On 07/25/2015 03:25 PM, Lee Hart wrote:
From: Willie2 via EV <[email protected]>
Continuing to cogitate on ebike batteries: can anyone give me a good
estimate of the number of ah one can pull from a lead golf cart
battery? I'm thinking my 2 20ah ebike batteries are a pretty good
fraction of a lead pack. Can you keep a lead GC battery alive if you
pull 100ah from it?
6v golf cart batteries are generally 220-240 amphours at the 20-hour rate
(about 5 amps), and 100-180 amphours at the 100-amp rate. (The change in
amphour capacity depending on current is the Peukert effect that people talk
about.)
Golf cart batteries are designed for continuous loads of 75 amps, and will
happily supply 200-500 amps peak for up to a minute. But life will suffer if
you draw high currents for more than a minute or so.
For best life, you also want to limit depth of discharge to about 50% or so.
This is true for most types of batteries; not just lead-acids. The deeper the
discharge, the worse the life.
Thanks! Bottom line, take away: 50-90 ah on a fresh lead pack. That
pretty well matches my gut feel that my 40ah of ebike batteries is
around half of a good lead pack. I believe, in general, 80% or more of
a lithium pack can be used.
I'm working on my second golf cart ebike conversion. Just took out the
12 100ah ThunderSkys. When they were functional, I judged they had more
capacity than the best lead I have used. They weigh about 100 pounds.
The 20 ah ebike batteries are supposed to weigh right at 10 pounds
each. The ebike batteries appear to have greater energy density than
the TS-LFPs though I don't think they can have twice the density of LFP.
I recall that using lead, you got very little time with good performance
since the voltage declines ~linearly. With lithium, you can't guess the
SOC from performance; the carts are sprightly most of the time.
I'm eager to get a meter working so I can measure capacity.
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