Originally Posted by
Overdriven
I've always wondered if this was possible but had never read about anyone who had done it. My experimentation with an EVX2 was brief, came with a truck and was done mostly to see what a dewalt could do.
Bypassing the bec side does eliminate that particular voltage restriction on this esc. But there are other voltage restrictions in the esc, namely the capacitors and mosfets. Sure there's usually some headroom built in but there's always a limit that you can't just throw away. Open up a MMM and you'll find 25v rated capacitors, doesn't matter what you do to the Bec the capacitors won't take more than 6s. In the EVX's case 18v capacitors would've provided some headroom for its intended 16.8v but they obviously must've used higher rated capacitors if it can survive 5s and 6s. The mosfets can usually take more voltage but the control circuits that connect to the receiver and tell the mosfets to open and close is anyone's guess.
Yup, gotta be concerned about amp draw. Increasing the weight with more batteries is going to increase the amp draw. How much? Probably about the same amount as increasing the pinion size 3 teeth would. As far as the rpm limit of the esc, that's only for brushless and doesn't apply to brushed motors.
I don't get out to many other forums these days so I haven't seen this and couldn't find any in a quick Google search. I did find a post on rcgroups a few minutes ago stating some EVX2's won't run right over 23v. Guy hooked up an adjustable power supply to test and got funky throttle response over 23v. But there's been numerous revisions to the esc and this was one guys test.
Sorry for the long post. And don't take it as picking anything apart I love discussing this stuff. Don't forget to show us what you come up with.
I love talking tech. So no problem overdriven. Yes I found the same post. Also this.....
"I just received today 2 ***** 5S 20C Lipos from Hobby King, 5 days from purchase to delivery in Scotland from Hong Kong is pretty impressive. As I have the setup you are thinking of running - 14V DeWalt motor and stock EVX2, I thought that in the interests of science I'd give them a run or two with the DeWalt motor before installing MMM combo which is sitting on my workbench awaiting the arrival of Spectrum 2.4GHz .
Battery connectors changed to TRX type and lipos balanced/charged. All 10 cells were 3.85 or 3.86 volts as delivered before charging, I mention that because I have heard of some Zippies being way out of balance when new, no problems with these.
First, the batteries are a tight squeeze in the compartments but after removing spring clips at the top and the 2 retainer tabs , they were in and the doors closed - just. The power cables need a bit of persuading into shape to come out of the slots, maybe need a bit of a mod to the compartment door to make this easier.
Parallel harness and jumper connected, it's time for a trial run in the garden. After a bit of a careful warm up to make sure nothing was going to smoke, everything was fine. The extra voltage sure makes a big difference to the power of the DeWalt - flipped straight on its lid from standstill on paved area with good traction, not that I condone that sort of behavior . Torque and top speed were also much improved over 4S setup.
After 15 minutes of driving I thought I'd check on temperatures and, in the absence of a 5S LVC, the battery voltage. Motor was pretty hot compared to running 4S, sorry I don't have temperature reading , no temp gun yet. ESC was a good bit hotter than on 4S as well. Lipo voltage still at 20.1V, no problems there. Ran for another 10 minutes and thought it safer for lipos to call a halt and recharge. My gearing was 20/68 as it has been for running 4S.
So far, so good. I was very impressed with the performance increase, if it could run reliably on 5S it would be an ideal waterproof alternative to going brushless. The biggest concern was how hot the DeWalt motor and EVX2 were but without a temp gun I can't be sure it was anything to be too worried about.I'll try another run once my temp gun arrives.
Also, I couldn't find a 5S LVC or even a 5S low voltage warning led, which is all I use for my 4S setup, just something else to consider if you go for this.
So, it's all down to how reliable this setup is, I might just postpone my MMM install to see how it holds up, I suspect it's on the limit of what both motor and EVX2 can handle and it will run hot or overheat."
He was using the internal BEC I think with a external bec it would work even better. I just tried 6s (3 and 3) on the evx. It was very glitchy. So that is a no go on the internal BEC. I have a castle external bec I may hook up tonight. When I do I will post my results on 6s