No wonder my battery wont charge

Maine Sail · Jan 5, 2013

drumbeater said:
I think it may have been the original rectifier. Don't know what blew the wire in two. I may have hooked my charger up backwards once.

That was caused by a dead short. Your batteries have thousands of amps of short circuit current in them... You got very, very lucky the wire fused before igniting the wire jacket and then the boat. This is why fusing is sooooooooo important.

Count your lucky stars!!!!

Maine Sail · Jan 5, 2013

drumbeater said:
This was in an older Evinrude Sailmaster.

It must have been connected to a battery to short that wire though.?

keys please · Jan 5, 2013

Re: No wonder ny battery wont charge

The completely black wire was your hot wire.... the one with the white tape was a neutral wire as inticated by the white tape which would then complete the connection.

onecoolair · Jan 5, 2013

keys please said:
The completely black wire was your hot wire.... the one with the white tape was a neutral wire as inticated by the white tape which would then complete the connection.

What??....Are you now talking now 120 Volts ?? We all need to be more clear here... on the color coding for 120 volts A/C Verses the color coding for 12 volt D/C.
One minute we are talking 12 volts and a Evinrude outboard connected to battery with no fuse and then you switch too the color coding for Alternating Current.
If you are talking 12 volts ...then black is -12v ground ...red is +12v hot....and thats just the basic's....
Some people just do not get how dangerous it is to not obey proper electrical color coding standards and codes as well as using properly sized fuses or breakers along with keeping A/C wiring harness runs marked and ran separately from marked D/C wiring runs so there is never any confusion. This is very,very important!! Mainsail or Stu...please chime in, maybe you can be more clear on getting this point across.

flynfol · Jan 5, 2013

I have an old Johnson Seahorse 9.9 with electric start and alternator.......never was fond of the way it was wired. Alternator wired thru the funky starter switch....no fuse. You could put a fuse between the rectifier and the switch. Great little motor(for a 2 stroke)......I just can't let it go. The positive wire had a rubber cap and red wire.......

Maine Sail · Jan 5, 2013

flynfol said:
I have an old Johnson Seahorse 9.9 with electric start and alternator.......never was fond of the way it was wired. Alternator wired thru the funky starter switch....no fuse. You could put a fuse between the rectifier and the switch. Great little motor(for a 2 stroke)......I just can't let it go. The positive wire had a rubber cap and red wire.......

The fuse always goes at the battery end. All marine battery chargers should be fused within 7" of the + post.

The rectifier/alternator is self limiting thus fusing it is only necessary at the battery end to protect the wire itself.. Self limiting means it can't fry the wire it is connected to.

The battery on the other end of the wire however packs thousands of amps of short circuit current and more than enough to start a fire. The OP got VERY, VERY, VERY lucky this did not burn his boat down.. Wires are not intended to be fuses, despite that being what happened...

This electrical fire is the result of what an unfused group 27 battery is capable of. This wire did not fuse itself and instead ignited the jacket and then the entire boat. Three minutes before this raging inferno there were four 8 year old junior sailors on this boat.... The Whaler was totaled.

flynfol · Jan 5, 2013

There might be a fusible link......but no fuse on this one.......starter might have something to do with that.......I agree that the gauge of the alternator windings would give up the magic smoke long before the heavier gauge starter wires would........but a fused/ welded starter switch can make for a interesting day.

flynfol · Jan 5, 2013

Re: No wonder ny battery wont charge

Drumbeater must have more than one device attached here.......I was commenting on the wiring for the Johnson ( sister motor) to the evinrude. In my experience, the fuse value was less the the stator winding current capability....the thought being it was cheaper to replace the fuse or rectifier than the stator. I understand Maine Sails point.......but clearly in the picture of the factory wiring from Johnson.......there is NO fuse. I could add graphic pictures of aircraft that have had catastrophic failures(some that I was PIC) with people aboard, but how does that relate to my actual post..........whatever.

onecoolair · Jan 5, 2013

drumbeater said:
Exactly my point. For some reason the charger on my 82 Hunter 22' had white tape around one of the leads from the charger that is powered by a shore power plug.
I thought white must have meant the positive 12v lead and it was not. It was ground.
Didn't mean to cause a ruckus, just posting a pic of a blown up rectifier.

Hey....Drumbeat......Sorry I did not mean to make it sound like I was just jumping on your case..But..After dealing with a boat fire myself some 12 years ago which was caused by a "Black and Decker Cordless Dust Buster"..... Sometimes A little ruckus is good if it gets some hard heads to wake up and pay attention to the safety issues involved when deal dealing with electrical systems.

NYSail · Jan 6, 2013

Maine, I have three battery banks two with a single battery and one bank(house) with three group 31's. each bank is fused within 7" of the positive post leading from charger. My question is each bank must be fused not each battery.... Correct?

monkeybars · Jan 6, 2013

NYSail said:
Maine, I have three battery banks two with a single battery and one bank(house) with three group 31's. each bank is fused within 7" of the positive post leading from charger. My question is each bank must be fused not each battery.... Correct?

depends on wheather you prefer only 4-5 inches of wire jacket burn below decks, or 20-30inches start fire and furn down there.either is better than no fuse,but safest is every single battery has a fuse,preferably the kind that mount right on the terminal.

jdhohmann · Jan 6, 2013

Re: No wonder ny battery wont charge

keys please said:
The completely black wire was your hot wire.... the one with the white tape was a neutral wire as inticated by the white tape which would then complete the connection.

remember, there is NO neutral to a DC connection, Only a positive and a negative!!!! Just sayin!!

Maine Sail · Jan 6, 2013

NYSail said:
Maine, I have three battery banks two with a single battery and one bank(house) with three group 31's. each bank is fused within 7" of the positive post leading from charger. My question is each bank must be fused not each battery.... Correct?

Yes you only need a fuse at the + post or within 7" or so at each BANK. They should be MRBF, ANL or Class T to make sure they have the AIC (amperage interrupt rating) necessary for a DC battery bank.

The caveat to that is parallel banks that are mounted far apart like 2 batts on port and 2 batts on stbd. Even though that is one bank you would be best to fuse both sides to prevent the long jumpers from shorting. On a single bank with short intrabank jumpers no real need to protect anything more than the paralleled bank unless you are concerned the jumpers could chafe.

Bank, alternator wiring (if wired direct to the bank), chargers, inverters, house panel wires etc. etc. all get fused as close to the "source" as possible. On a boat your "source" is the battery bank...

Also keep in mind that any time you change wiring sizes, or step down from larger to smaller, you need a new fuse sized for the smaller wire. A 6GA wire for the house DC panel can't share the same battery fuse that the 1/0 battery cable is protected by..

You can read more about battery bank fusing here:

Battery Fuse Sizing - How?

rardiH36 · Jan 6, 2013

Re: No wonder ny battery wont charge

Maine Sail:

Thanks for imbedding the link back to your June 2011 battery fusing article. Because of your information over the years, I did a ways back install battery terminal fuses to each of the two Group 27 batteries on my boat.

Just wanted to let you know that your advice is taken on board. And after some contemplation actually actioned upon more than just a few times! .

I've got the 2QM20 Yanmar engine that is showcased for the starting motor amperage video included within your June 2011 article. So watching it was informative. I really didn't know what the max amp draw was. Seems my 200A fuse choice was reasonable for the engine and my starting wire gauge. A few hundred starts since the fuse install and no blows yet. Also good to hear the audio in the video ... the engine sounds like mine and shimmy's around while running.

keys please · Jan 6, 2013

Re: No wonder ny battery wont charge

Jdhoh, I thought we were dealing with 120 a/c fed rectifier "powered by shore power"...I don't know what poles those two wires were connected to do you?...But they were color coded as 120 a/c hot (black wire) and as 120 a/c neutral (black with white tape) coming out of an a/c fed rectifier.... My comment was made to stir the pot and make people think...Until we use a multimeter on those leads we dont know what we are dealing with...my comment had the desired effect....
If we want to enjoy sailing... treat electricity with the respect it deserves, or risk more then just frying your boat... all the best

No wonder my battery wont charge

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