Thanks, Bruce,
I have lived with batteries for thirty years so I do know some of the
basic things but for most of that time I used secondhand batteries.
The last couple of years using expensive new ones I find that they
often perform less well. I would like to tap into the enormous
experience of this forum to calibrate some of my assumptions.
I got a nice speedy and informative reply to my first post but when I
asked too many questions in the second one it produced a lot less
information. Maybe I need to go straight to Rolls tech support for
discharge curves at lower temperatures and lower currents.
I do have one more question for any wrench who programs 'genstart'
voltages on Outbacks and the like. At what battery volts do you
start the generator for a system with a large battery and small
loads, in the winter?
I would habitually use about 23.5 or 47 volts as a discharge limit
voltage (time delayed). However I am finding that from full charge
at a temperature around 5 degrees C, I am getting under 25% of the
battery capacity using this rule. I this what I have to accept? Is
the capacity that much reduced by temperature? Will I reduce the
life expectancy and invalidate the warranty if I discharge it to
23/46 volts instead?
I wonder why there is no temperature compensation on low battery
voltage settings like there is on charging set points. Do I just
have to use the generator much more?
There I go asking too many questions again. I do have a few more
that I will save for now. Thanks for any more comments.
best wishes
Hugh
Hi Hugh, When discussing battery characteristics with a chemist at
my supplier years ago I was told the capacity at 0 deg c is around
50% of that at 25 deg c because the ion transfer rate within the
cell is slowed by the low temperature. This "loss" of capacity is
recovered once the battery warms again. The same reason why a fully
charged cranking battery in a car can fail to turn the motor in cold
weather. Ion rate is so low it simply can't deliver enough current
to the starter motor.
So, the answer to the second part of your question is yes.
A good thread with lots of useful background into how batteries
really operate.
Bruce Geddes
PowerOn (at the other end of the world)
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
--
Hugh Piggott
Scoraig Wind Electric
Scotland
http://www.scoraigwind.co.uk
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
