Battery bank sizing with Lithium

[GILow]

Originally Posted by MVDarlin

Where is Oz?

Common abbreviation for Australia.

Quicker than typing The Land Down Under.

[Uncle Bob]

Originally Posted by MVDarlin

Where is Oz?

Well me old Darlin, it be the wee island below Indonesia.

[CaptainRivet]

Originally Posted by GILow

Hi Jenta, thank you for the detailed response.

All valid points, my numbers for power consumption were what I think (hope) is worst case. We went through all the sorts of things we cook and tried to imagine what power setting we’d need to cook them. Like you say, most of the time the system would be pulsing at a much lower duty cycle, as little as 30% for most stuff we think. (Hope.)

The real power hog was the paella, but what can I say, some comforts I’m not willing to surrender. So it forms our worst case power draw, full tilt for most of twenty minutes.

If you do get a moment to trial that battery isolation/sag test I’d be really keen to hear what you found.

On the issue of which battery, I’ve been reading lots, watching videos by a young lad on YouTube who seems to be quite credible, and I’m increasingly tending towards making my own. I found a good kit with Eve cells, claimed to be new grade A, from a reputable online retailer here in Oz.

I’m tending towards two 12v banks made from 280AH cells, each with a 200 amp BMS. (JBD). So that’s 7.2kWh, a lot more than I initially planned.

As you said, you prefer to roll your own, and a couple of credible posters here have expressed similar sentiments. Someone made a very good point about cable gauge in the prepackaged batteries and the young lad on YouTube showed just how much variation there is out there.

Fun journey, a bit of a learning curve.

That will be too small for your needs. I just helped my buddy boat to install 2P4S 12V 560Ah with the 280AH cells and joined them for Atlantic crossing and 4 weeks in Caribbean.
They have a Victron Multiplus 12/3000W and running that on full load while cooking with the induction hob at 2400W=200A constant (spikes are at 300A) the 560AH is at its healthy limits. When we added 50A from their 12V watermaker the sag’s tripped the low voltage alarm on BMS when below 40% SOC. The cells also start to drift more and the Electrodacus BMS has a hard time keeping it balanced, it’s managing it but close to the limits.
If you want that small capacity bank and have a lot solar/big alternators to recharge more and cycle often I would highly recommend to use Winston cells. That will work.
The 280AH EVE or Lishen or basen are storage cells with only 1C max on Price of AGM batteries but you shouldn’t use them above 0.5C frequently (you get what you pay for, great cells for the money) the Winston do 2C permanently.
I have 4P4s with 280AH cells in my cat so 12V 1120AH with 1600W solar and just in process of swapping over to 24V 2P8S with the cells as I have now bought used inverters 2x Studer 24V/3500W inverters=7kw permanent possible but I use 4,5kw peak while cooking.
In 280AH cells that 1120W or 4P4S what you need to run 4kw healthy longthermed, limit i see 3P4S 860AH that’s what I had before with a 12V/3000 Multiplus and a 3,5kw hf inverter via power assist running a total of 4,5kw. Like this the cells stay below 0.3C and won‘t drift much too and good is you have enough capacity for 3-5 rain days in a row. Added 4 more cells and go 24V as voltage drop is too high and running 500A is dangerous too, even my installation is good for 600A. 24V will bring all down to manageable 250A range.
I use step down converter 28V to 13,8V for all the 12V equipment. Like that you can compensate the voltage drop of your cabling, water pumps or compressor ran much smoother and more efficient innige end with 13,8V instead 12V…
Windlass motor I change to 24V.
I would only run Winston cells above 0.5C frequently.

[CarlF]

Lithium batteries have much lower internal resistance than lead acid. This resistance is the primary cause of what you are calling “sag”. In a lithium bank the resistance is mostly in the battery cables. Use large cables and short cable runs and you will have no appreciably sag.

Whether you go drop in or build your own, be sure the BMS can support the maximum load. Pushing the BMS to its limit can burn up the FETs in the BMS. So don’t cut it close - my BMS can support twice my maximum load.

And be sure to talk to your insurance company. Many will no longer insure boats with owner built lithium batteries.

[wholybee]

Originally Posted by CaptainRivet

That will be too small for your needs. I just helped my buddy boat to install 2P4S 12V 560Ah with the 280AH cells and joined them for Atlantic crossing and 4 weeks in Caribbean.
They have a Victron Multiplus 12/3000W and running that on full load while cooking with the induction hob at 2400W=200A constant (spikes are at 300A) the 560AH is at its healthy limits. When we added 50A from their 12V watermaker the sag’s tripped the low voltage alarm on BMS when below 40% SOC. The cells also start to drift more and the Electrodacus BMS has a hard time keeping it balanced, it’s managing it but close to the limits.
If you want that small capacity bank and have a lot solar/big alternators to recharge more and cycle often I would highly recommend to use Winston cells. That will work.
The 280AH EVE or Lishen or basen are storage cells with only 1C max on Price of AGM batteries but you shouldn’t use them above 0.5C frequently (you get what you pay for, great cells for the money) the Winston do 2C permanently.
I have 4P4s with 280AH cells in my cat so 12V 1120AH with 1600W solar and just in process of swapping over to 24V 2P8S with the cells as I have now bought used inverters 2x Studer 24V/3500W inverters=7kw permanent possible but I use 4,5kw peak while cooking.
In 280AH cells that 1120W or 4P4S what you need to run 4kw healthy longthermed, limit i see 3P4S 860AH that’s what I had before with a 12V/3000 Multiplus and a 3,5kw hf inverter via power assist running a total of 4,5kw. Like this the cells stay below 0.3C and won‘t drift much too and good is you have enough capacity for 3-5 rain days in a row. Added 4 more cells and go 24V as voltage drop is too high and running 500A is dangerous too, even my installation is good for 600A. 24V will bring all down to manageable 250A range.
I use step down converter 28V to 13,8V for all the 12V equipment. Like that you can compensate the voltage drop of your cabling, water pumps or compressor ran much smoother and more efficient innige end with 13,8V instead 12V…
Windlass motor I change to 24V.
I would only run Winston cells above 0.5C frequently.

I disagree, and think he has enough. I make do with a 300Ah Lithium bank with 120A Overkill Solar BMS, and induction cooking. 2400W ?!? Holy cow. My hob only goes up to 1500W at its highest setting, and I only ever run it at 900W because 900W will boil water faster than propane. 900W is only 65A, and then only until it gets to temp and then it drops to about 20A. It is plenty unless you have a huge cast iron wok. 2400W would be running 3 hobs at once, 2 at max power, and it is pretty easy to not ever do that. My propane stove (which is still installed) only has 2 hobs. I've never wished for 3.

The actual power needed is related to the mass of the pan. Heavy cast iron requires more power to heat than a thin pan designed for induction cooking. And apparently the quality of the cooker makes a difference. When I boil water I don't see the water boil in rings like some report, and it seems to do a good job at regulating current down when it is at temp. I use a nuwave which was not expensive.

[GILow]

Originally Posted by CaptainRivet

That will be too small for your needs. I just helped my buddy boat to install 2P4S 12V 560Ah with the 280AH cells and joined them for Atlantic crossing and 4 weeks in Caribbean.
They have a Victron Multiplus 12/3000W and running that on full load while cooking with the induction hob at 2400W=200A constant (spikes are at 300A) the 560AH is at its healthy limits. When we added 50A from their 12V watermaker the sag’s tripped the low voltage alarm on BMS when below 40% SOC. The cells also start to drift more and the Electrodacus BMS has a hard time keeping it balanced, it’s managing it but close to the limits.
If you want that small capacity bank and have a lot solar/big alternators to recharge more and cycle often I would highly recommend to use Winston cells. That will work.
The 280AH EVE or Lishen or basen are storage cells with only 1C max on Price of AGM batteries but you shouldn’t use them above 0.5C frequently (you get what you pay for, great cells for the money) the Winston do 2C permanently.
I have 4P4s with 280AH cells in my cat so 12V 1120AH with 1600W solar and just in process of swapping over to 24V 2P8S with the cells as I have now bought used inverters 2x Studer 24V/3500W inverters=7kw permanent possible but I use 4,5kw peak while cooking.
In 280AH cells that 1120W or 4P4S what you need to run 4kw healthy longthermed, limit i see 3P4S 860AH that’s what I had before with a 12V/3000 Multiplus and a 3,5kw hf inverter via power assist running a total of 4,5kw. Like this the cells stay below 0.3C and won‘t drift much too and good is you have enough capacity for 3-5 rain days in a row. Added 4 more cells and go 24V as voltage drop is too high and running 500A is dangerous too, even my installation is good for 600A. 24V will bring all down to manageable 250A range.
I use step down converter 28V to 13,8V for all the 12V equipment. Like that you can compensate the voltage drop of your cabling, water pumps or compressor ran much smoother and more efficient innige end with 13,8V instead 12V…
Windlass motor I change to 24V.
I would only run Winston cells above 0.5C frequently.

Do you know, you would have saved yourself a whole load of typing if you’d read the question.

[CaptainRivet]

Originally Posted by GILow

Do you know, you would have saved yourself a whole load of typing if you’d read the question.

Thank you for that inspiring post. Read again you obviously don‘t even know what you asked…
Short answer you cannot cook your paella 20min full blown peak load on a 5kw inverter as if 2x280AH if they are at 40%SOC the voltage cuts off and inverter is off.
Read my post again it’s exactly what you asked in #1 „sag at peak power with inverter and needed size of battery bank“ and that only running a 3kw inverter on the Eve cells, not the 5kw one and told you real life experience with these cells. not your sofa calculations based on assumptions and datasheets. But well ignore it and pay the lesson…

=> the voltage sag on peaks with a 3kw inverter drawing 2400W at 40%SOC with 560AH (much higher then your planned capacity) is that high that the BMS low voltage shutoff was tripped =>so very high
And that Multiplus is 40cm away from the battery with very short 4x70sqmm2 cable, the sag is not the cabling and MUltiplus is a very good inverter.

Please buy 280AH EVE and the 5kw Quattro and give it a blast, you will pay your lesson

[CaptainRivet]

Originally Posted by wholybee

I disagree, and think he has enough. I make do with a 300Ah Lithium bank with 120A Overkill Solar BMS, and induction cooking. 2400W ?!? Holy cow. My hob only goes up to 1500W at its highest setting, and I only ever

run

it at 900W because 900W will boil water faster than propane. 900W is only 65A, and then only until it gets to temp and then it drops to about 20A. It is plenty unless you have a huge cast iron wok. 2400W would be running 3 hobs at once, 2 at max power, and it is pretty easy to not ever do that. My propane stove (which is still installed) only has 2 hobs. I've never wished for 3.

The actual power needed is related to the mass of the pan. Heavy cast iron requires more power to heat than a thin pan designed for induction cooking. And apparently the quality of the cooker makes a difference. When I boil water I don't see the water boil in rings like some report, and it seems to do a good job at regulating current down when it is at temp. I use a nuwave which was not expensive.

Cooking for 4 persons, pot and pan made for induction, 3500W cooktop with one burner 2000W, the other 1500W. Good induction Hob, used the same for 3 years on my mono.
Boiling pasta on one and making the sauce on the other…standard use case and the limiter is the 3000/12/16 Multiplus delivering max 2400W.
Nuwave are Good but not available in 230V in the good 1800W 2 burner version.