Battery Storage for Winter

johnm1 wrote:

I have no option to charge the batteries during storage

You still have not told us how long they will be out of service.

If you don't somehow keep them charged it is a gamble and the odds get worse the longer they sit.

The cold is good, in general because it slows down the discharge process.

DrewE wrote:

I'm going to disagree with the iffy-ness of two months.

I knew this would happen.

So pick a number: 3 months, 5 months, 7 months.......
The actual number depends on how it is stored and how much "wear" the batteries have to start with.

IMHO, a wise person will check and recharge as needed in the MINIMUM interval, not some arbitrary extended period.

YMMV.

Cold is a good thing for battery storage (at least in terms of self-discharge).

There are limits to the general rule, but not at Rochester-like temperatures. In genuine arctic conditions, there may be a risk of a charged battery freezing (at something like 90 degrees below zero), but that's definitely not the case at Rochester. A discharged battery is quite a different story; it stands a good chance of freezing and cracking and being even more dead afterwards if that is possible.

They will store six-months just fine if the following conditions are met:

Charge them until all six cells are slightly bubbling. This is not the easiest thing to acheive with today's chargers. So try this - charge them repeatededly perhaps six times and leave them on the charger or converter for a week solid.

Disconnect them by unhooking the ground cable.

Wait three days then check individual battery voltage.

6.35 volts per battery means they could not have been charged fuller.

Recheck voltages in the Spring. They should not have degraded to a voltage of less than 6.25

Try to give them a good charge rather than just use them normally at first.

Storage temperature has a profound effect on the efficacy of electrolyte. The effect is not linear with temperature. A difference of ten degrees say 80-90F is the same as from 70F to 48F.

The secret and the hard part is to get those batteries fully charged then electrically isolated. Sometimes I wonder if battery companies pay a stipend to charger manufactuers to ensure their chargers are too stupid to prevent battery damage. Notice the word CHARGER.

Sorry - forgot to add that they're plain old 6v wet cell GC batteries.

Drew - I'm missing something ... is the "cold" of Rochester a good or bad thing fro batteries?

I have no option to charge the batteries during storage so it's either leave them on the RV or bring them home. I would MUCH rather leave them on the RV if it's safe to do so.

Sam Spade wrote:

johnm1 wrote:
then disconnect the batteries at the storage lot and leave them until spring?

If they are AGMs, that will absolutely be fine.

If conventional lead-acid and the down time is more than 2 months it's gonna be iffy.

The cold will slow the process of self-discharge but not stop it.

It is better to give then a charge every 4 to 6 weeks.....however you can manage that.

And just to clarify, they might not be down far enough so that you notice a big difference in the spring but it's bad for them and after a few years of that, or some other deep discharge incidents, they will be aged beyond their years.

I'm going to disagree with the iffy-ness of two months. Rochester is plenty cold (I know; I studied at the Rochester Institute of Technology for six years), and the rate of battery self-discharge is exponentially related to temperature changes. An approximate rule of thumb is a factor of two difference for every ten degrees. A week or so in a Florida summer very likely involves more self-discharge than all winter season in Rochester, NY.

Here's a white paper from Trojan on the subject, including a nice little graph of self-discharge at various temperatures for T-105 batteries.

johnm1 wrote:
then disconnect the batteries at the storage lot and leave them until spring?

If they are AGMs, that will absolutely be fine.

If conventional lead-acid and the down time is more than 2 months it's gonna be iffy.

The cold will slow the process of self-discharge but not stop it.

It is better to give then a charge every 4 to 6 weeks.....however you can manage that.

And just to clarify, they might not be down far enough so that you notice a big difference in the spring but it's bad for them and after a few years of that, or some other deep discharge incidents, they will be aged beyond their years.

Sorry to bring this back up but this is the 1st year that I have to store my RV in a lot without power for the winter. It used to sleep next to the garage but we moved. I'm in the Rochester NY area so it gets cold but nothing like the brutal cold some of you are talking about.

Am I correct that one of the agreed upon ways to store RV batteries is to top off the water (distilled ... right??), then make sure it's got a good full charge (it's plugged into a Powermax Boondocker PM4B-75 MBA at home 24/7), then disconnect the batteries at the storage lot and leave them until spring?

Thanks

I live further north (just east of the beginning of the Alaska Highway) than any of the posters so far and I have had no problem leaving the batteries in place all winter. I do check the voltage every month or so and if down a tenth or two I put a charge on overnight - once or twice over the winter.

I like the suggestion of cleaning the snow off the collector and letting it look after the battery. That sounds easier than hooking up the charger.

It is harder to remember to check the water level at the beginning of the camping season when you don't take them inside, though.

Just upgraded to an AGM battery and PD 4655 converter. No more inspecting the battery and having to top it up. Our old WFCO converter destroyed 2 Interstate FLA batteries in 2 1/2 years - have always left it plugged in all winter and always kept it topped up.

Am I correct that you can just leave an AGM hooked up and use the PD all winter to look after the AGM and have no worries?

Interestingly, when you put the WFCO and PD converters side by side, there sure is a big difference. THE PD has two fans, huge heat sink, larger toroidal cores, larger caps (physically), heavier wire everywhere.

Ya know, ya hear folks saying how the WFCO converters are cr*p and until yours cr*ps out, ya think it will never happen to you. I'll never use one again. For no reason it also tripped the breaker and started to smell like burning insulation. It is NOT fun when you have to get and replace a battery and converter while out on a long road trip. :M