3S or 4S

[gencode]

I want to say thanks because I have learned a lot about batteries from you and the guys. I now run 2 2200 4S in parallel with a Y Connector. To keep them safe I always charge first and keep charged ones separate. I have my ExOSD set to 3500 to land.

Today I found I had a bad Deans solder on one battery and was very happy I had a second battery as a backup.

But now after only about 7-8 flights my flight time has gone down to 5 minutes. That seems pretty fast, so I tried them one at a time and only get about 3 min on each. They were 5 min.

Now that I have seen how 2 batteries can "save the day" I only want to fly 2.
But I still am unclear on if I should use 3S or 4S
I mean 3S is lighter (I think) than the equivalent 4S

 

[Benjamin Kenobi]

Hi. I run two in parallel and find the lipos have a much easier time and don't get warm. I run 3S but 4S is said to be more efficient. Stick with 4S in parallel.

 

[gencode]

Thanks Ben, I guess Im weighing the benefit of efficient packs vs weight of the craft. The main reason id want to go to 3S would be to make it a little lighter.

By more efficient you mean the 4S would have longer flight times I assume.

Hi. I run two in parallel and find the lipos have a much easier time and don't get warm. I run 3S but 4S is said to be more efficient. Stick with 4S in parallel.

 

[ChrisViperM]

It's not that simple and always a topic for serious hefty discussions. Every BL-motor got a few parameter which tell you what you can do with it...and what not.

Very important is the so called "KV-Rating" which tells you the RPM per every Volt you put on....if a motor got a KV-rating of 950 RPM and you use a 3-S Lipo (3x 3,7V = 11,1V) = 11,1V x 950KV = 10.545 RPM max. With 4S you get (4x 3,7V = 14,8V) 14,8V x 950KV = 14.060 RPM max. Thats a big difference already in your RPM which you have to compensate maybe with same smaller blades, you must also check if your ESC can handle 4S, also 4S is more weight than 3S....and that damn "sweet spot" of top efficency is hidden somewhere in between......most of the time all the academical aproach might help you to get into the right direction, but most of the time it's trial and error to get what you want.

Chris