Battery disconnect switch

I am building an electric bike with a 13s5p battery that is removable. But I am a little concerned that I will get sparks when removing the battery, that will damage connectors and maby controller and bms. The problem is that I don´t have anywhere to easy mount a main circuit breaker.
How big of a problem is it, I will probably remove the battery from time to time?
If I do mount a circuit breaker, will just a 1kohm resistor between the terminals of the breaker be a good way of doing it?
So when the switch is off, there is still connection over the resistor until I unplug the battery.

I want to keep it as user friendly as possible, so that my girlfriend can use the bike. I could have an extra switch for the resistor, but I am worried that it will be too complicated.

It's not going to damage anything except possibly the connectors, periodically checking and cleaning those is probably all you really need to worry about. I unplug my battery every time I charge it (at least daily) and the connectors are still fine. There's a tiny spark every time I plug it in but I think they're good for at least several hundred connect/disconnect cycles.

You shouldn't get a spark unplugging it, there's no voltage difference between the battery and the controller at that point. Where you'll get a spark is connecting the battery to a controller that's had time for it's capacitors to drain, in which case there's a large difference between battery and controller.

Thank you, that sounds good enogh for me. I was mostly conserned about damaging the controller with power spikes. But then it probably is not that big of a problem.

Is it a ready made commercial battery or a custom one? If custom, you should be able to add a precharge resistor or use a connector with one already built in to prevent the spark when connecting the battery to the controller.

What he said ^^^^^^

Here's a simple hookup that just uses a mix of one an two pin connectors. Easy with either Anderson PP or RC bullets. With a little heat shrink sleeving it just looks like a short Y on each side.





20-22ga is more than adequate for the precharge wire - the size is more to get physical robustness - anything on hand is okay. Similarly, the current in the resistors is modest and very brief - a 1/2W to 1W size is more than adequate and has sufficiently sturdy leads. Since we know the precharge current is transient, it's not strictly necessary to use a large 5W - 10W resistor part that would be necessary if the current was steady state.

Sleeve the whole resistor and a bit of the precharge leads alone and then together with the larger main power lead to reduce flexing of the more fragile resistor leads.

The resistor value depends on the desired precharge period and the size of the controller caps. 330ohms is fine for most situations and gives around a 1-2 second precharge time. Values up to about 1K are good - just the charge time gets longer. Your mileage may vary...

This is simple stuff so do what's convenient. For instance, I have a bike with a battery that came with two individual bullets already done up tidily so I just made up the controller side with three individual bullets - a single black (neg) and two positives - one the precharge. I plug in the black first, gently push the precharge on for a couple of seconds then unplug it and plug in the main positive. This might not be what I would build for a non-techie, but it works dandy for my personal use.

Please recommend a resistor value. Thank you.

Okay - added some notes and a more detailed illustration above. There are precharge calculators on line if you happen to know the cap values in your controller...

I use an XT90 connector with spark arrest. That works just fine for me.

When I’ve a battery equaliser connected I get no spark on a 10s 13p. FYI.