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

[Bill Battagin]

Dana,

             You must have quite a bit of PV to switch out to 2 
FM100's.  You didn't mention what is the size of your battery and its 
chemistry, what's you C-rate?  If you're charging a large Lead acid 
battery and maybe it was discharged pretty deep and/or you have 
substantial loads once you hit absorb, once its reached absorb it may 
continue to process pretty high amps to hold that voltage as it works on 
finish charging a large pack up to 100%. How long is it putting out 2800 
watts per CC?

             Obviously this doesn't apply with L-ion

Bill

Feather River Solar Electric
Bill Battagin, owner
4291 Nelson St. (Shipping)
5575 Genesee Rd. (USPS, UPS)
Taylorsville, CA  95983
530-284-7849, 258-1641(cell)
CA. C10 Lic # 874049
Solar Powered since 1982
Home of the Sunny Side Up

On 9/7/2024 3:49 PM, Dana Orzel via RE-wrenches wrote:
> 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
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