LFP alternator charge, LA-dc2dc in which order

[SOLAR SUPPORT]

There are two problems with charging LFP batteries with a standard alternator. We solve the overheating problem of the alternator with the dc2dc device. The second problem arises when the Bms in the LFP battery is suddenly isolating the charged battery from the system while the charging continues with high current during charging.

Meanwhile, alternator rectifier diodes, internal regulator and most importantly many electronic devices are tried to be protected from this high energy by discharging the energy trapped in the alternator to the LA battery. I was wondering if the battery isolator in the [A] or [B] string might be interfering with the lead acid battery's protective function during the LFP HvCutoff event.

When the Battery Isolator is not used, I think [C] shows the correct connection order.

[goboatingnow]

Originally Posted by SOLAR SUPPORT

There are two problems with charging LFP batteries with a standard alternator. We solve the overheating problem of the alternator with the dc2dc device. The second problem arises when the Bms in the LFP battery is suddenly isolating the charged battery from the system while the charging continues with high current during charging.



Meanwhile, alternator rectifier diodes, internal regulator and most importantly many electronic devices are tried to be protected from this high energy by discharging the energy trapped in the alternator to the LA battery. I was wondering if the battery isolator in the [A] or [B] string might be interfering with the lead acid battery's protective function during the LFP HvCutoff event.



When the Battery Isolator is not used, I think [C] shows the correct connection order.

The sudden loss dump is not the insurmountable problem it’s presented here. There are several well established means

The first and most successful is a regulated based fiend current switch off this removes almost any spike this modification can easily be done by most alternator shops

Secondly retaining load presence during such energy’s can also work thdgbload can be a battery a diversion load or a d dc losc

Thirdly it’s entirely practical to build protection circuits that will clamp the spike to safe levels. There are plenty of solutions in this area largely derived from car solutions .

I think this concern is over focused on alternator protection and is driving bad system architecture design decisions such as dc dc to starter decisions etc.

[smac999]

C is the only correct awswer. The otheres are wrong to do.

In a and b the isolator gets removed and you end up with c.

D is plain wrong feeding an alt into the dc to dc.

[CaptainRivet]

Originally Posted by goboatingnow

The sudden loss dump is not the insurmountable problem it’s presented here. There are several well established means

The first and most successful is a regulated based fiend current switch off this removes almost any spike this modification can easily be done by most alternator shops

Secondly retaining load presence during such energy’s can also work thdgbload can be a battery a diversion load or a d dc losc

Thirdly it’s entirely practical to build protection circuits that will clamp the spike to safe levels. There are plenty of solutions in this area largely derived from car solutions .

I think this concern is over focused on alternator protection and is driving bad system architecture design decisions such as dc dc to starter decisions etc.

The problem with solution 1 with the widespreaded mitsubishi 115A alternator (that solar arch has too) is if you modify it to external field cut you loose its internal temp regulation.
so you either go all in and modify it with an external regulator like Balmar with temp regulation or you use the Nordkyn VRC200 that does that unmodified via the sense wire, both cost you 300Euro (Nordkyn, what i will do now) or 500Euro (Balmar without alt modification).


THe DC2DC itslef don't give the alternator a load, its the lead starter battery that does and limit the current so alternator is not overloaded. Putting the DC2DC directly on the alternator would need an protection curcuit.
Well 300Euro for a 30A DC2DC heater or 300Euro for a Nordkyn VRC200 that gives you 80A is a nobrainer to go with the Nordkyn...well I had 2 DC2DC ORions before I got aware of the Nordkyn modul, just ordered 2 Norkyns and the DC2DC will then charge the LTO bank that will replace the lead starter in the bb hull. STB is started directly from the 840 LFP house.



Could you please lead me to those different solutions, links thats derived from cars.

[slacker]

Version A makes sense to me if you have an externally regulated alternator and something like a Balmar MC-614.

Alternator output (controlled by MC-614) is connected to theArgoFet which is connected to the FLA starter battery and the LFP.

All with proper fuses and cable sizing of course.


Would this not be the simple solution?

[SOLAR SUPPORT]

Originally Posted by slacker

Version A makes sense to me if you have an externally regulated alternator and something like a Balmar MC-614.

Alternator output (controlled by MC-614) is connected to theArgoFet which is connected to the FLA starter battery and the LFP.

All with proper fuses and cable sizing of course.


Would this not be the simple solution?

I think you have an externally regulated alternator. I think [A] is the option that suits you. In the diagrams, an externally regulated alternator is not used. With such an alternator, a dc2dc charger will not be necessary anyway. Standard alternator.

One reason I opened the topic was to reveal the simplest and safest alternator drop-in LFP charging scheme. [A] is available on many fabricated boats. This is how my setup is. The only difference is that I am not currently using a dc2dc charger.

The [C] option solves both problems when charging a drop-in LFP with a standard factory alternator. The only disadvantage of this option is that the LA battery is used without isolation. An automatic relay switch can be used to disconnect the engine battery from the LFP battery pack when the engine is stopped.

The simplest and safest is [C] I guess.

[goboatingnow]

My own view now firmly swings to ether modifying the alt or using a dedicated dc Dc from the alt directly to the lfp bank. I’ve tested two Chinese dc dc 80A units and additional fans are needed in extremis the solution is reasonably priced and works.

I still think a proper externally regulated alternator controller is the best long term option

[SOLAR SUPPORT]

Originally Posted by goboatingnow

My own view now firmly swings to ether modifying the alt or using a dedicated dc Dc from the alt directly to the lfp bank. I’ve tested two Chinese dc dc 80A units and additional fans are needed in extremis the solution is reasonably priced and works.

I still think a proper externally regulated alternator controller is the best long term option

The task of an external regulator, which monitors the load status and temperature of the alternator, is to safely disconnect the alternator charge before the bms of the drop-in LFP battery triggers the HvCutoff action.

As the voltage balance of the cells in LFP drop-in batteries deteriorates over time, the HvCutoff voltage decreases accordingly. So this is not a fixed value, it is variable. It is not possible for the regulator to know the drop-in LFP HvCutoff voltage that changes over time.

Therefore, the charging cut-off voltage of the alternator can be adjusted 0.5-0.7 volts below the estimated HvCutoff to avoid an accident.

The [C] option may allow the alternator to be subjected to Hvcutoff action under the protection of the LA battery. But, uncontrolled repetition of this undesirable event may damage the hardware and LFP batteries.

In the [C] option, it is necessary to use an advanced dc2dc charger that can gradually reduce the dc2dc charge current just before the target charge voltage is reached and then safely cut off the alternator charge when the target charge voltage is reached. Is it possible to get a secure solution with a simple dc2dc device?

[goboatingnow]

Originally Posted by SOLAR SUPPORT

The task of an external regulator, which monitors the load status and temperature of the alternator, is to safely disconnect the alternator charge before the bms of the drop-in LFP battery triggers the HvCutoff action.



As the voltage balance of the cells in LFP drop-in batteries deteriorates over time, the HvCutoff voltage decreases accordingly. So this is not a fixed value, it is variable. It is not possible for the regulator to know the drop-in LFP HvCutoff voltage that changes over time.



Therefore, the charging cut-off voltage of the alternator can be adjusted 0.5-0.7 volts below the estimated HvCutoff to avoid an accident.



The [C] option may allow the alternator to be subjected to Hvcutoff action under the protection of the LA battery. But, uncontrolled repetition of this undesirable event may damage the hardware and LFP batteries.



In the [C] option, it is necessary to use an advanced dc2dc charger that can gradually reduce the dc2dc charge current just before the target charge voltage is reached and then safely cut off the alternator charge when the target charge voltage is reached. Is it possible to get a secure solution with a simple dc2dc device?

The point is once you are under the control of a dc dc convert or you can use its output to structure alternator protection or battery charging strategy.

[s/v Jedi]

Here is the diagram I recommend for this setup. It uses the engine with start motor and alternator as it comes from the factory.

This diagram shows how to use multiple batteries; if you only have one start battery then simply delete the second, as well as the isolation switch.

For the house bank, simply delete the second battery and also the smart shunt. If you use a drop-in LFP battery instead of individual cells, then you don’t have the wire from cell 2 to the battery monitor for cell balance monitoring; connect it to the start bank instead to take over that task from the smart shunt, or just leave disconnected if you keep the smart shunt.

This diagram has separate fuse boxes for each battery bank; in this diagram mostly used for connecting Orion dc-dc chargers with one going each way and feeds to a breaker panel where you may have an OFF, A, B, A+B switch to select the source.

The bilge pump shows directly connected to a busbar instead of the fusebox. This is to allow for a push-to-reset breaker instead of replaceable fuse.

I recommend the diagram with the two start batteries and two house batteries for redundancy reasons at the cost of extra switches and monitors. I am of the opinion that the redundancy is well worth that extra cost for an offshore cruiser, but if one sails inland or coastal only, priorities may shift.

[SOLAR SUPPORT]

Originally Posted by goboatingnow

The point is once you are under the control of a dc dc convert or you can use its output to structure alternator protection or battery charging strategy.

I just reviewed smart dc2dc chargers. These "smart" devices have stipulated to be used with smart alternator. In other words, they do not have the feature of cutting the standard alternator charge. The smart alternator must be an externally regulated alternator. Why would you need a dc2dc charger if you have such a smart alternator?

[goboatingnow]

Originally Posted by SOLAR SUPPORT

I just reviewed smart dc2dc chargers. These "smart" devices have stipulated to be used with smart alternator. In other words, they do not have the feature of cutting the standard alternator charge. The smart alternator must be an externally regulated alternator. Why would you need a dc2dc charger if you have such a smart alternator?

If you use a dc dc converter mine has controlled voltage out and constant current control

Using both of these especially constant current restricts alternator overproduction you can then decide to charge the battery directly of feed the controlled dc into a more sophisticated battery charger I have both options but I think the dc dc would be sufficient directly.

As of yet the input has survived tests I now have my 500w electronic programmable load with me on the boat to setup more disruptive strategies

[Pete7]

Originally Posted by s/v Jedi

This diagram shows how to use multiple batteries; if you only have one start battery then simply delete the second, as well as the isolation switch.

Nick, struggling to see why you have Orion 24:12 converters? If the engine is 12v then fine, if its 24v well the diagram has it connected to the 12v pos buss bar via the smart shunt.

If the output of the solar MPPT is 24 volt, then its also connected to the 12v pos buss bar.

If the wire from the fuse box nearest the solar panels has the poss wire going up to the 12v pos buss bar is removed then that makes more sense, I think.

Pete

[CaptainRivet]

Originally Posted by Pete7

Nick, struggling to see why you have Orion 24:12 converters? If the engine is 12v then fine, if its 24v well the diagram has it connected to the 12v pos buss bar via the smart shunt.

If the output of the solar MPPT is 24 volt, then its also connected to the 12v pos buss bar.

If the wire from the fuse box nearest the solar panels has the poss wire going up to the 12v pos buss bar is removed then that makes more sense, I think.

Pete

It’s both, one 12:24 and one 24:12…they are just place holders. Had the same issue with the diagram. So you can charge both ways and 12V starter is always full.

[CaptainRivet]

Originally Posted by goboatingnow

The point is once you are under the control of a dc dc convert or you can use its output to structure alternator protection or battery charging strategy.

Can you please explain if you connect the DC2DC converter directly to the dumb alternator without external control how do you a)protect the alternator from a sudden disconnect and b)from getting overheated.
That a stock alternator like Mitzi 115A has a working internal temp control is not common, it’s the exception.