How small is too small of a battery

[Tiny92]

was reading through the tech section and came across this http://www.xs650.com/forum/showpost.php?p=4063&postcount=1 section 2 says the bikes ignition runs off the battery and a weak or compromised battery will cause a whole host of issues. I've also read about people going kick only with small battery's without issue. Will I have trouble running my 80 xs650 with a smaller battery. say a UPS battery backup?

I know its not much smaller in size but the brand new ballistic 4 cell battery I bought is dead and this battery was a free bee from a buddy. Electronic are all going in a fork bag hooked under the seat so not a lot of extra space.

 

[osteoderm]

With a PMA and kick-only, battery size is almost irrelevant. Everything depends on the strength/configuration of your charging system and the loads you want to run.

 

[Tiny92]

Devils in the details... Headlight and tailight only no blinkers. Has the high beam though I wouldn't mind not using it if it impacts the running of the bike. Stock charging system though it seems strong. haven't put a volt meter too it prior to tearing into the bike.

 

[osteoderm]

In a strange and wonderful way, the stock charging system is powered by the battery. Yup, you read that right... Low/weak/undersized/flat battery, and the alternator will not charge. Even a strong charging system may not keep the battery up at idle... It's a downward spiral where a tiny battery is just grief waiting to happen.

That's the primary advantage of a PMA: the charging system still run when the battery is low/flat/non-existent.

 

[Tiny92]

Downside I wasn't really looking to swap out the alt and ignition system at this time...

 

[aaronrkelly]

Yeah.....stock charging system and a non-standard/way small battery.....I see alot of pushing your bike in your future....but I really doubt itd run right at all honestly.

 

[pamcopete]

Use of a small battery with either the stock system or a PMA requires a lot of battery management to keep it from discharging below 10.5 Volts. Both charging systems will provide too much current for a discharged small battery and boil / fry it . Habits like turning off the headlight at stop lights and trickle charging overnight, every night, will help prolong the small batteries life.

Even if you remember to turn off the headlight at stop lights, it's equally important to turn it back on before you rev the engine else the current that would go to the headlight goes to the battery instead (fry, fry, fry ) One trick is to install a relay that shuts off the headlight when you shift into neutral at the light. The relay operates from the ground provided by the neutral switch.

 

[Tiny92]

Okay this should be it on this question was just reading up more on small battery setups and my setup isn't that small as it turns out. My battery is 12v 7ah not 12v .7ah should this be okay for normal riding, maybe add the relay for the neutral headlight cut off?

I'll also look at swapping out the tail/brake light with an LED bulb.

The battery I'm using is from a computer server battery backup system. I was planning on using a solar panel I have kicking around to make a garage window mounted battery tender for my winter storage shouldn't be that big a deal to add connecting it after riding to part of my routine if thats what is needed.

 

[Tiny92]

Update:

Been running my curent setup for a few miles now. Currently no issues aside from one time the Highbeam got flipped on during the day without my knowing it. a bit of in town riding and had it stall out at a light. noticed the Highbeam was on and ran fine from that point forward.

Going to disconnect the wire to the highbeam in the headlight bucket. I never use my highbeam normally and this will effectivly give me a on off switch for my head light for if I get stuck idleing at a light for any length of time.

Recap this is the battery I run in my bike UPS Battery

 

[Gene]

Update:

Been running my curent setup for a few miles now. Currently no issues aside from one time the Highbeam got flipped on during the day without my knowing it. a bit of in town riding and had it stall out at a light. noticed the Highbeam was on and ran fine from that point forward.

Going to disconnect the wire to the highbeam in the headlight bucket. I never use my highbeam normally and this will effectivly give me a on off switch for my head light for if I get stuck idleing at a light for any length of time.

Recap this is the battery I run in my bike UPS
Battery

Good follow up. I just built my electrical box with the same battery as you. I have yet to really ride my bike otherthan around my parking lot. So far its been fine in my bike and starts up evey time (kick)

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