Mixing Batteries

2carts

I have a Club Car DS 48 volt golf cart with TrojanT-875 batteries. I have noticed it getting slower and slower going up inclines. I checked the voltage on the batteries and 5 of the batteries are 8.5 volts and the 6th battery is 6.2 volts. Would that one battery cause the cart to slow down and if it is can I replace that one battery or are the other 5 going to quickly fail also? Also, if I replace the bad Trojan battery can I replace it with an Interstate 8v golf cart battery?

BGW

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LukeL

You have a bad battery for sure. How old are the others in the pack? A new one will quickly degrade to the level of the others, and an old one will bring the others down. I always try to locate a strong used one before blowing money on a single new replacement.

The Big Weezy

That battery is bad and needs replacement. You could use a different battery, but there may be manufacturing differences and such they may make perform differently than the others. May cause pack balance issues. I would at the very least replace it with a battery of the same manufacturer that matches the rest. If the pack is over 5 years old, I would consider replacing the whole pack. Depending how long that battery has been bad may have caused the other batteries to be damaged. The charging system will try achieve a specific voltage before shutting down. A bad battery may cause the charger to over charge the good batteries trying to make up for the bad battery.

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2carts

Thanks for your reply. I replaced the one defective battery and it made a big difference in the cart's performance. I know the advice about replacing all of the batteries at one time is correct, but I want to convert to Lithium ion batteries after the first of the year and did not want to dump a bunch of money on a whole new set. If this new battery will get through the rest of this year I will hopefully be ready to do the conversion.

Budule

I have had all kinds of battery combos mixed , different brands and different voltages ….is it ideal ? no ...did it run fine for long time ? yes....cart does not care what brands or what each cell is reading , pack voltage is really all that matters to the cart ...now if you need max range for some reason between charges , then no...but if you just run around in it , they be fine...

battleboro

I am faced with a similar dilemma; 5 "good", 8v batteries that have individual, fully charged readings of 8.45 volts. This is considered 100% state of charge (SOC) according to the chart in the thread, Golf Cart Repair and Troubleshooting > Electric Club Car > Everything to do with batteries! (new member for 5 days, unable to post links until day 7).

A 6th battery is showing 6.09, "bad".

How would we define "old" in this thread's context? Calendar age or performance (maximum SOC) degradation?

I am a novice at this, but it would seem to me that if 5 batteries can still achieve 100% SOC, they are good and a new battery would not be negatively affected. Unless... the old batteries start to degrade (unable to achieve 100% SOC), it goes unnoticed and then the new battery will start to degrade at a faster rate.

Budule

put in 1 battery , cheap and easy on the back ….

BUT , you need to load test your "good batteries" …….voltage at rest doesn't really tell you much imo ….have to put a load on each battery and watch how far they drop …..

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battleboro

Good point Budule. I forgot about load testing. Before I purchase a load tester, a quick search turned up this post from ScottyB: Golf Cart Repair and Troubleshooting > Electric Club Car > Voltage while driving?????? (one more day of membership and I can start posting links )



As I work my way through charging each battery individually, and giving them at least a 12 hour post-charge rest, I am getting less than a volt drop under load (using the cart as my load tester by jacking the back tires off the ground). Considering the age of the pack, and as long as the rest of my process proves a "good" 5 out of 6 pack, I am leaning heavily toward just replacing the 1 bad battery.



I think my final concern is finding a new battery with a Ah rating that matches the rest of my existing pack (US Battery - US 8VGC XC2 - 170Ah). So far, my research is showing I'll be buying another US Battery - US 8VGC XC2.



A local battery source informed me that US Battery makes a "black box" version, but it is only 160Ah. I am concerned the existing battery pack performance will be degraded to the new battery (170Ah-existing vs. 160Ah-new). If the price difference between "black box" and "brand label" is not too much, I may go with a "same-same" replacement for peace of mind and ride it out... no pun intended.



My son just wants his Papa's old CC to run like stock. It's me that has visions of lifting, upgrading and accessorizing. I think if I can get it running like stock, he will start seeing possibilities. Then I may replace the battery pack if it starts showing its age.



Thoughts?

Allmanac

You really should load test the batteries with the cart on the ground and you in it. Being off the ground does not put much load on the electronics. Take your meter and attach to each battery one at a time and lay it on the seat. Take it for a spin and then record your voltage drop as you are driving. That will give you a better picture. Most folks on here don't recommend mixing old and new batteries. It is mostly recommended to replace the bad battery with one of similar age and ah if replacing the pack as a whole is not in the budget.

battleboro

I was thinking the same thing about load testing; applying a real load. Either I misunderstood what was being said in another thread or they felt like load testing off the ground was sufficient... or was that in a youtube video.

At any rate, I will take your advice. I have a feeling a new battery pack is in my future.

Thanks.