Migrating from 24v to 48v.

[wingedlizard]

I am upgrading from a growatt 24v inverter to an eg4 6000xp 48v inverter. I've order 1 48v EG4 LL battery ( 100ah) as well.

My current system consists of two 150AH 24v batteries in parallel ( 300AH). I want to serialize these into a single 150AH 48v battery, then put the EG4 battery ( 100AH) in parallel to make a single 48v bank of 250AH.

There have been many posts that say this is not a problem, however Signature Solar told me it would "not be compatible". When I asked what would not work he did not give a very good answer. I suspect it's probably just something they don't want to support.

First question, am I wrong to do this? If so then why not? What will 'not work'?

If this is ok, then I probably need a battery balancer to keep the 24v batteries at the same voltage. I see many 4x12v balancers, but Have not found a 2x24v balancer. Does anybody have any suggestions?

Next question, If I put a victron smart shunt on the 2x24v bank, will EG4 recognize the battery as a separate bank ( it is probably an incompatible protocol)?

FWIW, I currently use solar assistant, It may not be necessary, but I'd like to keep using it. Can it be used to monitor the victron smartshunt ( second battery bank), and let the EG4 6000xp monitor it's EG4 Battery? alternatively, I suppose I could just put both batteries behind the smartshunt and tell EG4 is it one 250AH battery.

All batteries are lifepo4, and I am planning to use busbars. My cloud energy cl24-150 24v battery specs say they can be combined with themselves in parallel ( 4x ) and serial ( 2x ).

Any warnings/caveats?

Thanks

renogy 12v -> renogy 24v -> growatt 24v -> eg4 48v (I have lots of unused parts)

 

[Steve_S]

The "optimal" method is a big more difficult but the end result is best and will provide little to no issues going forward.
1) Take apart the 2 24V/150AH batteries and put the 16 cells into a 48V config. There are cases available to handle that & more.
2) Get a Compatible SmartBMS, I am partial to JKBMS Inverter edition which has inverter comms etc & can be managed by PC Software & Phone App etc. JK is also one of the few with Active Balancing built in and it works really well. This can also be connected to Victron - it supports it & more.

Gotcha's:
- The 150AH cells should match (make/model etc) depends on what they are.
- Disassembly requires patience & deep breaths because the cells may be diff format, or have lasered busbars etc...
- Can really get a replacement casing till you know what you got... And it takes a while to get once you know. * Some things are available in US.

 

[seneysolar]

My current system consists of two 150AH 24v batteries in serial ( 300AH). I want to parallel these into a single 150AH 48v battery, then put the EG4 battery ( 100AH) in parallel to make a single 48v bank of 250AH.

You have the terms backwards. Maybe thats why SS said you cant do it?. Do i understand you have (2) 24v 150AH batteries? Likely parallel to remain 24v but get to 300AH. Then yes you would need to series these to get 48v at 150AH.

I cant speak for eg4 compatibility but lots of folks parallel different brands of LFP batteries and different AH ratings.

 

[zanydroid]

I am upgrading from a growatt 24v inverter to an eg4 6000xp 48v inverter. I've order 1 48v EG4 LL battery ( 100ah) as well.

My current system consists of two 150AH 24v batteries in serial ( 300AH). I want to parallel these into a single 150AH 48v battery, then put the EG4 battery ( 100AH) in parallel to make a single 48v bank of 250AH.

There have been many posts that say this is not a problem, however Signature Solar told me it would "not be compatible". When I asked what would not work he did not give a very good answer. I suspect it's probably just something they don't want to support.

First question, am I wrong to do this? If so then why not? What will 'not work'?

If this is ok, then I probably need a battery balancer to keep the 24v batteries at the same voltage. I see many 4x12v balancers, but Have not found a 2x24v balancer. Does anybody have any suggestions?

Have you confirmed that the BMS in the 24V batteries are tolerant of being put in a 48V series setup? At least one of the BMS will see 48V on disconnect, and that could fry the FETs if they're not rated for it.

Another idea would be to get a 48V BMS, crack open the 24V batteries, and attach the voltage and balancer wires to it.

IMO the expertise and liability needed to commercially support combining low cost batteries together outweighs any income that can come from it in the US.

 

[wingedlizard]

You have the terms backwards. Maybe thats why SS said you cant do it?. Do i understand you have (2) 24v 150AH batteries? Likely parallel to remain 24v but get to 300AH. Then yes you would need to series these to get 48v at 150AH.

I cant speak for eg4 compatibility but lots of folks parallel different brands of LFP batteries and different AH ratings.

You are correct. I will edit my post.

 

[wingedlizard]

Have you confirmed that the BMS in the 24V batteries are tolerant of being put in a 48V series setup? At least one of the BMS will see 48V on disconnect, and that could fry the FETs if they're not rated for it.

Another idea would be to get a 48V BMS, crack open the 24V batteries, and attach the voltage and balancer wires to it.

IMO the expertise and liability needed to commercially support combining low cost batteries together outweighs any income that can come from it in the US.

Yes. 2 serial and 4 in parallel. web page states "4P2S" for a max of 30.72 Kwh.

There are laser welds.. not sure I want to do a dissection and resurrection.

 

[zanydroid]

Yes. 2 serial and 4 in parallel. web page states "4P2S" for a max of 30.72 Kwh.

There are laser welds.. not sure I want to do a dissection and resurrection.

OK. I’m curious as to whether it is recommended to solder on sensor and balancer leads on top of that. Or cut the existing sensor/balancer wires and splice them into new BMS.