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TOPIC: Overcharging? 15v at all rpm

Overcharging? 15v at all rpm 3 months 4 days ago #23837

  • Raygun
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My KZ has always performed very well electrically. Never a dead batteryr and it always starts pretty quickly. However, I've run it with a multimeter attached and it shows 15 volts all the time at all rpms. Idle is 15.0 and 5000rpm is 15.2 volts. So I'm assuming this is a regulator problem but I haven't gone digging yet. Tomorrow I'll check the stator output and verify the voltage on the battery with another multimeter. I've never seen this before in a motorcycle. Any insights? I've found Scotch's post about a MOSFET FH020AA and I will likely buy a kit from www.roadstercycle.com/index.htm . So I suppose I'm looking more for a confirmation of my plan going forward and an answer to why is this happening? Is there possible damage to the stator? Thanks for the help!
1982 KZ1300
2003 KLX400SR
1999 KDX220
Wife
Son
Cat x 3

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Overcharging? 15v at all rpm 3 months 4 days ago #23839

  • Kawboy
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Lead acid batteries prefer to be charged at 1.8-2.2 volts above battery voltage so 13.8 - 14.2 volts. AGM batteries prefer lower volts more like 13.2 - 13.6 volts. And the reason I mention the 1.8 - 2.2 volts is because we all have volt meters which could be out of calibration. If the resting battery voltage is 12.6 volts as measured with your volt meter you would want to measure a charging voltage of 12.6 + 1.8 to 2.2 = 14.4 - 14.8 V. It's a relative thing more than an actual thing. You're pouring a positive voltage in to the battery. The more positive the differential the faster it pours in. An AGM battery being a gell cell can't soak up the electricity as fast as a lead acid battery so you have to "pour it in " slower. Pouring the voltage in at a higher rate on the lead acid batteries will boil the water out of the acid and ruin the battery, never mind having a running voltage too high for electronic circuitry.

I wouldn't think twice about installing the MOSFET reg. They are the Cat's Ass when it comes to full current controlling regulators. When you can't regulate the voltage to the magnetic field and have to control the output voltage of an alternator running full out, then the switching mechanism needs to be top notch. The MOSFETs are renowned for high current switching. Just do it and don't look back.

Since you're looking in to a suspected problem here, don't forget that the regulator needs to sense a true voltage. If you have a corroded ground lead somewhere, the regulator could be measuring a false voltage causing the regulator to regulate at a higher output. So don't forget to check your grounds.

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Overcharging? 15v at all rpm 3 months 3 days ago #23841

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Thanks Kawboy for the quick and thorough answer to my questions. I think I'll go ahead and buy a MOSFET regulator but that leads me to the next question. I am assuming I replace the larger regulator under the right side cover but what about the smaller one near the battery? Should I do anything with it? Thanks again.

I checked the battery today and the electrolytic solution is near the low end of the range provided on the side of the battery but not too low. (I forgot how freaking huge this battery is.) I may have more work to do if I want to make sure it is all fixed which includes replacing my fuse block which I noticed is all cracked (which is probably unrelated to the high voltage but bothers me anyway). Thanks again for all your help. I'm off to search around the forum.
1982 KZ1300
2003 KLX400SR
1999 KDX220
Wife
Son
Cat x 3

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Overcharging? 15v at all rpm 3 months 3 days ago #23843

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Just looking at the service manual, it would appear that the main alternator and sub alternator are running in parallel and not being control together but rather independent of each other. The main alternator has a higher output and therefore runs 2 parallel feed wires to the battery where the sub alternator only runs 1 feed wire to the battery. I would think you would need 2 MOSFET regulator/rectifiers to do this properly and I'd have more faith in the 2 charging circuits running more evenly sharing the load than the old system with the Kawasaki regulator/rectifiers. Got to love electronics.

And maybe SCOTCH has some insite here?????

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Last edit: by Kawboy.

Overcharging? 15v at all rpm 3 months 3 days ago #23845

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can't add much ! kawboys suggestion of using 2 MOSFET's seems logical.

Answer to the P.M.: Copy and paste this to an ebay search

6 Way Fuse Holder Block 90V 115x53x42mm Car Vehicle Circuit Blade Fuse B MJW

Toss the fuses that come with this and buy some good quality ones at your auto-parts store ! !!

The over charging would suggest the regulator is shot !
1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !
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Overcharging? 15v at all rpm 3 months 3 days ago #23847

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Thanks to both of you! Definitely appreciate it. I think dual MOSFETs is the way to go and I'll head in that direction. What an interesting way to do things with dual charging systems of different sizes. Much more complex than my other motorcycles. The fuse block will be good to do at the same time just to update things. It's much easier to have spare spade fuses floating around than the glass ones. I'll be checking the outputs and resistance from the stators tomorrow so hopefully they won't need to be replaced.
1982 KZ1300
2003 KLX400SR
1999 KDX220
Wife
Son
Cat x 3

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