T-Pain Is On A Boat: [Electric Boats] Re: Battery diagnostics

Tuesday, June 23, 2009

[Electric Boats] Re: Battery diagnostics

"Finally - let's say you find one bad battery as I did. Are there any strategies for adding it into an existing "aged" pack."

Great question Keith. I'm dealing with that right now after finding a bad battery in one of my two banks. The bank is the newest set of batteries so it's about 9 months old.

I put a new (exact same battery) battery in the bank and tried charging. My PakTrakr showed the new battery being charged at a higher rate than the older batteries so I turned the charger off. I was told to try running the motor full out for about 15 minutes then cruise for a long time and try charging again. I did the 15 minutes full on in the slip and tried charging. It worked for a while (45 minutes?) then showed the new battery at a higher voltage (1 full volt) than the others. I turned it off. It seems it will take a while of vigilant monitoring while charging before I get a nice "patina" on the new battery so that it plays well with others :-).

Does anyone have any tricks?

Mark

--- In electricboats@yahoogroups.com, "aweekdaysailor" <aweekdaysailor@...> wrote:
>
> I'd like to add a section on my site about troubleshooting - particularly battery/range issues. But this seems like it's pretty much dark magic.
>
> To make it particularly tough I have a complex pack for both space and charging issues. It's 4 sets of (3 parallel) batteries cross-connected in series for 48V. From reading it seems this is sub-optimal but I'm not clear exactly on why (charge imbalance is the stated reason). I charge each set as a if it were a single 12V battery. One issue I suspect I face is sulfation because my charger output is so low (6amp) in comparison to the size of the set (345amp) - the batteries are sitting around in a discharged state for probably 3-4 days.
>
> I recently have been having trouble with greatly reduced range, and rapid voltage sag (like 40 down to 30 volts within 5 minutes). Reduced range I could expect due to sulfation, but the voltage sag was more troubling.
>
> First I checked water - I found a dry cell in one of my batteries a few weeks ago and thought that was the cause, but I dropped 1/3 of my pack (so now I am 4 sets of 2), that cell included, and it didn't help.
>
> Next I ran a load test after charge - couldn't see anything. (Sears has a nice 130amp load tester for about $50)
>
> Then I ran a load test after dropping the batteries pretty low. Bingo - 1 battery showing a dramatic difference. Pulled that battery and now I've got a range much closer to the predicted value (about 10AH down from "ideal"). And that's a string that has the "dry" cell battery in it (after refilling)
>
> Other than "divide and conquer", load testers, specific gravity and voltage meters - what other tools, strategies and processes can be used to diagnose battery issues?
>
> For example, I hear about "shorted" cells - what does that look like?
>
> Finally - let's say you find one bad battery as I did. Are there any strategies for adding it into an existing "aged" pack. All the stuff I've found basically says "don't do it"
>
> Thx
>
> -Keith
>