Where to start? Sudden Lack of Power

[LI-ghtcycle]

Hello, I'm noticing a sudden and significant loss in power (only about 20 MPH on the flats instead of the normal 24 MPH even with a head wind), what I can tell you is there is NO abnormal voltage drop, all batteries have nominal resting voltage(52 Volts), and only the nominal 1-2V drop depending on load.

*** Note *** I also wanted to add that I still have the same no-load speed, 31.4 MPH, so I'm still getting that same no-load speed, I'm only noticing the difference under load.

I have only noticed this problem the last 2 trips, and the only thing I have changed is I added a switch, however, I noticed the power drop the day before the new switch was installed (this switch simply isolates the controller side of the wiring from the watt meter) and amp draw is nominal as well.

I have heard of many people eventually having trouble riding in the rain with thumb throttles shorting/malfunctioning. I have once before noticed the throttle get a little "glitchy" (cutting in and out as the throttle is increased) but it never lasted long, and that was weeks ago, and I have run in the rain many times since with no problems.

I'm no electronics genius, but I have learned to diagnose problems with simple car electrical systems, and I am a plumbing repairman by trade, so if anyone has some basic things I can test to try and isolate the potential problem, please let me know.

 

[dogman dan]

Could be rust in the hub. Does it turn freely still like the bearings are ok? This one is wierd. A voltage drop from cold weather would make sense, or a cell going bad. Same thing for the other wheel, it turns ok? No low tires? Only other thing I can think of is you gained 30 pounds

In mid winter my ride home slows down 5-10 mph, but the reason is obvious. 2 mph for cold batteries and 7 more for the 15 mph headwind. In spring the wind will strengthen and turn 180 degrees and I fly home.

 

[LI-ghtcycle]

DOH!!! Maybe too many donuts!

J/K hehe :lol:

I have covered all that you mentioned, and other than the 30lb plutonium rod that managed to fall into my pocket at work the other day , I haven't noticed any unusual added weight , or resistance to the motor turning, and I always "pre-flight" my bike, meaning air pressure, axle & spoke tightness, and making sure the handlebar is secure each ride.

The only changes I have made recently are a different 48T chain-ring up front, and adding a "to the controller" switch (already tested and has VERY low resistance) and filling the tires with calcium ( j/k :lol: ).

I wish there WAS something drastic that happened recently to explain this loss of power. If anything, my last 2 rides have been in warmer and less windy conditions (previously low 40's with rain and now low 50's and dry) :? :? :?

I'm really hoping it's not a weird controller issue, maybe something got wet and just needs to dry out ... I wonder if that could be the case with my controller. :?

 

[liveforphysics]

Measure the voltage between your throttle ground, and throttle signal wire. Measure them near where they enter the controller.

 

[dogman dan]

True, the throttle is about all that's left. or the wires to it. A shunt melted on the controller would do it I suppose, but I never heard of that happening. Bad connector from battery to controler causing a voltage drop? I'm totally guessing for sure here.

 

[Dray]

How many amps is the switch rated for? I did this on my trek and it also lowered my speed under load as the switch was unable to put out the amps under load.

Also a dead or dieing cell will do the same thing under no load it will go the same speed but once under load it will be your weakest link.

D.Ray

 

[LI-ghtcycle]

Thus far I have tested some batteries that seem to be taking less of a charge (all well above nominal, just not as high as the previous average of 29V or 3.625V per cell, now to 27V or 3.4375V per cell) I went inside one of these batteries that wasn't seeming to take as high of a surface charge and found it absolutely perfect, every cell was at exactly 3.4V, so I don't think it was a balance issue, or a weak cell, but I have a theory that maybe the batteries had gotten colder than I realized over-night in the garage (maybe 35 F) and I used my bike with good results on a 42 mile trip in the dark & wet, but since I still don't have my new "cycle" computer, I couldn't see my speed, and since it was such a long trip, I used the batteries very sparingly, and achieved 2.7 W/mile, only using it on the 3 major hills and a little at starts & stops in traffic, but only at an average speed of 12MPH, and any hill I could comfortable use pedals alone, I did.

The switch is rated at 250v/15 amps or 3750 Watt if I am understanding that correctly, but I had the trouble for the first time the day before I installed the switch.
I have checked the phase wires and I did discover a plug from the throttle that was unplugged, but that had to happen when I took apart the wiring harness, I have an old inner tube wrapped around it to water proof the plugs.

Today I will take it around and see if after charing & storing the batteries indoors if it will make the difference. Hopefully this will just be a case of my not realizing how cold it had been over-night.

 

[amberwolf]

250V is the AC rating, though, for how much voltage AC can be across it during make or break before arcing might compromise it.

15amp is also an AC rating, and may be lower for DC if the switch has separate ratings.

That said, the switch is unlikely to be your (primary) problem if it started before installing it.

Cold batteries definitely can have problems delivering full current and/or voltage, less so with LiFePO4 than say, SLA, but potentially a cause of your problem. Just be careful when charging it that they're not cold then, too--damage can occur if they're charged at temperature extremes the same way you charge them at room temperature.

 

[TylerDurden]

Static voltage metering is not always sufficient for determining battery "health".

Testing voltage under load should also be done. Connect a sufficient load ~25A-50A and meter the cells. You could connect a resistive load like a small toaster or a bank of tungsten lamps.

 

[nicobie]

This has helped me alot.

Static voltage metering is not always sufficient for determining battery "health".

Testing voltage under load should also be done. Connect a sufficient load ~25A-50A and meter the cells. You could connect a resistive load like a small toaster or a bank of tungsten lamps.

 

[heathyoung]

Measure the voltage across the terminals of the switch to determine its voltage drop (and hence resistance)

 

[LI-ghtcycle]

Well, I'm happy to report that today the bike performed normally, and maybe I just need to stop charging batteries in the garage (it's usually about 50F) and just do it in my room, I noticed that the "low" battery packs charged right up to the normal 29+ volts once I had them stored inside.

Sorry for the false alarm, and thanks for all the advice! 8)