Using 1 solar array with 2 charge controllers

[BarkingSpider]

I have two 4kw battery banks, 1 AGM and 1 LifePo4 that need 2 different charging characteristics.
I currently have an existing 2kw solar array 4s4p at 80v to an Epever 40amp controller that is charging my AGM batteries no problem.
I want to try to connect my new LifePo4 bank to the same solar array and use the excess power I have to charge both battery banks.
I intend to connect a new charge controller to the same solar array in parallel to the existing Epever controller.

Has anyone done this before?
Will both MPPT controllers compete and cause problems
Should I use a PWM and a MPPT to avoid issues?

I want to avoid breaking up my existing solar array.
Any other suggestions?

 

[DIYVan]

I found a little board on Amazon that will energize a relay when a set voltage limit is hit. Coupled w/ a SPDT relay, you can swap between the two fairly easily (although would theoretically never be able to reach 100% charge on the primary pack).

Amazon.com

Someone on YouTube did this w/ a simple voltage gauge that had an adjustable alarm on it as well.

 

[tictag]

Has anyone done this before?

I don't know but for reasons that will soon become clear, I doubt it.

Will both MPPT controllers compete and cause problems

Yes.

Should I use a PWM and a MPPT to avoid issues?

No, doing so will cause more problems.

Any other suggestions?

MPPT SCCs work by presenting themselves as a varying load to the PV array in order to track the array's MPP as conditions change (e.g. clouds), if two are doing this, they will both be 'seeing' a varying voltage from the array and heaven knows what they'll make of it - it'll be like a game of 'Hungry Hungry Hippos' I would imagine (note: other 80's family board games are available). A PWM SCC work by essentially shorting the PV array directly to the battery, so the MPPT will see the array at say 60V one fraction of second then 24V (or whatever your battery voltage is) the next fraction of second. Again, Hungry Hungry Hippos time.

You obviously have your reasons why you need both LiFePO4 and lead-acid batteries together but this is like inviting a middle-class white man from Surrey to a dinner party with a Neanderthal from ancient Eurasia and expecting a 5-star review on 'Come Dine With Me'; you won't and they don't.

If you have to maintain two such battery banks then I would recommend having your array connected to one, then use a standard charger (either via an inverter or better still via a DC-DC charger to charge the other).

What do you do with the batteries? If powering an inverter, I do hope that you don't connect both banks to the same inverter.