BMS questions and recommendation needed...

Darce

New Member
Joined
Dec 4, 2020
Messages
42
I have recently purchased these LG Chem 48v modules from battery hookup. I have an Aims 6000w split phase inverter/charger on the way. My question is about adding a BMS to each module. I had originally purchased some 60amp Daly units (1 for each) but saw the charging side was kinda low. Only about 30 amps. I also started thinking about it and the cables included on the BMS units are 8awg while the manufacturer of the inverter calls for 0/1 wire. What gives? How is the BMS wire supposed to survive a full load on these batteries? From what I saw in the wiring diagram for the BMS it sits directly in between the battery and the load. I understand this is so that the BMS can cut the voltage for under/over protection but it seems to be a failure point. I am sure there is something I am missing as I am new to this.

Would a 100a 14s 48v BMS be a better choice for these batteries? Or another brand altogether?
At full 6000w and 48v the inverter is pulling 125 amps?
If I have 4 batteries this is split between all four so max of 31 amps each?
I am trying to clarify so I can build this properly.

I really need some advice lol.
Darce
 

snoobler

Solar Honey Badger
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Jul 10, 2020
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Location
HBR, AZ
I have recently purchased these LG Chem 48v modules from battery hookup. I have an Aims 6000w split phase inverter/charger on the way. My question is about adding a BMS to each module. I had originally purchased some 60amp Daly units (1 for each) but saw the charging side was kinda low. Only about 30 amps. I also started thinking about it and the cables included on the BMS units are 8awg while the manufacturer of the inverter calls for 0/1 wire. What gives? (1) How is the BMS wire supposed to survive a full load on these batteries? From what I saw in the wiring diagram for the BMS it sits directly in between the battery and the load. I understand this is so that the BMS can cut the voltage for under/over protection but it seems to be a failure point. (2) I am sure there is something I am missing as I am new to this.

(3) Would a 100a 14s 48v BMS be a better choice for these batteries? Or another brand altogether?
(4) At full 6000w and 48v the inverter is pulling 125 amps?
(5) If I have 4 batteries this is split between all four so max of 31 amps each?

(1) It depends on the insulation rating. Bare 8awg can handle almost 500A before it fuses. 135°C insulation can handle 90A.
(2) This is how a BMS works. It isolates the battery from the loads/charger to protect cells from damage.
(3) 14S per module sounds easier to me.
(4) for a sustained 6000W/48V = 125A. That AIMS is likely rated for 18kW surge for things like electric motor starting as they can have HUGE surge currents. You'll need to factor that in as well.
(5) Yes, provided you follow best practices per the "wiring" link in #2 in my signature.

Just be aware that this is the kind of lithium that explodes or catches fire if improperly handled and has a substantially lower cycle life compared to LFP. Important that you cycle it between 20% and 80% SoC to maximize cycle life.
 

Darce

New Member
Joined
Dec 4, 2020
Messages
42
Thank you for the response, I have downloaded the reference and will read through it.
 
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