Load testing a Battery

Boomyal

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Any ideas for load testing a battery out of the car? My son's battery just died. We left it on the charger overnite, @ 1.5 amp, and now would like to check it to make sure it is a bad battery as opposed to a drain from the car.<br /><br />It seems you should put X load on the Batt for Y amount of time and end up with Z voltage to confirm if the batt is good.
 

Bob_VT

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Re: Load testing a Battery

Got a parts store open near you? How about a walmart? Those testers are pretty heavy duty with the load they apply I would not begin to rig up something.
 

Boomyal

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Re: Load testing a Battery

Thanks Bob, I did not want to use a retailer that I was not going to buy a battery from. I want to get one, if necessary, at Costco. They used to load test 'em but apparently do not anymore. <br /><br />I just found this one at Harbor Freight and am headed there now. It's on sale for $17.99. Be a handy thing to have around.<br /><br /> http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90636
 

Bob_VT

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Re: Load testing a Battery

Yup that will work and they get hot! That is why I shyed away from the homebrewed.
 

ZmOz

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Re: Load testing a Battery

I've heard the HF load testers only really work at around 50 amps, which wouldn't be a big enough load to tell you anything. Even 100 amps is still pretty low...
 

ndemge

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Re: Load testing a Battery

...keep in mind, if your battery was dead, and you only gave it 1.5amps for 12 hours..... your still not even to half charge.<br /><br />I would not feel bad about going to an autozone and having a battery tested, Do you spend $ at these stores for OTHER services they provide? If it were found that your alternator were bad and drawing down your battery, where would you buy it?
 

Boomyal

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Re: Load testing a Battery

Originally posted by NoelMG:<br /> ...keep in mind, if your battery was dead, and you only gave it 1.5amps for 12 hours..... your still not even to half charge.
Thanks for that tip Noel, I'll give'r another twelve hours. Thought that a slow charge was better for a drained battery.<br /><br />Bob, so true on the heat. I went down and got one. You only apply the load for 5 seconds to get the reading on the batt. My son and I did it in the car (batt in box on back floor), on the way back from HF. You could smell the 'cooking'. <br /><br />I believe the HF unit (claims tests up to 1000 cca batts) uses an extrapolated result to pass judgement on the condition of the batt. It did show that the batt was weak. <br /><br />We will clean it up and put it back in for a couple of days and see what develops. Young son does carry a good set of jumpers.
 

ndemge

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Re: Load testing a Battery

yes,slow charge is best.... but something like a 10 amp on an automatic charger is good. Hitting that dead battery with 50 amps for 2 hours is not good. 1.5 amps.... gonna take ya a couple days.
 

Scaaty

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Re: Load testing a Battery

The Harbor Freight Load tester works fine, on ANY battery. And its 100 amps, 50 to 1000cca. Don't know of a lot of car batts putting out for than that. Hook up, click on for 5-10 seconds, and if the needles drops below (on a fully charged Batt)12 volts, its toast<br />And a 1.5 amp is WAY too low for a car battery,, no less than 6amps, best at 10. Read a battery chart to see just how long 1.5 would take to charge a dead car battery..lifes too short!
 

heycods

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Re: Load testing a Battery

I bought the digital one from harbor freight and it works fine Ive been using it for 2 years. I have used it on battrys up to size 4d (catapillar) The digital only cost me about $3 more.
 

whywhyzed

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Re: Load testing a Battery

Originally posted by NoelMG:<br /> Hitting that dead battery with 50 amps for 2 hours is not good.
:) <br /><br />Which is exactly what everyone's alternator does after they get a boost... then they wonder why their batteries don't live after they keep leaving their lights on...
 

Boomyal

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Re: Load testing a Battery

This morning, after having 'under' charged the battery the nite b4, the ol' Crown Vic was deader than a door nail. It held sufficient charge during the day to be able to start and run it last nite. But it couldn't hold enough charge overnite to do the job.<br /><br />Seems that the HF tester predicted it correctly. Bought a new batt today and now have a tool at hand next time there is an issue. (We have lots of candidates. The front of this house looks like a used car lot.)<br /><br />My 18 y/o son inherited his Grandpa's '88 Crown Vic with 77k miles on it. Ryan T, eat your heart out. :p <br /><br />
DSCF0862.jpg
 

Mark42

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Re: Load testing a Battery

I have found that laying a lug wrench across the terminals will indicate load rating. If the top of the battery blows off in less than 10 seconds, it was up to snuff. :D <br /><br />BTW, nice old Crown Vic. Where did you get it?
 

18rabbit

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Re: Load testing a Battery

Originally posted by hystat:<br />
Originally posted by NoelMG:<br /> Hitting that dead battery with 50 amps for 2 hours is not good.
:) <br /><br />Which is exactly what everyone's alternator does after they get a boost... then they wonder why their batteries don't live after they keep leaving their lights on...
You might want to rethink this one. Car batts/starting batts are designed to spit out, and thus suck up, big amps in a short amount if time. The faster you can recharge your batt, the happier you batt is, the longer its useful life.
 

ZmOz

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Re: Load testing a Battery

Originally posted by 18R:<br />Car batts/starting batts are designed to spit out, and thus suck up, big amps in a short amount if time. The faster you can recharge your batt, the happier you batt is, the longer its useful life.
Wrong. Car batteries are designed to to put "spit out" and "suck up" large amounts of amps for very short periods of time. Any type of battery, whether it's starting or deep cycle, lead acid, nimh, nicd, or lithium ion, will benefit from the slowest possible charge. Every time you use your battery sulfation develops on the plates. The slower the charge is, the more sulfation is dissolved during recharge. The build up of sulfation is what eventually kills almost every battery.
 

Boomyal

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Re: Load testing a Battery

Originally posted by Mark42:<br />BTW, nice old Crown Vic. Where did you get it?
It resided in the garage next door to me for the last 17 years.
 

18rabbit

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Re: Load testing a Battery

Originally posted by ZmOz:<br /> The slower the charge is, the more sulfation is dissolved during recharge.
Urban myth. Like I said, you may want to rethink this.<br /><br />In general, the deal charge rate for a lead acid batt will be between 20% and 40% of C.
 

Limited-Time

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Re: Load testing a Battery

Originally posted by Mark42:<br /> I have found that laying a lug wrench across the terminals will indicate load rating. If the top of the battery blows off in less than 10 seconds, it was up to snuff. :D <br /><br />BTW, nice old Crown Vic. Where did you get it?
Problem with that test is it's hard on wrenches :eek: :D :D :D <br /><br />Oh, and BTW, nice Vic!!
 

ZmOz

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Re: Load testing a Battery

Originally posted by 18R:<br />Urban myth.
It most certainly is not. Any battery manufacturer will agree with me 100%. The best charge is always the slowest possible charge.
 
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