How Harsh is Cold Weather on Batteries?

[harriswallace]

Good to know about the cold. I was thinking I had a bad battery or the full windshield i just put on had something too do with it . I start off at about 78 volts and 100% all batteries read 8.7 or 8.6. On a hard acceleration pack voltage drops as low as 51volts but comes right back to 78volts after stop which drops the percent meter down to 75%. my range seem to bee shorter also and no where as peppy and takes a lot longer too get to top speeds. Man can’t wait till this cold is over.

Eddie

[NCPW]

I believe it was JohnnieB who has posted charts that explain the effects of temperature on FLA battery performance. Maybe you could do a search for it or he'll chime in.

[Mooncarter]

Originally Posted by NCPW

I believe it was JohnnieB who has posted charts that explain the effects of temperature on FLA battery performance. Maybe you could do a search for it or he'll chime in.

[ThreeCW]

Here is the graph posted by CGTECH that shows battery performance vs temperature. I am not sure where it is sourced from but you can find more some more information by reading this thread: http://www.buggiesgonewild.com/elect...tric-cart.html

As you can see on the graph, at -10 C (14 F), your batteries only have about 55% of their normal capacity ... hence why your cart could have been feeling a little "sluggish". Normal capacity rating (100%) occurs at a temperature of 25 C (77 F).

[kernal]

Here is the chart from Trojan. It's a little simpler so my stupid brain can understand.

[BGoat]

So what the charts are saying, if your batteries are at 20 degrees, and are measuring 75% by voltage or specific gravity, they should be 100% at 80 degrees, therefore, they should be considered good?

[kernal]

Originally Posted by BGoat

So what the charts are saying, if your batteries are at 20 degrees, and are measuring 75% by voltage or specific gravity, they should be 100% at 80 degrees, therefore, they should be considered good?

No, might be true but I don't think you can assume that. Resting voltage is only one measure of battery health and has to be measured under consistent parameters to be of any value. Bad batteries can have normal resting voltage . Voltage drop under load and over time is a better measure of battery health.
I think what you CAN say is your batteries MAY be OK if the resting voltage is showing only 75% charged but they have been exposed to very cold temps for an extended time period. Also, if they have been just sitting, normal self discharge 1%-4% per week could account for this.

So, in the real world, this is how the reduction in capacity shows up in daily operations for me. The resting voltage of my carts remain pretty consistent when fully charged whether summer or winter (Atlanta). In the winter, 50-60°, the battery SOC drops faster over the same distance than it does in the summer, thus demonstrating the reduction in capacity due to temperature.

[Sergio]

Not at all, the effects of temperature are on the "capacity/performance" not the charge.

If you have a temperature adjusted hydrometer, You should still measure the correct specific gravity since it adjusts for the differences in the chemicals density caused by the cold temperature.

As You know, batteries do not store electricity, they store the chemical elements needed to produce electricity.

As the temperature drops, those chemical reactions slow down and are less efficient.

That causes lead-acid batteries in storage to have a very low "self-discharge" at cold temperatures since the reactions are much slower than at 80F.

Unfortunately that also causes the battery to either not be able to deliver the current being demanded due to the inability to create the necessary chemical reaction rate, or the "surface charge" will drop as a result of that inability.

As the temperature inside the battery rises, it can again perform its chemical reaction efficiently and deliver the rated capacity.

The same way the "peukert effect" causes the battery to deliver less than its rated capacity of 20 Hours as the discharge current increases, lowering the internal battery temperature will also cause it to deliver less than the rated capacity.

Edit: Kernal, I was replying to BGoat post, just took me a while to put my thoughts together...

[BGoat]

The reason I was asking is that 12 to 16 hours after my charger shuts off during this 20 degree weather, pack voltage is showing 75% charge and temperature compensated specifc gravities show the same. I was just trying to figure out if my batteries are any good or not. I still don't really know.

Specific gravities are pretty even.

[Sergio]

What kind of charger are You using?

The slow chemical reaction at lower temperatures also affects the charging efficiency, according to Trojan:

For every 1º F below 77º F add 0.0028 volts per cell for charging

So at 20ºF, the normal 59.3v @ 77º F bulk charge for 24 cells should reach:

59.3 + (77-20) * 0.0028 * 24 = 63.13v

Trojan keeps mixing 77º F vs 80º F in different articles, so it is not a precise science.

You can measure the voltage near the end of the charging cycle (while still charging) to make sure the charger is raising the voltage to an acceptable level, but Your batteries may be bad.