Battery Configuration Help

Looking for some advice on how to wire batteries in a new configuration, that I am planning on installing.

We have a single engine Yanmar 370hp in a Mainship 390 with the current configuration

1 (2) way Battery switch Isolator (1,2 or both)

1 50 amp 2 bank Battery charger

1 8Kw Generator with it's own Grp 27 battery with on off switch isolator

2 Grp 31 Deep cycle starting batteries wired in series (Connected to Battery 1 on the Battery/Isolator switch)

1 8D House battery (also runs the bow thruster) (Connected to Battery 2 on the Battery/Isolator switch)

I would like to go to the following, but not sure how connect

2 Grp 31 Deep Cycle starting batteries wired in series and also have it run the Bow thruster (Only change is move the thruster to theses batteries) Connect to Battery 1 on the Battery/Isolator switch

Add 4 Trojan T 145 6 Volt batteries for the house.

My thought process is
I need to have 2 groups of 2 of the 6 volt wired in Parallel to give me 12 Volts,
and then do I wire these 2 banks in series, to give me 1 Bank,
or am I way off base,
hopefully I am making sense.
I want to basically pull out the 8D and replace with (4) 6volt, (Reason we do a lot of anchoring and would like to increase my battery capacity, before having to run the generator) Many thanks for any help

You have your parallel and series reversed. You parallel 12v group 31’s and series your 6v Trojans.

Parallel is connecting the positive to positive post and series is connecting a positive to the negative of another battery

Your thrusters will work best connected to starting batteries. Batteries are either designed to throw off a lot of amps quickly (start battery) or they are designed to last a long time feeding a more moderate amp demand (deep cycle). A deep cycle starting battery would be an oxymoron or truly the worst of two demands.

There has been a lot of discussion on how to achive optimum battery bank set ups. If you haven’t done a search, I would highly recommend it. You will be surprised by all the discussion and combinations for various reasons.

What you haven’t mentioned is the alternator.

In short, you connect the positive of a 6v battery to the negative of a different 6 v battery and now you have a 12v group. You then connect the un used positive post of each group to the other, same with the negative and you now have a 12v bank. There is a lot more to consider, this is just a very short answer.

I'd very strongly recommend, no, urge, you to get a copy of Calder's "Boat Owner's mechanical and electrical manual" and/or "The 12 volt Bible for Boats".

Invaluable for this and many other projects.

caltexflanc said:

I'd very strongly recommend, no, urge, you to get a copy of Calder's "Boat Owner's mechanical and electrical manual" and/or "The 12 volt Bible for Boats".

Invaluable for this and many other projects.

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This is probably the best advice that can be given on this thread.

living on 12 volts

I agree on Calders book, also add Living on 12 volts with ample power by David Smead.

I am installing as of today 5 8d AGMs as one main bank for everything. Really wanted to put in LiFePo3 Batteries, next time. I just installed 4-370watt solar, haven't connected controllers, Big alternater on hold due to bracket problems. But I think one bank of same batteries and age will be much easier to manage. 1250ah is a good start. My boats windlass and winch were wired to the house, just got rid of genset batt.and added a 5th batt. Wish I could get the 210 amp alternater in! Leaving for Abaccos Dec 1.

Cartouche, I think your idea is fine, other than mixing up series vs parrallel.

One thing I would suggest, is look to see how your alternator output is fed to the batteries. Also think about about your charging setup in general.

tiltrider1 said:

Your thrusters will work best connected to starting batteries. Batteries are either designed to throw off a lot of amps quickly (start battery) or they are designed to last a long time feeding a more moderate amp demand (deep cycle). A deep cycle starting battery would be an oxymoron or truly the worst of two demands.

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Untrue, but not arguing the point here.

"(Reason we do a lot of anchoring and would like to increase my battery capacity, before having to run the generator)"

Upgrading the house side of the battery bank is fine , but can be expensive.

Far easier to examine what is using juice , on the hook, and make changes in consumption.

What is running down the house bank while anchored?

Cartouche
Mainship used diode isolators in some years / models for both alternator and shore charger connection to multi banks.
Worth checking yours to understand what exists. There are many better alternatives.
I made some changes to my MS charging systems ans can provide a link to more info if desired.
I think you heading in the right direction but agree Calder and other threads here on TF worth investigating.
You might also engage a pro to design a system based on your usage even if you plan to do the mods.

Many thanks to all I will get the Nigel Calder book and will let hopefully ive me the insight I need, thanks also to Bacchus for the heads up re Mainship.

What I would do is as follows.


1. Starting batteries - wire the two Grp 31 start batteries in parallel (positive to positive and negative to negative).


2. Wire the 4 golf cart batteries as follows:
Pair-1 - wire in series Positive on batt 1 to negative on batt 2
Pair-2 - wire in series Positive on batt 1 to negative on batt 2
Wire the two pairs in parallel - Positive on batt-2 in in pair-1 to positive on batt-2 in pair-2 and negative on batt-1 in pair-1 to negative on batt-1 in pair-2.


3. Wire the output from the alternator DIRECTLY (no switch) to the positive on the start batteries. Connect negative on the start batteries to the engine block.


4. Connect positive on the start batteries to positive on the house bank via an automatic combiner relay (ACR). Choose the ACR based on the alternator rating (i.e., ACR should be rated for more amps than the alternator).


5. Connect negative on the house bank to the engine block.


This setup will give you two separate battery banks when the engine is off, but the combiner will connect them for charging when the engine is running. The direct connection from the alternator to the start bank means you do not have to remember to turn a switch on before starting the engine. The ACR will connect the two battery banks when the engine is running and disconnect them when the engine is off. So you never have to flip a switch to charge the house bank from the alternator.


Don't forget to fuse the positive side of the connection to the start bank close to the batteries.

Many thanks TDunn exactly what I was looking for

TDunn said:

What I would do is as follows.


1. Starting batteries - wire the two Grp 31 start batteries in parallel (positive to positive and negative to negative).


2. Wire the 4 golf cart batteries as follows:
Pair-1 - wire in series Positive on batt 1 to negative on batt 2
Pair-2 - wire in series Positive on batt 1 to negative on batt 2
Wire the two pairs in parallel - Positive on batt-2 in in pair-1 to positive on batt-2 in pair-2 and negative on batt-1 in pair-1 to negative on batt-1 in pair-2.


3. Wire the output from the alternator DIRECTLY (no switch) to the positive on the start batteries. Connect negative on the start batteries to the engine block.


4. Connect positive on the start batteries to positive on the house bank via an automatic combiner relay (ACR). Choose the ACR based on the alternator rating (i.e., ACR should be rated for more amps than the alternator).


5. Connect negative on the house bank to the engine block.


This setup will give you two separate battery banks when the engine is off, but the combiner will connect them for charging when the engine is running. The direct connection from the alternator to the start bank means you do not have to remember to turn a switch on before starting the engine. The ACR will connect the two battery banks when the engine is running and disconnect them when the engine is off. So you never have to flip a switch to charge the house bank from the alternator.


Don't forget to fuse the positive side of the connection to the start bank close to the batteries.

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Very good advice but I'd recommend one change...

Send the alternator charge directly to the house bank since its charging needs will be greater than the start battery. Use the ACR connection to share this charge with the start battery after the house has exceeded 13V.

The start battery bank of 2 G31s will be more than enough for your start needs and should be ample for your bow thruster. I start both of my Perkins engines from one G31 start battery without issue but I don't have a bow thruster. (My windlass is connected to my start battery.)

Any battery labeled as a combo deep cycle-start battery is probably neither a very good start battery nor a very good deep cycle battery. It's best to buy batteries that are specifically designed, marketed and sold for the sole intended purpose, start or deep cycle. But working with what you have is often the most economical until you need to replace the batts, then a better battery can be purchased. Just food for thought for the next time you face purchasing batteries.

FlyWright said:

Any battery labeled as a combo deep cycle-start battery is probably neither a very good start battery nor a very good deep cycle battery. It's best to buy batteries that are specifically designed, marketed and sold for the sole intended purpose, start or deep cycle.

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True for 99.99% of mass market / automotive marketing channels.

Odyssey AGM is a major exception, and Northstar and Lifeline, all share advanced TPPL technology that gives you the best of both worlds.

At a price of course.

A large enough even FLA deep cycling bank can handle high discharge rates just fine too, much better value than AGM, especially in $/AH/year.

My boat came equipped with a lead acid 8D deep cycle for starting. Worked fine for many years before I converted. I'm not saying it's not possible as it clearly is...only that best practices normally recommend function-specific batteries for normal use.

Yes but for the use cases that are both high-current **and** require deep cycling, a Starter style batt will not have good longevity.

john61ct said:

Yes but for the use cases that are both high-current **and** require deep cycling, a Starter style batt will not have good longevity.

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I think you just like to argue. No one here is advocating using a start battery for deep cycle use.

Please tell us, john21ct, what is your experience? Have you ever crimped a connector? Do you have a boat? Have you installed marine electrical systems? Do you have formal training in electrical systems?

Some folks pass along electrical advice in online forums without any experience or true understanding. You post a lot about electrics but often it's the good work of others that has been discombobulated. Please tell us your experience and training so we can know that your words can be trusted.

Cartouche
One other consideration.
If you have a thruster I would check w whatever ACR mfg you choose and send them a schematic. When I rewired my alt & shore charger I added a ACR but was cautioned against using some due to the potential of it seeing hi amps when connected and the thruster was activated.
Again if interested I can provide a link to my schematics pics & ACRs considered.

FlyWright said:

Very good advice but I'd recommend one change...



Send the alternator charge directly to the house bank since its charging needs will be greater than the start battery. Use the ACR connection to share this charge with the start battery after the house has exceeded 13V.

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I was thinking the same thing. Not sure however if it will make a big difference if an ACR is used. I’m assuming that the alternators would produce voltages well over the 13v threshold but I could be wrong.

It would take more wiring and possibly some too-long wire runs, but I would even look at driving the thrusters off the house bank and charging the start battery with an Echo-charger.

Many people do not realize that some of their high-current loads are depleting SoC significantly more than cranking duty.

And some believe that true deep-cycling batts are inherently inferior to Starter batts in driving winches, windlasses, bowthrusters, high-gph watermakers etc

Therefore, not arguing for S&G, just correcting an overly general statement.

It is false to assert that you need to choose **either / or**, that true dual-use models are not available from trustworthy makers.

I was not in any way attacking you personally.

dhays said:

It would take more wiring and possibly some too-long wire runs, but I would even look at driving the thrusters off the house bank and charging the start battery with an Echo-charger.

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Yes whenever possible, putting all the big-AH eggs in one basket is best.

Cranking requirements are so minor, a low-amp combiner or Echo Charger is just fine.

Sharing the higher demand loads with cranking requires a much more robust Starter, higher amp charging thus bigger VSR/ACR, and loses the many Peukert advantages of a bigger Main bank. "house"

FlyWright said:

Please tell us, john21ct, what is your experience? Have you ever crimped a connector? Do you have a boat? Have you installed marine electrical systems? Do you have formal training in electrical systems?

Some folks pass along electrical advice in online forums without any experience or true understanding. You post a lot about electrics but often it's the good work of others that has been discombobulated. Please tell us your experience and training so we can know that your words can be trusted.

Click to expand...

John61ct, what is your experience and training in electrical systems?

I have answered you wrt such questions before via PM last year. I only share what I choose about what I consider personal info. Do with that what you will.

No you have not ever replied, despite repeated requests for info.

Be honest with us...

Just wonder,

The house deep cycle batts do an OK job of engine starting, even a 40-50% SOC if the bank is large , and has good plate area.

This might make it possible to forgo an actual start style batt and simply add to the house bank.

Great, till OOOPS the house bank gets too dead to crank the engine.

Has anyone attempted a main engine start with the small nicad power pack booster made for cars?

I stick with my suggestion of connecting the alternator output directly to the start battery and interconnecting the battery banks with an ACR. Even with a thruster connected to the start battery the ACR will still work because they work both ways. By that I mean that when you run the thruster, it will draw the start battery down below the threshold voltage of the ACR which will cause the ACR to open the connection circuit separating the batteries. The only time this might not happen is when the alternator output is higher than the thruster draw, which would require a rather beefy alternator.


As far as connecting the alternator directly to the house bank goes and relying on an ACR to connect the start battery for charging, you may find that the start battery doesn't get much charge. The reason is that if you have a large, significantly depleted house bank it may take quite a while to push the voltage above the ACR threshold voltage. Depending on the size ad charge state of the house bank and the length of the engine run the start battery may actually receive no charge. On the other hand, connecting the alternator to the start battery pretty much guarantees that both banks will be charged. The reason is that although starting an engine requires a big amp draw the duration of that draw is short (unless you have starting issues). So the start battery is not significantly depleted. For example a 500 amp draw for 5 seconds is about 0.7 amp-hr. The result is that the alternator will quickly push the start battery voltage above the ACR threshold so that the alternator will charge the house bank, generally within a minute of engine start.

TDunn, check out this post from CMS, specifically points 4 and 5.

Trawler Forum - View Single Post - Anyone use an ACR?

The ACR controls charge, not load. I have a battery switch to combine LOADS if I need to start with the house bank. It's never been a problem, even with 2 engines starting from a single Group 31 FLA.