Two House banks

[sstanley]

So, we recently bought a nordic tug that has, what seems to me, a weird house bank arrangement. I am looking for opinions on the pros/cons of this type arrangement. What we have is this;

House bank 1: 300AH, serves solely the DC loads
House bank 2: 600AH, dedicated solely to the inverter and thus AC loads

There are also dedicated engine and genset starter batteries, so those are isolated and independent of the house banks.

My boating background is on sailboats and I never had more than one house bank that served both DC and AC loads. On this nordic, we find that typically we put a heavy load on house bank 1 and we run very few things that use house bank 2 very much. Seems like a waste to me to have 2/3 of my capacity little used, so I am considering rewiring to be a single 900AH house bank serving both AC and DC loads.

I am looking for pros/cons on this 1 bank versus 2 bank arrangement. Any thoughts on this? With my background, I really do not see the pros on why someone would set up two independent house banks this way. But my experience is limited...

Thoughts?

Scott

 

[North Baltic sea]

Hi, the previous owner may have used 110V more.

I would do as you suggested 1 bank 900Ah, it will serve your boating better.

NBs

 

[Iggy]

I would agree with the Baltic. Plus you would get more time and less wear and tear on batteries from your D.C. & A.C. loads. In other words, you just increased your bank 1 by 200% (3 times) and bank 2 by 33% For the same load and time before combining the two banks. Now the one combined bank will be discharges less and give you more time between charging.

I would be mindful of age and types of batteries between the two banks before combining them. Also you may have to change how the two banks are being recharged. Not knowing the setup. Maybe the Alt is small and if both bank are low the Alt was over heating. So the past owner was charging one bank at a time. Just a thought?

The general rule-of-thumb for alternator output to battery size ratio is 4:1.

 

[OldManMirage]

The general rule-of-thumb for alternator output to battery size ratio is 4:1.

So basically a 100 amp alternator would be ok with a 400 AH bank ?

 

[twistedtree]

I agree that combining the banks would be preferred, but check carefully what's involved. There might be a practical/logistical reason why they are separate.


Are the banks the same voltage? Having something like a 24V inverter bank and 12V house bank would of course drive you to two banks.


Are the batteries the same technology, e.g. AGM, flood lead acid, etc?


Are the batteries the same size, e.g. 8D, 4D, Group 31, etc.?


How far apart of the two banks? If the cabling to one bank is much longer than the other bank it will be harder to keep the batteries at the same charge level.



Are the banks in the same environmental space? If some are in the ER and some in the laz, they will experience different temps and need different charge compensation.


What charging sources are at play? Which go to the DC load bank and which go to the Inverter load bank? Are there any issues combining all of them?

 

[Iggy]

So basically a 100 amp alternator would be ok with a 400 AH bank ?

TT: Your good with your suggestions. Love this forum!

If your asking me? I am generalizing. Others can answer this better than me! But, I can't see a 70A Alt charging a 1000A bank.

On my own boat, I have a 600A bank with a 120A Alt. Not 4 to 1, but it works with an external regulator and a temp sensor. If my batteries are below 60%, I start my genset for 20 mins and charge from the charger/inverter. Taking some load off the Alt. Keep in mind, the starting bank load too.

 

[sunchaser]

Is the bank in question dedicated to windlass or thrusters? This is quite common.

 

[Shrew]

I have a friend who did this.

2 start batteries (one for each engine)
1 Genny start battery
12V house bank
12V Inverter bank.

The inverter bank only runs the outlets, TV, DVR, satellite and (I think) the fridge (not sure why it's dual voltage).

I don't like his set-up. House and Inverter bank can only be charged by the generator. My question (which I don't think he can answer) is 'which bank are the navigation equipment connected too?

I wouldn't want the GPS, Radar and Auto-Pilot pulling from the house or inverter banks in this case.

 

[jleonard]

I had my Albin set up with an "inverter bank" with 4 Gofl Cart batteries and a "house/starting bank" using 3 group 31 batteries.
Initially they were separated, but I combined them into one large bank.
It worked fine and was easily charged with a 70-amp Balmar alternator.
Maybe "in theory" the numbers don't work out, but in my application, it worked fine.

 

[cafesport]

So I would recommend doing nothing other than use the boat as is for a year. There will be more than enough other projects that need more attention while you are figuring out your electrical wants and needs.

Independent Isolated banks are a good thing as far as maintenance and redundancy are concerned.

Battery type, age and charging needs might not make paralleling an option at this point.

How are your banks all charged underway? At the dock? Alternator/alternators, Inverter/charger, charger,solar dc2dc? Quite a few things to figure out, so I’d just go enjoy using what you have for now.

We have four main house banks and usually run with three parallel. We also have another 3 banks that we parallel in as needed or to rotate banks for maintenance. We a added an overnight lithium bank which through a dc 2 dc charger brings the online house banks to full charge by morning. The lithium bank is mostly charged via solar during the day but has its own small charger for cloudy days.

This system evolved over the years once we better understood our energy needs. When we first got the boat we assumed our batteries had the full rated capacity as they were only two years old. Running the batteries down to 80% soc wound up really being to 50%. Didn’t realize it until our second year.

 

[Jeff F]

So I would recommend doing nothing other than use the boat as is for a year. There will be more than enough other projects that need more attention while you are figuring out your electrical wants and needs.

Good advice IMO. I'd suggest that you invest in monitoring tools, maybe a shunt on each bank to give insight into your use case and needs and how the existing system meets those needs.

 

[sstanley]

Thanks. This is where I am leaning right now. Was not sure if there was some logical reason for the two.

 

[sstanley]

Let's try this again. Thought I could reply to an individual post, but I guess not.

I am definitely leaning towards combining the two right now, but I totally agree with cafesport, this is not a high priority project. Just thinking about the future and what I would like to do. We have had the boat about 11 months and the list of work to do is already pretty long, so repairs come first then followed by the upgrades I would like to do.

In response to some of the questions,

Neither of these banks serve the bow thruster/windlass or the stern thruster. These each have their own batteries I just didn't mention them above (feels like the boat has gazillion batteries at some points). The total batties are,

House bank 1: 300AH, serves solely the DC loads (2 x 6v @ 300AH each)
House bank 2: 600AH, dedicated solely to the inverter and thus AC loads (4 x 6v @ 300AH each)
Engine Start: 2 x 12v @ 150 AH, 1000 CCA each
GenSet Start: 700 CCA
Bow Thruster/Windlass: 4D battery, but not sure of specifications
Stern Thruster: 4D battery, but not sure of specifications

At the dock charging;
- House bank 2 is charged by a Victron Energy, MultiPlus 12v 3000 (120A) charger/inverter. Documentation says it recommends 500AH to 1200AH battery bank.

- All of the other batteries charged by a Mastervolt Powercharger 12/40 (40A).

When away from the dock, House bank 2 is strictly charged via the charger/inverter and the Genset. The rest all get power from the 110A alternator when underway and when the GenSet is running can be charged by the Powercharger.

Been looking at this a lot this week and it seems to me the Powercharger is pretty seriously underpowered for the battery capacity it is asked to serve. The battery manufacturer for the 6v batteries in house bank 1 recommends for deep cycling of power that the charger should provide 0.2C (0.2 * 300AH gives 60A). This does not include the fact this charger is also supporting the bow/stern thruster batteries and the two start batteries.

A lot of information there for those interested.

There are a lot of things for me to think about with this. Thankfully the two house banks are very near each other and both chargers. I am a little worried about the redundancy concerns of one house bank. I believe all the electronics are power by house bank 1 which combining banks would put it all on the same bank as the inverter loads. Also, right now I am a little concerned with the batteries in house bank 1. Seems to me they drain faster than they should... Need to check those and see if they are good.

I am certainly not rushing in to any changes, just trying to gather as much information as I can right now so I can make an informed decision. I really appreciate all of the feedback everyone.

 

[RobertLeatch]

I'll put the countary view.

I have a very similar 2 bank set up split to DC and AC loads and really like it. In my case, both banks are currently made from Trojan T105 6v in series/parallel to12v. B1 (DC) is 6 batteries and B2 (AC) is 12 batteries. Each bank is located on opposite sides of a twin engine boat. Pros as I see it are:

1. If I did join the banks, it would require a 3 metre cable across the boat. This would make balanced charging in the bank difficult. Moving the 2 banks to be co-located would create a weight imbalance and likely reduction in total number of batteries.

2. I monitor loads on each bank separately (via dedicated shunts and Victron Bmv 702 displays) and like being able to see loads as either coming from AC or DC appliances. Really helps trouble shooting.

3. My inverters are large (2 x Victron 12/3000/120 in parallel) and can pull 300+ amps at times. Separating the DC loads seems to prevent some of the devices from powering off under low voltage spikes.

4. I like the redundancy and flexibility of each bank having it's own dedicated charger (the inverter/charger and a separator Victron Phonex charger) and each engine alternator charging a separate bank. If (probably when) I change 1 of the banks to a different battery type, I think it will be easier to adjust the charging profile for that bank.

I have occasionally joined the 2 banks by a standard 1/2/both switch, but in general things work fine with the separate banks split by load source.

 

[Iggy]

Let's try this again. Thought I could reply to an individual post, but I guess not.

I am definitely leaning towards combining the two right now, but I totally agree with cafesport, this is not a high priority project. Just thinking about the future and what I would like to do. We have had the boat about 11 months and the list of work to do is already pretty long, so repairs come first then followed by the upgrades I would like to do.

In response to some of the questions,

Neither of these banks serve the bow thruster/windlass or the stern thruster. These each have their own batteries I just didn't mention them above (feels like the boat has gazillion batteries at some points). The total batties are,

House bank 1: 300AH, serves solely the DC loads (2 x 6v @ 300AH each)
House bank 2: 600AH, dedicated solely to the inverter and thus AC loads (4 x 6v @ 300AH each)
Engine Start: 2 x 12v @ 150 AH, 1000 CCA each
GenSet Start: 700 CCA
Bow Thruster/Windlass: 4D battery, but not sure of specifications
Stern Thruster: 4D battery, but not sure of specifications

At the dock charging;
- House bank 2 is charged by a Victron Energy, MultiPlus 12v 3000 (120A) charger/inverter. Documentation says it recommends 500AH to 1200AH battery bank.

- All of the other batteries charged by a Mastervolt Powercharger 12/40 (40A).

When away from the dock, House bank 2 is strictly charged via the charger/inverter and the Genset. The rest all get power from the 110A alternator when underway and when the GenSet is running can be charged by the Powercharger.

Been looking at this a lot this week and it seems to me the Powercharger is pretty seriously underpowered for the battery capacity it is asked to serve. The battery manufacturer for the 6v batteries in house bank 1 recommends for deep cycling of power that the charger should provide 0.2C (0.2 * 300AH gives 60A). This does not include the fact this charger is also supporting the bow/stern thruster batteries and the two start batteries.

A lot of information there for those interested.

There are a lot of things for me to think about with this. Thankfully the two house banks are very near each other and both chargers. I am a little worried about the redundancy concerns of one house bank. I believe all the electronics are power by house bank 1 which combining banks would put it all on the same bank as the inverter loads. Also, right now I am a little concerned with the batteries in house bank 1. Seems to me they drain faster than they should... Need to check those and see if they are good.

I am certainly not rushing in to any changes, just trying to gather as much information as I can right now so I can make an informed decision. I really appreciate all of the feedback everyone.

Good luck on how ever you handle this. You could say, I have the cousin to your boat. A Pacific Trawler 40, at first glance you would think there the same boat. I don't know the real history but I have heard that a engineer form Nordic left and created Pacific Trawler.

Anyways, If your batteries may need replacement. You might want to look at lithium. I went down that route last year and very happy I did. In my boat they take up less room, much lighter and more useable amps for the same size bank. The hard part was planning on how to set them up. Your Victron charger can handle lithium too.

 

[ranger58sb]

So, we recently bought a nordic tug that has, what seems to me, a weird house bank arrangement. I am looking for opinions on the pros/cons of this type arrangement. What we have is this;

House bank 1: 300AH, serves solely the DC loads
House bank 2: 600AH, dedicated solely to the inverter and thus AC loads

There are also dedicated engine and genset starter batteries, so those are isolated and independent of the house banks.

Neither of these banks serve the bow thruster/windlass or the stern thruster. These each have their own batteries I just didn't mention them above (feels like the boat has gazillion batteries at some points). The total batties are,

House bank 1: 300AH, serves solely the DC loads (2 x 6v @ 300AH each)
House bank 2: 600AH, dedicated solely to the inverter and thus AC loads (4 x 6v @ 300AH each)
Engine Start: 2 x 12v @ 150 AH, 1000 CCA each
GenSet Start: 700 CCA
Bow Thruster/Windlass: 4D battery, but not sure of specifications
Stern Thruster: 4D battery, but not sure of specifications

At the dock charging;
- House bank 2 is charged by a Victron Energy, MultiPlus 12v 3000 (120A) charger/inverter. Documentation says it recommends 500AH to 1200AH battery bank.

- All of the other batteries charged by a Mastervolt Powercharger 12/40 (40A).

I wonder how/why your banks were configured that way.

Perhaps your house bank #2 and inverter/charger were added later, i.e., after initial build?

Maybe that owner decided it was just easier to add than it would have been to reconfigure an original house bank for an inverter?

Just forensic speculation...

-Chris

 

[sunchaser]

SS
Have you asked the previous owner the same questions? I can think of other options, not uncommon, as to why this setup.

 

[Pete Meisinger]

As long as you have a crossover switch, I like the present set up.

pete

 

[Jeff F]

Been looking at this a lot this week and it seems to me the Powercharger is pretty seriously underpowered for the battery capacity it is asked to serve. The battery manufacturer for the 6v batteries in house bank 1 recommends for deep cycling of power that the charger should provide 0.2C (0.2 * 300AH gives 60A). This does not include the fact this charger is also supporting the bow/stern thruster batteries and the two start batteries.

This depends on your use case. The only time you'll be deep cycling with the charger is multiple days at anchor with occasional generator use. And in those cases the other batteries should remain fully charged, so the house bank should receive the majority of charger capacity. Doesn't seem like an issue to me.

I understand the rationale behind your existing system. It was done deliberately, and has some advantages.

I'd leave it alone, note pain points and concerns, and prepare to make it your own when it's time to replace existing batteries or make other changes. Also consider how solar and/or lithium might fit into the mix in the future.

 

[tpbrady]

Stanley,

Nordic Tug configured a lot of 42s this way from what I can tell. Ours is hull 002, and was set up that way with the starboard bank (2-8ds) for the inverter and the similar port bank for the house loads. It had been so modified since it was built by previous owners, nothing seemed to work quite right. After problems with AGM batteries that seemed to be going bad after 3 years, our first year of ownership, I spent about 4 hours mapping out all the DC cabling and found that the port and starboard banks had been paralleled three ways. I removed a fair amount of cabling and got 5 more years out of the batteries.

Before you embark on any changes, map out your DC cabling to see how the batteries including bow and stern thrusters, are charged while under way and when on shore power. There are a lot of ways to do it. On my Tug, the original construction used an Echo Charger to charge the start bank and a Xantrex Pathmaker for the bow thruster (stern thruster was hydraulic off the generator).

The engine alternator was only 100A so a little small to charge 800A of batteries that had been used for a few days. It’s output peaked at 13.6v so was not working correctly any way. I replaced it with a 200A. The battery monitoring originally was a Link 2000 for the house bank and a Link 20 that watched the start and bow thruster batteries.

They are pretty much all gone now. Hope my experience with Nordic Tugs helps.

Tom

 

[motion30]

So, we recently bought a nordic tug that has, what seems to me, a weird house bank arrangement. I am looking for opinions on the pros/cons of this type arrangement. What we have is this;

House bank 1: 300AH, serves solely the DC loads
House bank 2: 600AH, dedicated solely to the inverter and thus AC loads

There are also dedicated engine and genset starter batteries, so those are isolated and independent of the house banks.

My boating background is on sailboats and I never had more than one house bank that served both DC and AC loads. On this nordic, we find that typically we put a heavy load on house bank 1 and we run very few things that use house bank 2 very much. Seems like a waste to me to have 2/3 of my capacity little used, so I am considering rewiring to be a single 900AH house bank serving both AC and DC loads.

I am looking for pros/cons on this 1 bank versus 2 bank arrangement. Any thoughts on this? With my background, I really do not see the pros on why someone would set up two independent house banks this way. But my experience is limited...

Thoughts?

Scott

When I bought my boat it had a similar set up, Now I have one big Bank that does everything. It works well and I have no plans to change it

 

[sstanley]

I'll put the countary view.

I have a very similar 2 bank set up split to DC and AC loads and really like it. In my case, both banks are currently made from Trojan T105 6v in series/parallel to12v. B1 (DC) is 6 batteries and B2 (AC) is 12 batteries. Each bank is located on opposite sides of a twin engine boat. Pros as I see it are:
.
.
.
I have occasionally joined the 2 banks by a standard 1/2/both switch, but in general things work fine with the separate banks split by load source.

I like the idea of the crossover switch. I do not have that option right now. I assume you need to have special care in charging if you put them in Both since both banks have their own charger. How do you deal with this?

 

[sstanley]

Anyways, If your batteries may need replacement. You might want to look at lithium. I went down that route last year and very happy I did. In my boat they take up less room, much lighter and more useable amps for the same size bank. The hard part was planning on how to set them up. Your Victron charger can handle lithium too.

Yeah, I have been giving lithium a lot of thought this week. I tested batteries and one of the six 5v batteries in the two banks is bad. It is hard to convince myself right now that replacing them all with lithium instead of replacing the single battery is a good option, a lot more $$. Would like to do that though. I am not enthused about trying to figure out how to manhandle a 90lb 6v battery in to the box in the limited headroom of my engine room.

 

[sstanley]

Stanley,

Nordic Tug configured a lot of 42s this way from what I can tell. Ours is hull 002, and was set up that way with the starboard bank (2-8ds) for the inverter and the similar port bank for the house loads. It had been so modified since it was built by previous owners, nothing seemed to work quite right. After problems with AGM batteries that seemed to be going bad after 3 years, our first year of ownership, I spent about 4 hours mapping out all the DC cabling and found that the port and starboard banks had been paralleled three ways. I removed a fair amount of cabling and got 5 more years out of the batteries.

Before you embark on any changes, map out your DC cabling to see how the batteries including bow and stern thrusters, are charged while under way and when on shore power. There are a lot of ways to do it. On my Tug, the original construction used an Echo Charger to charge the start bank and a Xantrex Pathmaker for the bow thruster (stern thruster was hydraulic off the generator).

The engine alternator was only 100A so a little small to charge 800A of batteries that had been used for a few days. It’s output peaked at 13.6v so was not working correctly any way. I replaced it with a 200A. The battery monitoring originally was a Link 2000 for the house bank and a Link 20 that watched the start and bow thruster batteries.

They are pretty much all gone now. Hope my experience with Nordic Tugs helps.

Tom

Thanks for the information Tom. Interesting to know Nordic did this from the factory on many boats. If there is any crossover between my two banks, I can not figure it out so far. If I could find one, then that might go a long way to resolve my concerns with this.

I believe I have tracked through the charging circuit for HB1, the engine start, genset start and thrusters. Took me a little time to track through that. I need to do the same for HB2 with the inverter. I have not been able to track through the load side of the system yet. That is a lot harder since it goes out of the engine room and it is really hard to tell where cables are going. If there is a crossover between the two banks I believe it is going to be up around the nav station.

 

[ranger58sb]

I am not enthused about trying to figure out how to manhandle a 90lb 6v battery in to the box in the limited headroom of my engine room.

Pay the nice boatyard man for one of his labor force.

-Chris

 

[RobertLeatch]

I like the idea of the crossover switch. I do not have that option right now. I assume you need to have special care in charging if you put them in Both since both banks have their own charger. How do you deal with this?

I normally don't do a serious charge while the two banks are connected (though old school lead acid are pretty tolerant anyway so wouldn't stress to much If some unbalanced charge was occurring). I only tend to join them if the DC bank is a bit low (say <60%) and I need to use the davit to raise or lower the tender.

Not sure of your alternator setup, but if you dont go the external regulator option (which I didn't) the Id recommend putting in a blower directing cool air over the alternator. I have stock small frame 90amp alternators and since I put in the blowers I've seen them put out 75amps for many hours at a time with no apparent overheating issues.

 

[RobertLeatch]

Further to the charging question, I only tend to join when where off shore/generator power and in this situation the inverter/charger isn't charging the AC bank (because its inverting) and we turn off the phonex charger for the DC bank (because it would not be efficient to go from DC to AC to DC).

The photo shows where we monitor/control the 2 banks (and some AC stuff). Its a cliche but you can't fix what you can't measure.

 

[bkcorwin]

I have two banks but a 12v and a 24v bank with the 24v bank powering the inverters. You mention the house 1 charger may be a bit small. You need to figure out what your drawn down statistics are on the boat while at anchor for each bank. Then, the goal should be to size the charger so that both house 1 and house 2 have sufficient charging capacity so that they charge at similar rates with the generator on.

We had a situation where our 12v charger was much smaller and then we required extended generator usage solely to maintain the 12v bank. This was a problem as it made loading the generator difficult. We increased our 12v charging capacity and now both banks charge at much closer rates.

 

[SteveK]

Suppose I get two 12 volt lithium. Is it better to feed a 12 volt inverter or Combine and feed a 24 volt inverter

 

[Pcpete]

I too have a separate dedicated inverter battery bank. But……I’m going to modify that. The boat has 2 31’s for starting, charged by the port engine/alternator and hard wired battery charger; 4 golf cart batteries for the house/accessory circuit, charged by the starboard engine/alternator and the hard wired battery charger; one 27 series battery, charged by the generator/alternator and the hard wired battery charger; 4 additional golf cart batteries for the inverter that recharges through the inverter/charger only.
Last summer we had a situation where the DC circuit board in the generator fried requiring some energy management. The refrigerator was switched from the inverter 120v to the accessory/house 12v. This made it so we could finish the trip although the inverter batteries were pretty run down. The generator has been fixed, but not being able to charge the inverter batteries except with the generator or shore power has me thinking. The port alternator gets very little use, so how to put it to work? The plan is to add a battery isolator to the port engine to charge the inverter batteries. The alternator is rated for 160 amps, so once the starting batteries have been replenished, it’s just sitting there. A battery isolator will direct the recharge and charge the inverter bank while keeping the circuits separate. Next, I’ll add a simple switch to combine the house batteries to the inverter batteries, with an as yet unidentified battery management box to keep one bank from discharging the other.