charging frozen batteries

westcoastslider · December 2009

I have read that lead acid batteries should never be charged when they are frozen.

I have 4 T-605's that are stacked tight against each other and I have one inch of foam insulation around them. They are in a exterior battery bay that is not heated. I have been fine until recently it's been well below freezing for several days and will be several more before it warms up.

Not knowing how cold they where I tried to charge them with the xantrex inverter. The charger went straight from BULK to FLOAT and skipped the ABSORB stage. I tried several times and got the same result. I shot the battery terminal with a non contact thermometer and it said 27*F. I assume the batteries wouldn't charge properly because they are frozen.

The batteries where at 12.2V when I tried to charge them. How bad did I hurt the batteries?

What to do from here? I was thinking about bringing the batteries in until they warm up to 40*F and trying to charge them again.

How do you keep a exterior ventilated battery bay warm when it's this cold out?

Did anyone else wake up to frozen pipes this morning:grr I'm heading for Mexico next winter:cool:

GreenPowerManiac · December 2009

Re: charging frozen batteries

Doesn't sound good. 12.2 volts means around 20-30% charge, if that. Frozen temps kill the electrolyte when voltage is low like this. Providing the plates where not damaged too bad, an electrolyte replacement may be in order. I'm sure you'll get plenty of opinions/suggestions, but in the mean time, get them batteries to someplace warmer than freezing.

All you can do is bring the batteries into a warmer environment (above freezing) and try to charge them. Good luck and let us know what happens.

BB. · December 2009

Re: charging frozen batteries

Be careful when you bring them in... A frozen battery can have its case cracked and when thawed, the electrolyte will drain out.

If the batteries were that discharged such that they can freeze at 27F--then they where near dead and my have sulfated/failed from being stored at less than ~75% State of Charge for a long time.

A 40% State of Charge battery should freeze around -16F. Either your battery is near 0% SOC, or you have some other issue (poor electrical connections, failed cell, failed controller, or something else).

-Bill

mike95490 · December 2009

Re: charging frozen batteries

If the batteries are at +27F, and have any charge on them, they are likely not frozen.

BUT you might have one cell that is weak, and one cell in a bank could be frozen. When was the last time they were charged, and last equalized ?

http://www.windsun.com/Batteries/Battery_FAQ.htm

Do you have a remote temperature sensor for your batteries, so the charge controller knows what the battery temp is ?

If your batteries are in cases, you could try adding warm water to the spillage area, and see if that warms them up enough. Or get a glass thermometer, and actually dip it into a cell. Or just open a cap, and peek into the cell with a flashlight, if you see fluid, all should be fine.

westcoastslider wrote: »

I have read that lead acid batteries should never be charged when they are frozen.

I have 4 T-605's that are stacked tight against each other and I have one inch of foam insulation around them. They are in a exterior battery bay that is not heated. I have been fine until recently it's been well below freezing for several days and will be several more before it warms up.

Not knowing how cold they where I tried to charge them with the xantrex inverter. The charger went straight from BULK to FLOAT and skipped the ABSORB stage. I tried several times and got the same result. I shot the battery terminal with a non contact thermometer and it said 27*F. I assume the batteries wouldn't charge properly because they are frozen.

The batteries where at 12.2V when I tried to charge them. How bad did I hurt the batteries?

What to do from here? I was thinking about bringing the batteries in until they warm up to 40*F and trying to charge them again.

How do you keep a exterior ventilated battery bay warm when it's this cold out?

Did anyone else wake up to frozen pipes this morning:grr I'm heading for Mexico next winter:cool:

Windsun · December 2009

Re: charging frozen batteries

Batteries would have to be at zero charge - 10 volts or so - to freeze at 27 degrees. So either it got a lot colder than you think, or there is something else wrong with the batteries.

icarus · December 2009

Re: charging frozen batteries

If they have been on some solar charge, or if they were left fully charged, it is possible that they are fully charged already, hence going from bulk to float without absorb. If you have a battery temperature sensor, it may be telling the charger to ramp down the charge current.

A battery with anything but pure water in it won't freeze at 27f. 50% charge won't freeze until nearly -20, fully charged won't freeze until well below -50f.

Check each cell with a hydrometer or volt meter.

Tony

Ps, we routinely leave batteries over the winter @ -40 with out trouble.

Second, don't charge a frozen battery,,, but I don't think yours are frozen.

westcoastslider · December 2009

Re: charging frozen batteries

OK sorry for the confusion. I'm really new to all this. A quick visual check showed that none of the cells where actually frozen. I didn't know electrolyte had a lower freezing point than water.

Doesn't sound good. 12.2 volts means around 20-30% charge, if that.

The voltage charts I have seen say 12.2v = 60% and 11.6v = 20% No charge or discharge for 6 hours.

No battery temp sensor on the batteries.

The batteries are drawn down to 12.4v on a daily basis and recharged by the panels. If I get no sun I'll let it go to 12.0v before starting the generator to recharge. They never sit below 12.0v. Last EQ (which was the first time ever for some two year old batteries) was two weeks ago.

Why do you think the charger skipped the ABSORB stage? I know I didn't get a good charge on them.

If I maintain a good charge is it safe to leave them outside? High of 18*f today and back down to 0*f tonight.

mike95490 · December 2009

Re: charging frozen batteries

Battery voltage changes as the temps change, and that can be fooling your charge controller. You NEED a remote temp sensor to properly charge your batteries.

Cariboocoot · December 2009

Re: charging frozen batteries

You can also put a load on them and see if they 'behave'. Sometimes you have to draw a battery down a bit before you can charge it up.

Trick for automotive charging. Really dead batteries won't draw current from automatic chargers, so hook up the charger and turn the lights on so that the charger starts producing current, then turn them off. It'll drop back to zero, but then will start slowly charging up. This is because of the charger, though; not the batteries.

BB. · December 2009

Re: charging frozen batteries

Cold batteries need a higher charging voltage (one reason a Remote Battery Temperature Senor can help in cold weather).

Measuring battery voltage for state of charge is only accurate if the battery has sat for 3 hour or so.

Have you done a temperature corrected specific gravity measurement of all your cells yet?

-Bill

icarus · December 2009

Re: charging frozen batteries

On a side note,,,,

I think that if you are routinely drawing them down to 12.0, I think you are drawing them down to far. 12.0 is about 45% depending on temperature. Most folks don't recommend drawing down to a max of 50%, and then getting them back to 100% as soon as possible. Personally, I prefer to only draw down 20%.

Batteries that sit for more than a day or two at 50-80% soc are just asking for sulphation.

If you haven't read these yet I suggest that you read: http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
http://www.batteryfaq.org/

Tony

As for leaving them out side, IF they are kept fully charged, a battery in a box outside will be fine. Think of it this way. Your automobile battery rides around in the un-heated, subject to slipstream engine compartment, subject to cold temps and they do fine. -40 or even -50 in the north is not unheard of and our vehicles have lead acid batteries. (getting them started is another issue, preheat, block heaters, 0w5 oil etc).

hillbilly · December 2009

Re: charging frozen batteries

icarus wrote: »

On a side note,,,,

I think that if you are routinely drawing them down to 12.0, I think you are drawing them down to far. 12.0 is about 45% depending on temperature.

Actually, that may not be so. To the OP, are you talking about 12V under load or at rest? I would assume that you mean under load since you mention 12V as the lowest voltage. In which case it's tougher to tell what the actual SOC might be. If the batteries are getting down to a low of 12V under say a C/20 load, that would put the SOC pretty close to 75% (roughly, depending on all conditions). A heavier load could pull the batteries down to 12V momentarily when they are at a much higher SOC...

icarus · December 2009

Re: charging frozen batteries

HB, Westcoatslider mentions in his post #7 about "no charge or discharge for 6 hours".

So I assume from that that he knows the difference. To your point however, battery state of charge is a tough nut to crack. Arriving at a absolute number is pretty hard, coming up with a "close enough" number is pretty easy if you pay attention to some parameters. (and have a good battery monitor).

Tony

westcoastslider · December 2009

Re: charging frozen batteries

Thanks for all the help. I think I was over reacting to the cold temps. This is my first winter off the grid and I'm still learning about solar power.

I did get some temp comensated SG readings before the EQ I have not checked them since.

1.22 1.23 1.23
6.40v
1.23 1.23 1.23
6.45v
1.24 1.26 1.24
6.41v
1.24 1.24 1.235
6.44v
The batteries where at 44*F SG is temp compensated but voltage is not.

I rarely actually see 12.0v. We get a lot of sun and I'm very careful about power consumption when the sun is not out.

westcoastslider · December 2009

Re: charging frozen batteries

So it's getting colder. -20*F the last two nights. Highs in the teens. The batteries are at 4*F this morning. Not having a battery temp sensor I was hoping to manual adjust voltage in the c-40 to compensate.

The Trojan web site called for the batteries at 80*F to absorb at 14.8v and float at 13.2v. That seems like a high absorb voltage and a low float voltage. Is that where you guys charge your Trojans?

They also mentioned that for every 10*F below 80*F the charge voltage should be .028v higher per cell.

So 80*F - 5*F= 75*F bellow standard charge temp
7.5 * 0.028 (higher voltage) * 6 (cells in a 12v bank)= 1.26v higher charge voltage at 5*F

Starting at 14.8 and adding 1.26 gives me a absorb at 16.06v and float would be 14.46v.

The c-40 can only go up to 15v for absorb and 14.5v float. So I have the voltage maxed out on the controller and I'm hoping for the best.

I see a battery temp sensor for both the c-40 and the 2012 in the near future.

mike95490 · December 2009

Re: charging frozen batteries

westcoastslider wrote: »

...
Starting at 14.8 and adding 1.26 gives me a absorb at 16.06v and float would be 14.46v.

The c-40 can only go up to 15v for absorb and 14.5v float. So I have the voltage maxed out on the controller and I'm hoping for the best.

I see a battery temp sensor for both the c-40 and the 2012 in the near future.

Make sure your meter that you are using, is "spot-on"

What's the acceptable range that the BTS is usable for ? If you can't manually adjust - can the automatics exceed that?

So what would average Joes like us, have around the house, that could be used to verify a DVM voltage calib ? Any standard voltage charts for a fresh alkaline battery at 70F ? a cheapo car battery maintainer with 30 PV cells ?

EQ a 12V (or 48V) battery bank, wait 6 hours, and use that voltage as a cal reference ?

hillbilly · December 2009

Re: charging frozen batteries

Just a note regarding temperature compensation, was your calculation was for ambient temperature? It's better if you are going more on the temperature of the electrolyte, which tends to be a bit more moderate and will usually rise as the batteries become closer to fully charged. I've had some really cold batteries the last few mornings, but by mid afternoon the battery temp sensor (placed on the side of one battery right in the center of the pack) starts reading much closer to "normal" and the voltage compensation was not so far off. Yesterday for instance, in the morning the temp corrected voltage of my battery bank was 1.4V different, by the time they were in absorb they were more like 1V different, and by the end of absorb they were only about 0.8V different.
I do not have Trojan batteries, but I do charge my Surrette batteries up to 29.6V (14.8V for a 12V system) during the winter due to the shorter charging window. I also use a RTS for temp compensation, which I think is a better way to go about it; this also adjusts voltage when charging from the generator too.
BTW those voltage and SG readings seem a bit at odds, are you sure that they are both correct?

icarus · December 2009

Re: charging frozen batteries

I think that, regardless of the float voltage setting, you are failing to get the batteries any where near charged. Either you have to reduce your loading, or increase your charging. In the real world, I don't think you have to worry about absorb and float voltages UNTIL you routinely can get the batteries close to full anyways.

My hunch is that your batteries are beginning to be toast as a result of chronic undercharge/overdraw. What I would do first, is get them on a genny or grid power, get them fully charged both by voltage and by SG and then see where you are. I think you SG measurements are way to low.

Using in voltage as a measure of battery health is a bit like using body temperature. It may tell you that something is wrong, but it won't always. A battery that can show 12.6 volts on a volt meter, but can't light a light bulb an fool you into thinking it is a good/charged battery. Temp corrected SG is a much better indicator, but even that is only one indicator. SG/Voltage/load test etc in concert are the only mostly complete way of telling battery health.

Tony

westcoastslider · December 2009

Re: charging frozen batteries

Mike, I don't have a BTS. The c-40 can be manually adjusted to absorb from 13v-15v and float from 12.5v-14.5v. The voltage meter I am using seems to agree with the settings on the c-40.

Hillbilly, I was measure temp with a non contact temp sensor pointing it at the negative battery terminal. The temp gauge seems to be pretty accurate. I will keep an eye on the temp today and back it off if they warm up. They are forecasting a high of 17*F today. A BTS would be nice but I'm working with what got. I'm not sure those SG readings where accurate. I'll get the best charge I can on them and try again.

Icarus, I can reduce loads but the c-40 is the best thing I have for charging my batteries. I don't have a BTS on the xantrex 2012 or the control screen to tell it what voltage to charge at.

It's going to be really cold and sunny today. I will tell the c-40 to EQ and maybe I'll get close to correct charge voltage.

icarus · December 2009

Re: charging frozen batteries

Am I hearing you correctly that the ONLY way you have to charge is with the C-40?

No genny, no grid?

If that is the case, asking the C-40 to do an EQ charge is meaningless if the batteries are not fully charged to begin with. In case I am missing something, no matter how you tweek the controller(s) the reality is that you can only put as many amps into the battery as the PV will provide.

I may be missing something, but I still think your batteries are chronically undercharged/overdrawn and no matter how you adjust the Float/absorb voltage on the controller won't change that. Setting the Absorb voltage +16 vdc won't give the batteries one single more AH of charge, if the batteries can't get more than 14 vdc into them.

Please tell me what I am missing?

T

westcoastslider · December 2009

Re: charging frozen batteries

The c-40 isn't the only way I can charge. I have a genny and the xantrex 2012 has a 100 amp charger built in but I have no way of telling the 2012 how cold the batteries are. I have tried to charge with the 2012 and it immediately goes to float even if the batteries are down to 60% SOC. It has also spiked up to 20v while trying to charge. This leaves me with the c-40 being the BEST thing I have to charge with.

I'm not really hoping to get a good EQ out of the c-40 and the panels I have. I'm hoping to get closer to fully charged considering the temp of my batteries. I have been holding 15.8v for about three hours now. If I hadn't hit the EQ button I would have been sitting at 15.0v for the last three hours. My thinking is at the higher voltage I am putting more watt hours into the battery bank. Am I looking at this wrong?

Setting the Absorb voltage +16 vdc won't give the batteries one single more AH of charge, if the batteries can't get more than 14 vdc into them.

Can you explain this a little more? What do you mean by "can't get more than 14 vdc into them".

I understand that this is not the ideal situation but I'm on a limited budget with limited equipment. What do you suggest I do with the equipment I have?

icarus · December 2009

Re: charging frozen batteries

My point, however poorly stated, is that until the battery voltage climbs to the absorb/float voltage setting, it doesn't matter what that setting is. For example, if you have the absorb setting at 14.6, resetting it to 16.0 isn't going to put ah into the battery any faster. Clear as mud?

Tony

PS I haven't read too far back into the threads, but I would suggest that you check the SG of all the cells. It is possible that the temperature is masking a bad cell. I would also look at all the battery connections.

hillbilly · December 2009

Re: charging frozen batteries

20V from your Xantrex charger??? That does not sound good. I'd ask the dealer and/or Xantrex about that. I am afraid that I know nothing about that charger, so I really can't help... but I don't think that ever charging a 12V battery up to 20V is good. Was that 20V at the battery terminal?

mike95490 · December 2009

Re: charging frozen batteries

icarus wrote: »

..... For example, if you have the absorb setting at 14.6, resetting it to 16.0 isn't going to put ah into the battery any faster. Clear as mud? ...

Huh ?? If you have a 12V battery, full, and floating at 14.6, if you apply 16.0V it's going to start dumping amps into the battery, just like an EQ cycle would.
The battery is not likely to charge to 120%, but it will gas like mad.

icarus · December 2009

Re: charging frozen batteries

Mike,

My point was, if he didn't have the battery full and floating at 14.6 changing the CC float voltage is not going to get the battery to float voltage any faster. Like I said, I'm clear as mud to day. Too cold, waiting for freeze up. Currently -22.

Tony

charging frozen batteries

Comments

Categories