Batteries removed for winter or continuous charge?

[TimC]

Do you recommend removing batteries from your TD or RV in the winter AND why?

I have eight 18aHr AGM batteries in my TD. The last two winters I have left them in the TD and have them on continuous charge through an MPPT charge controller. Any real reason I should put them in a warm place? They are in their fifth year and have no trouble topping out at 13v +. I don't know if the capacity is reduced. I don't know how that is measured and don't have base data to compare to when they were new.

They are unlikely to freeze with a charge, correct? I am finding lots of conflicting information about cold storage of batteries. Some are saying I am killing my batteries, others are saying just keep them on a charge and no harm will be done.

[John61CT]

Either way is fine.

Personally I think it is best to leave valuable banks completely isolated.

Then top them up overnight every so often

How often depends on their self-discharge rate and how extreme you coddle them in general

but at least every six weeks.

[saltydawg]

I think the general thought is give them a charge once a month for a day, with a charger that is low amp like a battery tender. The theory is trying to constantly push a charge that is larger than the the self charge can drive electrolyte out ( boil water off ) but that is less of a problem for agm. Your existing mppt should be fine, just hook it up/turn it on one day a month and thats enough to keep them topped up.

[John61CT]

AGM have more of a problem if you vent electrolytic vapor, early death results if a regular event.

FLA has no such issue long as you keep the water topped up.

Of course a proper voltage setpoint is critical, low end of the range spec'd for Float by the mfg datasheet.

A super-high current charger is no problem, just use the one you usually do if it is high quality, adjustable setpoint is critical IMO.

[tony.latham]

AGM have more of a problem if you vent electrolytic vapor...

And how do you do that with a sealed battery?

Tony

[John61CT]

AGM have more of a problem if you vent electrolytic vapor...

And how do you do that with a sealed battery?

Just by overcharging, too high a voltage for too long a time period.

Some poor quality SLA are indeed truly sealed.

But AGM and GEL are within the VRLA subset, and indeed do vent when overcharged.

That is one reason why they rarely last as long as quality FLA, the owner needs to be much more meticulous about care, requires more precision, a narrower window of V&A in order to get good longevity.

[saltydawg]

As much as it pains me, to kind of agree with John.

Agm batteries do have vents, but they are more of an over pressure release so they dont pop. You can over charge a sealed battery to the point where it vents but that means the charger is broken, ie putting out 16 or higher voltage or holding 14+ volts for a long float charge.

Now using the wrong type of charger is bad too, you dont want a constant current charger. But for the most part any lead acid charger is fine for any lead acid battery even agm as long as you dont keep it on float for more than a few hours. If the charger has a agm mode, it will turn the float charge to the point where the agm is fine.

But for the most part, put it away charged, and give it a 24 hour charge once a month.

https://www.centurybatteries.com.au/con ... arging.pdf

[tony.latham]

I'm not sure how this post ran off into the Netherlands that overcharging a battery is harmful.



T

[TimC]

Thanks everybody.

I've processed all that and come to the conclusion that it will be OK to leave my batteries out in the cold (Avg. Jan temps 25f, lows occasionally to -25, rarely -40) hooked up to my MPPT charge controller and my 100W panel and letting that maintain the proper charge level without fear of freezing. This will be their third winter stored like this and I have had no problems so far.

[saltydawg]

I'm not sure how this post ran off into the Netherlands that overcharging a battery is harmful.



T

Are you saying that its not or how did the thread drift?

If for the thread drift, it was a you dont need to keep it charging all the time, because it can cause over charging if the charger cant provide a low enough voltage and current or is having an issue ie broke.

[RJ Howell]

I'm an old LA guy that has gone LiFePo. My battery comes out during the winter so I can use it as a UPS or backup when (not if) power goes out.

My old LA's lasted 18yrs by simply applying an old adage of 'use them and they will survive'. I always had a low (tender) watt charger hooked up and had a low (USB fan) running. I'd shut down the charger when full and let it draw a bit, then run the charger again. Also use my solar panel for a bit but was a PITA with the snow we get.. Now I did have meters set up to see my voltage levels and know not to draw them down to far. Cycle numbers change according to level o discharge.

Balance out what AGM's can do against what I've done with my LA's. I would 'think' the same principle applies, yet I'm not an AGM guy...

[Shadow Catcher]

For twelve years I have brought the 150 AH Lifeline AGM to 100% SOC and every month or so plug in the solar for a day or so. Once the snow is off the panel.

[GuitarPhotog]

My teardrop is plugged in 24/7/365. I have a PD4045 charging a 60AH AGM battery. So far the battery has lasted 5 years under this discipline. The previous battery (also AGM) lasted only 4 years, but it was accidentaly discharged down to zero twice.

I'm in So. Oregon, so we don't get a lot of snow, or hard cold weather, and the TD is in a carport for protection.



<Chas>

[Squigie]

As mentioned elsewhere recently, I bring mine into the garage and trickle charge. (Solar panel in the window for the deep cycle, plug-in for the automotive types. And they're checked every 4-6 weeks, or so.)

We are pretty much guaranteed to see -20 F for a day or two, more than once per winter, with at least a few weeks with high temperatures below zero.
Though I have never had a charged battery freeze in those temps, I have lost two batteries that had been neglected and allowed to drop below 9 V. One was damaged internally when it froze. The other actually cracked the case and leaked everywhere once it thawed.

Though I've had good luck when keeping the batteries charged, I'd still rather bring them into the garage for the slightly warmer temperature (10-15 degrees), just in case I forget to check on them for a while.

[John61CT]

I agree such extreme temps should be avoided when practical. Note that a fully charged battery is susceptible to being damaged at much lower temps than a depleted one.

But letting a lead battery sit below 100% Full is inherently life-shortening

even for just a few days, and more so in warm / hot weather.

A constant trickle charge is very very trusting of your source gear's reliability, overcharging can murder batts **very** quickly.

If it isn't inconvenient to regularly "check in" then leaving isolated the rest of the time is safer.