Choices for 4S ~250A-300A BMS with temp sensor?

[Mako74]

Hi all. I've been trying to get my head over the whole solar + LifePO4 thing as I'm about to start rebuilding my camper van.

I've binged on Will's YT videos, which are really fun to watch, and I think I'm ready to try the DIY route with 4 pcs of 12V 200Ah or 280Ah from Ali B.

But, I haven't yet found a suitable BMS that could handle a 1800W flow (3000W peak) through the inverter AND has a low temp cut-off (it gets cold up here on the 60° N Lat).

Sorry if the answer is close, but I just couldn't find anything definite while searching the forum.

So any good tips on the BMS?

Thanks!

 

[Samsonite801]

In my case, I had 2 ways of solving this. On my 12v RV system I'm building, I just went with 8 cells instead (ouch), so I could just buy 2x OverKill 120a 4s BMS, and keep them as separate 4s banks in 2P, then that gets me the 240a, with known tested and good low-temp cutoff.

Now obviously that is twice as expensive, perhaps why you are only trying to use 4x cells (or may be space related), I understand potential budget constraints, no worries. However, if you did have it in budget or within space constraint, the 8x does give double the runtime, and bank redundancy.

So on my other 48v system I'm building, the issue is that the 2x 200a 16s BMS that were included with those battery systems, they do not have low temperature cutoff (didn't learn that until after the fact). So I decided to get a Victron MPPT charge controller, with a Battery Sense monitor w/ temp probe (or you can alternatively use their BMV monitors w/ temp probe, or the Smart Shunt monitors w/ temp probe), and the Victron will be the one monitoring for low temp and do the charge cutoff at desired temp.

Other note, I did read today somewhere here, that maybe some of the newest Daly BMS may support low temp cutoff (find someone who tested it and confirms it works): https://diysolarforum.com/threads/daly-high-current-question.13558/#post-161850
(keep in mind this guy who said it works is using a 100a one)

Chargery low temp cutoff might work too (not sure the amps ratings or if they have 4s ones)..

Chargery BMS now with Low Temp Cutoff

Good Day Folks ! Note: I have no affiliation with Chargery whatsoever, I'm just a customer sharing info in the best interest to help others. I purchased a Chargery BMS8T a month or so ago as a replacement BMS for my ShunBin pack. Post showing installation on ShunBin Pack The installation has...

diysolarforum.com

Or keep searching on AliExpress and see if you can find a high amp BMS where the seller says low temp cutoff works (although still not tested, and cross fingers).. Also, even if they say the low temp cutoff works, is it user-configurable setting? Like doe it have Bluetooth and is a managed BMS? My OverKill BMS are managed so there is a user setting to change the temp. On my other BMS's, even if it were to have a working low temp cutoff say, that BMS is not manageable, so the parameter would be hard set and locked into whatever the manufacturer thought was a safe charging temperature...

According to the videos I've seen from Will, there are several instances where he would test BMS where they were advertised as working low temp cutoff, then he would test the feature and it wouldn't actually work. So in my case, that is why I opted for the OverKill one, because Will endorses them and tested that they do work, and this is a keystone point about OverKill BMS's. With other vendors it can be hit/miss, so you almost have to find someone who tested it and says it works for sure, then get the same model number yourself, otherwise it may be a gamble.

But again, the other option is to just let the charge controller handle it, if it offers the option, and with Victron, it requires the external temperature probe to get realtime temp monitoring, as the internal temp probe in the Victron only takes a reading once a day or something like that.

 

[drwormy]

Other note, I did read today somewhere here, that maybe some of the newest Daly BMS may support low temp cutoff (find someone who tested it and confirms it works): https://diysolarforum.com/threads/daly-high-current-question.13558/#post-161850
(keep in mind this guy who said it works is using a 100a one)

Several resellers / custom battery builders in Australia are using the Daly 250A smartBMS, and low (and high) temperature disconnect has been tested by them and works fine. I have the 60A version and low and high temp cutoff was the first thing i checked.

eg.

CALB 12V 326Ah Lithium Battery & 250A Daly Smart BMS

CALB 12V 326Ah Lithium Battery & 250A Daly Smart BMS - Assembled in Australia 300Ah

www.solar4rvs.com.au

and

 

[Mako74]

Thanks guys, appreciate your time answering!

@Samsonite801, you're correct on both the space and the budget, but I think I could be flexible. What size and type cells do you have in your 12V system? I was looking into the cheapest 280Ah Prismatic cells from Xuba etc., but after reading about the aluminum cases expanding in charging and how they last in off-road van use I'm a bit anxious and am now thinking about whether I should go for the 200Ah CALB cells instead and lose some total Ah. And the whole Victron temp probing possibility is not making this any easier!

I'll keep reading and studying and asking questions as I still have 1-2 months to decide on the system and place the orders from Ali.

 

[Samsonite801]

Thanks guys, appreciate your time answering!

@Samsonite801, you're correct on both the space and the budget, but I think I could be flexible. What size and type cells do you have in your 12V system? I was looking into the cheapest 280Ah Prismatic cells from Xuba etc., but after reading about the aluminum cases expanding in charging and how they last in off-road van use I'm a bit anxious and am now thinking about whether I should go for the 200Ah CALB cells instead and lose some total Ah. And the whole Victron temp probing possibility is not making this any easier!

I'll keep reading and studying and asking questions as I still have 1-2 months to decide on the system and place the orders from Ali.

Sounds great, the daily exposure to the forum, it all starts coming together after awhile hehe

My cells are the standard 280ah cells (look same like EVE, although I do not know if mine are EVE or not)... These are the ones I bought for the 12v system:

1179.9US $ 5% OFF|8pcs/lot Lifepo4 3.2v 280ah Lithium Iron Phosphate Cells For 24v 280ah Rv Battery With Bus Bars - Rechargeable Batteries - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

On a vehicle application where there is higher potential for shock/vibration, and larger temperature swings, I would definitely clamp the cells. That is a 'hole nother' rathole of information in threads here about that, but the bottom line is, clamp the batteries (with some plates and threaded rods) with some pressure to keep them tight (fixed as a single assembly) so the sides of the cells will stay flat and not bulge in time, but the other advantage to clamping, is the batteries won't move or wiggle around in relation to each other (bad for rigid bus bar connections), and if possible I would also recommend flexible, or non-rigid bus bars, so if there is any small movement, it doesn't put all the tensile stress on the battery terminals/bolts/bars.

I'd be fine using EVE 280ah in an RV, plenty here have done it, just try to think like the vehicle, working to wiggle and destroy and vibrate everything to pieces, just engineer it well, so it will stand the test of time as much as reasonably possible. Possibly install a heat pad under an aluminum plate the batteries sit on (with a thermostat switch), if the low temps may be a concern...

I am building my aluminum plate cell clamp assembly right now, and it includes a bottom plate to stick a heat pad onto. Building 3, two for my 16x cell 48v banks, and a smaller one for my 8x cell 12v banks. That clamp will be for 2x cells wide, and 4x cell deep, and mount 2x BMS's on the front of it, inspired by this design (except my plate is 2x wide, to house both banks in same clamp):


THESE ARE NOT MY PICS, I AM ONLY USING THIS DESIGN AS INSPIRATION FOR MY PROJECT:

 

[Mako74]

Sounds great, the daily exposure to the forum, it all starts coming together after awhile hehe

My cells are the standard 280ah cells (look same like EVE, although I do not know if mine are EVE or not)... These are the ones I bought for the 12v system:

1179.9US $ 5% OFF|8pcs/lot Lifepo4 3.2v 280ah Lithium Iron Phosphate Cells For 24v 280ah Rv Battery With Bus Bars - Rechargeable Batteries - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

On a vehicle application where there is higher potential for shock/vibration, and larger temperature swings, I would definitely clamp the cells. That is a 'hole nother' rathole of information in threads here about that, but the bottom line is, clamp the batteries (with some plates and threaded rods) with some pressure to keep them tight (fixed as a single assembly) so the sides of the cells will stay flat and not bulge in time, but the other advantage to clamping, is the batteries won't move or wiggle around in relation to each other (bad for rigid bus bar connections), and if possible I would also recommend flexible, or non-rigid bus bars, so if there is any small movement, it doesn't put all the tensile stress on the battery terminals/bolts/bars.

I'd be fine using EVE 280ah in an RV, plenty here have done it, just try to think like the vehicle, working to wiggle and destroy and vibrate everything to pieces, just engineer it well, so it will stand the test of time as much as reasonably possible. Possibly install a heat pad under an aluminum plate the batteries sit on (with a thermostat switch), if the low temps may be a concern...

I am building my aluminum plate cell clamp assembly right now, and it includes a bottom plate to stick a heat pad onto. Building 3, two for my 16x cell 48v banks, and a smaller one for my 8x cell 12v banks. That clamp will be for 2x cells wide, and 4x cell deep, and mount 2x BMS's on the front of it, inspired by this design (except my plate is 2x wide, to house both banks in same clamp):

Thanks again @Samsonite801 ! I actually just read about the clamping and all the different spring rates and PSI and what not and almost started crying. This is really not an issue as I'm pretty sure I can bolt these cells together and build a sturdy cage around the pack and fix them in my van so that they don't move around.

You mentioned cold weather. I've also been reading about the heating pads and thermostats (those threads made me cry as well), as I live in a country where we have below zero degrees Celcius 4-5 months of the year. Normally during these months we don't have sun, but there are days in February/March when the sun is out so cold temperature cut-off is essential and battery heating would be nice to have.

I'm actually tempted to go ahead and grab that Singles Day deal on a 4 pcs 280Ah pack from the same vendor you bought yours, as it seems to have good feedback, and get that 120A BMS with low temp sensor and cut-off, or even this Heltec 200A, but I'm not sure if it has low temp cut-off or just the high temp. This could get me started and I could always add another 4pcs of 280Ah later.

There are so many threads going on these topics that's it pretty hard to paint a clear picture. I'd be happy to follow your project as you are doing already the stuff I'm just starting to plan.

 

[Samsonite801]

Thanks again @Samsonite801 ! I actually just read about the clamping and all the different spring rates and PSI and what not and almost started crying. This is really not an issue as I'm pretty sure I can bolt these cells together and build a sturdy cage around the pack and fix them in my van so that they don't move around.

You mentioned cold weather. I've also been reading about the heating pads and thermostats (those threads made me cry as well), as I live in a country where we have below zero degrees Celcius 4-5 months of the year. Normally during these months we don't have sun, but there are days in February/March when the sun is out so cold temperature cut-off is essential and battery heating would be nice to have.

I'm actually tempted to go ahead and grab that Singles Day deal on a 4 pcs 280Ah pack from the same vendor you bought yours, as it seems to have good feedback, and get that 120A BMS with low temp sensor and cut-off, or even this Heltec 200A, but I'm not sure if it has low temp cut-off or just the high temp. This could get me started and I could always add another 4pcs of 280Ah later.

There are so many threads going on these topics that's it pretty hard to paint a clear picture. I'd be happy to follow your project as you are doing already the stuff I'm just starting to plan.

Yeah, I'm not gonna bother with springs, just a static clamp hehe, I don't care that much if my batteries last 5 million years or not, since Lithium Air batteries or something else is likely to hit the market well before then. I only ask myself, what practical steps I can take within logic and reason to help prolong battery life, but at the end of the day I just don't get too worried about it. It's nice to see all that talk though, from the 'granular blueprinters', because it helps one to see the entire spectrum of possibility. When I was younger I used to care a lot more about details and trying to make everything perfect (getting hung up on projects for way too long), but in the ladder years, I learned that perfection as a human is actually to find the best balance of imperfection, because there is no limit to how perfect you want to get with a given thing. Even the richest people in the world armed with the finest teams of support personnel, attempt to build the most perfect things, and find that it's an endless rathole, and it still has flaws in design/execution hehe...

On the batteries, yeah that's why I went with that seller was because they had some good sounding reviews...

And don't worry, it is hard to paint a clear picture when learning new topics, but it will get clear enough, soon enough, just keep on the learning curve for a bit and it will soon be 20/20...

Yeah, and I'm sure I will post my pictures and questions I may have as I build out my power solutions more, stay tuned I suppose, we'll see what I come up with

 

[Terrapin]

Yeah, I'm not gonna bother with springs, just a static clamp hehe, I don't care that much if my batteries last 5 million years or not, since Lithium Air batteries or something else is likely to hit the market well before then. I only ask myself, what practical steps I can take within logic and reason to help prolong battery life, but at the end of the day I just don't get too worried about it. It's nice to see all that talk though, from the 'granular blueprinters', because it helps one to see the entire spectrum of possibility. When I was younger I used to care a lot more about details and trying to make everything perfect (getting hung up on projects for way too long), but in the ladder years, I learned that perfection as a human is actually to find the best balance of imperfection, because there is no limit to how perfect you want to get with a given thing. Even the richest people in the world armed with the finest teams of support personnel, attempt to build the most perfect things, and find that it's an endless rathole, and it still has flaws in design/execution hehe...

On the batteries, yeah that's why I went with that seller was because they had some good sounding reviews...

And don't worry, it is hard to paint a clear picture when learning new topics, but it will get clear enough, soon enough, just keep on the learning curve for a bit and it will soon be 20/20...

Yeah, and I'm sure I will post my pictures and questions I may have as I build out my power solutions more, stay tuned I suppose, we'll see what I come up with

I seem to be about 4-5 months behind this crews voyage through this stuff, I have been posting questions on work arounds on the 120a limitations of the Overkill 4S BMI. Things like hybrid LA with the LFP to get over startup loads on the cheep......Soooooo close to my max short use load needs on a 1500w inverter it "made me cry". Now it seems I am rounding the corner to two separate 100ah DIY batteries in parallel in place of the single 240ah with the one Overkill 120a one... Gonna keep listening.

...but I like the "do your best" attitude of your comments about the battery builds.

And Dog bless the regulars here who chime in and walk each new revolution through the same paces as available tech changes. (Snoobler your are the man, TY.)

..."lithium-air" LMAO

 

[HRTKD]

Yeah, I'm not gonna bother with springs, just a static clamp hehe, I don't care that much if my batteries last 5 million years or not, since Lithium Air batteries or something else is likely to hit the market well before then. I only ask myself, what practical steps I can take within logic and reason to help prolong battery life, but at the end of the day I just don't get too worried about it. It's nice to see all that talk though, from the 'granular blueprinters', because it helps one to see the entire spectrum of possibility. When I was younger I used to care a lot more about details and trying to make everything perfect (getting hung up on projects for way too long), but in the ladder years, I learned that perfection as a human is actually to find the best balance of imperfection, because there is no limit to how perfect you want to get with a given thing. Even the richest people in the world armed with the finest teams of support personnel, attempt to build the most perfect things, and find that it's an endless rathole, and it still has flaws in design/execution hehe...

You and I are on the same wavelength here. I would rather be camping that fiddling around or researching, trying to get to that 100% right solution.

There are so many rabbit holes around here, someone is going to break an ankle.

 

[DonPhillipe]

Just starting my exact same project with a similar setup, the dual 4x12vX280A and building two parallel systems of these for redundancy in my own camper. I actually don't know where to listen or who to believe (sellers have a vested interest and buyers don't have the budget to smoke test or study long term effects due to info too slow to gather, plus many seem only reciting mfg spec-sheets and many are repeating marketing) - if all these are eliminated then sources with long term experience dwindle down to a few. Therefore I have to say that lithium tech is one of the craziest yet

@Samsonite801 I love your setup, and sad to say I had actually to mount mine on a styrofoam pad and duct tape so a strong peer pressure project you've inspired me for. How are you coming along so far?

Also speaking of who/where to info-source, Will P at the time I ordered last year (sitting on the parts since then) suggested the 250A Dali without the BMS while saying it was more reliable than the "smart" version. Hope that wasn't a $200 mistake.

 

[Samsonite801]

@Samsonite801 I love your setup, and sad to say I had actually to mount mine on a styrofoam pad and duct tape so a strong peer pressure project you've inspired me for. How are you coming along so far?

Thanks bud... Mine is coming along little by little. Starting to get into installation of the 12v battery pack I built for the motorhome, except last week I had to help a guy move out of a storage unit which took all week and slowed me down on the ranch project. Next weekend I'll run out and hammer on it some more, maybe take some pictures as I go. Starting to build a simple wooden frame to hold the first 4 solar panels for the 12v system.