The Official Dual Battery Thread

[bturner2]

Blue Seas has no clue what you're installing their product into or how far the distance will be from the engines to their gear. 2 AWG is some serious stuff and is going to be difficult to work with. I would agree with MLA here.

If you want to get a second opinion without calling an electrician, go to the MC dealer and look at their installation. See any 2 AWG? What size breakers are they using? Don't forget breakers are used to protect the circuit. Set the breaker too high and everything will fry and the breaker will either not trip or trip way too late.

[BellyUpFish]

The gauge of the cable is going to be determined by the potential load its going to carry, and the distance of of the cable. This can very boat to boat.

6ga would be adequate for connecting the ACR to the switch, unless one chose to mount it 30ft away. 6ga would be substandard for any engine starter load, unless it was a medium outboard engine.

I plan on leaving the factory wiring for engine starting load.

I don't know if my plan is sound, but I'm thinking about running the factory ground cable to a bus bar, near the factory battery location, and then adding a second battery..

Essentially all I want to change is to put my stereo onto it's own battery.

[MLA]

I plan on leaving the factory wiring for engine starting load.

Understood, but you are adding a 2nd battery that will connect to the new switch and loads will draw from it, so that cable length need to be taken into account, as well as the loads. Also, the switch has a COMBINE position, so the house bank has the potential of seeing engine cranking loads, which can peak at 300A and be as much as 200A continuous.

If the boat does not currently have a main battery switch, then the main starter cable comes off the existing battery and relocated to the new switch. now you need a new cable from the switch to battery. So yes, somethings get reused, but there are a few new cables that need to be built.

Unless the batteries are wide apart from each other, I prefer to just connect the house ground right to the main battery's ground post.

[waterlogged882]

I plan on leaving the factory wiring for engine starting load.

That is the first thing I would replace for reliable system (in conjunction with your overall objective).

.

[bturner2]

This was my last installation. Like MLA stated, I also tied the grounds together.....

Notice the common ground terminal to the right of the right battery. In a perfect work no individual wires should attach to the battery. The exception (for me) would be a bilge pump but even that I would attach to the batter switch post. Wires attached to batter posts can get left off when reconnecting. A small number of large cables is more difficult (but not impossible if you try hard) to miss.

[BellyUpFish]

That is the first thing I would replace for reliable system (in conjunction with your overall objective).

.

I can definitely consider replacing them. They seem to be in good shape, so I didn't consider it.

[waterlogged882]

I can definitely consider replacing them. They seem to be in good shape, so I didn't consider it.

I understand your thoughts. However after 17 years in a semi-harsh environment, the wire can corrode or degrade beneath the sheathing. Been there. Your call but for peace of mind and a new baseline, I thus suggest the new wire. The 2AWG wire is no trouble for installation and handling. It fits in quite nicely.

I will say this; use tinned marine wire instead of readily available auto wiring.

I can recommend Genuinedealz dot com for your wiring needs. Get them to build your 2AWG or whatever you decide, with professional crimps and heat-shrink cover. Specify your hole diameter in each end of each wire as the hole sizes vary from hot and ground / battery and opposite end connections. They ship with USPS flat rate (very reasonable). It comes plug-and-play ready right out of the shipping box.

Best luck.

[BellyUpFish]

I understand your thoughts. However after 17 years in a semi-harsh environment, the wire can corrode or degrade beneath the sheathing. Been there. Your call but for peace of mind and a new baseline, I thus suggest the new wire. The 2AWG wire is no trouble for installation and handling. It fits in quite nicely.

I will say this; use tinned marine wire instead of readily available auto wiring.

I can recommend Genuinedealz dot com for your wiring needs. Get them to build your 2AWG or whatever you decide, with professional crimps and heat-shrink cover. Specify your hole diameter in each end of each wire as the hole sizes vary from hot and ground / battery and opposite end connections. They ship with USPS flat rate (very reasonable). It comes plug-and-play ready right out of the shipping box.

Best luck.

Thanks. I'll give it a look. I guess I'll go ahead and replace it.

[neil.anderson63]

2007 X2 - Head scratcher for me. Starter battery is charging, 14.4 volts. House battery isn't, 12.2 volts and will die on the water after a few ballast fill and empty when goofy and regular riders switch sides. Battery is good, takes a charge, load tests and holds. I don't have a VSR or a Perko DBS in my system, only a breaker that sits right between my batteries. The breaker hasn't ever tripped. When the battery died on the water I put them inline with a jumper cable and was able to empty my tanks to trailer home.
I think my only component that could be bad is the breaker. Do these breakers go bad?

[waterlogged882]

2007 X2 - Head scratcher for me. Starter battery is charging, 14.4 volts. House battery isn't, 12.2 volts and will die on the water after a few ballast fill and empty when goofy and regular riders switch sides. Battery is good, takes a charge, load tests and holds. I don't have a VSR or a Perko DBS in my system, only a breaker that sits right between my batteries. The breaker hasn't ever tripped. When the battery died on the water I put them inline with a jumper cable and was able to empty my tanks to trailer home.
I think my only component that could be bad is the breaker. Do these breakers go bad?

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.

.

[MLA]

2007 X2 - Head scratcher for me. Starter battery is charging, 14.4 volts. House battery isn't, 12.2 volts and will die on the water after a few ballast fill and empty when goofy and regular riders switch sides. Battery is good, takes a charge, load tests and holds. I don't have a VSR or a Perko DBS in my system, only a breaker that sits right between my batteries. The breaker hasn't ever tripped. When the battery died on the water I put them inline with a jumper cable and was able to empty my tanks to trailer home.
I think my only component that could be bad is the breaker. Do these breakers go bad?

Breaker will likely never trip, unless its like less then 5A rating.

Unless there is more to your setup then posted, I read its 2 batteries wired in parallel into one, with a random breaker between them.

You measured alternator voltage on one and static battery voltage on the other. If this was with a meter, then use that meter to find where the alternator voltage stops.

Yes, a breaker can fail.

[JimN]

2007 X2 - Head scratcher for me. Starter battery is charging, 14.4 volts. House battery isn't, 12.2 volts and will die on the water after a few ballast fill and empty when goofy and regular riders switch sides. Battery is good, takes a charge, load tests and holds. I don't have a VSR or a Perko DBS in my system, only a breaker that sits right between my batteries. The breaker hasn't ever tripped. When the battery died on the water I put them inline with a jumper cable and was able to empty my tanks to trailer home.
I think my only component that could be bad is the breaker. Do these breakers go bad?

Make sure the second battery is on the ‘Load’ side of the breaker and measure continuity across its poles witg nothing else attached- should read 0 Ohms. How are the cables attached? Lead lugs with the clamps tight or only slid on and wiggled? If it has wing nuts, make sure the cable ends are clean and measure voltage without the second battery connected WITH the engine running- if you don’t see the same at both batteries, fix that.

[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.

[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.

.

[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.