On 07/27/2015 06:08 PM, Lee Hart via EV wrote:
Willie2 via EV wrote:
Thanks! Bottom line, take away: 50-90 ah on a fresh lead pack.
It's not quite that bad. The Peukert effect does not change the ACTUAL
capacity; it only describes the APPARENT capacity due to high
currents. If you have a 200ah battery and discharge it at 100 amps so
it appears "dead" after removing 100ah, it is in fact at the 50%
discharged point. That's a "safe" discharge level -- you can do that
every day for 600+ cycles.
The other 100ah is still there -- you just can't use it with a 100 amp
draw. If you draw a lower current, then it will be there. :-)
Somewhat against my will, I just did some lead battery shopping. T105s
are about $150. The "minutes at 75 amps" rating seems most
appropriate. That would be just under 100 ah. From what you say, it
appears those are usable amphours. SAMs batteries, with presumably less
capacity and longevity, are about $90. So, a pack of six T105s would be
about $900. Negatives: corrosion, watering, lower performance as SOC
decreases, perhaps 1/3 the life of lithium, "all or nothing" major
replacement.
Compare to 12 TS-LPF100s: about $1500 plus about $300 worth of BMS
stuff. Negative: nightmare of wiring maintenance, "all or nothing"
major replacement.
Compare to 5 20ah ebike batteries @ $285. Total: $1425. Experience so
far indicates as few as 2 20ah ebike batteries can be used at a cost of
$570.
The longevity of ebike batteries is a BIG unknown here.
I believe it is likely that the above can be scaled to larger vehicles.
If the golf cart projects are successful, I will be exploring higher
voltages and capacities on larger vehicles.
The same 50% capacity limit applies to lithiums, too. If you discharge
them to 80-100% on every cycle, you won't get as long a life. (How
long the life will be depends drastically on the type and quality of
the cells).
I will not accept the contention that lithium batteries should be
limited to 50%.
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