Do golf cart chargers always charge to equalize voltage?

[DSchmidt_2000]

I'm asking you all because:
- you're all smart and have long term history with FLA batteries
- BuggiesGoneWild won't activate my acct for me to post my question there.

48V cart with new set of 6 qty 8V Trojan T-875 batteries and a Lester Summit II charger.

I'm helping someone with a golf cart at a horse ranch. Replaced bad batteries and dead charger. I topped each up individually before installing in the cart.

With the new batteries installed, I plugged the charger in expecting it to say "Fully Charged", but instead it started a charge cycle. After about 10-15 mins, the battery pack voltage went to 64.4V, 6.4A charge rate, cells were vigorously bubbling, a slight smell of rotten egg, and charger said estimate time to completion was 3 hours. I terminated the charge as it seemed excessive. Restarting it only did the same thing. Battery profile is correct for these batteries.

I called Lester the next day and was told this is normal. Part of their answer was that it will do an equalize charge every ~ 30 charges, but he also said it will go up to 64-65V with every single charge! They said it's normal, that Trojan gave them the charging profile to follow. They also said the charger is in phase 3, the finishing stage.

Trojan's datasheet shows a bulk charge voltage of 9.88V, equalize of 10.80. 6 x 10.80 = 64.8V. Datasheet

Question for you guys that either have a golf cart, with or without a Lester Summit II charger, do you view going to equalize voltage with every charge excessive? I don't want to cook these batteries, and I also don't want a coating of acid on everything.

I asked Trojan what they thought, and got short reply "the info you need is on our website".

I could load an AGM profile into the charger. This would take the batteries to 9.88V/battery, no equalize. Figure I could do a manual equalize once a month.

Thoughts?

[DSchmidt_2000]

Here's an update - profile on charger set to use only 4A for the last stage of the charge (stage 3). I downloaded the charge history and see that the battery is hitting 63V at the end of the charge. Battery tops are staying dry so the designed overcharge isn't boiling away the electrolyte too much.

I'll keep monitoring the charge. (I really like that the charge logs each of the charges, including the voltage and time spend in each of the 3 charge stages.)

[joebedford]

x

[DSchmidt_2000]

CA Traveler wrote:
Interesting that the manual says the batteries should bubble at the end of the finish stage. If finish means the end of stage 3 ie float voltage then that's new to me. If instead it means during equalization then that is normal. And they do recommend equalization every 30 days. It's not clear to me as the chart shows both float and equalization. They also state to avoid contiuous float if charged for more than once a week.

Pretty sure they mean bubbling during the tail end of stage 3. Float voltage is a lot lower and should not bubble.

That graph to me is only the charge cycle, showing the 3 phases, and the last phase does hit the equalize voltage but then immediately terminates charge. Now I see what Lester means by charge termination being dV/dT - they're waiting for the voltage to no longer rise during phase 3 before stopping charging.

So I'm interpreting all this data to mean that normal charging always hits equalize voltage, or at least until it doesn't rise anymore, and an actual equalization holds that higher voltage for 1-2 hours.

I'm going to set the battery profile to the lower setting (4A finishing) as that is still in-spec per trojan. Not as good as 2A with the battery tender recommendation, but better than 6A.

[CA_Traveler]

Interesting that the manual says the batteries should bubble at the end of the finish stage. If finish means the end of stage 3 ie float voltage then that's new to me. If instead it means during equalization then that is normal. And they do recommend equalization every 30 days. It's not clear to me as the chart shows both float and equalization. They also state to avoid contiuous float if charged for more than once a week.

[DSchmidt_2000]

Sure enough, Trojan does recommend getting the voltage up there. Sorry for the long entry.

Starting on page 17 From this document

Trojan recommends a 3-phase I-V-I profile for charging its flooded batteries
o Phase 1: Constant current bulk charge
A constant current equal to 10-13% of C20 is applied as the voltage slowly increases.
The bulk phase ends when the voltage rises to the absorption voltage.
o Phase 2: Constant voltage absorption charge
A constant voltage equal to 2.35-2.45 V/cell is applied as the current slowly declines.
The absorption phase ends when the current falls to the finish current.
o Phase 3: Constant current finish charge
A constant current equal to 1-3% of C20 is applied as the voltage increases. The finish phase
ends when the battery is fully charged. Flooded batteries will gas (bubble) toward the
end of the finish phase to ensure proper mixing of electrolyte.
o Refer to Table 5 and Figure 6 for system charging parameters and typical voltage and
current profiles

Graph


I have these options with my charger. Lester recommended is profile 22251, but 22250 has a lower finishing charger amperage of 4 vs 6A. Or I can use the AGM which has no finishing charge, but uses dI/dT.

Per the Trojan spec of 1-3% of C/20, 4A is better than 6A, and everything else in the charge profile is the same.

Page 1Common Lester Summit II Profiles

time2roll wrote:
I recommend the Battery Tender brand.

Thanks! I'm going to try and make this charger work as I've already bought it. There's so many profiles available, I just need to find the one that doesn't boil the batteries.

[time2roll]

I recommend the Battery Tender brand.

Yes it will go through equalization every time. However the cycle is shorter and the equalization is limited to 2 amps to avoid the excessive bubbling. This slows the rise in voltage and slamming the batteries at max for hours.

I used this (12v version) on my golf batteries in the RV for 20 years and it works perfectly as expected. Never felt there was an excessive overcharge during the equalization.

https://www.batterytender.com/battery-chargers?output-voltage=48V

Shop around

[DSchmidt_2000]

joebedford wrote:
I don't stabilize my GC batteries ever (unless the charger does it without me knowing but I doubt it)

Some do. What charger do you use?

The old one that died on this cart was a Delta-Q SC-48

[DSchmidt_2000]

Thanks everyone! Here’s some answers:
- I measured at the posts and it was close to what the charger said (within a few tenths)
- charger is computerized and keeps track of the number of charge cycles
- I was thinking 9.88 should be target too, and hold that until current drops.
- batteries are new, right off the Trojan delivery truck.
- I took them home and connected them one at a time to a power supply set for 9.8V. So they were even.


The AGM profile for this charger will charge CC to 9.88V per battery (59.28 for a 48V system) and then wait for the current to drop before terminating charge. I’m going to give that a try.

Regarding equalization, guessing that’s more important when many packs are in series like this one (6qty), hence doing it once a month.

I’m surprised Lester is taking the voltage so high with every charge. They’re a big company, doing this a long time, and I’m not reading that they are known for cooking batteries. Really weird what I’m seeing and what tech support told me.

[joebedford]

I don't stabilize my GC batteries ever (unless the charger does it without me knowing but I doubt it)

[CA_Traveler]

"Part of their answer was that it will do an equalize charge every ~ 30 charge"

Wondering how they determine this.

Also charging each battery independently may have resulted in inconsistent charging. Plus it can take a few charging cycles for new battery stabilization.

[CA_Traveler]

Did you measure the voltage at the battery posts? There will be some, perhaps small voltage loss for all of the cables.

I would use the Trojan bulk spec of 9.88V. My understanding is that equalize is only needed when required due to lower than expected voltage. Are you suggesting once a month because it's used every day?

I believe Trojan has information on charging and equalization.