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Finding "good" BMS boards
#1
Tried this at the end of my last thread, but either it wasn't getting seen there or no one has answers.  Thought I'd try a new post to be sure...

Anyone have suggestions on sourcing parts, particularly BMS's? Research suggests that many available BMSs ... suck. (That could be literal if they are draining the pack, LOL).

But I am not finding a whole lot of reviews, testing, etc, so its hard to know what one is getting.

I am aware that the term "BMS" is overused, and I know that I have to be sure the unit is meant to do all of the things I need, but how do we know if a unit is quality??

Thanks!

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#2
I'm with you.  I've always been suspicious of a 'unit like this' that you can't see what's going on.   But its also a question of the type of battery.    For my DIY powerwall - I use Batrium and it has good visual/data so you can test and see what's happening - but its a heavy-weight and not practical for an ebike.  

For me smaller batteries in my APC UPSs I've settled on Chargery  'T' models ($120-$180 for 14s) as you can see what's happening.   But even at $180 (compared to Batrium) its a lot of $ for an ebike or skateboard battery.

A 3rd option is no BMS but use a balanced RC charger.  I use this for a portable power pack where I replaced the lead acid with my own 18650 3s...  as the RC charger shows what's going on.   I don't use it much and at 3s it cuts-out (low battery cut-off) before getting to the low end danger zone of the cells.

I know some have created test rigs - and simply test any (no visual indicator) BMSs before putting them in use.  But of course you don't know if they're still good a year later without test. 

There are many scenarios and I'm curious to see what others have determined.   
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#3
(07-08-2020, 08:30 PM)OffGridInTheCity Wrote: I'm with you.  I've always been suspicious of a 'unit like this' that you can't see what's going on.   But its also a question of the type of battery.   

This is a smaller (than powerwall) 24V (72) always-available backup battery.  Pretty low current needs .... under 10A easily, probably under 5.  But based on another thread I am going to overbuild it (capacity wise) and keep it charged in the 75%-ish SOC area.

Since my plan isn't to charge / discharge on an as needed basis, I don't think I can forego a BMS. 

I've seen a few smart BMS units that might be interesting .... but no reviews.
Here's an example:  https://www.aliexpress.com/item/4001218262806.html?spm=a2g0o.productlist.0.0.38a8346cMicorv&algo_pvid=991427e5-2746-4ccf-8152-7739611f3ad4&algo_expid=991427e5-2746-4ccf-8152-7739611f3ad4-3&btsid=0ab6f83115942409448576954e8f3f&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
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#4
(07-08-2020, 09:12 PM)khauser Wrote:
(07-08-2020, 08:30 PM)OffGridInTheCity Wrote: I'm with you.  I've always been suspicious of a 'unit like this' that you can't see what's going on.   But its also a question of the type of battery.   

This is a smaller (than powerwall) 24V (72) always-available backup battery.  Pretty low current needs .... under 10A easily, probably under 5.  But based on another thread I am going to overbuild it (capacity wise) and keep it charged in the 75%-ish SOC area.

Since my plan isn't to charge / discharge on an as needed basis, I don't think I can forego a BMS. 

I've seen a few smart BMS units that might be interesting .... but no reviews.
Here's an example:  https://www.aliexpress.com/item/4001218262806.html?spm=a2g0o.productlist.0.0.38a8346cMicorv&algo_pvid=991427e5-2746-4ccf-8152-7739611f3ad4&algo_expid=991427e5-2746-4ccf-8152-7739611f3ad4-3&btsid=0ab6f83115942409448576954e8f3f&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
Agree you need a BMS - didn't mean to imply you don't.
Agree that I've not seen reviews on the above  but personally I like that it shows data...  price is good... and you can check on the state of the cells to see if they are over/under/out-of-balance Smile

I ordered this one - https://www.ebay.com/itm/312721653175 + a  case for the LCD - but haven't tried it yet as I found Chargery https://www.ebay.com/itm/193543710606 a bit easier to setup for my purposes.
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#5
Thanks again
Unfortunately the display for the one i linked is not available in a 7s unit.
Well, at least I'm in good company trying to figure this all out.
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#6
Smart Bluetooth APP W/ LCD display 7S ~ 20S Lifepo4 li-ion Lipo Battery Protection Board BMS 400A 300A 100A 80A
https://www.aliexpress.com/item/33035076...34bfjikCoO
 later floyd
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#7
(07-09-2020, 02:58 AM)floydR Wrote: Smart Bluetooth APP W/ LCD display 7S ~ 20S Lifepo4 li-ion Lipo Battery Protection Board BMS 400A 300A 100A 80A
https://www.aliexpress.com/item/33035076...34bfjikCoO
 later floyd
Thanks Floyd!
Don't suppose you've tried one of these?
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