What are the correct voltages for a 48v charger to go up to before it cuts off?

[JohnnieB]

Originally Posted by Jeffreynmandy

I'm a little puzzled by it also. I can't say for sure. when I get a chance I'll drive it a few miles and stay home to watch it.


50.4 is a good number though right?

No it is not a good number.

If you have Trojan brand batteries, an At-Rest voltage of 50.4V is only 88.5% charged.

What make and model batteries do you have and how old are they???????

[Jeffreynmandy]

They are new Trojan t-875 batteries. It must have cut off too early. I don't know the history of the charger. It had to have sat, because I had to clean webs from the little fan in it. It wasn't turning before that and cut off from over temp. It was just completly off this time.

It has done one complete charge, and cut off at 64v, I've made a couple charges that I unplugged at 63v. That's the only uses I've had with it. It came in a package deal of used stuff.

I may invest in a new charger. I'll keep an eye on this one a couple more times first though.


I globbed corrosion protectant on the terminals last night. I had to unhook the main pos and neg earlier to make a small weld. The syrupy protectant could be in between the terminals, but I doubt that.

[JohnnieB]

Check the individual battery voltages from about 12 to 24 hours after the charger shuts off. Measure from lead terminal to lead terminal, so the goop won't interfere with the readings, if it is, which it probably isn't.

Attached is a Voltage vs SoC chart for Trojan batteries.
An 8V Trojan battery ought to read at least 8.49V. When new, they will read a little higher, but if they read lower, something is amiss.

[Jeffreynmandy]

Me or the charger must have had a brain fart. I plugged it in last night and this morning it was lit green with a full charge. It was right at 54v


I drove it about 8 miles today and I'll charge it again tonight.

[JohnnieB]

Originally Posted by Jeffreynmandy

Me or the charger must have had a brain fart. I plugged it in last night and this morning it was lit green with a full charge. It was right at 54v


I drove it about 8 miles today and I'll charge it again tonight.

If you plugged it in by 8PM, the charger probably shut off by midnight, so measure the battery voltage at noon, or later, today.

The 54V was a bit high, but the batteries are new and they may have been resting less than 12 hours.

[Jeffreynmandy]

I checked it again later and it was 52.2

[JohnnieB]

That is about right for new batteries.

[Jeffreynmandy]

Originally Posted by cgtech

I think that voltage is just a little high for trojans to see on a regular basis, keep an eye on the peak voltages while they are on their extended charges in the future. Star car used those "eagles" from the factory, and they charged those 8x 6v trojans too high, too long (i have a sheet from "eagle" that shows 32 hours on charge is "OK" before cutting off during "maintenance mode" lights 1 & 5 flashing ?!?!). The batteries all had Positive terminals protruding upward from their original location at the end of their life, sometimes enough to cause small cracks in the lid of the battery. In that Star situation, Star always said "send it to Eagle for reprogramming", Eagle always said "Star specified their charge profile, not our fault" - "Who-dunn-it" BS! One thing i will give Eagle/Procharge, i saw a very low "outright failure/charger is inoperable".

Since you said 64 is a little high for cutoff on Trojans, is it ok to unplug it from the wall at 63.8? It seems to stay at 63.8 forever with the green light flashing (final stage).

[MattFX4]

You guys are seeing high numbers compared to myself. I haven't watched the voltmeter the entire time while it's charging but I'm seeing a constant 52.9 when the charger is off. I have a dpi 48v charger and 6 8 volt crown cr190's. I'm trying to break them in but first few days of use I have only used about 4-5% each day before plugging back up. Should I try to run them down further during the first few cycles?

[JohnnieB]

Originally Posted by MattFX4

You guys are seeing high numbers compared to myself. I haven't watched the voltmeter the entire time while it's charging but I'm seeing a constant 52.9 when the charger is off. I have a dpi 48v charger and 6 8 volt crown cr190's. I'm trying to break them in but first few days of use I have only used about 4-5% each day before plugging back up. Should I try to run them down further during the first few cycles?

By "when the charger is off", I suspect you mean when the charger is in float charge mode (only top green LED and bottom red LED illuminated) after the regular charge cycle finishes.

In that case, 52.9V is normal.

As for the amount of discharge during the break in period: You are only taking them down to about 95% SoC, so I'd take then down to about 80% SoC a couple times during the first two dozen cycles. Do it by driving further in the same day rather then letting the sit overnight without being charged.