Recommended extension cord for charging boat batteries 2025

NorthernBasser reply :

I'll be getting my boat soon, and will need to get an extension cord to charge my 3 boat batteries.

Quick question, will this suffice, or would you recommend a different one?

https://www.amazon.com/gp/product/B0020YHX0E/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1

WRB reply :

You don't need a heavy duty cord, any outdoor 3 wire 115-120V cord will work.

Tom

Rahlow reply :

Depends on the amp draw of your charger, whatever the charger is rated, match it with the cord,

NorthernBasser reply :

This is the charger I'll be using. 3 bank, 10 amps per bank.

https://www.basspro.com/shop/en/minn-kota-digital-linear-onboard-battery-charger-mk-330d

DINK WHISPERER reply :

I just went and grabbed one from Home Depot along with a surge protector and called it good.

Russ E reply :

On 6/1/2018 at 9:53 AM, WRB said:

You don't need a heavy duty cord, any outdoor 3 wire 115-120V cord will work.

Tom

listen to what Tom said.

Most 3 bank 10 amp chargers draw less than 3 amps from the AC input.

WRB reply :

On 6/1/2018 at 10:09 AM, NorthernBasser said:

This is the charger I'll be using. 3 bank, 10 amps per bank.

https://www.basspro.com/shop/en/minn-kota-digital-linear-onboard-battery-charger-mk-330d

That is the Chargers DC output, not the 110v AC input provided by the cord.

Tom

Glenn reply :

How long of an extension cord do you want to use? If you're looking at a 50+ footer, you want an 8 GA cord. 12 gauge is fine for less than 50'.

Hope that helps!

NorthernBasser reply :

On 6/1/2018 at 1:48 PM, Glenn said:

How long of an extension cord do you want to use? If you're looking at a 50+ footer, you want an 8 GA cord. 12 gauge is fine for less than 50'.

Hope that helps!

Honestly, I really only need 25 ft, but I figured I'd get 50 just in case I'd need the extra length at some point.

You mention 16 gauge for anything more than 50 ft, and 12 for anything under. Shouldn't it be other way around? The lower the gauge, the thicker the cord?

Thanks.

Rahlow reply :

The longer the cord the larger the gauge needs to be 12 is larger wire than 14, 16 etc. Look at the rateing for the charger, not the output, but what the charger will draw from the 110 volt supply. Should be listed in the manual or on the charger.

BigAngus752 reply :

Is this boat to be stored indoors or outdoors? Is your charger (along with your batteries and battery cables) located in an area of the boat that may still contain water when you plug your charger in? I know that there is always some water left rolling around my battery trays when I get back from fishing.

I highly recommend that you make sure that you plug whatever extension cord you use into a GFCI outlet or, preferably, into a circuit protected by a GFCI breaker. Make sure you choose a cord rated for outdoor use if it's going to be outdoors. Even if your boat is stored indoors, I would not recommend the cord with the "lighted ends". The shorter the cord, the less the resistance. The heavier the wire, the less the resistance. 50ft. of 16GA would be just fine for your charger. I use a 50ft., 12GA, outdoor-rated extension cord. When we travel and I'm charging the boat while it's parked outside a cabin with sketchy electrical components and it's pouring rain I don't worry it...as much. But that's me.

J Francho reply :

I always just grabbed whatever cord was on the hook in the garage. Never really put much thought into it. Never had a problem.

Tennessee Boy reply :

Short answer: That will work.

Long answer: Watts are equal to voltage time amps. Example on the link you gave for the cord you are considering 15amp x 125 volts = 1875 watts. If your charger really did deliver 10amps at 12 volts times 3 banks you have 10 x 12 x 3 = 360 watts so at this rate your extension cord would be pulling around 3 amps (360 watts / 125 volts) from the wall depending on the exact voltage on the wall socket. WAY below the 15 amp rating on the cord.

Glenn reply :

On 6/1/2018 at 6:13 PM, NorthernBasser said:

You mention 16 gauge for anything more than 50 ft, and 12 for anything under. Shouldn't it be other way around? The lower the gauge, the thicker the cord?

Yup, I accidentally got it backwards. I fixed my post.

NorthernBasser reply :

On 6/1/2018 at 7:57 PM, BigAngus752 said:

Is this boat to be stored indoors or outdoors? Is your charger (along with your batteries and battery cables) located in an area of the boat that may still contain water when you plug your charger in? I know that there is always some water left rolling around my battery trays when I get back from fishing.

I highly recommend that you make sure that you plug whatever extension cord you use into a GFCI outlet or, preferably, into a circuit protected by a GFCI breaker. Make sure you choose a cord rated for outdoor use if it's going to be outdoors. Even if your boat is stored indoors, I would not recommend the cord with the "lighted ends". The shorter the cord, the less the resistance. The heavier the wire, the less the resistance. 50ft. of 16GA would be just fine for your charger. I use a 50ft., 12GA, outdoor-rated extension cord. When we travel and I'm charging the boat while it's parked outside a cabin with sketchy electrical components and it's pouring rain I don't worry it...as much. But that's me.

For now I'll be storing the boat in a storage unit. The charger is mounted in the back by the batteries. I have yet to take the boat out yet. I should be finally getting it late next week. As far as I know, it's just a regular old outlet.

Also, why do you recommend not using the lighted ended cords? I've been told they're nice because then you can tell it's charging?

BigAngus752 reply :

On 6/2/2018 at 11:22 AM, NorthernBasser said:

For now I'll be storing the boat in a storage unit. The charger is mounted in the back by the batteries. I have yet to take the boat out yet. I should be finally getting it late next week. As far as I know, it's just a regular old outlet.

Also, why do you recommend not using the lighted ended cords? I've been told they're nice because then you can tell it's charging?

Just experience. I've seen a dozen guys buy them because they were on sale only to have the ends crack or chunks break off during normal use. The plastic seems to be more brittle. One or two drops on the floor will sometimes shatter them. Perhaps they have improved and it's not a problem anymore.

NorthernBasser reply :

On 6/1/2018 at 7:57 PM, BigAngus752 said:

Is this boat to be stored indoors or outdoors? Is your charger (along with your batteries and battery cables) located in an area of the boat that may still contain water when you plug your charger in? I know that there is always some water left rolling around my battery trays when I get back from fishing.

I highly recommend that you make sure that you plug whatever extension cord you use into a GFCI outlet or, preferably, into a circuit protected by a GFCI breaker. Make sure you choose a cord rated for outdoor use if it's going to be outdoors. Even if your boat is stored indoors, I would not recommend the cord with the "lighted ends". The shorter the cord, the less the resistance. The heavier the wire, the less the resistance. 50ft. of 16GA would be just fine for your charger. I use a 50ft., 12GA, outdoor-rated extension cord. When we travel and I'm charging the boat while it's parked outside a cabin with sketchy electrical components and it's pouring rain I don't worry it...as much. But that's me.

So an adapter like this would be ok?

https://www.google.com/aclk?sa=l&ai=DChcSEwje_KCVo7XbAhXIwMAKHdz0CTwYABAQGgJpbQ&sig=AOD64_3unp70bSNkepGwlEGNi9ASjUkd7A&ctype=5&q=&ved=0ahUKEwiBgJyVo7XbAhVh7YMKHf0pDlMQ9aACCEk&adurl=

Further North reply :

Like anything else: don't go cheap, you'll regret it.

Good quality, heavier wire the longer you go, and if cord feels warm...bump it up...

...also, cheap cords tend to be less durable and won't stand long term abuse.

I have one semi-permanently mounted so that it hangs down from the garage ceiling right above where my charger plugs in...one less thing to step on/trip over on the garage floor. That one is a 50', over-rated for the duty, because I'm a belt ans suspenders guy.

I have another in my "boat box" that goes along on trips. That one is 100', and the heaviest duty cord I could find because:

See above "belt and suspenders."
I never know how from an outlet I'll be at say, a Canadian fishing lodge.
I never know what conditions it'll have to endure (other fishermen walking on it, running over rocks, how many boats might have to be plugged into it, etc.).
- More than once we've had to link two 100' cords together to get to a decent power source.
- Example: Houseboat in the middle of Lac Suel , six boats to charge running off a generator at the back of the house boat...

BigAngus752 reply :

On 6/2/2018 at 11:16 PM, NorthernBasser said:

So an adapter like this would be ok?

https://www.google.com/aclk?sa=l&ai=DChcSEwje_KCVo7XbAhXIwMAKHdz0CTwYABAQGgJpbQ&sig=AOD64_3unp70bSNkepGwlEGNi9ASjUkd7A&ctype=5&q=&ved=0ahUKEwiBgJyVo7XbAhVh7YMKHf0pDlMQ9aACCEk&adurl=

First, if you plan to plug the cord into an outlet in your garage check to make sure that your garage circuit isn't already protected. Look in your breaker box and see if the breaker for the garage outlets is GFCI. If not, examine all the outlets. The building may have installed a standard breaker but then installed a GFCI outlet as the first outlet for the run through the garage. That outlet will then offer protection for all of the outlets through the rest of the circuit (but not the circuit between the breaker and the first outlet).

If you have no GFCI anywhere you could use the item you linked to. It's not ideal but it may work for you. Those devices sometimes have issues with "start-up" draw or any significant variation in the draw. You probably won't experience enough of that with a battery charger to cause that device to trip. Honestly, you aren't saving much money with it, though. For just a few dollars more you could buy a GFCI outlet from one of the big box stores and one from the big box store will come with instructions in the box as they expect the average homeowner to do the install. If you can turn the breaker off and use a screwdriver you can install an outlet.

WRB reply :

I have charged my boat batteries using my onboard charger with, 1 or 2, 50' garden verity outdoor 3 wire grounded 110v extension cord or cords in several states over the decades without any issues in all types of weather, plugging into whatever 110V-125V, 15 to 20 amp receptacle that was available. If you feel the need for GFI protection go for it if the area get wet.

Tom

Further North reply :

On GFCIs...I had something weird happen last year.

Our detached garage where we store the boat is GFCI protected, and there's a circuit breaker for the garage in the house...pretty standard.

We had a close by lightning strike that tripped the breaker and the GFCIs (for some reason the garage seems to be more sensitive to lighting strikes than the house is, so I am in the habit of checking the garage after every thunderstorm.

Sure enough, the GFCIs had popped, so I re-set them, didn't think about it after that.

I had a weird spot in my summer last year where I didn't take my boat out for about 3 weeks...fished with some buddies, was busy one weekend...anyway, went out to get ready for an after work run to a local lake...the while boat, except the trolling motor is dead as a doornail.

The strike, or something, had also tripped the circuit breakers on the boat. My main battery charges the battery for the remote for my Ulterra, and the electronics battery runs the 360°, which pulls a constant draw if you don't shut it off...I hadn't installed shut off switches...I figured I didn't need them as the boat is plugged in any time it's in the garage.

Those two batteries were deader than dead.

I've since installed on/off switches on all three systems so I don't run into this again. Should have done it from the get go, but I took the easy way out.

PECo reply :

On 6/1/2018 at 10:09 AM, NorthernBasser said:

This is the charger I'll be using. 3 bank, 10 amps per bank.

https://www.basspro.com/shop/en/minn-kota-digital-linear-onboard-battery-charger-mk-330d

From the manual https://minnkotamotors.johnsonoutdoors.com/sites/johnsonoutdoors-store/files/product/minchargers/1036048/ProductManual/MIN_productmanual_ChargerDigital.pdf?_ga=2.163682232.625704911.1528026689-627013622.1528026689 :

However, I'd go with the lowest gauge (i.e., largest wire diameter) and shortest length that's practical for you. I had problems with my Minn Kota Precision Charger properly detecting my batteries. I read on a forum somewhere that they're particularly sensitive to line voltage irregularities, so I upgraded my extension cord and the problem went away.

Catt reply :

Like @J Francho & @WRB I don't get overly excited over which cord I use.

My thoughts, don't use a 100' when 50' will reach & don't use a 50' when a 25' will reach.

NorthernBasser reply :

Appreciate it fellas.

Maybe I'll go with a 25' for when it's garaged, and get a 100' when I go on overnight trips.

Further North reply :

On 6/3/2018 at 7:55 PM, PECo said:

From the manual https://minnkotamotors.johnsonoutdoors.com/sites/johnsonoutdoors-store/files/product/minchargers/1036048/ProductManual/MIN_productmanual_ChargerDigital.pdf?_ga=2.163682232.625704911.1528026689-627013622.1528026689 :

However, I'd go with the lowest gauge (i.e., largest wire diameter) and shortest length that's practical for you. I had problems with my Minn Kota Precision Charger properly detecting my batteries. I read on a forum somewhere that they're particularly sensitive to line voltage irregularities, so I upgraded my extension cord and the problem went away.

Just an observation: Minn Kota's statement about not using an extension cord is absurd.

The cords attached to their chargers are nowhere near long enough to reach a wall socket.

I suspect a lawyer, and a not very good one at that, is try to play CYA for Minn Kota...

Way2slow reply :

A 10 amp per bank, 3 bank charger is going to pull less than 500 watt's. That's less than 4 amps on a 120VAC circuit

For a 4 amp circuit, a 100ft drop cord should be 14 gauge. Some charts will probably say a 50ft cord should also be 14 gauge, but 16 gauge will work just fine for 50ft or less.

NorthernBasser reply :

Stupid question. But is there such thing as overdoing it in regards to gauge/ft?

I ended up getting a 25 ft, 12 gauge cord for when it's being charged inside.

Tim Kelly reply :

No. But as a note, if you have one of the lighter gauge extension cords you ought not to use it coiled up as the coiling of the cord adds to the resistance.

PECo reply :

On 6/3/2018 at 11:15 PM, Further North said:

Just an observation: Minn Kota's statement about not using an extension cord is absurd.

And I haven’t been impressed by the robustness of Johnson Outdoors products, lately. You’d expect them to engineer a charger that CAN handle line voltage irregularities well. And don’t get me started about the issues with Humminbird Helix G2 units. . . .

On 6/4/2018 at 2:19 PM, NorthernBasser said:

Stupid question. But is there such thing as overdoing it in regards to gauge/ft?

No, but the lower the gauge, the heavier and bulkier the cord. I once bought one that was so unwieldy I returned it.

Further North reply :

On 6/4/2018 at 7:41 PM, PECo said:

I haven’t been impressed by the robustness of Johnson Outdoors products, lately. You’d expect them to engineer a charger that CAN handle line voltage irregularities well. And don’t get me started about the issues with Humminbird Helix G2 units. . . .

I am under the impression that one of their products is designed to deal with that...but I can't recall which one.

On the Helix G2s, mine have been fine, but it's small sample and they are both G2N. A couple folks I know have had issues.

Seems that the more complicated we try to get the more issues we have...it also seems like that'd be predictable.

Tennessee Boy reply :

I remember back in the day (1990s), I was on one of my Bass Club's two day tournament road trips. We were all at a lake side camp ground with 15-20 boat that needed to be changed by a few camp ground electrical outlets. We all brought long extension cords and three way socket splitters. I remember six cords plugged into one two socket outlet and there were probably multiple boats plugged into some of those cords. All of the batteries got charged, no breakers were thrown, no fires were started, and no one died. I guess it was just easier in those days.

NorthernBasser reply :

On 6/4/2018 at 10:05 PM, Tennessee Boy said:

I remember back in the day (1990s), I was on one of my Bass Club's two day tournament road trips. We were all at a lake side camp ground with 15-20 boat that needed to be changed by a few camp ground electrical outlets. We all brought long extension cords and three way socket splitters. I remember six cords plugged into one two socket outlet and there were probably multiple boats plugged into some of those cords. All of the batteries got charged, no breakers were thrown, no fires were started, and no one died. I guess it was just easier in those days.

This song is fitting, for sure. Give it a listen.

401

Recommended extension cord for charging boat batteries 2025

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