dead Batteries

[Bryce22345]

delivered the boat to the mooring on Mother's day. boat had been on shore power and had the batteries fully charged. 2 sets of 2 6V wet cell golf cart batts and group 27 start battery. went over this past weekend for the first time since getting her back (wonderful spring we've had in NE) to discover that both of the house banks were fully discharged. totally dead. 5 volts across what should have been 12 V banks. start battery was also severely discharged, altho it did start the yanmar. have been charging with genset/Xantrex 3000 invertor/charger for about 6 hours and have the house bank back to about 80% capacity. yesterday I fired the lap top up only to discover its battery was 98% discharged also. all the electronics, except the auto pilot have been tested for functionality and are working fine. tis my habit to ensure everything is off whenever I leave the boat. DC panel, battery switches etc. all off. bilge pump is wired to the start battery, but the bilge was dry, as in dry dry, so its not the culprit. Link 1000 battery monitor is the only other device wired directly to the house bank for power. no way it could suck 460AH's over three weeks.

so 2 questions
1. any thoughts on what may have discharged all the batteries. my initial thought was a lightning strike, but hard to believe since all the electronics are functional.
2. have no idea how long the house bank sat totally discharged. are they severely compromised at this point? they seem to be accepting and holding a charge.
thanks in advance.

 

[Don S/V ILLusion]

Dead batteries don't typically reach 5 V. Sounds like a short in one of the batteries cells which, because they are interconnected, drew down the other batteries. They are all probably ready for the recycle pile but you can try recharging after which I'd disconnect all of them to isolate what may be a bad one. Disconnect the charger (which may have a short to ground), let them reach a resting voltage. If the resting voltage appears good, check each cell with a hydrometer and compare the results.

 

[kloudie1]

I agree, Don.. One batt probably has a shorted cell.. Be very careful around those guys because if you've been charging and the short gets the slightest jostle, you could have a battery explosion .. Not a pretty thing to deal with in close quarters!! Make sure ya have on long sleeves and goggles.. Another way to test would be to pull all the interconnections and test across each batt.. the low one will be obvious after a very short time (maybe 20 minutes) .. You may get lucky with replacing only one, but again, Don is probably correct in that they are most likely ready for the pile.. I want to caution again, .. be very careful of the possibility of explosion in one cell.

 

[Stu Jackson]

www.amplepower.com, download the AP Primer from the tech docs tab. There's lots of good ideas about trying to bring wet cell batteries back from the dead, as well as how to Break In new batteries.

How old were the golf carts?

 

[Bryce22345]

batteries are 3 years old. US 2000.
I've never had a shorted cell before. wouldn't there be some visible sign, like loss of electrolyte? all cells have electrolyte well above the plates. the two banks were isolated as the 1-2-both switch was off. also it wouldn't explain the discharge of the start battery, also isolated and the deep discharge of the lap top battery.
it would seem that a shorted cell would not hold any sort of charge, which they seem to be doing. will check again today. will also dig out the hydrometer and see what that indicates.

 

[FourPoints]

Sounds like the charger may have a short and is drawing down the batteries. As for the laptop, 75% of people put their laptop in suspend instead of shut down, which continues to draw power, just at a lower rate. Even shut down some circuits are still powered up. I dont think 3 weeks to discharge the battery seems unreasonable.

 

[Ross]

My e3xperience has been : if you start having trouble with the batteries change them and damn the cost

 

[LloydB]

I don't know if this is the right manual but the one i found says:
If you set the Idle mode to 0 W, Idle mode is actually
defeated and the inverter stays on all the time. When the
inverter is on, it draws approximately 0.5 amps. This setting
is useful if you want to ensure uninterrupted power to a very
small load like an electric clock.
In 3 weeks that's about 250 amps. is the computer programmed to auto check for updates daily? was the computer battery charger plugged in?