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Good Chinese BMS review
#1
A Batrium system was a little too expensive for me, so I decided to use a cheap-ish (42USD) Chinese BMS for my Lithium Ion 18650 14S92P / 160Ah battery.  I've done 3 charge-discharge cycles, and so far I'm very happy with it.

This is it:
https://www.aliexpress.com/item/14S-58-8...4c4d8tRQhp

It has all the basic safety features such as to cut off discharge when:
* any cell goes below the safety voltage
* combined battery voltage below safety voltage
* over current
* over / under temperature
and also cut off charge when:
* any cell goes above the safety voltage
* combined voltage above
* over current
* over / under temperature
and a lot more features listed in the link.

The best part is that all the voltage / current / temperature trigger values can be adjusted using the smartphone app (bluetooth connection) or a PC app (USB).  A bit stupid that some settings can only be modified using the PC app.  The voltage/current sensors can also be calibrated, which fixed my BMS Amps reading being off by almost 2x.

My main concern was the balancing function, as it can only drain at 50mA.  Many cheap BMS start balancing only when a cell has reached 4.2V, but this one has many option on when it should balance.  I'm very happy with my settings of:
balance when { cell voltage >3.8V } and { voltage diff of 0.02V or more } and { battery is being charged }
So far, this has been plenty to keep by packs balanced.  If it should not suffice, I can change it to balance 24/7 instead of only when being charged.


It's also reasonably easy to do some basic troubleshooting of the packs.  The packs were initially all in the 4.08V~4.16V range.  After my first discharge, the BMS reported that packs #7 and #12 had much lower voltages:

Turned out that the fuse wire on 4 cells on pack #7 were not properly soldered, and pack #12 had 2 cells with the same problem.  After fixing those issues and 2 cycles later (ca 20h of charging/balancing in total) all the packs were top balanced to within 0.02V difference.  On discharge:


pack #11 is a little weak, but still within my "good enough" range.

I'm quite happy with this BMS, and I've ordered 3 more to use in my next batteries.
The only thing I'm not too happy about is the limited range of the bluetooth requiring me to be basically in the room to check the status.  Wifi remote monitoring would have been awesome.
Wolf, Alber, Generic like this post
Modular PowerShelf using 3D printed packs.  30kWh and growing.
https://secondlifestorage.com/t-AJW22-s-...PowerShelf
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#2
What criteria does it use to deem the battery to be fully charged ?
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#3
Thanks for the post and update.  I'm interested in this product, but I'm planning on initially creating a 7S20P system and then maybe upgrading to a 14S20P system.  Would this work with that product in a 7S20P system?

Thanks.
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#4
I’m using three of these BMS for my Powerwall build and they work flawlessly. They are available for 7s configurations as well, my largest pack is 7s40p.
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#5
I will go with five of these bms thingies and will interface them with a raspberry
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#6
If I get a 20A version of these, does that mean I can only charge/discharge with 20A ? Or can this be setup to only do balancing and I'll charge/discharge as usual without going through this bms thingy ?
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#7
Is there a 10s as well ?
My needs...
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#8
(03-06-2019, 04:30 PM)Sean Wrote: What criteria does it use to deem the battery to be fully charged ?

Charging is blocked when any cell reaches "Overvoltage" (default 4.2V?, me: 4.15V) OR the overall voltage reaches a set level (default 59.5V?, me: will set to 58.1V; adjustable only through PC app).  Though the terminals are the same, discharge is of course still possible even when charging is blocked.

The "Overvoltage release" specifies the voltage at which charging should be allowed again after it was blocked due to Overvoltage.  Probably best to have it set a little below "Overvoltage" so that the blocking MOSFET and the charger does not cycle on-off too frequently.






(03-06-2019, 05:17 PM)Ebarnett Wrote: Thanks for the post and update.  I'm interested in this product, but I'm planning on initially creating a 7S20P system and then maybe upgrading to a 14S20P system.  Would this work with that product in a 7S20P system?

Thanks.

They have all sorts of versions for different S and max current rating.  But unfortunately, that means you'd have to get a new BMS when you switch to 14S.  Can't just add on parts like with Batrium.

Here you go, 7S:
https://www.aliexpress.com/store/product...574ajjk2mE


(03-06-2019, 07:39 PM)Charly144 Wrote: I will go with five of these bms thingies and will interface them with a raspberry

I'd love to see your code when you get it working!!


(03-06-2019, 08:18 PM)DennisN Wrote: If I get a 20A version of these, does that mean I can only charge/discharge with 20A ? Or can this be setup to only do balancing and I'll charge/discharge as usual without going through this bms thingy ?

Yes, 20A version can handle max 20A drain (and charge, I assume).  You can always set this lower via software (see screenshot above), but not higher due to hardware limitation.  ALWAYS go for one or two levels higher spec than you need, especially with cheap models.  The parts will stay cooler and be more reliable, and you will have some head room to expand.  A no brainer in this case because the cost difference for 30A is just $2.21 !

I think you can use the BMS just for the balancing and charge/discharge the battery directly.  But please please don't?!  As soon as you have one high self discharge cell (or blown cell fuse) that the balancer can't keep up with, you will end up overcharging all other packs and burn down something.



(03-06-2019, 10:28 PM)Cherry67 Wrote: Is there a 10s as well ?
My needs...

Here you go, 10S:
https://www.aliexpress.com/store/product...61e8Vut6Kd
Modular PowerShelf using 3D printed packs.  30kWh and growing.
https://secondlifestorage.com/t-AJW22-s-...PowerShelf
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#9
(03-06-2019, 11:41 PM)ajw22 Wrote:
(03-06-2019, 04:30 PM)Sean Wrote: What criteria does it use to deem the battery to be fully charged ?

Charging is blocked when any cell reaches "Overvoltage" (default 4.2V?, me: 4.15V) OR the overall voltage reaches a set level (default 59.5V? .....

You are aware that just reaching a certain voltage isnt the complete picture in terms of charge completion criteria ?
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#10
Thanks. Looks like I may go either batrium. I want the flex ability to upgrade and not pay for s bums sgsin
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