Ah meter?

[sleepyluke]

Ok, I have learned that very cold and older batteries is not a good combo and it sucks the juice out of them very quickly. I have a digital voltmeter ready to be installed maybe this weekend, but the cold affects the Ah as I understand it basically sucking power and run time. I have seen a few Ah meters online that appear to not be a viable option, and I can not quantum physics in my head like JohnnieB to calculate, but if there is a basic calculation, or meter, i may be interested.

I understand that it is roughly a 10% per 15 degree or 20% per 20 degree drop depending on which chart you look at, but is that literally power, mileage, both? And at what point do you stop, 50% like volt drop?

I know I am overthinking it, but i very much do not want to walk home in the cold! So far I have not gotten myself stranded, but the cart was definitely slower on the trip home, less than a mile round trip, but sat for 3 hours in between in 25 degrees.

Thanks

[JohnnieB]

It is the AH capacity of the battery that shrinks as they get colder, so an Amp-Hour meter won't tell you much more than the Voltmeter you already have will when you get it installed.

Shrunken storage (AH) capacity reduces both range (run-time) and performance. In a nutshell, your cart won't go as fast, slows down more going uphill and won't go as far when it is cold.

However, the At-Rest voltage readings will be the same. So you can estimate the you battery pack's Soc (State of Charge) using the same chart you do in warmer weather.

Also, how far the Under-Load voltage can drop to stays the same.

Basically, in cold weather, you have effectively removed the summer batteries and installed smaller batteries. How much smaller depends on how much less than 80°F the temperature is.

Using a new, broken-in, T-105 as an example, its storage capacity at different temperatures is:
80°F = 225AH
65°F = 203AH
50°F = 180AH
35°F = 158AH
20°F = 135AH
5°F = 113AH
-10°F = 90AH

The AH used per mile by your cart will stay about the same, so the range decreases about 10% for each 15°F below 80°F and it may be worse with older batteries.

[simple man]

I thought that the batteries warm up when being used. Is this a faulty assumption? I do know they are warmed up by charging. How much with either scenario would only be a guess.
This should increase the run time, but like I said, it would only be a guess as to how much!

[Volt_Ampere]

They warm some when being used but they do that in the summer too. Rating drops and internal impedance goes up in cold weather. This reduces range and torque.

[kellybell]

That's why carting is so popular in Florida.......

[JohnnieB]

Originally Posted by simple man

I thought that the batteries warm up when being used. Is this a faulty assumption? I do know they are warmed up by charging. How much with either scenario would only be a guess.
This should increase the run time, but like I said, it would only be a guess as to how much!

They do gain some heat while being discharged, both by the chemical reaction that is occurring during discharge and by the current flow through their internal resistance, but it is only a few hundred calories per Amp of current flow and there's about four hundred pounds of batteries, so the temperature rise probable won't be much.

It takes one BTU to raise the temperature of 1Lb of water 1°F and if the battery pack was all water, (which it isn't), it would take 1,511,970 calories to increase the storage capacity by 10%. (Lead, sulfuric acid and plastic are denser than water, so the number of calories actually needed would be much higher.)

There are more things causing heat when charging, so battery heating is more pronounced while charging.

[simple man]

Thanks, John! If anyone knew this, I knew it would be you!!!

[yurtle]

Not trying to highjack, but I've always wondered if a 36 or 48 volt heater would offer more increased capacity than the juice used to run it. If you have a float charger, they'd always be warm, but once you're on the road, a heater could keep them warm. This would only work if the gain in Amp-Hr is greater than the loss in SOC due to the heater.

Lotsa variables involved, such as are you running constantly, or parking for hours between runs.

[sleepyluke]

Thanks for the breakdown. So I know it is personal choice, but when do you know it is time to replace batteries, when it really drops off in the cold, seemingly more than the chart calculations say it should? Or whole mother topic?! I am losing more run time than calculated but I have 4 year old batts that I have no clue how well they were treated until a year ago when I got it.

Thanks again for helping the dummy! this may be why I have always owned gas carts till now......but I am loving the learning and the challenges of electrics.

[JohnnieB]

Originally Posted by yurtle

Not trying to highjack, but I've always wondered if a 36 or 48 volt heater would offer more increased capacity than the juice used to run it. If you have a float charger, they'd always be warm, but once you're on the road, a heater could keep them warm. This would only work if the gain in Amp-Hr is greater than the loss in SOC due to the heater.

Lotsa variables involved, such as are you running constantly, or parking for hours between runs.

A cold battery already has a reduced storage capacity, so I'm not sure if using more energy from it would be a good idea or not.
Maybe an auxiliary battery or two stashed in the bagwell could be used instead of the main pack.

I've never checked to see how much heating float charging generates, or discharge does. Looks like my To-Do list got longer.