DC/DC or ArgoFet

[CaptainRivet]

Originally Posted by Britishsea

Thxs again very much for this info.

I was tempted by some cells from Battery Hookup (https://batteryhookup.com) which were advertised as 35amp hours cells that they claim are testing in house btw 36-38ah. So as you say, these are likley relabeled 40 ah cells.

So is it your opinion that by the time a LTO cell has lost 10 - 15% of its original rated capacity, its basically at or near end of life

Good point re. the windlass needing more capacity. There are times i have hooked something on the bottom (rock, cable, etc) that takes a while to finagle off of.

To avoid the expense of 80ah of LTO, I could put my windlass on my 280 ah LFP bank. It's rated for 1 C continuous loads (EVE 280). Unless that is a bad idea. I only use the windlass it when the engine is running, so that might be OK and the wire funs are shorter from my LFP bank, which is located under my nav seat. I also have an electric winch, which is used more intermittently, and might be better suited for 40ah LTO bank.

Britsea

Looks like these are new factory 40AH grade B that didn't pass the specs. If they really have 37-40Ah and you get delivered what the pics show thats a great deal
Would write them and ask precisely if they are used, salvage and rebadged or if they are new grade B 40AH derated.

No 10-15% is not an issue, new grade A have +/-5%. There are 40AH cells used and rebadged to 30AH out there and deliver 28AH. These were heavily used and assumed close to end but still have 3000-5000cycles left.
How they really degrade at the end is not known, only used d since 12 years widely in korea and they should last 40 years min if new and used properly. The used are from power storage or public buses and used permanently on the limits so - 10AH for that 7-10years long.... On a boat you never uso them near their limit permanently.

I have 840AH Lishen 272AH connected 3P6S.

Windlass on LFP house: no problem if your BMS can handle the extra current. To be honest with your setup i would just skip a starter bat completely and get 6 extra eve and make a 560AH house/starter. Backup cells and enough power. Simply your live.
The AGM you can keep as backup starter/house connected via a 50W solar panel and a small connector switch. Later replace with a cheap LFA if dead. They like to sit around fully charged no problem and the solar always keep it full. Like this no need to plug in anymore.

I have a cat DC-to DC 2x30A via LFA now because engine are new and carry the 115a Mitsubishi alternator, they can do 60A each. Mostly 1 engine runs so they maxed out, if both run i charge 60A too. My main source are real 1200W Bifacial solar, so I get around 100A charge in if sun is there, cloudy still 30-45A the whole day.
Final solution is skip the DCs and put regultors on alt and will use in STB the LifePo4 house as starter and windlass too, in BB 40AH LTO as starter. Simplify is the key. Just wanna get the lifepo4 right with all the security setup and get experience on my cat and LFA are 2 years old and i had 1 DC to DC lying around anyhow.

[s/v Jedi]

Originally Posted by Afrinus

This is actually what I ended up doing. No ArgoFET.
Instead I connect the FLA via a Cyrix Li-ct directly to the house bank (downstream of the Loadside Battery Protect).
My charging setup is set at 13.8 which will leave the FLA slightly undercharged, but I'm confident that would be ok.

I find your demonstration of confidence disturbing

No, it will not be okay. FLA needs to be charged to it’s absorption voltage or lifespan will be drastically reduced.

[Afrinus]

Originally Posted by s/v Jedi

I find your demonstration of confidence disturbing [emoji3]



No, it will not be okay. FLA needs to be charged to it’s absorption voltage or lifespan will be drastically reduced.

LOL [emoji1787]
Of course you're right. I'm OK with that while I'm not on shore power.
When on shore power, there is the Aux output from the Multi that charges the FLA.
On edit, I probably will add a small DC/DC to charge the FLA.

[Britishsea]

i wrote to seller. Still awaiting on a reply.

You are right that for the money, an additional 280ah of lithium would be the way to go, but I am a little space constrained. Also, I fear that 2p4s set up would cause imbalance problems, which would mean going to 24v volts system which would have its own set of issues....

[more]

Originally Posted by s/v Jedi

I find your demonstration of confidence disturbing

No, it will not be okay. FLA needs to be charged to it’s absorption voltage or lifespan will be drastically reduced.

and who care first 3 years under warranty,this is a problem of the producer of start battery not a customer. 60-80€ battery / 3 year 26€ /12 month +-2€ month for start battery.

[lmxr]

Originally Posted by Britishsea

I had to think about this for a bit, but you are right. These are very good points.

If i have this right, the Argofet goes directly to the LFP bank and the start battery. Also attached to the LFP bank is the DC-DC charger (as power source) to the start battery (DC_DC's charge output) so that the voltage is boosted up for the start battery to get the correct charge.

Powering the DC-DC from the LFP is one option indeed. Many DC-DC chargers have an 'enable' input, which can be connected to the ignition switch for example, which will prevent draining the LFP in case the LA starter shorts out (not likely, but if it does, one ends up with two dead banks...). An unused, extra positive output from a mains charger can in addition be used to control the enable (use two diodes to make an OR-port) such that the DC-DC is also enabled while shore power is available.

Only downside i can see is that when the DC-DC has charged the start battery and turn off, the Argofet will still be providing 13.9 - 14v to the start battery so charging will not fully stop. [...]

Good point, overcharging of the start battery should be prevented indeed. Would this situation be similar to the one where the house bank is traditional lead-acid, and therefore with higher voltages? That approach appears to work reasonably well, at least with flooded start batteries.

[CaptainRivet]

Originally Posted by Britishsea

i wrote to seller. Still awaiting on a reply.

You are right that for the money, an additional 280ah of lithium would be the way to go, but I am a little space constrained. Also, I fear that 2p4s set up would cause imbalance problems, which would mean going to 24v volts system which would have its own set of issues....

Just 2 cells parallel, if you perform a good top balance before assembly there won‘t be an imbalance, I run 3ps4 means 3 parallel.
You get imbalances but also in the series if you use them hard means regular draw of 0.6-1C. If you add more AH they share the load, means before you draw 1C=imbalances, with 2p afterwards you draw 0.5C = no imbalance.
Don‘t need to go 24V which has a greater chance of imbalance……..

[s/v Jedi]

Originally Posted by CaptainRivet

Don‘t need to go 24V which has a greater chance of imbalance……..

Cells in parallel works okay when the cells are properly matched but it will not outperform series connection which is superior by design and will keep better balance than parallel with equally matched cells.

When a new inverter/charger is being bought anyway, switching from 12 to 24 or even 48V makes a lot of sense if more battery capacity is wanted.

[CaptainRivet]

Originally Posted by s/v Jedi

Cells in parallel works okay when the cells are properly matched but it will not outperform series connection which is superior by design and will keep better balance than parallel with equally matched cells.

When a new inverter/charger is being bought anyway, switching from 12 to 24 or even 48V makes a lot of sense if more battery capacity is wanted.

Yes it’s the inverter where even 48V would be awesome but what keeps you from switching to a 24V house is all your high current legacy 12V equipment need to be changed too or if you keep that on the 12V starter then you have no backup in case either of them fail.
To change 12V starter, alternator, windlass and electric winch costs a lot, if you have a cat with 2 engines even more…my 2 engines are new, 12V windlass freshly overhauled, 12V electric whinch 1 year old when I bought the cat…so I stay 12V got a 12V 5kw inverter and put it with 2x120mm2 with 30cm cable length straight connected with a T3 fuse in each cable to the battery to avoid to upgrade and put this huge load on your main busbar. Not really big disadvantage compared to 24V inverter. Electrodacus BMS so the total current i don‘t care as it carries no current and switches the inverter off via the Remote on/off Switch if SOC is too low or an alarm disconnect event.

That’s the theory that Series is superior to parallel, with perfect quality and 100% identical cells that’s true. In practice it depends on chemistry and quality of each cell and what you can afford are good mass quality cells with quite some deviation of each cell. And then 1p8S =24V in series cells starting to drift more and sooner then 2p4S =12V but you need double cable diameter and voltage drop are bigger on 12V. This increases the more cells in parallel and the More current you draw. Less with LifePo4, more with LTO.

This is the biggest issue with LTO as you only get good and affordable 40AH cells and the 2,65V cell voltages is not really good to make a 12V battery as 5S is too less and 6S are 17-18V (perfect for a starter but not house) but 12 cells make a good 25-27V battery which is in the range 24V equipment can handle. But to reach sufficient capacity need to put 6p or 7p, so we are talking about min. 36 cells.
Even a 7P6S LTO doesn’t need a BMS if properly top balanced before assembly (even if you pull regularly 800A) but already a 1P12S does and a 3P12S needs a BMS with a very good active balancer. Know only the Electrodacus BMS (maybe REC but don’t know if it has an LTO setting) that can handle this as other limit the current. that’s why you use LTO because a small bank can handle high current permanently. You can easily connect a fully loaded 3.5kw inverter on a 12V 80AH or 24V 40AH LTO and eg cook with it daily.

[s/v Jedi]

Originally Posted by CaptainRivet

Yes it’s the inverter where even 48V would be awesome but what keeps you from switching to a 24V house is all your high current legacy 12V equipment need to be changed too or if you keep that on the 12V starter then you have no backup in case either of them fail.
To change 12V starter, alternator, windlass and electric winch costs a lot, if you have a cat with 2 engines even more…my 2 engines are new, 12V windlass freshly overhauled, 12V electric whinch 1 year old when I bought the cat…so I stay 12V got a 12V 5kw inverter and put it with 2x120mm2 with 30cm cable length straight connected with a T3 fuse in each cable to the battery to avoid to upgrade and put this huge load on your main busbar. Not really big disadvantage compared to 24V inverter. Electrodacus BMS so the total current i don‘t care as it carries no current and switches the inverter off via the Remote on/off Switch if SOC is too low or an alarm disconnect event.

That’s the theory that Series is superior to parallel, with perfect quality and 100% identical cells that’s true. In practice it depends on chemistry and quality of each cell and what you can afford are good mass quality cells with quite some deviation of each cell. And then 1p8S =24V in series cells starting to drift more and sooner then 2p4S =12V but you need double cable diameter and voltage drop are bigger on 12V. This increases the more cells in parallel and the More current you draw. Less with LifePo4, more with LTO.

This is the biggest issue with LTO as you only get good and affordable 40AH cells and the 2,65V cell voltages is not really good to make a 12V battery as 5S is too less and 6S are 17-18V (perfect for a starter but not house) but 12 cells make a good 25-27V battery which is in the range 24V equipment can handle. But to reach sufficient capacity need to put 6p or 7p, so we are talking about min. 36 cells.
Even a 7P6S LTO doesn’t need a BMS if properly top balanced before assembly (even if you pull regularly 800A) but already a 1P12S does and a 3P12S needs a BMS with a very good active balancer. Know only the Electrodacus BMS (maybe REC but don’t know if it has an LTO setting) that can handle this as other limit the current. that’s why you use LTO because a small bank can handle high current permanently. You can easily connect a fully loaded 3.5kw inverter on a 12V 80AH or 24V 40AH LTO and eg cook with it daily.

I did change from a 12V to a 24V house bank and find none of the problems you list as being relevant. 99% of all 12V loads are handled by a DC-DC converter. This leaves engine start, windlass and any electric winches to deal with, which is easily done so with my example setup, which I posted before, but attach here as well.

[CaptainRivet]

Originally Posted by s/v Jedi

I did change from a 12V to a 24V house bank and find none of the problems you list as being relevant. 99% of all 12V loads are handled by a DC-DC converter. This leaves engine start, windlass and any electric winches to deal with, which is easily done so with my example setup, which I posted before, but attach here as well.

Sorry thumbnail is very small,cannot get much…

How Do you operate the 12V starters, 12V windlass, 12V winch?
For/From your 24V house: You would need a 2x 300A 24 to 12V converter….expensive if they exist
From 12V starter: makes no sense
What do you do if your 12V starter bat breaks?
How do you charge your 24V house from the 12V alternator? Easiest fix, via 12V starter and Dc-to-DC charger 12-24V=> costs a fortune

[s/v Jedi]

Originally Posted by CaptainRivet

Sorry thumbnail is very small,cannot get much…

How Do you operate the 12V starters, 12V windlass, 12V winch?
For/From your 24V house: You would need a 2x 300A 24 to 12V converter….expensive if they exist
From 12V starter: makes no sense
What do you do if your 12V starter bat breaks?
How do you charge your 24V house from the 12V alternator? Easiest fix, via 12V starter and Dc-to-DC charger 12-24V=> costs a fortune

Open the thumbnail

[CaptainRivet]

Originally Posted by s/v Jedi

Open the thumbnail

I did with the phone
Now again with the 12.9 IPad, now I can see…
How do you start your engine if the 12V bat break? You can‘t
Backup if your 24V LifePo4 shuts off? You don‘t
You have 24V windlass, I am not…
You have 24V alternators, i am not…

I have:
Windlass 12V 114A
Winch 12V 75A
Alternator 2x12V 2x115A
Starter 2x12v 2x200A
Amp 6x100W, 12V 60A
Shorepower charger 2x12V 50A

I have 12 cells Lishen 272AH in 3P4S, capacity tested 12V 840AH bank.

How does this make sense to go to 24V house?
Just to save on 4 cables with 120qmm2 30cm long, 8 cable shoes and 2 Class T3 250A fuses?
No problem pulling 500A from a 840AH house, voltage drop from 30cm cable with t3 fuse is 0.1V, inverter is 120Euro more expensive in 12 then 24V.

The only advantage you can raise output voltage of the 24V to 12V converter to compensate for cable losses/voltage drop in the 12V part.

[s/v Jedi]

Originally Posted by CaptainRivet

I did with the phone
Now again with the 12.9 IPad, now I can see…
How do you start your engine if the 12V bat break? You can‘t
Backup if your 24V LifePo4 shuts off? You don‘t
You have 24V windlass, I am not…
You have 24V alternators, i am not…

I have:
Windlass 12V 114A
Winch 12V 75A
Alternator 2x12V 2x115A
Starter 2x12v 2x200A
Amp 6x100W, 12V 60A
Shorepower charger 2x12V 50A

I have 12 cells Lishen 272AH in 3P4S, capacity tested 12V 840AH bank.

How does this make sense to go to 24V house?
Just to save on 4 cables with 120qmm2 30cm long, 8 cable shoes and 2 Class T3 250A fuses?
No problem pulling 500A from a 840AH house, voltage drop from 30cm cable with t3 fuse is 0.1V, inverter is 120Euro more expensive in 12 then 24V.

The only advantage you can raise output voltage of the 24V to 12V converter to compensate for cable losses/voltage drop in the 12V part.

I have/had all the same gear you had… remember I had a 12V battery bank too. So let’s see:

Start engine when 12V battery breaks: I start with the 2nd start battery; surely you could see that in the diagram! Then there’s a shtf backup as well: a center tap on the 24V house battery: see the leftmost switch in the picture!

Backup when my house bank fails? I have a 2nd house bank as well as a 12 to 24V converter and a rather large 1875W solar array with 24V output.

I had a 12V windlass. I simply bought a 24V motor for it.

I have 12V alternators on engine and genset. They charge the 12V batteries. There are two 12-24V converters that charge the house bank from the alternator output.

You have a 12V winch? I have 4 massive 12V winches incl. the Lewmar 66 primaries. They simply run off the 12V.

Why you have 12 cells is beyond me because that would make a 36V battery. I did hear car manufacturers switching to that but I would keep it at 8 cells for 24V or 16 for 48V

You have a 12V shore power charger? Remember, I had 12V too. I still have a good as new Victron Quattro 3000 and a Xantrex 60A charger. I think I’ll keep the charger and sell the Quattro or use it at another project.

[Britishsea]

[QUOTE=CaptainRivet;3562825]. "Electrodacus BMS so the total current i don‘t care as it carries no current and switches the inverter off via the Remote on/off Switch if SOC is too low or an alarm disconnect event."

I am also using the Electrodacus. Seems a bit prone to corrosion in a marine environment, but hoping it will get through a couple of years until more BMS options are available or drop-in LFP becomes more sophisticated.

BritSea