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Garret,
Had a chat with John Bidwell about the local Colorado EV motorcycles to
compare notes about the range of my Kawasaki EX500 ninja EV. A few summary
points for the group and direct answer to your question.
First I have now actually weighed most of the components of my bike during
a battery replacement process. The full bike weighs ~540#s or roughly 100 pounds
more than the "wet" weight of the base vehicle in ICE trim. The chassis with
controller (no batteries or charger) is 265#s roughly balanced front and
rear.
Remember I am running 72 volts of older YT AGMs. They are labeled at 65AH,
but I suspect they are the same as the newer models labeled at 55AHs. The bike
came with a set of original batteries that were suspect. My real world range
(very hilly) with these batteries on a warm to hot day was ~20 miles
without conservative driving. Range when temperatures were well below 50
degrees was ~10 miles.
This winter I removed the batteries and began to weed out the weaker ones.
Here is what I found. First the highest voltage battery was the lightest when I
weighed it. It was down 1 pound when compared to the weight a new battery.
This was the result of fluid boil off e.g. venting. I also found that when load
testing the lowest voltage battery in the pack that it dropped off
more quickly than its peers. I also found one of the remaining batteries
with apparently good voltage levels also fell off more than the others. So in
the end the pack had 2 weak, and one bad battery.
I spoke with an EV battery pack technical specialist at Johnson Controls
(they make the YTs) in Wisconsin. He indicated that the K&W charger that
I was using for all my charging needs is pretty abusive for these batteries
over time. He recommended that I try using the Soniel chargers. Also charging
the pack in series with the K&W doesn't quite fill up the batteries as
it does not provide the 2 amp constant current for 1 hour finishing charge
that the manufacturer calls for. As with most semi smart chargers it simply
tapers off the current at the end of the charge cycle. So the
batteries are not getting fully toped off.
Another conclusion that I have to share is that even though a battery shows
only 3 or 4 tenths difference in terms of voltage when compared to its peers in
the pack that this indicates an out of balance condition. Although less than I
deal I don't know what real affect this has on range.
In an ideal world if I had a pack that was not providing the range expected
I would install instrumentation that allowed me to look at the voltage of each
battery in real time as the pack gets discharged. I would have been able to
identify the weaker batteries in my pack if I had been able to get this
view. In my mind a view of the total pack is less valuable than being able to
view the performance of each battery.
Please note that I spent some time breaking the new batteries in on
the bench. They each have at least 4 gentle charge discharge cycles on them
(the specs call for 6 to complete break in).
At this point I am rewiring up the new pack (some of the original
cabling was not up to my standards) and moving to parallel charging. I'll report
back to the list when I have some new pack range numbers to
share.
Mike Bachand
Highlands Ranch,
Colorado |
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