Convert mAh to Watt Hours
The formula is (mAh)*(V)/1000 = (Wh).
Example: 2200 (mAh) * 3.7 (V) = 8140 / 1000 = 8.14Wh
Convert Watt Hours to mAh
The formula is (Wh)*1000/(V) = (mAh).
Example: 7.92 (Wh) * 1000 = 7920 / 3.6 (V) = 2200
Series and Parallel Battery Configurations
- Voltage combines.
- The Positive side of the battery is
- Voltage stays the same.
Series & Parallel Examples
- Garage Tech with Randy Rundle: Series VS Parallel Battery Connections…Which Is Which
- Differences between battery circuits installed in series or in parallel | Garmin Customer Support
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S indicates the amount of cells connected in series and P indicates the amount of cells connected in parallel.
In this case, if we are talking 18650 batteries, 3 are connected together and the voltage stays at 4.2, while the capacity increases. S indicates that we have 6 of 3 parallel connections so we combine the voltage 3.6 6 times, giving us 22.2 volts.
We would like to create a 12v 18650 battery back. We have 84 spare cells. First we’ll need to find out how many cells required to reach 12 volts. You could do 12/4.2 to get 2.857… we obviously can’t split cells so we round up to the nearest number so that would give us 3 cells. 4.2*3=12.6 which is fine.
So now we know we need 3 in Series that’s S3, now to increase the capacities. We’ve got 84 cells and we need to divide them equally. We should also keep the series consistent so we can’t have 1 with an extra battery.
84/3=28, so now we’ve concluded our pack is 3S28P. That’s 28 cells in 3 groups, connected together to then give us 1 positive and 1 negative connections.
How to know what kind of capacity we’ll have?
Each cell, for instance has a capacity mAh of 2000.
Links & References
18650 Battery Pack Calculator and Planner – Cell Saviors
Battery pack calculator : Capacity, C-rating, ampere, charge and discharge run-time calculator of a battery or pack of batteries (energy storage)