Considering Onboard DC Alternator Charger for Trolling Battery

[NelsonQ]

I'm installing a 12V trolling motor (Minn Kota Powerdrive V2 55lb). My plan is to have a single starting battery along with a single trolling battery. I'd like to have them both charging off the alternator on the outboard (2010 200HP Optimax) with a 60A output.

Manufacturer states a single bank DC charger (MK-1-DC) would work.

Support details list a minimum of 12A to support the single bank so no issues there.

My question is, has anyone used a similar setup, what is there experience? Example, how long does it take to recharge the battery (assuming an average 2 hours of usage). Not looking for exact details, just general experience and any positive/negative experiences.

 

[Silvertip]

Re: Considering Onboard DC Alternator Charger for Trolling Battery

The only number you can rely on is that your 55# motor will draw 46 amps maximum. Slower speeds current consumption cannot be predicted since there are too many variables. Although your alternator may have 60 amp output, the engine itself draws considerable power so you probably have about 40 amps available for charging purposes. Therefore, if you run the troller for one hour at maximum current draw you must also run the motor one hour at wide open throttle to come close to replacing that amount of current. A 12 amp on-board charger would take a minumum of 4 hours to replace that amount of current.

 

[NelsonQ]

Re: Considering Onboard DC Alternator Charger for Trolling Battery

Silvertip....thanks for your input... that was the information I was looking for. Unfortunately, it doesn't look like those DC Chargers are worth their weight in scrap metal. I don't have an AC source nearby so I'll have to resort to dragging the battery with me to charge it once I've run it down.

A point of interest, the manual from Minn Kota, on the 12V indicates 1A per # of thrust or 55A draw. On the 24V, it indicates .76A.

I went with the 12V and used the recommended 60A in line fuse (which i will in the future replace with a breaker as soon as I can get one ordered locally)

I also ran 20ft of wire (4 AWG) front to back but finding a quick connect/disconnect for 4 AWG is proving to be a daunting task.

 

[fishrdan]

Re: Considering Onboard DC Alternator Charger for Trolling Battery

Yeah, the 12amp output of the DC charger won't do squat for your TM battery. But, why not use an ACR or automatic charging relay? Once the main battery is charged up, the ACR will cut over to the TM battery and put the outboard's full output (what ever that might be at your cruising RPM) to the trolling battery.

I have a bit different setup with a 24V bank being charged up by a 100 amp alternator on an I/O. But, after trolling with the TM for 4-6 hours, I can switch to trolling off the main and charge the TM batteries back up in 1-2 hours. I doubt you will be able to do this with your OB as it doesn't put out near the current of an 100 amp alternator at idle, but if you are cruising, you should be able to put some charge back in the TM battery between fishing holes. Then on the run back to the marina you might top it off... It really depends on how much you use the TM and how long you run the OB.

4AWG quick disconect

 

[Silvertip]

Re: Considering Onboard DC Alternator Charger for Trolling Battery

Attempting to keep a troller battery TOPPED OFF with an outboard is not a good idea since there simply is not enough alternator output to do that. You can certainly prolong the run time but you will still need to top the system off with a charger.

 

[Silvertip]

Re: Considering Onboard DC Alternator Charger for Trolling Battery

A point of interest, the manual from Minn Kota, on the 12V indicates 1A per # of thrust or 55A draw. On the 24V, it indicates .76A..

Minnkota specs indicate the 55# motor draws 50A max and a 24 volt draws 42A to 56A max depending on model. Don't know how you arrived at the .76A.

 

[NelsonQ]

Re: Considering Onboard DC Alternator Charger for Trolling Battery

Minnkota specs indicate the 55# motor draws 50A max and a 24 volt draws 42A to 56A max depending on model. Don't know how you arrived at the .76A.

Sorry, my answer was somewhat confusing. It was .75A or .76A per 1lb of thrust on a 24V system, so for 55A would be around 42A as you've stated. 1A on 12V or 55A. This is what it states in the PowerDrive v2 manual for the 12V or 24V versions of that model.