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Old 27-04-2019, 16:43   #1
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24V storage battery on a 12V vired boat??

Hi there,
I have a 12V wired boat: 2x 12V alternators, starter motors, autopilot etc etc.
I have 2x12V 450Ah battery connected in parallel giving me 900Ah.
I have several 220V appliances that I want to use.
I will have around 1600W solar to control.

I am having a hard time to find one (or two) inverters/chargers/solar controllers to handle the job on hand.

I can find High frequency inverter/chargers with MPPT controllers up to 3Kw, or low frequency up to 4kw, but this with no MPPT built in.

Also if I was to connect my batteries in series and get 24V, I can find 24V-3kW HF inverters that can be connected in parallel and get 6Kw or a single 24V LF that can output 6Kw.

I have been proposed several solutions and i have made some diagrams to better illustrate them. The most controversial was proposed by my battery supplier that tells me that i can still get 12V from one of the two batteries if I connect them in series without causing any damage, just keep an eye on them and swap the cables around every month or so to keep them balanced.

A last solution that is not on the diagrams is to use a 24 to 12V Step Down converter to keep a 12V battery in charge and supply 12V to all the boat 12V systems....

Confusing? I bet. I am going bananas.....

Any help to find a solution appreciated.
Attached Files
File Type: pdf Charging diagram 1x4Kwa.pdf (28.8 KB, 36 views)
File Type: pdf Charging diagram 2x3Kwa.pdf (29.8 KB, 27 views)
File Type: pdf Charging diagram 24V 6Kwa.pdf (28.8 KB, 31 views)
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Old 27-04-2019, 18:32   #2
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Re: 24V storage battery on a 12V vired boat??

With "solutions" that increase complexity and demand obscure equipment, have to ask, what exactly is the underlying issue you're looking to "solve"?

I do not see the specific problems requiring either going to a mixed 24 & 12V setup, nor seeking single monolithic controllers, inverters etc rather than a modular approach, having a number of more common smaller units.
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Old 28-04-2019, 01:23   #3
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Re: 24V storage battery on a 12V vired boat??

Quote:
Originally Posted by john61ct View Post
With "solutions" that increase complexity and demand obscure equipment, have to ask, what exactly is the underlying issue you're looking to "solve"?

I do not see the specific problems requiring either going to a mixed 24 & 12V setup, nor seeking single monolithic controllers, inverters etc rather than a modular approach, having a number of more common smaller units.
John,
The 12V/3Kwa inverters cannot be put in parallel, so I either have only one (not enough power) or if I get two, I need to split the 220V circuit (easily done) but I would only be able to use 1 inverter as a battery charger when connected to grid (very seldom). But i am not sure if the MPPT built in can be parallelled??
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Old 28-04-2019, 02:50   #4
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Re: 24V storage battery on a 12V vired boat??

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Originally Posted by spiv View Post
John,
The 12V/3Kwa inverters cannot be put in parallel, so I either have only one (not enough power) or if I get two, I need to split the 220V circuit (easily done) but I would only be able to use 1 inverter as a battery charger when connected to grid (very seldom). But i am not sure if the MPPT built in can be parallelled??

You can stick to 12V and use a victron quattro 5kW. You will need separate MPPTs, which I think is a better choice anyway. I wanted redundancy so I went for 2x victron multi 12V/3kW, working impressively well in parallel, both for converting and charging. Of course 12V is a pita for such high amperage, but 24V adds complexity and/or lots of modifications on the initial system. Out of curiosity, what 12V battery has 450Ah capacity and would weight about 140kg ???
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Old 28-04-2019, 08:48   #5
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Re: 24V storage battery on a 12V vired boat??

I must firstly ask, what are the loads on the boat at 220v that requires 6KW at any one time?
At 12v that is some 550Amps, like holding the starter motor engaged for an hour. Something will give, as the battery plates are likely to buckle and there is going to be an awful lot of heat generated.
Secondly, what battery capacity does the inverter maker require to support his piece of equipment?
Can you answer these 2 questions firstly?
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Old 28-04-2019, 08:53   #6
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Re: 24V storage battery on a 12V vired boat??

Short peak loads, a 1000Ah bank of high-CAR chemistry should be OK.

But yes increase the runtime and duty cycles the size needs to further increase.

Getting the hot tub up to the proper temp while running the clothes drier and all-electric galley at the same time?
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Old 28-04-2019, 09:02   #7
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Re: 24V storage battery on a 12V vired boat??

Why not live in a condo and have all the comforts that you want without the inconvenience of trying to have them on a boat. KIS.
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Old 28-04-2019, 09:15   #8
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Re: 24V storage battery on a 12V vired boat??

A Gillig transit bus typically has 2, 8D 12V bats and starts and runs at 28V with 12V for running lights and hang-on gadgets. They use a battery equalizer to keep the charge on the two series 8D's equal. Very nice Remy 270A 24V oil cooled alt. Powered by a fairly large engine system.
You might want to look at their system diagrams.
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Old 28-04-2019, 09:16   #9
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Re: 24V storage battery on a 12V vired boat??

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Originally Posted by stewie View Post
Why not live in a condo and have all the comforts that you want without the inconvenience of trying to have them on a boat. KIS.
Im doing a similar elec sys upgrade ATM. 2x 3kw Victron Inverters.
Im doing it mostly for my welder. But I am also slowly converting the galley.

Yes I have heard all the 'dishing' about condos bla bla. These are usually the same guys that want welding done.
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Old 28-04-2019, 09:24   #10
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Re: 24V storage battery on a 12V vired boat??

These sorts of loads are usually achieved using a 220v generator. Do you not have one?
What battery power does the inverter manufacturer recommend? For long life of a battery I would think that 15-20% of its capacity is enough to discharge for any period of time. That is about 80 amps at 12v or under a KW at 220v.
I don't understand where this out of balance in capacity and systems came from. Victron have a lot of information on their website for perusal and the download of their operating characteristics.
SOme equipment needs a sine wave inverter rather than a modified sine wave, and some equip,ent needs 10 times the power to start it -anything with an inductive starting load like fridges and microwaves.
You can run inverters and generators in parallel as long as they have the right electronics to go with them as these new all singing and dancing ones do have (at a price of course).
Do you need to run everything at the same time? Can you not add hot water to your jakuzi from your hot water system which I hope is not an immersion heater.
And you have 1600 watts of solar at 12v. Such large currents and heat to deal with.
If it were my boat I would firstly have a generator installed.
Secondly I would manage the use of electricity such that peak loads of 6KW are not required.
Thirdly, I would separate the control of the solars using perhaps 3 MPPT controllers in parallel.
Perhaps you have a 30m megayacht?
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Old 28-04-2019, 11:32   #11
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Re: 24V storage battery on a 12V vired boat??

Thank you to all those that made constructive comments.
To the others, please go and watch TV, you are not welcome on this thread.

I never said I want 6Kw of power at the same time nor for an hour.
My diagrams shows all the loads and no, I do not intend to turn them all on at the same time, and no, there is no jacuzzi in my diagrams.

Now, I do know of the Victron inverters, but cannot afford them, I have some much cheaper options, still manufactured by QA companies, so I am confident enough about them and they are all Pure Sine Wave.


Quote:
Originally Posted by rom View Post
I went for 2x victron multi 12V/3kW, working impressively well in parallel, both for converting and charging.......
... Out of curiosity, what 12V battery has 450Ah capacity and would weight about 140kg ???
My original want was two 3Kwa in parallel, but I cannot get them from my suppliers and the main reason was for redundancy.
My batteries are 450Ah "Traction" batteries as used on electric forklifts, designed to be flattened and recharged every day.
2V cells, 28Kg each +168kg x2=336kg a lot for a cat, but cannot afford Litium....

Quote:
Originally Posted by oleman View Post
A Gillig transit bus typically has 2, 8D 12V bats and starts and runs at 28V with 12V for running lights and hang-on gadgets. They use a battery equalizer to keep the charge on the two series 8D's equal. Very nice Remy 270A 24V oil cooled alt. Powered by a fairly large engine system.
You might want to look at their system diagrams.
Never heard of that and not quite understanding it, but I will Google it, thanks.

Lastly, I don't have a 30M megayacht and I do not want a genset (but might end up with a little silenced one for emergencies).
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Old 28-04-2019, 13:00   #12
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Re: 24V storage battery on a 12V vired boat??

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To the others, please go and watch TV, you are not welcome on this thread.
I was hoping you'd say that, I have pretty much the same "jacuzzi" setup
Quote:
Now, I do know of the Victron inverters, but cannot afford them, I have some much cheaper options, still manufactured by QA companies, so I am confident enough about them and they are all Pure Sine Wave.
Maybe you are looking at the Axpert MKS then. 2 friends of mine use it. One a boat, one on land. Both killed their batteries but I believe it is mostly by lack of knowledge and proper programming. Though I was not convinced with the setup parameters you should be able to get it about right. And the price is indeed so much lower than victron ! Anyway, if that is the brand you are looking at, I am pretty sure they offer a model with redundancy / parallel operation. I believe you should stay 12VDC, you will have a hard time with the big cables but the global system will remain simple and less expensive than a 12/24V system. I would go 24V if I was building the boat / electrical system from scratch or if I had lots of money to spend.
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