Disconnecting parallel batteries

[FishingBob]

If I have to pull the batteries from my 2014 Parkliner to keep them from dying (it's in a storage lot, and not regularly on shore power), does it matter which negative I disconnect first? And when I go back to reconnect, which positive I start with?
Thanks

[Casita Greg]

Since you have two 12 volt batteries, you have two ground wires and two hot wires hooked up in parallel in your battery circuit.
(I mention this because some people have two 6 volt golf cart batteries instead of one 12 volt battery, but they would be hooked up in series, and thus would only have one ground anyway.)
To answer your question, it doesn't matter which ground wire you remove first, but the second part of your question infers that you are not just disconnecting the negative wires, but removing the batteries outright, (or else why would you care about which positive wire to re-connect first?)
Again, it wouldn't matter which positive you re-connect first, but I would suggest re-connecting both positive wires before re-connecting the negative wires.
As a suggestion, have you looked into installing a two battery selector switch, (Bat#1/Bat#2/Both/Off) and then you wouldn't need to disconnect anything, unless of course you prefer to remove the batteries for the time it is stored. Just switch to the battery you want to use or turn them both off. (When in the Off position, it will isolate them from the trailer's wiring so they wouldn't be drained by "phantom drains" like the smoke detector, propane detector, fridge control board,etc. which are always on if 12 volt power is available.) The nice thing about a selector switch is you can run on the battery you turn on, and you can recharge the one that is off while using the other one. Then you can switch them over and use the freshly charged battery while you're recharging the one you have used. You don't want to recharge both batteries simultaneously because no two batteries charge at the same rate. You could risk damaging one of them by doing that. Just a thought to consider.

Dual Marine Battery Selector Safety Shut Off Switch 2-ALL-1-OFF 4 Position | eBay

[Byron Kinnaman]

Unless there some metal that's has a path to the negative terminal near the batteries it doesn't matter which cables you disconnect first or last. Refer to Kirchhoff's loop law.

[stevebaz]

Take a picture of you battery connections before you remove anything. tag each wire so it can be put back in its proper place. now go ahead and disconnect the batteries.

This way you or some other battery installer can make proper battery connections at a later date. There are so many bad battery connections done with RV batteries causing a whole host of problems. Especially if the person who re-installs the battery connections at a later date isnt the one who disconnected them. Things happen and sometimes a trailer will sit for a very long time and memory fades. A good picture in a plastic bag left in the battery box can save allot of headaches later.

[Wayne Collins]

No need to remove the batteries. As long as the ground wires are disconnected, and the tops are clean and dry. They should hold a charge.

[Byron Kinnaman]

Originally Posted by Wayne Collins

No need to remove the batteries. As long as the ground wires are disconnected, and the tops are clean and dry. They should hold a charge.

OR THE POSITIVE WIRE.

Kerchoff's loop law.

[Byron Kinnaman]

There seems to be some confusion about disconnecting a battery. In a automobile the battery is close to the fenders, frame, or some other piece of metal. Here with the wrench on the positive post you touch the metal, which is connected to the negative battery terminal. That touch will weld the wrench to battery and vehicle and possible explode the battery.
However in other cases Like the trailer the battery is usually located in such a manner that the terminals are a ways away from any metal surface that could come into contact with a tool removing the positive terminal. Therefore unlike an automobile it doesn't matter which you remove first.
Just because in case there's a good reason to remove one side first doesn't mean that's true in all cases.

FYI in order for electrons to flow there has to be a complete loop. A brake anywhere is the loop and no electrons will flow.

[FishingBob]

Thanks. I may just disconnect the batteries and leave in place. There seems to be some significant phantom draw that I'll need to investigate, and hope to have it in my driveway for a time, but the county could potentially complain. In the lot, if charged, I imagine the batteries would probably be ok without any minder, at least for a few weeks.


I've actually still not seen the batteries (had the Parkliner over 2 weeks now but work and Irma have kept getting in the way). The battery case needs to have the propane tanks removed before the case can opened, and I just haven't gotten to it, but the Trimetric 2025 now shows a draw as high as 2.9 amps, and everything's off. I'll certainly take pictures, and try to figure out a location for a disconnect switch.

[The Minimalist]

Originally Posted by Byron Kinnaman

There seems to be some confusion about disconnecting a battery. In a automobile the battery is close to the fenders, frame, or some other piece of metal. Here with the wrench on the positive post you touch the metal, which is connected to the negative battery terminal. That touch will weld the wrench to battery and vehicle and possible explode the battery.
However in other cases Like the trailer the battery is usually located in such a manner that the terminals are a ways away from any metal surface that could come into contact with a tool removing the positive terminal. Therefore unlike an automobile it doesn't matter which you remove first.
Just because in case there's a good reason to remove one side first doesn't mean that's true in all cases.

FYI in order for electrons to flow there has to be a complete loop. A brake anywhere is the loop and no electrons will flow.

Byron, I would suggest that despite Kerchoffs loop law and that trailer batteries are 'usually' away from possible metal contact, best practice would always be to disconnect the the negative terminal first.

Regards.

[Byron Kinnaman]

Originally Posted by The Minimalist

Byron, I would suggest that despite Kerchoffs loop law and that trailer batteries are 'usually' away from possible metal contact, best practice would always be to disconnect the the negative terminal first.

Regards.

As I pointed out that's a myth associated with automobiles. It matters NOT with fiberglass. Of course it's up the person doing the disconnection which terminal is disconnected first or last.

[Wayne Collins]

Well, as luck would have it; I went out and checked battery voltage on our ParkLiner which has been parked since early July. It was down to 8.5 volts.
I suppose the smoke detector is the only parasitic load. or, could it be battery powered?

[Byron Kinnaman]

Originally Posted by Wayne Collins

Well, as luck would have it; I went out and checked battery voltage on our ParkLiner which has been parked since early July. It was down to 8.5 volts.
I suppose the smoke detector is the only parasitic load. or, could it be battery powered?

My guess the battery voltage would be about the same without the propane detector. Batteries have a self discharge rate the is often close to the same rate as your propane detector. The best bet is keep the batteries charged by some method or another. If no power is available a small solar panel set on top of the trailer could do the trick.

[FishingBob]

Originally Posted by Wayne Collins

Well, as luck would have it; I went out and checked battery voltage on our ParkLiner which has been parked since early July. It was down to 8.5 volts.
I suppose the smoke detector is the only parasitic load. or, could it be battery powered?

Mine (2014 Parkliner) was parked in a lot for four and half days, and I pulled it home this morning. When first parked at the lot, it showed 98% battery; that was down to 75% Wed evening (and 12.9 v., and -2.9 amps), at 64% when I pulled it home this morning (12.7 v. and -2.7 amps). It went on shore power, started charging, and soon showed 13.3 v.
Although I suspect a draw more significant than what should be expected, I really need to spend more time with that Trimetric manual.

[Wayne Collins]

Originally Posted by Byron Kinnaman

My guess the battery voltage would be about the same without the propane detector. Batteries have a self discharge rate the is often close to the same rate as your propane detector. The best bet is keep the batteries charged by some method or another. If no power is available a small solar panel set on top of the trailer could do the trick.

I do have a small solar panel, but the 12 v outlet on this trailer is dead, have not found why.