Topic: The $6 Charging System Output Improvement Mod

[PeWe]

Any specific ground connections that have to be improved?

1. Grounding the rectifier at bottom with a thicker wire direct to battery.
2. Make sure that main harness ground connection at the seat lock has paint scratched off on lock bracket and frame.

This is vital on stock rectifier too.
I have thoughts of a thicker ground wire from battery to headlight connector and eventual relays.

My K6 with relays to headlight (and ign coils) has lower voltage dip when headlight is on than my K2 without relays.

I have a voltmeter connected at front to black and green in headlight bucket on both bikes. The black wiring, ("system 12V") seems to be better if relays relieve it.
This indicate weak wires/connectors? The harnesses are new aftermarket since build, on the road 1 year ago.

[PeWe]

This is already a product!
Just order the circuit and mount it on a cooler.
An alu plate of right size might be enough. Clamp the circuit in place by another alu plate.
It must be wheather proof?
Hi temp sealer around it to not let water enter the cooling surface.

I know that silicone and electronics is not a good thing but here OO with hi temp silicone to seal around the circuit, right?

I thinking on a terminal block with correct distance between connectors to attach soldered rectifier/wires to the mounting plate. Fastened by  2 screws.
https://media.rs-online.com/t_large/F8208366-01.jpg

Improve ground wires and grounding points is a good advice for all bikes.

The "problem" is to find a correct connector that fits the main harness. Replace main harness connector to fit a new connector is not for me.

[dazemc]

Any specific ground connections that have to be improved?

1. Grounding the rectifier at bottom with a thicker wire direct to battery.
2. Make sure that main harness ground connection at the seat lock has paint scratched off on lock bracket and frame.

You're most important connections are going to be the ones from your, battery negative to frame and your battery positive to charging voltage, along with every wire involved in charging. You'll see the most benefit from increasing the gauge on these wires. Bigger the better works but only to a point. Personally I'm going to run 4/0 cable for my battery ground to chassis. Oh yeah I almost forgot the starter wire because I don't have one right now.

This is vital on stock rectifier too.
I have thoughts of a thicker ground wire from battery to headlight connector and eventual relays.

My K6 with relays to headlight (and ign coils) has lower voltage dip when headlight is on than my K2 without relays.

I have a voltmeter connected at front to black and green in headlight bucket on both bikes. The black wiring, ("system 12V") seems to be better if relays relieve it.
This indicate weak wires/connectors? The harnesses are new aftermarket since build, on the road 1 year ago.

So you do not need to run wires all the way to your negative battery post when running grounds. I mean you can if you want, but if you have a good negative to chassis ground connection, then you are just adding resistance and a failure point with more wire. You want to find, or make, a ground as close as you can to what you are grounding, path of least resistance. Without a relay on the headlight you are running the power up through a switch on your handlebar that is known to build up corrosion. Even with an immaculate headlight switch you are still adding resistance. With a relay you are running power from the battery to the headlight. The headlight switch, switches the relay on, rather than the headlight on. Definitely running a higher gauge positive wire and relay to your headlight will improve things considerably. 

This is already a product!
Just order the circuit and mount it on a cooler.
An alu plate of right size might be enough. Clamp the circuit in place by another alu plate.
It must be wheather proof?
Hi temp sealer around it to not let water enter the cooling surface.

You can find heatsinks online fairly easy. You could just use a chunk of aluminium or copper it'd help if it was contacting the frame too because the more mass you have the more heat capacity. The more surface area you have the higher heat transference though, that's why there is so many channels cut through heatsinks.
If you want to be able to easily change the rectifier in the future then you'll want to use either thermal paste/grease or thermal pads. Nothing wrong with using a thermally conductive adhesive though, just a bit harder to remove from the heatsink.

I know that silicone and electronics is not a good thing but here OO with hi temp silicone to seal around the circuit, right?

Dielectric grease is used to prevent corrosion on electrical contact points and it is silicone based, so silicone is safe. I mean if you are really worried about weatherproofing then I don't see why you couldn't just sandwich the rectifier between two heatsinks and run a bead of sealant between the gap.

[PeWe]

The ground to various loads are distributed by the relatively thin green wire in main harness that is grounded (hopefully) at the seat lock to frame unless paint is an isolator decreasing the contact area.

Battery ground to frame- engine is OK. I filed off the paint on frame (engine bolt) where connected, other side of frame plus engine. Electrical starter work fine.

I think the 12V can be extra affected by the thin wiring, connectors and simple  switch for head light.
Relays will take that load away from the 12V (black) wiring.

This is something which is visible when measure the voltage with a voltmeter constantly connected and supervised while riding.

No voltmeter no problem seen.

[American Locomotive]

So I tested it today, and I did manage to kill the rectifier. I just completely disconnected the + lead from the rectifier and slowly increased the throttle. It went up to about 55v at which point the rectifier let go and shorted. Strange, as most Schottky diodes seem to do okay in reverse breakdown. I guess these particular diodes just don't tolerate reverse breakdown very well, or there was a big inductive kick when they broke down and a couple hundred amps pushed though the diodes backwards.

I don't think it will be an issue for most people with well sorted electricals, but if you do have flaky wiring, there is a chance you could damage the rectifier with a momentary opening of the charging circuit. But there is a simple and cheap fix:

https://www.digikey.com/product-detail/en/littelfuse-inc/TP5KP18A/F7617CT-ND/6174237

Solder that across the + and - outputs of the rectifier, and it will clamp the output at 20v maximum. It might technically be a better idea to install two of them on the AC side (between each AC line?), but I think it should work the same on the output. I'll order the diode and a new rectifier and test it out. If it works reliably, I'll update the first post with it.

So good catch Hondaman!

[PeWe]

GOOD UPGRADE!!

The rectifier + lead to battery is via the harness, the red/white can rather easy be disconnected at it's short end on the battery plus cable.

The other small irritating connections beside to starter solenoid have made problems several times for me on my K6, if not disconnected, corroded. Really short wires squeezed  between frame and harness. They should be longer to be routed better.

Good idea to protect that circuit. I intend to use stock harness so that is a must.

The rectifier is very "expensive" for me, not $6 US, ! $25US ! + $3 US shipping for 2 pcs. Still a very low price.

OK, I look for that little bugger near me.

Relays is a good idea to install when doing this if not already done.
I have prepared to upgrade my K2 with 3 mini relays for Hi, Lo and ignition. This will soon be done all parts waiting to be connected. Hopefully tomorrow when I'm working from/at home.

The mini relay is half the size as that std Auto relay that is bulky inside headlight bucket.

 Red/White wire can easily be disconnected close to the thick battery + cable


Small mini relays take less space. Some extra Scotch electrical glass tape to isolate all connectors on the relay to avoid short when the rectifier is pressed in to all connectors.

[American Locomotive]

There are other TVS diodes that would work as well. They just need to be rated for a 20-40v clamping voltage, and at least a 20+ amp pulse current rating.

[PeWe]

There are other TVS diodes that would work as well. They just need to be rated for a 20-40v clamping voltage, and at least a 20+ amp pulse current rating.

You have read my thoughts when I searched for an alternative one hour ago?

https://www.elfa.se/Web/Downloads/_t/ds/5KPxx_eng_tds.pdf?pid=

I hope link works. OK here but I have already downloaded the file

[American Locomotive]

Yup! Just make sure which ever one you get is has a minimum stand off voltage a few volts above your operating voltage, and a maximum clamping voltage below the 45v rating of the rectifier. I would go for the bi directional one, as it will protect from surges from either polarity.

[maxheadflow]

Not sure why you need voltage clamping as long as the battery is in the circuit.  The battery will keep the rectifier from having PIV issues.   The main issues are keeping all the connections tight.  The stock bridge can blow if power, ground or any of the phase connections are lost.

BTW,  Schottky diodes do handle surges pretty well, their turn on time is really fast. Used to use them in circuits when fast 5V/3.3 TTL/cmos was the rage.  They can have a bit of "on" junction capacitance which can make them have trouble turning off but this stuff keeps getting better. 

[PeWe]

That little red/white wire connects to battery + cable close to battery just under the frame. 

If (when) that bullet plug connection is apart the rectifier will go. It sit in the upper right corner visible with side cover removed.
It sit with red hose under the right upper cover attachment hole.
(Aftermarket CB750 K2 main harness, Honda stock battery cable)

[American Locomotive]

Not sure why you need voltage clamping as long as the battery is in the circuit.  The battery will keep the rectifier from having PIV issues.   The main issues are keeping all the connections tight.  The stock bridge can blow if power, ground or any of the phase connections are lost.

Just a bit of added protection if an intermittent fault were to happen. I guess it's really not a big deal at all if your wiring and connections are up to snuff. I also suppose that if you're looking at charging system improvements, step 1 would be to make sure all of your connections are good.

[PeWe]

More good info to this thread
http://forums.sohc4.net/index.php/topic,43684.msg453904.html#msg453904

[dave500]

i just use a rectifier from a modern bike and bosch regulator,my 550 will charge at idle speeds headlight on.

[rotortiller]

i just use a rectifier from a modern bike and bosch regulator,my 550 will charge at idle speeds headlight on.

Doesn't get any better than that, especially for a 550.

[dave500]

i dont ride at night either,so ive pulled the instrument globes out,gives a boost.

[rotortiller]

Yup Dave. Lots of options. LEDs on high demand components however avoiding stupid aftermarket monster coils etc to make you into "Rodney Road-Racer" will keep the bike electrics running at healthy pace.  I put an LED tail light bulb in one of my bikes a few days ago and other than hopefully lasting longer the bike voltage and rpm is the same but it's a 750. I initially tried the LED bulb on my H2 triple and it threw the brake light monitor into a fit so I had to put it somewhere. LOL

[PeWe]

Yup! Just make sure which ever one you get is has a minimum stand off voltage a few volts above your operating voltage, and a maximum clamping voltage below the 45v rating of the rectifier. I would go for the bi directional one, as it will protect from surges from either polarity.

I guess this one will due
5KP18A
https://www.ebay.co.uk/itm/192412539547


Alternatives with close values.

https://www.elfa.se/Web/Downloads/_t/ds/5KPxx_eng_tds.pdf?pid=

Better charging at lower rpm will be interesting to see.

[HondaMan]

i just use a rectifier from a modern bike and bosch regulator,my 550 will charge at idle speeds headlight on.

There's a good idea, Dave! What bike did the regulator come from?

[dave500]

im not sure Hondaman?it was a permanant magnet type though with the regulator dead,im just using its rectifier leads,been great for years.

[Deltarider]

If that implies the alternator is working at a 100% of its capacity all of the time, I don't think that's an elegant idea, but that's just me.

[rotortiller]

that implies the alternator is working at a 100% of its capacity all of the time

Not necessarily  as Dave stated he is using only the rectifier portion of the RR unit but employing a Bosch regulator.

[PeWe]

If stock CB750 charging system does not charge properly. It is possible to improve it.
My CB750 K2 is now working very stable.
This thanks to improved wiring, cleaned connectors, additional ground.
Relays with thicker durable  wires (2.5mm2) from battery for less voltage drops/power thieves.

A constant installed voltmeter to view while riding to verify not working charging system and see the result of adjustments.

My voltmeter between gauges verified by multimeter measured battery poles. Diff was +0.2 V on battery.
I had to buy a battery for another multimeter to hook up and see which is correct.
It show same result, my voltmeter between gauges show 0.2 too low.

My bike has GEL battery that must get lower voltage, 14.1V for longer life.

So max voltage visible at voltmeter between gauges while riding for the GEL battery is around 13.9V.  I think I see that at next ride after todays adjustment, or if another 1/8 turn counterclockwards on volt adjuster screw on regulator is needed.

The bike is now ready for the TS Schottky rectifier.

[Deltarider]

I now remember I've read about the subject on the German site in 2012. I wonder, isn't the Schottky diode in any of these aftermarket rec/reg combi's? BTW, some Germans seem to have bad results with the HN-047 type. Just passing it on. Although I like to make things myself, in this case, wouldn't it be best to fit the rectifier of a modern bike?

[PeWe]

I heard that some are working at full constantly, burning the excess voltage to ground running very hot.
The old Honda throttling design by the field coil is good.