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-   -   Correct procedure for disconnecting Batteries (https://www.irv2.com/forums/f258/correct-procedure-for-disconnecting-batteries-267354.html)

michguy 10-19-2015 02:06 PM

Correct procedure for disconnecting Batteries
 
I will be storing my Motorhome for a couple months outdoors in Hot Springs, Arkansas. I did this last year, hit the battery disconnect switch and left. Totally dead Chassis batteries when I got back. I just replaced the Chassis batteries a month ago, but I'm thinking I should disconnect them so that there's no draw at all on them. What is the proper procedure or disconnecting, and do I have to disconnect both the Positive and Negative terminals?

Your All Things Electric, Idiot

Michguy

BrianGlenn 10-19-2015 02:22 PM

Simply remove the negative terminal connection. I choose negative (rather than positive) because if there are any capacitance charge devices on the positive circuit there is no chance to short it out if the positive connection touches a ground plane.

PS - make sure the battery is fully charged before leaving; a partially charged/dead battery can freeze in cold weather (below freezing).

Dutchstar08 10-19-2015 02:22 PM

All you need to do is disconnect the negative terminals. This is also the correct way when removing batteries or disconnecting to do work on the DC side.
Always disconnect the negative terminals first. When reinstalling connect the negative last. In that way there is no way for a positive lead to accidentally contact a grounded surface.

dennis45 10-19-2015 02:23 PM

There is no reason to remove the batteries as long as they are fully charged. Purchase one of these terminal disconnect devices for each Negative (Black) terminal (One for the House batteries and one for the chassis batteries) and use that to isolate the batteries. By disconnecting the Negative cable, you have completely isolated the battery from the coach.
Now, if you plan to store the coach longer than say 2-3 months, you can simply turn the switch back on, start and run the generator for a couple hours to fully charge the batteries and then turn the switches off again to store.
This link is an example, you should be able to find these at most Auto Parts stores.
P/S. Whenever you are removing a battery, always disconnect the Negative post first to avoid a short to ground. Use the same procedure in reverse to install by installing the Positive first and then the Negative last.

https://www.amazon.com/Post-Battery-M...connect+switch

okcnewbie 10-19-2015 02:49 PM

Just pull Negative lead.




That way if you fumble the lead like say the U of M punter .......

t55watson 10-19-2015 02:53 PM

Well Michguy maybe a SPARTAN can give you an answer. If you only have one battery disconnect switch that is for the house only. The chassis batteries are still connected and a draw-down is possible. Soooo add another disconnect switch. Or disconnect battery. Positive cable first (red 1 )then the ground (black 1 ). When reconnecting, red first then black.

Tony Lee 10-19-2015 02:58 PM

NO!!!

Negative cable FIRST, then positive. Reason is the most likely path for shorting out with a spanner is to grounded metal around the battery. No spark if you are disconnecting the negative. Once negative is disconnected then a short from positive to grounded metal doesn't matter.

ALWAYS possibility of very dangerous short from positive terminal to negative terminal via a spanner so care needed - of use wrench with insulated handle. Safety glasses recommended.

To replace, Positive cable first, negative LAST

Also smart to take a photo before you touch anything. Use black and red tape to clearly identify cables going to negative and positive terminals.

If you have two 12V batteries in parallel, then just disconnect BOTH negative leads.

t55watson 10-19-2015 03:02 PM

Quote:

Originally Posted by Tony Lee (Post 2790463)
NO!!!

Negative cable FIRST, then positive.

To replace, Positive cable first, negative LAST

Also smart to take a photo before you touch anything.

If you have two 12V batteries in parallel, then just disconnect BOTH negative leads.

If you touch the red cable to the positive post when the black cable is connected you will get a spark. Sometimes a BIG spark. This introduces the possibility of big BANG :nonono:from the gasses that are given off of a battery.:banghead:

BFlinn181 10-19-2015 03:04 PM

I think realistically just disconnecting the ground cable while the RV sits in storage is plenty.

Your present disconnect switch is an electrically operated solenoid, correct? If you added another one of those on the other set of batteries, where would the power come from to trigger the solenoid for reconnect???

If you do plan to remove all the cables from the batteries, not only take a photo but label them to make it clear where they go 4-6 months from now. If you just disconnect the ground cables, perhaps not needed. If the batteries are fully charged when you store the RV, they will be very close to full when you reconnect in the Spring, charged batteries will not freeze, so you should be good to go.

Tony Lee 10-19-2015 03:22 PM

If other motorhomes are like mine there will be two batteries in parallel for the engine battery and several cables, large and small, on each terminal. In that case, deciding how many disconnects and where to put them is not so clear cut.

Same problem with the house batteries. Bad design of course but some systems grow like Topsy and stuff that is added later is just connected to whatever terminal has a bit of space.

twinboat 10-19-2015 03:30 PM

Quote:

Originally Posted by t55watson (Post 2790466)
If you touch the red cable to the positive post when the black cable is connected you will get a spark. Sometimes a BIG spark. This introduces the possibility of big BANG :nonono:from the gasses that are given off of a battery.:banghead:

If the cable is going to spark, it will spark from the negative or positive cable connection.
You need 2 connections to complete a circuit.

Do not connect the cables while, or having recently, charged the battery. That is when it will be giving off the explosive gases.

A good, resting battery will not be gassing, otherwise they would be exploding all over the place.

Standard practice is to remove or connect the negative first for the reasons mentioned.

BFlinn181 10-19-2015 03:44 PM

twinboat, there you go introducing logic and fact into a discussion about electricity. Many folks still believe in magic smoke that can be released if the gods don't like you.

Forest Grump 10-19-2015 04:04 PM

I added a manual marine style disconnect.

tgdameron 10-19-2015 04:05 PM

Since batteries are so expensive and getting more so, I always take my batteries out and store them in the garage with a smart charger on them such as Battery Tender. I have 12v batteries. If you have two batteries, I do, I use the cable from the coach to hook positive of one battery to the positive of the other battery as well as the negative to the negative (12v batteries are hooked up in parallel). The Battery Tender is then hooked the positive of battery one and the negative of battery two. It produces enough amps to keep both batteries charged.


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