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BF8A Charge System

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arima_fan

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First I think I need a new rectifier/regulator, after checking the resistance between the connectors (per the Honda shop manual) I get nothing so I gather it is fried. Of course the manual says to use a specific japanese brand of meter, I used a fluke and double checked with a micronta.

But I decided (after fixing it) that I would like to use the kicker's charging system to maintain the house battery while trolling, specially when using the downriggers.

My question is how to isolate the main engine charging system from the kicker's and viceversa to prevent current backflow form one to the other.

I have the typical two battery set up with an Off/1/2/Both switch.
I realize that if I set the switch to the house battery and use the kicker the main would be isolated, but if I run the main with the switch in both or 2 (house) how can I prevent current flow to the kicker charging system.
Is there a rectifier product out there? Do I have to make my own? How?
Does it really matter?

Thanks!
 
The use of a Fluke meter should be MORE than adequate to verify resistance. I'll wager that the accuracy tolerance of the Fluke DMM is as good or better than the Sanwa or the Kowa Seki instruments although I've never seen either one of those. As a precaution though, make sure you use the Diode Test portion of the Fluke to check that bridge rectifier before condemning it. The reason being is that I'm not sure if either one of those meters specified in the service manual are digital. If they are analogue, they will automatically provide enough current to "turn on" the diodes while, on the other hand, the Fluke Ohms scale will not.

I've never done what you are proposing but my opinion is that the simplest solution would be the best. That might be to just add an inline switch to the positive line of the kicker and then keep it off when using the main. The problem with this system is that you might forget to throw the switch.

Either that or install a diode in the positive wire from the kicker to "block" incoming charge current from the main system.
The trick here is to ensure that the diode you select has an adequate "breakdown" voltage rating to prevent back-feeding the kicker charge circuit. There is probably something at Radio Shack that will work.

Of course, with each of these "solutions", you will still need to use the 1-2-both switch to isolate the house battery as you have already stated.

Good luck.
 
Mike butting in again....

Be careful of all of your assumptions you get too far along.

How is the battery switch actually wired? Most that I have seen have the main motor and wiring for the dash/accessories etc wired to the common terminal. Then starting battery on #1 terminal and house battery on #2. There are many variations, but that is the way I am assuming that you have your boat wired at this time.

The main question will be where are your downriggers wired to? Directly to house battery? Or to the common terminal?

Jimmy D's idea on the diode will work fine to isolate the kicker motor from the main motor, however, it will not isolate the main motor from the kicker unless the battery switch is turned to the starting battery only or off. (Which you may have indicated). This will work as long as the downriggers are wired directly to the house battery.

Ok...now that I have run on...all the design effort may be in vain.

The charging rate indicated in the manual goes something like this.. zero current @ 1500rpm, 1/2 amp @ about 2400 rpm, 1 1/2 amp @ 3000 rpm 3 1/2amp @ 4500 rpm and will put out about 6 amps at 6000 rpm.

Idle rpm in neutral is supposed to be about 1200 rpm plus/minus 100. Naturally, when put in gear, the rpm goes down a little at idle.

If I understood you right and you are idling with the kicker, then theoretically, it is putting out little or no current at idle.

As you can see, this post is built upon a list of assumptions.

One last comment...Some larger motors (depending on the brand), have options where you can split the charging lead out from the main power cable. This is a standard option for many brands of two strokes. If that is the case, then some other options are available.

However, using a diode isolator also causes a small voltage drop. This will further cut down of the charging of the 8 HP.

If you are going to try the diode method, this one from Radio Shack is pretty cheap. http://www.radioshack.com/product/index.jsp?productId=2062591&numProdsPerPage=60

You get 4 to a pack. They are only rated for 6 amps, but if you take all four of them and put the in parallel with each other, the current will be divided between the four (each with 6/4 amps at max output). It will also help dissipate the heat and cut down on the voltage drop.

It is cheap enough to give it a try if you are going to pursue the diode method.

Sorry to butt in and run on like this.

Mike
 
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