converting 12v battery bank to 48v

[pctree]

Probably a silly question but I have 6 GNB H1T-41 batteries in series, each battery is 2v with a 4000ah capacity. These are large and expensive batteries so I hope to keep utilizing them. My issue is I want to expand my system and would love to have a grid tied system with a decent sized inverter incorperated but am realizing it would be preferable to have a 48 volt system for this. I assume I cant safely add 3 12v smaller batteries to them and charge with PV array ?

Could I get 4 AGM batteries and somehow have the 12v system charge the 48v to increase its capacity ?

Any input appreciated

 

[A.Justice]

Unless you get 18 more of the exact same cells in series, you won't be able to reuse your existing battery cells for 48 volts.

With a battery that big, that still functions, I would build an additional 48v system. Most of the components won't be compatible anyway. To switch from 12 to 48 volt you would need to get a new inverter, probably a charge controller, and possibly fuses / breakers. You would keep some loads running on your 12 volt system / inverter, and other loads running on your 48 volt system.

 

[Mattb4]

If you want a 48vDC battery system you would be better served to have all your batteries of like type and age. Perhaps sell the present battery?

 

[pctree]

I am coming to the conclusion That I need to get a new 48v battery bank and something like an outback radian to charge it and sell to grid.It would still be desirable to power the 48v system with the 12v if the grid power goes out at night

 

[Rocketman]

I am sure is possible to do - to boost the 12v to 48v - but I doubt it’s practical to do.

Sterling makes a 12v to 48v Dc-Dc charger. 70amps of 12v Dc to 13amps of 48v Dc. It’s like $450.

The real problem is the how much power you can put through it. It would probably be better to sell your 12v battery…

Your idea of having a 48v battery and using this to recharge it is possible, but the 48v battery would need to be sized for the loads (I.e. inverter). The other issue is the power losses. To charge the 12v battery you have losses, then to convert to 48v you have losses, then to charge the 48v you have losses. My guess is all the losses plus to cost of the Dc-Dc charger, plus what you could sell your 12v battery- really makes it impractical.

Good Luck with your decision