Batteries die off quick

[boandbabs]

I have a 36v EZ GO golf cart. I bought new batteries in January 2019, "US2000" batteries. These have a prorated 2 year warranty. These have worked great, getting 14 miles of driving on dirt, gravel & asphalt on each charge. Near the end of September it was like flipping a switch and now we can only get about 6 miles or maybe 20 to 30 minutes of riding time. The batteries are getting a full charge and the water has been correctly maintained, not too full of let to get to low. I checked each battery today with a battery tester that put load on the battery. All the batteries tested on the line between ok & weak. One battery tested in the middle of the weak section but not bad. What could cause this issue? It acks just like the battery pack is weak and not holding a charge. Thanks for all the great advice I'm sure I will receive.

[ThreeCW]

Originally Posted by boandbabs

These have worked great, getting 14 miles of driving on dirt, gravel & asphalt on each charge.

Do you charge your batteries after each use or wait until you have 14 miles on them?

How deep are the batteries being discharged usually?

Find attached a Depth of Discharge chart vs. expected life for your reference.

[boandbabs]

I put them on charge at end of every day they are used. Usually batteries are pretty low when the kids stop riding. That's the reason they stop when they do. The charger I use is new when I got the batteries. It keeps them maintained when not in use. Thanks,

[Sergio]

Do You have any accessories connect to a few individual batteries?

If the "battery tester" was not a hydrometer (or refractometer) You may want to use one to test the cells individually.

Your pack run time is equal to the weakest battery even if all the other ones were brand new.

[DaveTM]

Where do you "park" your cart when not in use? Is it in a heated area or left in a shed outside?

I dunno what part of the country you live in, but if your cart is outside and it's getting cold and night, cold temps will affect battery performance.

When I had FLA's on my cart I could get 12 miles on gently rolling dirt packed roads\trails. When the temps got below freezing that was cut in half or more.

I know it's not been all that cold out yet.....but temps will have a negative impact on milage.

[JohnnieB]

Gere is a SoC chart for US Battery brand batteries as well as a graph showing USB cycle vs three other top brands and a chart showing storage capacity (range) vs temperature.

[boandbabs]

Thanks, the cart only has the light connected to a few of the batteries. The cart is always stored inside of my shop when not in use. The temp here in South Carolina is still in the 70's at night, 80's in the day. I have not used a hydrometer. Thanks for the responses.

[JohnnieB]

Originally Posted by boandbabs

Thanks, the cart only has the light connected to a few of the batteries. The cart is always stored inside of my shop when not in use. The temp here in South Carolina is still in the 70's at night, 80's in the day. I have not used a hydrometer. Thanks for the responses.

That is the formula for killing batteries.

They are connected in series for charging and when two batteries are tapped for 12V accessories those batteries are discharge more than the rest, imbalancing the pack and royally screwing up the charging process. In a nut shell, the charger only sees the whole pack and net result is some batteries are being overcharged while others are being undercharged, so none are being charged correctly.

Use a 36V to 12V reducer or a separate 12V battery for accessories.

Use a 12V charge on the batteries used for lights and give the a good charging.

After resting for 12 hours, all six batteries ought to be withing 0.1V of each other.

[kernal]

Originally Posted by boandbabs

I put them on charge at end of every day they are used. Usually batteries are pretty low when the kids stop riding. That's the reason they stop when they do. The charger I use is new when I got the batteries. It keeps them maintained when not in use. Thanks,

Another killer of batteries. You only get so many charge cycles and the deeper the batteries are discharged before re-charging the shorter the total life span.

[boandbabs]

Thanks, the lights that are connected to 2 batteries are never used. Only day time driving 99% of time. I'm thinking the batteries have been cycled too much but they do check good. Since January 2019 These batterie's have been used & charged just about every day with exception of some rainy days(a lot lately) and a few colder days in the winter. My kids do ride it all the time until now that it won't last but about 6 miles. I do have a few batteries with black moist post. Thanks for the advice.