Dynamically switch between multiple batteries?

[s0129]

I already have a Fox H1 gen2 inverter with a small 10kwh fox cube battery. The inverter only supports a single battery but I was wondering if I could add a battery emulator ev battery using some clever software and electronics. My thinking was to only have a single battery connected at one time but using contactors switch out which battery was connected. Obviously would have to do something similar with the BMS connection as well.
Something like.

• charge battery 1
• shutdown inverter
• switch battery 1 for battery 2 using connectors
• start inverter
• charge battery 2
  Etc

Would this be feasible with some custom software/electronics or is this a crazy idea?

If not I guess the best option would be to sell the existing batteries and get a larger EV battery.

[jasonday171973-eng]

Gen 2 supports multiple inverters in parallel with just the one CT clamp.
Though not gone much beyond that myself.

[Simply-Johann]

Yes, that's doable... if you were a developer. But based on how you phrased this question, my answer is: "yes, that is a crazy idea, leave it alone".
You're measuring the batteries in "kw", and you haven't even mentioned the voltage range of the two batteries.
Maybe they're a good match and will even work parallel WITHOUT ANY STUPID CONTACTORS??

[s0129]

The voltage range doesn't matter as I have no intention of the two batteries ever being connected in parallel, that is just stupid. And yes I have extensive experience developing software and building custom electronics. Just wondered if anyone has done something similar to this before.

[jasonday171973-eng]

AFIK Fox batteries don't have electrically operated contactors, just a manual switch. You do not wan't any situation arrising where you connect to 400ish volt batteries together directly in parallel as there is likely to be a large current inrush in the order of 100's of amps.
at best, you wreck 2 batteries. at worst, explosions and loss of life.
If you wan't to go down the big battery route. ditch the fox battery.
There are some inverters that can do dual battery.
But again, the fox battery at 10KWh is small compared to most EV batteries.

[Simply-Johann]

"You do not wan't any situation arrising where you connect to 400ish volt batteries together directly in parallel as there is likely to be a large current inrush in the order of 100's of amps"
Nonsense...
If both voltages are the same, NOTHING happens at all!
You should learn the basics of electrical laws first.

[jasonday171973-eng]

When I said 400ish volts. I mean label voltage,, not measured voltage.
The fox Battery can vary between 348v ~ 438v depending on state of charge.
Connecting up some random EV in parallel with differing number of cells in the pack and cell chemistry can also result in one pack becoming under or over charged.
The Dacia spring for example has a lable voltage of 216V-302V.
My point stands. don't connect random high voltage packs in parallel and don't tell ppl it's fine to do so.

[s0129]

I have no intention of having both batteries connected at the same time, this feels asking for trouble. Was thinking of using something like a changeover contactor to ensure only one was connected at once. What I don't know is how the inverter will react when the BMS connection is changed over and how it will handle different capacity batteries. I know I can add a second invertor running in parallel which is an option but obviously higher cost.