SLA Battery or PMA system?

crash_davis

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Been on the forum for about a year; because of the incredible wealth of knowledge here I haven’t needed to post a question (until now) on my first restoration/modification of a motorcycle. What I’ve got is a 1981 XS650 with stock alternator and Boyer-bransden ignition set up for kick-only and all LED lighting. Pictures of the day I got it home in January, and today added. So here is my issue: I would like to clean up/minimize the battery and wiring on the bike for aesthetics and reliability.

Option 1: I can use a small sealed lead acid battery (12V 7AH) ~$40 with everything I have on the bike. My understanding from researching conflicting posts/threads is that the stock charging system should be able to handle the power draw when running above idle. And this should be enough to power the bike at idle and the stock charging system and reg/rec can safely charge the SLA Battery (but not Lithium battery).

Option 2: Install a PMA and small sealed lead acid battery (12V .08AH) or 4 cell antigravity battery. My understanding is the Moffset reg/rec can handle the low power draw of the LED lights but will be bleeding off a lot of energy the PMA puts out. And that a battery is much better than a capacitor for the Boyer bransden ignition.

I know there are a lot of pro-PMA and pro-stock viewpoints on the charging systems. I just want to be sure I understand these options correctly before making an uninformed purchase! Thanks!
 

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The only problem I know of the Boyer has i that it don't like Voltage outside specs
so option 2 does send up a red flag .
My first guess is that it will cause problems .
I would check that with Boyer that has a support .. But my first guess not possible

Option 1
Not sure that is a reliable solution either

minimize the battery .......... and reliability.

Since the success of a start up is dependent on power to the coils and alternator
might work but when the battery gets weak ..Problems are there .
Cant start it.
 
A 7AH battery should work just fine for no starter, LED's and stock alternator.
I like what you did with the bike btw.
thumbsup.gif
 
A 7AH battery should work just fine for no starter, LED's and stock alternator.
I like what you did with the bike btw. View attachment 198679
Thanks Jim, I’ve read through your many posts & replies on several topics and they have been most helpful to me in getting the bike together and running! I had seen your posts on electrical systems (and you :banghead: about some replies :)). I really appreciate your feedback, as I didn’t want to spend $$$ to create a new problem. I’ve been chasing problem after problem with this bike and it has been ‘fun’ and educational.
 
I don't think there's any hardtail bikes nominated for the calendar this year.... or damn few if there are.
I think your bike would be worthy of consideration.
Unfortunately, I'm out of nominations.
Anyone?
Bueller?


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RD twins had the same coils, points ignition, and a similar OEM alternator setup. And they worked just fine with a 5.5 Ah battery. So 7 should definitely work fine
I ended up going with a 5.5 Ah SLA battery and it’s been running just fine for the last 7 months. The bike has been a joy to ride!
 
I went thru the charging system on my '75 several years ago. I recall putting in an electronic voltage regulator / diode unit, and I think I was replacing an old 'mechanical' regulator. I definitely recall cleaning up the contact rings on the rotor, as well as replacing brushes and springs and cleaning up all contacts and slide points there-in as well. I went to one of those AGM alarm batteries, and just quit using the electric starter. I run an H-4 headlight with all original stock lighting. I think it has been over 7 or 8 years since that was all done, and its still working fine today. Same battery as well, which is probably now over 10 years old. But, my point is that the stock system ain't all that bad if its operating properly. I don't know that anything can be any 'more reliable' other than maybe an old magneto system, but even those had their issues. I like 'stock'! You always know where you are and what you're dealing with, plus you can almost always find a repair part pretty quickly, easily, and reasonably priced!
 
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