Dropping Temperature / Performance decline

[MiltonC]

Low temperatures around here have been around freezing for the last few days.

I went out for a 2 mile drive this evening in my '08 RXV with the temp in the mid-40s. I could tell a definite decline in performance on the hills, although the top speed appeared to remain about the same.

Cleaned all the cables about 2-weeks ago and the battery pack voltage has been good when checked lately at 51.3 volts.

I have been charging the pack after every drive, and at least weekly.

My SOC shows a full charge is on the pack and it does not drop when the performance is slowed.

Is this decline in performance during the winter normal?

[kernal]

It has been my experience that when the temp gets colder battery performance degrades but mostly in range per charge. The included chart from Trojan supports my experience.

[JohnnieB]

Originally Posted by MiltonC

................
My SOC shows a full charge is on the pack and it does not drop when the performance is slowed.
..................

I suspect you have a LED Bar-graph type SOC meter.
A DVM type SOC meter will show the pack voltage drops further under load when cold.

Temperature does not effect the battery voltage, that is determined by the chemistry of the electrolyte and plates, but it does change the speed at witch the chemical reaction takes place.

The net results is that the battery's storage capacity is reduced by about 10% for each 20°F below 80°F.
Therefore, your T-1260 batteries that are rated at 140AH at 80°F are only 98AH batteries at 32°F and their voltage will drop further under the same load that was applied in warmer weather. Run-time will also be reduced by 30%, or more.

Please note that it is the internal temperature of the battery rather than ambient air temperature, that causes the change.
If the cart is kept in a heated garage, it will preform "normally" until the battery's innards cool off and considering the thermal mass of a lead-acid battery, that may take a while.

[MiltonC]

Thanks for the replies Kernal and Johnnie,

So I am a little confused. Here's what I think you guys are telling me.

Then the storage capacity of the battery pack at 32 deg F is ~25% less than at 80 deg F after a full charge and the waiting period.

Following this logic, the recommendation on other BGW threads to protect the batteries and make them last as long as possible is to avoid deep discharge and recharge at roughly a 20%-30% discharge but in no case over 50% if it can be avoided, or that is what I understand. Driving in colder weather, I am already at or below this level when I start off? Therefore, driving any significant distance in cold weather is limiting the cycle life of the battery pack.

To put it simply, driving my cart in the winter is reducing the cycle life of the batteries (harder on them) more than driving in the summer.

Or is there no difference, as long as I reduce the distance by 25% between recharges?

Options are:
1. Quit driving in cold weather
2. Store the cart a heated garage
3. Place a heating device under the battery pack (heat lamp etc) while outside.

At what point is the temperature too high for a battery pack?

I am using an EZGO SOC which looks like a gas gauge, but in effect I believe it functions the same as the LED bar type.

[kernal]

Yes, driving the same distance at 40° is discharging the batteries deeper than at 80° all else being equal. I use the led bar SOC meter that came on the cart (I'm the original owner). These type meters have a bad reputation on this board but mine is reasonably accurate when compared to a DVM and like yours doesn't cycle when under load. Sooooo, on cold days the meter drops faster over the same trip than on hot days. That is how see that the batteries have reduced capacity when cold. I understand your meter has a different presentation and only has three graduations full, half and empty I believe but it works same way----I think.
In the summer I can make about 18 miles without going below 40% discharge. With typical trips in the 8-10 mile distance I am not stressing batteries even on cold days.
Trojan produces a chart (which I can't find right now) which graphs battery life in cycles compared to percentage of discharge. Basically the chart shows that even discharging the batteries to 50% every day will still give several years of life assuming proper maintenance and charging procedures.
Check out the tech support section of the Trojan web site if you have some time to kill.

[MiltonC]

Originally Posted by kernal

Yes, driving the same distance at 40° is discharging the batteries deeper than at 80° all else being equal. I use the led bar SOC meter that came on the cart (I'm the original owner). These type meters have a bad reputation on this board but mine is reasonably accurate when compared to a DVM and like yours doesn't cycle when under load. Sooooo, on cold days the meter drops faster over the same trip than on hot days. That is how see that the batteries have reduced capacity when cold. I understand your meter has a different presentation and only has three graduations full, half and empty I believe but it works same way----I think.
In the summer I can make about 18 miles without going below 40% discharge. With typical trips in the 8-10 mile distance I am not stressing batteries even on cold days.
Trojan produces a chart (which I can't find right now) which graphs battery life in cycles compared to percentage of discharge. Basically the chart shows that even discharging the batteries to 50% every day will still give several years of life assuming proper maintenance and charging procedures.
Check out the tech support section of the Trojan web site if you have some time to kill.

Thinks for the education Kernal,

I get about the same distance from my cart during warm weather as you. I will just continue to charge the batteries after everytrip which is usually in the 2-8 mile range.

Based on a battery pack voltage check using charts supplied by JohnnieB and others on this forum my SOC meter has been pretty acurate.

If I am understanding, if the SOC meter is working correctly I should see the guage drop roughly 30% faster during cold weather. However, the initial voltage on the battery pack would be the same.

In simpler terms (if I am right), my cart goes from getting 18 mpg to 12 mpg although in both cases I am starting with a full tank. As long as I don't run the tank to less than 1/2 full, I am ok.

[yurtle]

Is you gauge an LED style, or does it have a needle? If it is the needle type (analogue), then you can use a marker and mark 100%, 90%, etc., based on actual readings from a DMM.

[MiltonC]

Originally Posted by yurtle

Is you gauge an LED style, or does it have a needle? If it is the needle type (analogue), then you can use a marker and mark 100%, 90%, etc., based on actual readings from a DMM.

It uses a needle. I've verified that the SOC gauge is pretty much in line with the battery discharge charts +/-.

[MiltonC]

Here's a picture of my SOC in the middle of the instrument panel.

[yurtle]

I've never seen an RXV. Now I know why you said it looked like a fuel gauge.