Battery Voltage Question

[Jsmth86]

It is around 40 degrees for a high today and when cruising in the golf cart about 30 min into my drive (5-6 miles) the cart was acting like the battery voltage was low. I have a battery meter (bar type) on the cart and I know it’s not the best it gives me an idea of where I am at and it showed that I was under 1/2 charge. I went straight back to my campsite and got out my volt meter and it read at 48.8V. After testing each of the 6 batteries none tested below 8.7v.

I plugged into my Lester charger and it said I was at 18% of charge. After unplugging and plugging back in it then said I was at 94% charged. I left the battery pack charging for another hour and retested the pack and it is now at 50.6v.

Any idea what is going on here? Do you think my battery pack is bad, bad battery or just acting crazy with the colder weather? I have 6-8v Duracell batteries that are about 14 months old.

Thanks for the help!

[CP241]

Cold weather sucks.

This sounds about right. My cart is 4x12v. When it’s warm, under heavy acceleration it only drops to around 47v during load. I get 10+ miles easy on a charge and still have 70%+ state of charge remaining.

It’s cold now. Fresh off the charger it will drop to 45-46v under a load. After 2-3 miles it will drop down to 42-43v under load. (Though that is a pretty heavy load doing donuts in snow and all...) As soon as I stop it’s back up to 50+ after resting 5 minutes. Nothing else has changed, except the weather. Cold affects the chemical reaction within the batteries. This is why people’s car batteries much more frequently die in the winter than summer.

I wouldn’t fret it. Once it warms up they’ll go back to normal.

I’d highly recommend a digital voltage gauge. The “fuel” bars really don’t tell you anything. A voltage gauge giving live actual readings is much more helpful.

[CP241]

And as for plugging and unplugging and replugging the charger... the charger was prob more right the first time. When you plug it in and it starts charging, false voltage of the batteries will rise very rapidly because the charger is outputting pretty high. If you plug in the charger for 5 minutes and then remove it, it will initially show 50+ volts. But let it sit for a few hours and it will slowly drop back to about where it started.

If you plug it in for a few, unplug it and then plug it back in it is probably reading this false voltage and thinking they’re more charged than they really are.

[Jsmth86]

Thanks for the info. The initial test of 48.8v was at a 2min rest. I have a voltage meter however I don’t really have any place in the dash for it. I am thinking of mounting it near the f&r switch. The “fuel” gauge typically gives me a good estimate. And I carry a multimeter on the cart but for some reason left it back at the campsite.

[CP241]

I’ve always removed the bar meter (because it’s junk) and put the volt meter where the bar gauge was. Have to use a dremel and open it up slightly larger to accommodate the bigger gauge but that only takes a minute.

[kernal]

From the chart you can see the battery capacity is at least 20% lower due to temp alone. Timing is important when estimating battery capacity using voltage. It needs time to stabilize before readings are valid. Same with the charger app. It gives you a snap shot when you look at it so can be very misleading. I agree with CP. I don't think you have a battery or charger problem.

[CP241]

Originally Posted by kernal

From the chart you can see the battery capacity is at least 20% lower due to temp alone. Timing is important when estimating battery capacity using voltage. It needs time to stabilize before readings are valid. Same with the charger app. It gives you a snap shot when you look at it so can be very misleading. I agree with CP. I don't think you have a battery or charger problem.

I’ve never seen that chart before. That is great information.

Makes total sense why I went from great range to crap. At 0C it’s around 75% capacity right off the bat... and it acts like it!

[kernal]

The chart comes from the Trojan battery user guide: https://www.trojanbattery.com/pdf/Tr...UsersGuide.pdf

Although produced by Trojan, the guide would apply in general terms to all golf cart flooded batteries.

[CP241]

Originally Posted by kernal

The chart comes from the Trojan battery user guide: https://www.trojanbattery.com/pdf/Tr...UsersGuide.pdf

Although produced by Trojan, the guide would apply in general terms to all golf cart flooded batteries.

That chart rocks. Pretty much says it all. Thank you

[Fairtax4me]

Seems normal for cold weather operation, especially if the batteries are a few years old.

Cold slows down the process that allows the electron minions to run around in the battery. This happens with all batteries regardless of chemical composition. (Lead acid, lithium, nickel, alkaline, etc.)
It’s a chemical reaction, and the reaction slows down with a decrease in temperature. It’s an unfortunate side effect of any battery. It doesn’t necessarily mean the battery is bad, but it can reveal a battery that is having a capacity problem, or that is of a lower State Of Charge (SOC) than the others in the pack.

The best way to test the batteries is with them under load, and test each one individually to see if one has a lower voltage than the rest when under load.

Which Lester charger do you have?