Hi Zeke,
In looking at your battery spec, it indicates the 12 volt battery is
391 watts per cell constant discharge for 15 minutes to 1.67 volts per
cell. If I divide the 391 watts by 2 volts per cell, it comes out to
195.5 Amps for 15 minutes for the voltage to drop to 1.67 volts per cell.
You mention that you are drawing 300 battery Amps at times, which is 100
Amps more. looking at the chart indicates 505 Watts constant discharge
per cell for 10 minutes. at 2 volts per cell, that 's 252.5 Amps.
Does it seem reasonable that with high current draw(acceleration, going
up a hill, high speed) you don't have much time before your batteries
are discharged?
Don
On 8/29/2013 12:08 PM, Zeke Yewdall wrote:
Sorry... I posted the details a long time ago.
Photo of it on top of the mountain today:
http://sphotos-a-lax.xx.fbcdn.net/hphotos-ash3/1240063_605592482816967_962234180_n.jpg
For current reference:
It's a 1973 VW superbug with the e-volk #2 kit...
http://www.e-volks.com/about2.html?
It was an "interesting" conversion that was virtually undriveable when I
first got my hands on it. Some odd design choices too (for example, the
original starter motor was left attached to both the ignition key and the
transmission... so everytime you "started" it, the 12 volt starter motor
would rev up briefly -- I thought it was sending a surge to the main drive
motor when you started it, but then found that. Hmm......... could
probably lose 10lbs by taking that out.
Controller is the Alltrax 7245
Motor is 6.7" series DC by D&D direct coupled to transmission -- in this
case, I can shift through all the gears just fine without a clutch, except
1st I have to rev the motor a tiny bit to get it in there if it's moving
already and I'm downshifting from 2nd.
Batteries are 12 volt 100AH AGM UPS batteries
http://www.npstelecom.com/pdfs/Dyn_UPS/UPS_12-370.pdf
72 volt nominal system, 74lbs each (444lbs total) + auxiliary battery
(which is a standard starter battery instead of a deep cycle... ugh).
Those batteries look like pretty high rate batteries... no real idea on
how old they are though -- they are used taken out of UPS systems I think...
I've added a Xantrex AH meter and some circuit breakers and such, and an
Elcon 1200 watt charger. No DC-DC, separately charging the 12 volt
auxiliary battery.
It's incredibly fun to drive for a few miles now, till the current limit
kills the performance... but not quite long enough range to be actually
useful yet.... 7 or 8 miles is a long as I'm getting before current limit
is shutting it down to snail pace.
What do people think of the Concorde AGM batteries? Wondering if that
might be an option for new ones. A bank of PVX-1290T would have a 1 hour
rate of 79AH, for the same weight as the existing bank.
I'd like to do a bank of GNB 100AH lithium batteries, but that would
roughly double what the client paid for the car (they got a great deal
anyway, just the restored glider was worth what they paid, even if it
hadn't had any EV stuff put in yet). Though... that's only about twice as
much as a good AGM bank, so maybe it doesn't make sense to do lead. I want
to have good options to present to them though.
Z
On Thu, Aug 29, 2013 at 12:39 PM, EVDL Administrator <[email protected]>wrote:
On 29 Aug 2013 at 11:51, Zeke Yewdall wrote:
It seems like it's staying on till about 1.7vpc, and that's probably
not good for the batteries to drop below that, right?
The rule of thumb for lead is that you stop (or reduce load) when the
battery voltage under load falls to 1.75 volts per cell. You hope that
will
prevent cell reversal. It doesn't always.
As for where to go, I'd start with replacing the one battery that read low.
That's probably just a quick fix, though.
Some kinds of AGMs can deliver huge currents with aplomb and are suitable
for fast, short range EVs. Others are hardly much better than the infamous
flooded marine batteries that die in a few months of such use. But you
don't say what the batteries are (or if you did I've forgotten).
Could you remind us of such matters as vehicle weight, what batteries
you're
using, what motor, what controller?
This is a Beetle, right? I'm pretty sure I remember folks back in the late
1970s and 1980s building Beetles with 72v golf car battery packs. They
gave
up the back seat to batteries, of course. However, I checked the EV Album
(searched with startpage.com, as Evalbum search wouldn't work for me) and
found only this one, I guess originally converted by Lawrence Rhodes :
http://www.evalbum.com/1466
And another with 8v golf car batteries :
http://www.evalbum.com/1689
David Roden - Akron, Ohio, USA
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