Calling electrical gurus! Help!

[Tim22]

Hi all
I have recently experienced the demise of my batteries at the hands of an unruly charger. As a result I am planning an electrical upgrade that will replace the charger with a Sterling Ultra 30 Amp charger. I am also planning to modify the 1/Both/2/Off switch as per Maine's article at http://forums.sailboatowners.com/index.php?threads/1-both-2-off-switches-thoughts-musings.137615/

I am not an electrical or engine guy but have been doing my research and have attached a plan of what I want to do. I would be extremely grateful if the electric gurus would provide their feedback. Also, I have a couple of questions

1. The modifications to the 1/Both/2/Off switch require that I remove the jumper from the alternator to the starting motor and replace it with a larger wire connected to the positive terminal of the house battery bank. I spent a bit of time looking at the engine today and am not sure which wire I am removing. I have attached a couple of photos of the alternator and starter in the hope that someone will clarify this.

2. The Sterling manual (echoed by Maine) says that the charger case ground (DC) needs to be run to the negative bus at the DC Panel. Is it acceptable to run this ground wire to the ground on the engine. This is a more direct route in my boat. If this is acceptable can anyone tell me exactly where on the yanmar 2gm20f the grounding bus is located.

The boat is a 1997 Hunter 310 and I think most of the details are included on the drawing.

Many thanks
Tim

 

[kloudie1]

Not much help here but the wire terminal under the big red wire is the one that has the alternator direct wire.. Problem is that there are two reds in that connector.. the other one goes to a fuse then to the instrument panel. You'll have to do some detective work to figure out which is which, but tracing from the alternator should not be difficult .. the red on the alternator (B) is the one you are looking for.

 

[Tim22]

Here is another photo of the terminal with the big red wire. There appears to be two smaller red wires behind it. Am I looking for one of those wires that run to the back of the altrnator?

Thanks
Tim

 

[Jim 5757]

You'll need to physically trace it back to the battery but that fat red wire on the starter should be the one you're looking for. As for the alternator it should be marked "+" or "Pos". Do you have an ammeter on the panel? If so, you should change it to a voltmeter 'cuz it won't read properly after rerouting the alternator output. Mainesail has a tutorial on that as well.

 

[Tim22]

Did a bit of sleuthing and believe I have found the jumper from the alternator BAT terminal to the starter. I have attached a photo showing what I believe is the jumper marked with yellow tape at each end.

My understanding is that I should remove the jumper and add a cable directly from the alternator BAT terminal to the POS terminal on the house battery and that this should be sized and fused for 1.5 X the alternator output. The Alternator is rated at 55Amps (X 1.5 = 82.5) and the distance to the battery is 15 feet so using the using the genuinedealz.com voltage drop calculator this would require a 2/0 cable. Does this seem correct?

Thanks
Tim

 

[MitchM]

Hunter should be able to supply you with the electric circuit diagrams for all connections including those on the engine. those are always good to keep on the boat...

 

[MitchM]

for info on the wiring for the Yan 2 GM 20 F , boat diesel.com , a subscription site, may provide the electricals on the 2GM20F if Hunter can't get them to you.

 

[Maine Sail]

Hi all


1. The modifications to the 1/Both/2/Off switch require that I remove the jumper from the alternator to the starting motor and replace it with a larger wire connected to the positive terminal of the house battery bank. I spent a bit of time looking at the engine today and am not sure which wire I am removing. I have attached a couple of photos of the alternator and starter in the hope that someone will clarify this.

With your stock alternator the charging improvements will only be a minimal improvement so what you gain is the protection from blowing your diodes. In the harness is a red wire that goes over to the starter post from alt B+. This is the wire you'd remove. Unless you have a high performance alternator system this part of the upgrade is a nice to do but not an absolute must do..

2. The Sterling manual (echoed by Maine) says that the charger case ground (DC) needs to be run to the negative bus at the DC Panel. Is it acceptable to run this ground wire to the ground on the engine. This is a more direct route in my boat. If this is acceptable can anyone tell me exactly where on the yanmar 2gm20f the grounding bus is located.

]

This would be fine. Look for the big black battery cable and where it attaches..

 

[Maine Sail]

Did a bit of sleuthing and believe I have found the jumper from the alternator BAT terminal to the starter. I have attached a photo showing what I believe is the jumper marked with yellow tape at each end.

My understanding is that I should remove the jumper and add a cable directly from the alternator BAT terminal to the POS terminal on the house battery and that this should be sized and fused for 1.5 X the alternator output. The Alternator is rated at 55Amps (X 1.5 = 82.5) and the distance to the battery is 15 feet so using the using the genuinedealz.com voltage drop calculator this would require a 2/0 cable. Does this seem correct?

Thanks
Tim

Yep that looks like it. To be sure disconnect both ends and do a continuity test. 1GA wire should get you to about 2% voltage drop.. You'll never see 55A out of that Hitachi anyway (perhaps for a few seconds while its cold) so the drop will actually be less...

IMPORTANT: The small terminal on the starter post should NEVER be UNDER the large cable from the battery bank!! The largest load is ALWAYS on the BOTTOM with smaller loads (terminals) stacked on-top..

 

[Tim22]

Thanks for the help - most appreciated. I decided to keep the over size 2/0 cable as I may want to upgrade the alternator in the future. Wow that copper is expensive, but in the end the fear of having to upgrade it later prevailed.

I have revised the electric drawing to reflect the comments. I would be really grateful of any suggestions or improvements as I'm not really confident that I have got it right!!

Also, in Maine's article on installing a battery charger at http://www.pbase.com/mainecruising/installing_a_marine_battery_charger there is a picture of three fuses bussed together with a copper bus. (At the bottom of the page). Is it acceptable to use a piece of copper flat bar (1" X .125") or is there some magicical alloy or processing that is required. I am in fresh water if that makes a difference.

Again, I'm truly grateful for all the assistance I've received on these forums. It really is a remarkable community

Tim