Merged LiFeYPO4 1000Ah Winston prismatic cells and all electric galley...

[CatNewBee]

Originally Posted by dooleedooroo

Thank you for many people really interested in this B2B discussion. But try to focus on the more specific situation, here is my reason why I am interested in B2B

1. I am planning to buy new Catamaran, So my Starter/House batteries are brand new AGM as well as alternators. And not planning to order the generator.

2. Trying to DIY to add Lithium bank and solar.

3. Planning to use Solar as primary charging source, but need engine as my secondary charging source.

4. So I am looking for most inexpensive and safe option and heard about using b2b between AGM house to lithium and control that B2B.

5. I am guessing that B2b should check both Lithium and house bank and decide the charging.

6. Any recommendation on B2B for this case or any other idea on this specific situation?

B2B charger have different features based on model and manufacturer.
There are more expensive units, that can be programmed to protect the start battery from discharging by keeping the input voltage at 12.8V and using / transformin anything above to push a charge current into the house bank. In ideal condition they will use all available energy output of the alternator, limiting factor is only the b2b max Amps specification.

If you have a large alternator with Amps out 》charge current start battery + max current B2B charger, the alternator will not run under full load and will remain cool.

If you have a small alternator with Amps 《 Max Amps B2B charger, it will run all the time at full capacity and the B2B charger will not reach its maximum output, it will be the same when you connect the LFP directly, probably you will have a slightly higher current then, because no losses by heat in the omitted B2B charger. The ONLY advantage then is, you have a controlled maximum Voltage, regardless of the rpm.

I cannot recommend you a particular device, because I am not using them. There are other ways to reach the same goals. There are devices from all brands on the market, mainly to push highest possible current from an alternor to a house bank, even when the engine is idling. They are usually not meant to protect the alternator from overheating. Victron, Mastervolt, Votronic, Sterling to name a few...Some even can trick the CAN bus to disable eco modes in newer vehicles and force the alternator do deliver power.

You will need one B2B charger per engine / alternator.

[CatNewBee]

Originally Posted by jmh2002

CatNewBee's awesome thread appears to have been hijacked...

Pity

Thank you for the credits.

Well, the system was discussed at the first few posts, and it is working, so there is not much to add to the topic from my side. Usually others have different approaches and goals, it ends always in a LFP discussion unrelated to the galley and the daily usage of the harvested / stored energy. I wanted to show what is already doable.

But I guess, it is OK when there are discussions about general topics, it is a refresh for many on electricity basics and helps demystify the LFP environment, it is not that different to other battery technologies as many think.

[tanglewood]

Originally Posted by dooleedooroo

Thank you for many people really interested in this B2B discussion. But try to focus on the more specific situation, here is my reason why I am interested in B2B

1. I am planning to buy new Catamaran, So my Starter/House batteries are brand new AGM as well as alternators. And not planning to order the generator.

2. Trying to DIY to add Lithium bank and solar.

3. Planning to use Solar as primary charging source, but need engine as my secondary charging source.

4. So I am looking for most inexpensive and safe option and heard about using b2b between AGM house to lithium and control that B2B.

5. I am guessing that B2b should check both Lithium and house bank and decide the charging.

6. Any recommendation on B2B for this case or any other idea on this specific situation?

This can be a good application for a B2B charger, but I would use it to charge the start battery from the house battery, not the house battery from the start battery.


Connect your chargers directly to the house bank. That way they can deliver full output without being restricted by the capacity of the B2B.


And then you can use an even lower capacity B2B to recharge the start batteries because they will need very little to recharge.


All this of course assumes that your charging sources can be programmed for LFP charging, but most modern devices can, so it shouldn't be a problem on a new boat.

[hzcruiser]

Originally Posted by CatNewBee

this is a basic misunderstanding of the electric system as a whole.

[...] there will be simply a voltage drop from the 14.2V output to the 13.4V battery voltage and th difference of 0.8V × lets say 60A output = 48W will be heat in the alternator burned by its inner resistance, that will be vented away by the fan or the air around.

[...]alternator will burn 5.2V × 60A = 312W in heat, or even 624W. And this makes a serious difference.

You've got a great setup there, CNB, and I've already expressed that some time ago. You also show a very good understanding of electricity and and electronics. However, I'm sorry but I have to question your statements above.

Where is this notion that the alternator is "burning some Volts x Amps in heat" coming from?

From my memory, the alternator should be treated as a _current_ source, as such its terminal voltage could be anything, even close to 0 V. Any voltage and current combination is a, may I say, "delicate" _balance_ between the current being produced by the source and the rest of that system.

An empty batt will "drag down" the voltage while absorbing all the available current whereas a full batt causes the voltage on the alternator, the wiring and the batt to rise until the regulator in the alternator reduces the field current in order to limit the voltage. The regulator is not burning voltage or dropping voltage, it's reducing the power being produced by the alternator all the way to zero, in which case the voltage is stable at whatever the batt voltage is at that time.

[Q Xopa]

Originally Posted by tanglewood

This can be a good application for a B2B charger, but I would use it to charge the start battery from the house battery, not the house battery from the start battery.


Connect your chargers directly to the house bank. That way they can deliver full output without being restricted by the capacity of the B2B.


And then you can use an even lower capacity B2B to recharge the start batteries because they will need very little to recharge.


All this of course assumes that your charging sources can be programmed for LFP charging, but most modern devices can, so it shouldn't be a problem on a new boat.

Agreed, thats exactly what I am doing. Using a B2B to charge my start batt from the House bank. Others have remarked it is 'Overkill' but I am quite happy with it.

[CatNewBee]

Originally Posted by hzcruiser

You've got a great setup there, CNB, and I've already expressed that some time ago. You also show a very good understanding of electricity and and electronics. However, I'm sorry but I have to question your statements above.

Where is this notion that the alternator is "burning some Volts x Amps in heat" coming from?

From my memory, the alternator should be treated as a _current_ source, as such its terminal voltage could be anything, even close to 0 V. Any voltage and current combination is a, may I say, "delicate" _balance_ between the current being produced by the source and the rest of that system.

An empty batt will "drag down" the voltage while absorbing all the available current whereas a full batt causes the voltage on the alternator, the wiring and the batt to rise until the regulator in the alternator reduces the field current in order to limit the voltage. The regulator is not burning voltage or dropping voltage, it's reducing the power being produced by the alternator all the way to zero, in which case the voltage is stable at whatever the batt voltage is at that time.

Well, yes and no.
Tte alternator is a copper coil, ithas an inductivity and a resistance, the regulator is usually a device that limits the field current based on the terminal voltage. It is not an ideal current source so.

You can replace the symbol of an alternator by a current source in series with an resistor, the voltage for the Regulator is measured behind this resistor, then a small resistor in series representing the wiring, and then the battery as a voltage source with 0 Ohm resistance in series with the inner resistance of the battery. Along the current path you can measure the voltage drops at each point.

The regulator will try to power up the coil as long as the terminal voltage on the alternator output is below the 14.2 setpoint, however, the Alt is not an ideal current source, tho there is a limit based on the resistance / impedance of the coil, frequency etc. On an open circuit there will be a Voltage with no current, on a short circuit there would be voltage 0 and the maximum current. In between by applying a variable resistive load there is a non-linear curve of voltages and respective currents what you can use to calculate the inner resistance of the alternator at each set point and frequency (rpm).

When a current flows through something, there is a voltage drop, Voltage drop divided by current gives you the resistance, Voltage drop multiplied by the current gives you the power transformed in heat by this something. It can be a wire, a light bulb, a motor, a heater, an LED, a fuse, a switch contact, a plug...

In all electric circuits this is the source /reason when you noticed increased temperature.

In an IDEAL alternator made of supra-conductors there will be zero resistance, no voltage drop, no heat losses. Not feaseable yet.

[dooleedooroo]

Originally Posted by tanglewood

This can be a good application for a B2B charger, but I would use it to charge the start battery from the house battery, not the house battery from the start battery.

Connect your chargers directly to the house bank. That way they can deliver full output without being restricted by the capacity of the B2B.

To connect my alternator directly to the Lithium, I heard I need external regulator and also alternator auto-disconnect when the Lithium is fully charged.

I was thinking that if I go with b2b to charge lithium, I can simply insert b2b and lithium in between the current AGM battery and Load panel. Seems to be very simple and easy job. And only thing I need is b2b just big enough for alternator output.

[CatNewBee]

Originally Posted by dooleedooroo

To connect my alternator directly to the Lithium, I heard I need external regulator and also alternator auto-disconnect when the Lithium is fully charged.

I was thinking that if I go with b2b to charge lithium, I can simply insert b2b and lithium in between the current AGM battery and Load panel. Seems to be very simple and easy job. And only thing I need is b2b just big enough for alternator output.

Yes, that is doable.

[Q Xopa]

Originally Posted by CatNewBee

Yes, that is doable.

Yes doable, hopefully.

But there is a risk and no back up.

Most people generally have all their chargers- set to a 'conservative' level.
Then a bit higher at still a safe level have a HVC (High Volt Cutoff). In case one of the chargers fail to stop at the correct voltage for any reason.
Considering the expence of LFPs most people are a bit cautious about protecting them.

[CatNewBee]

Originally Posted by Q Xopa

Yes doable, hopefully.

But there is a risk and no back up.

Most people generally have all their chargers- set to a 'conservative' level.
Then a bit higher at still a safe level have a HVC (High Volt Cutoff). In case one of the chargers fail to stop at the correct voltage for any reason.
Considering the expence of LFPs most people are a bit cautious about protecting them.

Sure, that is one part of the job of the BMS, besides keeping the cells balanced.

[tanglewood]

Originally Posted by Q Xopa

Agreed, thats exactly what I am doing. Using a B2B to charge my start batt from the House bank. Others have remarked it is 'Overkill' but I am quite happy with it.

What's "overkill" about it? Is it a really big charger? Mine was only 20A, but more than enough to maintain a start battery.

[Q Xopa]

Originally Posted by tanglewood

What's "overkill" about it? Is it a really big charger? Mine was only 20A, but more than enough to maintain a start battery.

There are apparently way smarter and more experienced people than me on here.

[aybabtme]

I've been reading the thread. I see it has moved onto holy wars and I'm sorry to hijack this great stride!

We're planning to live aboard, with an electric setup similar to CatNewBee (we even had the same idea about projector!). I'm currently planning my LFP bank. I just installed 915W of solar on my 37ft monohull. I wanted to throw some of my ideas here to see if I'm crazy.

This is my first boat, and I consider it my "testing boat" before moving onto what we want to be a big catamaran. It's meant to the boat where we learn how to cruise, how to do all these DIY projects, how to maintain a boat, etc. We're new-ish to boating in general, so it's our training platform. But we're ambitious people, so we like to try interesting things.

My strategy has been to only invest into expensive hardware if it can be moved to the next boat, and avoid doing too many expensive changes to the current boat's setup. With that in mind, I want to hookup as big an inverter as I can, so we can power induction stove, electric steam oven, espresso coffee machine, hair dryer, water heater, water boiler... without having to worry about anything. Hell, running a TIG welder off the inverter is something I'm half seriously considering. But all the inverters in that power range are at least 24V. So I thought I would setup my design this way: make a separate bank to power the heavy loads, at 24V, and leave the current 12V AGM bank alone to avoid having to mess with the starter, the alternator or change everything to bespoke 24V.

Device wise, I'm currently aligned for:
- Solar: Victron 100/30 configured at 24V for the 915W of solar. This MPPT controller can handle 915W at 24V, but not as much at 12V.
- Inverter: AIMS 24V 6000W pure-sine inverter charger. Not sold on this manufacturer, but the specs (peak at 18kW) would fit the TIG welder dream, and their inverters are cheap-ish. Otherwise was considering the Magnum MSH4024. Any reason for the Victron Quattro? How would they compare to the Magnum? Note that I'd be okay with inverter-only instead of the combo. I doubt I'll need shore power charging.
- BMS: haven't settled one yet. The REC Q Active is for 4s only, and I'm looking at a 8s bank for 24V. Considering buying a Batrium WatchMon4 with 8s BlockMon, but I don't know how much I trust these things with the 3D printed enclosure. However, parts of me likes the "hackable" feel of it.

I'm assuming that the current 12V AGM bank will continue on having very small loads applied to it, but should remain charged to run lights and start the diesel. I don't worry too much about charging it, it'll have the alternator. I plan on leaving the alternator as is, to minimize changes to the boat, which means the alternator wouldn't charge my LFP bank. I'm assuming that this isn't a problem, since I have plenty of solar and I don't think the alternator will make a big difference. I'd like to avoid running the diesel as much as possible, and keep the 12V bank topped off with a Sterling B2B, taking 24V from the LFP bank and charging the 12V AGM bank as needed.

And then, when I move to "next boat", I'd take the inverter, the LFP bank, (maybe) the solar, and the B2B charger with me, leaving behind the 12V AGM bank along with the alternator and everything unchanged, as it was when I first got the boat.

So, is this crazy? Should I do something different?

[rom]

The way I see it:
1. 12V for such high amp loads (300+A) sucks because of those monster cables

2. 24V is much better of course but switching everything to 24V takes time & money
3. Having both 12 & 24V adds complexity and lowers reliability

FWIW I stayed 12V and ended up with 2x 3000W 12V victron multiplus working in parallel, high power & redundancy. I would love to do it all again in 24V, but didn't have the time & money when I started the conversion.
Good luck with your project!

Originally Posted by aybabtme

But all the inverters in that power range are at least 24V

[Q Xopa]

Originally Posted by aybabtme

I've been reading the thread. I see it has moved onto holy wars and I'm sorry to hijack this great stride!

We're planning to live aboard, with an electric setup similar to CatNewBee (we even had the same idea about projector!). I'm currently planning my LFP bank. I just installed 915W of solar on my 37ft monohull. I wanted to throw some of my ideas here to see if I'm crazy.

This is my first boat, and I consider it my "testing boat" before moving onto what we want to be a big catamaran. It's meant to the boat where we learn how to cruise, how to do all these DIY projects, how to maintain a boat, etc. We're new-ish to boating in general, so it's our training platform. But we're ambitious people, so we like to try interesting things.

My strategy has been to only invest into expensive hardware if it can be moved to the next boat, and avoid doing too many expensive changes to the current boat's setup. With that in mind, I want to hookup as big an inverter as I can, so we can power induction stove, electric steam oven, espresso coffee machine, hair dryer, water heater, water boiler... without having to worry about anything. Hell, running a TIG welder off the inverter is something I'm half seriously considering. But all the inverters in that power range are at least 24V. So I thought I would setup my design this way: make a separate bank to power the heavy loads, at 24V, and leave the current 12V AGM bank alone to avoid having to mess with the starter, the alternator or change everything to bespoke 24V.

Device wise, I'm currently aligned for:
- Solar: Victron 100/30 configured at 24V for the 915W of solar. This MPPT controller can handle 915W at 24V, but not as much at 12V.
- Inverter: AIMS 24V 6000W pure-sine inverter charger. Not sold on this manufacturer, but the specs (peak at 18kW) would fit the TIG welder dream, and their inverters are cheap-ish. Otherwise was considering the Magnum MSH4024. Any reason for the Victron Quattro? How would they compare to the Magnum? Note that I'd be okay with inverter-only instead of the combo. I doubt I'll need shore power charging.
- BMS: haven't settled one yet. The REC Q Active is for 4s only, and I'm looking at a 8s bank for 24V. Considering buying a Batrium WatchMon4 with 8s BlockMon, but I don't know how much I trust these things with the 3D printed enclosure. However, parts of me likes the "hackable" feel of it.

I'm assuming that the current 12V AGM bank will continue on having very small loads applied to it, but should remain charged to run lights and start the diesel. I don't worry too much about charging it, it'll have the alternator. I plan on leaving the alternator as is, to minimize changes to the boat, which means the alternator wouldn't charge my LFP bank. I'm assuming that this isn't a problem, since I have plenty of solar and I don't think the alternator will make a big difference. I'd like to avoid running the diesel as much as possible, and keep the 12V bank topped off with a Sterling B2B, taking 24V from the LFP bank and charging the 12V AGM bank as needed.

And then, when I move to "next boat", I'd take the inverter, the LFP bank, (maybe) the solar, and the B2B charger with me, leaving behind the 12V AGM bank along with the alternator and everything unchanged, as it was when I first got the boat.

So, is this crazy? Should I do something different?

Apart from having a bigger boat what you are preposing sounds similar to what I have and in process of doing myself.

And yes I have a Tig happily running through a couple of paralled 24v 3000w inverters on my boat.

A couple of questions if I may. Are you only planning to charge your 24V batts from Solar? Or with shore power?

The reason I ask is from what I understsnd it sounds like you are planning on big loads on your 24v batts but not planning to use the alternators.

I undestand changing to 24v alternators is not a trivial exercise. And I appreciate trying to reduce engine running, which I dont disagree with either.

Anything is possible but to me a big Inverter feeding big loads is going to have to get charged some how. Do you have a plan for getting you batteries charged if you have a week of cloudy weather? Generator or shore power?

It sounds like your alternator, although you dont plan on using it much, cant charge your 24v batts.

Maybe another B2B1224? Atleast if you need to you could charge up your 24v batts using your Alternators via the B2B at 60A.

From the sounds of your 12v batt setup it will need very little charging.

I'm thinking most of us have our engines going coming into or out of an anchorage to have the alternator help the Windlass. Ie reduces voltage drop and helps the batts keep up with the Windlass current. For example my windlass is 24v 1200w, so 50A. I agree it is a good idea for them to be 24v. If it was 12v it would be 100A. Although not usually done with a boat of your size. But you stated your reasons so thats fine.

Also, I know AIMS Inverters are popular and quite reasonablly priced. But I dont think they are 'marine' rated. I know many do get used in marine applications. This is quite important for a few reasons. Without getting bogged down in lengthy explanations but for a start I would look into 'floating grounds'.