[ausev] Cold weather and lead acid batteries

[Chris Robison]

As I understand it, the charge management system on board the Ranger is 
extremely simplistic, to reduce manufacturing and design costs.

Essentially, the system just monitors the voltage of each of its 
batteries during charge, waiting for the first battery to reach a 
voltage representing a full charge. At that point, the current backs off 
to a trickle, a small enough current that the batteries can 
theoretically withstand the overcharge for long enough that the other 
batteries can catch up.

With a substantially imbalanced pack, this can mean an extremely long 
equalization period, potentially spanning several weeks of daily driving 
and overnight charging. If the vehicle is used regularly though, it 
shouldn't be a problem.

At any rate, I don't think the Ranger's charge management system is 
involved in any sort of weird charging or usage instructions.  I think 
the advice from Blue Sky is simply mistaken. "Memory affect" applied to 
early nickel-cadmium consumer dry cells; it does not apply to any 
battery chemistry used in EVs.

The best advice for lead acid batteries is that the more fully charged 
they are, the longer they'll last. Charge whenever you have a convenient 
opportunity.

   --chris




Erik wrote:
> Lead acid batteries don't have a memory, but all of the onboard charging and
> monitoring built into the truck sure might.
> 
> Erik
> 
> On Mon, Nov 24, 2008 at 3:37 PM, Mark Farver <mfarver at mindbent.org> wrote:
> 
>> 2008/11/22 Claire Sorenson <csorenson1 at austin.rr.com>:
>>> I called Blue Sky motors last week. They said that I should run the truck
>> to
>>> near complete discharge every two weeks.  They said if I do a lot of
>> small
>>> partial charges that it will cause it to charge less and less.  I have
>> been
>>> aware of batteries in phones and other small electrical items having to
>> be
>>> fully discharged so it doesn't create a "charge memory", but I didn't
>> think
>>> that this applied to lead acid batteries.
>> Lead Acid batteries do not suffer from a memory effect (the effect is
>> actually pretty rare in NiCad too).  Full discharge cycles are bad for
>> Lead batteries, the deeper you discharge them the shorter their
>> lifespan will be.  Don't take their advice.=
>>
>> Mark
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> 
> 
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