Stereo and Lights draining battery pack

[Cecilt]

I had a stereo installed a few months ago and they wired it up to the same 2 batteries that run my lights. This worked fine for the 10 days in early July we were at Ocean Lakes as I would charge the battery pack every night. However, we just got back from another 10 day trip to Ocean Lakes and on about the 5 night the cart almost died while driving at night. Limped it home. Charged it up and next night after a few hours with lights and batteries on stereo started cutting out so I knew this meant it was probably going to die soon so just went back to camper.

Now, my question is is I want to just wire the lights and stereo directly to a 12v marine battery and install and trickle charger. I have read to run the negative from the stereo to the negative on the 12v. My question here is since it is currently wired to the pack would there be a negative ground on the golf cart as well?

Lastly, what is the liklihood that my batter pack or possibly 2 batteries are toast? I am horrible at electronics and wouldn't even know how to test to make sure all or some are still good? The batteries were new last year and we used it 10 days at the beach last year and 30 days this year. Sits the rest of the time and I charge them 1x month and keep the fluids topped off. tks

[JohnnieB]

Bad news first.
There is a very definitely a likelihood that the two batteries the lights and stereo where connected to, are toast.
There is also a possibility the other four are damaged.

You can check them with a DVM.
Measure the voltage of each battery about 12 hours after the charger shuts off automatically.
A good battery will have about 6.37V and all of the voltages should be within about 0.1V of each other.
Drive cart around a bit and then check the voltages again. They should still be within about 0.1V.

Or you could take it to a cart dealer and have the batteries load tested.

There is no ground on a golf cart (or shouldn't be - Safety issue)
All accessories should have two wire attached, one to B+ and the other to B-. Of course, there will most likely be an off/on switch in one of the two wires.

Just move all the wires that went to the accessories from the battery pack and attach them to the respective + or - terminals of the entirely separate 12V battery you are adding.

You should end up with only four wires connected to the 36V battery pack. Two heavy cables to solenoid and controller (B+ to solenoid and B- to controller) and two smaller, but still heavy gauge, wires to the charger receptacle.

Hope this helps.

[Cecilt]

Wow, that could be bad news. I should clarify we only used the golf cart about 20 days total after the stereo install. We would run around a little during the day with stereo and no no lights and then maybe 2 hours at night with both on for the 18-20 days. Lights have been on it since I bought it so they have run off the same 2 batteries the shop wired the stereo to. Since I told the shop to install a reducer and they did not, looks they have some explaining to do. I sort of figured when he charged me $25 for a reducer he didn't put one on as they are over $100.

[Cecilt]

Okay, here are my results. First, I made sure I was pulling readings from each battery separately so I would remove the postive and negative from each one, test and re-attach cables and move my way through the batteries. The batteries sat about 12-18 hours(probably on the higher end) from fully charged state to when I did the test.

Standing on the passenger side and starting with the battery closest to the cowl here were my readings:

Driver Side
6.45/6.45(these are the 2 batteries the stereo and lights were hooked up to)
6.52/6.51
6.50/6.53
Passenger Side

I drove the cart around for about 8 minutes and up some nice hills in the neigborhood and re-tested.

Driver Side
6.36/6.35
6.51/6.49
6.49/6.49
Passenger Side

Any thoughts on the above. I did notice the cable from the solenoid to the first battery on the passenger side was pretty hot after driving. Normal?

Just picked up a marine battery to make the conversion but before doing anything I want to make sure the battery pack is good to go. Tks

[JohnnieB]

Wow! Those are some high battery voltage readings. Off the top of the charts.
What is the manufacture and model, I want some.
Here is a Voltage vs State of Charge chart. (Voltages are taken after about 12 Hours rest)

The first set of reading are great and the second set are almost as good.
The voltage spread did double from 0.08V to 0.16V, but that shouldn't have caused the problem you had and the two weaker batteries are only slightly weaker.

The two batteries probably got discharged enough from running the lights and stereo to lower the pack voltage enough to make the cart misbehave, but they seem to have recovered from that abuse quite well.

Giving those two batteries a couple extra hours of charging with a 12V charger following the normal charge of the total battery pack with your 36V charger would help them recover even more, but other than that, I think you battery pack is good to go.

BTW: You can attach the 12V charger to the two batteries without disconnecting them from the rest of the pack. Just go from negative post on rear driver side battery to Positive post on front one.

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Any of the high current cables getting hot is abnormal. Ideally, they shouldn't even get warm.

What happens is resistance in the cables and/or connections converts a portion of the electrical energy supplied by the battery pack into heat rather sending it to the motor where it is converted to horsepower. You cannot eliminate all of the resistance, because copper isn't a perfect conductor, but you can eliminate most of it with well constructed, heavy gauge cables and clean connections.

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If you installed a DVM battery meter like the one shown here: http://www.cartsunlimited.net/Digita...ry_Meters.html
You could avoid running the pack down too far unintentionally and if you added a switch, you could also check the 12V accessory battery.

[kab69440]

Johnnie- I put NAPA brand GC batteries (8144?? Can't remember off the top of my head...) in my cart. After almost two years of anal retentive care and maintenance I also have four cells at 6.5v and two cells at 6.4v rested. I use the same TC3 charger I posted all those pics of for you. I equalize once or twice per month and try to make time to drive at least once per week to keep the electrolyte from stratifying. Total rested charge after twelve hours is 38.6-38.7v.

[kab69440]

I have been overjoyed with the performance of my NAPA golf cart batteries over the last two years. They cost a fortune, but have done very well for me. I used to abuse the crap out of my cart (not to mention my body) by being outside 10 to16 hours a day in the dead of winter and towing equipment that only an idiot (guilty) would ask a golf cart to move. Dang that job sucked, but the cart was my best friend doing it!

[JohnnieB]

I just posted a couple comments about manuf. Specs. in another thread.

8144 is rated 186AH @ 20Hr rate and 110 minutes @ 75A
T-105 is rated 225AH @ 20Hr rate and 115 minutes @ 75A
Both weigh 62 Pounds.
I wonder what the respective ratings would be if tested the same way on the same test equipment.

I think the SoC charts are based on Trojan batteries, which use an acid dilution that has a SG of 1.277 when "fully" charged.
If the acid concentration is higher, the voltage is probably higher also, but I suspect the actual storage capacity would be about the same.


Just curious, but do you know what the voltage is when the TC3 shuts off?
I'm starting to believe just a small difference in the final on-charge voltage makes a large difference in stored energy.

Thanks for the info.

[kab69440]

I don't actually know that? If I can ever get a day off work, I know a way to find out, though!


Sorry about that second post, I believe it was meant for another thread. Not sure how it ended up in this one?

[Cecilt]

Thanks for the encouraging news that my battery pack seems to be good. I picked up a 12v marine deep cycle marine battery and a 1.5 amp trickle charger. Do you think this trickle charger will be sufficient. My use of the golf cart with both lights and stereo on at the same time will be 2 1/2 hours at most over the course of 14 or so days. Other use during the day may total 2 hours of use with just stereo on. Part of what Ocean Lakes in Myrtle beach offers!!!!