Marina battery charging - 30A to 15A

C

Ctarmigan

Member
On multi-day trips, my house battery can get pretty low. I'm looking to gain the ability to charge batteries while at a marina. Electrons have always been mysterious little creatures for me, so I'm running my plan past the collective wisdom of the C-Brats to ensure I'm not wildly off.

Currently, I have two batteries (AGM; house and start), and a ProSport 12 charger.

My plan is to pick up the following equipment to enable charging from 30A marina power:

Marinco 30A male to 15A female pigtail adapter
https://www.marinco.com/en/p/105SPP/Pig ... ale-To-30A

Inline GFCI cord (single female)
https://www.homedepot.com/p/Tower-Manuf ... /202510249

My thinking:
* potential for Marinco adapter failure suggests separating GFCI and adapter components, rather than going for the (more expensive) Marinco adapter with GFCI built in
* GFCI on the shore power side of things, rather than in the boat, such that GFCI protection starts ~12" from the power supply
* with little cause for plugging in anything but my charger, going with single connections all the way through the system (rather than the more common 3-outlet inline GFCI cord) presents a less complex system with no hot-but-empty female 15A sockets

Have at it. Am I asking for trouble in a way I don't realize? Is there a better way to skin my particular cat?
 
I am NOT an electrical expert but here are some of of my thoughts from a similar project on my boat(non Cdory).

I opted for the adapter plug without the short cord attached (Marinco S30-15). Reason for this I didn't want any connections exposed to weather(rain). This adapter is covered by the flap on the shore power pedestal.

I opted for a 12ga (20amp) cord (yellow) to look a little less out of place and a little less voltage drop than a 14ga cord. I have used yellow electrical tape to secure the adapter to it - keep moisture out of the connection. I use velcro ties to secure it to my bow rail, etc. so it doesn't droop onto the water. I feed it into my anchor locker through the notch where the rode comes out. This latches closed and the cord I used has the 3 prong end on it so it cannot be pulled out of the locker.

In my cuddy I have a ground fault cord similar to your example. For some reason mine cost a lot more(not sure what the difference might be). https://en.lumenco.ca/hubbell-hubgfpil1 ... Lw_wcBThis is fed through the cuddy wall into the anchor locker. My charger then plugs into it.

This leaves both connections - at pedestal and in anchor locker out of the weather if it rains. It may be better to have the gfi at the pedestal - again I am no expert. Always make connection at boat and secure cord before connecting to shore power pedestal and disconnect power at pedestal before cord from boat.

Keep an eye on charging and float voltages - especially if you will be leaving it unattended for a long period of time.

OK I'm done rambling now,

Rob
 
Does the boat already have AC power, with sub panel? Or are you using an extension cord?

Are you using a VSR or ACR between the start and house battery, or just using a 1/2/All/ off switch?

Theoretically there are reasons to put in a full AC system (Circuit breakers in, circuit breakers for each use [battery charger, water heater, refrigeration, outlets etc], with galvanic isolator, but many do just with the cord. Without going into detail, I did a minimal AC system, with a battery charger inlet for the 120 V 15 amp input,. a circuit breaker and fuse, then an outlet to plug the battery charger into.

You really should hard wire the battery charger to the batteries, and include fuses near the battery.

One should not discharge a Flooded lead Acid battery (FLA) to less than 12.2 volts steady state (no charge or discharge for more than 2 hours.

I have both used the 15 amp pigtail, and I have hard wired a 30 Amp marine male plug to an extension cord. In that case, I like to use a #12, or better yet, a #10 AWG wire in the extension cord.

Also be aware of the 2020 new standards for wiring marinas to prevent electrical shock drowning. Any new or upgrades to a marina should be to these codes


2020 National Electrical Code.

The GFP {GFCI} requirements were divided into three parts to provide clarity, according to the International Association of Electrical Inspectors.

Section 555.35(A)(1) addresses shore power receptacles with individual GFPE not to exceed 30 milliamperes. Section 555.35(A)(2) addresses 15- and 20-ampere receptacles for other than shore power with Class A ground fault circuit interrupter protection (4 to 6 mA) being provided in accordance with NEC 210.8. Section 555.35(A)(3) addresses feeder and branch-circuit conductors that are installed on docking facilities to be provided with GFPE set to open at currents not exceeding 100 mA with coordination downstream GFPE permitted at the feeder overcurrent protective device.
Click to expand...

These more restrictive GFP will often trip the GFP at the pedistal, in older boats, where the galvanic isolator, an improper wiring, or some appliances will trip the lower threshold GFP.
 
Ctarmigan,

There may be counter arguments to my thoughts here, but I don't think you should get hung up on where the GIFC unit is in the circuit. Over current devices (e.g., traditional circuit breakers, fuses) and GIFCs manage very different dangers in spite of the fact that they both break the circuit when they trip. GIFCs trip extremely quickly whenever it measures a small leakage of current somewhere in the circuit. Over current devices only trip at high amp loads (i.e., over 20 amps for a 20 amp breaker).

Typically folks recommend putting circuit breakers near the source. There are 2 reasons for this: one, if there is a full short before the breaker, the piece of wire btwn the source and the short is not protected from damage; two, if tripped the wire from breaker/fuse back the source is still energized (i.e,, can shock).

GIFCs don't protect against a short to that circuit's neutral and are more focused on the leakage of small currents (like if you are grounded and touch a live wire). Wire damage protection is not really an issue with GIFCs. So I don't think it really matters where the GIFC is in the circuit....if there is any leakage anywhere in that circuit, the GIFC is going to trip. The one advantage you might get from having the GIFC near the source is the other benefit of avoiding the wire leading from the source to the GIFC live after the GIFC has tripped. That's a very small benefit to get such that one should design the system based on just that.
 
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