Frozen battery cells

[Gjac]

My MH has been in MT for 3 mos(another thread) I asked the shop to charge the batteries because they sat so long over the summer since July. Apparently the charged the chassis battery but not the house batteries. Last week I flew out to MT to drive the MH home and checked the the batteries the chassis battery was at 90 percent SOC and the house batteries were at 30 percent. I started charging with my 40 amp B&D charger and got an error message of a shorted cell. When I looked inside the caps there was a slushy ice formation inside, so I reduced the amps to 10, charged for a while then charged at 40 amps all night. No error message. My distilled water was frozen solid so added tap water to top of cells. It was very cold ride all the way home and batteries continued charging for 2000 miles while driving. They are holding a charge for the last 5 days. I will try an equalization before winter in CT sets in. Do you think partially frozen cells do any permanent damage the batteries? These are 2 6V GC Sam's Club batteries.

[time2roll]

Just saying I would not just arbitrarily leave an AGM out in the snow all winter because freezing is harmless. Of course freezing for water is usually different than freezing a battery.

Is my propane frozen yet? There is frost on the outside of the cylinder...

[MEXICOWANDERER]

[full_mosey]

time2roll wrote:

full_mosey wrote:
AGMs are not like that. They can freeze without damage. They can be thawed and then charged.

OK you might get away with a light freeze a couple times however I would not count on doing this on a regular basis.
More resilient to some freezing but hardly damage proof from freezing.

Is a light freeze like being a little bit pregnant? 🙂

I don't have any experience with a frozen AGM. IIRC, there has never been a post here re a frozen AGM. I do recall reading somewhere on the procedure though.

Based on MEX's post I would say it is less likely for a severely discharged AGM to freeze while alongside a fully charged frozen FLA. There are plenty of posts re frozen or slushy FLAs. I am guessing that if you found frozen FLAs then the AGMs would be fine. If you find a frozen AGM, you better be wearing your sweater!

HTH;
John

[MEXICOWANDERER]

AGM is a funny animal. Even when discharged to 8-volts, the saturated mat still contains acid in the 1.180 - 1.190 range. Why? AGM batteries start out with a 1.300 electrolyte density and fall on their face with a denser gravity than a flooded battery.

I would not like to experience a day that could freeze an AGM battery even when the battery has been reasonably flattened. "Reasonably" means a constant load has not existed for weeks utterly exhausting the battery.

Internal plate (grid) and separator structure of a quality GC battery is far stronger than it is for a car jar battery. Meaning the plates are more bend resistant. But this increased strength only goes so far. It should not be construed as any type of "advantage" but rather as a reason why golf car batteries seem to survive freezes "better" than a car jar RV battery. But please don't extrapolate this as being a tangible "advantage".

[time2roll]

full_mosey wrote:
AGMs are not like that. They can freeze without damage. They can be thawed and then charged.

OK you might get away with a light freeze a couple times however I would not count on doing this on a regular basis.
More resilient to some freezing but hardly damage proof from freezing.

[Gjac]

red31 wrote:
page 3 chart shows DOD ~ 60% just below zero F

https://www.cdtechno.com/pdf/ref/41_7953_0112.pdf

Thanks for posting this. It shows that at 30% SOC the cells will start to freeze at 10 degrees F but even if your batteries drop to 70% SOC over the winter storage you are good to -50 degrees F.

[red31]

page 3 chart shows DOD ~ 60% just below zero F

https://www.cdtechno.com/pdf/ref/41_7953_0112.pdf

[Gjac]

Sounds like the consensus is a hard freeze is damaging but slush formed in the cells is recoverable. Like I said in my OP I will equalize before really cold weather sets in. They are still holding a charge after 2 weeks with no load. Will see if I get another year out of them next season. This was the first time batteries ever dropped below 50% SOC. There must be some kind of chart that shows at what SOC and temperate ice begins to form in cells, just have not seen one.

[full_mosey]

eHoefler wrote:
Your batteries are junk. Never try to charge batteries that are frozen or have been frozen then thawed. They can and will explode! I have had 4 batteries explode on me over the years working in class 7 & 8 truck. Replace them!!

AGMs are not like that. They can freeze without damage. They can be thawed and then charged.

I don't know how you are supposed to tell that they are frozen as they are sealed. I doubt you could observe any swelling as there is not much liquid in there and what there is, is absorbed. Probably a pint per gallon of liquid compared to FLA.

I guess an IR gun would help or you may have the type of charger that uses a temp sensor cable. My solar controller system records battery temp at one minute intervals.

HTH;
John

[Matt_Colie]

If your house bank has been successfully charged and they are nine years old, put her up carefully (it will be winter in CT soon enough) and see what they are like next year. I would bet that they behave like 9yo batteries.

Matt

[eHoefler]

Your batteries are junk. Never try to charge batteries that are frozen or have been frozen then thawed. They can and will explode! I have had 4 batteries explode on me over the years working in class 7 & 8 truck. Replace them!!

[BMCM]

Dennis12 wrote:
You should never put frozen water in a battery. It says so right in the manual.

Say what?

[36guy]

Well, I'm 62, been rv'ing for forty years, building hot rods more than forty years and have NEVER added distilled water to a battery, always tap water, sometimes creek water. The 6 volt batteries in my fifth are ten years old this year and probably have seen their day, but the first trip out will determine that. Regular maintenance is the key to battery life.

[Gjac]

Bill.Satellite wrote:
Tap water bad! You would not have to have driven very far to find some distilled water. If I am wrong about that then you did a good thing to get you where you needed to go but don't start a new thread in the future about your batteries not lasting as long as they should have.

Wow, not a lot of stores open at 10 PM in Mt. to drive to and buy distilled water after dark in the snow. I have treated my batteries well, they are 9 years old I figured topping off with tap water one time is better than no water as someone else posted. I wanted to charge the batteries overnight to keep the cells from freezing solid and really doing damage, the overnight temperatures were 4 degrees.