Boaters Guide to AC Electrical
Many seasoned boaters have an aversion to using AC Electrical around boats in marinas.
Water. Electricity. That’s a natural concern.
Marinco has been designing, building and supplying the best marine AC electrical products since 1972. Safety is always the first concern. And the best way to ensure safe shore power product usage is through training and education.
Marinco makes it easy to know how to use these products. They publish a great booklet entitled: “Boaters Guide to AC Electrical”, known around the marketplace as the “Shore Power Manual”. It’s the definitive resource when it comes to shore power. This guide drills out the mystery and concern, with straight-forward, easy-to-understand tips on AC Electrical.
You can order this booklet by visiting their website: http://www.marinco.com/view/96/guides
Editor’s Note: John Tinghitella formerly VP Sales / Marketing for the Marinco Electrical Group spent many years in the trenches of the marine electrical products market. He’s moved on and now runs the hottest negotiation training group in the business.
On-Board Charging
It started out promising to be a great day.
Gear is loaded. You’re at the boat launch or marina. Wife and kids are ready to go. And then…
…You turn the key…nothing happens. Dead battery. Now it’s now a lousy day.
We all have war stories of preparing for a great day of boating or fishing, only to get snagged by boat batteries that somehow died since the last boat use. No rocket science here. Know this: batteries lose 1% of their charge each day they are not used. Boats often times sit for long periods between uses. You can do the math.
There is a better way. If you have not embraced the concept of on-board charging, you need to. It’s simple … buy, install and use a marine-grade battery charger. The technology has come a long way. While the boat is either trailered and stored in your garage, driveway or wherever, you leave it plugged in. So instead of discharge between boat uses, your batteries are well maintained and healthy.
Today’s 3 stage chargers recognize when the battery is fully re-charged, and then go into “maintenance” or ”float” mode. That keeps it topped off…so when you’re ready to boat, the batteries are ready to crank.
The Guest range of on-board battery chargers are simply the most reliable, best performing and longest lasting products in marine electronics. Check ‘em out!
Editor’s Note: John Tinghitella formerly VP Sales / Marketing for the Marinco Electrical Group spent many years in the trenches of the marine electrical products market. He’s moved on and now runs the hottest negotiation training group in the business.
Best of both worlds — Guest Chargers + BEP VSR
The Guest range of Charge Pro Plus chargers combine reliable Guest charging with state of the art BEP voltage sensing. The benefit for the boater is simple…you can charge your batteries while on the water (DC to DC) as well as the normal AC route. The BEP VSR module is integrated into the marine electrical system and simply sends alternator current to where it’s needed most while you’re underway. Sort of like a charging traffic cop deciding where to send the juice. And it’s seemless to the user. You get to do what you should do…fish, boat and have fun.
Editor’s Note: John Tinghitella formerly VP Sales / Marketing for the Marinco Electrical Group spent many years in the trenches of the marine electrical products market. He’s moved on and now runs the hottest negotiation training group in the business.
Connecting two batteries with different capacities
Hi Kevin,
Many thanks for making this service available – reading the previous posts has been a real eye-opener.
I have what I think is a silly question, however I’d like to check:
I have two batteries, both lead-acid sealed 12 volt. One is a 70 amp/hour, which wasn’t up to the job of providing enough current
to turn the engine over in the mornings after sleeping over on the yacht. So, I went out and bought a 110 amp/hour which is.
I’d like to use both of these batteries – with the large capacity to run the boat systems and the smaller as a reserve / starter battery. The wiring to a main switch that allows Battery1/Battery2/neither /both is in place.
I think that I can simply connect the two batteries despite their different capacities, so that when ‘both’ is selected they will discharge together and/or charge together.
I believe that if one has a higher voltage than the other at the point of selecting ‘both’ then the higher will discharge to the lower until they are equal. I don’t believe that the fact they both have different maximum capacities will affect their use.
Am I right? Is there any drawback to connecting two batteries of different capacities?
Thanks!
Evan
Evan,
You are correct. You can certainly connect two batteries with different reserve capacities in parallel with your battery switch. 
You may want to consider modifying your boat wiring system by adding an emergency paralleling VSR like the one from BEP Marine instead of the battery switch.
This switch will automatically parallel the batteries when the engine alternator is charging the system. When the system is not charging and the voltage is below 12.6 volts, the circuit will open up. This device also offers an emergency paralleling feature that can be manually operated or remotely from a button.
Thank you for writing.
Kevin
Common ground with two alternators?
Kevin,
I am wanting to have two separate alternators, one to use for my existing power system and a second to use to run an inverter for my 120 volt system.
Do I tie the grounds from both of the alternators together? If I have two alternator/battery systems would these not have to be isolated from each other?
Thanks,
Freddy
Freddy,
Tie all you DC grounds together. The best practice on 12v boat wiring is to have a common ground. Keeping the positives isolated helps prevent the dead cranking battery problems associated with inverter use.
A great option to add would be an emergency parallel VSR like the one from BEP. This would allow you to crank your engine off of your inverter battery or run you inverter off of your engine battery in an emergency. Plus, if the paralleled voltage is too low, the built in timer will open the circuit in 5 minutes to prevent complete battery discharge.
I hope that this is helpful.
Kevin
Battery charger wiring configuration
Kevin,
I have a 3-Stage 20 Amp Battery Charger with 2 outputs, each producing 10 Amps from their respective red & black leads. It is designed to charge 2-12v batteries simultaneously, i.e., Ouput 1(10Amp) Output 2 (10 Amp).
I wish to connect the Charger to two 12V batteries that are connected in Parallel with AWG#8 tinned-copper stranded cable. Both 12V batteries are identical, GROUP 31 – Heavy Duty Marine Deep Cycle (Trolling Motor application), each with Reserve Capacity of 225 min.
QUESTIONS:
Which is the recommended way of connecting the charger to charge the Parallel batteries ? ….
Are any of the connections below, not acceptable?
- Using Charger Leads from both Output 1 and Output 2 – connect the RED and BLK leads to their respective terminals on PARALLEL batteries 1 & 2 ? …
- Using the Charger Leads from Output 1 (10 Amps) – connect the RED lead to POS of battery 1 and BLK lead to NEG of battery 1 ? …
- Using the Charger Leads from Output 1 (10 Amps) – connect the RED lead to POS of battery 1 and BLK lead to NEG of battery 2 ? …Also, using the two scenarios above …
- Can I use the unused Charger Leads from Output 2 (10 Amps) to double up on the leads from Output 1 (thus 20 Amps total output)? …
Brian
Brian,
Your battery charger will perform like 2 separate chargers. It is designed to charge two isolated batteries, two batteries in series, or two batteries in parallel.
All of your proposed battery charger connections would work except 2 and 2b. 2 and 2b would only be using 10 amps of the 20 amp capacity of your charger.
The best setup is 1. It is the least confusing and minimizes the risk higher resistance in the charger output wires.
Hope this helps,
Boat wiring diagram available?
Dear Kevin,
I just purchased a 1990 Thunder Craft bow rider. As far as I knew everything worked on the boat when I picked it up at my friend’s house – and he had shown me that all systems worked.
I took the boat out to local lake and submitted to a voluntary safety check. The boat passed with the
exception the navigation lights. They had worked before. I had cleaned and lubed all electric connections on the battery and the stern light with dielectric grease.
I guess that my question is do you know of a location of a boat wiring diagram with component locations for a 1990 Thunder Craft 1560 SE? Or, is there a fuse box in the boat that I just can’t find?
I have searched the web to try and find something I can use and the only thing I can find is info on a legal case against Thunder Craft from another company. I know the boat company isn’t around anymore because I can’t find anything on them.
Can you help?
Thank You,
Robert Thompson
Robert,
Boat wiring diagrams are rare for new boats and almost non-existent for older ones. Your best bet is trace each individual wire. This may be easier with a boat wiring color chart like the one that we have posted on Easy Ac/Dc.
If the boat was built to USCG standards, then there should be a fuse block or breaker panel near your helm switches. 
It is very possible that a previous owner did some creative wiring and removed some components.
If you absolutely don’t have a fuse block or breaker panel, you really need to add circuit protection for the individual circuits.
As for the navigation lights, since they have quit and all the wiring is intact, it is very possible that the nav/anc switch is malfunctioning. In the early 90s, builders used unsealed, inexpensive switches that were prone to corrosion. Most of these switches can be dis-assembled and cleaned up. Most can then be reassembled. But, some cannot!
Is the remaining wiring in decent shape or does it make sense to do some rewiring?
Let me know. I have some ideas.
Kevin
