LFP alternator charge, LA-dc2dc in which order

[wholybee]

Originally Posted by Ballsnall

I depends on what size auxiliary engine or specifically should matched to the alternator size. A 60A DC/DC charger would be too much for an 80A alternator where a 30A DC/DC would be about right. You could match a 60A DC/DC charger to a 125A alternator comfortably or as some like to do, use 2 X 30A DC/DC charges.
Oversizing the DC/DC charger will leave you with a flat start battery or even a fried alternator. If your going for maximum auxiliary charging then direct to house bank with a programmable regulator is the optimum way.

Something that doesn't make sense to me. If a 125A small case alternator can safely run at 60A continuously, then shouldn't a 70A or 80A alternator in the same case equally be able to? The cooling capacity is the same for all of them.

Different DCDC chargers are enabled different ways. The better ones have a voltage sense lead, and if the input voltage drops below a certain voltage (~13.8 typically) then it assumes the charge source is off, and stops charging without discharging the start battery.

[Ballsnall]

Originally Posted by newhaul

Actually a 60 amp unit would not be to big for an 80 amp alternator as long as you add extra external cooling . Afterall that is only 75% capacity and most can push 80% with minimal issues . Some on here run as big as 245 amp alternators. Which the 200 amp dc dc from sterling would be good for .

Now explain how a properly installed dc2dc charger would leave one with a dead start battery ?

Drawing a constant 60A from the start battery will flattened it very quickly if you are not inputting in excess of 60A. You need to account for recharging the start battery and as the alternator output varies with RPM so alternator output is variable and not always at max.

A 30A DC/DC charger is most optimal size for a stock 80A and if you don't do a lot of motoring 20A may be more appropriate.

Some on here run as big as 245 amp alternators.

If anyone running a high output alternator through a DC/DC charger to the house bank is doing it wrong. A DC/DC charger is a viable, cost effective and simple option for those with a stock alternator .

[newhaul]

Originally Posted by Ballsnall

Drawing a constant 60A from the start battery will flattened it very quickly if you are not inputting in excess of 60A. You need to account for recharging the start battery and as the alternator output varies with RPM so alternator output is variable and not always at max.

A 30A DC/DC charger is most optimal size for a stock 80A and if you don't do a lot of motoring 20A may be more appropriate.



If anyone running a high output alternator through a DC/DC charger to the house bank is doing it wrong. A DC/DC charger is a viable, cost effective and simple option for those with a stock alternator .

Sorry but that's not how dc dc chargers function it requires a voltage sensed from the alternator which for the Orion is 13.3 volts which signifies the alternator is running . Most others are the same or similar and or they have an ignition sense wire which energizes the dc dc when the ignition is in the engine run position .

[Ballsnall]

I understand that DC chargers only operate when the alternator is providing charge voltage, and I am talking about scenarios where the charging amps of the alternator are not at maximum output. Ie. entering & exiting harbours & marina's, anchoring, motor sailing etc etc. During these times when your engine is not at cruising revs your alternator is producing significant less amps but your 60A DC/DC is still out putting 60A continuous. So in situations where you are using low engine revs or intermittent engine use you are depleting your start battery.

[s/v Jedi]

There is a major difference between a dc-dc converter and a dc-dc charger:

The dc-dc converter takes an input dc source like for example 9V to 17V, which can vary, dip when a big load is switched on etc. and converts it to an output dc power source like for this example 13.2V which is a steady 13.2V even when the input is varying all over the place.
You use these to provide clean power to electronics or even the whole dc breaker panel etc.

The dc-dc charger is the same at the input side but it turns it into a smart charger that you can set to the correct profile like AGM, FLA, GEL, LFP etc. and it supports the familiar bulk, absorption and float stages.

For Victron Orion, the Smart versions are both of the above; you can choose this in programming. The dumb high power units are converters only and I’m not sure if they support the same ranges either.

The Smart versions also have automatic on/off algorithms where you can set them to only activate above a certain input voltage or even high tech alternator detection algorithms that support the new Smart Alternators that I think are only used on cars at the moment.

Another important feature is that the Smart Orions have a remote on/off switch. You can install two and switch one or both on, take one offline when motoring for long periods to keep the alternator cooler and more HP available etc.

Another important feature you have to make a choice for is to select an isolated or non isolated version. If the negatives of the two sides are interconnected, i.e. 12V negative is the same as 24V negative or start battery negative is the same as LFP house bank negative, then you don’t need an isolated version… but you can use one, just connect both negative terminals to the same negative busbar.
Here you need to check out the available models for each series as they differ.
I published a diagram for an isolated supply for powering electrics, which is the best example that requires an isolated version.

[s/v Jedi]

Let me add to this: I see a trend developing to install a dc-dc converter between batteries and dc breaker panel regardless of voltage used. Where 24V to 12V converters were used before, I now see installations with 12V house banks and 12V breaker panels, install 12V to 12V converters, which is not commonly done on boats… yet.

The advantages are clear: you get a stable voltage at the panel, like 13.2V even when the battery is down to 12.5 or 11.9 etc. or up to 14.6V during charging.

I can’t come up with many disadvantages for this other than the need to have a unit powerful enough to provide all power required, and a backup unit or bypass switch as well.

Large loads like a windlass or engine starter are normally wired around the breaker panel anyway so the power requirement isn’t that high I think. I think this will become in use on boats as well.

[Ballsnall]

Here we are discussing DC/DC chargers not converters such as the Victron Orion-Tr Smart 12/12-30A Non-isolated DC-DC charger. I would be interested in your opinion on the pros and cons of isolated v non isolated chargers in this situation.

Personally I don't see the need for the extra expense but I'm just a busted assed tradie and your knowledge vastly exceeds anything I could hope to obtain.

[s/v Jedi]

Originally Posted by Ballsnall

Here we are discussing DC/DC chargers not converters such as the Victron Orion-Tr Smart 12/12-30A Non-isolated DC-DC charger. I would be interested in your opinion on the pros and cons of isolated v non isolated chargers in this situation.

Personally I don't see the need for the extra expense but I'm just a busted assed tradie and your knowledge vastly exceeds anything I could hope to obtain.

The posts made in this thread clearly show that many do not realize the difference is there. Some even think it is another name for an ACR.

I did explain the isolated vs non isolated versions? There isn’t much more to it than that.

[CaptainRivet]

Originally Posted by wholybee

Something that doesn't make sense to me. If a 125A small case alternator can safely run at 60A continuously, then shouldn't a 70A or 80A alternator in the same case equally be able to? The cooling capacity is the same for all of them.

Different DCDC chargers are enabled different ways. The better ones have a voltage sense lead, and if the input voltage drops below a certain voltage (~13.8 typically) then it assumes the charge source is off, and stops charging without discharging the start battery.

Not all alternators are the same that have an equal rating. It depends what they are designed for.
Most alternators below 90A on marine engines are car alternators, made to top up a starter Batterie with high rpm (up to 8000rpm engine, alternator turn 16000) but no deep cycling batteries. They can typically do 50% of their rating max and 99% small case. Marine engine run low rpms, most till 3000 range. The next typical is alts for commercial high power drain purposes like cooling trucks which are reinforced with deep cycle charging capabilities but still run high rpm (eg the widespreaded 12V 115A Mitsubishi alternator) which can do 70 till 90% of their rating depending on rpms run.available in mostly small case but some also in large case available.
Then you have low rpm alternator for low rpm engines for high power and/or deep cycling, they can do 100% of their rating continuously. Small cases alts exists/are available but majority is large case due to the demands (we here just see a lot small cases here because a large case simply doesn‘t fit in standard config on most engines in cruising yachts)

[CaptainRivet]

Originally Posted by s/v Jedi

Let me add to this: I see a trend developing to install a dc-dc converter between batteries and dc breaker panel regardless of voltage used. Where 24V to 12V converters were used before, I now see installations with 12V house banks and 12V breaker panels, install 12V to 12V converters, which is not commonly done on boats… yet.

The advantages are clear: you get a stable voltage at the panel, like 13.2V even when the battery is down to 12.5 or 11.9 etc. or up to 14.6V during charging.

I can’t come up with many disadvantages for this other than the need to have a unit powerful enough to provide all power required, and a backup unit or bypass switch as well.

Large loads like a windlass or engine starter are normally wired around the breaker panel anyway so the power requirement isn’t that high I think. I think this will become in use on boats as well.

Exactly, it’s also a low budget way if your yacht is older and cabling is a bit corroded and a cause a higher voltage drop that you bump up the voltage with a converter. You don‘t need to rip out cables (sure if the corrosion exceeds where cables get hot or isolation bridly you need to exchange).
Also all 12V equipment can withstand 15,0V and especially all driven by motors (like pumps) or compressor profit highly and live longer when they get higher voltage means you measure at the water pump and your compressor till you get 14V there and bump voltage up till 15V. If higher needed you go to 15V and see what you get…also converters like Victron dumb Orion’s stabilize so you always get the voltage. Fridges and fresh waterpumps are located close on my cat, so I ran an extra cable with an Dumb 30A 12 12 Orion installed and have a sub panel with fuses there so they all get stable 14V with max 40cm cable. the switches on the nav station on the old cable switch a SSR that switches on/off pumps and fridge. Cable length is 10m one way…made A huge difference in performance and in the end less power draw overall as less heat.
Freezer runs on 230V with an extra small Victron Phönix inverter.

[wholybee]

Originally Posted by CaptainRivet

Not all alternators are the same that have an equal rating. It depends what they are designed for.
Most alternators below 90A on marine engines are car alternators, made to top up a starter Batterie with high rpm (up to 8000rpm engine, alternator turn 16000) but no deep cycling batteries. They can typically do 50% of their rating max and 99% small case. Marine engine run low rpms, most till 3000 range. The next typical is alts for commercial high power drain purposes like cooling trucks which are reinforced with deep cycle charging capabilities but still run high rpm (eg the widespreaded 12V 115A Mitsubishi alternator) which can do 70 till 90% of their rating depending on rpms run.available in mostly small case but some also in large case available.
Then you have low rpm alternator for low rpm engines for high power and/or deep cycling, they can do 100% of their rating continuously. Small cases alts exists/are available but majority is large case due to the demands (we here just see a lot small cases here because a large case simply doesn‘t fit in standard config on most engines in cruising yachts)

That all makes sense. I think the point should be made about the type/intended application of the alternator. I have a small case 70A balmar alternator. Selected because I have a single V-belt and can't really go larger without and expensive belt upgrade. Point taken, it is NOT an automotive alternator. But, it is a 70A small case alternator, and I can run it 60A+ for extended periods. I would not expect a 120A balmar in the same small case to run 120A for extended periods.
So, I think the rule that a 70-80 amp alternator not being able to run over 30A for extended periods is not really true. It may be true of a 70-80A automotive alternator. But I expect that any externally regulated alternator is not an automotive alternator. And, in the context of an LFP conversion, all of this should be taken into account in the selection of what alternator to install. I do understand a lot of people will buy a 120A alternator on price, or an internally regulated, or whatever. I think a better understanding should be applied.

[fxykty]

Originally Posted by SOLAR SUPPORT

When the Bms triggers the HvCutoff action, the system is of course not de-energized. …

Huh?

That must be a very dumb BMS that can only handle a charge source by disconnecting the battery. WTF? And even if that is so, have separate charge bus and load bus so that the load bus can stay connected.

A BMS should have programmable ways of controlling your charge sources so that a high voltage cutoff event will NEVER take place. The charge source(s) should be turned off or disconnected well before the battery gets anywhere near the high voltage cutoff voltage.

If you insist on using a drip in battery with a dumb BMS, then fill your boots and use the various workarounds that have been suggested. But do realise that that is not the best nor most efficient use of LFP chemistry.

[SOLAR SUPPORT]

Originally Posted by fxykty

Huh?

That must be a very dumb BMS that can only handle a charge source by disconnecting the battery. WTF? And even if that is so, have separate charge bus and load bus so that the load bus can stay connected.

A BMS should have programmable ways of controlling your charge sources so that a high voltage cutoff event will NEVER take place. The charge source(s) should be turned off or disconnected well before the battery gets anywhere near the high voltage cutoff voltage.

If you insist on using a drip in battery with a dumb BMS, then fill your boots and use the various workarounds that have been suggested. But do realise that that is not the best nor most efficient use of LFP chemistry.

I guess you paid a lot of electrical work to find the best or most efficient way to use LFP chemistry. If your insurance company has approved your electrical infrastructure, there is no happier sailor than you.

[CaptainRivet]

Originally Posted by wholybee

That all makes sense. I think the point should be made about the type/intended application of the alternator. I have a small case 70A balmar alternator. Selected because I have a single V-belt and can't really go larger without and expensive belt upgrade. Point taken, it is NOT an automotive alternator. But, it is a 70A small case alternator, and I can run it 60A+ for extended periods. I would not expect a 120A balmar in the same small case to run 120A for extended periods.
So, I think the rule that a 70-80 amp alternator not being able to run over 30A for extended periods is not really true. It may be true of a 70-80A automotive alternator. But I expect that any externally regulated alternator is not an automotive alternator. And, in the context of an LFP conversion, all of this should be taken into account in the selection of what alternator to install. I do understand a lot of people will buy a 120A alternator on price, or an internally regulated, or whatever. I think a better understanding should be applied.

What I wrote is regarding stock alternators on marine engines.
Yes the 120A balmar in the small case will deliver 120A, they even have a 180A one in the small case that is tested. They all deliver their rating. These are the exception I mentioned, small case heavy duty low rpm alternators. And that these are exceptions you already see on the price, 200Euro for a 100A car alternator that delivers 50A— 1300Euro for a 90A mastervolt heavy Duty without the regulator.