Low Budget Lifepo4 Experiences anyone?

[Simi 60]

Originally Posted by CaptainRivet

Seriously, for example catnewbee 500+, me 350A, several just in this thread and in the one about electric cooktop…maybe several with Li bank should just put an amp clamp and measure what they really draw. If you have 220V you use it and if not your female crew will.
Simply everyone that has a decent 400AH+ Li house (below you just stress it too much and yes you can use a 200AH and electric galley) and does induction cooking and has a 12V system as the majority still does. Take a 3kw inverter, 12 V and an induction cooktop and you see 300A continuous. Do this on a Long Passage and you see 350A easily with all your other gear eg freezer….

Again, my victron multiplus 24v 5000/120 , which is what we have only outputs 100amps
We run a 500 litre fridge freezer
A 100 litre freezer
And 2 X 150 litre bar fridge, all 240v
Plus we have a 180 litre hot water system also 240v
And multiple PC, monitors, TVs, pumps also 240v

With all of that gear running we never see 100 amps of draw.
With just the refrigeration plus other systems on board we rarely crack 20 Amps
And the HWS comes on when the solar is smashing in amps so most of the time it's barely pulling anything.

. If you have 220V you use it and if not your female crew will.

I do have a female onboard, have done since day one and never had an issue.

[hzcruiser]

Originally Posted by CaptainRivet

I disagree it's safer. The 3 cells in parallel balance each other and always while in 3 separate batteries they separate especially when you draw high loads and In worst case the BMS interfere with each other causing that one battery can get nearly the full load.... The two 123Smart BMS interfered in an install I did

Well, in case any single cell fails in your setup you end up with a total failure of your whole battery system and the boat goes dark.

That's not what I would ever want to risk on my boat, thank you. And it's easy to avoid, too.

[Simi 60]

Originally Posted by hzcruiser

Well, in case any single cell fails in your setup you end up with a total failure of your whole battery system and the boat goes dark.

That's not what I would ever want to risk on my boat, thank you. And it's easy to avoid, too.

I agree
Waiting waiting waiting for our 24 cells to arrive
Formatted into 3 x 280ah @ 24v
Each with 200amp solid state contactor BMS and MRBF

[newhaul]

Originally Posted by Simi 60

Again, my victron multiplus 24v 5000/120 , which is what we have only outputs 100amps
We run a 500 litre fridge freezer
A 100 litre freezer
And 2 X 150 litre bar fridge, all 240v
Plus we have a 180 litre hot water system also 240v
And multiple PC, monitors, TVs, pumps also 240v

With all of that gear running we never see 100 amps of draw.
With just the refrigeration plus other systems on board we rarely crack 20 Amps
And the HWS comes on when the solar is smashing in amps so most of the time it's barely pulling anything.



I do have a female onboard, have done since day one and never had an issue.

Is that 100 amps draw at 24 volt or 240 volt ?
If 240 that 100 amps is 1000 amps at 24 volt .

[CaptainRivet]

Originally Posted by hzcruiser

Well, in case any single cell fails in your setup you end up with a total failure of your whole battery system and the boat goes dark.

That's not what I would ever want to risk on my boat, thank you. And it's easy to avoid, too.

That’s why I still have my 300AH legacy FLA starter/service bank in the stb hull.
2nd I can then dismantle the battery and make a 560AH 12V bank. 3rd my windlass and starter are 12V as all the other gear so if I would make a 24V house and the starter died I cannot switch to the 24V house
4th if one cell dies the other BMSs will most likely shut down the other 1 or 2 batteries too. Why because they mostly die during a high load event and something additional is wrong, not from just sitting around…experience

The Electrodacus BMS is very controlling, precise and with 5 digits behind the comma I can early dedect that a 3p block has a problem and check it in detail.

@simi: 12V systems is still the Norm and majority of the sailboats out there.
And I didn‘t wanna mess with a dual 12 and 24V system plus the fat 12V inverter came with the boat badly installed with the 40A in-line fuse that Chinese supplier delivered
You don‘t have to reinstall your whole system when adding a big inverter, you simply connect it directly to the Li house with a fuse and this should be a NH2 or better NH3 group 3 and not a Megafuse.

[CaptainRivet]

Originally Posted by newhaul

Is that 100 amps draw at 24 volt or 240 volt ?
If 240 that 100 amps is 1000 amps at 24 volt .

That is 2400W and with 24V at 120V/2400W or equal to 240V/1200W.
That shows Simi has no electric galley, the 2400W/120V is most likely the hairdryer or coffee machine.
Use a double burner electric stove and you also exceed your 200A

[CaptainRivet]

Originally Posted by Simi 60

Again, my victron multiplus 24v 5000/120 , which is what we have only outputs 100amps
We run a 500 litre fridge freezer
A 100 litre freezer
And 2 X 150 litre bar fridge, all 240v
Plus we have a 180 litre hot water system also 240v
And multiple PC, monitors, TVs, pumps also 240v

With all of that gear running we never see 100 amps of draw.
With just the refrigeration plus other systems on board we rarely crack 20 Amps
And the HWS comes on when the solar is smashing in amps so most of the time it's barely pulling anything.



I do have a female onboard, have done since day one and never had an issue.

You have a 120V inverter and 240V gear? How does that work?
How many watt and V does your heating element of a 180l boiler has, definitely not 750W
Your 500l fridge seems to have a magic compressor that creates cold from nothing…this only should use 15A in minimum

[newhaul]

Originally Posted by CaptainRivet

That is 2400W and with 24V at 120V/2400W or equal to 240V/1200W.
That shows Simi has no electric galley, the 2400W/120V is most likely the hairdryer or coffee machine.
Use a double burner electric stove and you also exceed your 200A

My induction cooktop is a single burner 1300 watt new newwave pic flex, 1500 watt Mr coffee and an 800 watt rice cooker, a 2512 trace inverter charger, and 250ah LFP bank with 200 amp Daly bms so an electric galley can be run on a small system but I also am a small (29 foot) boat with 12 volt refrigeration.

[goboatingnow]

I’m a bit confused by the opposing arguments

In my case economics dictate I use 100 Ah cells ( sweet spot pricing ) hence my 300Ah config is by definition 3P4S

I will have a cell based BMS and cell based balancing ( passive top balance )

Other then a faulty design ,I dont see any electronic reason why the BMS would interfere with each other. The bms will top balance the cells within the “ battery “ and since very cell bms is using the same set points , in effect all three batteries will top balance to the same point.

Any cell LVC or HVC will cause a bank disconnect. ( with alternator protection ) I’m currently deciding whether to simply disconnect the battery affected rather then the whole bank. ( clearly this has cost implications ) currently I don’t see much advantage in selective disconnect as an LVC event is likely to affect the multiple cells but it could provide an emergency zone of power for a short while ( till presumably all batteries suffer a LVC )

[Simi 60]

Originally Posted by CaptainRivet

You have a 120V inverter and 240V gear? How does that work?
:

It's a multiplus
The 120 is the charger

How many watt and V does your heating element of a 180l boiler has, definitely not 750W:whistling

1800watrs @ 240v but as I said, it is used when the sun is smashing in amps via the 2500w if solar or, Genset running.
Never done by battery alone

Your 500l fridge seems to have a magic compressor that creates cold from nothing…this only should use 15A in minimum:whistling

Probably does on start but drops back when running.
Fridges cycle, they very rarely all run together.

[CaptainRivet]

Originally Posted by Simi 60

It's a multiplus
The 120 is the charger


1800watrs @ 240v but as I said, it is used when the sun is smashing in amps via the 2500w if solar or, Genset running.
Never done by battery alone

Probably does on start but drops back when running.
Fridges cycle, they very rarely all run together.

I can just highly recommend to put a shunt on your minus 24V main busbar and really measure what’s really going through your whole system. It must be much more Amps then you post, if it’s what you see something fouls the measures.
You have a massive system and a lot of power hungry 240V stuff.
4 fridges/freezer 240V that switches on at the same time will definitely bring your inverter near its limits and your current above 200A and then the 1800W heater switches on powered by solar, here we go 300A+
Plus all the other gear…and it happens rarely but does and that’s what you minimum spec it for plus a safety margin.
In the galley no microwave, no mixers, icemakers or other 240V stuff…?
Everything that passes through your system does go through the main fuse that also protects the house bank, doesn‘t matter if it’s supported by solar and not going purely of your house bank.

I assume you have separate banks for your bowtrusters and anker windlass.

[CaptainRivet]

Originally Posted by goboatingnow

I’m a bit confused by the opposing arguments

In my case economics dictate I use 100 Ah cells ( sweet spot pricing ) hence my 300Ah config is by definition 3P4S

I will have a cell based BMS and cell based balancing ( passive top balance )

Other then a faulty design ,I dont see any electronic reason why the BMS would interfere with each other. The bms will top balance the cells within the “ battery “ and since very cell bms is using the same set points , in effect all three batteries will top balance to the same point.

Any cell LVC or HVC will cause a bank disconnect. ( with alternator protection ) I’m currently deciding whether to simply disconnect the battery affected rather then the whole bank. ( clearly this has cost implications ) currently I don’t see much advantage in selective disconnect as an LVC event is likely to affect the multiple cells but it could provide an emergency zone of power for a short while ( till presumably all batteries suffer a LVC )

Well that’s again theory and yes in real world interference between BMS happens. Why don‘t care because seperate BMS are a waste of money anyhow and only needed in drop in batteries (were cheap ones state you are not allowed to parallel them).
Especially in low budget DIY builds, see below.

Also your cells are not 100% equal, they have tolerances in eg internal resistance and the bigger they are the more the different cells will differ and separate in high loads putting the most current at the weakest cell.
If you parallel 3 cells and use 2 best and the worst this 3 will minimize the internal restistance tolerance as the load sees one cell with combined internal resistance consisting of 3 parallel cells.
If you put your 4 weakest cells in one battery with its own BMS and parallel the other 1 till x batteries with their own BMS this one weak battery will steer your whole bank down as the weak one will get the highest load.

Tried it with a 3p4S and 3 seperate batteries config with the same cells, the difference in capacity and max load was significant and the more significant the cheaper and low quality your cells are. So in low budget builds only that one fact determines its best to use a 3p4s config with one BMS.

Make one LVC and invest your saved money in a bigger FLA starter which buffers and works as service too till you fix your LI house in a disconnect event. Cheap hybrid FLA batteries for cooling trucks is a very good choice for that and choose one where you can check and refill water.

And have a look at Electrodacus, this really manages your cells for cheap 140Euro, opensource and I don‘t see why you need to reinvent the wheel and create your own BMS from the sofa. Adapt it to your needs if there is something that’s not like you want.

[goboatingnow]

Originally Posted by CaptainRivet

Well that’s again theory and yes in real world interference between BMS happens.

Also your cells are not 100% equal, they have tolerances in eg internal resistance and the bigger they are the more the different cells will differ and separate in high loads putting the most current at the weakest cell.
If you parallel 3 cells and use 2 best and the worst this 3 will minimize the internal restistance tolerance as the load sees one cell with combined internal resistance consisting of 3 parallel cells.
If you put your 4 weakest cells in one battery with its own BMS and parallel the your other 1 till x batteries with their own BMS this one weak battery will steer your whole bank down as the weak one will get the highest load.

Tried it with a 3p4S and 3 seperate batteries, the difference in capacity and max load was significant and the more significant the cheaper and low quality your cells are. So in low budget builds only that one fact determines its best to use a 3p4s config with one BMS.

Make one LVC and invest your saved money in a bigger FLA starter which buffers and works as service too till you fix your LI house. Cheap hybrid FLA batteries for cooling trucks is a very good choice for that and choose one where you can check and refill water.

Sorry your post suggests you don’t quite understand ohms law and battery discharge.

The fact is that a cell based bms , and I presume you understand how this works, each bms unit just measures its local cell. It can’t be affected by an adjacent cell

I mean I’m am electronics engineer with domain expertise here. I cant see what “ bms interference ) will occur.

In my case each cell bms contributes status to a central controller then it does the system wide HVC and lvc. So it’s both a cell level and system level bms.

Again I see no electronic means that would suggest 3 batteries with 4 series cells is different to a bank of 3P4S

Finally all batteries have equivalent output resistance.

Hence the lowest battery will supply the majority of the load until it’s terminal voltage falls then the discharge will split up depending on equivalent battery resistance.

At the end of the day it doesn’t really matter what set is supplying power , over time the usage will even out.

I agree keeping an FLA in the circuit but mind you my experience is it’s the FLA that fail way before Lithium’s

[CaptainRivet]

Originally Posted by goboatingnow

Sorry your post suggests you don’t quite understand ohms law and battery discharge.

The fact is that a cell based bms , and I presume you understand how this works, each bms unit just measures its local cell. It can’t be affected by an adjacent cell

I mean I’m am electronics engineer with domain expertise here. I cant see what “ bms interference ) will occur.

In my case each cell bms contributes status to a central controller then it does the system wide HVC and lvc. So it’s both a cell level and system level bms.

Again I see no electronic means that would suggest 3 batteries with 4 series cells is different to a bank of 3P4S

Finally all batteries have equivalent output resistance.

Hence the lowest battery will supply the majority of the load until it’s terminal voltage falls then the discharge will split up depending on equivalent battery resistance.

At the end of the day it doesn’t really matter what set is supplying power , over time the usage will even out.

I agree keeping an FLA in the circuit but mind you my experience is it’s the FLA that fail way before Lithium’s

There is so much totally wrong in your post Mr Electric engineer….
Sorry I am no domain expert, just a guy who installs in his private and Friends vehicles (car stereo, race cars, RV) with Li since 25years and LTO since 15 when nearly nobody even knew what that is…since 4 years my and buddy boats.

If you measure each cell in a 3p pack you just see the voltage and resistance of the whole 3p pack and not each individual cell, doesn’t matter if you measure at the pole of each cell or the whole pack. So individual cell Monitoring of paralleled cells is useless. You need to disconnect the cells to see individual cell voltages…

If you get different voltages between the paralleled cells and the whole 3p pack this means your connection between the cells is bad causing resistance and you measure the voltage drop, not the individual cells.


Would love to if the internal resistance even out over time, like this grade B cells would heal themselves but that doesn’t happen and is totally wrong. The opposite happens, the resistance grow even further apart the more the cell wear.

Do the test yourself between 3p4S and 3 individual batteries, best with grade B cells and apply 1C loads and measure…do at least 10 cycles and you will see yourself

True a FLA dies earlier under normal circumstances BUT a FLA shows clear signs of wear before it dies giving you a lot time to solve the problem. Besides an LTO a FLA is just the best to supply the short high current needs of a starter and you have it anyhow, so oversize and have a Backup…-

[goboatingnow]

I think we might have a failure of terminology

I’m using INDIVIDUAL CELLS . My question was given the only arrangement for me with 100Ah cells is too arrange them as 3P4S

A 3P4S arrangement is equivalent to three sets of 4 cells connected in parallel , ie three “batteries “ ( on the basis that a battery is a collection of cells )

Hence I fail to see how there is any practical difference between a bank arranged as 3P4S and 3 “ batteries “ of 4 cells in series.

Perhaps this might be called 4S3P

I’m not disagreeing with you that 3 cells paralleled then in 4 series is a good idea.

With my config every cell is capable of being individually monitored with interference.

In any parallel configuration load ( or discharge ) balances as a function of relative resistance. Resistance of a battery increases as it discharges hence load currents redistribute as SOC falls.

I’m not an electrical engineer I’m an electronics engineer ( that’s my specialist degrees ) with domain experience in handheld Li battery equipment.