Botbitz 85a esc..... in a heavy?

**blazerbotics** · 30th January 2013, 17:07

Voltage is the problem, every heavyweight runs on at least 24volts (20 Nicad/Nimh Cells).

**maddox10** · 30th January 2013, 17:17

Originally Posted by blazerbotics

Voltage is the problem, every heavyweight runs on at least 24volts (20 Nicad/Nimh Cells).

Easely enough replaced with 1 or 2 these pack. Saves a lot of weight, probably cheaper than 60 NiMH cells and accepted in heavies.

Other option is 4 of these.

I agree, it's a small drop in voltage, but nothing you can't solve with the right motor and gearratio. The few amps you'll draw more to compensate shouldn't make the problem.

**marto** · 19th February 2013, 14:50

I'm just gunna leave this here.

25th March 2013, 01:22

I would wonder if these ESCs would work with a heavy

**archie2000** · 25th March 2013, 10:42

are they just botbitz tz85a with heatsinks in the top picture?

**Ellis** · 25th March 2013, 10:50

It's a bit cleverer than that. They are two tz85s linked so that they work as one big speed controller. If I remember correctly they're being rated at something like 150a, which like the tz85s won't be their literal constant current handling ability but they'd take that sort of figure for quite some time.

I believe Botbitz are building middleweights to test these speedos for Robogames/Combot Cup this year, so we'll know more soon.

**Merkabah_PT** · 25th March 2013, 14:21

Link for the BotBoitz Middleweight with the dual tx85s:http://robowars.org/forum/viewtopic....er=asc&start=0

Video: http://www.youtube.com/watch?v=AA7exuzUyGo

**marto** · 28th March 2013, 14:13

So... I gave up on the 150A version. It looked promising and I could easily pull 500A through it but the idea of pairing up two TZ85as is inherently flawed.

It all works fine until one of the ESCs browns out. And if you happen to be using very low inductance motors, like I am, this can happen even at very low PWM duty cycle. If the motors are stalled even at low throttle this can cause the input voltage to drop very low and the ESC to reset. As there is communication between the two paired ESCs to ensure they are synced and running properly this means that if they don't reset at exactly the same time or if one powers back up first they can enter a situation where there is shoot through in the ESC causing it to blow up.

There is no way to solve this with software. It could be solved in hardware but its easier to just use a different ESC. For the middle they are 2 85As running on separate brushes. I do not know how much current is coming out of the batteries but I think it is a lot. The 8AWG wire from the batteries is too hot to touch after just a few minutes of driving. So it will be interesting to see what happens.

Steve

**Merkabah_PT** · 28th March 2013, 14:20

Good luck at the robogames Steve!
I admire your work and projects very much, the hacked brushless esc's are a genius idea, allowing people to have good and cheap esc's.