"Chargery Power" Inc BMS ? Feedback / Opinion wanted

[Steve_S]

Good Day everyone,

I'm in process of investigating options to replace my FLA Batteries with Lithium. Something I have to do fairly quickly so "the heat is on" you might say. I'm fielding a couple of options at the moment and this brings the question. Does anyone have experience with "Chargery Power" brand BMS ?
REF:
direct: http://chargery.com/BMS8T.asp or

Chargery BMS and Charger - Shop Cheap Chargery BMS and Charger from China Chargery BMS and Charger Suppliers at IC GOGOGO Store on Aliexpress.com

Shopping for Cheap Chargery BMS and Charger at IC GOGOGO Store and more from lipo life,life smart,lipo display on Aliexpress.com ,the Leading Trading Marketplace from China

www.aliexpress.com

I have an opportunity buy 12, Chevy Volt 6S Modules which I can config @ 24VDC fort something around 13kwh or so. This is the BMS suggested by the vendor but I would like to know more.... Is there something better / more flexible at similar price point or any "gotcha's" lurking, waiting to pounce ? There is also the possibility that the battery pack could get expanded later so I don't really want to get locked into a BMS that would limit such.

Ideally, I would love to have a BMS which I can use Modbus or ? to communicate & interact with it using a RaspberryPi, node-red.

What's worse, deciding on battery options !
1) 12, Volt 6S modules (24vdc 13kwh +/-) [$3600 CAD] or
2) 2 Tesla Model S Packs for (24vdc 11kwh +/-) [ $3300 CAD] or
3) New LifePO4 either 16pcs @ 200AH or 8pcs @ 400Ah for 24V 400Ah / ~10kwh [varies but close to above #s]

Geez, makes my Brain Hurt ! and terrifies the wallet !
Thanks in Advance for any help
Steve

 

[Johan]

You can also consider Tiny BMS (also thanks to @electric), as used here on Youtube. Supports 4 to 16 cells. It interfaces with quite a few platforms.

Price comparison example:
Chargery: USD 250 @ ECPC (namebrand blacked out but I think this is Chargery)
Tiny BMS: EUR 200 @ Energus (EUR 159 + some cables)

A remark about the Chargery BMS16T/BMS24T (maybe not important): For balancing, according to the manual, the programmable LFP "balance start voltage" can be chosen between 3.1 and 3.4V, which is too low, and 3.2V as default, which makes no sense as discussed here. In contrast, the latest (4th) generation Daly BMS uses 3.6V. Someone else with Chargery balancing problems here.

[edit] I just stumbled over this comparison of commercially available Li-Ion BMSs:
http://liionbms.com/php/bms_options.php

 

[Steve_S]

You can also consider Tiny BMS, as used here on Youtube. Supports 4 to 16 cells. It interfaces with quite a few platforms.

Price comparison example:
Chargery: USD 250 @ ECPC (namebrand blacked out but I think this is Chargery)
Tiny BMS: EUR 200 @ Energus (EUR 159 + some cables)

A remark about the Chargery BMS16T/BMS24T (maybe not important): For balancing, the programmable LFP "balance start voltage" can be chosen between 3.1 and 3.4V, which is too low, and 3.2V as default, which makes no sense as discussed here. In contrast, the latest (4th) generation Daly BMS uses 3.6V.

[edit] I just stumbled over this comparison of commercially available Li-Ion BMSs:
http://liionbms.com/php/bms_options.php

That's quite a helpful resource indeed ! THANKS A LOT !
I ended up purchasing a ShunBin 24V/400AH pack with built in BMS ~but~ the BMS they supply is fairly limited and may need to be replaced so this is potentially going to be very handy.

 

[electric]

A remark about the Chargery BMS16T/BMS24T (maybe not important): For balancing, according to the manual, the programmable LFP "balance start voltage" can be chosen between 3.1 and 3.4V, which is too low, and 3.2V as default, which makes no sense as discussed here. In contrast, the latest (4th) generation Daly BMS uses 3.6V. Someone else with Chargery balancing problems here.

In theory, as long as you can control the differential threshold for balancing, it doesn't matter at what voltage you start. If you can set dV=30mV for example, then a healthy pack will never start balancing until well above 3.4V average, because dV only starts to grow when first cell(s) approach full charge.
In practice, starting to balance below 3.4V is nonsense, because it's not practical to burn off a lot of energy from many healthy cells, just to allow one weak cell to catch up. If your pack is so much out of balance, then you should consider some sort of maintenance, cell replacement, etc. Normal day to day balancing on a healthy pack should be very minimal if any at all.
Also consider that balancing goes by voltage, which is subject to cell's impedance when under bulk charge current. So, a cell with higher impedance will be at a higher voltage during bulk charge and could trigger unnecessary balancing. The same cell will be at a lower dV compared to other cells at the end of charge when current is reduced.

 

[grizzzman]

In theory, as long as you can control the differential threshold for balancing, it doesn't matter at what voltage you start. If you can set dV=30mV for example, then a healthy pack will never start balancing until well above 3.4V average, because dV only starts to grow when first cell(s) approach full charge.
In practice, starting to balance below 3.4V is nonsense, because it's not practical to burn off a lot of energy from many healthy cells, just to allow one weak cell to catch up. If your pack is so much out of balance, then you should consider some sort of maintenance, cell replacement, etc. Normal day to day balancing on a healthy pack should be very minimal if any at all.
Also consider that balancing goes by voltage, which is subject to cell's impedance when under bulk charge current. So, a cell with higher impedance will be at a higher voltage during bulk charge and could trigger unnecessary balancing. The same cell will be at a lower dV compared to other cells at the end of charge when current is reduced.

Do you feel the same way about active(using coils and or capacitors)balancers? This Tec moves power. (although there is still some loss.)

 

[Johan]

@grizzzman: Related to your question (but maybe not answering it), see also:
White Paper - Dissipative vs. nondissipative balancing (a.k.a.: Passive vs. Active balancing)
(TLDR; check the conclusions at the bottom)

 

[grizzzman]

@grizzzman: Related to your question (but maybe not answering it), see also:
White Paper - Dissipative vs. nondissipative balancing (a.k.a.: Passive vs. Active balancing)
(TLDR; check the conclusions at the bottom)

Thanks, Johan. I have already read it. I have three I'm testing. one has inductors, one capacitive and a mystery potted unit. The mystery unit works well.
Of course, it was the most expensive. I bought it due to its having a on-off circuit. (not tested yet)

 

[electric]

Do you feel the same way about active(using coils and or capacitors)balancers? This Tec moves power. (although there is still some loss.)

For me active balancing seems completely unreasonable. At a high cost and complexity, it is meant to move substantial energy between cells.
But in a healthy battery this is not needed. So, it seems to be a band-aid to a bad situation, not a solution. Solution would be to fix the battery, so it's healthy again, by using high quality cells and replacing ones which need replacement.
The only application where I see a need for active balancing is remote critical power, such as space, remote stations, etc. where cost of preventive maintenance is too high, so this kludge can buy some more time when a cell starts to fail, until battery can be swapped or fixed.

 

[grizzzman]

electric how many millivolts would you say is acceptable between the cells say at 3.6?

 

[electric]

electric how many millivolts would you say is acceptable between the cells say at 3.6?

The idea of top balance is to have all cells fully charged before you have to cut the charge if the highest cell reaches above 3.65V. Assuming fractional C rate of charge and reasonably equal internal resistance among all cells, we can assume that above 3.50V the cell is essentially fully charged. So, if your highest cell is below 3.65V, while your lowest cell is above 3.50V, the pack can be considered reasonably well balanced. That means max dV of 150mV at the end of charge, with 3.65V being a cutoff voltage at the highest cell.

 

[grizzzman]

Thank you electric