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Old 06-14-2021, 11:24 AM   #1
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Engine Batteries and House Batteries

So we bought a 1988 Californian 48 CPMY late last year. It has four 8-D batteries (brand new when we took delivery), and the owner told us that Battery 1 was for port engine, Battery 2 for starboard, and 3 - 4 for house. I could quickly tell that was incorrect since 2 - 4 were wired in parallel. After some tracing, we found Battery 1 was indeed for port engine, and Batteries 2 - 4 were for Stbd engine AND house. I think the two alternators are the same size, even though the stbd engine has a larger capacity to charge.

We will be hauling again relatively soon to put in a bow thruster which will include a couple more small batteries up front. At that time, we will replace the stbd alternator with a higher amp model.

But, my question, concern, dilemma is one engine battery being combined with the house. While I like having more amp-hours for the house when we are on the hook, I don't want to have to start up the generator simply to get the starboard engine started, especially if we have to make a quick getaway.

My plan this week is to spend the night on the boat while in our slip but be disconnected from shore power and on battery only to see how things work out.

Any thoughts or strategies out there? It may be simpler for alternator connections, but is combining the house batteries to one engine ok?

(In our previous boat, it was one engine/one battery and two batteries for house. Plan B if the engine did not start was to hoist the sails since it was a sailboat. Plan B was never required to be implemented.)
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Old 06-14-2021, 12:22 PM   #2
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Quote:
Originally Posted by Mike H View Post
So we bought a 1988 Californian 48 CPMY late last year. It has four 8-D batteries (brand new when we took delivery), and the owner told us that Battery 1 was for port engine, Battery 2 for starboard, and 3 - 4 for house. I could quickly tell that was incorrect since 2 - 4 were wired in parallel. After some tracing, we found Battery 1 was indeed for port engine, and Batteries 2 - 4 were for Stbd engine AND house. I think the two alternators are the same size, even though the stbd engine has a larger capacity to charge.

We will be hauling again relatively soon to put in a bow thruster which will include a couple more small batteries up front. At that time, we will replace the stbd alternator with a higher amp model.

But, my question, concern, dilemma is one engine battery being combined with the house. While I like having more amp-hours for the house when we are on the hook, I don't want to have to start up the generator simply to get the starboard engine started, especially if we have to make a quick getaway.

My plan this week is to spend the night on the boat while in our slip but be disconnected from shore power and on battery only to see how things work out.

Any thoughts or strategies out there? It may be simpler for alternator connections, but is combining the house batteries to one engine ok?

(In our previous boat, it was one engine/one battery and two batteries for house. Plan B if the engine did not start was to hoist the sails since it was a sailboat. Plan B was never required to be implemented.)
You currently would be unable to start one engine if you inadvertently run down the house bank overnight

Faced with your options I would dedicate one battery to start both engines. I would parallel the other three batteries to be my house bank. I would have a "combiner" switch that allowed me to (temporarily) combine the start with the house bank in case your start battery ever quits. I would probably lkeep the existing alternators in place but have the lower capacity one charge the start battery so that the higher capacity one charges larger house bank.
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Old 06-14-2021, 12:44 PM   #3
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Originally Posted by Mike H View Post
So we bought a 1988 Californian 48 CPMY late last year. It has four 8-D batteries (brand new when we took delivery), and the owner told us that Battery 1 was for port engine, Battery 2 for starboard, and 3 - 4 for house. I could quickly tell that was incorrect since 2 - 4 were wired in parallel. After some tracing, we found Battery 1 was indeed for port engine, and Batteries 2 - 4 were for Stbd engine AND house. I think the two alternators are the same size, even though the stbd engine has a larger capacity to charge.

We will be hauling again relatively soon to put in a bow thruster which will include a couple more small batteries up front. At that time, we will replace the stbd alternator with a higher amp model.

But, my question, concern, dilemma is one engine battery being combined with the house. While I like having more amp-hours for the house when we are on the hook, I don't want to have to start up the generator simply to get the starboard engine started, especially if we have to make a quick getaway.

My plan this week is to spend the night on the boat while in our slip but be disconnected from shore power and on battery only to see how things work out.

Any thoughts or strategies out there? It may be simpler for alternator connections, but is combining the house batteries to one engine ok?

(In our previous boat, it was one engine/one battery and two batteries for house. Plan B if the engine did not start was to hoist the sails since it was a sailboat. Plan B was never required to be implemented.)
I would like to see your complete set up before I made a specific recommendation for you. In general start batteries are different than house batteries. Are all your batteries the same make or are two of the CCA and two of them deep cycle? There is no end to over kill in setting up batteries on a boat. I will give you a general low level arrangement. One 8D set to start both engines 3 deep cycles for house. You should be able to use switches to start either engine off of start or house. All alternators should go to house bank. A smart combiner or DC to DC charger should be used to charge the start battery from the house bank. Do not use a standard combiner, this will cook your start battery. Your battery charger should be wired to the house. If a multi bank charger you can hook it to both banks.

I prefer that generators have their own stand alone battery not connected to the rest of the system. This battery should be cycled out on a regular schedule this is your last line of defense when all else has failed.
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Old 06-14-2021, 02:26 PM   #4
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In addition, when you upgrade one of your alternators to charge a larger house set of batteries, also upgrade your regulator from the internal regulator you likely now have in each alternator, to a separate, 3 stage, "smart" regulator.

An automotive style regulator comes with most (all?) OEM alternators putting out 50 or lower amperage and will be adequate to keep the start battery up with a brief full output, easing off after just a few minutes at that level, but is totally inadequate for a large house battery bank connected to a more capable alternator putting out at least 100 amps at peak.

That high output alternator is designed to put out high amperage for as long as the battery bank takes to get out of the hole and up to a reasonable level, then to put out a more modest output to get to almost a full charge, then to ease off to a "Float" level, hence the "three stages".

Your charger should also put out at least 100 amps and have a 3 stage profile. Otherwise your running of a genset will not get you charged as fast as on your alternator after its upgrade.
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Old 06-14-2021, 03:49 PM   #5
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Turn off all battery disconnect switches then measure the voltage of each battery with a multimeter. You should quickly see which one is dead - if that is indeed the problem.
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You may have a bad battery and still have it show voltage. Go to a car parts store and buy a cheap battery load tester. It puts a load on the battery when testing it. I use it here all the time on our "farm" with all kinds of equipment and all kinds of batteries.
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Old 06-15-2021, 07:46 AM   #6
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I see no problem with the current set-up as long as there's a way to start either engine with the starting bank. A combiner or 1-2-Both switch would work.

If (when) you go to a higher capacity, externally regulated alternator for your house bank, make sure you upgrade any wiring that the extra current will traverse. Don't ask me how I know this.
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Old 06-15-2021, 09:35 AM   #7
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You may have a bad battery and still have it show voltage. Go to a car parts store and buy a cheap battery load tester. It puts a load on the battery when testing it. I use it here all the time on our "farm" with all kinds of equipment and all kinds of batteries.
Good advice! I had no idea they were so cheap. I remember them as massive things on trolleys in most mechanics' shops.

Just ordered one and am sure it will get usage.
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Old 06-18-2021, 10:43 AM   #8
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I would like to see your complete set up before I made a specific recommendation for you. In general start batteries are different than house batteries. Are all your batteries the same make or are two of the CCA and two of them deep cycle? There is no end to over kill in setting up batteries on a boat. I will give you a general low level arrangement. One 8D set to start both engines 3 deep cycles for house. You should be able to use switches to start either engine off of start or house. All alternators should go to house bank. A smart combiner or DC to DC charger should be used to charge the start battery from the house bank. Do not use a standard combiner, this will cook your start battery. Your battery charger should be wired to the house. If a multi bank charger you can hook it to both banks.

I prefer that generators have their own stand alone battery not connected to the rest of the system. This battery should be cycled out on a regular schedule this is your last line of defense when all else has failed.

This makes the most sense to me. I would summarize it this way.
1. One battery to start both engines
2. 3 batteries combined for the house.
3. All charging sources go to the house back.
4. DC to DC charger from the house to start battery. I am currently using both a Xantrex Echo Charger and a Balmar Duo Charger on my boat. There are likely newer/better options now.
5. Use combining switches to temporarily combine house and start battery if the start battery somehow gets drained.
6. Separate small start battery for the generator.

I use three DC-DC chargers on my boat. Echo Charger charges the engine start battery. Two Duo Chargers charge the thruster/windlass bank and the house bank.
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Old 06-18-2021, 11:58 AM   #9
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I see no problem with the current set-up as long as there's a way to start either engine with the starting bank. A combiner or 1-2-Both switch would work.

If (when) you go to a higher capacity, externally regulated alternator for your house bank, make sure you upgrade any wiring that the extra current will traverse. Don't ask me how I know this.
this is the KISS method and the one i like.
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Old 06-18-2021, 12:42 PM   #10
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Thanks to all for thoughts and observations. A number of ways to go, each with their own set of advantages and disadvantages. I will ponder up until we put the new thruster in....
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Old 06-19-2021, 01:06 PM   #11
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Mike, a first step to consider once you complete electrical load changes (like adding thruster,) is to complete a whole boat load survey, set down your new power consumption parameters based on how you'll use the boat, then look at current house capacity and determine if it will meet your needs or not and go from there.
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Old 06-21-2021, 10:17 AM   #12
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Mike,
I have a 1990 Californian 48 MY in Corpus Christi, Texas. I have the standard setup(at least according to the wire diagrams of the boat). That setup is 2 8Dís for Port and Generator, and 2 8Dís for Starboard and House. You didnít mention the Generator but Iím guessing itís connected up to the Port battery bank.

Do you have a Parallel Battery Switch at the helm? All Californians Iíve been on had it. I just spent a week debugging and testing mine to make sure it worked. It combines the banks at the push of the switch, nice feature.

Iím thinking of making the change to match your configuration. It would be very easy and no major wire changes and the parallel battery switch covers a drained Starboard /House bank without having to start the generator and charge a battery Bank.

My charging is factory setup, standard alternator, and one battery charger with 2 40amp legs, one for each bank.

I have a Victron Inverter/charger with a 120 amp charger connected to the Starboard/House Bank.

Iíve not done any load testing yet so let us know what you come up with.

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Old 06-25-2021, 05:55 PM   #13
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Check to make sure you don't have a Parallel Switch somewhere in the circuit. Get thoroughly familiar with how these various batts are wired and switched before making changes. A quick electrical walk through by an ABYC certified electrician does not need to cost a lot of money, but will save you a lot of figuring out work.
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Old 06-25-2021, 07:42 PM   #14
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I agree with Tiltrider!
Also, a so called "combination" start/house battery is not a very good battery for house use, as it is not a true deep cycle battery. That is another reason to separate house from start, but have a combining switch for emergency starts if the start battery were to fail.
Set it up right once, and then gain the advantages for years to come. You will need to know your average energy needs (actual consumption) to ensure that your house bank is adequate in size. Drawing the bank down below 50% regularly will shorten expected battery life, adding to overall costs to operate.
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Old 06-26-2021, 05:42 AM   #15
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Also, a so called "combination" start/house battery is not a very good battery for house use, as it is not a true deep cycle battery.
That is true for FLA battys but doesn't hold for AGMs.
At least East Penn, Duracell and others...
EP confirmed that their AGM GCs and GP31s perform equally well for start and deep cycle applications. If you look they spec both AHs and CCA on their AGMs. That provides a bit of flexibility when deciding / designing banks to fit available space.
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Old 06-26-2021, 09:18 AM   #16
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Three things I wouldn’t tie to the house bank except in an emergency (switch) or routinely tied to anything else.
Engine start
Electronics
Thrusters.
High draw with voltage drop from thrusters or engine start can cause your electronics to reboot. Dead cell in your house bank can cause the others to not work. I’m ok with having cameras on the electronics circuit. House should be house except in extraordinary circumstances. FLA, AGM, C or Li doesn’t matter.
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Old 06-26-2021, 10:09 AM   #17
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Three things I wouldnít tie to the house bank except in an emergency (switch) or routinely tied to anything else.
Engine start
Electronics
Thrusters.
High draw with voltage drop from thrusters or engine start can cause your electronics to reboot. Dead cell in your house bank can cause the others to not work. Iím ok with having cameras on the electronics circuit. House should be house except in extraordinary circumstances. FLA, AGM, C or Li doesnít matter.
Are you proposing 3 banks or more?
Start / thruster
House
Electronics
Gen start?

Mainship installed a lot of combo house / start batty banks but I moved my start to a separate start / thruster bank for exactly the reason you stated... electronics occasionally didn't like the V drop at start. I dont see the need for an additional electronics bank separate from house.
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Old 06-26-2021, 11:20 AM   #18
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Agree thrusters aren’t used except when engine is running. Agree either AGM, carbon or lithium can serve as both start and house. Have seen multiple ways to skin this cat and as long as it works that’s fine. Even have seen two separate “house” banks allowing mix and match. Given a larger bank will have less voltage drop for a given current draw if using carbon or Li which will tolerate high draw and not being at 100% SOC for long periods of time having sudden high draws on one bank and the rest on the other can work as well. Personally as stated with Pb chemistry like a battery for electronics, another for each engine start and a battery for thrusters. The big bank is house. Guest switches to allow backup. Have had balmar duo fail. Glad there are better choices now. That’s the other variable. What kind of chemistry? How big a bank?
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Old 06-26-2021, 11:43 AM   #19
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Ok, I just went through this on my 1991 Californian 55. It had your setup. 8D to start the port engine and the genset. 3 8Ds for house and stb start. A large combiner on the back wall of the engine room. All were start battery types. A defective Xantrex inverter killed all those batteries in only 2.5 years. So, replaced the start bank with two 8D start batteries but they only start the generator and the port engine. I know overkill in a way but I bought the batteries before I knew everything. I replaced the other two 8Ds with 6 Trojan L16s. They are just slightly larger and still fit crammed into the battery location, just taller. They start the stb engine and are the house bank. I put in a Victron 120 amp charger set to lead acid for the house bank L16s. I replaced another old non functioning three leg charger with a new Victron 30 amp to keep the start batts up, also feeds the house, and a separate genset start battery (I have two generators). Genset 1 charges house and start batteries. Genset 2 charges house and start batteries and its own start battery. Separately I installed a Sidepower bow thruster with a separate 24v charger under the seat in the dinette charging two group 31s. I think I'm in a good place.
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Old 06-26-2021, 04:53 PM   #20
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Iíve never owned a twin engine boat. Is it common to use an 8D batter to start each engine? That seems overkill, but again, Iíve never had twins.

Does anyone use a single battery to start both engines? The extra Ahs and weight could be put into the house bank or a dedicated thruster bank.

I have an 8D as a start battery only because that what what on the boat when I bought it. When I need to replace, Iíll use a smaller battery. All it has to do is start an engine, which is pretty easy on my 5.9 QSB. If I recall, when Dodge first put the 5.9L Cummins in their trucks they used a single group 27 battery.

A few of those Dodge truck owners ran into problems with cold cranking. Understandable if they are starting the truck in extremely cold weather, driving a few miles with all the accessories on, and stopping. Sometimes they would do this many times in a day.

Most of our boats donít do that. We start the engines in relatively warm weather after the batteries have been fully charged. Accessories arenít run off the start battery. Once started, the engines often run for hours before being shut down, giving the charging systems plenty of time to top them up.

If a diesel truck can get by on a single group 27 battery, being able to do multiple cold weather starts while running all kinds of accessories, our pampered diesels certainly should be able to.

An 8D has about 2x the CCA and 2X the weight of one Grp27. I would think that a single 8D could easily start twins, particularly if once the first engine is started, the alternator is starting to put amps back into the battery.

Am I wrong?
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