Battery too big for 1954 generator

Electrical issues
Forum rules
Please do not start new topics here, but here: New Panhead and Flathead topics
Post Reply

Battery too big for 1954 generator


Post by Danl » Mon Apr 07, 2008 9:43 pm

Post by Danl on Jun 27, 2004, 6:05pm

Okay guys, here goes... I've got a '54 motor/tranny, but I'm running in a late swingarm with the large Shovel battery. The bike was puttin' around just fine yesterday (no headlight), then me 'n my gal went out for a putt last night and it started running like crap at higher revs.
I've been told that the ol' generator is not cranking out enough to deal with charging up that big battery AND run the headlight, if the battery is even just a little bit low. Yes? If so, what can I do (with what I've got)?


Post by Jack Hester on Jun 27, 2004, 10:13pm

Danl -

I used to have a 65 Pan, that had the large battery, as it was a stock bike. In N. Carolina, we have to run the headlight all the time. Never a problem out of the 12v generator on this bike. Put quite a few miles on it before I sold it to a guy in England.


Post by kell on Jun 27, 2004, 10:57pm

You could put a smaller battery in it (a healthy one) and see if the problem goes away.
I kind of doubt it will be that simple.

Post by Danl on Jun 27, 2004, 11:10pm

Thanks, guys... yeah, I put a new battery in it this Spring, as the old one was dead, and wouldn't hold a charge. I had a couple other problems (grounding out at the contact post, thru the dist base... insulator blocks were worn) and so, after I tracked down those gremlins, I got the new battery. Running w/the headlights on is the only correlative to this crapping out, I can figure right now.

Jack... do you know if these generators (early w/no electric start, and the later models w/electric start) put out the same amount of juice?

Thanks again.


Post by Squint on Jun 29, 2004, 6:50am

I have built seveal pan bikes 48,56,and a 59 They all had 6 volt generators but your large shovel battery will be a 12 volt. Since you dont mention using a 1965 or later generator I reckon I should remind you everything pre 1965 would be 6 volt ,and your generator is only puting half the volts into the 12 volt battery that it needs.
This sounds like something I woulda overlooked myself, obvious as it seems .What you described is exactly what would happen if you did have a 6v gen.with 12v batt. Yer coil uses so little juice ,and the brake lite is hardly on .without the headlite you could ride that bike like it is forever. Of coarse the law wont let you.
Hope this helps..

Post by Squint on Jun 29, 2004, 7:12am

Hey Danl I just read yer last post asking if the if the 2 generators put out the same amount of juice ABSOLUTLEY NOT in 1965 Harley went to a 12 volt generator before that they used a 6 volt generator same with the batterys before 1965 it was 6 volt in 1965 and ever since they used 12 volt .
thats yer problem..All you gotta do is charge yer battery and ride over to any battery testing place and ask em to check your generator output , also all 12 volt generators are stamped 12v following the model number .
So what voltage are the light bulbs ..You better go back to 6 volt for all of them..I dont think you can half charge yer 12 volt battery and run it on a 6 volt system but if it were me back then I would sure as H*** try it ,( I never had enough money for needless things ) just be sure you got jumper cables along .
Thats very lokely the problem ..Good Luck

Post by Danl on Jun 29, 2004, 1:59pm

Hey Squint! Thanks for the head's up... I'm not sure that's it tho...? I've been running this bike for about 7 years, and just had the motor and tranny rebuilt (I'm in the de-bugging stage right now). BUT, I did have the generator rebuilt while I was at it!?! Told the guy it was from a '54...!? Maybe he was a little too efficient.
I've got the battery charged up, but (as you can tell) electrical isn't my biggest blessing. Do I just hook up the volt meter to the two gen posts? Is it really as simple as that? Don't tell me this ol' dude (me) has overlooked something as simple as that!! Gawd, I'm gettin' old...


Post by billy on Jun 29, 2004, 6:29pm

Squint makes sense.
If you took it to a rebuilder & stated, for my '54 & made no mention you converted it to 12 V. I would think he's gonna make it right for a '54 = 6V...
The only Harley that had 12 volt in before '65 was the Servi-Car, First HD Electric start in '64 & first 12 V. HD.

just my 4 cents........

Post by Sidecar on Jun 29, 2004, 7:06pm

The "big" battery is not your problem. {Unless of course, there is something wrong with it}. I think you got some bad advice about the genny charging the "big" battery and running the headlight at the same time also. {Unless of course, there is something wrong with it}
Take your volt meter and stick it on the battery {observe proper polarity of course} and make sure you are getting a 12 volt reading. Start the bike up. Open the throttle a little to get the revs going at a continuous rate. The meter should be reading higher than 12 volts now. {Are you seeing 13 volts or so now ??} Turn the headlight on. What is the meter reading with the headlight on ?? {You can let go of the throttle after you make a note of the voltage while the headlight is on.}
Let us know what happens.

Post by squint on Jun 30, 2004, 7:18am

Danl ,just take yer volt meter and put one of the 2 wires on one of the battery posts and the other wire on the other battery post hope yer volt meters got only 2 wires ..any way start the bike and see what it says . If it shows minus you got the wires reversed,no big deal just switch wires around so they are now on the oposite posts from what you just had em on, now read it .thats how many volts yer gen is putting out ..Dont hook it to the generator ..
Now as for the guy who rebuilt the eng and gen .wa 1954 eng and gen ..any one wjho knows how to rebuild an old pan will know 1954s came 6 volt ..From what you say I'm certain you have a 12 volt ( has to be if from a shovel ) battery and if you had a 1954 generator rebuilt ,the guy will know they came 6 volt and see it was 6 volt way would anyone change it to 12 volt and not tell you ..Noe Danl check ALL yer light bulbs and headlight too..make sure you got all 6 volt ( after confirming you have 6 volt) ..All you got to do is get a 6 volt battery .If you are running your lights all the time I dont think your gen will keep up may want to charge the battery ( 6 volt) every few days ..I never ran with my lights on ..Still dont on my 91 springer ,unless i'm in rush hour traffic ( to many idiots ) .Mine didnt stay charged when I had to leave the lights on like when I was in US and didnt want to get pulled over in unfamiliar territory. I;m in Canada . Another thing a friend of mine does is use a rehostat ( like a house dimmer switch you turn and the lights dim)
He hooked it to the wires going to his headlight and it appears to be on ,just a bit dim But he is saving on electricity ..and still has a headlight on ,although kinda dim..
Let us know how you make out ..

Post Reply

Return to “Electrical”