Battery switch and fuse

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slomove
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Joined: 02/07/2009
Points: 16

Sorry about all my uninformed questions but that is as it comes up assembling the BL36 kit:

1.The controller power switch does not really turn off power as can be seen by the small cap charge spark when connecting the battery. I am wondering to put in a real battery disconnect switch (or equivalent relay). Is that a good idea or is the controller leakage current when turned off so small it does not matter?

2.Should I put a serious fuse (30 or 40 amps) in the supply circuit from the battery to the controller? If the controller should ever short out internally (FETs or caps) I would like to avoid damage to the cells or burning wire.

3.How do you guys protect the controller from rain? I installed it now on the rear side of the center stem right under the saddle which should provide some minimal "roof" protection. I would make a waterproof fabric hood for the whole thing but I suspect that would impede cooling air flow too much. Any good idea? Obviously I could slip a shopping bag over saddle and controller when parked but that would look really cheesy.

Thanks,

GB

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chas_stevenson
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Joined: 12/06/2006
Points: 1309
Re: Battery switch and fuse

slomove wrote:

I could slip a shopping bag over saddle and controller when parked but that would look really cheesy.

You may be right but I carry a shower cap to place over my seat because I would rather have a dry back side and not look like I had an accident. I think that would also help keep the rain off your controller as well.

Grandpa Chas S.

dogman
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Joined: 04/29/2008
Points: 830
Re: Battery switch and fuse

I carry some garbage bags for the inevitable, caught out event. You may want to just pedal without power in a real downpour, but a sack to cover my battery, controller etc will save a bunch of trouble later. I also put a soft foam rear fender on the bike. It's just a chunk of that cheap anti fatique mat foam, similar to backpack sleeping pad. It won't keep my back dry, but it allows a puddle to be ridden through without spraying the controller mounted on the seatpost. Looking cheezy when your bike is parked and thieves are scoping it out is a PLUS! You do need the ventilation while riding the bike though. Too bad controllers don't have fans, so you could mount in a waterproof, but ventilated container. In cool climates, if the controller heat sink is touching the frame, it might conduct enough heat to keep the controller cool enough. Another option is getting out the gutter sealant caulk, or butylene caulk and sealing everything completely. On my 2009 model controller, it's potted inside so that should help a lot if it ever gets wet.

I use the battery to controller plug to do disconnect when I need it, but mostly I leave it connected. I ride so often, I don't run the battery down. My bike ends up hooked to the charger about 20 hours a day. A fuse between the battery and the controller is a good idea. I'm and idiot for not having one. But since a lot of kits come without, maybe its not so essential. A short between motor wires is more likely actually, when the motor spins in the dropouts if you let the nuts get loose.

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slomove
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Joined: 02/07/2009
Points: 16
Re: Battery switch and fuse

Thanks for the advice!

I put the fuse in, found a nice weatherproof fuse holder at the auto store.

I will not install a separate switch. I measured the off-leakage current to be 8 mA @48V. That should drain the batteries less than 10% in a week. Not too bad and I will keep them on maintenance charge anyway.

Actually I did my first short ride tonight :) In the rain :(

GB

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