In order to run 2s, the Mobula 7 comes standard with 2 x PH2.0 connectors that allow you to run 2 x 1s batteries in series. When running in series the strength of the connection is determined by the weakest link in that circuit. The strength of connection determines the maximum current that can pass and the voltage drop that results. Although it works this system has a very low current overhead from a design perspective - 2 x budget PH2.0 connectors with the dreaded 'folded' pin and very lightweight 26AWG wire. All this adds up to a lot of voltage drop when even reasonable current is pulled - something all will be familiar with on the mobula where you see voltage drop to scary levels (6v and below) during punches even when you have a full battery. Although it recovers almost immediately it does mean you don't get access to the battery's full voltage potential.
This is the second article in my series of HappyModel Mobula7 upgrades, many of which can be used for the Trashcan too. Also to come are:
Why not XT30?
I'll address the elephant in the room - short answer is weight. The JST connector is lighter than the XT30 and has plenty of overhead on this quad considering it only has a 4x5a ESC (20a max). I've also had history of using both on my larger 1.9" ultralight build before too and the JST was not left wanting. The only reason I would go to XT30 over the JST in the future was if I needed more durability. (photos to follow shortly comparing weight)
Going ahead with this mod means you'll no longer be able to use 2 x 1s batteries as before unless you make a harness of female JST to 2 x series PH2.0 I'd strongly recommend against this though as this adds weight and a lot of extra resistance. Assuming you have upgraded to the Eachine trashcan/mobula v3 frame as covered here (which is honestly the very first mod you should do) then there are 2 batteries I can strongly recommend:
If you do not have a balance charger, you will need one to charge these 2s batteries or ay other multicelled lipo battery. I use the hobbymate pro 2 duo (reviewed here) - a little more expensive but so versatile.
What to do with you 1s batteries you have left? I have an article coming to show you how to convert these to proper 2s batteries you can use with this new connector alongside the GNB or nanotech batteries.
How to install
Before I launch in with pics and steps I'll say although quick this is a fiddly install only because the solder pads are small in relation to the wires you will connect to them. I do have a method to confirm everything is safe but you have been warned!
I probably spoiled the suprise earlier but this mod is well worthwhile. I skeptical but really pleased to find the standard battery sag issue was instantly improved meaning I didn't have to guess at how much battery I had left as before finishing my flight. In addition I seem to have access to more power more quickly meaning response feels snappier. Also on long punches thrust seems to remain more consistent. If you have a good soldering iron and are a confident solderer I'd definitely recommend this one, particularly if you are running the v3/trashcan frame. On my year old 2s 300mah turnigy nanotech batteries I got just over 3 minutes of hard flying in a large area. During that time voltage did not dip below 6.8v and then only toward the end. Compare this to dips below 6.0v with the original setup in the first minute of light. This large voltage drop is less to do with the battery and more to do with the poor connection on the original setup hence the improvement to power. As a side bonus this should mean power will be more consistent to the VTX and receiver as well for more consistent performance. All in all I can recommend this mod but stick with the 22AWG wire and bear in mind the change in battery requirements.
Up next - easiest way to reverse motors (props out) without using BL_Heli Suite
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