Witt78

Okay, so I'm new to this E-Bike scene... But am really enjoying it so far.

I made this video for some Facebook friends whom had never seen one before, so much of the information in it is useless for you guys. However, you can see what I've built.

https://www.youtube.com/watch?v=yqbTt_5fePI

I'm using a Diamondback Sorrento frame (2006 or 7, I think) 26"

Magic Pie rear motor with 4X, 12-Volt, 12 Amp Hour SLA batteries wired in series.
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Yes, I've had a couple minor problems, but have worked through them all.

My next paycheck I'm going to get a really beefy kickstand. Probably a twin leg, v shaped kickstand. (The original kickstand is useless on this bike now.)

My next paycheck I am also going to get a nice desulfator unit to install and leave on the battery.
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Now let me ask a question...

I want to put a "Kill Switch" on this thing. (That main power plug will eventually break if I keep using it.)

I was thinking about using a circuit breaker of some sort. How many amps should I get? I don't want the breaker to trip constantly, but I don't want to get one so strong it would never trip, even in the event of electrical trouble.

Suggestions?

- Witt

Zephyr Boy

I have a LiFePo4 48V/15Ah battery, I installed an on/off switch from Radio Shack. SPST 12VDC/50A On/Off Toggle Switch. I also went to my local Auto supply store, bought and installed an "inline fuse holder (12 AWG, 30 AMP fuse)."

Witt78

So the 12 VDC switches will handle the 48 VDC connection?

I figured you would weld the switch shut the first time you threw the toggle. =P

Sangesf

Why do you the "kill switch"?
The MP controller has auto shutdown built-in on shorts..
(my personal experience says it works fine).

Sangesf

Also, any inline fuse will work... From experience, I've never pulled more than 40a.
For a key lock/switch, I would go to your local golf cart place and ask them for a key lock.. I bought one for $25 at my local golf place.
(they use them on 48v golfcarts and they pull lots more amps then you will on your magic pie...)
IF you had the external controller model, you could have used it to set the alarm like I did?

Witt78

Okay, next question...

I just dropped a whole $4.50 on each of two LED bike headlights. (I bought two of em.)

I'm hoping that I can drill small holes in the battery covers and run that 5-Volt feed from the throttle switch, directly to the terminals inside the headlights... Am I going to have any sort of luck doing this? Or did I just waste $9?

(I thought it was a cool enough idea to try out...)

Sangesf

Do NOT hook them up to the throttle...
Throttle only varies voltage from ZERO to about 4.x volts.
Aren't they rated for 12v?

Witt78

Let me be more clear...

I have two feeds on that bike... Obviously, I have the 48 Volt Dynamo...

Then (According to this schematic in front of me) I also have a 5 Volt supply for the "Throttle and Pedelec". The schematic actually instructs you to use this feed for the lights.
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My question is this... I'm using regular battery powered bike headlights... They are supposed to run of 4X AAA batteries. I wonder if that's 4X AAA batteries in series? (4.8 Volts??) or perhaps in Parallel (1.2 volts with long life)

What would happen if I just ran a 5-volt feed into that light and soldered the wires directly to the battery leads?

Witt78

I'm looking at this schematic, BTW.

https://www.goldenmotor.com/e-Bike-DIY/MPguide.pdf

Witt78

I wish I did have a 12-volt feed. I'd go to the local junk yard and get the horn out of a 1989 Buick Century. lol It sounds like the fog horn on a cruise ship. hehe

Witt78

Here are the headlights we are talking about...

https://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWNX:IT

Cheap, Plastic, Chinese crap...

Sangesf

Those are rated at 6v.
4 x 1.5 is 6.
They will run on 5v but will not be as bright.
As for 12v, just get a 12v 7ah and hook up stuff to that.
All you need is a 12v charger.

Witt78

Well, these days AA and AAA batteries put out 1.2 volts. Not 1.5, so I should be slightly over-powering those lights. (Assuming those batteries are in series and not parallel.) Plus, I want to install two of them, if I can get this working properly.

I have tossed around the idea of putting one more 12 volt battery on the bike, but I don't want to add any more weight unless I have to.

Somebody mentioned that I could go to a golf cart shop and get a cheap DC to DC Converter box. 48 Volt to 12 Volt, step down. I'll be looking into that. If I can get a converter that weights half a pound, instead of a battery that weights 5; that sounds like the better choice.

Witt78

BTW, all of this is also assuming that my 5V lead won't sag to half a volt every time I hit the throttle.

The damn schematic says it's a "5V Supply" but it appears to run through my throttle. We'll soon see. The headlights should be here in the next day or so.

Sangesf

Rechargables are 1.2
Alkalines are 1.5

Witt78

Really... That's interesting.

I wonder how they get away with that? You'd think it would cause problems in certain electronics.
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Won't be long and I'll figure out if this is going to be a viable option. The headlights are pretty much due to arrive.

I just found a bunch of DC/DC Step Down converters on eBay too, so if plan A doesn't work, I have other options.

adamtki

Great to see another e-bike enthusiast. Just curious, how heavy is the bike?