48-12v system

[Yvan]

My existing 12v system using 8x 6v fla’s is due for new batteries. I would like to get 6-8 100ah LiFeP04 batteries ( assembled myself from cells Will recommends).
My concern is with the suggestion to go to 48v. Since my home is set up for 12 v , changing everything would be tooa big of an expense .

Im running 3 3000w inverters( for redundancy, not using 9000w) and have 3 chargé controllers from my solar panels, plus a dc to dc charger from my alternator.
Is it safe to run 8 individual 100ah packs with individual BMS’s together to form a 800ah 12v pack?

 

[John Frum]

My concern is with the suggestion to go to 48v. Since my home is set up for 12 v , changing everything would be tooa big of an expense .

Would this help buck converter ?

 

[jasonhc73]

Is it safe to run 8 individual 100ah packs with individual BMS’s together to form a 800ah 12v pack?

Yes.

You can only invert so much 12V to 120 before the limits of inverters are reached and the size limits of wires are reached.

This is why 48v is used in whole house systems.

5000w @ 48V is basically 100 amps.
5000w @ 12v is basically 400 amps.

You simply cannot push 400 amps through small wires continuously.

 

[Supervstech]

My existing 12v system using 8x 6v fla’s is due for new batteries. I would like to get 6-8 100ah LiFeP04 batteries ( assembled myself from cells Will recommends).
My concern is with the suggestion to go to 48v. Since my home is set up for 12 v , changing everything would be tooa big of an expense .

Im running 3 3000w inverters( for redundancy, not using 9000w) and have 3 chargé controllers from my solar panels, plus a dc to dc charger from my alternator.
Is it safe to run 8 individual 100ah packs with individual BMS’s together to form a 800ah 12v pack?

As long as your 3 inverters provide the needs, changing to lithium and sticking with 12v system should be fine.
You can build the packs and use three BMS controlled setups, or you can tie ALL the cells into parallel -serial, so only one bms is needed.

 

[Yvan]

As long as your 3 inverters provide the needs, changing to lithium and sticking with 12v system should be fine.
You can build the packs and use three BMS controlled setups, or you can tie ALL the cells into parallel -serial, so only one bms is needed.

I’m thinking 32 Fortune cells, to give me 800ah capacity at 12v. It will fill the space I have for batteries, and give me twice the capacity of my lead acid set up I have now. What BMS do you recommend, and would 8 bms’s be better than 1 ? My maximum amp draw would be about 20 amps of 120v at any given moment ( that’s my AC at 9.6a, fridge at 3.8, and if my wife uses her coffee maker or microwave-8a)

 

[Supervstech]

If the BMSs are compatible, more is better, but if the batteries are balanced, a single one should handle minor imbalances.

 

[Yvan]

What bms is the best at the moment, and one that Will gets an affiliate link for, he deserves it.

 

[jasonhc73]

I thought fortune batteries already had a BMS in the pack?

 

[Yvan]

I thought fortune batteries already had a BMS in the pack?

Fortune cells

 

[Steve_S]

I might suggest you consider the size / amount of space & weight that 32 100AH cells will take up. Next add up the cost of 32 cells, + S&H on top and then add the cost of BMS'. Your in deep !

Sometimes Less is more.. take 200AH cells and you would only need 16 of them. 400AH cells and you'd only need 8
As well, I'll point out that there are some good deals out there which you may wish to ponder upon first.

On BMS' there are many varieties & flavours for various use cases. The standard fare BMS' like the Daly, or LLTC ones have ratings for MAX Amps for example 100A BMS, keep in mind that is the maximum edge, they 'may' handle a slightly higher surge but that's it... Always get the next higher up to what you think your MAXIMUM Demand will be. As previously pointed out, draw on 12V can get quite high and exceed 100A. Some BMS' are rated for specific voltage ranges as well. Then you will see other types of BMS' which use external relays and are not dependent upon the voltage limits nor the MOSFET limits for amperage as the amps are passed through the relays, not the BMS' itself. Chargery, TinyBMS and others are examples of that type of BMS. *NB* Packs in parallel, if properly configured to use a common-bus topology can share load across all the packs in the battery bank but again the proper selection of BMS' for this is required.


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Hope that helps.

 

[Yvan]

Thanks, space and weight are not really a concern, these will be replacing 8 lead acid batteries.
I prefer buying from a known and tested source in North America. This is for my home( we live and tour in our bus full time) so safety and reliability are top priorities. Also I don’t know where I’m going to be in 2 weeks, never mind à month, so planning to receive a shipment from China isn’t exactly easy.
I do like the idea though. Any US sources of higher AH cells?

 

[grizzzman]

Carl at electric car parts company has options and would work with you (even if you wanted a package deal)

 

[Yvan]

Thank you

 

[jasonhc73]

Scan the forum for BYD Batteries... Yep, used, so what they work. (they can be dismantled to 12V systems)

batteryclearinghouse and batteryhookup have them sporadically.