Moving from 12v FLD to LiFePo4

Simple questions about LiFePo4's.

1 - Is it better to buy 2- 12v 200ah in 2p or go with one 12v 400ah?

2 - Is it recommended to connect 2 - 12v in 2s for a 24v setup? I've been told it's not

I'm looking to go with LiTime, Eco-Worthy or PowerQueen battery
Thanks!

1. Single point of failure (there are usually a lot of those, so whatever is cheapest should really be the consideration.)
2. Buy a 24v battery. They are out there. Victron does have a balancer for just such a use case, but easiest to just buy what you need.

Chris1407 said:

better to buy 2- 12v 200ah in 2p or go with one 12v 400ah?

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Being able to handle the weight may be an issue. Most 200Ah will have a 200 amp BMS giving a 400 amp capability, a single 400Ah, ( if they exist) may only have a 200 amp BMS.

Chris1407 said:

Is it recommended to connect 2 - 12v in 2s for a 24v setup?

Click to expand...

If possible avoid two in series for 24 volts. Use 24 volt batteries, in parallel if a greater Ah capacity is needed. As Just John suggested 12v batteries in series with a battery balancer is an option.

1. Yes, No, Maybe.
2. No.

mikefitz said:

Being able to handle the weight may be an issue. Most 200Ah will have a 200 amp BMS giving a 400 amp capability, a single 400Ah, ( if they exist) may only have a 200 amp BMS.

If possible avoid two in series for 24 volts. Use 24 volt batteries, in parallel if a greater Ah capacity is needed. As Just John suggested 12v batteries in series with a battery balancer is an option.

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Good point for the BMS amp I didn't thought about that.

What are the pros of going 24v?
I'm running a 12/24v DC full size refrigerator/freezer.
All the rest, lights, water pump, fan is 12v where I would use a step down. Plus I have a rarely used 1500W inverter for device charging and TV.

What are the pros of going 24v?
I'm running a 12/24v DC full size refrigerator/freezer.
All the rest, lights, water pump, fan is 12v where I would use a step down. Plus I have a rarely used 1500W inverter for device charging and TV.

At the moment I have 2- 290W panels and a SRNE 60amp MPPT controller and I don't mind if I must upgrade.

In your case there may not be any reason to go 24VDC. If you plan to change over to more AC appliances from the present 12vDC than the 24vDC to an inverter will facilitate more loading. Twice the voltage, half the amps.

Chris1407 said:

What are the pros of going 24v?

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Lots of info on this topic here. Watts = volts * amps

If you need more than 2000w of power total you should go to 24v or 48v. If you need more that 3000w you need 48v.

mikefitz said:

Being able to handle the weight may be an issue. Most 200Ah will have a 200 amp BMS giving a 400 amp capability, a single 400Ah, ( if they exist) may only have a 200 amp BMS.

If possible avoid two in series for 24 volts. Use 24 volt batteries, in parallel if a greater Ah capacity is needed. As Just John suggested 12v batteries in series with a battery balancer is an option.

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Winston produce 1000ah cells though I've only seen 500amp bms's, though I'm sure 1000amp are available.

Chris1407 said:

Simple questions about LiFePo4's.

1 - Is it better to buy 2- 12v 200ah in 2p or go with one 12v 400ah?

Click to expand...

Price and fit for purpose normally are the factors here

Chris1407 said:

2 - Is it recommended to connect 2 - 12v in 2s for a 24v setup? I've been told it's not

Click to expand...

No not for lithium, you need to order the cells to the voltage then have a single BMS that covers that voltage/amperage.
NB you can balance two 12v batteries and use them as 24 but it can be trouble and if your buying new why bother.

robbob2112 said:

If you need more than 2000w of power total you should go to 24v or 48v. If you need more that 3000w you need 48v.

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I'm right on the edge needing 2200W. I think I will go 24V for the simplicity of expansion in the future.

Chris1407 said:

I'm right on the edge needing 2200W. I think I will go 24V for the simplicity of expansion in the future.

Click to expand...

Sounds like the best answer - make sure to get the 200ah version of the battery - it should come with a 200 amp BMS inside it.

And Keep it simple - get 1 24v100ah and if you need more power add a second one in parallel.


And I am a fan of the Li Time batteries because I have several and they are great. Capacity test showed 10% over rated capacity. And in the teardown videos they were using all grade A prismatic cells.

If temperature is going to be near freezing look for self-heating.

I've seen videos and looks like the powerqueen are similar quality to the Li Time.

I've seen more than one complaint on the eco-worthy batteries that they are using grade B batteries or the capacity test shows less than rated.