you must not charge below 0C (32F) else you'll do damage - the greater the charge the greater/faster the damage. There is such as a thing as some 'special' LifePo4(s) that go a bit lower but I'm guessing you don't have those - but of course you should look up the specs for your cells.

Its a curve down to 0C rather than a sharp drop-off. This graphic gives a visual-https://www.researchgate.net/figure...mperature-of-Li-ion-battery-26_fig3_327966044

You should be able to easily find aBMS with low temp cutt-off to help you protect the battery bank.
 

duclos_laurent

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Charly144

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Be aware with this bms. Max charging Rate is 50Amp, even wehren discharge is 300 Amp!
 

camthecam

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I thought if you had a Multiplus or other regulated charger inverter, you wouldn't need a BMS. If its fused/Breaker and monitored by charger settings (short absorption) then all you need is a balancer which you could do manually every couple of weeks.
Just causing trouble and baiting Gauss....
 

Charly144

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You need something that controls voltage on cell level. Multiplus doesnt care about that, it just stops charging at the set voltage...
 

Redpacket

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duclos_laurent said:
Thanks OffGridInTheCity and gauss163 for your advice.
Yes I plan to let a little space between each cell and put 2 or 3 computer fan to cool down the pack, take air from outside (I have to make a hole inside the wall) and extract the warm air from inside the box on which I will put the battery cells.
All will be managed according to temperature sensor inside the box and fans will be start/stop automatically.
Air conditioner will be the last solution if the temperature goes too high.
Limit the SOC is also planned, maybe not to go higher than 75%

And what about the minus temperature, in our region the minimum temperature can reach minus -10C but I think that internal cell temp can prevent from freezing

Outside air can bring humidity & lead to cell corrosion problems.
My large LiFePo4 packs don't seem to dissipate noticeable heat on charge or discharge. They are in metal battery box cases &l I have a DS18b20 temp probe in there.
I log battery + outside temps 24/7 - the cells slowly follow (lag behind) outside temps vs anything to do with charge or discharge.
Temps here are typically 5C to 35C with occasional hot days 45 ish. The cells have always been inside this range.


Now the inverter & 3x MPPT chargers, yes, they get warm & need some fans....
Some graphs:
image_xhclxk.jpg
 

not2bme

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duclos_laurent said:
Thanks OffGridInTheCity and gauss163 for your advice.
Yes I plan to let a little space between each cell and put 2 or 3 computer fan to cool down the pack, take air from outside (I have to make a hole inside the wall) and extract the warm air from inside the box on which I will put the battery cells.
All will be managed according to temperature sensor inside the box and fans will be start/stop automatically.
Air conditioner will be the last solution if the temperature goes too high.
Limit the SOC is also planned, maybe not to go higher than 75%

And what about the minus temperature, in our region the minimum temperature can reach minus -10C but I think that internal cell temp can prevent from freezing

You do what you have to do to keep the batteries cool but ambient is fine unless you live in the desert where your average temp is 40C. Hbpowerwall goes over 40C in his shed over the hot australian summers. Tesla powerwalls have been installed outside as well. Is it optimal? No but nothing in this world is optimal. Having it inside the house is optimal but increased risk to safety. A few hot summer days will not kill your batteries. The key is to install it at a location where it's shaded and not exposed to direct sun. My shed is located under a shade and the box is insulated. The temp inside is only slightly higher than outside temps. Humidity is not a concern unless you live in the swamp it's probably within working parameters. My shed contains the inverters as well so the heat generated dehumidifies the shed at night when the fan isn't running as much. During winters it must not drop below 10C. Batteries must never get below 0C. Heat generated from my inverters work well to keep it within these parameters. You lose capacity if you are running at lower temps but it's easier to add heat during winters with spaceheaters, etc.
 

duclos_laurent

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Thanks Redpacket for the feedback about the temperature evolution on the battery pack. I also monitor the temperature inside the pool house where the battery pack will be installed and max teperature till now was 42C. So I think there will have no risk for the pack.
@ Not2bme, you are right, nothing in the world is optimal and battery pack can support some hot days. For the moment, I will not take care of hot days but maybe more on cold days, and as you said, it is more easy to warm the room than to cool down.
 

duclos_laurent

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@not2bme & @Redpacket,
Just to give an update about my installation, I change a lot of things and now no more problem about hot/cold temperature inside my swimming pool house.
Hybrid inverter have been removed and replaced by 3 micro-inverter.
Charger is now a Victron Multiplus 2 48/3000, cells balancing is made by a 48V/300A BMS and monitoring by BMV-700.
Storage capacity is 48V/280A mdae with 16 Lifepo4 cells coming from Alibaba seller.
All have been wired and tested, installed inside my house cellar, no more issue on with temperature and humidity as it is under earth with constant temperature and humidity...


image_suepkw.jpg



image_jrcqha.jpg


Thanks to both for your advices
 
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