Fully charged battery voltage

[Ramp Builder]

I've been using Ridgid 18 volt tools for a couple of years building wheelchair ramps. I've just had the original batteries replaced (for the second time) and also just bought 2 3.0 AH lithium ion batteries.

I'm just trying to find out what the specified battery voltage is for fully charged batteries...the 18 volt NiCad MaxHC and the 18 volt Lithium Ion 3.0 AH.

Any help would be appreciated.

Bill

[Velosapien]

Usually 18v batteries are actually about 20v at peak right after charging.

[Ramp Builder]

Thanks for the quick reply. My lithium ion batteries show 25 and 26 volts. The one nicad battery I have in the house shows 26 volts.

I wasn't sure if the lithium ion batteries charged correctly...guess they did.

[Calder]

Are they 18 or 24 volt batteries? I have ten 18 volt NiCd batteries, (3 different makes) and they all come off charge right around 21.0 volts (plus or minus 0.2 volts). After 12 hours they get down to about 20.5 volts, and at 7 days are down to 20.0 volts.

I don't think Li batteries should be much different in their off-charge voltage, their nominal rating is 3.6 volts per cell with a max of 4.2 volts (I think). With 5 cells that gives a nominal voltage of 18 volts and a max of 21 volts.

[DRC-Wartex]

Are they 18 or 24 volt batteries? I have ten 18 volt NiCd batteries, (3 different makes) and they all come off charge right around 21.0 volts (plus or minus 0.2 volts). After 12 hours they get down to about 20.5 volts, and at 7 days are down to 20.0 volts.

I don't think Li batteries should be much different in their off-charge voltage, their nominal rating is 3.6 volts per cell with a max of 4.2 volts (I think). With 5 cells that gives a nominal voltage of 18 volts and a max of 21 volts.


Accurate graphs here http://www.molienergy.bc.ca/pdf/IMR18650E.pdf

[Ramp Builder]

Calder

The batteries (both the lithium and the NiCad) are 18 volts.

[Calder]

Looks like they all charged OK, since all are the same voltage. The voltage is high. I don't believe either chemistry can be charged that high. You might want to check your voltmeter. Per the charts from DRC, the max voltage of the Li cells are 4.2 volts, therefore max voltage in a 5-cell battery is 21.0 volts. For NiCd cells, I believe the max voltage you can charge them to is 1.45 volts per cell, therefore max voltage in a 15-cell battery is 21.75 volts. Clearly the numbers you have are much higher than these, which makes me think your voltmeter is reading incorrectly.