Topic: Battery at 5.5V after long ride (melted alternator connection)

[zabzob]

Bike is a CB750K5.

I started another thread about slow cranking from the starter, thinking that the issues were starter related. Now it seems it is charging related.

I did a 50 mile ride yesterday. Lots of highway stuff. Last night, close to home, the bike feels like it want to die. I pull up in front of my place and start backing the bike in. Dies right there. Check the voltage immediately, and it's down to 5.5V. Took it inside, measure again... slowly creeping up. 6V, 6.5V, 7.5V... takes maybe 20 minutes.

I will do all of the charging system tests, of course, but based on the extremely low voltage of the battery, does it seem like at some point the bike just stopped charging the battery?

Also, would voltage this low have killed my brand new AGM batter? I threw it on the charger at 9, and it was at 13.5V as of about 8 this morning. I'll check again when I get home.

[skamagedon]

sounds like a rectifier. maybe regulator, but probably rectifier. one of the diodes going out would cause less voltage to be produced to regulator to charge battery. if you unhook the headlight, does it stay around 9v?

[Bankerdanny]

Keep in mind that it could also be as simple as a bad battery that appears to take a charge when using the charger, but under any kind of load loses it immediately.

[TwoTired]

All you can say at this point is that the electrical load exceeded whatever the alternator provided, and the battery drained.  The cause is, as yet, unknown.

The battery self recovery is a normal occurrence to a point and is a good sign.  But, taking it down to 5.5V is like taking an electrical sledge hammer to it.  Some of the cells probably experienced polarity reversal, and is a pretty good way to kill a battery permanently.

Anyway, you test charging systems with a fully charged, good battery.  With it installed, you watch the battery voltage while the engine is revved.  If the voltage trends downward, the battery is depleting, if it trends upward, the battery is recharging.

[zabzob]

I went over the rectifier according to the FAQ. It seems to be in working order. Continuity one way and not the other. The regulator seems pretty good. Zero resistance between negative battery terminal and black wire. Zero resistance between I and F poles. Resistance between white wire and ground was 8.5 Ohms, a bit outside the range. Maybe the multimeter is out, or maybe I should subtract the 1.5 Ohm resistance in the leads.

Then I went to test the alternator. Really, I think the problem is this big melted connector that I found. Since the melting happened at the connection, I'm hoping it was just resistance between the connectors themselves. Anybody know what else could cause this? Possibly to near the breather tube, heating things up? Overload elsewhere?

While an authentic connector from vintageconnections.com would be nice, I think I'll see what the auto parts and electronics stores have in my area so I can get going as fast as possible.

[zabzob]

I decided to spring for the eight prong plug from Oregon Motorcycle. I needed a blade type fuse box and some new blade terminals to replace some gross ones in my other connectors anyway.

That could take a week or more due to what seem like longer than normal border wait times, plus a rotating Canada Post strike. I'll still see what I can find locally in the meantime. If it comes down to it, I'll just use butt connectors for now.

[skamagedon]

id check those yellows from the stator against a ground, but thats just me...

[gnarlycharlie4u]

I went over the rectifier according to the FAQ. It seems to be in working order. Continuity one way and not the other. The regulator seems pretty good. Zero resistance between negative battery terminal and black wire. Zero resistance between I and F poles. Resistance between white wire and ground was 8.5 Ohms, a bit outside the range. Maybe the multimeter is out, or maybe I should subtract the 1.5 Ohm resistance in the leads.

Then I went to test the alternator. Really, I think the problem is this big melted connector that I found. Since the melting happened at the connection, I'm hoping it was just resistance between the connectors themselves. Anybody know what else could cause this? Possibly to near the breather tube, heating things up? Overload elsewhere?

While an authentic connector from vintageconnections.com would be nice, I think I'll see what the auto parts and electronics stores have in my area so I can get going as fast as possible.

holy crap. looks like maybe it's time for some weatherpack terminals

it's been said but check your grounds and test your regulator/rectifier.

[zabzob]

Reg/rec checks out as far as connectivity/resistance goes. Alternator looks good from what I can check without taking it apart. I saved as many terminal pins as I could from the brand new harness end, and did the rest with large bullet connectors.

Last night I tested at the battery terminals (with my fully charged battery) and got 13.9V at 4000rpm with no lights on and 13.5V at 4000rpm with the lights on. From another post by TwoTired, I think this is okay:  "Depending on what RPMs the engine is doing, the Vreg can cycle on and off very rapidly, such that battery voltages read by a multimeter can average about 13.8 V.  (Unless you have a peak reading multimeter whereupon you should see voltages right at 14.5 V if the Vreg is adjusted properly.)"

After a 4 mile ride (not much, I know) the battery read 12.91v at rest.

I will be cleaning up all the grounds and replacing all the terminal pins I can when I get the new stuff from Oregon Motorcycle. Hopefully that'll get the charging system right in the range that it needs to be.

Gnarly, those weatherpack terminals look a lot more robust than the old school connectors. I'm going to think about converting to those over the winter.

[gnarlycharlie4u]

Gnarly, those weatherpack terminals look a lot more robust than the old school connectors. I'm going to think about converting to those over the winter.

you won't regret it.

you need to do a drain test on the battery. take it to autozone or advance auto or something. they'll do it for free