fan in circuit-breaker box is cycling every 10 seconds

All the above is on target. Also, not trying to be "uppity" here, but if it has a WFCO brand converter, it could just be giving up on you. My WFCO brand lasted about 7 years, then one night it just sorta freaked out, fan running on and off and the power was visibly going up and down as the lighting fluctuated bright and dim(well...not so bright). My batteries were perfect, the converter just up and croaked. I got a Progressive Dynamice retro-fit to replace it.....easy peasy, if that turns out to be the issue.