[urq] Battery issue

Brett Dikeman quattro at frank.mercea.net
Fri Dec 7 22:10:51 PST 2007

On Dec 7, 2007, at 10:17 AM, Max Hoepli wrote:

> I left the car standing for 3 weeks, went to start in -8C and  
> cranked over
> slowly, never started, the radio alarm went off. Does it matter how  
> long I
> leave the battery in this condition before getting battery hook-up?  
> The 4
> year old battery is under back seat.

Bunch of comments:

*FYI, in my experience (and that of a couple of other listers) Optima  
batteries aren't worth anything.  They fail often, the dealers refuse  
to honor the manufacturer's warranty (illegal in MA, actually-  
possibly in other states) and Optima's warranty return policy requires  
dealer testing, followed by shipment to them (on your $$$), them  
testing it, and then MAYBE you getting a new one shipped to you.

*Car batteries self-discharge just sitting on a shelf; add in a clock,  
seat position memory power, ECU adaptation memory power,etc and you  
can easily drain a battery in a few weeks or less. Aftermarket radios  
may consume a lot more power than the factory systems.  The best place  
to store a battery long-term is in a cool place; contrary to what some  
posters said, cold weather actually slows the self-discharge; hotter  
temperatures accelerate it.  Any storage longer than 2 weeks should be  
done with one cable disconnected, and preferably a maintenance charger  
or solar panel connected (and don't bother with the small 5w panels  
unless you live somewhere with plenty of sun, where the panel won't be  
shaded, etc.)

*Colder weather slows the chemical reaction that produces power, so  
cranking ability is hampered quite a bit.  Side note- if you have a  
won't-quite-start situation, turn on EVERY accessory in the car for a  
minute or two, turn everything off and wait a minute or so, then try  
again.  The heat generated from (almost) shorting the battery can  
sometimes warm things up enough that you'll get more power out of it.

*Any time a lead-acid battery is not fully charged (or close to it),  
sulfur in the battery acid starts to coats the lead plates in a  
process known as sulfation.  There are DIY circuits and devices  
available that can reverse the process somewhat, via extremely short  
but high current pulses of electricity. Some battery charges have this  
functionality built-in.

*If a battery has been slowly drained, you should charge it at the  
slowest rate possible until you're sure how sulfated the battery is.   
Sulfation reduces the capacity of the battery, and thus its maximum  
charge rate.  They usually "die" completely when they get drained,  
someone slaps a charger on, and overcharges it, causing violent  
gassing...which causes the plate grid to break apart.

*Draining a 12v lead-acid battery below 10.7 volts, no matter the  
type, will damage it.  Deep-discharge storage batteries will tolerate  
that kind of abuse better than others, but it still causes damage.

*Be extremely careful with dead batteries in such a cold temperature;  
as the battery SOC (state of charge) drops, the freezing point of the  
electrolyte RISES, quite a bit.  A dead battery WILL freeze easily,  
and if you attempt to charge a frozen battery, you will likely cause  
it to BURST VIOLENTLY, spraying battery acid everywhere.  Bring such a  
battery indoors and give it plenty of time to warm up.  Bringing it  
close to room temperature is best, so you don't overcharge it (the  
charger expects the battery to be at about room temperature; State Of  
Charge vs. voltage is dependent on temperature, and the colder the  
battery is, the lower the 100% SOC voltage is.

*SLA/AGM batteries are not necessarily better for automotive  
applications.  Among other things, they're very easily damaged by  
overcharging, and have different voltage ranges.  I've had horrible  
luck with Optima batteries, as have a number of other listers- and  
their warranty policies suck.

*After storing a battery for a while, even on a maintenance charger,  
you should twist/rock the battery a bit to stir the electrolyte;  
sometimes the electrolyte can settle at the bottom of the battery.   
Alternatively, you can put it on a full charge or equalization charge;  
the bubbling will stir up the electrolyte. Some maintenance chargers  
incorporate an automatic periodic full charge cycle; my Yuasa (which  
is based off the same basic charger circuit board many of the 1.5-2A  
maintenance chargers are) does this every 30 days.

FYI, the best resource pretty much hands-down for how to care for lead- 
acid batteries is www.batteryfaq.org.


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