Battery Voltage Increasing!

[ARCWINSTON]

I have 2 12v deep cycle batteries which are wired such that when the trolling mtor is plugged in they become wired in series to power the trolling motor (24v). As I do not use the trolling motor I took a plug of the same type as the trolling motor and configured it so that when the plug is in the receptacle the batteries are in parallel with the intention of using them as "house batteries", ie, everything other than the engine. After plugging in the parallel configured plug I have monitored the voltage to the fuse box and although it started out OK at 13 volts it has gradually increased over the last few days and is now reading 19 volts. I have unplugged the paralleling plug and the batteries read 13 volts each at the terminals. Why would the parallel voltage have increased to 19v? Thanks...W

 

[springhead]

Re: Battery Voltage Increasing!

not sure what u configured with a plug but its still a series circuit if your reading 19 volts,

 

[ARCWINSTON]

Re: Battery Voltage Increasing!

When they were in series they measured 24v right off. The way I had them they measured 13vto start with. The next day they were at 16v and today 19v

 

[18rabbit]

Re: Battery Voltage Increasing!

This is just a w.a.g. … the (+) and (-) of one battery is connected, even if poorly, to the (-) of the other battery through your special homemade plug. If I am correct (omg, I hope not!) you should be able to feel the tm leads to the battery that is shorted, getting hot. If so, (I hope not) you get to replace a couple batteries. The innards of that battery may have started to melt down, needs to be load tested. Unfortunately, unless the bats are brand new, you should not replace just one.<br /><br />Also, if I am correct (I’m still hoping not), your looking down the throat of a disaster trying to happen … fire. You should inspect every inch or your tm harness before reusing. It’s possible it was exposed to heat that may have compromised the insulation.<br /><br />Good news: I don’t know anything about electric trolling motors so I may have presumed something that is not correct with that tm harness. I’m presuming a pair of leads (+) and (-) to each battery.

 

[ARCWINSTON]

Re: Battery Voltage Increasing!

One of the things that really bugs me is when someone asks me for some help and then ignores what I offer so please don't think that I am doubting any theories or your input is unappreciated; at this point I will consider all offers. <br />The plug on the trolling motor connects the + of batt #1 to the - of batt #2 and thus makes the series circuit. What I did with the new plug was to connect the + of batt #1 to the + of batt #2 and the - of batt #1 to the - of batt #2 to make the parallel circuit. I tapped into the power by connecting to the + and - of batt #2. I have checked everything thoroughly and can find no source of short or cross connection. So, anything else will be appreciated. Thanks...W

 

[richg99]

Re: Battery Voltage Increasing!

Your connections are correct for parallel. <br /><br />I'd try another voltmeter,just to be sure that isn't the trouble area. <br /><br />However, as another poster already noted, you could be experiencing leakage through the wire insulation. It is the only thing that you can't really check without a load on. RichG TX

 

[cmyers_uk]

Re: Battery Voltage Increasing!

ARCWINSTON,<br /><br />Im new to this so may be teaching you to suck eggs but heres my thoughts anyway <br /><br />How are the batteries getting charged? is the voltage measured at the fuse box when at 19V when somethings charging the batteries? If not and you have connected the + to + and - to - you will not get more than 13V. To prove this just get some spare wire and connect then +,+ -,- and meter them it will read 12+V. If it was in series then it would be 24v unless something was causing a IR drop in which case something would be warm. If you leave the batteries for a few days and then check there voltage has it decreased?<br /><br />Thats all I hope its jogged something.<br /><br />Regards<br /><br />Chris

 

[ARCWINSTON]

Re: Battery Voltage Increasing!

The batteries were not being charged when I read them at 19v. I will try a different meter and get the batts load checked to see if they are damaged. There were no hot wires that I could feel but much of it is concealed. there was no smell of anything being hot or burned. The logical conclusion is a short of some kind but I can't find one. 12+12 in parallel = 12 so I am a bit lost. Thanks all for the suggestions...W

 

[Dunaruna]

Re: Battery Voltage Increasing!

Arc, can you draw a pic of your wiring curcuit? The way I read your post it seems to me that every time you connect the trolling motor you are completing the 24v curcuit for EVERTHING. Maybe I've misread your post - dunno.<br /><br />BTW, you could do a lot worse than get a reply from 18rabbit, he is very knowledgable.<br /><br />Aldo

 

[ARCWINSTON]

Re: Battery Voltage Increasing!

Well, the "problem" turned out to be my high dollar professional grade multi-meter. The more I thought it through the more I became sure that it had to be something simple; (Occam's Razor). So I bought another meter. New meter 13.5v Old meter 19v.I feel pretty stupid right now but thought the lesson I learned could be useful to others. Don't assume anything. I assumed that because my meter was expensive and professional grade it was telling the truth. Bad assumption. Thanks to all who offered help and my apologies for wasting your time...W

 

[Dunaruna]

Re: Battery Voltage Increasing!

Glad it was something simple. Its never a waste of time asking questions, this is a good reminder that a faulty multi-meter can cause mayhem.<br /><br />Merry Christmas.<br /><br />Aldo

 

[cmyers_uk]

Re: Battery Voltage Increasing!

Thanks for posting the solution , I was intreged. Even ran the problem past my physics teacher sister but here answer was its not possible! guess she was right.

 

[18rabbit]

Re: Battery Voltage Increasing!

Thanks for posting the follow up. And no one’s time was wasted. We’re all stuck on that big, infinite learning curve. <br /><br />Kudos to Richg99 for nailing a faulty dmm as the possible problem.