Identifying a Bad Battery

[greenmonster]

I drained the pack to less than 50% (35.7) after 7.5 miles this weekend. I've taken the same route (10 - 11 miles) many times before and made it home with pack voltage in the high 36's.
When I got home I checked each battery and 5 were in the 6.1 - 6.2 but the 6th measured 4.8. I charged the pack overnight and the next morning each battery read 6.4. I bought a Specific Gravity meter the next day and checked each cell of each battery.
The battery that read 4.8 after the ride had one cell show up in the white or fair range, one cell showed the red range, and the last one was on the low end of the green. The volt meter read 6.4.
The set is 15 months old and I've been diligent about keeping water levels checked and keeping the pack charged.
Have I identified a bad battery? And did it cause the pack to die prematurely?

[scottyb]

A big difference is cell readings is an indicator of a bad cell, you have a bad battery. You should replace it so the other 5 don't get over taxed. If you had a digital voltmeter connected to the pack while you ran the cart you would have seen some deep drops in voltage.

As to what causes this? The batteries could have been under rated for the application, the water could be heavy in certain minerals, or the load could have been uneven? They could have been over taxed, they could have been left in a state of deep discharge, It could be defective?
I can't say it is any one thing from here knowing what little information you have given?

[greenmonster]

Originally Posted by scottyb

A big difference is cell readings is an indicator of a bad cell, you have a bad battery. You should replace it so the other 5 don't get over taxed. If you had a digital voltmeter connected to the pack while you ran the cart you would have seen some deep drops in voltage.

As to what causes this? The batteries could have been under rated for the application, the water could be heavy in certain minerals, or the load could have been uneven? They could have been over taxed, they could have been left in a state of deep discharge, It could be defective?
I can't say it is any one thing from here knowing what little information you have given?

ScottyB Good Morning! I had the digital volt meter that I got from you (that is very sweet by the way) connected and I did notice that the reading dropped to the 28-29 range while riding. Since I've installed the digital meter, I've not noticed it falling below 32.
The batteries are powertron and I've always used distilled water to bring levels up. I have a 12 volt deep cell marine battery that runs lights and accessories so the pack has never been used for anything but pushing the motor.
I've never let the cart sit uncharged for any long length of time.

I'll take your advice and replace the battery. A local battery dealer has used US Batteries- would that be a good plan? I would like to get another year out of this pack before I replace all batteries with a premium set.

Thanks!

[scottyb]

You can just get another powertron, should be a little prorated discount at 15 months? But my guess is they are not 220-225 amp hour batteries? You could have just a weak one and some internal connection was lost?

[twp5253]

I just went through the same thing although I have not yet mounted up Scotty's digital meter....that should really help with knowing how much power I have left in the pack. I have been using a load tester from Harbor Freight and for 20$ I can put a 100amp load on the batteries one at a time. However, I found out that you need to leave the load on for more than a few seconds. You see, all my batteries were checking good on charge for volts and load test. But, after using the cart some, pulling out some jet skis, I found one battery that if you hold a load on it for more than say 5 seconds...it completely goes in the toilet. I think I will also order up a specific gravity tester.