Using a Toggle Switch to Connect/Disconnect LiPos?

[HacknMod]

I'm building an electric unicycle and I want to be able to use a toggle switch to switch my batteries from "charge mode" to "run mode" and vice versa. Is this a good idea (please see diagram below)?

I'm worried that if I switch from one mode to the other, the mechanical "bouncing" which occurs might be damaging to the LiPos?

Thanks!

 

[dogman dan]

The real problem is you will need a monster of a switch. More expensive than it's worth. A small switch will just cook off.

The majority of us are just using cheap and easily replaced connectors. Sure, it hasn't the elegance of a switch, but once you build your plug blocks the right way, you can easily swap from series connections to run to paralell connections to charge. A block of connectors is attached to the battery. Then you have a wiring attachement for each use, one makes a series connection and is on your vehicle. The other makes paralell, and is on your charger.

Icecube 57 can make you a set of wiring harnesses to do the job if you wish.

 

[HacknMod]

The real problem is you will need a monster of a switch. More expensive than it's worth.

True, a switch that large is expensive. I sampled the S821D though, so I got it free and I'd like to use it. Given that I'm going to use the switch, does anyone foresee any problems with using said switch?

 

[nicobie]

I tried a couple of them as a battery disconnect switch for a 22s battery and while it would disconnect fine it couldn't take the connect with out welding the contacts even though I was using a 1k pre-charge circuit. When I switched to a 250 ohm resistor it worked OK. It might be fine with a lower voltage battery. Give it a try, you'll find out soon enough...

 

[HacknMod]

I tried a couple of them as a battery disconnect switch for a 22s battery and while it would disconnect fine it couldn't take the connect with out welding the contacts even though I was using a 1k pre-charge circuit. When I switched to a 250 ohm resistor it worked OK. It might be fine with a lower voltage battery. Give it a try, you'll find out soon enough...

Interesting. I'm switching two 6s batteries together in series, so maybe it won't be an issue?

 

[Kin]

Out of curiosity-How are you approaching the problem of the crankshafts? Unicycles, I understand, not freewheeling, so your crankshafts will go spinning at the speed of the wheel.

 

[HacknMod]

Out of curiosity-How are you approaching the problem of the crankshafts? Unicycles, I understand, not freewheeling, so your crankshafts will go spinning at the speed of the wheel.

I'm not really a mechanical guy, but if you're asking how I will stop the unicycle from spinning out of control while going downhill, the answer is to instruct the wheel to go backwards while it's spinning forward. This will act as a generator and put power back into the battery pack.

So...is the toggle switch safe to use?

 

[Kin]

Ok, I see you are not trying to go faster than one could normally unicycle themselves, then. Otherwise, I was thinking if you are going for, say, 20 mile an hour, and the wheel size put your max pedaling speed at 15 mile an hour, then your feet would have problems keeping up with the motor. Good point on using the regen braking for downhill.

 

[HacknMod]

Ok, I see you are not trying to go faster than one could normally unicycle themselves, then. Otherwise, I was thinking if you are going for, say, 20 mile an hour, and the wheel size put your max pedaling speed at 15 mile an hour, then your feet would have problems keeping up with the motor. Good point on using the regen braking for downhill.

I should probably clarify that this is a 100% electric unicycle - There are no pedals for human power.

 

[Kin]

I brought the thread a little off-topic, but thanks for the clarification

So...is the toggle switch safe to use? would be where the thread should re-continue .