How can I disable sense wire on Powerwise 36V charger?

[wsettle]

I have a Powerwise 36V charger, 28115 G04, that I want to use on a 36V forklift.

I replaced the connector to a 2 pole anderson connector to match the forklift and when I plug it in, the charger won't charge the batteries. (relay won't engage)

I tried tying the sense wire to B+ and then to B- and the charger relay still won't click and engage. I searched threads here to find this information and have seen folks recommend both ways so I'm not sure which is correct.

If I jump the two black wires on the relay together, the charger will charge but I don't think it will ever turn off once the batteries are full.

Can someone tell me the correct way to disable the sense wire and based on what I've described, do I have a bad relay or control board by chance?

Thanks,
Bill

[JohnnieB]

Tying the sense wire to the B- terminal should have done the trick.
I'm not sure if tying it to the B+ terminal first took out the control board, but it might have.

Attached is a schematic showing the sense wire connected to the center tap of transform's secondary and eliminating the external sense wire. A service manual is also attached.

No, the charger will not shut off with relay bypassed.

To check control board, Plug charger output cable into forklift without the charge being plugged into an AC outlet. Measure the voltage between the red and black wires on the control board. The relay ought to click if the voltage is about 30V or above. (The forklift's battery pack energizes the relay to turn on the charger and has to be at or above the voltage needed to close the relay's contacts.)

[wsettle]

Thanks JohnnieB. I'll check it out shortly.

[wsettle]

I tried your suggestion and with 39V on the red/black wires of the control board the relay did not click so I have ordered a new control board.

[JohnnieB]

Originally Posted by wsettle

I tried your suggestion and with 39V on the red/black wires of the control board the relay did not click so I have ordered a new control board.

[wsettle]

A new twist. I gave the charger to a friend with the forklift that had a bad, built in charger, so some of the troubleshooting has been by proxy.

He tried a jumper of the sense wire to ground and it didn't work so I ordered the new control board. It came in today but before I installed it, I did as you suggested (that my friend thought he had done) and jumpered the sense wire to ground, with the charger unplugged from power, and I heard the relay click. So, I plugged it all back together and the charger works as it should from a charging standpoint.

We let if charge to 45.9V and it did not cutoff. I've read that the cutoff voltage is 45V +- 1V. I verified that the voltage of each battery was about the same and they were all around 7.6V and within .2-.3V of each other so I'm thinking that there are no "problem" cells. The batteries were gassing at this point.

So, do you happen to know what the approximate cutoff voltage would be of the charger? Does 45V +-1V sound correct?

I am betting the charger will cutoff eventually, since it was working fine when I put in storage several years ago, but what is the maximum voltage I should allow before pulling the plug on charger?

Also, there is one potentiometer on the board. Would that happen to adjust the cutoff voltage?

I really appreciate your help!

[cgtech]

Charge it up pretty good, unplug, replug in the morning & watch it throughout the day. Just because gassing is happening, doesnt mean it's not ok. If you see it going over 48v without shutting off, then be concerned. I think you are also charging batteries of higher capacity than the charger was designed for, so odd behavior isnt too alarming. These aren't a set of 6 T-105s right?

[JohnnieB]

Originally Posted by wsettle

A new twist. I gave the charger to a friend with the forklift that had a bad, built in charger, so some of the troubleshooting has been by proxy.

He tried a jumper of the sense wire to ground and it didn't work so I ordered the new control board. It came in today but before I installed it, I did as you suggested (that my friend thought he had done) and jumpered the sense wire to ground, with the charger unplugged from power, and I heard the relay click. So, I plugged it all back together and the charger works as it should from a charging standpoint.

We let if charge to 45.9V and it did not cutoff. I've read that the cutoff voltage is 45V +- 1V. I verified that the voltage of each battery was about the same and they were all around 7.6V and within .2-.3V of each other so I'm thinking that there are no "problem" cells. The batteries were gassing at this point.

So, do you happen to know what the approximate cutoff voltage would be of the charger? Does 45V +-1V sound correct?

I am betting the charger will cutoff eventually, since it was working fine when I put in storage several years ago, but what is the maximum voltage I should allow before pulling the plug on charger?

Also, there is one potentiometer on the board. Would that happen to adjust the cutoff voltage?

I really appreciate your help!

The charger's output is isolated from ground as is a golf cart's battery pack. I'm not100% sure if the battery pack of a forklift is or not, but the same safety issues apply, so I strongly suspect they are not grounded either.

The battery sense wire connects to the center tap of the transformer's secondary windings, which is B- (battery negative). If there any wires of any type, other than the AC power cord's green wire, connected to the charger's chassis, frame or case, disconnect it immediately.

The cutoff point for that type charger is traditionally 45V +/-1V, however that is the voltage as measured between the black (B-) and red (B+) wires on the control board. If the cables and connections between the forklift's battery pack and charger's control are less than perfect, the voltages at the two points can be different.

However, if the sense wire is truly connected to earth ground (AC power cord's green wire) inside the charger, all bets are off.

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

Gassing is both normal and good.

What are the make/model and AH rating of the batteries? The charger is specifically designed to charge 220AH deep-cycle batteries, but will work okay with batteries quite a bit smaller or a bit larger than that. The danger is too high of a charge rate for low AH batteries and the problem with high AH batteries is the length of time needed to charge.

From what I have found online, the batteries in 36V forklifts are huge, over a 1,000AH and the max output of a PW 28115 is about 18A, so it'll take at least 2.5 days to charge a 1,000AH pack from 50% to 100%.