Author Topic: 1971 Honda CB500 - Charging Issue (At wits' end) (Read 14509 times)

scottly · « **Reply #50 on:** July 13, 2016, 10:56:26 AM »

What are you going to do with the old battery? Can I have it?

zerodaydave · « **Reply #51 on:** July 13, 2016, 12:41:40 PM »

Ha if it isnt a bad battery the old one is going in a KZ400.

scottly · « **Reply #52 on:** July 13, 2016, 06:04:14 PM »

Ahh, shucks.

Seriously, when I got my LiFe 4 cell battery 5 years ago, the first thing I did was conduct bench testing, recording both the charge and discharge characteristics. Based on those tests, it would require an average charging current of 5 Amps for 50 minutes to raise the voltage of your 8 cell from 13V to 14V. Even if your charging system was working properly, it didn't have enough time to recharge the battery, and the "tender" may not be up to the task.
If you want, ship me the battery and I'll do a proper charge and load test for free, but you will have to pay for the round trip.

zerodaydave · « **Reply #53 on:** July 14, 2016, 06:29:52 PM »

So I charged the battery over night and it was at 13.20v.

I tested the bike again and here is what I got:

Terminal 13.20v

Idle (1k) 12.92

2k 13.8v

3k 13.14v

5k 13.14v

So it's all in spec according to the manual except for 3k - 5k should be 14.5k?

I rode the bike to work and back today in stop and go traffic about 20m each way and let the bike sit.

I tested it again and it was at 13.19v.

Sorry for the noob question but do I have an issue? It's charging a little bit right? Is it just weak? Or is it good.

scottly · « **Reply #54 on:** July 14, 2016, 06:55:40 PM »

Sounds like you need to leave the tender on for longer; last time it got the battery up to 12.89V, and this time it got the battery up to 13.20. Your charging system must be doing something, since you ended up with nearly the same voltage you started with. The 13.8V at 2K dropping to 13.14 at 3K and above is troubling though.

zerodaydave · « **Reply #55 on:** July 14, 2016, 07:04:07 PM »

I just got the new battery from and tested it out of the box it's at 13.2v at the terminal.

I threw it in and I have the same results I can't beak past the 13.15v in the 3k - 5k range.

scottly · « **Reply #56 on:** July 14, 2016, 07:29:51 PM »

Place your red voltmeter lead directly on the battery + terminal. Connect the black meter lead to the white wire going to the Ricks regulator. Turn the key on and check the voltage. Report the results.

zerodaydave · « **Reply #57 on:** July 14, 2016, 08:05:51 PM »

There's no white wire. I think it's green as that's the only wire that test would work on. At 3k it was 13.7v reporting with + on the terminal and negative on the green.

scottly · « **Reply #58 on:** July 14, 2016, 08:20:24 PM »

If you got 13.7 volts on a green wire, but only 13.14 at the battery, it suggests a bad ground connection between the battery- and the frame. Test the voltage from the battery- terminal to the green wire where you measured 13.7.

zerodaydave · « **Reply #59 on:** July 14, 2016, 08:25:55 PM »

So positive on the green wire and negative on the negative terminal correct?

scottly · « **Reply #60 on:** July 14, 2016, 08:29:07 PM »

Yeah. And if there is no white wire on the reg, what is connected to the white field coil wire?

zerodaydave · « **Reply #61 on:** July 14, 2016, 08:46:16 PM »

Ok ...

See attached picture of the connector from the stator and field coil. There is a white wire that goes to a white wire from the field cool shown in the pic attached and on the other side that white wire goes into the back of the rectifier/regulator. There is no voltage on that white wire when I tested + to the + terminal and - to the white wire.

zerodaydave · « **Reply #62 on:** July 14, 2016, 08:58:49 PM »

More pictures

scottly · « **Reply #63 on:** July 14, 2016, 09:16:47 PM »

Quote from: zerodaydave on July 14, 2016, 08:46:16 PM

There is no voltage on that white wire when I tested + to the + terminal and - to the white wire.

I would have expected 1 volt, more or less. With the meter black lead connected to battery -, and the red meter lead connected to the white field wire, what is the voltage with the key on?

zerodaydave · « **Reply #64 on:** July 14, 2016, 09:29:07 PM »

Just at idle (1k) it's 11.50v from the field coil wire.

scottly · « **Reply #65 on:** July 14, 2016, 09:39:51 PM »

Ok, now measure the voltage from the battery- to the green field coil wire, as close as you can get to where it exits from under the cover. Key on, but the motor doesn't need to be running.

zerodaydave · « **Reply #66 on:** July 14, 2016, 09:50:10 PM »

It's like .90v with just the key running. Sound right?

scottly · « **Reply #67 on:** July 14, 2016, 10:01:58 PM »

Should be zero, or very, very close to zero. You have a poor connection between the battery-, frame, and harness grounds. That .9 volt loss plus the 13.2 volts measured earlier would bring the charging voltage up to 14.1 volts.

zerodaydave · « **Reply #68 on:** July 14, 2016, 10:07:27 PM »

So basically just go around the bike and look at all the grounds and make sure theyre clean. Sorry I'm learning as I go. Not really sure how to troubleshoot that other than make sure they are clean.

scottly · « **Reply #69 on:** July 14, 2016, 10:21:07 PM »

No problem, as long as you are learning!

Since your wiring isn't stock, and I'm not looking at it with my own eyes, I can only give you some things to look for. Normally, there is a connection from the common green harness wire to the frame, sometimes at the coil mount under the gas tank, sometimes near the battery under the seat. You need to find this connection and make sure it's clean and properly grounded. The battery - post must also have a good connection to the frame.

zerodaydave · « **Reply #70 on:** July 14, 2016, 11:02:50 PM »

I have found it and it's connected on to the coil with the two bar end lights (which flicker at idle and when revving). I looked at the connections and it is clean. Do I need to do something special with the green wire? Can it have other accessories grounded with it?

Also it's crazy how much I've learned and how much I continue to learn from people like you and cal on this forum. Super stoked!

scottly · « **Reply #71 on:** July 14, 2016, 11:19:55 PM »

Yes, you can have other accessories grounded at the same point, but if the bar end lights are flickering, it may point to a poor/loose ground connection. Remove the bolt and make sure the connection point on the frame is clean and shiny, and all surfaces on the wiring eyelets are clean as well. When reassembling the connection, make sure the bolt clamps the eyelets firmly against the frame; a bolt that is too long will feel tight, but not clamp the eyelets properly.

zerodaydave · « **Reply #72 on:** July 14, 2016, 11:33:34 PM »

Excuse my ignorance but it can be any of the grounds right? There's nothing significant about the main green one?

zerodaydave · « **Reply #73 on:** July 15, 2016, 10:12:52 AM »

Plot twist discovered this this morning. See attached. The bike was still running because we were apparently bypassing the fuse wired directly to the battery. We removed that wire and we are now going through the fuse.

I went through all the grounds and sanded each ground down to the shiney frame.

Test results are about the same. It is just crazy how fast the battery drains when idling I barely have time to test anything before it dies. The new battery is already at 12.3v. I had to place the old one back in. At terminal 13.20. At 4-5k 13.60v. Should it be at 14.5k in those ranges? That's what the manual says.

New test results attached. Did break out of the 13.15v range I couldn't get out of yesterday.

I'm super frustrated right now. I have no idea what it could be.

zerodaydave · « **Reply #74 on:** July 15, 2016, 02:44:04 PM »

Ugh ... So I found it! And I now know what's up. Basically I was doing a compression test for another issue I was having. And when I tried to start the bike for some reason the ignition button wasn't working so I kick started the bike and drove it around the neighborhood. Came back and tested it again and this time 14.64v at 5k rpm! Turned off the bike and was super stoked! Obviously I didn't believe it so I tried to start the bike again with the starter button and it didn't work. Kick started it and only 13.50v at 5krpm what gives? Hit the ignition button again and the bike just cuts out. Turned the key off and kick started it and again 14.64v at 5k rpm. So it's something with the right hand controls! Specifically the ignition starter button. Grrr ....

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Author Topic: 1971 Honda CB500 - Charging Issue (At wits' end) (Read 14509 times)