Adding more LiFePO$ batteries to one running an 12v inverter?

[Terrapin]

1. Can an additional 280ah battery be added to an existing 280ah w/ a 120A BMS battery at a later date +/- 4-6 months from the original being placed in occasional service?

2. Will adding the second battery change the amps available to the inverter?

3. Would the BMSs need to be of the same amperage rating? (example can a 50-80A BMS drive the second battery?)

4. Can cells from different two different manufacturers (assuming identical factory specs & same makers ones as 2P the packs) be put into a single 2P4S battery?

TY !

 

[snoobler]

1. Yes.
2. Yes. A second 120A BMS means up to 240A assuming perfect balance. Probably not perfect, but 80-90% of that is realistic.
3. No, but they would need to be suitable for the load.
4. Yes. You would need to test them to confirm each manufacturer's cells perform similarly even if different between brands. You would also need to interleave them, i.e., each cell group has an Eve and Lishen cell in parallel.

Short answer:
Everything must be as close to the same as possible - similar capacity, similar internal resistance, etc.

Best practice is always, all cells same manufacturer, same spec, same age. Improvisation and budgets encourage non-best practices that don't qualify as crappy ideas.

 

[Terrapin]

1. Yes.
2. Yes. A second 120A BMS means up to 240A assuming perfect balance. Probably not perfect, but 80-90% of that is realistic.
3. No, but they would need to be suitable for the load.
4. Yes. You would need to test them to confirm each manufacturer's cells perform similarly even if different between brands. You would also need to interleave them, i.e., each cell group has an Eve and Lishen cell in parallel.

Short answer:
Everything must be as close to the same as possible - similar capacity, similar internal resistance, etc.

Best practice is always, all cells same manufacturer, same spec, same age. Improvisation and budgets encourage non-best practices that don't qualify as crappy ideas.

TY...again Snoobler. this especially! "You would need to test them to confirm each manufacturer's cells perform similarly even if different between brands. You would also need to interleave them, i.e., each cell group has an Eve and Lishen cell in parallel." I CHOSE MY GUESS POORLY.

Now if the microwave will operate I won't need a second full battery based on Will's vid using a single 4S BMS with 8 cells. and if it doesn't work on the one battery it def. will in May/April when the next 4 cells come. THIS IS PERFECT!

I'll now base all the trailer wiring on the expectation It will be two batteries and if not It will be a very low loss harness.

Getting so close... thx!

 

[snoobler]

Forgot which BMS you had, but a 1000W microwave uses about 1600W. You'll need:

1600W/.85 /12V = 157A.

 

[Terrapin]

Forgot which BMS you had, but a 1000W microwave uses about 1600W. You'll need:

1600W/.85 /12V = 157A.

BMS is the 120A overkill, nuke is 800w, a 1300w max draw, add frig propane solioid, some led lights and safety monitors...maybe a vent fan (Been forgetting that till now. 8-/ ) ..... Yep It will be a second battery for certain...

I am done wishing. like the honey badger math don't give a shit. LOL

Seriously thx for dragging me though it this far. I will pay it forward helping where I can when I get there.

 

[GoWithTheFlowSolar]

1. Can an additional 280ah battery be added to an existing 280ah w/ a 120A BMS battery at a later date +/- 4-6 months from the original being placed in occasional service?

2. Will adding the second battery change the amps available to the inverter?

3. Would the BMSs need to be of the same amperage rating? (example can a 50-80A BMS drive the second battery?)

4. Can cells from different two different manufacturers (assuming identical factory specs & same makers ones as 2P the packs) be put into a single 2P4S battery?

TY !

1. I do not believe adding additional batteries is a problem.
2. Yes, if both sets of cells have a 120amp BMS, you can pull 240 amps.
3. I do not see why they would have to the same for them to "work". I would personally want them to match. If you had a 120 amp BMS and added a 50 amp BMS on your second set of cells, and your cells in both packs were the same, and cabling was similar, I would expect them to pull similar amperage. So then if you pulled over 100amps your each BMS would be pulling 50+ amps until the 50amp one would shutoff, then you would only be pulling from one battery. So a 50amp BMS would be especially problematic. In theory if your second BMS was 60amps it would not reduce your total output if both packs were powering equally, but I would still want them to be the same.
4. This might be something that would "work" but I doubt it is recommended and not sure if it would impact any warranty. I would be inclined to get a second matching BMS and just run two separate batteries.

Note, I have been running a 12v 120ah battery with 120amp BMS (this pack is about four months old) and two 12v 280ah batteries with 120amp BMSs. These packs are only about 3-4 weeks old.
They charge and discharge proportional to the size of the cells. So the 120ah cells will take about 3-4 amps while the 280AH cells are each charging at about10 amps. Voltage between the batteries stays pretty close. I have had these like this for two or three weeks and seems to work great, so far...

 

[Terrapin]

1. I do not believe adding additional batteries is a problem.
2. Yes, if both sets of cells have a 120amp BMS, you can pull 240 amps.
3. I do not see why they would have to the same for them to "work". I would personally want them to match. If you had a 120 amp BMS and added a 50 amp BMS on your second set of cells, and your cells in both packs were the same, and cabling was similar, I would expect them to pull similar amperage. So then if you pulled over 100amps your each BMS would be pulling 50+ amps until the 50amp one would shutoff, then you would only be pulling from one battery. So a 50amp BMS would be especially problematic. In theory if your second BMS was 60amps it would not reduce your total output if both packs were powering equally, but I would still want them to be the same.
4. This might be something that would "work" but I doubt it is recommended and not sure if it would impact any warranty. I would be inclined to get a second matching BMS and just run two separate batteries.

Note, I have been running a 12v 120ah battery with 120amp BMS (this pack is about four months old) and two 12v 280ah batteries with 120amp BMSs. These packs are only about 3-4 weeks old.
They charge and discharge proportional to the size of the cells. So the 120ah cells will take about 3-4 amps while the 280AH cells are each charging at about10 amps. Voltage between the batteries stays pretty close. I have had these like this for two or three weeks and seems to work great, so far...

Great, thanks!

 

[snoobler]

BMS is the 120A overkill, nuke is 800w, a 1300w max draw, add frig propane solioid, some led lights and safety monitors...maybe a vent fan (Been forgetting that till now. 8-/ ) ..... Yep It will be a second battery for certain...

I am done wishing. like the honey badger math don't give a shit. LOL

Seriously thx for dragging me though it this far. I will pay it forward helping where I can when I get there.

FWIW, you've been getting lighter with each drag.

 

[Larry Joe]

FWIW, you've been getting lighter with each drag.

Hi there
Newbie here, First post/question
On my RV I have been on solar for about 5 yrs now. Have been on 6v batteries using Bogart eng. TM2030 monitor & SC2030 charger & have been very pleased.
I also am using the magnum MS2812 with the programmable control.
I believe both systems can be used with the lithium setup with a little reprogramming.
I have now ordered 4ea 310ah lifepo4 and a 200a bms.
My main concern is that probably I am not going to have hardly enough amp hrs as I’ll eventually want & I would like to know if I can add say another string of 100ah batteries later. Also could I use another 100a bms with them. If this would work I’ll probably need a little help on wiring setup.
Thanks so much, Larry

 

[Terrapin]

Hi there
Newbie here, First post/question
On my RV I have been on solar for about 5 yrs now. Have been on 6v batteries using Bogart eng. TM2030 monitor & SC2030 charger & have been very pleased.
I also am using the magnum MS2812 with the programmable control.
I believe both systems can be used with the lithium setup with a little reprogramming.
I have now ordered 4ea 310ah lifepo4 and a 200a bms.
My main concern is that probably I am not going to have hardly enough amp hrs as I’ll eventually want & I would like to know if I can add say another string of 100ah batteries later. Also could I use another 100a bms with them. If this would work I’ll probably need a little help on wiring setup.
Thanks so much, Larry

I am on the first leg of the walk down the rabbit hole myself. It sounds like a very similar situation so from what I have learned above I am going to relay that it seems so. And that is very good news here. But as I pointed out be sure to include the final Amp usage in your battery wire gauge needs if you'll be increasing that with the added batteries. If your like me and the power available I will find a way to need it. Also it was suggested to me to post concise questions with numbers as it will be easier for those willing to help to offer specific answers by referncing the question numbers. Best of luck and welcome to here.