Charging and discharging in cold temperatures

[Dayrobber]

Feb,mar.june 2019. Southern California desert. Definitely no ruff handling. Don't know if I mentioned the white is baking soda. No corrosion, just cleaning with water and BS. Strange all the terminals are coming loose then iut if there settings.

[Mike90250]

Seams pulling apart like that makes me think rough handling or maybe freeze damage. How old are those ?

[Dayrobber]

The white stuff is baking soda from cleaning. That's when I notice the seperation at the seams. They're not uniform all around.

[Dayrobber]

Here's a link.https://photos.app.goo.gl/98F2Lhp4oo4GdAa67

[Dayrobber]

It does,and I leave it alone. Curious that's all. But those batteries just this morning. Actually just finishing up now. Everstart 24dc. During cleaning noticed all threaded bolt on terminals were moving/wiggling so to speak. Further inspection, batteries are seperating on casing tops. I might not have a $1000 CC. But I have a good MPPT. Cables never hot. Cables are 2awg. These batteries were bought 2 in feb.19. 2 in mar 19.
WT FertiliFertilizer is up?. I already ordered new batteries. AGM. Is there a way to post a pic. on here?

[Mike90250]

If you can't find anyting specific for your batteries, then I would enable the proper charging mode (generic FLA, AGM or GEL) and enable temp comp. Most good controllers have a remote BTS to insure accurate Battery Temperature Sensing

[Dayrobber]

MPPT is programmable. Just don't know wgat 12v everstart batts rv/marine should be set at.
Nothing on the website, or searches.

[Mike90250]

Higher temps usually indicate lower charging voltages. Most modern Charge controllers have a setting or a way to configure automatic temperature compensation. Keep using them till they fail the warranty capacity test. If you can't adjust or configure your controller, you will continue to have this problem with any battery

[Dayrobber]

I'm asking because I know that figuring temperature compensation coefficient values are over my head. It's been a 118 Fahrenheit for over a month. My 5 month old 4 100ah everstart 24dc mar.rv batteries are dying. I have 4 cloudy cells,(weird all in the same cells)and with the temps. being what they are should I adjust the values? If so,what to? The batteries are still under warrenty so I'll take them back. Kick them to the 12v system. Then continue the 24v setup with what I've learned from those mistakes. Thanks. Later.

[Higher Voltage]

Thanks everyone. I do care about the batteries but safety first.I wish I could bring them in my basement but I worry about the what ifs. Im not home all the time and I have a child. The batteries are from 2015 out of a ups unit . I am now cycling the hell out of them,but not deep discharge, and there not much I can do. I dont think Ive been below 49v under load,2500w. My midnight state of charge meter has never been in the red or yellow. Its -9 C now they still work.Did I mention I got 50 for free. Really I could never afford to buy these new and if I could I wouldnt. Probably go with Li Po.But I really appreciate all the help.

[PNjunction]

If you care about your batteries, you won't wing-it with manual temperature compensation adjustments, but use a controller with a temp-sense wire attached to the battery instead.

The lead in batteries don't react quickly to ambient temperature changes, so it is best to automate this if your batteries are not in a temperature-controlled environment. Simple manual adjustments for temperature can lead to under / overcharge as the battery is slowly ramping up or down in temperature.

[BackwoodsEE]

Im in CAN. We are in the minuses now. As low as -12 C.I am also 48v. I still use a 24 cell set up for voltage but I am running 48 12v ups batteries. C&D Tech.UPS12-300MR. Not my preference but I paid almost nothing so I cant complain. I dont have a BTS for my controller, which I should have. I guess for me it is a money thing. So for me at -5 we are : 30x.096=2.88+56.8=59.68V. Is this correct? My inverter does not like the higher voltages . Thanks for the math lesson.Ill see if I can find the temp.comp. for my batteries.

A quick look through your battery's manual didn't reveal anything about temperature compensation, but they recommend the same float voltage as for mine: between 2.25 and 2.30 V per cell. That works out to 54.6 V in the middle of that range, for float service. The "freshening charge" they recommend (clearly only intending these for backup usage) works out to 57.6 V for your battery bank.

Assuming your batteries (also AGM) would also use the -0.004 V/degree/cell temperature compensation, yes, your adjustment would be the same. Say your average battery temp is -6 C, or 31 C below the standard room temperature for which battery charging parameters are published. You would add +3 V to these numbers: "Freshening charge" at 60.6 V and float at 57.6 V. Or, using the 56.8 V figure you cite, 59.8 V instead.

The temp sensor should be taped securely to the side of a battery in the middle of your battery bank, about halfway up. Don't use double-stick foam or anything that puts thermal insulation between the battery and the sensor.

Remember, these are UPS batteries and are best used for float service without much cycling.

[Higher Voltage]

If I were to get a BTS ,where would be the best place to install?

[Higher Voltage]

Im in CAN. We are in the minuses now. As low as -12 C.I am also 48v. I still use a 24 cell set up for voltage but I am running 48 12v ups batteries. C&D Tech.UPS12-300MR. Not my preference but I paid almost nothing so I cant complain. I dont have a BTS for my controller, which I should have. I guess for me it is a money thing. So for me at -5 we are : 30x.096=2.88+56.8=59.68V. Is this correct? My inverter does not like the higher voltages . Thanks for the math lesson.Ill see if I can find the temp.comp. for my batteries.

[BackwoodsEE]

As an example, Rolls-Surrette recommends a temperature compensation of -0.004 V per degree C per cell for its AGMs. For my 48V battery made up of 24 cells (eight S6-460 6V batteries made up of three cells each), that works out to 0.096 V/deg C.

Right now on this winter morning in WA, the battery is 4 degrees C, so the increase in voltage set points is (25-4)*0.096 = +2.016 V.

Unfortunately, my Outback Radian seems to have a fixed "one size fits all" temp comp coefficient of -0.005 V/deg/cell, which means I will have to change the charging set points somewhat depending on the average battery temperature. Come summer when the battery temperature is averaging 27 degrees C, the wintertime set points will be about half a volt too low. Probably not a big deal, and the numbers would still be well within Rolls's range of acceptable charging voltage values.