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Battery damage if drained fully?

35K views 17 replies 10 participants last post by  E46330iguy  
#1 ·
I rarely drive my car so I've been caught a few times where the battery was totally drained and I needed a jump start.
I finally got a slow battery charger for when I know my car will not be driven for a few weeks to months and now use that.
The question is, could there be any damage to my battery because it's been let to drain fully a few times?
Reason I ask is cause yesterday I was working on some foglight stuff where I needed to leave the lights on for a min or two a few times. When I was done I go to get in my car and car wouldn't start...I pop on the charger for a few hours and bingo car starts (the charger said the battery wasn't 100% charged).
 
#4 ·
Good point, I mean drained low enough where I couldn't start the car but needed a jump...I recall the lights, radio and other stuff still operational....
Does this mean my I should change my battery, because now it seems good, I will test it out by leaving the lights on for like 2-3 mins, then see if I can start the car. If the battery fails again then means it's not fully charging 100% even with the slow charger?
 
#7 ·
depends on how old the battery is........ a car battery typically lasts on average between 3-4 years. Sometimes 5. That's on average. Some can last longer, some shorter. When you run a lead acid battery right down....you increase the changes of ruining the cells/plates inside the battery. A couple of times of doing a complete run down......the battery will lose atleast one plate, sometimes more than one. The older the battery the increased change you'll kill a battery by running it right down. Kill as in, it won't charge back up to full, or charge at all. If you trickle charge a battery you think isn't fully functioning, it's the best way to determine on your own if the battery is usefull anymore. You can take a battery to any automotive shop and they can test your battery for you and tell you whether it's holding a charge properly or if it's dying.

By the way......the BMW battery you get at the dealer is a rip off. Here the dealer wants $315 for a battery installed. $20 less if you install it yourself. If you buy a battery elsewhere, like a DIEHARD or EXCELL or other name brand battery....... they will be 50-60% cheaper in cost. AND EXACTLY THE SAME in charge and capacity, if not better. There is NO difference in a brand name battery or an OEM battery, as long as you get the right size/fitment and specs for your car. I'm sure your probably aware of it......thought I'd just mention it.
 
#8 · (Edited)
Yes, running down the battery and leaving it discharged for a while causes harm. Sometimes the battery will just deeply discharge to the point where it will take a really long time to charge back up again. If you do this too often though, then yeah, you will mess up the insides of the battery. Automotive lead acid batteries are usually intended to not be fully drained but used to run the radio when the car is off and start the car, then to be constantly charging while the car is running.

I personally destroyed a battery or two just from doing things like opening the doors and letting the interior lights drain the battery while the car was sitting for a few weeks without being started. Now i make it a point to keep a quality charger on the battery and haven't had a problem. I used one made by CTEK.
 
#10 ·
I've had my car sitting in the garage for about 7 weeks, and I went out this afternoon to start it up and found the battery is dead as a doornail. I just put a 2 amp trickle charger on it, but the charger needle isn't moving, so I don't know if the battery is accepting any current whatsoever. If I leave the trickle charger on, do you think the battery might start to come around?
 
#13 · (Edited)
OP, to answer your question... yes.
When you really drain a lead acid battery it's very important to charge it immediately with a
higher amp output charger. I would use at least a 10 amp, & up to a 15 amp charger,
preferably a charger that ultrasonically conditions a weaker or failing battery. A small trickle
charger is not what you want to use, to try to recharge a 80, 90 or 100 plus amp battery.
When your dealing with a battery thats in "good condition" then you can use a 1 or 2 amp
trickle charger, to maintain it.

I pulled this from another post that i submitted it in, it might be helpful here.

"Battery Tenders (it's a small 12v trickle charger) are great, don't get
me wrong, i own 2 different kinds. But for this problem i wouldn't use
one. The most common Battery Tender is the 1.25 amp unit, most people
don't know this but there out put is only 1.0 amps. A 1 amp charging
device has trouble pushing the acid back out of the lead plates of your dead
battery. Very few people in the country know this but the Tender has
a 72 hour timer, and the last 8 hours of the 72 are at less than 1 amp,
about .5 amps. So your maximum amperage that you can put back into
your battery is 68 amps, but that's under ideal conditions. Not knowing
what battery is in your Bimmer, I'd guess it's larger than 68, probably 90
plus amps. I would use a regular size charger and charge at about 10 or
12 amps. I also own this charger, you can pick it up at your local Walmart,
it will do a great job. I promise."

http://www.walmart.com/catalog/product.do?product_id=13005745&findingMethod=rr
Good luck,
 
#15 ·
Get yourself one of these http://www.optimabatteries.com/optima_products/redtop/index.phpYou can Drain it as low as you want and it will always hold a charge but they can be up to 300 bucks at some stores. The last one i had lasted me 15 years!
1. No, running even that battery to dead could kill it, or at the least cause permanent damage. Leaving just about any rechargeable battery in a dead or near dead state, will cause damage the longer you leave it like that. Rechargeable batteries also have a limited amount "power cycles" before their performance starts noticeably degrading. If you have a car with a properly performing alternator, and a quality battery of enough capacity, the battery should last 10+ years.

2. You should put a space between your link and the "You" of your next sentence, as it breaks the link.