question

richie-gorrod avatar image
richie-gorrod asked

24v or 48v

Hello

i am pretty new to this. I have 58 x 12v 130Ah AGM batterys.

Looking to go off gird.

I have 20 x 300w panels wired in 5 in series 2 parallel going into 2 x 250/85 MPPT controllers. There is room for at least another 20 panels in the area I am installing.

I have a couple of questions.

1. Can I wire all 58 of these Battery's into a 24v system with a balancer or would it be better to create of 48v system?

2. I have a 24v Multiplus II at the moment doing a load share and is working great but only running on 8 batteries. In the house I have an electric Aga that runs around 21a. This currently is just connected to the mains and rest of the house runs on the invertor. - Could I upgrade to a 48v system and run the aga as well.

thankyou.

Cheers,

Rich

48v battery
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3 Answers
nigelcharles avatar image
nigelcharles answered ·

48v is better than 24v for both cost and efficiency reasons. Cables don't have to be so big which reduces cost and losses. Inverters and controllers for a given output are cheaper.

All lead acid batteries have many disadvantages compared with LiFePo4 batteries. Until recently they had one advantage, that is cost. Now that LiFePo4 cells can be bought cost effectively direct from China the situation has changed. I bought 36 310Ah cells (over 30kwh usable power) for £3000 delivered to the UK with all shipping and duty paid last spring. I have just bough a second set for £3300. Previously 48kwh lead acid pack cost me about £4000. Remember it is unwise to discharge lead acids below 50% SOC so this was effective a 24kwh pack.

If you want to use you existing batteries I would test them, put the worst 10 aside, create two separate banks of 4S6P configuration. Even then keeping them all balanced may be tricky.

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richie-gorrod avatar image richie-gorrod commented ·
Hi Nigel,

thanks for the reply,

Interested in the batteries you built. My AGM's are coming to the end of there life and looking at options. wonder i should bite the bullet and go 48v.. BMS etc.

many thanks

Rich

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kevgermany avatar image kevgermany ♦♦ richie-gorrod commented ·
It probably makes sense, factor in the much longer service life of LiFePO4 and higher usable capacity.

The better ones have a sophisticated BMS built in, and can control the charging through a GX device like the Cerbo. Cheap is not always the most cost efficient over time.

It would be a good idea to discuss with a Victron dealer, then you'll get a full informed picture of the equipment needed, costs, service life. There are excellent batteries around at fair prices, but make sure fully compatible with your equipment and are properly supported.


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richie-gorrod avatar image richie-gorrod kevgermany ♦♦ commented ·
thanks Kev,

Will speak to my dealer but erring on the pylontech battery with can bus comms. Probably bite the bullet with a quatro 8000.

many thanks

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seb71 avatar image
seb71 answered ·

58 12V batteries are a little too much for a single battery bank.

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netrange avatar image
netrange answered ·

It will be very very hard to charge and balance ALL these 12V AGM batteries reasonably.
You need a lot of balancers and always enough voltage to balance the cells. When you are OFF GRID, you also have no possibility to maintain your batteries all the time.
The problem with such a connection is always that the batteries can break down on each other.
If you want to protect them with ARGO blocking diodes, you can't charge them so easily ...


The positive thing about so much AGM batteries ... Your garage no longer flies away so quickly in a storm

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