DPI charger

[kojo]

Got a question about my DPI 48v charger. What should my dvm read while charging? I've never really checked it while charging, but last night it was 61.2v, is that the norm? Plus, I've never felt the warmth of it until last night and it was a little warm, not so much that you couldn't keep your hand on it, but warm nonetheless. I'm assuming that they probably get warm anyway though. I've only had it for maybe 3-4 months and usually when we ride it and come back, I just put it back on charge and leave it alone till the next day, most of the time we ride at night anyway. Also, what's the avg. charge time before it cuts off(I know this varies with different batts.} It was charging for 61/2 hrs. before I went to bed and hadn't switched to float charge yet so I just unplugged it and went to bed. Thanks for any help.

[JohnnieB]

Basically, the charge time mostly depends on how far the batteries have been discharged and the output current of the charger, as well as some other factors.

For example: If you have a 170AH 48V pack (Six T-875 batteries) and discharge them to 60% SoC, you've taken 68AH out of the pack. Battery charging isn't 100% efficient, so you have to put bat about 125% of what you take out, or 85AH. If you charged at a constant current of 17A, it would take about 5 hours to recharger the batteries. However a 48V DPI puts out about 17A during the bulk charge phase and the amps taper off when it goes into the Absorption charge and Finish charge phases. In addition, the DPI doesn't terminate the regular charge sequence and go into the float charge mode until the ON-Charge voltage stops climbing (dV/dT technology), so you can just about double that time estimate.

The constant voltage during the Absorption phase is from 56.4V (Trojan) to 60.0V (US Battery) depending on the battery brand selected, and the finish voltage climbs higher than that, so 61.2V is in the ballpark, but I would check the electrolyte levels.

You probably caught it right before it switched over to float charge.

I'd just plug it back in and let it complete the charge cycle and go into float charge.

[kojo]

Thanks JohnnieB, I just plugged her back in but, I checked with the DVM before I did, and it was 51.9v, it had sat for probably 11-11 1/2 hrs. By the way, yours gets fairly warm doesn't it? I'll go out in a bit and take my laser temp. checker and check the temp. on the outside of the charger(didn't think about that). Thanks again buddy.

[kojo]

Almost forgot, if it makes any difference, I've got 8 6v us 1800's (208ah).

[JohnnieB]

Yes, my DPI chargers do get a bit warm. Never measured the temperature, but my guess is about 110° or so.

BTW: You'll probably get a more accurate temperature reading on the black label rather than the shiny case.

Yes, Make/Model of batteries makes a difference. US Battery mode has the highest voltages.

An at-rest voltage of 51.9V for fairly new US Battery batteries sounds about right.

[kojo]

Thanks JohnnieB.

[yurtle]

FWIW,
Anything that has vents on a heavy iron core transformer WILL get hot. Electronics don't weigh anything, but a coil and core transformer weighs a ton (exaggerated).

Don't sweat it.