Is there any point adding a switch?

[Manc44]

I got a battery with no switch and the first time I connected it there was a spark.

I assume that was the capacitor in the controller taking some current for the first time ever, because about 10 mins later when I reconnected the battery, there was no spark.

Each time I had everything plugged into the controller with the battery the last thing to get connected.

Is there any point putting a switch on it?

I have seen cables that have Male XT60 > Switch > Female XT60 and they are dirt cheap, rated at 20A, for example:

XT60 20A Switch Harness

This Switch has a male and female XT60 connector attached and has an easy access charging socket. SpecificationsPower rating - 20AConnectors - XT60

iactiverc.com

My controller is 18A (+/-1).

It's another two XT60 plugs to go wrong, but it would stop sparking, but if the capacitor holds its charge for a few days, it doesn't matter anyway.

What I am wondering about more than anything is, how long do the 63V capacitors typically hold their charge in these controllers?

If the switch did fail while out riding, I could just unplug the two XT60 plugs and directly plug the battery to the 1T4 cable like I am now, without a switch.

I just thought it odd that it sparked the first time connecting it but not the second time.

It seems you have to sort of fool it into not sparking and connect it quick when it's got it's not expecting it lol.

 

[vfr400]

A switch won't help you, wspecially one rated at only 20A. The inrush current is many times that, and it will burn the switch contacts or etch them away until they can't work. All you've done is shift the problem from the connector to a switch.

 

[Manc44]

I don't want it giving me a belt lol

 

[vfr400]

I don't want it giving me a belt lol

It can't give you a shock. It's just a noise.

 

[Manc44]

It can't give you a shock. It's just a noise.

And a visual lol... but you said a 20A switch won't cope with it because way more than 20A can go through it on connection. How can it not give me a shock? After the first time connecting it I put rubber gloves on the next time!

 

[wheeliepete]

You could fit xt90s anti spark connectors. Beware of fake ones, they don't work.

Pardon our interruption...

 

[vfr400]

And a visual lol... but you said a 20A switch won't cope with it because way more than 20A can go through it on connection. How can it not give me a shock? After the first time connecting it I put rubber gloves on the next time!

The volts are too low to give you a shock. The electricity can't get through your skin. It's completely harmless to you. Only metal things need to worry because it eats them. The current flowing is thousands of amps and the power is transfered at hundreds of kilowatts, but it only happens for a very short time.

 

[Manc44]

Cheers folks. One thing I wondered is how long the (63v) capacitors hold their charge in the controller, because if that is holding enough of a charge, it stops it sparking anyway, right? At least, the 2nd time I connected (15-20 mins after the very first time) there wasn't a spark.

 

[Nealh]

The capacitor will self drain/discharge slowly over a period of many hours.
To get any real shock off DC you will need higher voltage say more then 80v.
If you lay your bare arm across a battery cell pack of nominal voltage of up to about 60v you will get a slight tingling sensation, when you crack your funny bone the effect is 4 or 5 times worse then a low DC voltage tingle.

The only time you might get a shock or KFF's, is if you in advertently short the contacts.

 

[vfr400]

Cheers folks. One thing I wondered is how long the (63v) capacitors hold their charge in the controller, because if that is holding enough of a charge, it stops it sparking anyway, right? At least, the 2nd time I connected (15-20 mins after the very first time) there wasn't a spark.

It depends on many factors. Sometimes there's a bleed resistor to ground to drain it off in a very short time for safety, as the prongs on the connector are effectively live.

After disconnecting the battery, put a screwdriver or anything metal across the pins on the controller side connector and you'll see another big spark as the capacitor discharges.

 

[Sturmey]

I am using an electrical 16 amp mcb for years to turn off the battery on a front wheel kit with no display. It has given no problems except they are a little large. These switches can typically momentarily carry 10,000 amps (rated breaking capacity). e.g. typical spec below. They also act as an additional fuse.

Miniature Circuit Breaker (MCB) Specifications | Entek Electric

Entek Electric provides a full range of miniature circuit breakers (MCBs) for domestic/residential installations.

www.entekelectric.com

 

[vfr400]

I am using an electrical 16 amp mcb for years to turn off the battery on a front wheel kit with no display. It has given no problems except they are a little large. These switches can typically momentarily carry 10,000 amps (rated breaking capacity). e.g. typical spec below. They also act as an additional fuse.

Miniature Circuit Breaker (MCB) Specifications | Entek Electric

Entek Electric provides a full range of miniature circuit breakers (MCBs) for domestic/residential installations.

www.entekelectric.com

I sometimes wonder about you guys. Why would you want a big bulky and expensive thing like that when you can just connect the connector. The little snap noise never hurt anyone. The only time you need a switch is when you have a removable battery that has delicate terminals, but then it costs nearly nothing to put a little waterproof toggle switch on the battery case to switch off any of the sense wires or the 12v supply to the mosfets, then the mosfets will switch off. That's how batteries with switches work.

 

[Manc44]

That Marley guy building them on eBay uses a switch but I don't know what it is he's using, it's only a small thing. Note the fuse on the switch wire too...



His listing doesn't show that image anymore but that's taken from a few weeks back, maybe he quit being silly vf400

I'm just not putting a switch on mine, it's too much pissing about plus I have never soldered anything in my life, maybe on work experience (with my dad wiring speaker cabinets up) nearly 30 years ago and then, some of those shorted out. It's just not my cuppa tea all this electronics stuff! I wouldn't dare touch a battery I just spent over £200 on.

My plan is to plug it in and never unplug it - because I never need to. Assuming these things are OK to be charged while the XT60 is still plugged into the controller? (say yes).

 

[Nealh]

The switch could be for the BMS as one cna buy them with switch output.

 

[vfr400]

That Marley guy building them on eBay uses a switch but I don't know what it is he's using, it's only a small thing. Note the fuse on the switch wire too...

View attachment 43639

His listing doesn't show that image anymore but that's taken from a few weeks back, maybe he quit being silly vf400

I'm just not putting a switch on mine, it's too much pissing about plus I have never soldered anything in my life, maybe on work experience (with my dad wiring speaker cabinets up) nearly 30 years ago and then, some of those shorted out. It's just not my cuppa tea all this electronics stuff! I wouldn't dare touch a battery I just spent over £200 on.

My plan is to plug it in and never unplug it - because I never need to. Assuming these things are OK to be charged while the XT60 is still plugged into the controller? (say yes).

That switch is on the BMS. It switches off the output mosfets, like I described above. The BMS is just a smart-switch. It looks at various inputs; like cell voltages, switch state, temperature; then decides whether to open or close the mosfets, which are just electronic switches. The BMS can be controlled by a CPU (smart BMS) or simple analogue logic, where the switch would be on the 12V supply to the mosfets.