Re: (ET) Solar charging, part 2

["Travis Creswell" <ozsolar ipa net>]

I charge my E-15 with solar.  Yes, you will need a charge controller.  On 
my
old pack, which was a very abused set of batteries before I got them the
solar wouldn't overcharge them, even in a week.  Now, I have a new pack of
T-105's and I had to get charge controller.  I found my battery pack
regularly at 16 volts per battery if I didn't pay attention and shut the
array off.  I mow approximately less then .75 acres and the new pack 
charges
up in just a few days with 340 watts of solar.  I'm using a maximum power
point tracker to charge it.  I use four 85 watt solar panels wired in 
series
(48 volts nominal) and the charge controller converts it to the 36 volts 
the
tractor needs.  I've set the charge limit to 45.6 (temp compensated).  If
you are interested in this charge controller I use you can check them out 
at
www.outbackpower.com.

Travis

Joplin, MO
E-15


----------
>From: Jim Coate <jbc coate org>
>To: ELECTRAK <elec-trak cosmos phy tufts edu>
>Subject: Re: (ET) Solar charging, part 2
>Date: Tue, Apr 22, 2003, 8:32 AM
>

>Christopher Zach wrote:
>> In the meantime, some thoughts: I am beginning to think that you could
>> simply take 3 60 watt panels, connect them in series, plug them into a
>> breaker box/disconnect with a 10 amp fuse (DC RATED!) and run a cable 
>> into
>> the Elec-Trak. Put a single diode in there to prevent back-feeding the
>> panels from the tractor and let it rip.
>
>This would basically work, but...
>
>> I doubt that the three panels could produce enough current (5 amp hours
>> *tops*) to overcharge the batteries. 
>
>Note that current is measured in *amps*. So these panels would be 
>producing 5 amps. IF left connected for 1 hour, would then have 5x1 = 5 
>amp-hours (or if left for 20 hours would have 5x20 = 100 amp-hours).
>
>> But that would be enough to put 100
>> amps into the batteries over the course of a week; enough to top them 
>> off.
>
>This would be 100 *amp-hours*. So, as above, 20 hours of full sun, or 
>just under 3 hours per day. During the summer months you'd probably get 
>much more than that. During the winter, possibly less.
>
>> Any thoughts? Can a T105 last with a float charge of < 5 amps?
>
>A "float charge" normally refers to a fixed voltage source. Once 
>charged, 5 amps is enough to get a T105 gassing nicely. If you use the 
>tractor once a week, it would take a few days to fill up so wouldn't be 
>until near the end of the week that during mid-day sun it would get to 
>the gassing point, so could end up with just a nice amount of 
>equalization. However... if you don't use the ET for a while (no rain in 
>August so no new growth to mow) then might get a bit over charged. The 
>flip side is that if really run the batteries pretty far down (and then 
>it rains for a couple of days), then could take many days to charge back 
>up, which could promote sulfation.
>
>So, not the ideal charger but... probably just as good as the OEM 
>charger which tortures the batteries in different ways yet people get 5+ 
>years out of a pack. And it's solar.
>
>
>_________
>Jim Coate
>1992 Chevy S10
>1970's Elec-Trak
>http://www.eeevee.com
>
>