how to set up my bank to desired ah's

[GordMay]

Originally Posted by motion30

...The truth of the matter is 99% of the time you will run out of real estate for solar panels Before you have enough Power from solar .
What is the harm of having too much solar capacity?

Indeed, the more electricity you want to produce, the more solar panels you will need, as you want to collect as much sunlight as possible. Solar PV panels [and batteries] require a lot of space
The initial cost of purchasing a solar system is fairly high. This includes paying for solar panels, inverter, batteries, wiring, and the installation.

[Boatyarddog]

Originally Posted by captianjuan

I don't see why I cant design a system that will allow me dynamic movement within the capabilities of that system. for instance, if I buy say, the Victron Quattro, I should be able to upgrade my panels or add more so as to increase my charging capability. or maybe I could add say another 400ah battery to my bank to increase my power. or I could buy more effecicient panels, or I could build a big ass davits on my stern beam on my boat is 14 feet. I think Ill have a good amount of room for panels. what if I want to upgrade to induction stove. this all seems practical to me, but as I said, I am still in the learning phase.

Probably need to read up more on Lithium Batterys, charging them, and precautions in usage.
Boatyarddog

[fxykty]

Originally Posted by captianjuan

I want to build a 12v, 1200ah bank with the possibility to expand. should I use three 400ah cells or four, 300ah cells? could you tell me the pros cons of these set ups. im new to all this and appreciate any info you may have.

thank again.

As other posters have asked, you need to make clear whether you are talking about 12V drop-in batteries (which is what it sounds like), or whether you are talking about 3.2V cells that you plan on combining in some way to yield a 12V battery.

12V drop-in batteries have limits on how many batteries can be put in parallel to increase the capacity of a battery bank. That limit could be what sways your decision to 300Ah or 400Ah drop-in batteries. You will end up with either a 4P or 3P configuration, either of which you can extend subject to the limits on number of parallel batteries. With a parallel configuration make sure that the cables to the bus for each battery are the same length, otherwise the batteries will charge and discharge at different rates (the battery with the shortest cables will be used most).

If you are talking about building a 12V battery by combining individual 3.2V cells then you can use any size of cell you want. Some people feel that larger cells (more than 200Ah) are too fragile to use on a boat, while others report no problems with larger cells.

With lithium 3.2V cells it is always better to first wire the cells in parallel to get the Ah capacity you want, then to wire them in series to get the voltage that you want. That is because most (all?) BMS measure and control cells in series and typically have low limits on the number of cells/batteries in parallel they can control. Additionally, cells in parallel maintain their balance better. So a 4P4S or 3P4S configuration can be managed by a single BMS, while a 4S4P or 4S3P configuration would require four BMS (and I’m not sure that there is any external BMS that can manage 4 batteries in parallel).

Regarding solar and other charge sources, there is no “right” ratio for solar watts vs battery capacity when using lithium batteries, as they don’t care about partial state of charge (PSOC) and don’t have to be (and shouldn’t be) charged to 100% daily. Start with however much solar you can easily install, then see how that works for your cruising area and season. If you need more charging, consider more solar, a built in or portable generator, a high output alternator, and/or wind and hydro generators.

[StuM]

Originally Posted by fxykty

As other posters have asked, you need to make clear whether you are talking about 12V drop-in batteries (which is what it sounds like), or whether you are talking about 3.2V cells that you plan on combining in some way to yield a 12V battery.

He did make it clear in a subsequent post (#13):
"oh ok. I thought that when I wire up the cells since they would be wiring in series to increase voltage from int 3.2v individual and using 4 cells to achieve 12v"
So he was talking about cells, not batteries and was operating under a major misconception about how many cells he needed for 1200Ah @ 12V

[wingssail]

Originally Posted by motion30

...What is the harm of having too much solar capacity?

The harm is that you affect the boat in other ways (mostly bad ways).

Solar panels are heavy. You need to put them aloft, so that heaviness is up high where it affects the stability and pitching moment of the boat.

The frame work to support that load is also heavy, and a big array requires a massive support structure. (maybe on a Catamaran this is not an issue, the boat itself is massive).

So now you have a heavy structure supporting heavy panels, and probably you'll mount other stuff there (such as a dingy).

Windage. All of this, besides being heavy, and in a bad spot, adds windage.

OK, so the harm is it affects the boat's sailing ability and also affects the boat's handling in big seas, sailing or motoring.

I won't mention looks.

[Bowdrie]

Originally Posted by StuM

And importantly Amp hours are not absolute values- they depend on both Wattage and Voltage.
Watt hours are an absolute amount of energy.
The best way to understand series v parallel is to convert your battery capacity (Amp hours and Volts) to Watt hours.

This is the bottom line, an absolute measurement.

[captianjuan]

I am referring to making a battery from 3.2v cells. I am going to make a 1200ah bank with (im thinking) 400ah cells. Still not sure on sure on exactly how many amp hours ill want for the cells.
sounds like good advice. still trying to figure out how to arrange the banks and BMS so ill have to draw out what you suggested. thanks for the input.

Originally Posted by fxykty

As other posters have asked, you need to make clear whether you are talking about 12V drop-in batteries (which is what it sounds like), or whether you are talking about 3.2V cells that you plan on combining in some way to yield a 12V battery.

12V drop-in batteries have limits on how many batteries can be put in parallel to increase the capacity of a battery bank. That limit could be what sways your decision to 300Ah or 400Ah drop-in batteries. You will end up with either a 4P or 3P configuration, either of which you can extend subject to the limits on number of parallel batteries. With a parallel configuration make sure that the cables to the bus for each battery are the same length, otherwise the batteries will charge and discharge at different rates (the battery with the shortest cables will be used most).

If you are talking about building a 12V battery by combining individual 3.2V cells then you can use any size of cell you want. Some people feel that larger cells (more than 200Ah) are too fragile to use on a boat, while others report no problems with larger cells.

With lithium 3.2V cells it is always better to first wire the cells in parallel to get the Ah capacity you want, then to wire them in series to get the voltage that you want. That is because most (all?) BMS measure and control cells in series and typically have low limits on the number of cells/batteries in parallel they can control. Additionally, cells in parallel maintain their balance better. So a 4P4S or 3P4S configuration can be managed by a single BMS, while a 4S4P or 4S3P configuration would require four BMS (and I’m not sure that there is any external BMS that can manage 4 batteries in parallel).

Regarding solar and other charge sources, there is no “right” ratio for solar watts vs battery capacity when using lithium batteries, as they don’t care about partial state of charge (PSOC) and don’t have to be (and shouldn’t be) charged to 100% daily. Start with however much solar you can easily install, then see how that works for your cruising area and season. If you need more charging, consider more solar, a built in or portable generator, a high output alternator, and/or wind and hydro generators.

[captianjuan]

that would be the reason I posted asking the forum for some information. if you have a good book or website to check out, im all ears.


QUOTE=Boatyarddog;3644353]Probably need to read up more on Lithium Batterys, charging them, and precautions in usage.
Boatyarddog[/QUOTE]

[StuM]

Originally Posted by captianjuan

I am referring to making a battery from 3.2v cells. I am going to make a 1200ah bank with (im thinking) 400ah cells. Still not sure on sure on exactly how many amp hours ill want for the cells.

As stated earlier. If you go with 400Ah cells, you'll need twelve of them to get 1200Ah @ 12V nominal (actually 12.8).
That would be four x 400Ah @ 3.2V cells in series in each battery to get 400Ah @12.8V and three such batteries in parallel to get 1200Ah @ 12.8V (commonly abbreviated to a 4S3P battery bank.)

[thomm225]

Originally Posted by captianjuan

I want to build a 12v, 1200ah bank with the possibility to expand. should I use three 400ah cells or four, 300ah cells? could you tell me the pros cons of these set ups. im new to all this and appreciate any info you may have.
thank again.

Probably would depend on space available and how much weight you can handle and if you want all at once.

You could buy 3-300 ah batteries and that might be enough if you haven't figured your usage yet

The 300 ah Life PO4 in photo is $1169 @ 75 lbs

The 400 ah Life PO4 is $1799 @ 86 lbs

These look a lot easier than trying to do it with 3.2 volt cells

https://www.amazon.com/Ampere-Time-P...xpY2s9dHJ1ZQ==

https://www.amazon.com/Ampere-Time-L...dDbGljaz10cnVl

[Sand crab]

I'm confused, is the OP talking about building the bank from the little individual cells like the 18650?

[thomm225]

Originally Posted by Sand crab

I'm confused, is the OP talking about building the bank from the little individual cells like the 18650?

The OP was trying to figure all that out and now I believe he knows what he wants to do.

You rarely get straight forward answers here. Threads usually wonder around for a while until all the details slowly emerge......

To wire up all those 3.2 volt cells would be a royal PITA (unless you just love tinkering with that sort of thing) when you can just buy the 12 volt batteries all ready to go in either 300 ah size or 400 ah.

Then you just put them in parallel for the size bank you want.

https://www.power-sonic.com/blog/how...-and-parallel/

[Sand crab]

Yup, I saw a vid of some guys trying to repair battery banks and they mostly failed when the cells caught fire.

[StuM]

Originally Posted by Sand crab

I'm confused, is the OP talking about building the bank from the little individual cells like the 18650?

Probably prismatic cells something like this:





https://www.evworks.com.au/winston-400ah-lifepo4-cells




You won't get 400Ah out of a cylindrical cell

[mitiempo]

Originally Posted by thomm225

To wire up all those 3.2 volt cells would be a royal PITA (unless you just love tinkering with that sort of thing) when you can just buy the 12 volt batteries all ready to go in either 300 ah size or 400 ah.

Then you just put them in parallel for the size bank you want.

The op is much better with individual 3.2 volt cells in 3P4S configuration.

Drop in batteries should not be on a boat - fine for an RV.

I suggest the op contact Lythbattery for the cells. They are a major Calb distributor with prices that cannot be beat.

Lythbattery.com

Rita Sun is the sales manager.

Less than half the price of the same cells from any retailer.