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Old 05-05-2021, 11:09 AM   #1
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House Battery System Configuration Brainstorming

I am thinking through my options on how I would like to configure the house battery set up on my new (to me) Mainship 34 MK1. In particular I'm trying to weight the cost an benefit of retaining the existing charger/inverter as it works and I already own it but it may limit the options I have for other components.

Currently the boat only has 2 - 27 group dual purpose, lead acid batteries that serve as a consolidated starting and house bank. It is charged by a 1500 W Promariner modified (Promariner call is a quasi sine) sine wave inverter/charger. It is incorrectly configured to feed the entire AC panel (which is clearly cannot support). The refrigerator onboard is a AC only unit, that was probably installed in conjunction with the inverter system. The boat has it's original 3kw onan generator which has it's own starting battery. The boat has an electric galley and no other battery systems onboard.

The intended use for the house battery system is pretty modest, I would like to be able run the refrigerator and small ac devices (charging laptops and tablets) for 12-18 hours between charging via shore power or running the generator. Because the boat has an electric galley, I don't anticipate any extended cruising that would not involve having shore power or running the generator at least once a day. I would also like to size, configure and position this battery bank to support future loads such as an upgraded windlass and bow thruster.

I have at least 2 locations I could easily place a dedicated house battery system with easy access to run all the wiring I need.

For purpose of discussion, I'm going to try to generalize my options into 4 approaches but certainly I could go about this in many ways. I'm open to other options.

Option 1 - Dedicated inverter bank, combined starter/house bank:
Leave the two group 27's in place as engine, electronics and house loads, install a new inverter specific bank of flooded lead acid or AGM type batteries to support the existing inverter. Rewire the inverter to limit loads to outlets and install a dedicated charger for the existing bank.

Option 2 - Inverter/house bank, dedicated starter bank:
Leave the two group 27's in place as engine battery only, install bank of flooded lead acid or AGM type batteries to support the existing inverter and house loads. Rewire the inverter to limit loads to outlets and install a dedicated charger for the existing bank.

Option 3 - Lithium Iron Phosphate House/Inverter Bank:
Upgrade inverter/charger to system with charging profile for LiFePO and install new house/inverter bank, properly wired and then install a simple, standalone charger for the starting battery or DC to DC charger to piggyback off of the LiFEPO.

Option 4 - Isolate starting to new bank shared by main engine and generator, replace the existing house/inverter bank with a larger capacity but reuse much of the wiring and battery box. Re-wire the inverter to outlets only.


Goals, constraints, considerations: I want to ensure I don't end up with a dead starting battery and no way to get home, the intended use is all local cruising so if I end up with a dead inverter bank and warm refrigerator, it isn't the end of the world, the boat isn't used far from civilization, I can throw out bad milk. I want a pretty fool proof system that my wife and kids can operate easily. Budget is not limitless, but I'd rather not have to replace components just down the road, I'm perfectly happy with the limited capacity and functionality of the existing inverter, we aren't running expensive components with it and the non-pure sine wave status doesn't seem to be a problem for now, the current (bad pun) issue is the miss-wiring and limited battery options at this point.

I'd appreciate any thoughts. Thanks
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Old 05-05-2021, 11:28 AM   #2
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I like option 3 the best of the approaches you outlined no matter if you choose to go with LiFE batteries or stay with lead acid, it's the only option that puts in a new inverter that can support the house loads without using extension cords if you want to run something that isn't on the 'inverter outlet'. Modified sine is also likely to become a problem in time.

I would think there's going to be quite a bit of cost to rewire your AC panel for options 1, 2, and 4 to divide up the loads. Money would be better spent on a 3KW inverter that can be wired through it's automatic transfer switch and feed all the outlets the same as the genset. Easier to use, easier to configure and you don't have to rewire the AC panel. If you get an inverter/charger it can also charge the bank it's attached to. Put a DC-DC charger to charge the house bank and you'll have an isolated start battery that can be of any chemistry the DC-DC charger supports. You could carry one of the new lithium 'jump packs' as a backup if you are worried about the start bank becoming drained accidentally.
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Old 05-05-2021, 11:50 AM   #3
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I like option 3 the best of the approaches you outlined no matter if you choose to go with LiFE batteries or stay with lead acid, it's the only option that puts in a new inverter that can support the house loads without using extension cords if you want to run something that isn't on the 'inverter outlet'. Modified sine is also likely to become a problem in time.

I would think there's going to be quite a bit of cost to rewire your AC panel for options 1, 2, and 4 to divide up the loads. Money would be better spent on a 3KW inverter that can be wired through it's automatic transfer switch and feed all the outlets the same as the genset. Easier to use, easier to configure and you don't have to rewire the AC panel. If you get an inverter/charger it can also charge the bank it's attached to. Put a DC-DC charger to charge the house bank and you'll have an isolated start battery that can be of any chemistry the DC-DC charger supports. You could carry one of the new lithium 'jump packs' as a backup if you are worried about the start bank becoming drained accidentally.
Thanks, I need to dig a little deeper and should probably diagram out exactly how the AC and DC is configured now in order to design the new setup and avoid hiccups.
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Old 05-05-2021, 11:52 AM   #4
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Seems as if option 2 is your easiest way out if that is what you are looking for.

If you decide to up the ante and go for a system upgrade and a lot of new components you may also want to consider the option of converting your boat to a 24V system. It is something I have been looking into.

You can easily add a couple of switches to your system that will let you use the house bank for starting the engine if your main starter battery fails.

I'm sure you are going to get lots of good advice here on how to proceed. There a lots of places on the internet and uTube that talk about marine electrics. Have a look at some of the videos and advice from Jeff Cote of Pacific Yacht Systems e.g.:

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Old 05-05-2021, 12:20 PM   #5
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IIRC, from a long time ago... and if it helps...

Our 34 Mk III had a single 8D located to starboard, acting as a combined start/house battery. We didn't have an inverter; never got a round tuit on that. Never had any "dead battery" issues and we anchored out often; we just ran the genset 2x/day to charge.

The genset had it's own start battery, and it's alternator charged the genset start battery.

Were it me (without boatloads of more current specific analysis), I think I'd upsize the single start/house battery bank to the extent possible within space constraints, use it as a combined start/house (and inverter) bank... and call it good.

Upsizing would probably include some combination of physically-smaller batteries -- maybe four Group 31s, maybe six GC2s or maybe six of the taller L16s, etc. No 8Ds! Have to pay attention to overall weight, to avoid inducing an unsolvable list. I remember it was a pain to access that 8D to water it; I'd probably choose AGMs to solve that these days. Inverter to outlets,, and in your case, including the AC-only fridge.

In the years since then, we've noticed lots of boats are originally configured with combined start/house banks. Our two most recent boats, ditto, no issues.

That does of course mean paying attention to battery condition... but I've not ever found that very difficult.

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Old 05-05-2021, 12:21 PM   #6
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George

I think you should consider changes as separate decisions... how do you want banks configured and what batty chemistry you want.

My MS had a 2 8D combined house / start bank and a separate 8D thruster (B&S) bank. Gen had its own GP 24 start. MS had originally installed diode isolators for Alt & shore chargers to charge multi batty banks. I have switched from FLA to AGMs but how they are configured have little bearing on which chemistry to use IMO

Over time I have
1. Eliminated diode isolator and substituted a Sterling CVSR to charge house / start & thruster bank using Alt.

2. Eliminated gen batty charging from main eng alt & shore using gen alt to charge itself when run. I also replaced the gen on/off Sw with a 1-2-all-off Sw on same foot print & bolt pattern to allow adding a jumper from house to gen sw for use in an emergy to start gen or periodically to tie in gen batty to "top off" charge it I havent run gen in awhile

3. Recently moved main eng start to my thruster bank leaving a pure house bank. I have combined the 2 house 8Ds into one bank as I installed a Balmar smart gauge to better monitor house V & SOC and start V. The Balmar does not work with a switched configuration and was part of my decisions to combine. One plus I was looking was to separate high amp loads from the house bank. I had issues with V drop when starting affecting electronic nav equip when combined w eng start.

I figure my gen is my back up for start if start battys have any issues and need a charge boost. Back up for gen batty should there be any issues is the gen sw that allows me to combine w house. My plan B back up is to make / carry a jumper to combine main eng starter to house bank.

I have decided to not replace 8Ds when needed but would instead use two GP31 AGM for start / thruster.
I considered and could use 4 GCs or GP31s for house bank. With AGMs East Penn confirmed that with AGMs GP31s work as well as GCs for deep cycle and the converse as well... GCs work as well for starting as GP31s. The reason it holds for AGM is that unlike FLA they do not/ or need to tailor plate design for each application. EP Duracell AGMs state both AH and CCA specs so easy to compare performance. I am pretty sure I will use all GP31s just to keep things consistent.

The decision around LiFePo is one I havent considered seriously as I wasn't interested in investing that much $$$, didn't think I'd be boating long enough to ever break even if the additional life is what is claimed. I do like and willing to pay the premium $ for AGM vs flooded but the changes I've made could easily handle or be satisfied by FLA battys if anyone wanted to (In that case I would certainly use GP31 for high amp start /thruster and 6V GCs for house.

What you decide re inverter & whether to separate loads or manage them manually is another separate decision IMO

Hope above thoughts help. Lots of different approaches and none always correct. Some are proponents of one large bank to service everything and that can work if managed correctly.
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Old 05-05-2021, 12:38 PM   #7
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Thank you to all, a lot of food for thought to work through.

I really enjoy this kind of stuff and it is what brought me to this forum 5 years ago looking for and receiving some great advice on setting up my father's Mainship MK3, that boat already had a dedicated flooded lead acid 6 volt batteries in parallel & series but no generator. We added a generator and changed very little else. He has since upgraded to a newer boat and I am starting my own adventure with this old scow.
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Old 05-05-2021, 11:29 PM   #8
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I had 4 group 31 AGMs in a combined start/house bank on my 34. I think that's the simplest solution. I kept an eye on voltage and never discharged them severely. No problems with supporting AC fridge and modest house loads for 36 hours.

My backup plan for engine start with a dead bank was to start the generator and charge from there. Genset had a dedicated battery. And I carry a lithium booster pack. Never had to do that.

Consider a monitoring system as well. If you are able to keep an eye on current and battery state of charge you'll learn a lot and hopefully avoid a dead bank.
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Old 05-06-2021, 07:19 AM   #9
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A few questions:
- Propane or electric stove?
- Electric water heater has an engine heating coil?
- What is the charger capacity of the I/C?
- Single or twins?
- What is the footprint available for a larger house bank? Can you fit at least 4 GC's?

Manual load shedding of the water heater is easy, especially if it can be engine heated. KIS, Just leave the breaker off. Our twenty gallon holds hot water 2-3 days after a few hour run. The other breakers can be left on. No need to go through a rewiring project for a small job.

We have 6 GC's as a single bank and use that to start the single Perkins engine. The gen has a separate M24 battery as the backup plan if we ran the house bank dead. Our cruise up the east coast to NY Erie Canal and back to FL was no problem even with 2 of the GCs accidentally left disconnected (my bad).
Run the gen an hour in the morning on cruising days or one more time for an hour at dinner if the microwave is needed or its a lay day at anchor.
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Old 05-06-2021, 07:46 AM   #10
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I like option 2 and if you ever need more inverter capacity, you can just install a better inverter without doing anything else. I would use 4/0 wiring from the bank to the inverter so that it's future-proof, capacity-wise. If would include a 500 amp ACR/battery combiner in the mix so that the main engine alternator charges both banks and so you can easily use the house bank for emergency starting.
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Old 05-06-2021, 08:08 AM   #11
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Quote:
Originally Posted by High Wire View Post
A few questions:
- Propane or electric stove?
- Electric water heater has an engine heating coil?
- What is the charger capacity of the I/C?
- Single or twins?
- What is the footprint available for a larger house bank? Can you fit at least 4 GC's?

Manual load shedding of the water heater is easy, especially if it can be engine heated. KIS, Just leave the breaker off. Our twenty gallon holds hot water 2-3 days after a few hour run. The other breakers can be left on. No need to go through a rewiring project for a small job.

We have 6 GC's as a single bank and use that to start the single Perkins engine. The gen has a separate M24 battery as the backup plan if we ran the house bank dead. Our cruise up the east coast to NY Erie Canal and back to FL was no problem even with 2 of the GCs accidentally left disconnected (my bad).
Run the gen an hour in the morning on cruising days or one more time for an hour at dinner if the microwave is needed or its a lay day at anchor.

- The stove is electric, a simple two burner, 120V Kenyon (not an induction)
- The water heater is connected to the engine
- The charger side is 30 amps
- Single 160 perkins, I don't have the specs on the alternator, there is a receipt from it's replacement but looks stock.
- Plenty of footprint for additional batteries. The current location, which is on starboard, just forward of the starboard fuel tank has access above to service flooded battery types and the battery box is bulky, a thinner battery box would allow more batteries, there is room on the port side but no access above so maintaining flooded batteries would be difficult here.
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Old 05-06-2021, 08:16 AM   #12
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I would consider solar panels. They will extend the life of your batteries between recharging.
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Old 05-06-2021, 09:51 AM   #13
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- The stove is electric, a simple two burner, 120V Kenyon (not an induction)
- The water heater is connected to the engine
- The charger side is 30 amps
- Single 160 perkins, I don't have the specs on the alternator, there is a receipt from it's replacement but looks stock.
- Plenty of footprint for additional batteries. The current location, which is on starboard, just forward of the starboard fuel tank has access above to service flooded battery types and the battery box is bulky, a thinner battery box would allow more batteries, there is room on the port side but no access above so maintaining flooded batteries would be difficult here.
Your charger is small for a 4 or 6 golf carts batts. The stock alternator is about 60 amps which is ok for starting batts but small for a GC house bank. You will want to be able to recharge relatively fast for minimum gen run time. FWIW we have a 2000 watt Magnum I/C which has 100A charger and upgraded the alternator to 100A. Refrigerator is a small current draw but for a long time. So it is the biggest AH draw on the hook.

You won't be able to run your electric stove or microwave more than 2-3 minutes off the inverter so need to run the genny for that.
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Old 05-06-2021, 10:45 AM   #14
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Not one of your options, but you might consider firefly batteries for the house bank. Two group 31 batteries will give you 240 AH. You get lithium -like performance without the science/engineering project.

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Old 05-06-2021, 11:38 AM   #15
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Thanks again to all for the thoughtful input.

I will have to take another look at the firefly batteries, last time I looked into them they were similar in price to the current pricing of Lithium Iron Phoshate, I've heard there are some quality control issues with them as well but i need to research some more.

Because the stove is electric, I plan to run the generator for every cooked meal, I'm not looking to support the stove off an inverter but I will run the microwave off of it. The majority of our cruising is during the summer and I don't hesitate to crank up the genny to run Air conditioning as well, it is humid on the Chesapeake and my family has become pretty spoiled boaters, I grew up jumping in jellyfish invested water to cool off (in the snow, uphill, both ways, etc).

My wife and I have 3 kids so water and waste holding is a pretty limiting factor, generally only anchor out for 2 days in a row maximum. The Chesapeake is too silty for water makers and limited areas to treat and pump overboard, so tankage will be a limiting factor to days on the hook. The kids really enjoy a marina with a pool so we make it to a dock at least every 3 days, if I end up oversizing the battery and it only gets a full charge at the dock, it would be fine for now. Solar is a possibility, but between running the generator for meals and frequent docking, I don't see it as a priority this year.

Aside from correcting the AC system to limit the inverter to supporting the outlet outlet circuits, it will eventually need some other upgrades, I only have one 30 amp input so I have to manage loads even at the dock. I also have a good used 8kw genset sitting in my garage that will go into the boat as an upgrade to the single cylinder 3kw. When that goes in, I will probably upgrade the AC panel and add a second 30 amp shore connection. I was honestly surprised at the little MJDA, I had heard they were really load and obnoxious machines, but this one is set up well and I don't mind listening to it at all. The previous owner did a pretty thorough sound insulating effort and that must be helping.
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Old 05-07-2021, 08:19 AM   #16
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Thanks again to all, I think I'm going with option 4 but will incorporate as much feedback along the way.

The house bank will be four group 31 sized AGM batteries split between the existing battery bank location and across the engine room on the port side using equal length cables, being maintenance free, I can use tie down straps and just cover the battery terminals for protection. The two existing 27 lead acids and the box they are in, will move back next to the generator and support the generator, main engine and navigation electronics. The windlass and eventual thruster will feed off of the house/inverter bank to avoid voltage drops messing with my electronics. The alternator will feed the engine bank and a charging relay will go to the house bank. For now the inverter/charger will be retained but rewired correctly. The house bank will primarily be charge when docked or off of the generator when run for meals or Air conditioning.

I'll have a combiner between the two banks as well as a booster pack to start the generator. I suspect the health of the two 27 lead acid batteries, the were reportedly too week to start the engine earlier this spring when the charger was left on and a float switch was stuck on. They would be relatively cheap to replace if needed.

I think this approach will limit the need for a massive rewiring effort and allow for future upgrades later without too much rework. Eventually, I'd like to pursue LiFePO4 technology but the market for marine chargers to really benefit them is limited at this point, to my knowledge.
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Old 05-07-2021, 08:36 AM   #17
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I like option 4 with anything but lead acid batteries. I don't see much advantage in a house bank configured with lead acid batteries. Add a parallel switch between house and start bank for that time when your start bank has a dead batt and your house bank is healthy enough to start the genny. Been there.
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Old 05-07-2021, 11:26 AM   #18
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And I like Option 4 with flooded batteries. No shortage of opinions here.
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I like option 4 with anything but lead acid batteries. I don't see much advantage in a house bank configured with lead acid batteries. Add a parallel switch between house and start bank for that time when your start bank has a dead batt and your house bank is healthy enough to start the genny. Been there.
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Old 05-07-2021, 12:14 PM   #19
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And I like Option 4 with flooded batteries. No shortage of opinions here.
I've had good luck with flooded golf cart batteries in the past, my only hesitation in this case is that I would have trouble accessing half of the bank to check fluid levels. In my experience they are very good as long as you have your charger set up properly to avoid over charging them, but you need a proper setup charger for any battery type so that should really be held against them.

Catalinajack, you have probably seen my boat around your area before, the PO kept it in the boat shed at West River Yacht Harbor, named Graceland. It is now down at HHS.
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Old 05-07-2021, 01:23 PM   #20
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We kept our Mk III at West River Yacht Harbor... back in the '90s.

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