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

[john61ct]

Originally Posted by Q Xopa

If you want to risk the cheaper stuff no arguments from me.

Is this the same person that says you wont consider anything but UL rated wires etc?

Sometimes cheaper does not compromise the mission.

I do not consider wiring quality to be optional, more like a sound hull when passagemaking is the goal.

A DCDC unit or one the many alternative approaches, is just another gadget needs periodic replacing.

Again, I am not being critical of your own choice, just responding as I see fit to your continued questions.

[Q Xopa]

Originally Posted by john61ct

Sometimes cheaper does not compromise the mission.

I do not consider wiring quality to be optional, more like a sound hull when passagemaking is the goal.

A DCDC unit or one the many alternative approaches, is just another gadget needs periodic replacing.

Again, I am not being critical of your own choice, just responding as I see fit to your continued questions.

When you say my continued questions, if memory serves I think it was you that brought up the subject of a B2B being a waste. My question was asking for your reason for saying it.

Yes sure replaceable components. I guess everything in a boat is basicaly replaceble.

Im trying to minimise the interval of having to replace things.

Hopefully that should reduce the stuff I have to replace in out of the way places. I have a bit of experience in trying to rustle up stuff in out of the way places. The boat, mid refit, is in Panama and I am working currently in Pakistan. The range and quality in these places is not what is available in US, UK, Aus etc.

Saying B2B is a 'waste' kinda sounded a little critical. Maybe I mistook your meaning?

"Again, I try to avoid being a fan-boy for any device or technique.

I only felt compelled to defend their use **as an option** from mistaken overly general misconceptions"

I guess I also mistook your defence of B2Bs as an option as a little aggressive with your comments like 'blatant misinformation', 'refusing to pursue a little verification', 'willful' etc.

Appology accepted.

[john61ct]

I have never used the word waste in this thread, at least not since this post which is what you most recently challenged me on http://www.cruisersforum.com/forums/...ml#post2913468

Overkill is in many cases a compliment, when a low budget is not the main focus.

[Q Xopa]

Originally Posted by john61ct

I have never used the word waste in this thread, at least not since this post which is what you most recently challenged me on http://www.cruisersforum.com/forums/...ml#post2913468

Overkill is in many cases a compliment, when a low budget is not the main focus.

Yes sorry, my bad, youre correct 'overkill'. Youre also right that doesnt sound critcal at all.

No comment about anything else?

Thought so.

[mbartosch]

Originally Posted by Q Xopa

So how would you charge a Start battery if a B2B is a waste?

For me using an Alternator is a waste.

A Start batt is charged in minutes. If you use an Alternator you only get minutes use out of it then it just sits there doing nothing but spinning most of the time. Sounds like a wasted use, or lack of, resource to me. In my case it is a 110A 24V resource.

If you use a B2B, you can use that additional Alternator to feed the main house bank, which is where the majority of the charging is required.

In fact I have got my-
Alternators,
Solor controllers, and my
AC charger
All charging my Main house bank.

The only thing that charges my Start batt is the B2B. 60A is more than adequate for this.

A B2B isnt actually a charge 'source', it simply converts DC current from another source.

Agree 100 % with this post, and have an identical setup as detailed on my blog.

I don‘t see how the proposed B2B „choke point“ between charging sources and LFP bank can reliably work with multiple charging sources.
It basically requires a (working) LA bank for a) damping voltage spikes, protecting alternators from LFP cutoffs and b) for buffering charging sources output as already mentioned.
Without a steady input voltage on the source side of the B2B, this device will constantly reset on fluctuating input voltage or even not work at all (my Sterling B2B needs about 30 seconds from booting to charging)
The idea that multiple charging sources with different (possibly lower than 12 V such as an idling alternator) would contribute to charging through the B2B will not work IMO.

[john61ct]

All those factors are true with or without the B2B.

Multiple sources aren't in themselves an issue, with or without the B2B.

And that nitpick not relevant to the points in question anyway, you're using your Sterling DCDC as you like, feel free to do so.

Anyone wanting to devote more time and energy to this derailing discussion, it's well past the point of deserving a new thread with a specific scenario.

[tanglewood]

Originally Posted by john61ct

The continuous duty rated issue may be relevant to the health of the upstream power source, but still does not protect the LFP bank from its ability to draw current at too high a rate.

I think you fundamentally don't understand how this stuff works.


You seem to think that a given alternator will output more current when connected to an LFP bank than when connected to an LA bank. It's simply not the case. At full field, the alternator will output full rated current. Voltage will depend on the battery's SOC. Only once a voltage set point is reached will current reduce, and it will do so because the regulator reduces the field voltage.


The issue is how long any given alternator can run at full field/full output before it overheats or starts to accumulate wear and damage due to heat. A century or so of alternators charging LA batteries, typically start batteries, have taken advantage of the fact that the battery quickly reaches the regulation voltage, and the regulator can reduce output before things get toasty. So they are rarely called on to output at full capacity for any sustained length of time.


Now when people started using those same alternators to charge house batteries that were at a much lower initial SOC, and ran at full output for much longer than a typical start battery, accumulated heat started to be a problem. Enter the features of a Balmar to artificially reduce max output, or to monitor temp and reduce output based on that.


The only thing that's different with LFP is that the entire charge cycle is bulk and will run at full output if you let it.


So what's happened is that alternators that are historically intermittent duty rated have now been exposed as such, and one needs to artificially reduce their output to a continuous duty rating if you are going to run them at full output continuously.

[tanglewood]

Originally Posted by Q Xopa

So how would you charge a Start battery if a B2B is a waste?

For me using an Alternator is a waste.

A Start batt is charged in minutes. If you use an Alternator you only get minutes use out of it then it just sits there doing nothing but spinning most of the time. Sounds like a wasted use, or lack of, resource to me. In my case it is a 110A 24V resource.

If you use a B2B, you can use that additional Alternator to feed the main house bank, which is where the majority of the charging is required.

In fact I have got my-
Alternators,
Solor controllers, and my
AC charger
All charging my Main house bank.

The only thing that charges my Start batt is the B2B. 60A is more than adequate for this.

A B2B isnt actually a charge 'source', it simply converts DC current from another source.

I had my last boat set up the same way, for the same reasons.

[john61ct]

Originally Posted by tanglewood

You seem to think that a given alternator will output more current when connected to an LFP bank than when connected to an LA bank. It's simply not the case. At full field, the alternator will output full rated current

Sigh.

Only if there is a load device or battery demanding that current X.

Which if X is say 250A, is very unlikely to happen with even a very large bank of the highest-CAR **lead** chemistry.

But **very** likely to be the case, with even a pretty small LFP bank, as long as the **required** current-limiting functionality isn't "taming the dragon" somewhere between the two.

[tanglewood]

Originally Posted by john61ct

Sigh.

Only if there is a load device or battery demanding that current X.

Which if X is say 250A, is very unlikely to happen with even a very large bank of the highest-CAR **lead** chemistry.

But **very** likely to be the case, with even a pretty small LFP bank, as long as the **required** current-limiting functionality isn't "taming the dragon" somewhere between the two.

But why on earth would you have an alternator with more capacity than your LA bank can accept in bulk mode? If you did, it would mean that your charging system always go straight to absorb. It's a nonsensical example.


You're just not making any sense.

[john61ct]

Originally Posted by tanglewood

But why on earth would you have an alternator with more capacity than your LA bank can accept in bulk mode? If you did, it would mean that your charging system always go straight to absorb.

The point is that a stock alt cannot / should not be run at its rated (maximum peak) capacity.

Also why assume there is only one bank that needs charging? Or that they are all the same size?

A heavy-duty windlass or watermaker or even freezer plates may need more amps in use than you'd want to allow for charging your bank.

The point is not one limited scenario, it's clarifying the basic principles, which you keep insulting me about and then mis-state or over-generalize about yourself.

[jmh2002]

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

Pity

[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?

[CatNewBee]

Originally Posted by john61ct

Sigh.

Only if there is a load device or battery demanding that current X.

Which if X is say 250A, is very unlikely to happen with even a very large bank of the highest-CAR **lead** chemistry.

But **very** likely to be the case, with even a pretty small LFP bank, as long as the **required** current-limiting functionality isn't "taming the dragon" somewhere between the two.

this is a basic misunderstanding of the electric system as a whole.
John, you tend to think in ideal circuits. Real world circuits do have an inner resistance, and the current is limited by exactly this. Even IF a LFP 1000Ah battery CAN accept 3C, that means 3000A, no real world alternator could even deliver this in a sailing vessel. The limiting factor is the voltage of the alternator and its higher resistance. 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.

At no time this alternator will fry. If you have an empty AGM battery with one shorted cell and lets say 9V battery voltage, different story. 14.2V - 9V = 5.2V difference, current lets say again 60A, will be probably max possible current 120A, but lets stick to the 60A as an example, the alternator will burn 5.2V × 60A = 312W in heat, or even 624W. And this makes a serious difference.

LFP batteries stay at higher voltages, less voltage difference drives lower currents and creates less heat at the inner resistance.

There is no need for a special protection of the alternator when using LFP batteries - except for the possibility of a sudden disconnect by the BMS when over voltage protection kicks in.

And if the regulator is set properly to below 14.2V, there is little to do for the BMS to protect the LFP Battery either.

[john61ct]

Just flat out not true, with a stock alt setup.

If the alt circuitry / diodes aren't fried, what happened is the OCPand/or high temp protection circuitry of the stock regulator was well enough designed, and dropped the voltage to the point that in effect the LFP bank stops getting charged.

The goal is to **maintain the voltage precisely** at the desired setpoint

and handle the too-high demand from the LFP by scaling down the current.

Fitting an external regulator is one fix, the A2B or B2B solution is the other.