I have an AC500 EU with B300S batteries.
When the batteries SOC is getting low, I connect 2 external LFP batteries during night time using the DC input cable.
DC1 is working fine but DC2 is always switching off after a short while.
How to solve this problem ?
For better chances of getting help here, would you mind providing a little more information?
What are your settings for DC1 and DC2 on the AC500? Are they set to “PV” or to “other”? Did you enable or disable parallel mode for DC input?
Also it would be good to know the electrical properties of your external LFP batteries you connected to DC1 and DC2, so someone can compare those with the input capabilities of the AC500. The AC500 will likely disable any input if values are out of expected range.
I’m an AC300 owner. It is very similar, but not identical. But I’m sure someone will be able to help specifically with the AC500. Just give them as much information as you can.
DC1 and DC2 are set to “other”
Parallel mode for DC input is disabled.
External LFP batteries: Wattstunde LIX300LT, 3840Wh, 12.8V
Settings are OK as it is working on DC1.
DC2 switches off after a short time.
The input voltage of 12.8V is too low.
Connect both batteries in series to a DC input and you will get a voltage of about 24V. Then it will work.
Then why does it work on DC1 ?
In the manual is stated that you can charge from a car cigarette lighter port and from a lead-acid battery. This is less than 12.7V.
My LFP has a nominal voltage of 12.8V according to the specs.
Actual voltage is 13.2V.
Here is a screenshot when one battery is connected to DC1:
