Topic: Help! Noob with battery problems...

[shane]

So I bought my bike about 2 months ago. Battery was nearly dead when I bought it. So then I bought a new battery a month ago from a honda shop down the street. Been riding just a couple miles a day 3 or 4 times a week. Just short little rides, getting used to the bike, working out issues. It has  started up every time no problems. Then friday, I swap out the rear suspension, then try to take it out for a ride that night. Battery dies in the driveway. So saturday I take the battery back to Honda ask them if they can test it or replace it. They put it on a charger for 2 hours and tell me its completely dead. So they replace it.

Anyway, so before I put this battery in I wanted to make sure there's not a constant draw coming from somewhere by using a test light. I think I did this right, someone please correct me if not. I connected the postitive cable to the postive terminal, then put the clip of the test light on negative terminal, then touched the tip of the test light to the negative cable. There was no light. So assuming I did the test right, there's not a constant draw.

You think the alternator is probably the culprit?

[Stev-o]

First off, don't know what kind of bike you have so more details would help.
Second, most SOHC Hondas do not have alternaters, so doubt that is the issue.
If your battery is not charging, it could be as easy as a bad connection or a bad regulator or stator.

Good luck...

[shane]

Oh yeah, its a '76 550 Super Sport (just noticed you have one as well)...

No alternator

[Spanner 1]

Yeah alternator!.....first tell-all test is to put a volt meter across the battery with the bike running.... rev the motor to 3k, 4k, 5k and the voltage must rise to ,say, 14.5V.... if not then alt. / reg. problem.......

Your bike is not charging.... having re-read your first post.

[TwoTired]

First off, I will confirm the 550 does indeed have an alternator.

Second, these bikes were made to run and not just idle.  The alternator needs RPM to make enough power to overcome system load, where the excess power created can charge the battery.  The battery will deplete at idle with the lights on, that's normal.

There are a number of things that can go wrong.  And, the first thing to check is the battery voltage  Fully charged at rest, then again with the key on,  then measure the battery voltage at idle, 2000, 3000, 4000, and 5000 RPM.  (The alternator is rated for max power @ 5000 RPM; 150 watts.)  The alternator makes about 40-50 Watts at idle RPM and the bike uses about 120 Watts when the key switch and lighting is on.

Anyway, the above measurements will tell if the charging system is working and at what RPM the battery voltage begins to rise instead of fall.

Once you learn the charging characteristics, you can then move on to possible improvements, like maybe electrical contact cleaning.

You should also note that the alternator power capability works well with the stock electrical loads.  Higher wattage headlights or alternate ignition devices can consume enough power that the stock alternator can never keep up with demand, resulting in a depleting battery that will eventually lose all that was stored.