I will take one step at a time. This will be my initation into the
electrical propulsion world. I believe in safety first and consider
myself to be conservative in my endeavors. My test run on Sunday will
not exceed an hour and I will be taking Arby's advice on running a
straight line course and then 180 degrees back along the same path. From
what I have learned from this discussion group is to not run at full
power for very long, but ideally to run at 30 to 40 AH which is
considered cruising speed. A second battery bank is feasible, even on a
E27, and has definitely been on my mind.
Thanks for the update though on the Peukert effect.
Don Swanson
On Wed, 07 Oct 2009 05:23:52 -0000 "aweekdaysailor"
<aweekdaysailor@
Don
I would caution against running too long on just these 4 batteries
(unless they are quite larger than I expect). I made that mistake, so
maybe you can learn from my experience. And apologies in advance if this
is already known to you or you've got monster 4D's in or something.
First - you should take the Peukert effect into account. If your
batteries are typical 100AH (for example), and you normally cruise at
30AH you might think you have 2.5 hours of capacity at 80% depth of
discharge ((100*.8)/30)
1.25) your batteries will only give you 1.7 hours - only 70% of what
might have been predicted.
Second - you should never run your batteries much past 50% so you really
will only get ~1 hour. Because I didn't understand Peukert I once ran my
original pack down probably well below 80%, damaging it.
Third - once your current batteries are used for a while and you then try
to double up - you'll find your battery pack to be pretty unstable where
it's difficult to get the old batteries charged correctly and balanced.
Your pack will then act as if every battery has only the energy capacity
of the weakest.
So I would make the investment in extra batteries now (I know space is
limited in an e27). If you do you'll get 2.5 hours @50% DOD. So on a
dollars/range basis - that second bank is much cheaper than the first and
well worth it.
regards and welcome to the e-boat club!
-Keith
--- In electricboats@
>
> I have just installed four batteries powering an ElectricYacht 48 volt
> system on an Ericson 27.
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