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

[marto]

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

Just a quick heads up that I am working on a 150A version for some middleweights of ours.



So might be possible to use it in a Heavy soon.

Steve

[typhoon_driver]

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

I'd like to know what the actual current handling capacity of these is beyond the hobbyamp figures as there is no way in hell it's actually 85A continuous. Granted I've bought a couple to play wtih and i'm sure they will be fine in a featherweight but just from their size etc I get the feeling they are around the 20 to 30 amp continuous range for 5 minutes.

[shakesc]

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

even in a featherweight beefing up the heatsink is no bad thing

[craig_colliass]

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

From the specification given for these controllers they could work if used in tandem.

The maximum voltage at 25v may be a little restrictive as many people use a little more than that.

Quote from Specifications.

1 Specification
This ESC has been flashed replaced with custom BotBitz firmware in order to allow it
to be used for brushed motors. (Brushless motors will no longer work)
ESC do not have current or temperature limiting and overcurrent and situations
will result in damage to the ESC.
1.1 Current Capacity
€ 200A burst <1s
€ 85A for 1min
€ 60A for 2min
€ 40A for 3min
For more information see the graphs in testing section.
1.2 Voltage Limit
Max Voltage 25V
Lipo: 2 - 6S
NiMh/NiCd: 5-18S

[plargen]

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

with that spec you could probably use them with wheelchair motors as most are 300w or less

[blazerbotics]

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

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

[maddox10]

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

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]

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

http://www.youtube.com/watch?v=DGJjQJEdeec

I'm just gunna leave this here.

[TeamMental]

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

I would wonder if these ESCs would work with a heavy

[archie2000]

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

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

[Ellis]

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

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]

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

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]

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

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]

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

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.

[PJ-27]

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

Are you saying they brown out from interference caused by the motors?