Anyone care to comment? Used LiFePo 12v batteries from medical equipment?

[luthj]

I'm not 100% certain but I believe the data cables are for the Battery management system (BMS), not for the battery voltage. If you watch the video above you'll see that he connects the data cables but he ALSO connects the batteries together at the terminals using standard battery cables like you would with any other big battery. In the video he is connecting them in parallel, don't know why you COULDN'T connect them in series, I suppose, if you needed a 24v battery for some reason. Why would you need higher voltage than 12?

Thats what I was trying to convey. If the batteries are aware of each other, then can use there internal balancing circuitry to bypass current around the entire battery, allowing the others time to equalize. Typically the BMS in these units can only bypass individual cells internally, as it has not idea what other batteries in the string are doing.

 

[DaveInDenver]

I'm not 100% certain but I believe the data cables are for the Battery management system (BMS), not for the battery voltage. If you watch the video above you'll see that he connects the data cables but he ALSO connects the batteries together at the terminals using standard battery cables like you would with any other big battery. In the video he is connecting them in parallel, don't know why you COULDN'T connect them in series, I suppose, if you needed a 24v battery for some reason. Why would you need higher voltage than 12?

That's what he meant, you have to connect them all together with heavy cables regardless but since the BMS can communicate with each other they may be smart enough to know they are in series or parallel and adapt their profile.

 

[Martinjmpr]

Here is the common use for the valence battery , a mobile medical computer cart.

View attachment 536919

I thought it was something like that. OK, silly question: Where is the CHARGER? I know these carts (and similar ones) are just rolled to the nearest outlet and then plugged in. So somewhere in the system there is a 120vAC charger. Is it built into the BMS or would there have to be a separate part that is the charger?

 

[luthj]

Charging is to a set voltage, no absorb. Then terminate.

 

[DaveInDenver]

I would be real surprised if BMS on the battery can recognise series or parallel.
An overall voltage display a function of apparatus being powered.
Most likely BMS only know how manage the battery its controlling, it firmware simply displays cells status of each battery by serial nr. or other identifier.

It couldn't know but could be told the configuration which might be useful when you add CANbus (like OBD2 maybe) to the BMS? Not sure it would do much without a controller for the load and charger, too. Might let the bank be semi-aware and balance itself without intervention.