Placed my 12 volt battery on a trickle charger in the garage today. Friend insisted the caps that cover the water reserviors should be opened to avoid a build up of gases that would lead to an explosion. That sounds like a good way for the water to evaporate to me but I didn't want to contradict him. (He'd been kind enough to help me lift a battery that was too heavy for me.). And, to tell you the truth, I wasn't really sure?I'll watch the battery over the Winter. But should I re-cover the water reservoir with the caps? What say you? Caps on? Or caps off? Thanks, in advance,/CC

Leave them on, they're vented.Bill

When the batteries are in service they charge with the caps on.Leave the caps installed. And, use a battey tender, not a trickle charger.

I would NEVER use a trickle charger, but that's another story. In the old days I would always take the caps of when on the charger, and then put them back on when it was fully charged. Charge them up and then let them sit another month off season before charging again.Recently I had a problem with a battery that was still under warranty. The dealer said NO NO NO don't take the caps off when charging. Just for laughs I asked several other dealers. They all said the same thing.Now if you insist on trickling, and thus keeping the acid boiling all the time, then maybe you should check weekly for fluid loss, whether you use the caps or not.

Agree with others; they're vented and designed to be left in place when charging. Does your buddy take his off when he's driving his car? ;)

Quick Vote: Battery Reservoir Cover Caps -- On or Off?

pianotuna
Nomad III
Dec 17, 2017
Hi,

The electrolyte does not boil. It gasses from electrolysis. Voltage determines when that happens. The lower the ambient temperature the higher the gassing voltage.

nineoaks2004 wrote:
Leave them on.. Otherwise you could get contaminants etc. in the cells, the caps are vented and a trickle charge will not cause the acid to get hot enough to boil out anyway.
nineoaks2004
Explorer
Dec 17, 2017
Leave them on.. Otherwise you could get contaminants etc. in the cells, the caps are vented and a trickle charge will not cause the acid to get hot enough to boil out anyway.
pianotuna
Nomad III
Dec 17, 2017
All this fuss and bother when the best solution may be just to charge the battery fully, then disconnect it and leave it in the RV.
CopilotCompanio
Explorer
Dec 16, 2017
No, it's for my travel trailer. A single 12-volt battery. In his defense, he called tonight to ask about coming by to make sure it hadn't "boiled over". I had to confess I'd bought a battery tender. Saw no reason to school him on the subject. I think he was just trying to help?

Thanks for all the input. You guys are lifesavers.

/CC
John_Joey
Explorer
Dec 16, 2017
Many years ago batteries would explode during a fast charge. The caps now are vented, and their purpose is to stop contaminates from entering the cells.

You posted in an RV forum, but in the outside chance you're dealing with something (i.e. golf cart) that has an automatic waterier, then your friend might have something there. Those have been known to explode.
Walaby
Explorer II
Dec 16, 2017
Was wondering when someone would bring up the old concrete discharge issue. In my formative adult years, learning as an auto mechanic, my boss taught me that. Said I needed to put the battery on a couple of 2x4s to keep it off the concrete. Wasn't until many years later I learned the truth.

BTW - he also taught me removing the caps.. but didn't take me as long to realize that wasn't necessary.

Mike
CopilotCompanio
Explorer
Dec 16, 2017
Dave H M, you are psychic! He did just that! Except it was an old rubber welcome mat. For just that reason, he said?

Thanks for the tip on the DelTran Junior. I think I can pick one up at Advanced Auto Parts. Or, as I call it, "The Club".

Dave H M wrote:
CoPilot, why not just hop on Amazon or ebay and have a tender dropped at your door?

Your batt will be happy on its own for a while.

For long term service the DelTran Junior is the route I go.

I can see it coming, next your neighbor will show up with a piece of plywood to put under the batt to keep it from discharging while setting on concrete. :B
Dave_H_M
Explorer II
Dec 16, 2017
CoPilot, why not just hop on Amazon or ebay and have a tender dropped at your door?

Your batt will be happy on its own for a while.

For long term service the DelTran Junior is the route I go.

I can see it coming, next your neighbor will show up with a piece of plywood to put under the batt to keep it from discharging while setting on concrete. :B
CopilotCompanio
Explorer
Dec 15, 2017
Thanks to everyone who replied. As usual, your responses were swift and informative. I meandered down there this morning to replace the caps and disconnect the battery from the trickle charger. Will buy a "tender" later today.

Thanks, again,

/CC
mobeewan
Explorer
Dec 15, 2017
Leaving them off long term (weeks/months) could allow dust, dirt, spiders, bugs, etc., to get inside the batteries. As stated the caps are vented, leave them on.

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