Battery Pack Range Reduction

Drive motor and electrical issues

Re: Battery Pack Range Reduction

Postby Bushman » Sat May 18, 2013 2:58 pm

Mark,

Checked all of the batteries with a meter and don't seem to have any bad cells. I like to think that deep discharges like the ones ive been going through help the batteries become even charged once the cycle is complete. Definitely seems like we're undercharging and i need to adjust the setpoint on the Landis. I think the instructions say it is set at 38V now, but according to you, it's only about 0.4V lower than what the resting voltage needs to be. We may need to go higher than that still, because I don't think the charger even gets up to the 41-42V level that would indicate the battery load has reduced and are charged. So, first things first, I'll pull the Landis out and set it to 6.37 * 6 = 38.4 Volts and try it there. I have a real nice, vintage Heathkit power supply and brand new, Tenma benchtop multimeter to use. Makes doing these kinds of things fun, lol.

Nice setup Jeff. Anyone who installs these should consider keeping the timer switch or installing some sort of switch so that the cord is not backfed through the charger in any way. Found that out the hard way after trying to save time on putting one in. The HOT stab on the AC cord touched one of the battery posts with the key on, the tractor started driving. Wierd stuff. I plan on getting some plastic cord covers and putting in a switch.

Thanks guys.

Chad
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Re: Battery Pack Range Reduction

Postby Jeff Antonucci » Mon May 20, 2013 10:20 pm

My batteries were measuring 6.26 volts each fully charged, so not "fully" charged I guess. Chad - I also have a 15A fuse on the AC side.
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Re: Battery Pack Range Reduction

Postby Bushman » Tue May 21, 2013 3:52 pm

All,

I had purchased ten of these charge controllers from Harry. After going through all of them by checking the setpoint and readjusting them all to about 38.5V, NONE of them were set to the 38V as stated in the instructions. In fact, most were closer to 37.5V and the rest were a little under 37.75V. My benchtop multimeter is accurate to +/-10mV, so I know that my readings are good, no matter what power supply is used. I am still experimenting with setpoint and range, but if anyone is going to purchase a controller from Mr. Landis, I would suggest asking him to increase the setpoint to at least 38.5V, if not a little higher to err on the side of caution. I'd rather have a little more range than less. It's been frustrating enough having to charge 2 or 3 times to finish the yard.

Also while testing, I was checking for relay contact to get an idea of when the "coil" actually energizes. Got no indication on my meter set for continuity, and then realized this is a solid state relay. That also means that the contacts are never really off and would explain my cord arcing problem. Therefore, always use a switch between the AC cord and charge controller to prevent leakage. I installed the stock timer and only used the start switch on it to enable the controller. Proof of these leakage currents was also found by my wire from controller to transformer. It had gotten caught up in the toaster again and actually served enough current through the controller to burn up the solid state relay. Luckily had another controller to install and isolate via the timer switch. Also shortened the wire that was getting caught and will eventually make a better mount for the controller.

Lots of lessons learned on this problem and will continue to post as I play with the setpoint.

Chad
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Re: Battery Pack Range Reduction

Postby mfrerking » Tue May 21, 2013 6:39 pm

Jeff,

Your measured voltage of 6.26 is about an 80% charge. Check out this link for a chart:

http://ddmotorsystems.com/ElectricVehicles.php#FAQ9

Chad,

When you checked your battery voltage, was it after they sat for a few hours with no charger running?
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Re: Battery Pack Range Reduction with Landis

Postby Bushman » Wed May 22, 2013 2:04 pm

Thanks for that link Mark. I'll definitely bookmark that chart for future reference. Do you know if those are open-circuit values? Because right now I'm using them as a reference with them in the tractor (obviously) and disconnect on, which would be a small, relatively negligible load.

When I got home from work last night around 5:30, I metered each battery and the whole pack. Not sure how long the charger had been off since the last cycle from the controller, but individual readings were 6.39, 6.42, 6.40, 6.37... all indicating a 100% charge according to D&D's chart. The overall pack was sitting between 38.4 and 38.5V, also indicating 100% charge. So I set off to finish the yard and it seemed as if the tractor was running as expected after about an hour. I was doing a lot of trimming under pine trees the last half hour or so, but will have to post again after starting the yard from scratch. Plugged the tractor in after finishing and at 10:30PM when I closed up the garage, the controller had stopped cycling to about every half hour already. Hoping for better results next week, as i'll be out camping through Monday.

I will offer this to others that may not have the equipment or know-how, but for those that are running controllers and need them adjusted, I would gladly do it for free if you pay for the shipping back and forth.

Thanks everybody. I hope this helps more than just me.

Chad
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Re: Battery Pack Range Reduction

Postby mfrerking » Wed May 22, 2013 6:24 pm

Chad,

From what I have read, batteries have what is called a "surface charge" that has to dissipate after being charged in order to get their true resting state of charge.

Not sure if you can simply run the mower deck for a few minutes to eliminate the surface charge or if you have to let the battery rest for a number of hours to get the best reading.

The most accurate way of determining battery state of charge is to measure the specific gravity. This will also tell you if one or more of the battery's cells is weaker or less than fully charged. The weakest cell in the pack is the weakest part of the pack. If one cell gets out of balance with the other two, this is when you would want to over-charge (boil) the battery to bring the cells back into balance.

This one of the reasons I recommend modern 3-bank chargers. Because of the various 12 -18 volt taps off of the battery pack, some of the batteries are being drawn from more than others. If you do not over-charge the whole pack (41-42 volts), some of the individual batteries may not be brought up to full charge. Also, internal resistance may allow some batteries to take up a higher charge (greater than 6.36 volts of the 38.5 volts the whole pack sees from set point), while others may remain below this.

Glad to hear you are up to at least an hour of run-time.

It would be good to do some additional measurements as the battery pack is discharged to get an idea of when you are down to a 50% Depth of Discharge (DOD). You will get the longest life span from the pack if you do not consistently discharge greater 50% DOD.

This will change as your pack ages because Amp/Hr capacity goes down as the battery ages.
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Re: Battery Pack Range Reduction

Postby roberttroll » Wed May 22, 2013 6:36 pm

Yes - old school way to test a fresh off the charger battery is to connect it for a min to a car headlight. That gets rid of the surface charge.
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Re: Battery Pack Range Reduction

Postby Bushman » Thu May 23, 2013 2:54 am

Understanding the idea of surface charge, I disconnected the charger today for about 5 hours and took a reading before coming in the house. Batts were down to 38.1V. Not sure what that means, but that's still pretty close to 100% charge according to the chart at D&D. It may be that you are correct Mark, in that the charge controller setpoint should be higher in order to allow the batteries to become overcharged enough to equalize. Even raising the setpoint to 39V may be enough to do that, although the charger may run more often to maintain that setpoint.

At some point I would like to install a digital meter to display pack voltage, however, in order to be accurate you would have to stop mowing/plowing to get a good reading in terms of DOD. Problem is, I have so many other things to do and not enough play time to do the projects that would benefit the tractors. Although, more time is opening up for me, and I plan to soon start some restorations (maybe).

Jeff, have you adjusted your setpoint yet? Would like to know what yours was set at originally...
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Re: Battery Pack Range Reduction

Postby Bushman » Thu May 30, 2013 2:56 am

Update: Doesn't seem like bringing the setpoint up to 38.5V really gave me much more range. Still had to stop and charge a few times in order to finish the yard, of which I still didn't get to finish trimming underneath our pine trees. I bet I don't mow much more than an acre all together. 1.25 acres at most. Not exactly sure what to do next, although I can't keep running it like this, and I bought 10 of these things so need to figure out a good setpoint to give enough range and equalization without boiling them too much. The controller never kicked the charger on after finishing the yard, but the small LED was on. Not sure what's up with that, but the disconnect was on as usual and it should have been working/charging. I hope these relays aren't giving me trouble. This would be the second one to go out.

Any suggestions would be great. My step-dad uses an automatic EZ-Go external charger, but I can't seem to get him to remember to check the battery level after it finishes to compare setpoints.
Chad
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Re: Battery Pack Range Reduction

Postby roberttroll » Thu May 30, 2013 1:02 pm

If the batteries have been undercharged, they will need to be cycled a few times. I would remove the charge controller and charge with the stock setup or a different charger like your dads.
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