ESCs for 18V 775 Motors

[Giles]

Currently looking at building a feather for the champs in April, I've bought a few parts and want to start testing things. The ESC's which I've been recommended are the BotBitz 80A ones, but I'm not ready to drop £100 on two ESC's for a project I'm still trying to get my feet wet with. I was just wondering if anybody had some cheaper options that they have had success with in the past?

I've ordered some of the cheap chinese "320A brushed ESCs" from a UK supplier, which of course are nowhere near that amperage rating, but I'm going to try and upgrade the connectors and wiring in hopes that it can withstand the draw from the 775 motor. Bit of an experiment, but if it works then its an ESC for only £10.

I know the general consensus is "you get what you pay for", and i totally agree. I will no doubt buy myself a pair of BotBitz ESC's in the future, but for now, I just want to be able to get my bot driving around the garage so I can test out various aspects of its design before commiting to spending a lot on it.

[typhoon_driver]

Hate to say it, but you've wasted your money on those "320A" escs. If they don't burn up, you won't be able to sell them. Money down the drain and they won't do the business in the arena.

You might be able to find a set of electronize cheap second hand if you put a post in the wanted section which would do the job better than the 320A esc.

[plargen]

If their the ones that can handle 16v and have the then they will probably work as ive usiveed them in my 2 and you can run 2 550 drill motors at 4s on each esc but I found that you either need a gyro or a good transmitter strait line

If your over volting them then they probably wont last long and there are also 2 versions 1 will go from forward to reverse with no problem ant the other stops when u slam it into full reverse making driving a proble so I hope u get the good 1s

[Giles]

We'll see! Yes indeed they are the 16V versions, and I'll be be running them on a 4S lipo, so it should be fine on the voltage side of things. The reversal thing sounds like firmware problems, I wonder if I can flash them with different firmware? Hopefully I won't need to though and they'll be the right ones.

[Matthew]

I believe I am using the same ESC as you. I had a problem with having too lower ampere, yet for me 3s 2.2 amps lipo on each work well, using 12v drill motors.

[Rapidrory]

I had a look at various of these cheap ESCs with mixed results... Have a look here: http://www.fightingrobots.co.uk/thre...heap-drive-esc

General consensus was though that the 20A ones work with 550s after a lot of modding, but those "340A" ESCs are pretty naff for anything larger than a 550 even with mods..

[daveimi]

If you're struggling for cash have a go at the smaller weight classes first.

[Giles]

It's not that I'm struggling for cash. I just want to explore cheaper avenues before settling with the expensive "it just works" option I am building a beetle at the moment too though!

[Rapidrory]

I wanted a cheap option for my first featherweight, so I opted to build my own ESC.. Cost me about £25 and lasted fine for 12 fights before blowing up in testing. Got a pair of those cheap 20A chinese ESCs, and they lasted a good number of fights before blowing up, then I stuck my heavyweight ESC in there whilst waiting for my next design of ESC to be built, then my next ESC blew up on the first day of the championships, so I've stuck a 5th new one in there now, and this is all within the space of one year.. In total I've probably spent over £150 designing and building these ESCs, and they're always the main point of failure with my bot (though getting more reliable as I get better ), and all but my heavy ESC wouldn't be good enough to drive those 18v 775s. On the other hand, if I'd just bought a pair of TZ85s I'd likely have had basically no problems all year and only spent £60 (would reprogram them myself as that's easy enough). Picture below shows all but the latest version (which is currently in my feather), and is in the order of oldest on the left.



Sadly don't think there is a cheap option when it comes to ESCs, unless you're already experienced in building them (I can build my own for <£20 now). I would still encourage more people to try building their own; I've learnt so much from it and developing new controllers is one of the most interesting parts of the sport for me, but in the long run it's not necessarily cheaper.

[Giles]

So, Rapid, between you and my teammate, I've been convinced to try and build my own ESC's. Even if its a failure it'll be an experience. My team mate, Dave, is a bit more in touch with electronics than I am, so he'll probably be doing most of the work on these. One thing we're both wondering though is how stall currents are handled. Do your ESC's have a way to protect themselves from the high stall currents? Or are they simply beefy enough to deal with it? I was planning on using an ATMega control board to read currents across the circuit and apply a pulse to the input power when it goes too high, bringing it back down to a reasonable level. But maybe I'm over thinking this?