Over-Unity achieved !

The other day I road my bike to the store, just like I do most days. It's almost a 5 mile round trip. When I left, the at rest pack voltage was 80.5v and when I returned home the at rest voltage was 80.7v, indicating that my pack had more energy than when I left. I've seen this on several occasions though not after that long a distance.

My cruising speed was my normal 35-40mph.
I did not charge the pack while I was out.
No, I didn't pedal at all. In fact, all propulsion was provided only by the measured batt pack on the bike via the my usual hub motor, which consumed its usual 200-250wh for the trip.
No, I don't have solar panels on my ebike, not yet anyway.
No connections were loose or any change made in the ebike, so the entire pack was connected for both measurements, and there was no change in configuration in the pack. I just got on, turned on the key, took off, and returned 30-40min later just like I always do. I just happened to notice the voltage being high when I got home, so I checked it again after a few minute rest.
The same multimeter took both measurements, so there wasn't some calibration difference.
No gale force winds blew me there and back. The day was near calm.
It was a round trip ride, so no net change in elevation, therefore regen braking isn't the cause. In fact, the max/min elevation difference over the route is less than 15m.
No, I didn't travel through a wormhole and get back before I left.

Anyone want to take a shot at the cause? I believe it's an effect we should all take into consideration with our ebikes.

John

BTW - I don't believe in over-unity, though that doesn't preclude the possibility of harnessing some as yet unknown energy or using a yet unknown method to capture known energy in the environment. I this case, I did neither. 8)

Temperature.

If your battery got warm on the trip, there could well be a little higher voltage at the end than before. Did you have it inside (air conditioning) before you left? Did you park it in the sun and is the battery pack a dark color?

Cameron

oldpiper said:

Temperature.

If your battery got warm on the trip, there could well be a little higher voltage at the end than before. Did you have it inside (air conditioning) before you left? Did you park it in the sun and is the battery pack a dark color?

Cameron

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What He said.

No It's gotta be over unity man. Shhh. don't let the feds catch ya or they'll confiscate your stuff and we won't get to reap the benefits of your discovery.. 8) 8)

oldpiper said:

Temperature.
If your battery got warm on the trip, there could well be a little higher voltage at the end than before. Did you have it inside (air conditioning) before you left? Did you park it in the sun and is the battery pack a dark color?
Cameron

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Yep. In the shade in the carport is nice and cool in the morning, but even mid morning the sun is brutal here. This was about 9am and the sun was hitting one side of the gray duct taped pack at about a 90° angle. Even just the 15 minutes I was parked at the store was enough to warm the pack considerably. While riding is never an issue because there's enough air flow, but I think parking a freshly charged pack in the sun for a long period of time, especially covered in something dark, could be a serious mistake.

I charge mine quite conservatively, so I'm probably safe, but imagine a big lipo pack charged to 4.2v/cell in a cool garage, and then park it in the sun.

maybe that was today in the world,my leaving voltage was 54.2 and my return voltage was 53.7,i checked 4 times in a half hr because i thought something was wrong,cuz im a regen noob.i rode across a hilly town and back,im guessing 13kms.with regen.but i didnt zero out,thats pretty cool.
perhaps a bad cell boosting the overall voltage,iirc that happened to me a few years ago.maybe this will continue ..

not being in one of the bike subforums,
i initially thought 'over-unity achieved' was referring to opposition to obama.

Wind?

Toorbough ULL-Zeveigh said:

not being in one of the bike subforums,
i initially thought 'over-unity achieved' was referring to opposition to obama.

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Sorry to disappoint. That would be like making fun of the intellectually handicapped, and where's the sport in that? 8)

Did you came home with the same bike you left?
:lol:

JennyB said:

Wind?

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No, as stated in the OP it was near calm. In fact, a lack of significant wind is probably a requirement.

HAL9000v2.0 said:

Did you came home with the same bike you left?
:lol:

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No, one ebike ridden for the round trip. Everything identical other than the 20lbs of groceries, none of which were batteries.

And it wasn't 20lbs of lemons?

I have only run into over unity once in my life. Specifically FCR is the mass of the food eaten divided by the body mass gain, all over a specified period of time. FCR is dimensionless, i.e. there are no measurement units associated with FCR. Salmon are typically 4 to 1. We had a salmon farm with a 1 to 1.1, one pound of food, 1.1 pound of flesh. Impossible? No, feed was swimming into the pen and being eaten!
What triggered the memory is the government comment. Ocean ranching is illegal, except for clams and oysters. Don't let the government find our you are capturing free electrons.

HAL9000v2.0 said:

And it wasn't 20lbs of lemons?

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Nope. In this context I would consider lemons to be batteries, and that would be a change in the pack anyway. Plus, we have 2 lemon trees and never need to buy any lemons.

I've measured the tempco of a LiFeP04 cell at 50uV/degC (single cell, from 23C-40C).

I don't know what your pack consists of, so lets assume a hypothetical 22 cell series connection and a 20C temperature rise.

50uV/degC * 22 cells * 20C = 22mV

Your pack Voltage rose by an order of magnitude more than that. Maybe your cell chemistry is different and has a much higher tempco than the one I was looking at... or maybe your meter was sitting in the sun as well?

busted_bike said:

I've measured the tempco of a LiFeP04 cell at 50uV/degC (single cell, from 23C-40C).

I don't know what your pack consists of, so lets assume a hypothetical 22 cell series connection and a 20C temperature rise.

50uV/degC * 22 cells * 20C = 22mV

Your pack Voltage rose by an order of magnitude more than that. Maybe your cell chemistry is different and has a much higher tempco than the one I was looking at... or maybe your meter was sitting in the sun as well?

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At what charge status did you test the LiFePo4 cell(s)? At full charge I would expect different results, though I may be off base.

My pack is a well used LiMN pack 20s and about 20ah. I doubt the pack saw anywhere near 20°C temperature change, because it started at about a 20°C ambient temp, and didn't sit in parked in the sun for more than 15 minutes. I'm sure I've seen a full volt increase in pack voltage just sitting in the sun, though I generally try to avoid that. Maybe tomorrow will be calm and I can intentionally park it in the sun and see what the voltage does.

Neither measurement was in the sun, but would temperature significantly affect my multimeter?

John

Pretty interesting. I suspect temp played a role, but you'd think 5 miles would have used up any of that difference. I have seen REALLY cold lifepo4 drop a lot of voltage, then perk up a tiny bit when discharging them warmed it back up. But I never saw it come back to the house higher than I left. Like many perplexing results to an experiment, I suspect this one has more than one cause. Something going on with the quality of the contact you made with the voltmeter probes perhaps also ? So for some weird reason you had a tiny bit of resistance on the first reading?

John in CR said:

At what charge status did you test the LiFePo4 cell(s)? At full charge I would expect different results, though I may be off base.

My pack is a well used LiMN pack 20s and about 20ah. I doubt the pack saw anywhere near 20°C temperature change, because it started at about a 20°C ambient temp, and didn't sit in parked in the sun for more than 15 minutes. I'm sure I've seen a full volt increase in pack voltage just sitting in the sun, though I generally try to avoid that. Maybe tomorrow will be calm and I can intentionally park it in the sun and see what the voltage does.

Neither measurement was in the sun, but would temperature significantly affect my multimeter?

John

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Good question. As I recall, it was a fresh cell that would have had only a 33% charge on it. I certainly wouldn't rule out the possibility that your cells behave differently. When you get down to the details, different chemistry cells do seem to behave quite differently.

As for the multimeter, many (most?) are specified within a +/-5C temperature window from calibration and may have an additional tempco term that needs to be factored in outside of that window. For the case of a relative measurement (like yours, where the difference is more significant than the absolute value), it's always a good idea to keep that error term in mind since temperature is the main contributor to accuracy drift after calibration.