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I'm doing research on a remote control model ship. I have 11.1V LiPo batteries, but because of their weight and duration, larger batteries are considered better in this application (these batteries come were originally for RC airplanes, where lightness is key.)

My battery would go to an ESC, then to an electric motor. I have read that true, non-nominal voltages of LiPo batteries are higher, somewhere closer to 12.6V at peak. Because a 12V battery rating is also nominal, I understand it might be necessary to use a resistor or some other means of reducing voltage, but I do not really know much about how current flows, charge rating, cell count, etc.

The ESC being powered would be something like this, rated at 40A, and there would be a motor like this on the end, rated for 2s to 4s batteries. I'm assuming these ratings are just to guide people using standard material. Also, I actually have two ESCs and motors, but they are both plugged through the same receiver.

This would be the normal max power, from what I understand from this article:

power = voltage * current
480W = 11.1V battery * 40A ESC

Using this lawnmower battery for example, this would be the max power output (I think?):

420W = 12V battery * 35A battery rating

There could be something terribly wrong with this calculation, but it does look like it would work, while supplying a little less wattage, but likely allow a longer use period. Note that I used the amp rating of the battery for the second calculation, since it's lower than the ESC's max tolerance. Again, I could be mistaken. I've heard scary things about the power of 12V car batteries to solder metals together.

So I'm wondering, what arrangement would be needed to power such a system through something like a 12V lawn mower battery? Is that possible, or will this fry my ESCs, motors, and receiver?

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    \$\begingroup\$ I'm not sure, but I think you're asking about "How much energy do the batteries hold" when you're describing power above, yes?? Your equations tell you how much instantaneous power (maximum) the battery can deliver, not how much energy they store. That's described in mA-hr (Milliamp-hours) or A-hr (Amperes - hour) or sometimes W-h. For example, a 1000mA-hr could provide 1000mA for one hour, or 100mA for 10 hours, etc.. Is that what you're seeking??? Your controller is only looking for 3A output - That's a fraction of what the batteries can deliver. \$\endgroup\$
    – Kyle B
    Commented Apr 23, 2020 at 16:46
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    \$\begingroup\$ The brushless motor plugs directly into the ESC. The ESC delivers power to everything else. Check this block diagram. ftforumx2.s3.amazonaws.com/2017/06/… \$\endgroup\$
    – Kyle B
    Commented Apr 23, 2020 at 17:12
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    \$\begingroup\$ Don't take that diagram TOO literally of course ;) It's just an example. Refer to the technical data for your actual parts. And BTW, you are right, a 12V car battery most definitely can "melt metal" :) I've seen some (poor) arc welding done with just a few car batteries. \$\endgroup\$
    – Kyle B
    Commented Apr 23, 2020 at 17:16
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    \$\begingroup\$ :) OK - I got ya. So really your question is "Can I use a 12V lead acid battery instead of 11.1V LiPo" ? Sorry it's taken this long to get that into my head LOL \$\endgroup\$
    – Kyle B
    Commented Apr 23, 2020 at 17:19
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    \$\begingroup\$ This kind of thing is done, and there is indeed substantial overlap in the ranges of the differently shaped voltage curves of a 6-cell lead acid battery and a 3-cell lithium polymer. Actually determining if this is workable depends on knowing details of the items which you have not provided. That is typically the reason why product usage questions such as this are off topic on this site. You will do better on an R/C boating forum, especially if you can find people familiar with the particular ESC and motors you want to use. \$\endgroup\$
    – Chris Stratton
    Commented Apr 23, 2020 at 17:25

1 Answer 1

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The output voltage from a standard Li-Ion or Lipo battery pack with (3) cells in series (3S) ranges from about 12.6 Vdc (freshly charged) down to about 9.0 Vdc (end of life cutoff-voltage).

A standard 12V Lead-Acid battery ranges from about 14.5 Vdc (freshly charged) down to about 11.0 Vdc (end of life cutoff-voltage.

Best to check the datasheet for the device(s) that you are powering. However, my past experience says that you can safely substitute a 12V Lead-Acid in place of a 3S Li-Ion or Lipo battery pack.

[Edit] One thing to consider that Li-Ion or Lipo batteries have FAR greater energy storage as compared to a Lead-Acid battery of similar size or weight. Lead-Acid batteries are significantly less expensive than Lithium technology. That is one of the few advantages that Lead-Acid batteries have compared to Lithium-type batteries.

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  • \$\begingroup\$ Update: I actually realized that the ESCs I ordered were compatible with 2-4s LiPo batteries, which have a voltage from 7.4V to 16.8V. Therefore, a 12V battery should be well within range. \$\endgroup\$
    – Denis G. Labrecque
    Commented Apr 27, 2020 at 20:41

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