hi everyone, i'm travis from california

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hi everyone, i'm travis from california

Postby tlscheiber » 13 Apr 2017, 23:15

i'm building a 4 wheel drive chair using permobil parts. I have chopped the backs off of a c500 and a c400 frame and welded the fronts together to utilize the motor and shock mounts plus central battery box. I plan on a skid steer control system utilizing two motor controllers in pair. I have the hardware and wiring all sorted out, but have the power and control of the motors left to do.. because I don't know what to do. I have 2 pilot plus controllers w/esp modules and am considering splitting the joystick cable to connect with both. is this wise or incredibly foolish and dangerous?

travis
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Re: hi everyone, i'm travis from california

Postby Burgerman » 14 Apr 2017, 09:11

I doubt it will zero turn reliably even with 2 controllers, because the battery cant provide enough amps. At least not if its geared for any sensible speed. Unless you plan on 4 batteries too. Connecting analog joystick outputs to two pods? Should work...
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Re: hi everyone, i'm travis from california

Postby tlscheiber » 14 Apr 2017, 18:10

on battery output..

I have the standard (2) 12v 73ah sla battery wired in series, which is insufficient as you have stated. would something like (4) 6v 50ah batteries be any better? it may be a bone-head assumption, but if (4) 6v in series produce 24v, would they also produce 200ah?
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Re: hi everyone, i'm travis from california

Postby LROBBINS » 14 Apr 2017, 18:29

No.

In PARALLEL increases AmpHrs, and leaves voltage unchanged.

In SERIES increases voltage, and leaves AmpHrs unchanged.

Thus,

two 12V, 73Ahr batteries in series gives 24V and 73AHr.

four 6V, 50Ahr batteries in series gives 24V and 50Ahr - a losing proposition

four 12V, 73Ar made up as two pairs in series to give 24V and 73AHr per pair, then the two pairs in parallel gives 24V and 146AHr

Note that those lead battery AHr capacities are at a slow and steady 20Hr discharge rate. A wheelchair draws much higher current when maneuvering and capacity will be much, much less. The harder it is to maneuver, as is the case with skid steer, the worse the battery performance.
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Re: hi everyone, i'm travis from california

Postby Burgerman » 14 Apr 2017, 18:41

If you think the motors, stock controllers, are capable of turning something by sliding its tyres on say tarmac or dry grass you are in for a shock. Skid steer will only work properly with a lot of power, bigger motors, very low gearing/speed, and lithium battery power. Lead doesn't work, adding more just adds weight and makes it harder to turn... Tested.

Works OK for a kid. if extremely short wheelbase and low speed gearing. After that then not really unless you want to turn only by going forwards or backwards.

Imagine how hard you would need to push sideways to turn your car around in the street on the spot, by sliding its 4 tyres sideways, compared to pushing it forwards. Or a chair with casters.
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Re: hi everyone, i'm travis from california

Postby tlscheiber » 14 Apr 2017, 21:10

thanks for the info, I am sticking to two drive tires. still gives lots of options for off road.
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