Easy Ac/Dc

Easy Ac/Dc serves as a forum for the discussion of boat wiring concepts, products and issues - many of which are generated by reader’s questions.

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Hello Kevin,

I purchased a Guest 2611A two bank charger with two independent ground wires. Since I have a battery selector switch, I have a jumper between the battery ground terminals.

Will the charger work with this setup, i.e. can the charger ground leads serve as a common ground?

Thanks very much,

Steve

Steve,

You can combine the independent grounds on all Guest multi-output chargers if you have a 12 volt system.

Kevin

Hey Kevin,

I have a bass boat (22’ Nitro) with what I believe is a typical battery setup; two batteries (24V) for the trolling motor and one battery (“cranking”) for everything else. “Everything else” would be depth finders (2), GPS, radio, live wells (2) and bilge pumps.

I have a two-bank onboard charger for the two trolling motor batteries. The cranking battery is charged by the engine’s alternator.

1. If the above setup isn’t the “right” way to do it, what is?
2. If the cranking battery draws down too low to crank the motor, I would like a “clean” way to utilize the trolling batteries for temporary cranking. In other words, I don’t want to break out the jumper cables.

Thank You,

Brian

Brian,

You have your system wired correctly.

The simplest way to use one of your trolling motor batteries for emergency starting would be to install an On/Off battery switch between the positive posts of your engine battery and your #1 trolling motor battery (connected with 2awg battery cable). You would also need to connect a 2awg ground wire between the negative of your engine battery and your #1 trolling motor battery. Any 12 volt items on your boat that are connected to the trolling motor batteries need to be connected to your #1 trolling motor batteries.

During normal operation, leave the battery switch in the OFF position. During emergency starting, turn the switch to the ON position.a

Hope this helps,

Kevin

Hello Kevin,

I purchased a Guest 2611A two bank charger with two independent ground wires.

Since I have a battery selector switch, I have a jumper between the battery ground terminals. Will the charger work with this setup, i.e. can the charger ground leads serve as a common ground?

Thanks very much,

Steve

Steve,

You can combine the independent grounds on all Guest multi-output chargers if you have a 12 volt system.

Kevin

Kevin,

First off, Happy Holidays!

I’ve been doing some wiring on my dad’s boat. Yesterday he wanted an extra power outlet so he can use his portable cell phone charger while at sea.

I had the outlet mounted in place and when I connected the second lead, there was a tiny spark and now nothing lights up and the boat won’t start!

I was wiring the outlet in series with all the gauges; they turn on when the key is turned.

I know it’s not the battery because the stereo system works and is still loud. (I wired that directly from the battery using a toggle switch). I’m so lost! There are 2 fuses by the battery and both are good.

Help!

-Jay

Jay,

It sounds like you blew a fuse or tripped a circuit breaker in the ignition circuit on your Dad’s boat. This should be a fairly easy DC boat wiring problem to troubleshoot.

If the boat was built using standard boat wiring colors, the input to the ignition switch should be a red/purple wire. Trace this wire back to a fuse panel or circuit breaker near the ignition key. You should find a blown fuse or breaker with a rating of around 15 amps.

If you cannot find the tripped circuit protection, please give me more info in the boat (Make/Model/Year/Engine) and I can be more specific.

Hope this helps,

Kevin

Kevin,

I removed two old batteries from a boat I just purchased. When I put the wires back on to the new batteries I tried to start the motor and the post blew out and caught fire.

I freaked for a moment, but then decided to try again on the other battery after removing the ground wire that connected them together and putting the selector to the only battery that worked. Well, that battery’s post melted and now I’m just aggravated.

Most of the wires I’m looking at are black or red, indicating to me ground and hot wires. So I’m pretty sure I’ve got them set up to their respective posts.

If I wanted to make certain how do I test the wire to see if it needs to run to the positive or negative post.

Thanks,

David

David,

It sounds like your DC battery system has a terrible short.

I would guess that the starter/starter/battery cable has something wrong. The battery post burns up because it is the highest resistance connection in the circuit.

When you are looking for the short, keep the following in mind:

Small accessory wires burn before battery posts

• Fault in accessory wire or accessory
• Proper fusing will eliminate

Battery posts burn before battery cables

• Fault in engine starter or starter cables
• Proper fusing is not practical

Most smaller current circuits have circuit protection (fuses or breakers) that would trip before burning the post off. These should be as close as possible to the battery.

If you cannot find your wiring short after inspecting the starter wiring, I would do the following:

1. Run all of your grounds to a ground buss (engine and boat systems).
2. Connect two 2awg black ground wires on your ground buss and run one to each of your batteries.
3. Connect your DC positive leads to your battery switch.
4. Connect the switched items to the Common post on battery switch and emergency items (bilge pump, stereo memory, horn) to Bat 1 and Bat 2 on the back of your switch. These items should all have fuses or breakers near - within 7″ - of the switch.
5. Connect two 2awg red positive wires from Bat 1 and Bat 2 of your switch to each battery.

For future connections, your boat wiring system will now have only one black and one red from each battery.

Happy Holidays,

Kevin

Hi Kevin,

Just bought my first boat, a 1999 bowrider with 3.0 Mercruiser. The boat came with standard battery for house and starting.

I’ve purchased a trolling motor, a Motorguide W55 12 volt with 50 amp reset breaker, and a modest stereo with a separate 230 watt bridged mono amp for the subwoofer. I’ve also purchased a Guest 10 amp dual battery charger, Guest A/B/both switch, and Ed Sherman’s book, Powerboater’s Guide to Electrical Systems, which I’m currently about a third of the way through.

My plan was to keep the original starting/house battery (Bat 1) isolated, i.e., as its own separate system so as to avoid draining the starting battery by running the stereo or trolling motor. I would then add a second (Bat 2) and third battery (Bat3) only for the audio and trolling motor…

I decided to purchase the two additional group 27 batteries. connecting the “trolling motor” battery (Bat 3) mounted in the bow, and the “audio” stern port side battery (Bat 2) via A/B/both switch - then use the Guest 10 amp charger to keep these two batteries charged… I figured if the trolling battery (Bat 3) was low, I could always switch and use the Audio battery (Bat 2) to troll or get to shore in case of emergency.

Then I found the info about marine electrical systems using voltage sensitive relays on Easy Ac/Dc

Now I’m confused and am reanalyzing what to do.

• Can I run two VSR’s from one alternator? VSR1 from Bat 1 to Bat 2 and VSR 2 from Bat 2 to Bat 3?
• Should I connect one VSR to (Bat 2 and Bat 3) combined in parallel for 12 volt output to audio and trolling?
• Use the two battery 10 amp Guest charger to maintain Bat 1 @ 5 amp, Bat 2 & Bat 3 @ 2.5 amp each? I would get three output Guest charger, but cannot afford it.
• Or, should I just simplify and just have a two battery system with one VSR - both being charged by the alternator via one VSR, e.g., Bat 1 for house and starting, and Bat 2 for audio and trolling motor?

I would love to have all three batteries relayed, so the alternator charges the entire system, then when voltage drop when using audio or trolling motor, each of the three batteries go independent…

Sorry if this is confusing… I’m new to this and just want a reliable system…

Thanks in advance!

Best regards!

Bryan

Bryan,

The main reason to add a BEP VSR, or Voltage Sensitive Relay, to your DC boat wiring system would be to isolate your starting battery from your house battery(s).

If this were my boat, I would…

1. Have Bat 1 connected to my engine
2. Connect Bat 2 and Bat 3 directly together to make one large house bank. (stereo, trolling motor, etc)
3. Use a VSR between Bat 1 and large battery bank 2
4. Connect one leg of the charger to battery 1 and the other leg to battery bank 2
5. Use an ON/OFF switch to for each circuit to provide a master disconnect.

It sounds as if you may have some of these components already. If not, my friends at EzAcDc have this setup as a complete battery management kit that even includes the battery boxes.

Hope this helps,

Kevin

Thanks Kevin,

That makes a lot of sense… I’ll order this kit ASAP.

What gauge cable should I use to link Bat 2 and Bat 3 together?

And, I only will require one master switch? Or one for Bat 1 and one for Bat 2 / Bat 3 bank?

Thanks again!

Happy holidays!

Bryan

Hi Bryan,

According to their website, the marine battery management system on EzAcDc includes a dual pole on/off switch. You can use this switch as your master on/off for both your engine start and your house battery bank.

I would use 2AWG cable to connect battery 2 and battery 3.

Glad I could help,

Kevin

Hello

I am connecting a diesel generator which is a new replacement for an existing generator.

First, I installed a new breaker panel - the old one was shot - with the appropriately sized double-pole breaker (the generator is 120/240 volts AC hence needs a 2-pole breaker).

This breaker panel protects the wiring between itself and the main boat panel when the master switch is set to “generator” (instead of “shore”). It also protects against overload, that is, if the total loads running off the generator exceed the breaker rating, it will blow.

The breaker’s amp rating is less than that of the wires it’s protecting and, also, just a little higher than the generator’s rating (so it won’t blow for momentary surges such as motor startups). So, it functions essentially the way a main house breaker does (the main service panel located right after the meter in a house).

My question is this: the ABYC (and other, I think) standards state that the maximum length of wire from a generator to its breakers must not exceed 7″ or 40″ if the wires are encased. Because of physical limitations, I needed to place the breaker panel about 6′ away (length of the wires) from the generator. So, do I need to provide additional protective devices closer to the generator to protect the AC output wires between the generator and the “service panel”?

I was thinking of putting a set of fuses, rated higher than the service breaker but less than the wires’ rating, right at the generator. I could do this because the fuses would take up less space than the breaker panel. Should I do this ? My impression is that regardless of the rules, this is not often done even when the distance exceeds the 40″.

To explain further, the sole purpose of these fuses would be to protect the relatively short run (6′) of wire from the generator to the breaker panel.

In the case of an overload/short, etc in a device running from generator power, for example an air conditioner, the breaker on the boat’s main panel for the specific device’s circuit should blow first, as normal. In the case of a cumulative load where no individual circuit is overloaded but the total load exceeds the generator’s capacity, the breaker in the panel I installed would blow. This would also occur if there were a short in the wire runs between the boat main panel and the generator panel I installed. If there were a short in the wires between the generator and the breaker I installed, the fuse(s) would blow.

This is really a similar situation where in many boats, at least older ones, with 12 V d.c. systems. There is no fuse/breaker at the battery, There is often a fairly long run of wire from the hosue battery to the boat’s main panel, and, should there be a short, etc. in that wire, there would be no protection.

Thank you

Ken

Ken,

If your generator does not have output breakers on it, it is probably self limiting.

Per the exception on ABYC E-11.7.3: “Self limiting generators, whose maximum overload current does not exceed 120 percent of its rated current output, do not require additional external overcurrent protection.”

Check into this before you start adding un-necessary breakers.

Kevin

Kevin,

I was wondering if you could help me with a question about charging two 12 volt batteries hooked up in series with a 2 bank charger.

Why is it that you don’t have to unhook the jumper wire that is going from the positive of one battery to the negative of the other? Isn’t that jumper creating a short when you are charging with the 2 bank charger?

Thank you for your time,

Ryan

Ryan,

There are two types of chargers used for DC battery management on boats.

Type 1 - Common Ground

All ground leads are internally or externally wired together.

These chargers are most commonly found on larger boats. They have several 12 volts systems with separate batteries. All of the grounds on the boat are wired together.

Type 2 - Independent ground

All ground leads are separate and can be wired together by the end user.

These chargers can be used in a Type 1 application, but can also be used in a 12/24/36 volt system. The charger doesn’t care how you connect the grounds. If there is a battery connected between the negative and positive output of the charger, it will charge the battery.

Hope this helps,

Kevin

Hello Kevin;

I just read about the voltage sensitive relay and it sounds great.

I have a 35’ twin outboard boat with a generator, shore power, 4 batteries and 3 manual switches.

I would like to add an on-board charger and VSR. Will I need more than one VSR? I would also like to be able to monitor the condition of my batteries at the helm.

Please advise.
Regards,

Gary

Gary,

The BEP Voltage Sensitive Relay, aka VSR, is a great product for DC boat wiring and battery management.

Depending on how many batteries you would like to combine, you would need as many as three VSRs for your system. You could also use the Emergency Paralleling VSR in your system. This would give you all of the benefits of the standard VSR with the addition of an Emergency override function.

• VSR 1 would go between your Port Engine Battery and your House Battery.



• VSR 2 would go between your Stbd Engine Battery and your House Battery.
• VSR 3 would go between your Generator Battery and your House Battery.

If this were my boat, I would use the Emergency Paralleling VSRs for VSR 1 and VSR 2 and would have a push button at the helm to trigger the paralleling.

VSR 3 is not as important as VSR 1 and 2. It will just include the Generator battery when your outboard alternators are charging the system. It will also allow charging of all 4 batteries when the generator alternator is running.

I would use a 3 bank charger like the Guest 2632 connecting the 20 amp leg to your House Battery and the 5 AMP legs to your Engine batteries.

During initial charging, the house battery voltage will probably be the lowest. The large leg will bring that battery voltage up faster. The 5 AMP legs are more for maintenance on the Engine Batteries. These batteries should be closer to fully charged. There should be no load on the generator battery and no need to start the generator when connected to shore power. Once all voltages are high enough, all 3 VSRs will close and all 3 legs of the charger will be charging the 4 battery system.

There are several systems available for battery management and monitoring. I like the BEP Contour System. This unit will monitor 3 batteries. Just like the battery charger, I would be most concerned with monitoring the Engine and House batteries.

Hope this helps,

Kevin