Voltage Increase

So as we all know, the Wireless Aerial Surveillance Platform has less than desirable flight characteristics. Mostly this is due to her being very heavy, which we are currently working on. The motor however is also being under utilized.

The E-flite 90 brush-less out runner we are using can support 6-8s (21.6v-28.8v) lipos. We are currently using Thunder Power RC 6s 20c 5000mAh packs. We didn’t want to have to purchase 4 new 4s packs and run 2 sets in series to achieve the desired 8s voltage. I wasn’t positive that using a 6s and a 2s would work the same as 2 4s packs, as Lipos are very sensitive to being over discharged. I sent an email to Thunder Power some time ago regarding the use of a 2s 5000mAh pack run in series to bring us to the desired 8s voltage. The response I received is encouraging.

Email from Thunder Power RC:

It is OK to run different (or the same…per personal preference) series cell count batteries in series, like 2S and 6S to achieve 8S. However, we do recommend that the cells be of the exact same series, for example, 2S 5000mAh Pro Lite V2 20C and 6S 5000mAh Pro Lite V2 20C used in series as 8S 5000mAh Pro Lite V2 20C, whenever possible.

And while it is possible to use other model 5000mAh batteries in series, for example, 2S 5000mAh Pro Power 45C and 6S 5000mAh Pro Lite V2 20C used in series as 8S 5000mAh, it is not typically recommended unless you are monitoring individual cell voltages during discharge or do not use more than 60-75% of rated capacity as the batteries can discharge at different rates (due to the differences in the internal resistance and other performance characteristics of the cells). Also, you must be sure to not exceed the performance capability of the lowest discharge rate capable battery used.

It’s also important to ensure that the batteries, whether charged separately or in series (and especially if charging in series), have the individual cells charged (or discharged for charging) to approximately the same voltage for use. For example, if the 6S battery is charged to 4.18V per cell (25.08V total), the 2S battery should also be charged to approximately 4.18V per cell as well (8.36V total) before discharge. And, just in case the ages/conditions of the batteries are not exact, you should not discharge them beyond 80-85% when used in series as the cells in one battery may discharge at slightly higher rate than the cells in the other battery (again, due to the differences in the internal resistance and other performance characteristics of the cells).

We hope this information is helpful and still useful.

Thank you again and best regards,

Jason M.
Thunder Power RC/SebArtRC
Visit the all-new www.SebArtRC.com

Thanks Jason, it is indeed very helpful. Now we know, if the diet is not enough to improve flight characteristics, we can add voltage without breaking the bank.
Compare
2 of these 2s 5000mAh 20c @ $79.99 each
vs.
4 of these 4s 5000mAh 20c @$149.99 each

Of course the long term solution is an airframe with a much better wing load and glide slope…all in good time.

WhiteQueen

About WhiteQueen

An avid radio control enthusiast and a senior security engineer supporting the U.S. Government. He has had a 20 year Information Technology career including programming, Enterprise Administration, and Information Security. Hobbies include hiking, SCUBA diving, R/C, computers and electronics, as well as a penchant for voiding warranties.
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