Battery Drain with Disconnect

[piet10]

I am a brand new owner of a Greystone 29MK, and our inaugural trip is this week!

We had a second battery installed at the dealer because we will be doing a fair amount of dry camping. Because of all the parasitic drains on the battery, I installed a disconnect on the primary negative lead where it joins the negative bus. With a fully charged battery, after 4 days the battery is depleted about 1/4, with the battery completely disconnected the entire time. I have verified there is (0) parasitic current drain with the disconnect using an ammeter.

The only thing I can think of is a bad battery with excessive internal drain. Am I missing something?

Thanks for the help, we are looking forward to our new rig and participating in this form.

Al

 

[cookie]

Hello Piet10 and welcome to the forum. Lots of good information here.
If you have two batteries, are they both disconnected?
I believe that most disconnects are on the + side of the battery cable.
If your batteries are disconnected, you may have a bad battery.
One more thing, When you run two batteries they should be the same capacity.

Peace
Dave

 

[pegmikef]

sounds like a shorted cell in one of the batteries which would pull the whole battery down as well as the second if connected.

 

[porthole]

Good chance your dealer supplied you with cheap batteries, and one or both are bad

 

[Hastey]

sounds like a shorted cell in one of the batteries which would pull the whole battery down as well as the second if connected.

X2 on the shorted cell

Sent from my Kindle Fire using Tapatalk 2

 

[rick_debbie_gallant]

I may be hooking up a battery isolator. More to follow.

 

[porthole]

Rick - if you use an isolator do some research. Many isolators just use diodes. They work fine but the issue that diodes have is .6 volts drop across them. So unless you can adjust your charge voltage, or put a charge sensor after the diode, you will not get full charge capabilities.

 

[piet10]

Thanks for the replies. Both batteries are identical and good quality. I checked the wiring and it is correct. The disconnect switch is on the (-) lead, and zero current was confirmed with a meter. The bad cell theory sounds likely at this point.

We are on the maiden voyage for our rig and will be experimenting further.


Any other theories welcomed.

 

[porthole]

Any reason why you used the negative cable?

Something you can try with a test light. Disconnect a battery cable and put the test light in series, e.g. between the disconnected cable post and the cable. If it lights up you have enough of a current draw to kill a battery, under a day for a poor quality or small battery.

A digital meter, because of it's accuracy, may show a 12 volt draw, but it could be so low of a drain the battery could go for weeks with it.
Finding a bead cell with a maintenance free battery could be difficult without he proper tools.

If it is a conventional wet cell battery you can check with a battery hydrometer. A bad cell will be obvious with the reading.

 

[racingzr]

When using multiple batteries you need the same size AND the same age. Otherwise the stronger battery will just draw on the weaker one and you won't gain anything.