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Message from discussion Anti-regen Rides
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PGrace  
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 More options Sep 20 2007, 11:34 pm
From: PGrace <mentul...@gmail.com>
Date: Thu, 20 Sep 2007 20:34:54 -0700
Local: Thurs, Sep 20 2007 11:34 pm
Subject: Re: Anti-regen Rides
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A while ago I used two "WattsUp" back-to-back to measure current in
and out.  Charging peaked a tad over 19Amps.  From my 8.5Ah "A" pack,
I took out 11.9Ah, and put in 3.9Ah through regen (the difference .5
was lost to heat).  Obviously that ride would not be possible without
Regen.

But yes, 19.02A charging is a very high charge current for an 8.5Ah
pack. (more than 2C, it would charge the battery from flat in less
than 30 minutes) so this would affect the life of the battery compared
to the slow charge on the shelf.  Also, we would be charging an
already warm battery, which is not as good as charging a cold battery.

So:
If you want your battery pack to last longer, treat it as gently as
possible.  No turbo, no high-rate regen.  With turbo shut off, regen
also is much lower.
Discharging the pack at 19A is every bit as bad as charging it at 19A.

But, 3.9Ah on an 8.5Ah pack in regen is a huge gain in efficiency, it
makes rides possible that would otherwise be impossible.

LiPos can probably tolerate more regen, as they have better current
handling, and more Ah to play with.

Be aware that any charing issues discovered with Regen would apply
identically to fast-charging of LiPos.

On Sep 20, 8:11 pm, deerfencer1 <deerfenc...@aol.com> wrote:

> Interesting ride tonight as I did a fast hilly 14-mile sprint up and
> down Quaker Hill and back again. I only had 1/2 hour or so to ride, so
> tried something different, and came up with some interesting results.

> Basically I sprinted up the hills with full power demand, then did the
> downhills as fast as  possible by bypassing regen but pedaling hard in
> freewheel mode to give the battery a break. IOW, on the downhill (3.5
> mile) stretches I tried to keep the current draw minimal, somewhere
> around 100-300W, just enough to bypass regen, and pedaled hard in my
> top (54/11) gear to maximize my speed.

> Results: I averaged between 20-22 mph on the uphill portions with max
> pedaling and current draw, then very close to 33 mph on the downhill
> stretches with virtually no regen and minimal current, though with an
> occasional minor e-goose on the flats between downgrades. I averaged
> around 1.4 miles/Ah after 14 miles of this fast up and down riding.

> Here's the significant part: the lipo packs were almost stone cool at
> the end of the ride, even though I had been riding them to the max on
> the two 3.5 mile climbs. The last part of the ride was downhill but
> still I was very surprised at how cool the packs were to the touch at
> ride's end considering how I hammered them on the climbs.

> Conclusion: This whole Regen debate is a very worthy one as I'm
> starting to think regen may indeed be a major stress on our packs. IOW
> I'm ascribing the cool packs to the fact that I overrode regen for
> pretty much the whole ride--and kept my average speeds very high by
> just pedaling hard on the downhills and freewheeling. 33+21/2=27 mph
> average, which is very fast.

> I plan on investigating this further by bypassing regen as much as
> possible and am very interested to see what my average speeds and
> range come out to be riding this way over longer distances.

> Larry


 
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