battery charging

[RDW]

I have a disagreement with a fellow boater but I do not know enough to be sure he is wrong. I was using a battery driven drill. It did not have enough juice to finish the last hole. I suggested putting it on the charge for 15 minutes and trying again. His comment that it needed to be fully charged before I could do any good.
In our discussion, I made the comparison to an electric car. I gave the opinion that if a car would go 250 miles on a full charge that would take 24 hours to fully charge, it would go further in total if you did 4 six hour charges and driving between each charge. My theory is that charging is faster while charging a discharged battery than getting the last 50% of the energy into the battery.
Anybody got any opinion other than we are crazy and beers may have been involved in the discussion?
RDW

[RDW]

`must be a boring topic or a dumb question
rdw

[skipmac]

For standard lead/acid batteries, then yes a very discharged battery will take more charge faster than a slightly discharge battery. So to charge a battery from 50% to 60% will take much less time than charging from 90% to 100% even though both are adding 10% charge to the battery.

This of course assumes you have a charger that will put out as much as the battery can accept.

If I understand the chemistry correctly, this would not be the case with LiFePo batteries that I think charge at the same rate all the way to 100%.

So the answer would depend on the battery chemistry.

[newhaul]

To answer you I would need to know if the charger is a standard or a rapid charge but if just needing to drill one little hole 15 min on charge would help you

[btrayfors]

The answer is YES, you can do that UNLESS the batteries are NiCADs. These have a "memory" and should be fully charged before using again.

However, these days most utility batteries are not NiCADs, they're LiIon which has no "memory".

So, you can charge for a few minutes, finish the job, then put the battery back on charge.

Bill