Formula for AMPS,MAH etc..

[DISAR]

Reddy Watts has given the formula:

(Bat. Mah * 0.06) / run time = Amps

For a two battery setup in series, let's say 2 x 2s (4900 mah each) what mah we use 4900 or 9800?

And if in parallel?

[Steven Vaccaro]

In series the voltage is doubled and the mah stays the same. So 4900 in your case. There also some good formulas here.
http://www.offshoreelectrics.com/conversion.htm

[DISAR]

Thank you! I was also looking for this page.

[ReddyWatts]

MAH means you can discharge one milliamp for one hour from the cell/cells in series, before it is discharged to its minimum usable voltage. So a 3300 mAh battery can be discharged at the rate of 3.3 amps for one hour. Time decreases as amps increase.

In series it is the same amps for each cell or pack. 2 packs in parallel it is 1/2 of the amps are produced out of each pack. 3 packs in parallel it is 1/3 of the amps are produced out of each pack etc.

Parallel packs amps
step 1 - (Bat. Mah * 0.06) / run time = average Amps used

step 2 - average Amps used / number of packs = amps from each pack.

2 series packs using 4900 MAH = 4900 Mah total

2 parallel packs using 4900 MAH = 9800 Mah total

3 series packs using 4900 MAH = 4900 Mah total

3 parallel packs using 4900 MAH = 14700 Mah total

[ED66677]

Steven, can you have the tools/conversion page to pop-up when entering the forum? I also think a link to the ReddyWatts's "Ideas on building a Reliable BL system" and "Number cells/Motor KV/Prop Size/Hull Size" threads should be part of this pop-up!
... that would immediately direct newbie to the holly bible !

just an idea!

[DISAR]

Many thanks ReddyWatts. I am just comparing results of my boat actual values with FE program and OSE formulas. Please allow me to mention that the FE program is good only for the Amps estimation, at least for my boat 36" mono and using the "hydro-performance". I had taken measurements with Eagle Tree. All the rest are inaccurate (propeller wizard, speed). The OSE formulas are very very accurate but missing the Amps calculation. Therefore, if the Amps calculation is inserted in the OSE formulas it will be perfect.
I am a bit confused anyway.

[Steven Vaccaro]

The ose calcs are just basic speed formula's. You still need experience with what size motors to use in what size boats. Reading the forums is a good start. Seeing what other people are using successfully. The problem is some people exaggerate or believe that their setups are faster than they really are.

[DISAR]

I am reading the posts and have obtained very useful information. I am just doing these calculations again because I face some heating problems with my ESC. Maybe it is because it is summer time and sea water temp. is higher (75 F) and not sufficient for cooling my ESC. Added also a fan but not tested yet. Have fun

[ReddyWatts]

Yes, the Fe program has not worked as well for 4 or 6 pole motors. It was designed for 2 pole motors like Fiegao and KB. You will mainly get an estimate, ball park figure. It will give you an idea of where to start with a setup. It is the next best thing, without experience. That is why you ALWAYS start with a small prop and work upward to your desired amp readings.