[RE-wrenches] intermittent battery problem

William Miller william at millersolar.com
Sat Oct 8 11:09:23 PDT 2011


Ron:

Have you checked the voltage on the individual batteries during a low 
voltage incident?  You need to know if all the batteries have equally low 
voltage or if there is a specific battery with this problem.

Another possibility is a connection that is intermittently resistive.  We 
spend a lot of time cleaning battery connections.  We don't make a 
connection without wire brushing all mating surfaces.  Finding a resistive 
connection can be difficult.  I'd like to hear how other wrenches check for 
resistive connections.

William Miller



At 11:03 AM 10/8/2011, you wrote:
>Howdy Wrenches,
>
>One of my customers that lives 3 hours out in the back country is having 
>an intermittent problem that I haven't encountered before. The batteries 
>drop rapidly in voltage but hydrometer readings are in the green. Turning 
>off the inverter and just using DC doesn't change anything. Meters on the 
>Mate, Outback MX and Whisper controller are all the same so it's not a 
>metering problem. On the way to bed the batteries were at 25.4, overnight 
>with no loads they dropped to 22.9 then a short 15 min. charge with a 
>generator brings the batteries back up and two hours later they are at 
>25.8. This scenario has occurred several times and then doesn't appear for 
>a day or two.
>
>It doesn't seem to be sulfation as the batteries are reading good on the 
>hydrometer every time. All cells check out. The inverter doesn't seem to 
>be the problem. They have a Sunfrost on a separate DC circuit. It sounds 
>like an intermittent circuit problem or electronics issue. Customer has 
>checked and tightened all the connections he can get at but hasn't been 
>inside the components. Would appreciate any suggestions or clues before I 
>make the trip.
>
>Ron Young
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