gandude
east bay
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I built a charging station for my batteries and use the Harbor Freight maintainers. 7 batteries total w/6 maintainers.
The GFI breaker for the outlet that powers the maintainers tripped and I didn't know it. The maintainers draw power from the battery when A/C is removed. Has anyone installed a diode in-line on one of the clip leads or another device to prevent battery draining on the units?
Thanks
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1995brave
San Antonio, TX
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Need more information. Which maintainers are you using? And how are they wired up?
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Hiking Hunter
Warrior, Alabama, usually
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An in line diode would work to prevent discharge, however, there is a .6 volt drop across a silicon diode in the forward biased direction, so the batteries would not charge to their proper voltage.
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gandude
east bay
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These are the maintainers in use.
Maintainer
One maintainer per battery on group 24's and 31's total=6 and two ATV batteries wired parallel on one maintainer.
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gandude
east bay
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Hiking Hunter wrote:An in line diode would work to prevent discharge, however, there is a .6 volt drop across a silicon diode in the forward biased direction, so the batteries would not charge to their proper voltage.
I was afraid of that. 
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KendallP
Grants Pass, OR
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Yeah, that's a bummer. This is a definite design flaw.
They could have easily added that diode in the design and just upped the charging voltage to compensate.
That said...
My previous generation HF unit peaks a single starting battery at 12.92V. I brought this to the attention of mexbungalows and he expressed no concern whatsoever at typical wintertime garage temps and even a little lower.
Sure enough!
My boat battery sat in the garage all winter at about 45-50F on the 12.92V float. Before I put it to bed, I had desulfated and equalized it. SG was pretty much in line with brand new.
When I tested it this spring, the temp-adjusted SG was even higher. I don't know how, but clearly ol' mex was right and the 12.92V was not a problem for a 1000 CA starting battery.
Well the new generation floaters are more like 14.2V. I was thinking of adding that diode myself, just to bring it down to more like 13.6. Turns out 14.2 appears to be doing no harm, so I abandoned the project.
Bottom line?
If yours are the new gen and charge at this voltage, then I would add the diode.
***EDIT***
FYI: I've been informed, via email, by one of our retired engineers, Bigfootford, that a battery discharge caused by the loss of AC is common to many maintainers of this type and others. It is not merely a HF problem.
.
* This post was
edited 11/17/11 10:21am by KendallP *
Cheers,
Kendall
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Gdetrailer
PA
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Instead of a diode perhaps a relay with 120V AC coil and use the N.O (Normally open) contacts of the relay to interrupt the connection between the batteries and charger.
When the 120V AC is lost then the relay contacts open and no more charger drain during power outages or GFI trips.
Additionally you could also setup an alarm to notify you that the 120V power is out.
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riggsp
Charlotte, NC
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I'd find out why the breaker tripped before I tried anything else...how much current does the 6 maintainers charging 7 batteries draw...do you really need a GFI in this application...did the GFI trip due to a safety issue, or did the breaker trip from too much current draw.
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gandude
east bay
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The garage is large, >1500 sqft. There are 12 outlets on each side so GFI breakers were used - east plugs and west plugs. I rewired a few years ago with permits that required GFI. The GFI part of the breaker tripped because I disconnected the garage computer monitor for testing inside the house. It's tripped before when I disconnected, I just didn't remember the consequence.
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KendallP
Grants Pass, OR
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riggsp wrote:...or did the breaker trip from too much current draw.
400mA each
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