Honda BF8A

[mashby]

Can anyone let me know what the charging rate is for a 1999 BF8A. The book says 6 amps but i never get anywhere near that even with a low battery. Battery is new. I have measured about 3 amps at very high rpm.<br />Is this normal?

 

[cp]

Re: Honda BF8A

The schematics in my Honda manual show two different charging setups depending on whether you have an earlier or later model BF8A as determined by serial number. What is the serial number of your BF8A?

 

[mashby]

Re: Honda BF8A

My serial NO is BACL 1401370. a 2000my ENGINE

 

[cp]

Re: Honda BF8A

The higher serial numbered BF8A motors such as yours are shown to have a rectifier/regulator unit between the charging/lighting coil and the battery. When functioning properly the regulator should act to keep the output voltage of the rectifier at a relatively constant value, regardless of rpm. The constant voltage results in the current (amps) that will flow being dependent on the load demand which consists mainly of your battery and any other electrical devices you have on. If you are measuring three amps DC flowing, that seems to indicate that your charging/lighting coil and your rectifier/regulator are working, just that you don't have more than the three amps worth of load. If the BF8A is keeping your battery charged, you're fine.

 

[mashby]

Re: Honda BF8A

Thanks. The problem is that the battery, which is known to be OK, was discharged, approx 11.5 volts so hence I would expect the charge rate to be higher. Anyway it does seem to charge something.<br /><br />Thanks again.

 

[cp]

Re: Honda BF8A

The initial charge rate should be higher but, on a good battery, will quickly drop. The simple measurement is that there is an increase in voltage at the battery from the 11.5VDC initial reading to something on the order of 13.8VDC when the motor is running. If that is the case then it would seem your charging system is OK and the 3 amps you measure is simply a result of the charge state and internal resistance of your battery. Note that the fuse shown between the rectifier/regulator and the battery is only rated at 5 amps, so you should expect something less than that on a normal basis.

 

[mashby]

Re: Honda BF8A

I have never seen a volatge as high as 13.8v. This is what i initially expected. Car alternators run around 14 - 14.5 volts so 13.8v seems OK. I will check again when boat in launched but I seem to remember measuring 12.5v max.

 

[Boatist]

Re: Honda BF8A

Mashby<br />If your voltage does not go over 12.5 then you will not charge the battery at all. A normal voltage for a 12 volts lead acid battery is 12.6 volts at 70 degrees. Anywhere from 13.8 to 14.6 is normal charge rate. I suggest you fully charge the battery before going out for a test. Then check the voltage at the battery terminals with a good voltmeter, not the one on the dash.

 

[cp]

Re: Honda BF8A

If your rectifier/regulator is only putting out 12.5 VDC, then it will not fully charge your battery, however it will charge your battery from the 11.5 VDC you mention up to 12.5 VDC. Since you measure 3 amps flowing, some charging must be occurring, as you recognize. Do use an accurate voltmeter, and if you do not see about 13.8 VDC, then you should consider checking to verify that your rectifier/regulator is operating correctly. The easiest way to do this is with an oscilloscope, but not everyone has one of those. In view of the 3 amps you've measured, I think you'll find with an accurate meter that you're OK. Good luck.