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Old 06-03-09, 10:11 PM   #1
flash_man
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Help diagnose my battery problem

I have the amped rear kit and a PING 48v 12ah battery. Yesterday after riding about 5 miles I noticed that I was hearing a rumble sound which I thought meant that one of the phase wires was loose, and my speed was dropping. (A few weeks back 2 phase wire connectors had melted so I replaced them with Anderson connectors.) I checked the connectors and one of them did seem to be loose and not seating well. Pressed them together and then the motor rode normally for a small bit then began rumbling and driving slow again. Gave up and tried riding without the motor, but now it was humming and dragging, and I believe I was essentially pedaling a generator. So I disconnected all 3 phase wires and the riding resistance went back to normal.

Now the charger stays green, indicating fully charged. But I switch the motor on and all 3 throttle lights turn on (this means there is more than 36v) but then quickly turn to Red (which means the voltage is below 26 volts or something in that range.) I measure the battery voltage and it reads 1 volt, but slowly climbing back up. After 2 minutes, it's back at 55 volts. The motor won't budge.

Thoughts? Are there more tests I need to run to diagnose the problem? Why would the battery instantaneously drop from 55 volts to almost 0? I'm guessing cells are damaged within the pack.

Eric
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Old 06-03-09, 10:34 PM   #2
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The fact that 2 of your phase wires melt probably means you have a short somewhere. Do you have a fuse in your battery line?
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Old 06-04-09, 06:04 AM   #3
similor
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sounds like ur controller is wrong.Measure the resistance of 2 phases of controller,if low than 500ohm,it's can be sure to be changed.
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Old 06-04-09, 11:46 PM   #4
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Yes, I added a 30 amp fuse off the positive battery terminal.
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Old 06-05-09, 11:53 PM   #5
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Ping told me to leave it on the charger 24 hours, which I did. The symptom is still there: I turn on the switch at the throttle and the battery voltage drops to almost zero volts. I turn the switch off, and the battery voltage slows back up (58v, fully charged) within about 2 minutes.
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Old 06-06-09, 07:11 AM   #6
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Sounds like you are using the idiot lights to determine voltage: have you confirmed with a volt meter that the voltage is indeed dropping to near zero?

If you have have a 30A fuse in the circuit and it's not popping then I doubt it's a short circuit. If the circuit is drawing enough current to truly cause that much voltage drop, something would be getting real hot in a hurry.

Sounds like a battery problem to me.
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Old 06-06-09, 03:45 PM   #7
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I am using a fluke multimeter. I only mentioned the idiot lights because I understand the BMS would cut off before the voltage got low enough to trigger red light. Could the BMS be shutting off the voltage?

After leaving the charger on for 24 hours to balance the cells, the voltage still drops to near 0 when I turn the switch on, then climbs back to 57 volts within a few minutes after I turn the switch off.
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Old 06-06-09, 05:39 PM   #8
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"...2 phase wire connectors had melted....." How many AMP could do this?I m sure ur battery is ok,but ur controller is in trouble.When the battery worked at the high current,the volt will drop immediately.
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Old 06-07-09, 08:56 AM   #9
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You raise a good point about the BMS, I hadn't thought of that. I know the BMS has the job of making sure a battery is neither overcharged or overdischarged. Considering the discharge side of things it may simply use the voltage to guess a "close enough" state of charge. If you had a short, that could drop the voltage enough to cause the BMS to dial out the battery and not blow the fuse.

Do you have a bench power supply with a current limiter you could test with?

Another option is using a power resistor to draw a nominal amount of current from the battery, say a 10 ohm power resistor from Radio Shack, which would pull close to 5 amps, just to see if the pack is up to snuff. At 230 watts the resistor won't last very long unless it's rated to dissipate that much heat, but they're cheap.
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Old 06-07-09, 12:55 PM   #10
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Since you have a multimeter, why don't you put it in current measurement mode. Connect serially. The controller should not draw any amps with no throttle. At worst you blow the 9 amp fuse in the meter.
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Old 06-07-09, 03:25 PM   #11
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Quote:
Originally Posted by snowranger View Post
Since you have a multimeter, why don't you put it in current measurement mode. Connect serially. The controller should not draw any amps with no throttle. At worst you blow the 9 amp fuse in the meter.
Not saying my controller is typical but, when fully discharged, it has enough inrush current to spark the PowerPole disconnect. I'd suggest a slight modification, tap the circuit on momentarily to satisfy the inrush, disconnect, then meter it as snowranger suggested.

ps. it's a PITA to replace the fuse in my Fluke
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Old 07-09-09, 12:48 PM   #12
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Quote:
Originally Posted by misslexi View Post
ps. it's a PITA to replace the fuse in my Fluke
Good point here, it can also be EXPEN$IVE! There are online sources for the 15A 600V fiber fuse most newer Flukes use, but to find one locally might not be so easy. Even some of the larger electronics supply sites charge ~$20 for this fuse!

I agree with those who have suggested you test the speed controller. If your battery is fine on the bench (probing the battery leads with your DMM) then there is a good chance this is related to the problem you had with your phase wires. Have you tried opening up your speed controller to check for obvious signs of damage/heat?
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Old 07-09-09, 08:51 PM   #13
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A better way to measure current would be to put a low resistance, few ohms, high power resistor in the supply circuit and measure the voltage across it with your Fluke.
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Old 07-13-09, 04:17 PM   #14
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So I've been doing some more testing:
- I disconnected the BMS altogther from the battery. Now the idiot lights stay on, but applying the throttle does nothing. If I flip the throttle on and off, I may get a little "blip" like the motor wants to engage. I now think the problem is not the battery or BMS.
- I opened up the speed controller and there is no obvious signs of damage. Nothing looks burned. No fried smells. I'm wondering if the controller has been damaged in a way that isn't obvious.
- I tested continuity through all connectors. Everything is making good contact. No shorts.

Phase wire connectors had overheated previously and melted and I had replaced them with Andersons. This new problem began in the middle of a ride, with the power cutting out intermittently, then not working at all. Now I'm wondering if the same overheating problem occurred elsewhere in the circuit. My next guess is that there may be damage to the phase or sensor wires inside the motor. It looks like I need to open up the motor.

Any other thoughts? At this point, troubleshooting would be easier if I could switch out known working components. I might see if I can swing by Danny's shop for some of his expertise.

Eric
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Old 07-23-09, 07:28 PM   #15
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what is the voltage across each cell in your battery pack? The reason I ask is because a battery pack that is extremely out of balance wont charge because of the charged cells, and wont supply because of the discharged cells.
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Old 07-27-09, 01:15 PM   #16
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Each cell is exactly the same, around 3.5 v. The pack seems balanced.

Danny at Amped says that the speed controller is fried, probably when the phase wires melted. I need to swing by the shop to swap one out for testing.

What do speed controller do folks recommend for a 48v 500watt system?
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Old 07-28-09, 02:08 AM   #17
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Sounds like your controller was broken when the 2 pahse wires melted. Get a new controller to try. Before you use your new kit please make sure the controller is connected properly with the motor. when you get a wrong connection there will be 2 posibile results:

1: the motor doesn't work;

2: the motor works, but the motor and controller becomes VERY HOT shortly within several minutes. If you donot notice this for a period something such as controller might be burned.

You could switch on the system and use throttle for several minutes when motor works, then use your hand to touch the motor and controller to check if it becomes obviously very hot.

Feel free to try different combinations of the pahse wires and haul wires to connect with the motor (surely only motor pahse wires to controller pahse wires, and motor haul wires to controller haul wires), this will not harm your motor if you donot ride it on the way for long time. Hope this helps.
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