The Official Dual Battery Thread

[bturner2]

This is going back a bit in my memory bank... but maybe it will spark some conversation. The load that could be "Parasitic" would be better better managed with a switch externally to the kit IMO. I've used the BS configuration as described in their manual and have never had trouble.

Best,
D2

Same here. I don't mess with what the EEs at a company that designs these and systems for very large installations recommend.

[D2Dominator]

Getting ready to add a 2nd battery using the Blue Sea add a battery kit. In reading through the thread it appears to eliminate any draw from the ACR it should be wired to the load side of the switch. Sorry about the bad editing but it is as simple as wiring directly to the load post on the switch as shown in blue so both the 1 and 2 load side posts will have 2 wires attached to them?

This is going back a bit in my memory bank... but maybe it will spark some conversation. The load that could be "Parasitic" would be better better managed with a switch externally to the kit IMO. I've used the BS configuration as described in their manual and have never had trouble.

Best,
D2

[Footin]

In a standard factory MC set up, does anyone know which battery is the starting and which one is the house battery? I have one long ways (closest to the opening of the observer seat and one side ways behind it.

I could play around with a volt meter and figure it out, just asking before I do that.

The last person who replaced the batteries put in two deep cycles so I cant tell that way either.

[jj91]

Getting ready to add a 2nd battery using the Blue Sea add a battery kit. In reading through the thread it appears to eliminate any draw from the ACR it should be wired to the load side of the switch. Sorry about the bad editing but it is as simple as wiring directly to the load post on the switch as shown in blue so both the 1 and 2 load side posts will have 2 wires attached to them?

[D2Dominator]

This is a follow up for my 2002 Xstar (205v):

Charging lead (orange) runs from the alternator to the starter. The orange lead is combined with a red lead in a single 3/8 ring terminal: this should be 5/16.

The red lead feeds the 50amp engine breaker.

The alternator ground terminates at the starboard 3/8 lug forward engine lug.

2awg power cable runs from the starter to the battery switch along side a 2awg ground cable that terminates at the port 3/8 engine lug.

House electric from under dash by way of 2 6awg cables that travel behind the kick panel, through the bilge and into the batter compartment under the passenger observer seat.

I’m going to replace the charging cable and alternator ground with appropriately sized cable and ring ends. The 3/8 lugs are grossly oversized for the alternator and starter bolts.

I’m going to leave the engine breaker attached directly to the starter, and connect the amps, radio, and dash fuse panel to the house battery. This should be a simple method of isolating the house and engine... I’m going to use the blue seas ACR.

My factory setup had the battery’s run in parallel, with all the grounds terminating at one of the battery’s 5/16 ground post, and the red leads attached to the PERKO switch. I’ve installed a 4 x 3/8 studded ground bus bar and run appropriate cables and lugs to the batteries, house bus bar, amps, and engine block.

Next step is to install the add a battery kit, but the system is already cleaner... I’m surprised MC installed lugs that are so mismatched in size. The engine ground was an oval after 20 years!

Hope this specificity helps someone.


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[D2Dominator]

Isolate the house battery through the switch. Don't worry about re-wiring the starter on a stand alone circuit. Keep it simple.

If you want to have the one dedicated circuit for starting, put everything else on the accessory battery and the ignition start and bilge pump on the start battery. Use the switch/relay for the isolation. When you turn the engine off, the relay fails open and you have now isolated the start battery from the circuit and it all be there for starting, where all else is on the accessory battery with no concern of running down the start battery. When you fire the engine, the relay fails closed and you can charge both banks. No need to go beyond the intended purpose of a dual position switch and the relay. As long as the relay is wired properly on the ignition switch, you're good.

I think your wiring diagram above is correct.

.

100% agree on your logic. Assuming my wiring order is correct, I’d have to run a wire direct from the alternator to the starter, and one from house back to the breaker... not challenging by any means.

As long as the 2awg cable from the starter is the only thing connected to the starter battery, I should be fine as it will be isolated. I know the charging circuit won’t be “ideal”, but I have such a small audio system it should be fine...

I’ll audit the circuit later today as I want to hunt down and polish the grounds...

D2


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[waterlogged882]

I can check again this morning.

I’ve got a 205v xstar... Might be wrong.

If not wired as I said, there should be cable from the circuit breaker to the battery right?
Because I’m sure there isn’t.

No problem with running a 8g cable from the house battery to the 50amp house breaker at the engine?

D2


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Isolate the house battery through the switch. Don't worry about re-wiring the starter on a stand alone circuit. Keep it simple.

If you want to have the one dedicated circuit for starting, put everything else on the accessory battery and the ignition start and bilge pump on the start battery. Use the switch/relay for the isolation. When you turn the engine off, the relay fails open and you have now isolated the start battery from the circuit and it all be there for starting, where all else is on the accessory battery with no concern of running down the start battery. When you fire the engine, the relay fails closed and you can charge both banks. No need to go beyond the intended purpose of a dual position switch and the relay. As long as the relay is wired properly on the ignition switch, you're good.

I think your wiring diagram above is correct.

.

[D2Dominator]

I can check again this morning.

I’ve got a 205v xstar... Might be wrong.

If not wired as I said, there should be cable from the circuit breaker to the battery right?
Because I’m sure there isn’t.

No problem with running a 8g cable from the house battery to the 50amp house breaker at the engine?

D2


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[MLA]

Alternator --> Circuit Breaker(dash fuse panel) --Starter --> Back to the battery

Never seen a boat wired like this, and ive worked on hundreds and hundreds of boats.

Most boats I see, the alternator is wired to the starter.

[D2Dominator]

ALLLLLLRIGHT...

Read this thread for the last few years... Great work All.

Here is a question:
For those of us who's boats have a charging circuit that flows as such:
Alternator --> Circuit Breaker(dash fuse panel) --Starter --> Back to the battery

If we want to isolate the starter (as I do), any problem with running a charging cable from the alt to the starter directly bypassing the house breaker. I'd then run a 6AWG cable from the house battery back to the breaker to accommodate the dash fuse panel.

The way I see it, it is the only way to truly isolate the starter from the house bank. The other option would be to run a cable from the breaker junction, to the house battery.

Thoughts?

D2

[landshark]

Dual Battery Success

Just want to thank the group and Diesel in particular. I recently installed the dual battery system he laid out on the first page of this thread. Even without the diagram picture, the directions were easy to follow. It's so nice to not have to worry about battery switches or anything more complicated than the original setup, and now I have the extra peace of mind of having a second, charged, battery on board. All for less than $200 including the second batt.

If anyone needs to see the diagram, let me know, as I drew it up based on the original post.

happy boating all!

[landshark]

OK, I know this is a dual battery thread but I'm trying to solve a single battery problem without having to add a second battery. 2009 Prostar 214V with the following BUSS switch (see pic). It looks like the stater leads are direct from the battery and the two amplifier leads were also run direct from the battery (previous owners). The final lead off the battery post connects to this BUSS switch. Am I correct in assuming everything except the starter and amps can be killed if this BUSS is switched "off" or am I missing something.

I don't have any experience with that switch, but what you are saying makes logical sense to me.

You could test your theory by turning the switch off and seeing what works, and what doesn't.

[mcnorthwest]

Single battery question

OK, I know this is a dual battery thread but I'm trying to solve a single battery problem without having to add a second battery. 2009 Prostar 214V with the following BUSS switch (see pic). It looks like the stater leads are direct from the battery and the two amplifier leads were also run direct from the battery (previous owners). The final lead off the battery post connects to this BUSS switch. Am I correct in assuming everything except the starter and amps can be killed if this BUSS is switched "off" or am I missing something.

[waterlogged882]

Batteries are in parallel. Negative's are connected and positives are split by a 40amp thermal circuit breaker. Starter battery is on the battery/load terminal, house is on the accessory terminal. Boat was configured like this when I bought it in 2012 and I figured it to be factory as it was the same way my 2005 X9 was set up.
Diagnosing the circuit breaker, I found that it isn't working as designed and is fixed in the open position.
Replacing the thermal circuit breaker is the cure. New breaker installed I have 14.4 volts on each battery with the engine running. Thank you for the help diagnosing this problem.

Makes sense and I think we were seeing the same issue in a slightly different manner.

Glad you got it resolved.

Best of the summer for you and family.

.

[neil.anderson63]

I have to ask...why a breaker between the batteries? A circuit breaker I presume? I don't see that as beneficial for the intent of your setup.

From what I understand, it seems you do not have the batteries in parallel for charging and also do not have an isolation relay to separate the batteries when engine is off. The breaker does nothing for you in this scenario.

You jumped the two batteries together for a start which the jumper was acting as the DBS, thus combining the batteries.

If you do not have an isolation relay (open and close on ignition switch command) you're not isolating the start battery from the accessory battery when the ignition switch is off [and not charging (failed closed) them when the ignition switch is on run]. The ignition switch off position triggers the relay to fail open thus isolating the batteries...but you do not have this component.

If this doesn't make sense, I have misunderstood the description of your setup.

.

Batteries are in parallel. Negative's are connected and positives are split by a 40amp thermal circuit breaker. Starter battery is on the battery/load terminal, house is on the accessory terminal. Boat was configured like this when I bought it in 2012 and I figured it to be factory as it was the same way my 2005 X9 was set up.
Diagnosing the circuit breaker, I found that it isn't working as designed and is fixed in the open position.
Replacing the thermal circuit breaker is the cure. New breaker installed I have 14.4 volts on each battery with the engine running. Thank you for the help diagnosing this problem.