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opzsgu asked

PV system (MPPT + LiFepo4) + AGM - how combine for standby operation

Hello,

I set up tiny pv system with victron MPPT solar charger + victron lifepo4.

System work great day charge - noon discharge but i”m lacking ability to have emergency power (like ups) that will allow me work offline in case power outage (lifepo4) is in constant charge or discharge so i can’t rely on power stored inside when i have couple days of shade - lifepo4 is discharged and i”m working from grid -and this is what i want .

I would like have separated battery just for storage power only to use in case real outage. I make decision - now we have serious condition - i remove all non esential dc load and switch to backup

battery to power my computer.


I bought for that victron agm 110ah.


What will be the best way to combine this AGM as backup so it will be keep fully charged but wont be discharged until I decide?


first part is easy - i just buy isolated dc/dc charger and make it constantly recharge my AGM from that liion battery that is tied to solar but how to connect inverter / dc load?

hardware changing wires to agm seems like bad idea.

i saw boat switch but all of they have mode For combine both batteries - Im afraid how they respond when fully charged agm is connected to fully depleted 100ah lifepo4.

I seen victron have something like diode combiner - does this will be good for my use case?

or buy two isolated dc-dc chargers and hook one of them in way it recharge agm from lithium and second lithium from agm and then just add double throw switch?

in normal mode it will be charging agm - in reverse it charge lithium - that way i left all my load connected to lithium.

any ideas?

Lithium BatteryCyrix Battery Combiner
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1 Answer
Mike Dorsett avatar image
Mike Dorsett answered ·

a good way would be add some switching around the existing isolated charger so you can use it to charge either battery from the other..


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