Dumb battery charger

If you only have a smart charger, you can sometimes charge a flat battery by kinda fooling the charger. Just connect a good battery in parallel with the dead one, then connect the charger (to either battery of course - no difference). The smart charger will see the voltage from the good battery and start pumping out its precious electro-juice. After a while you can disconnect the good battery and keep going on the dead one.

Haggis.
 
aogrady said:
If there is a duff cell though there’s no coming back from that of course.
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Yeah you can… but it’s a bit brutal…
Sulphates build up on the lead plates over time, esp if the battery runs flat or gets overcharged. That reduces the capacity.
The “bush cure” is to charge it as best you can, then short it out with a large screwdriver. The high current blows some of the sulphate off and gives you a little more life.
Also does irreparable damage, but if you’re stuck, or you were going to throw it away anyway 👍

P.S. this is for worn-out lead-acid wet batts, not AGM, and definitely not Lithium!
If you try this trick with a good battery with high current, you’ll find out why you were warned not to do this 😬
 
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