[RE-wrenches] Fm100’s stuck at full charge

[Dana Orzel]

OK, you wise guys.
I am upgrading my home off grid system from two FM 80s to two FM 100s.
The FM 80s were able to share the negative wire so you didn’t have to pull a second negative wire.
I wired the FM 100 typical of how my FM 80s were wired with a number four battery negative assuming and yes, I know what happens when I assume, that the PV negative on the battery negative are common and I could just pull one number four since going through those double 1” - 90° is a bitch. Currently I have two # fours for output to battery, the number eight ground and 1 # six PV input.
I got this all together and it’s charging just fine but once the battery got full charge controllers continued to produce full output. The battery dropped to a float and I had 2800W on each charge controller continuing to be produced at which was turning into heat so the FM 100s were getting very warm. The fans had not turned on, but the heat sinks were definitely very very warm to the touch. The battery voltage is fine.
I Read the manual it doesn’t talk about being able to use one negative so I am assuming that my problem is that the PV needs a negative and they do not share the negative.
Has anybody else seen this or done the same wiring maneuver.
 thanks in advance

Dana Orzel - dana at solarwork.com - 208.721.7003