Solar batteries

[stevemul]

I have been running a small 12v PV set up using 2 x 420W panels through a Victron 50amp controller to 4 x 100ah wet cell leisure batteries in parallel and a 3000/6000 inverter.
I saw a cheap 100ah LiFePO4 battery so I purchased it and swapped it to my system, disconnecting the non lithium batteries and it all works fine during these dull days producing me about 1KW per day which runs a fridge and a freezer. The lithium battery copes with the input just about without going into absorption. Next spring I plan to add another lithium battery.
I now have 4x perfectly good wet cell batteries which may well be useful to use as additional storage on sunny days when the lithium battery becomes fully charged and I am not using the excess input.
My query, please, is what hardware (ie switchgear) can I put between the two battery types to enable me to simply switch between the two battery banks? I am assuming that linking the two types directly is not possible or advisable but to be able to disconnect the lithium and switch to the wet cell may be feasible. Could anyone please sketch me a diagram and recommend the hardware required please?

 

[binky]

Sounds like a ' changeover switch' will do what you need.

 

[ExArmy]

Sounds like a ' changeover switch' will do what you need.

as long as it's rated to disconnect DC under load, or you had a way of disconnecting the load before switching

 

[johnb2713]

as long as it's rated to disconnect DC under load, or you had a way of disconnecting the load before switching

and you may need to change the parameters in the charging unit, low voltage cut off in the inverter etc.

 

[binky]

as long as it's rated to disconnect DC under load, or you had a way of disconnecting the load before switching

I wouldn't want to be doing anything under load, that would cause problems with the inverter settings as per John's post, as you would be changing the battery spec. All batteries should be fitted with isolators, so you could install a switch between isolators and the inverter.