affordable aftermarket charger, buy or not?

[Gonkulor]

let them settle for 12 hours or more and then take another reading. I sure hope that charger didn't overstuff your pack! I don't know what damage could have been done but my mind leads me to believe an over voltage for an extended period of time would melt the plates inside the batteries.

Please keep us informed.

[newbie2gonewild]

Originally Posted by Gonkulor

let them settle for 12 hours or more and then take another reading. I sure hope that charger didn't overstuff your pack! I don't know what damage could have been done but my mind leads me to believe an over voltage for an extended period of time would melt the plates inside the batteries.

Please keep us informed.

I will take theses batteries to them and gladly get 6 new ones. The only thing I don't like is my batteries are better quality than theirs and I just bought mine in May 2012.

[Rickochet]

Originally Posted by newbie2gonewild

I will take theses batteries to them and gladly get 6 new ones. The only thing I don't like is my batteries are better quality than theirs and I just bought mine in May 2012.

I would wait until you get some opinions from people who are knowledgeable about batteries. Perhaps you just need to discharge them down to 38.2v and all is well.

In the meantime make sure your voltage reading is correct. Maybe try a different volt meter. Check the water levels in each cell.

[JohnnieB]

Originally Posted by newbie2gonewild

I tested them 30 minutes after charging and it was 52, after 60 it was 50, after 5 hours they were fluxuating between 50 and 46

Does that mean some of the batteries were reading 50V, others were reading 46V and the rest were reading something in between those two voltages, or that the voltage reading on each battery was fluctuating higher and lower while the DVM was actually attached to it?

Except for the last part of your statement (Highlighted in red), your batteries might be okay.

-----------------

Charging a 2V cell to 2.79V is at the upper limit of Trojans recommended charge curve (Attached), which is 50.22V for an 18 cell (36V) battery pack.

They went a couple volts higher than that, but it might not have harmed them because overcharging is when the charging current is continued after the on-charge voltage stops increasing, which may or may not have happened.

(I suspect Trojan is a little conservative on their recommended charge profile. )
---------------

My first suggestion would be to verify the accuracy of the DVM and/or replace the DVM's battery.
Second would be to drive the cart a couple of miles and then measure the pack voltage and the individual battery voltages.
The pack voltage should be in the 37V to 38V range, maybe a bit over 38V because they are relatively new, but definitely less than 40V.
More importantly, all the individual battery voltages should be within 0.1V of each other.

--------------
If the battery voltages indicate they are damaged, make sure you receive replacement batteries of equal or greater Amp-Hour ratings.

[mack Courtney]

So basically what you are saying is that with the Trojan batteries for a set of 6 6 volt batteries (18 cells) a full charge could easily be 50.2 volts? just for curiosity what influence does the temperature have on the equation? lower temps raise or lower the charge capacity? and of course the accuracy of the DVM is also a big factor?
I agree that before doing anything as rash as taking a charger back or hitting the panic button, maybe there isn't anything out of the ordinary?

I thank everyone for this having this discussion.

I would have expected that a full charge on new batteries would be around 38 volts.

I have read that with proper breaking in and charging with a proper charger, a set of batteries could increase their total charge amount over 12 or more charging cycles, do you all agree with that?

[JohnnieB]

Originally Posted by mack Courtney

1. So basically what you are saying is that with the Trojan batteries for a set of 6 6 volt batteries (18 cells) a full charge could easily be 50.2 volts?

2. just for curiosity what influence does the temperature have on the equation? lower temps raise or lower the charge capacity?

3. and of course the accuracy of the DVM is also a big factor?

<snip>

4. I would have expected that a full charge on new batteries would be around 38 volts.

5. I have read that with proper breaking in and charging with a proper charger, a set of batteries could increase their total charge amount over 12 or more charging cycles, do you all agree with that?

1. No. I'm saying that the on-charge voltage could reach 50.2V and still be within Trojans recommended charge curve.
The only concise definition for "Fully" charged that I have been able to find is when the Specific Gravity of the electrolyte in a cell does not increase while a charging current is passing through it.

Since the on-charge voltage increases as the specific gravity of a cell's electrolyte increase, it also ceases to increase when the cell if fully charged.
However, what that voltage is specifically, is not defined.

Trojan recommends that 36V battery chargers with selectable or adjustable maximum output voltages be set to 44.4V, which is slightly above 2.35V per cell.
Most automatic 36V Golf Cart battery chargers terminate the charge in the 44V to 46V range.

Does that "Fully" charge the battery pack. No, but it is awfully close to it and there is little danger of overcharging the batteries after they get older and have less storage capacity.

2. I'm not sure how much the on-charge or at-rest voltage varies with temperature, but the storage capacity does.
See the Attached.

3. Some DVM's read high when their internal battery is low, others read low.
FWIW: I replace the batteries in my DVM's when we make the switch to Daylight Saving Time each spring, along with the batteries in clocks, smoke detectors, Etc.

4. New Batteries would most likely be a bit higher than 38.2V as shown on the State of Charge carts.
Those charts are derived from the average voltages of a statistically significant sample size of matured 2V cells and extrapolated for the various battery and battery pack voltages.

Also, the voltages given is after the cells have rested about 12 hours after charging is terminated.

5. Yes, but it will take more than 12 charge cycle to reach maximum storage capacity.
See first two sentences on attached.

[kab69440]

I can't remember precisely off the top of my head, but I posted charge cycle info for Johnnie and it seems my cutoff was in the neighborhood of 45 volts on my TC III. I wouldn't think one minor overcharge would damage them. If they were a few years old, you might have gotten a little capacity back?

[mack Courtney]

Ok, now I think I have it straight about the on charge voltage being that high. I will log the different voltage readings of my new Energizer batteries from SAMS. The same size batteries at my local independent auto supply store would have been $140 each with my standard dealer's discount and the Energizers from SAMS club were $81.83 each at SAMS. They sell a lot of golf cart batteries out in Abilene, several pallets per week , 100% replacement if they fail within 12 months.

[newbie2gonewild]

I let my batteries sit for 24 hours and replaced my battery in dvm. I am getting 6.9 volts per battery and a total of 38.4 for the pack. Maybe they needed to sit or my battery was low in my dvm. Who knows?! Thanks for everyone's help and now I am more knowledgeable in the battery category. Now to upgrade my motor and controller and we will be set for the next camping season! THANKS EVERYONE, I am so grateful for you all. THIS IS THE BEST FORUM!!

[JohnnieB]

Originally Posted by newbie2gonewild

I let my batteries sit for 24 hours and replaced my battery in dvm. I am getting 6.9 volts per battery and a total of 38.4 for the pack. Maybe they needed to sit or my battery was low in my dvm. Who knows?! Thanks for everyone's help and now I am more knowledgeable in the battery category. Now to upgrade my motor and controller and we will be set for the next camping season! THANKS EVERYONE, I am so grateful for you all. THIS IS THE BEST FORUM!!

A pack voltage of 38.4V after 24 hours rest is about right, but 6.9V per battery is a bit high and it doesn't add up.

Six time 6.9V equals 41.4V, yet the pack voltage measures 38.4V. There is 3.0V missing someplace!

There are 5 high current cables connecting the six 6V batteries into a 36V battery pack and those cables and/or the connections at each end of them could be where the voltage goes missing.

Using your DVM, measure across each of these cables, from the lead post on one battery to the lead post on the next battery.
You should get -0- (Zero) volts.
If you read any voltage at all, the connections and/or the cable is bad.

Note: Measuring across the cables while battery pack is on charge will make bad cables and connections more obvious. Still should be zero volts across them.