Onboard DC Alternator Charger help

[wildwood11]

I am running a 1975 Evinrude 75 hp Hustler on my 16' boat. I have a perko with 2 batteries, one for starting and one for trolling. The current system is to haul the 2nd battery out on the daily and charge it inside. I saw that Minn Kota has an onboard DC alternator charger and figured this would be a great ting to get more juice back in the battery. Thanks to a helpful member I found out today my motor alternator puts out only 6 amps. The Minn Kota suggests a 12 amp min in order to achieve full output from the charger. Has anyone used one of these before? Any suggestions? Can I not use this system? Will it still help?

Thanks

 

[tx1961whaler]

Re: Onboard DC Alternator Charger help

Your source of power is from the outboard, which only puts out 6 amps @ 13Volts. The "magic box" cannot produce any more power than what it is given. The Minn-Kota box is to provide a better regulated charge current for deep cycle batteries.

 

[wildwood11]

Re: Onboard DC Alternator Charger help

So it will not provide any additional charge to the battery or batteries? They advertise "putting additional juice in the trolling battery on runs between fishing spots"

 

[Silvertip]

Re: Onboard DC Alternator Charger help

So it will not provide any additional charge to the battery or batteries? They advertise "putting additional juice in the trolling battery on runs between fishing spots"

Yes -- any charging system will "add" a charge to the battery. But again, how much it adds and whether it is worth the cost depends on what goes INTO that magic box. You have a 6 amp alternator. Your troller draws roughtly 40 - 45 amps if it is a 45 - 55# thrust unit. So the long and short of this is that if you ran the motor for one hour and it drew 45 amps from the battery, you would need to run the boat wide open for nine (that's the number 9) hours to replace that current. So a five minute jaunt to another fishing hole would add little to nothing to the battery. Batteries are buckets of electricity. If you use more than you put back you eventually end up with an empty bucket. There is no free lunch here.

 

[wildwood11]

Re: Onboard DC Alternator Charger help

So the bottom line is 6 amps just doesn't cut it. Too bad the reviews online are good for people who have only 10 - 12 amps. I never expected it to completely recharge the battery but a boost would be good.

 

[wildwood11]

Re: Onboard DC Alternator Charger help

Any other suggestions for me regarding trolling motor use?

 

[Silvertip]

Re: Onboard DC Alternator Charger help

Any other suggestions for me regarding trolling motor use?

Continue doing what you are doing. Or add an on-board charger (one that plugs into house power at the dock). If an extension cord is out of the question or you don't have shore power then you have no option for charging. You can add another battery to extend run time but that means you now have two of them to lug wherever it is you charge them at. Don't even think about solar panels.

 

[wildwood11]

Re: Onboard DC Alternator Charger help

Well as you guys have pointed out there is no secret and beggers can't be choosers I am running a motor from 1975 afterall. One more question just for interest sake, does the DC alternator basically do the same thing as my Perko? When I turn the Perko to the ALL setting I think the alternator charges both batteries.

 

[Silvertip]

Re: Onboard DC Alternator Charger help

Well as you guys have pointed out there is no secret and beggers can't be choosers I am running a motor from 1975 afterall. One more question just for interest sake, does the DC alternator basically do the same thing as my Perko? When I turn the Perko to the ALL setting I think the alternator charges both batteries.

The Perko switch and the alternator have totally separate functions. Sort of like a light switch in your house and the ceiling light it controls. The Perko switch is a traffic cop for the charging current from the alternator. OFF cuts power to everything in the boat that is connected to the COM terminal on the switch. You NEVER switch to OFF with the engine running unless you want to muck up the charging system. When set to BAT 1 you can start the engine, run accessories and charge ONLY BAT 1 when the engine is running. Set to BAT 2 you can start the engine, run accessories and ONLY BAT 2 will charge. When set to BOTH, you can start the engine, run accessories and charge BOTH batteries at the same time (but it takes twice as long because those two batteries look like one giant one to the alternator). Of course there are folks that do not wire dual battery switches the way they should be so not knowing how yours is wired, who knows how the switch operates.

 

[wildwood11]

Re: Onboard DC Alternator Charger help

That's exactly how mine works Supreme. But it sounds based on what people are saying here that the DC onboard charger does the same thing. It takes the 6 amp charge AFT and splits it to charge your trolling motor batteries. Like the Perko set to ALL it would take twice as long.

 

[Silvertip]

Re: Onboard DC Alternator Charger help

But your problem is that the engine doesn't have enough alternator output to charge both batteries at the same time. That is what makes the switch so handy. Don't over-think the switch. If you are intent on adding juice to the troller battery, make sure only IT is selected whenever the engine is running. But START the engine on BAT 1 and THEN switch to BAT 2 which you run to another spot. If you start the engine on BAT 2 all you do during the run replace some of the juice you sucked out just starting the engine. Don't worry so much about the start battery. If your engine starts normally, you can start it many dozens of times before it would give you any trouble. Good heavens -- electric start outboards years ago didn't even have alternators and on smaller motors a battery lasted all summer without charging. One last comment here. Someone added the Perko switch to try and accomplish the same thing you think the magic box will do. Fact is, even the Perko switch was not a good investment in your situation. Don't add something else that won't make any difference. Use what you have, use it correctly, and you will get the little help but don't plan on being able to stay on the water twice as long as before. It ain't going to happen. You still need to fully charge the troller battery after every use.

 

[wildwood11]

Re: Onboard DC Alternator Charger help

Ok, thanks for all the info Silvertip. I learned a little about marine electronics. No magic box. If anything Ill just add another battery, so that I can troll longer and an onboard charger that plugs in when I dock.

 

[Silvertip]

Re: Onboard DC Alternator Charger help

Ok, thanks for all the info Silvertip. I learned a little about marine electronics. No magic box. If anything Ill just add another battery, so that I can troll longer and an onboard charger that plugs in when I dock.

Wise choice.