Nominal voltage of golf cart batts

[fred4936]

All good info! I had Trojan T105's in my electric truck. The frame rotted out, so I sold most of the batteries and kept 4 for the house bank on the boat. they are 4 years old now, still working fine. They always rested at 6.4 volts, so the 6.37 number is good. One thing to keep in mind is that the resting voltage is temperature dependent. The 6.37 number is only valid at a given temperature, probably 85 degrees F, which is the optimum temp for lead acid.

[OldManMirage]

As i said in the original post, the batts are coming out of my mother-in-laws golf cart. The reason is that they don't last days like she is used to. She and my wife are going on a trip and they want the cart to last them while they are at their destination. Pretty sure they have more than enough life left for me.

I have set up a pair of them, and hooked up a trolling motor that pulls 18amps on high. Its running now. They were 12.74 sitting. Dropped to 12.36 when I turned on the motor.

What would you consider 50% ? Or should I go past that ? I was going to let them drop to 12 and see how long that takes.

[thomm225]

Originally Posted by OldManMirage

As i said in the original post, the batts are coming out of my mother-in-laws golf cart. The reason is that they don't last days like she is used to. She and my wife are going on a trip and they want the cart to last them while they are at their destination. Pretty sure they have more than enough life left for me.

I have set up a pair of them, and hooked up a trolling motor that pulls 18amps on high. Its running now. They were 12.74 sitting. Dropped to 12.36 when I turned on the motor.

What would you consider 50% ? Or should I go past that ? I was going to let them drop to 12 and see how long that takes.

Didn't see this (in bold above) in your first post but it tells you just about all you need to know......which is to probably to go ahead and buy some nice new batteries.

You may find a couple decent batteries that will last you a while out of the group, but they have had to support the weaker one(s)

So if you don't like the install process then new may be better especially if you are only running two batteries.......which with some types is under $300.

I had to buy the carrying strap for mine, but the cost was still under $300 for the two 6 volt 220 ah golf cart batteries

[OldManMirage]

2 hours so far, voltage is down to 12.18, trolling motor pulls 18 amps.

[Wotname]

Keep going until you reach 10.5V.
Then multiply the time (in hours) by 18 (amps) and the result will be roughly the true capacity of the batteries in amp-hours (AH).

Recharge.

You have used up one cycle of their life but you now know what capacity is available.

[Wotname]

I am assuming the trolling motor is running under load i.e. the prop is in water.

The result will be approximate as the current draw won't remain at exactly 18 amps over the cycle but it will be close enough to be useful.

[PaulCrawhorn]

Once batteries start to exhibit obvious performance decline, they are way past the point where they should have been recycled.

There are dangerous "failure modes" and the odds of them happening skyrockets once you get to that point,exponentially every 5-10 cycles.

[Don C L]

Sounds like you got the answers you need but I'll add that my two new 6 volts (Interstates, like T-105s) in a series are full at 12.7v but my charger might be showing over 13.0v when charging (just before dropping to float charge) and it takes a while for the voltage to settle down to 12.7 to 12.8 or so once it is off. Did you take the reading just after taking them off the charger? 6.37v is correct, and I wouldn't be surprised to see 6.5v right after one is charged. But as everyone is saying this won't give you the health or capacity.

[OldManMirage]

I shut down the experiment after about 4.5 hours. The voltage was still over 12 and I had pulled at least 75-80 amps out the pair. That's more than sufficient for what I want them for now.

I appreciate all the help.

[Wotname]

[GILow]

Originally Posted by OldManMirage

I shut down the experiment after about 4.5 hours. The voltage was still over 12 and I had pulled at least 75-80 amps out the pair. That's more than sufficient for what I want them for now.



I appreciate all the help.

That’s the problem with golfers these days, just too fussy.

[OldManMirage]

Originally Posted by GILow

That’s the problem with golfers these days, just too fussy.

Lol, hey you're talking about my mother-in-law !

And what's really funny is she doesn't golf, just uses it to ride around her neighborhood. But the main reason for the whole change-out is that she and my wife are taking a trip to Cedar Key and they use the cart to get around and don't want to get stranded.

[GILow]

Originally Posted by OldManMirage

Lol, hey you're talking about my mother-in-law ! [emoji3]



And what's really funny is she doesn't golf, just uses it to ride around her neighborhood. But the main reason for the whole change-out is that she and my wife are taking a trip to Cedar Key and they use the cart to get around and don't want to get stranded.

And there was me thinking golf carts were used for golf.

[OldManMirage]

Originally Posted by GILow

And there was me thinking golf carts were used for golf.

Ha ! Not over here mate. I would venture to bet that the majority of carts here in America are used more off the greens than on. I have seen a lot of lifted carts with gas engines here in the south. We'll hot rod anything !

Also, thanks again to everyone who participated in this thread. I did end up buying 6 new Duracell GC-2's from Sam's Club for a total of $641 including tax. Those are going in the MIL's golf cart.

I took the 2 with the highest resting voltage that I used in my trolling motor experiment and I'll be putting them in my boat. I'm doing that mostly so that I can finish cleaning up my existing wiring and setting the system up the way I want. I'll be buying a fresh pair of batts when I'm closer to actually going cruising.

[Dieseldude]

Have a few heavy 12 volt loads around such as some vehicle head lights? Hook up a few and check the current with an amp meter. Run them a while and keep a watch until they fade. Just do the math of amps time hours.