What is the acceptable voltage drop for a 12V Battery?

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Old 05-23-18, 12:33 PM
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Question What is the acceptable voltage drop for a 12V Battery?

I have one those car battery jumper packs (basically a SLA battery in a box with some extra goodies).

I suspect the battery is bad as I tried to jump a friends car and it failed to start (The cars battery was not totally drained just not enough to start the 2011 Honda CRV 4 Cylinder engine).

I then fully charged it for 24 hours as mentioned in the manual. I waited about 14 hours for the voltage to stabilize.

Without a load I get 12.69V. I then attached a 12V 55W halogen car headlamp and the voltage then dropped to 11.99V (That is with only a 4.58A load so I imagine with a starter motor which is hundreds of amps that the voltage will be practically nothing).

I did attach the head light and meter to the clamps which in turn are connected directly to the battery in side the unit .

So is it safe to assume my jumper needs a new battery? The unit requires a 12V 18AH Sealed Lead Acid battery

It is a Peak Automotive PKC0AZ

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Old 05-23-18, 01:07 PM
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Sounds like a bad battery to me. That charger has poor reviews. You may want to cut your losses and part with it.
 
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Old 05-23-18, 01:54 PM
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The battery clamps and the switch seems to be of good quality.


I am going to buy a new battery and an analog voltage meter and use my car battery charger to charge the new battery (Don't worry it is also listed to charge AGM/SLA batteries along with the standard flooded/wet cells).

I am keeping the 12V power point but the USB charger and the LED worklight can go away

The unit is about 6 years old and it had a hard life (Starting a Jeep Grand Cherokee V8 almost every day for about 2 of the 6 years I had it) The Jeep was a total POS and had a battery drain a brand new high quality battery was dead (as in totally dead no lights no click when the key was turned NADA!) with in a week of no use. Needless to say that car is gone, so the jumper was sitting for 4 years but I did charge it occasionally
 
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Old 05-23-18, 06:26 PM
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Six years isn't bad for a SLA battery. I replace any of mine after 5 years. Mossman is right; put that one out to pasture.
 
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Old 05-23-18, 06:35 PM
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The mew battery will run around $35 so it should be a worthwhile replacement.
 
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