Battery cut-off switch? What to use...

[t0me]

Hiya, up till now I've been must pulling the deans plugs apart to isolate the battery when I'm charging or not using the bike.
Been looking for something easier/neater, and not having a lot of luck.
Got one of those big red key'd isolator switches, too big to mount anywhere easily.
What else can I use? What are you using? Any other suggestions? Ebay as the source would be easiest for me I reckon (in Australia).

Cheers,
Tom

 

[dnmun]

i use a DIP switch in the circuit current of the BMS so i can turn off the battery.

 

[steveo]

ev200 contactor is a good suggestion...

proper way to do it.. if you need on let me know

i have a couple floating around

-steveo

 

[teklektik]

Marine/Solar Breakers

Try a magnetic breaker for marine use (~ 65v/50A max) - similar solar units have higher V/A ratings (150v/100A+). The marine breakers are very rugged and have been mounted in the open and used in high humidity salt air for decades for similar double duty as protection/disconnect switches.

My bike is 64v nominal, 73v HOC, max draw ~60A. I use a 50A magnetic marine breaker for the main disconnect switch (Blue Sea #7230 - there are identical choices from other manufacturers). The 7230 is rated to carry 50A, trip at 62A, is good for 65VDC, and handles interruption currents up to 7500A at 65VDC - essentially indestructible for ebike use. Easy flush mount with a 3/4" hole. About $20 on Amazon.

Midnite Solar makes a unit of about the same size (approx 2" square and 3/4" thick) with stud terminals and higher available V/A ratings. I haven't tried these, but they look good. Flush mounting requires a rectangular cutout. Also about $20 on Amazon.

• 65v DC 6-32 SS screw terminal - marine = Blue Sea specs here: https://www.bluesea.com/products/category/14/29/Circuit_Breakers/A-Series?Actuator_Style=Toggle
• 150v DC 1/4" stud terminal - solar = Midnite Solar specs here: http://www.midnitesolar.com/productPhoto.php?product_ID=197&productCatName=Breakers&productCat_ID=16&sortOrder=12&act=p

Chances are you will not be switching anything other than a fraction of an Amp under normal circumstances, but these breakers have a very high carry current and interrupt capacity in a nice small package - a nice switch even if you don't need the protection feature. For protection purposes the current draw will be very high so there's no point in crowding the operating current unnecessarily. Something 50% over your max is perfectly fine and leaves room for a bigger controller in the future. These breakers are also rated for use as switches.

I've tripped the breaker due to controller failures as well as long heavy-handed steep-hill-climbing-episodes. The 50A breaker tripped at 60A+ as per spec but the two series 50A MAXI fuses in the battery packs never blew or even looked unhappy. The CA recorded 175A burst for the controller failures and the breaker still beat the fuses. As you can see, I got the highest rating marine breaker but ended up crowding the rating after some power upgrades to bike - the 50A breaker is okay but if doing it again I would go with an 80A unit.

I have mine mounted facing downward in the seat tube/seat stay area to keep out the bulk of the water. 7500mi and very reliable.

 

[t0me]

Excellent, just the sort of stuff I was hoping to see.

The "ignition" wire on a motor controller, that doesn't isolate the battery does it? I'll kick myself for over thinking it if adding a simple switch to that wire is the solution.

 

[rodgah]

the ignition wire on at least infinion controllers doesnt shut all of the power off, though the discharge is very minimal. AFAIK it just shuts off the logic side of the board while the power side is still live(this is maybe over simplified I am by far not a pro at knowing whats going on in controllers) so its still not good for long periods of no use.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=54225 is a board that is still being tested that basically works as a switch with pre-charge all built in.

 

[jonescg]

If you have a precharge resistor and momentary button in series, paralleled to the terminals of a switch, any suitably rated switch will work. I used to have a DPDT 250 V AC (30 V DC) switch on my 9 fet, 50 V ebike. Worked really well and took up very little space. You had to always press the button for 3 seconds before flicking the switch though. I'd put brief 100 amp currents through it without issues, but it wasn't the best.

 

[teklektik]

I'll kick myself for over thinking it if adding a simple switch to that wire is the solution.

What you should do is add a switch to that as a kill switch. It will make the controller go brain-dead for throttle or freak controller failures.

A must-have.

The current is very small so you can use light gauge wire - size it for adequate physical strength not electrical capacity. Ideally, it can be flicked with the thumb from the throttle-closed position (the first thing you try when the bike runs away and you are hanging on for dear life).

 

[teklektik]

My links to Outback Solar breakers showed the product no longer available when I posted above, but I located an exact equivalent unit from Midnite Solar and updated the earlier post. Higher ratings and stud terminals make the solar units look attractive for more aggressive builds.