I have a mountainbike with a rear X-Lyte 5 hub motor. I have six 12V 12ah SLA batteries (72V 12ah total). I recently got a new 40 amp immediate start controller. After about 3.5 to 4 miles of normal hybrid riding, the power suddenly cuts off. I have to wait a few seconds and it kicks back on for a few seconds. It then cuts out, and back on until I get home. This is really strange because even with my old 20amp controller would get me over 10 miles, even up a big long hill. I have pretty new SLA batteries. My voltmeter says all of them are ok. Is there something in the 40amp controller that is governing things or something??
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Sounds like a textbook case of the LVC (low voltage cutout) kicking in.
The batteries sag under the higher amp load, and the LVC cuts in. Then, they recover and you can start again. Keeps happening until you get home.
Only way to fix it is get bigger/better batteries, or baby the throttle (but then what's the point of the high-amp controller?).
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Ride the bike until you get the cutout problem, and do a short-duration load test on each battery with about 30-50 amps if possible. The voltage drop will clearly distinguish any bad batteries from the rest.
If none of them are bad, than the LVC is just set too high. But I highly suspect a bad battery because AGMs hold voltage pretty good throughout the discharge cycle, and unless you are hitting a really big hill, you probably aren't even going past 50% DOD.
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1. The controller gets hot, which is odd because that new 40amp 72v controller is supposed to have the upgraded mosfets that are supposed to handle the current.
2. One or more of the batteries certainly could be bad. I, however, have no idea how to do a load test. Do I have to buy some soft of load tester?
3. I will look at all the connections very carefully.
4. I used to have a 35amp 72V controller way back when. It never cut out. How do I know if this new controller is bad?
Patrick
1. How hot? If it's being pushed hard a lot, it's going to get warm regardless. I don't think it should be too hot to touch indefinitely, though.
2. It helps. But, you can also do it if you just have a multimeter. Clip the leads to the battery terminals and go for a quick ride down the street. Make SURE the leads can't touch, though. Not good.
4. I don't know if the old controllers had a LVC or not, so that could be why. And you won't know if it's the controller unless you check the batts.
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Sounds like it could be an overheating problem. Which controller did you buy, and can you open it up?
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Well, I went ahead a bought a load tester. All of the batteries are fine. The problem probably is that, in my infinite wisdom, I had decided to place the controller underneath a gortex bag with the chargers and batteries. I guess my rationale was to prevent the controller from getting wet. Anyway, I have now move the controller to the outside so it will breathe and be windswept. I guess next time I ride I'll see if this works.
I wonder if I can find out if I have done irrevocable damage to it??
Patrick
I have this controller: http://www.poweridestore.com/Crystalyte/40A72V-X-5-Motor-Controller
It is a 40A(72V) X-5 Single Speed Hub Motor Controller.
I'm not sure I would want to mess with it and open it up since it is brand new essentially. But yes, it can be opened.
Patrick
I doubt you hurt it. That might have been the overheat switch cutting in. The whole point of it is so that you don't damage the controller.
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Ok,
I rode this morning 9 plus miles to work, with the controller installed outside so wind can cool it. When I got 5.6 miles into it the power cut off again. Of course, I had 3.5 more miles to go - uphill. That's alot of weight to lug up a hill. It did the same thing, on for 2 seconds, off for 2 seconds all the way up. And by the way, I felt the controller many times and it was not hot to touch.
I know the batteries are fine, and that there is much more juice in them. I disconnected the Cycle Analyst just to make sure that it wasn't governing the controller. The power still cut out repeatedly.
This is a ride I used to do easily with my 35amp 72V controller. My 20amp 72V controller even did this ride without problem. I have to assume I got a dud. This 40amp 72V controller really sucks. I have no idea what to do.
Patrick
I would talk to the distributor and try to get a refund/replacement. But there is something I thought of.
Ride the bike until the controller cuts out. Than let the bike sit 1/2 to 1 hour without charging it. Than go for another ride, and see if it'll ride another 4-5 miles. This would help determine if its a LVC problem, or a heat problem. My bet is that it's a heat problem.
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I found that it is a LVC problem. It cut out when it went below about 55V everytime. I think the X-5 motor is too beefy and draws too much juice, or something. Either I need better batteries or get a lower-speed, higher-torque motor. This sucks because I can't be buying more stuff, especially when I already have batteries and a motor. Yuck...
Patrick
praskal,
What is the temperature where you are riding the bike? And how cold are the battereis? If the batteries are not cold, than I suspect a bad battery, and recommend a load test, as in my initial reply. 55v for 6 batteries is 9.16v/battery which is very low in the discharge curve in the spec sheet I linked below for B&B 12ah batteries. At a constant current discharge of 48 amps, when they hit 10v the capacity is almost completely used up.
I had a similar problem with my motorcycle. I would get about 4 miles, than the top speed would drop to about 40-45. I probably couldn't of gotten another mile. A load test right after a ride distinguished the bad battery very quickly.
If you can't determine that any of the batteries are bad while doing a load test with the batteries discharged to the point of the LVC, than consider what I initially posted below.
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This definitely sounds like my problem. Yes, I tested all the batteries with a load tester, but not during a heavy load during riding up a hill. It is possible one or more batts is bad.
Patrick