Tecumseh Charging Help

Ruppster81

Ruppster81

Member
#1
#1
I want to "MAYBE" add electric start on my super bronc, or at least so I can add a battery for more consistant light power and accessories. According to some online tecumseh manuals I have a 3 AMP AC lighting coil, but I need a diode or 2? to convert to DC to charge a battery, what kind of diode(s)? Can it be obtained from radio shack? The book also said this system does not use regulator as the output is not enough to need one but it also said something about if your battery does happen to boil/overcharge I need to go to a half wave rectifier? My wires comming from the motor are 2 + leads and the kill lead.

All this has my head spinning like a top and I've never worked on a tecumseh that had to charge a battery. Any help is apprciated.
 
Ruppster81

Ruppster81

Member
#3
#3
Thanks cncsparky, Now How would I wire them from the alternator? I have 2 hot leads and the engine kill. Do I use 1 or both power leads? Once I get this figured out the rest "should" be easy. I'm going to radio shack tomorrow and see if they have those diodes in stock.
 
cncsparky

cncsparky

New Member
#4
#4
Diode bridge - Wikipedia, the free encyclopedia

You'll use both hot leads, one on each side of the bridge. The striped end of the diode is the Cathode. In the picture on the wiki page, the two cathodes tied together make the + side and the two anodes connected make the - side of your DC circuit.

This would actually be easier to connect, I should've suggested it first:

25A, 50V Full-Wave Bridge Rectifiers - RadioShack.com

It should be marked to make hookup easier, along with spade connectors.

Tom.
 
Ruppster81

Ruppster81

Member
#5
#5
So my engine has 2 + AC output wires and when the diodes or rectifier is used I will have 2 DC conectors with one being + and the other being - ?

I thought I was supposed to end up with one wire to hook up to the battery? Sorry if I am way off base.
 
cncsparky

cncsparky

New Member
#6
#6
The rectifier will only get you raw DC voltage. I'm not sure if thats good enough to just connect to the battery or not. We may need an automotive regulator for charging the battery.

Tom.
 
Ruppster81

Ruppster81

Member
#7
#7
The manual said the 3 amp AC system when converted to DC didn't need a regulator unless the voltage went above 14.4 volts at 3600 rpms.

Now that I think about it my engine is spinning almost twice that and maybe putting out 20 volts + at full throttle so maybe a regulator will be needed, I'll have to check the voltage when I get it converted. I still havent made it to radio shack yet to get those diodes or rectifier.
 
Ruppster81

Ruppster81

Member
#8
#8
Ok, I got the 4 diodes from radio shack. I tried a single diode inline with 1 AC positive lead from the engine and I lost 2 volts converting from AC to DC, That's fine I suppose.

Then I tried hooking both AC positive leads from the engine with 1 diode and lost another volt or 2. WTH? it's worse with 2 power leads than one? Shouldn't it have doubled?
 
cncsparky

cncsparky

New Member
#9
#9
Sounds normal. I'll try to explain it.

Without the diodes, measure the AC output across both hot wires with your volt meter. Lets say you measure 12V AC. Imagine a sine wave with a zero volt line running horizontally through the middle of the sine wave. The meter is measuring 6V above and 6V below the zero line for 12V total.

When you inserted the diode inline with one of the hot wires, you effectively took out everything below the zero line, so only 6v available. When you rectify the AC, it takes approximately .6V to turn on the diode, which raises the Zero point. Its not straight DC either, because you haven't smoothed the output yet which may not be necessary in your application.
 
Ruppster81

Ruppster81

Member
#10
#10
I did ALOT of research and thanks to a few OldMiniBikes members I have found out that the super bronc had this on it



And here is the wiring diagram for it. So it looks like this is how I should do it? It makes sense to me lol. I think I understand the loopy wave diagrams with the line in the middle. It basically cuts your volts in half when converting to DC correct? It makes sense now that I was trying to use both AC leads to 1 diode... I dunno what I was thinking.

 
Last edited:
Ruppster81

Ruppster81

Member
#13
#13
Thanks Randy, got the pics. Mine did not have electric start but have most of the parts to convert it. I guess I don't need half of the wiring in the diagram I posted. I still don't know how they get away with no starter solenoid but it must work.

Most of the parts I collected were from an old ariens rear engine mower motor including the starter, ignition, I had a to get a new flywheel as mine didn't have the ring gear, It was cheap $20 for new. All I need now is a battery box.





 
Last edited:
Randy

Randy

#14
#14
The box should be the easy part. Let me know if you need measurements and better photos. It might take me a few days to get them too you. Switches are rated for what ever amperage so apparently the starter must not exceed that? The switch dose look to be heavy duty, just judging by the size of it.

Randy
 
Ruppster81

Ruppster81

Member
#16
#16
I know I've seen some of the OLD mowers that never used a starter solenoid, Any super bronc with the factory electric start I've ever seen never had the solenoid unless it was added, That had me puzzled :confused:

I wired it up without the solenoid and used the heavy duty key switch.... It works, really good actually :thumbsup: The switch or wires don't get hot but I used alittle heavier wire than the broncs originally came with. Also made my battery tray and it turned out really nice, It will work untill I can find an original but I don't see changing it out anytime soon. If I had a sheet metal brake I could make one to spec's but I don't have access to one. So far it's good and I'm happy with it.

Thank's guys for all the pictures and help! :scooter:
 
Randy

Randy

#17
#17
LOL.. I see your no longer beating a dead horse. I was surprised at the small gauge wiring as well. But it's "heald" up for 35 years.................
Randy:scooter:
 
Ruppster81

Ruppster81

Member
#18
#18
Yup! It was time to change it after about 2 years lol. Just doing some upgrading to the avatar and added a video link for the Bronc in my sig. I just figured since I was "testing" without a solenoid it would be best to do it with a little heavier wire. It's going to stay this way untill something gives out but nothing seems to be under any stress and looks like it should hold up for 35 years or better :thumbsup: Also will be adding a pic later... I still have to paint the battery box.
 
Larry Harter

Larry Harter

New Member
#20
#20
Ruppster, On some of the Tecumseh models they had a 3 Amp D.C. and 5 Amp A.C. alternator. The 3 Amp D.C. is used to charge battery and a 5 Amp A.C. for lighting. The red wire has a diode for DC, The yellow wire provides A.C.
 
You must log in or register to reply here.
Top