I have a ef 91 yak on electric 360 e- flight motor on 12s, 2 5300 45c, can I add 2 more batteries same c rating but only 1800 ma, but keep as a 12s, I'm looking for just a little more flight time. I have the 2 6s 1800. Thanks

No. WIthout some kind of sharing/regulation you will run the risk of draining the 1800 below safe voltage. It will then be a bad situation.

You can run 2S2P, but run them with same capacity batteries.

ok thanks

so you would have to use all the same ma, batteries

Yes. Do NOT run different capacity batteries WITHOUT some kind of distribution system...

either way, its cheaper to spring for new batts.

the results could could cost you your airframe and electronics

hope this helps

Thanks for you help, Time to save and maybe 6s 6500. It fly's awesome I will not chance it, I could get more time but I'm a little hard with the throttle, I have learn to back off a little more. Thanks again

Originally Posted by rwhitlow

You can run 2S2P, but run them with same capacity batteries.

FWIW when I was racing electric boats I ran a 10S2P set up using a 4S and 6S in series to form 10S and then the same 4S+6S in parallel to get 10S. Using all 5,000 mAh packs I had 10S power with 10,000 mAh capacity. That was good for about 1:45 of screaming fun!!!

Also, packs in parallel (same cell count) will contribute to load based on their respective capacities. So a 2,500 and 5,000 pack feeding the same load will run down at the same time. Connected to the same power bus they each must maintain the same voltage, and as such, the larger capacity pack will carry more of the load at any given time, but they will both reach discharge at the same time.