Start vs. House bank

[4mo]

Hi all,

I bought a new to me 1996 Carver 370 Voyager last fall and have been having a blast on it this summer with my family in the San Juan and gulf islands.

First off thanks! This forum has been super helpful and I searched the forum for this but didn't see anything specific, so....

The bank that came with my boat is 4 group 27's in two banks. I kept the switch on 'all' this summer (400Ah) and ran down the batteries a few times overnight. I have since installed a monitor to help with that but also am upgrading the bank as well so I don't have to run the genny as much on the hook, where we like to be. My generator has its own start battery so I'm not sure on the need for a separate starter bank. (thoughts?) I also have gas Crusader 454 XL engines and I'm not sure if I need higher cranking batteries to start those or if GC2s would be okay.

Option 1: keep 2 group 27s and add a bank of 4 GC2s. This would have a starting bank and a house bank (420Ah). This wouldn't increase the size of my usable bank much as I'm under the impression that I would want to use these as two banks, not put the switch to 'all' except when the alternator or generator is charging them. Is that correct? Could I use them on 'all' and have a 620 AH bank?

Option 2: Replace the other 2 group 27s with 2 more GC2's and have a total of 6 GC2's all together and keep the switch on 'all' for 630Ah.

Option 3: I might be able to squeeze in 8 GC2s. This would necessitate a little more fiddling, and twice the cost but then I could leave them as one larger bank with the 'all' switch and have an 840Ah bank. Would this be an issue starting the motor vs. the duel purpose group 27's?

Thanks in advance for the experience and expertise!

 

[motion30]

In my humble opinion I would ditch the group 27 batteries, as they are not deep cycle. 6 golf cart batteries would be a decent house bank and easy it allow you to start your Motors

 

[Lou_tribal]

I am in favor of having a separate dedicated starting battery so if by any mean I run the house bank empty over the night I am not stuck.

L

 

[4mo]

I am in favor of having a separate dedicated starting battery so if by any mean I run the house bank empty over the night I am not stuck.

L

Even though i can always start the generator and then start the mains? that does take a while, which could be an issue if i'm dragging or something. Any other reason?

I am all in favor of separate starting batteries, but given the amount of space available and desire to increase the bank size, I can't have both.

 

[DavidM]

As Lou noted it is much better to have separate start and house banks that you can keep isolated. But you need to look carefully and see if they truly are isolated: separate outputs from your shore power charger, propulsion engine alternators going to just one battery bank, etc. Also think about how to charge both banks when they are isolated. Use an ACR or similar, etc.


There are many more questions above than can be easily answered in a forum like this. If you are a DIY kind of guy then buy a copy of Nigel Calder's electrical book and dive in. Otherwise get a marine electrician to work out the boat's electrical system with you.


When you do separate the banks, then use a starting battery for starting and a deep cycle battery for house loads. A single good Group 31 should start those engines fine. Some say you need two separate starting batteries for redundancy. That is fine if you have the space but then you need to consider how to maintain isolation and charging of both.


Finally by far the best and cheapest house batteries are pairs of GC2 batteries that can be purchased from Batteries Plus, Costco, etc. Since you have run your existing batteries down a time or two, use at least three pairs of GC2 batteries for 660 AHs.



David

 

[4mo]

In my humble opinion I would ditch the group 27 batteries, as they are not deep cycle. 6 golf cart batteries would be a decent house bank and easy it allow you to start your Motors

If they (6V golf cart - GC2s) can start the motors easily that seems like the way to go.

I bought 4 yesterday and will be installing those on Thursday, and trying to see what I can actually fit in there.

 

[4mo]

As Lou noted it is much better to have separate start and house banks that you can keep isolated. But you need to look carefully and see if they truly are isolated: separate outputs from your shore power charger, propulsion engine alternators going to just one battery bank, etc. Also think about how to charge both banks when they are isolated. Use an ACR or similar, etc.


There are many more questions above than can be easily answered in a forum like this. If you are a DIY kind of guy then buy a copy of Nigel Calder's electrical book and dive in. Otherwise get a marine electrician to work out the boat's electrical system with you.


When you do separate the banks, then use a starting battery for starting and a deep cycle battery for house loads. A single good Group 31 should start those engines fine. Some say you need two separate starting batteries for redundancy. That is fine if you have the space but then you need to consider how to maintain isolation and charging of both.


Finally by far the best and cheapest house batteries are pairs of GC2 batteries that can be purchased from Batteries Plus, Costco, etc. Since you have run your existing batteries down a time or two, use at least three pairs of GC2 batteries for 660 AHs.



David

Thanks David! I got 4 GC2s from Costco yesterday for $94 each +tax. I'm going to try to fit them Thursday to see how many i can actually squeeze in there. Its mostly a matter of space at this point, if i can do 6+ starting then i'll probably do that.

 

[kchace]

Thanks David! I got 4 GC2s from Costco yesterday for $94 each +tax. I'm going to try to fit them Thursday to see how many i can actually squeeze in there. Its mostly a matter of space at this point, if i can do 6+ starting then i'll probably do that.

The 27's you have are not nearly as heavy duty as GC2's AND they came with the boat, I think you'll find the GC2's provide MUCH more usable power than (probably) abused group 27's.


Since you have them, I'd keep 2 27's to use as dedicated start batteries.



Ken

 

[FlyWright]

Thanks David! I got 4 GC2s from Costco yesterday for $94 each +tax. I'm going to try to fit them Thursday to see how many i can actually squeeze in there. Its mostly a matter of space at this point, if i can do 6+ starting then i'll probably do that.

Sounds like a good plan. I run a 6xGC2 house bank for an easy 2 day stay on the hook without the gen. My start battery for two Perkins diesels is a single Gp 31 start from Costco. Works like a champ!

 

[Tom.B]

Redundancy is key. There is such a thing as too many banks AND too few. Still, you kinda want the right battery for the job. Ideally a single start bank and a single house bank with a1/2/A/O switch on each bank to select where each it goes. You should swap out the G27s for 12V dual purpose versions (2 in parallel) and fit as many 6V golfcart batteries as you can in the remaining space (4 or 6 if you can). Lose the genset start battery altogether.



Pull your alternator lines, that are probably on your starter studs, and put them on your house bank. Then use a automatic charging relay to just from house to start bank.



All done.

 

[dhays]

In your shoes, I think I would consider using a single battery to start the genset and the motor and keep your house bank separate. Setup properly the start battery will always be charged and ready to so and if it fails you can use the house bank to start either the motor or genset.

 

[4mo]

I really appreciate the throughts!

The genset battery is in the lazarette by the generator, so its not taking up any space by the rest of the bank which is under the saloon. I guess i could run the starter wires back to it, but that seems unnecessary.

The current group 27s are duel purpose I believe

 

[dhays]

I really appreciate the throughts!

The genset battery is in the lazarette by the generator, so its not taking up any space by the rest of the bank which is under the saloon. I guess i could run the starter wires back to it, but that seems unnecessary.

The current group 27s are duel purpose I believe

I’m not an expert, but I’ve heard plenty of folks that do know what they are talking about (as opposed to me) that have opined that “dual purpose” is a marketing description more than a description of the build.

Anyway, you mentioned that you didn’t have room for a separate start battery. My thought was that you already have a separate start battery and could use it for both. If it is too small for your main engine, then just upgrade it and then design your house bank to hand the house loads. Again, maybe not a great idea as I’ve not seen your boat, but think about it.

 

[BruceK]

I suggest keep your genset start batt dedicated to the genset. It`s your lifeline, preserve it. Mine even has its own little 25w solar panel for batt maintenance.
If you can set up dedicated start batts, do it.
Island Gypsy boats like mine typically have as OEM 2 large batts one associated with each engine serving both start and house function. Not ideal, doubtless some have changed it, I and some others have not, and it works, I never run out of battery. Early in ownership before I knew the batts were cactus, I needed the genset as backup, so keep it ready to go at all times. Maybe set it up to start mains if needs be, to cover possible emergency.

 

[tiltrider1]

It’s all about how much redundancy you can afford. Dedicated gen battery, dedicated start battery, house bank is optimum. Can you get by with house/start bank made of GC batteries? Yes, just less optimum. You do what you have to do. If I was combining my house & start bank I would use GC batteries.

 

[4mo]

I’m not an expert, but I’ve heard plenty of folks that do know what they are talking about (as opposed to me) that have opined that “dual purpose” is a marketing description more than a description of the build.

Anyway, you mentioned that you didn’t have room for a separate start battery. My thought was that you already have a separate start battery and could use it for both. If it is too small for your main engine, then just upgrade it and then design your house bank to hand the house loads. Again, maybe not a great idea as I’ve not seen your boat, but think about it.

Dave, I appreciate you literally thinking outside the battery box on this one! I'll check it out tonight when I'm assessing how many batteries I can fit.

 

[AKDoug]

My boat came with 3 group 24's, it would run well below 50% just being on the hook overnight with only the refrigerator running. I upgraded to 2 4D AGM's and a single group 27 start battery. The House bank is the 4D's on a single battery switch, the 27 is on a single switch, and there is a switch to join the two banks in an emergency (that is always off). I used AGM's because my access to the batteries is poor and I can't access the tops to check fluid levels.

I did have to redesign the battery compartment to make everything fit, but with 5 years on the system everything is good. The charging system tops off the house bank first, then switches over to the start battery, which obviously gets little use and never gets drawn down like the house bank. I did tap my pot puller into the start battery to help discharge it in an effort to keep the battery healthy by using it and drawing it down so it will recharge.

For me, it's been the best solution and is working well. The engine is always running when pulling pots, and the house bank is almost always topped off when pulling pots. As a fireman, we always had problems with recharging batteries when they didn't get drawn down before recharging as they tend to take a surface charge and not last long.

My two cents...

 

[FlyWright]

Since 4mo has twins, one alternator can charge the start battery and the other alternator can charge the house bank. Of course, the larger the bank, the larger the charge requirements.

Similar to AKDoug, I run my windlass from my start battery since the engines are always running when the windlass is used. If I lose an alternator, a switchable Yandina combiner allows either alternator to charge both battery banks.

Below is a schematic of my system before many components were upgraded but it shows the general layout. Remember that it's important to supply ample charging if you increase your bank capacity.

 

[4mo]

So after looking at it last night and with all the helpful advise from you guys i think i have a plan. I can fit 4 golf carts in where 2 of the group 27s were. I'll leave the other 2 group 27s as start batteries and also leave the separate generator battery. I'll see how that works for a while.

If I decide that i want a lot more, i can fit 8 GC batteries in the space and still have room for one group 31 if I purchase more efficient battery boxes like these: https://allbatterysalesandservice.c...box-holds-4-6-volt-golf-cart-batteries-gcq-g/

I could do 6, but the cost difference is only $200, so might as well do 8 if I need to.

Here is the space as well as the tray i made for the boxes last night.

For wiring I'm planning on wiring the windlass off the start batteries and keeping it simple with the 1-both-2-off switch for now.

I only have one alternator so my procedure would be to wake up in the morning, check the batteries, make coffee (press) and when its time to pull the anchor i would switch it from the house bank to the start bank, start the motors, pull anchor, then switch it to house bank while i'm under way to charge up the house bank with the alternator.

That sound right?

 

[4mo]

pictures

 

[Cigatoo]

“ only have one alternator so my procedure would be to wake up in the morning, check the batteries, make coffee (press) and when its time to pull the anchor i would switch it from the house bank to the start bank, start the motors, pull anchor, then switch it to house bank while i'm under way to charge up the house bank with the alternator. “

Even more simple......

Keeping the start bank and the house bank separate and having an ACR would do this for you. (Except making the coffee)

 

[4mo]

That sounds perfect, so the Blue Sea Si-ACR automatic charging Relay - 12V DC 120a?

I wonder how to wire that with my battery monitor (victron bmv-700) on the house bank?

 

[Cigatoo]

That sounds perfect, so the Blue Sea Si-ACR automatic charging Relay - 12V DC 120a?

I wonder how to wire that with my battery monitor (victron bmv-700) on the house bank?

Not sure one will have anything to do with the other. The ACR just charges the house bank 1st and then moves to the start bank when the house is charged. No need to touch the combiner switch.
Maybe someone else can add something here?

 

[AKDoug]

I am a little confused by so much switching, my start and house batteries are dedicated and once I switch them on I don't touch the switches again until I dock and shut everything down, including my through hull fittings. The only time I would use the crossover switch would be if one or the other of the banks had died.

It sounds like your batteries will only charge one bank at a time from your alternator, and that's why you're switching them? I would look at a unit to automatically switch the charge from one bank to the other once a certain level of charge had been achieved, that's what I use. I also have only one alternator...

 

[Cigatoo]

“I would look at a unit to automatically switch the charge from one bank to the other once a certain level of charge had been achieved, that's what I use. I also have only one alternator...”

That’s the scenario/ ACR relay that I just described. No switching necessary.

 

[AKDoug]

“I would look at a unit to automatically switch the charge from one bank to the other once a certain level of charge had been achieved, that's what I use. I also have only one alternator...”

That’s the scenario/ ACR relay that I just described. No switching necessary.

Yep, your post wasn't visible when I posted my comment

 

[4mo]

Thanks both of you.

Is it the Starter isloating ACR that I want?

 

[AKDoug]

I have a Balmar Digital Duo Charge unit, it has been flawless for me. I am sure there are several different manufacturers making units that do the same thing.

It simply mounts between the house and start batteries

 

[FlyWright]

There are plenty of threads here on TF addressing ACRs/combiners vs isolators. Use the TF Search link at the bottom of my post to find existing discussions on the issue. Great guidance can be found on CMS's website.

 

[FF]

PLAN B or C

You might contemplate going to all deep cycle batts , as it will work well -except in an emergency.

If the noisemaker batt was large enough , you might pull it out and drag it to where a QUALITY set of jumper cables would work.

http://www.wiringdepot.com/store/p/3977-Commercial-Service-Booster-Cables-4-Gauge-16ft.aspx?feed=Bing&msclkid=2c65a04acac518d7ba88fbd809408c92&utm_source=bing&utm_medium=cpc&utm_campaign=Wiring%20Depot%20-%20Shopping&utm_term=4582695746474083&utm_content=Shopping

Plan C would be to borrow one of the super start emergency batts from a dock mate and see if it will start the engine when cold.

https://www.amazon.com/s/?ie=UTF8&k...targid=kwd-11625213010&ref=pd_sl_2ih03ljwkn_b