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Early AGM battery demise

teebo

Veteran Member
Joined
Dec 5, 2021
Total Posts
1,786
Total likes
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Location
Oklahoma City
What could cause early AGM failure? Less than a year old. I can literally watch the voltage drop. Interesting part is that moving the battery around changes the reading. My battery tender also keeps cycling oddly when connected.

It has been hot here. Routinely over 100. Often closer to 105. No telling about heat build up in the garage.

1969 CB350
 
What could cause early AGM failure? Less than a year old. I can literally watch the voltage drop. Interesting part is that moving the battery around changes the reading. My battery tender also keeps cycling oddly when connected.

It has been hot here. Routinely over 100. Often closer to 105. No telling about heat build up in the garage.

1969 CB350

Are you running the original rectifier and separate regultor setup?
 
New rectifier.

1969 CB350
You installed the new unit at the outset before you installed the AGM battery? If not maybe the voltage of the original setup had already started damaging the battery. I just changed out my original to the new combo unit just for that reason, to save the AGM from the ~16 volt charge. What brand battery is it?
 
New style rectifier/regulator from the start.

Trying the repair mode on my battery tender. I don't expect success.

1969 CB350
 
Is the RR a cheap Chinese model? I've had brand new ones last less than 50 miles and overcharge and cook the battery.

Hook up a voltmeter to your battery with the bike running and see what voltage you get at 5k rpm.

I've also had issues with bikemaster platinum batteries, and no issues with cheap ebay batteries.
 
Not sure how to determine if it's Chinese.

The battery is a Bikemaster platinum.

This is why I need a spare motorcycle. I'm going to get on this. I mean if I'm good for one, I need at least one (two?) more.

1969 CB350
 
Is the RR a cheap Chinese model? I've had brand new ones last less than 50 miles and overcharge and cook the battery.

Hook up a voltmeter to your battery with the bike running and see what voltage you get at 5k rpm.

I've also had issues with bikemaster platinum batteries, and no issues with cheap ebay batteries.

Just asking...is there a non Chinese made unit that you know of that has a good reputation? And how would you know if a Chinese made unit is a good or sketchy one?
 
Not sure how to determine if it's Chinese.

The battery is a Bikemaster platinum.

This is why I need a spare motorcycle. I'm going to get on this. I mean if I'm good for one, I need at least one (two?) more.

1969 CB350

I found your problem. You purchased the semi cheap Bikemaster platinum, big mistake. You should have purchased the ultra cheap Mighty Max mentioned by me and ballbearian.
 
I've had good experiences with eBay Mighty max batteries.

As for RR, I've had luck with ricks and Charlie's place. I've also used 80s/90s/2000s made in Japan 3 phase units on my 350.

Anything except generic eBay or online shops that source generic parts... I'm not sure the story behind ricks but if anyone has heard different then I'd be curious


I found your problem. You purchased the semi cheap Bikemaster platinum, big mistake. You should have purchased the ultra cheap Mighty Max mentioned by me and ballbearian.
 
I have something else going on.

I noticed the neutral indicator light fluctuating. Sometimes just sitting there.

Removed the motorcycle battery and jumpered bike up to truck battery. Intermittently it will operate the starter motor. Other times it does nothing (not even lights do anything), and other times the neutral indicator is dimming or cutting out.

Like a short somewhere. But the fuse isn't blowing. Yes... Correct size fuse.

1969 CB350
 
Try wiggling the key switch plug... that's where I've had most problems.

Make sure your ground contact is clean and not corroded, and good contact with the frame.

After that, wiggle the harness and check for any extreme bends(like from battery to solenoid) or pinched wires or stressed connections.

However, the battery voltage on a charger should be separate from all those issues. .
 
I thought at first wiggling did have an effect. Not entirely sure now.

This probably explain a situation I had not long ago where I started the bike, running fine, and it just shut off. Checked the fuse (it was fine) and it started back up.

1969 CB350
 
If the ignition switch is still the one on the bike when you got it (possibly the original, or at least an old replacement) then it could easily have corroded contacts internally. The older switches can be disassembled and contacts cleaned/greased, there are little tabs in the outer metal shell on the back of it that you can bend open to get the board out of it.
 
I've had a few SS (stupid stuff) issues lately. Mostly due to not using dielectric grease on switches a few years ago, now EVERY thing gets it, ground straps, rectifier mounts, switch contacts, bulb bases and sockets. A poorly grounded rectifier can get cooked then it damages battery.
 
Vintage bikes are never done, are they?

1969 CB350

Typically, no. :) When I had my string of new ones during high school and while working for the dealerships, I rarely had to touch them but there was always regular maintenance anyway... and it was during the era of carburetors and points ignition on cars and trucks too, so we didn't give it a second thought - stuff needed to be done back then at certain intervals no matter, unlike today when you just put gas in it, check the oil once in a while and go. No one even mentions tune-ups anymore because even spark plugs last ridiculous lengths of time.
 
I did replace the battery. I got it to hold a charge. It just wouldn't crank the starter.

New Mighty Max and started right up.

I did rev it to 5k. It didn't go above 12.8. What should it be?

I also cleaned the switch. Wasn't corroded. There was a thick blob of some goo on one side. Old grease.

1969 CB350
 
I did rev it to 5k. It didn't go above 12.8. What should it be?

Remember that unlike a car charging system with 100 amps available, the battery voltage won't rise as quickly with a weenie charging system feeding it so a quick rev to 5000 probably won't show much change. Riding down the road above 4000 to 5000 for a few minutes will elevate the battery voltage to where the cutoff point would be for the rec/reg unit you bought, hopefully more than 13.5 but no more than 14.5v. So, sustained charging with small output will take longer to show its maximum.
 
The battery that read 12.8, what was the resting voltage and what was the voltage at idle?

If resting voltage was 13v and voltage at idle 12.8, then 12.8 at 5k rpm means your stator, generator magnet, or RR or the wires connecting them need further inspection
 
AD said what I was going to. If you hold it at 5k for 5 seconds you will see the voltage creeping up slowly. Mine started out at 12.8 and I saw 13.25 after a few sustained 5k revs.
 
Remember that unlike a car charging system with 100 amps available, the battery voltage won't rise as quickly with a weenie charging system feeding it so a quick rev to 5000 probably won't show much change. Riding down the road above 4000 to 5000 for a few minutes will elevate the battery voltage to where the cutoff point would be for the rec/reg unit you bought, hopefully more than 13.5 but no more than 14.5v. So, sustained charging with small output will take longer to show its maximum.
This sounds like a great excuse to go for a ride. Not that I need much of one.

1969 CB350
 
I've forced a done battery to spec volts but it's the amp draw that a new one has that cranks a starter. If you took the old one to be tested with a pile load tester, it would fail.
 
Took it on a highway ride. Checked voltage in garage revving to 5k.

13.35 when I first got home. 12.88 after using the starter. Then 15-20 seconds at 5k seemed to stabilize at 13.53. It likely would have gone up a bit more. Not quickly though.

1969 CB350
 
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