# Question about balancing 26S/3P, 60 Ah A123 Brand 5KW modules



## BVH (Jul 4, 2014)

I have acquired 4 of these 5KW, 26S3P/60 Amp Hour A123 Prismatic modules and plan to use them for my whole house backup system I will build. Each module has 2, 13S BMS "slaves" that probably reported to a master BMS controller. I’m not very knowledgeable in BMS’s but generally understand what they do. A member of a different forum tested one of the packs and slaves to see if it would passively balance by charging one individual cell of the 13 cells to 3.6 and observing with a Watt meter in the balance line. All other cells were resting at 3.3 Volts. It appears it is not functioning at all without the master. Are there 13 or preferable 26 cell capable, BMS's (systems) available that I could retrofit? Bluetooth would be nice. I really just need balancing but the other features are fine. I’m open to any solution. I’ll most likely be charging the packs individually with a Cycle Satiator, (no balancing capability) High Voltage version at a max of about 4.5 Amps. I know it’s slow but I have lots of time.

https://www.ebay.com/itm/A123-modul...icle-New-batteries-Less-100-KWh-/153713692059


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## BVH (Jul 4, 2014)

Open to any and all suggestions. Don't want to have to manually balance 8 half-packs separately.


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## brooks (Aug 2, 2019)

Working on the same thing. These boards are blank and I'm trying to locate the software to flash them.


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## BVH (Jul 4, 2014)

Glad to have another person working on it. I hope you are successful. If you'll be needing an inverter and transfer switch, I found a couple that are integrated into one unit and react as fast a computer UPS - 8 ms so there is no momentary loss of power as with many systems using separate components. One is 6800 Watts continuous, the other 8000 Watts continuous. Both have pretty generous surge capabilities. They are for on or off grid applications and meet recent CA and Hawaii utility rules and also connect to a generator if you'll have one in the system.


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## TimHug (Jun 24, 2020)

I am interested in getting more info on these modules too as I also bought from ebay. 

Which Forum did you see the info on the 13S sub module bms's? 



From various forums it seems the balancer circuitry ,at least in old versions of A123's BMS boards can balance up to 300mA and it maybe the balancer needs to be turned on during charging via a CAN bus message. This makes sense in that the balancer then has no parasitic drain in long term battery storage/standby but it makes it harder to use without setting up CAN controller. Apparently the can interface connector has an enable line and some error alert lines over and above normal comm intfc lines.
T


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## frodus (Apr 12, 2008)

Is there someone that wants to work on building a BMS master for these? I may have access to some of the CAN protocol information for the slaves, but someone else needs to do the work. I'm interested in potentially funding the work if a board/software was created.


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## BVH (Jul 4, 2014)

There's not much usable info here but here's the start of the topic in a thread


https://www.rcgroups.com/forums/showpost.php?p=44718841&postcount=15




I cancelled my order of 6 modules for use as an inverter feed for a whole house backup system. Both the 26S and 13S (electrically splitting the pack) Voltage is just too low for all the major inverter players 48 Volt and 96 Volt input units.


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## PaperCut (Jun 10, 2020)

You could use two of these bluetooth active balancers (they daisy-chain). I use them for my Li-Ion packs and it has a decent bluetooth interface.
https://www.ebay.com/itm/CAN-Bus-RS...zer-Balance-Bluetooth-2S-24S-BMS/264662290391


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## TimHug (Jun 24, 2020)

The ANT BMS is a possible an option. 
It is blue tooth controlled and is available in a version with up to 32S so easily handles 26S in this pack. I believe there is an optional RS232 plug in interface but I have not seen it on ebay. Balance current is up to 200mA. 

The A123 packs have 2 balance connectors built in, one at each end which are connected to two A123 Battery management units of 13S each. These units rely on operation using a daisy chained CAN bus interface which can connect multiple A123 modules together for seamless control of a larger effective pack. The messaging / control would take some effort to setup and without an operating controller there is no balance function and the boards hibernate.

By removing the A123 BMS boards you could connect the ANT unit directly to the two 13S JST balance connectors and you would also need to add power cables to incorporate the over current/overvoltage protection offered by the ANT BMS. The A123 bms does not include over voltage or short circuit protection. ( The pack only has internal fusible links between each cell.)

Prices for ANT BMS vary, depending on if you get a unit with the higher current protection FETs or LCD display . Available in 70 to 300A versions although aparently you need to derate the current by maybe a factor of 2 for continuous use. $106 - $155. The ANT units have other features like temperature sensors you can embed in pack and does coulomb counting etc.
example of one seller:








8S-32S Battery BMS protection Board Bluetooth APP Lifepo4 Lipo Lithium LTO DIY | eBay


Find many great new & used options and get the best deals for 8S-32S Battery BMS protection Board Bluetooth APP Lifepo4 Lipo Lithium LTO DIY at the best online prices at eBay! Free shipping for many products!



www.ebay.com


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## BVH (Jul 4, 2014)

Thanks for the info on the ANT BMS!


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## TimHug (Jun 24, 2020)

BVH commented that these packs cant be charged by the ubiquitous 96V chargers and so not so straight forward to find a suitable charger. 
Here is an inexpensive one I just bought : 9A , 900W $130 free shipping fast via UPS. Voltage per cell is 3.55V which is fine as max charge voltage is not that critical for LiFePO4. (Nominal recomended for A123 is 3.6V)








48V 58.4V 58.8V 72V 60V 67.2V eBike Lipo Li-ion Lifepo4 Battery Charger 12A EV | eBay


12V 24V 36V 48V 60V 72V 84V 96V you can choose. you can adjust the current 2A to 12A. output current : 2A to 12A you can adjust. suit for 20AH to 120AH Li battery. can suit for 99% Li batteries. Built-in thermostat.



www.ebay.com













It is available in a wide range of max charge voltages aimed at both LiFePO4 and LiIon. 
By carefully examining the max voltages you can use a LiIon voltage for LiFePO4 string, just depends on number of cells. This works especially well for LiFePO4 where exact 3.6V/cell is not super critical.
Here are the various options offered copied from the ebay AD but I edited the numbers showing additional LiFePO4 cell string numbers ,and voltage per cell wattage etc for 26S unit. If you contact them they will even make a custom voltage, which also means if you figure out which resistor is feedback you could tweak it yourself. Note that there are at least two different designs as the internal pictures here and elsewhere show some board differences. Probably one unit for lower voltages and another for higher ranges?

< suitable for 20AH to 120AH Li battery current adjustable from 2A to 9A
< suitable for a wide range of Lithium batteries choose from these models :
84V 28S lifepo4 102.2V output 102.2/28 = 3.65V/cell, 918W
96V 32S lifepo4 116.8V output 116.8/32= 3.65V/cell
23S li-ion 96.6V output ( LiFePO4 ~27S )
22S li-ion 92.4V output (LiFePO4 26S 92.4/26 = 3.554V, `830W) (This is what I ordered for A123)
24S li-ion 100.8V output (LiFePO4 100.8/3.6V ~ 26 cells)
26S li-ion 109.2V output (LiFePO4 109.2/3.6 ~ 30cells)
27S li-ion 113.4V output (LiFePO4 113.4/3.6V ~ 31 or 32 cells)
28S li-ion 117.6V output (LiFePO4 113.4/3.6 ~ 33 cells)
120V 32S li-ion 134.4V 5A (LiFePO4 134/3.6V ~ 37 cells)

The output does not switch on unless a battery is connected , display reads volts or amps selectable.
Fan is noisy but unit runs cool to touch. Upon connection current ramps up slowly to 12A, at max setting and then backs off to rated 9A. Output is to an IEC 13A female connector.


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## eelyot (Nov 2, 2020)

BVH said:


> I have acquired 4 of these 5KW, 26S3P/60 Amp Hour A123 Prismatic modules and plan to use them for my whole house backup system I will build. Each module has 2, 13S BMS "slaves" that probably reported to a master BMS controller. I’m not very knowledgeable in BMS’s but generally understand what they do. A member of a different forum tested one of the packs and slaves to see if it would passively balance by charging one individual cell of the 13 cells to 3.6 and observing with a Watt meter in the balance line. All other cells were resting at 3.3 Volts. It appears it is not functioning at all without the master. Are there 13 or preferable 26 cell capable, BMS's (systems) available that I could retrofit? Bluetooth would be nice. I really just need balancing but the other features are fine. I’m open to any solution. I’ll most likely be charging the packs individually with a Cycle Satiator, (no balancing capability) High Voltage version at a max of about 4.5 Amps. I know it’s slow but I have lots of time.
> 
> https://www.ebay.com/itm/A123-modul...icle-New-batteries-Less-100-KWh-/153713692059


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## eelyot (Nov 2, 2020)

sorry but I only see 2p. they are grouped in 4 not in 6


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## brian_ (Feb 7, 2017)

eelyot said:


> sorry but I only see 2p. they are grouped in 4 not in 6


Neat trick, counting cells in an image from an eBay listing which has expired so there is no image.

The real question: is eelyot a real person, or just yet another spambot?


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## eelyot (Nov 2, 2020)

in your posts you gave a link with pictures "( RC Groups - View Single Post - New A123 Pack? A123 Nano Tech LiFePo4 A123M1-HD 20Ah Prismatic )" I am also about to buy these battery modules (A123 systems 26s3p and 15s3p) but as I said before, in a 26s3p package I counted 52 cells and not 78 .If you want I'll come back with pictures from the seller. Pixy


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## TimHug (Jun 24, 2020)

I bought some of these packs from the original ebay link. The ones I got were certainly 26s3p . I had to exchange some of the packs from the vendor because some were over discharged. Although apparently essentially unnused (but ~3Y old). Supposedly they had only been cycled to check capacity but these packs were from an insurance shipping accident claim,so some had water/fire retardant damage particularly to the bms boards even though those are conformally coated. 

The 2 bms boards (13cells ea) one on each end of pack get daisy chained together on the can bus. They then can daisy chain to more boards on more packs. This allows them to be adressed as one giant pack with the cells sequentially numbered automatically by the onboard software. The BMS boards can only balance (300mA) they have no series pass devices to prevent overvoltage or over discharge . Having said that they have quite a lot of intelligence and can function in various balancing modes and voltage settings etc but the *boards are not activated to balance unless the CAN bus as well as the added board enable* *pins/supply voltage on the can bus connector are operating and parameters have been set. *I opted to use a different bms board but kept the plug and wiring which went to the original bms board. It was difficult to find a mating connector but eventually I found one I got from mouser, although I had to grind off the keying to make it fit. The pins are small and I needed a new crimp tool too.


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## eelyot (Nov 2, 2020)

this battery bank is about 15s3p, there are 30 cells and the one that writes 26s3p is 52 cells. my question is: isn't it 26s2p? I'm not a professional electrician ... thank you


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## eelyot (Nov 2, 2020)

battery pack


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## eelyot (Nov 2, 2020)

I come back with a clearer picture


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## brian_ (Feb 7, 2017)

eelyot said:


> this battery bank is about 15s3p, there are 30 cells and the one that writes 26s3p is 52 cells. my question is: isn't it 26s2p? I'm not a professional electrician ... thank you





eelyot said:


> I come back with a clearer picture


I have no idea who actually has what module, but this photo, with a label from A123 saying "26s3p", is indeed a 26S3P module. The pouch cells go the width of the module, with tab on each side. You can see the tab edges, which are clamped together through channels; there are two cells for each section of the plastic case (so there are 49 case sections for the 26*3=78 cells). The groups of six connected tabs are visible due to the black line where there isn't a connecting channel: that's three positive tabs from one group of three cells, and three negative tabs from the next group of three cells. You should also be able to pick out the BMS wiring running down the middle, with one tap going to each group of six connected tabs (just three tabs at the very ends of the pack), for a total of 27 taps.


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## eelyot (Nov 2, 2020)

Thanks for the explanations! Do I understand that there is another cell under the black line?


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