Power wise charging

[jmevans_2]

I am following this because I have a similar issue. My cart is boiling the batteries before the charger cuts off. I checked the voltage yesterday near the end of the charging cycle (could hear my brand new T-105 batteries boiling) and got 49.2V. I snatched my charger out and don't plan to use it again until I follow the same troubleshooting steps you have. You said your replacement control circuit was inexpensive, where did you buy it from? Is it aftermarket or OEM?

My cart is a 2007 TXT Series 36V with T-106 batteries and a PowerWise QE charger.

[JohnnieB]

Originally Posted by jmevans_2

I am following this because I have a similar issue. My cart is boiling the batteries before the charger cuts off. I checked the voltage yesterday near the end of the charging cycle (could hear my brand new T-105 batteries boiling) and got 49.2V. I snatched my charger out and don't plan to use it again until I follow the same troubleshooting steps you have. You said your replacement control circuit was inexpensive, where did you buy it from? Is it aftermarket or OEM?

My cart is a 2007 TXT Series 36V with T-106 batteries and a PowerWise QE charger.

A Powerwise QE is a very different animal than the Powerwise 28115 Skip has. The QE is more or less a throwaway when it fails.
Please note that I said "when it fails" rather than "if it fails". The 36V QE is a high failure item and is not repairable.

That said, your QE charge may be operating normally.

The "boiling" you hear is called gassing and is a normal occurrence when charging cart batteries.
When an electrical current passes through the battery's electrolyte, the water in it decomposes (electrolysis) into hydrogen and oxygen gases and the gases bubble to the surface, causing the sound you hear, there is no heat involved.

If this is the first time you've charged your new batteries, the charge cycle may last up to about 20 hours so the on-charge voltage may get upwards of 50V.

Clean the auxiliary contact in the charger's output plug and the outside surface of the negative terminal in the cart's charge receptacle, then run the charger until it shuts off automatically, or the on-charge voltage exceeds 50.1V.

[skipsmith521]

Took some voltage readings and not what I was expecting...

During a charge took a reading with my handheld DVM and pack is 39.4.

Took reading of the black and red wire inside charger and it is was at 40.1

Not sure why the reading in the charger would be higher than the actual pack charge.

Thanks for any help.

Skip

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[skipsmith521]

I should also mentioned...

I have not try to clean the contacts...

Would a dirty contact cause the reading in the charger to be 7 tenths higher than the pack charge?

If the typical cut off for the charger is around 45.5, this would mean my pack is really getting charged up to 46.2...assuming the charger cut off is working.

Does the charger have a hard set number that it turns off at...or is it sensing something else coming from the batteries and the cut off point can vary beyond 45.5 ?



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[JohnnieB]

I'll answer the easy question first.

Your Powerwise model 28115 charger is the Ferroresonant Transformer type with a control board, which terminates the charge when a specific on-charge voltage is reached. The fixed voltage chosen by those that collaborated on the design, is 2.5VPC (Vols per cell), which is 45.0V for an 18 cell 36V battery pack, but there was a fudge factor tossed in to compensate for manufacturing wiggle room and the end result was 45.0V +/- 1.0V, so we typically say that type charger will cutoff in the 44V to 46V range.

The charger's control board does not actually know what the cart's battery pack voltage is, it only knows what the voltage is between the red and black wires and if the control board is working properly, it will shut off the charger when the voltage between where those two wires connect to it, is at 45.0V +/- 1.0V.

Now for the stuff that will make your head spin.

If there is excessive resistance in the heavy (8Ga) battery charging circuit, or the thinner battery sensing circuit, the voltage between the red and black wires on the charger's control board can read higher or lower than the actual battery pack voltage, depending on which circuit the excessive resistance is in. If it is in the charging circuit, the control board will see a voltage higher the the actual pack voltage and if it is in the sensing circuit, it will see a lower voltage.

The way the two circuits react to excessive resistance may appear to be diametrically opposed, but they both doing the same thing, only our viewing perspective changes.

The total voltage of a series circuit is the sum of the voltage drops in that circuit. When amps pass through resistance there is a voltage drop across that resistance. When you measure the voltage of the battery pack while it is being charged, you are be measuring only the center portion of a series circuit, so the applied voltage (measured at the center tap of the transformer and the heatsink) will be the pack voltage plus the voltage drops on the wires and connections between the battery terminals and the heatsink/center tap.

On the other hand, the battery sensing circuit effectively measures the voltage at both ends of the series charging circuit and any voltage drops in the wires of the sensing circuit is subtracted from the total voltage.

The 0.7V difference you are seeing is the net sum of the voltage gains and loses in the two circuits caused by the undesired resistance in both of them.

[skipsmith521]

This information is actually very interesting...

At this point in the process...should I just let it charge?

It seems I would really know if the charger is working if I can get a reading of the pack charge when the charger shuts off and the pack voltage would read between 44 and 46 ? Does that sound correct?



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[JohnnieB]

The charger is working, it just doesn't seem to be quite working right.

Yes, just let it charge and see where it cuts off at. (If you have a DVM with a Min/Max function, it is easy to find the max voltage reached)