Myth of alternator damage cause by BMS disconnect?

[goboatingnow]

Now that you have external field current control , you could use a battery monitoring system that has many inputs , so you could monitor battery temp , alternator temp etc. The best solution is one relay or solid state device , driven by electronics that monitors the things that are important rather then a set of series disconnects.

More sophisticated external alternator regulators can also modulate the field current so that instead of complete disconnects , the output of the alternator is reduced to lower the case temperature.

[SOLAR SUPPORT]

I think it will be enough for me for now to simply cut off the alternator charge temporarily harmlessly with over-temperature and HVCutoff protection circuits when necessary, and continue charging after the alternator has cooled itself sufficiently. Maybe there are those who know: There is the ECU, the "Electronic Control Unit", which is used in new generation cars that controls the alternator from the path I follow. This device has other functions in addition to the battery charge controls you mentioned. The ECU temporarily shuts down the alternator charge until the engine load decreases, so that the climbing power does not decrease when the engine is going uphill or when the vehicle is trying to accelerate. It has another feature, when the engine first starts, it delays the charging of the alternator at full load until the engine warms up. It has many more features, no doubt about it. I think there is a need for an ECU-like unit that controls the healthier operation of the alternator, especially after the Lithium battery upgrade for boats.

[goboatingnow]

There are alternator regulators like https://www.offgridsoftwaresolutions...BoCLOUQAvD_BwE and others that will measure alternator and battery temp and control the field current. If you intend to go lithium this type of unit is very useful

[more]

Originally Posted by SOLAR SUPPORT

In addition, it is known that the alternators installed in cars are not exposed to loads such as charging batteries with a large capacity as in boats for an hour or more. Alternators installed on boats are a charging device that must be protected for the reasons I mentioned above.

you think so. modern car BMW,Mercedes and other need to 2500w power for bunch electronic installed in car. 2500W / 12v 208A

[baltic sailor]

Today the newer cars have alternators with more then 200A. The internal heaters in European cars draw 2kw. These electrical heating works until the engine has warmed up. They use a smart regulator controlled via the Linbus. You can very easy see it on the newer cars. The alternator has a heavy wire which carries The Postive voltage to charge the battery. The second wire is thin and it,s the Linbus. The Alrernator is a slave to the engine control processor (ECU) which is the Master. It's a complex system. Inside the alternator is a microprocessor which works together with the ECU. I' m sure soon someday will have a controller which simulates the ECU and we will use a modern alternator..
Till then companies like Balmar , Offgridsolution will stay in business.....

[Dieseldude]

Originally Posted by baltic sailor

Today the newer cars have alternators with more then 200A. The internal heaters in European cars draw 2kw. These electrical heating works until the engine has warmed up. They use a smart regulator controlled via the Linbus. You can very easy see it on the newer cars. The alternator has a heavy wire which carries The Postive voltage to charge the battery. The second wire is thin and it,s the Linbus. The Alrernator is a slave to the engine control processor (ECU) which is the Master. It's a complex system. Inside the alternator is a microprocessor which works together with the ECU. I' m sure soon someday will have a controller which simulates the ECU and we will use a modern alternator..
Till then companies like Balmar , Offgridsolution will stay in business.....

As if Engines and their accessories were not already complex enough. I microprocessor inside an alternator that talks to the engine computer sounds like an expensive can of warms when part of the system fails. It seems to be fantastic to monitor heat of the alternator and battery and current demand and to delay charging the battery until engine has warmed through, this adds a whole order of magnitude to complexity and certainly bumps up the cost. If the system is designed with switching to override the automation into a "get home" mode, this would help.



Turning something as basic as an alternator into a complex data controlled system is certain to create opportunity for a host of new kinds of failures. An alternator can simply be protected by fuses, breakers, and thermal overload devices. Going a step further, an independent system with current sensing with feed back to the exciter coil would be helpful to control overcharge and overload, but if not designed for ease of trouble shooting and repair, could cause as many problems as it would prevent.

[RaymondR]

Originally Posted by Dieseldude

Turning something as basic as an alternator into a complex data controlled system is certain to create opportunity for a host of new kinds of failures. An alternator can simply be protected by fuses, breakers, and thermal overload devices. Going a step further, an independent system with current sensing with feed back to the exciter coil would be helpful to control overcharge and overload, but if not designed for ease of trouble shooting and repair, could cause as many problems as it would prevent.

Hence the emphasis on managing what happens to the excitation current rather than the alternator.

The basic alternator constitutes two circuits; the power output circuit which consists of the stator windings and diode bridge, and the excitation circuit which consists of the voltage regulator and the rotor windings.

The answer to the problem of causing large voltage excursions by interrupting the alternator output circuit might be as simple as having the BMS system interrupt the power supply to the alternators excitation circuit rather than the power output circuit.

[Wotname]

Originally Posted by RaymondR

Hence the emphasis on managing what happens to the excitation current rather than the alternator.

The basic alternator constitutes two circuits; the power output circuit which consists of the stator windings and diode bridge, and the excitation circuit which consists of the voltage regulator and the rotor windings.

The answer to the problem of causing large voltage excursions by interrupting the alternator output circuit might be as simple as having the BMS system interrupt the power supply to the alternators excitation circuit rather than the power output circuit.

Hmm... don't forget to consider the third 'circuit' which is the rotor rpm. This has a large influence EMF generated in the stator winding - as much effect as the rotor current.

However I do agree that monitoring the rotor current is a step in a better direction.

[SOLAR SUPPORT]

Be sure that the control unit similar to ECU used in automobiles will be developed for marine engines in the future. When that day comes, you may need to change your alternator. I don't want to wait until that day and replace my 115A alternator, which is in good condition.

The solution I have implemented on my own boat is the installation labor cost of the bridge circuit mainly made in the Alternator, plus a $1 thermostat and a 12$ voltage sensitive adjustable 30A relay. These are not easily malfunctioning devices.

80 C° Thermostat is normally closed. When the outside temperature of the alternator rises above 80°C, it cuts off the rotor warning curent. When the alternator, which will cool itself in a short time with its internal fan, sees the outside temperature of 70 C°, the thermostat closes the warning current circuit again and the alternator continues to charge with this cycle. The thermostat will only open when the alternator is exposed to high current loads for a long time. In a boat with a lead-acid battery bank, only the thermal control circuit is sufficient to prevent the alternator from heating with excessive current load.

For a boat with a Lifepo4 battery bank, this Thermal protection circuit mentioned above is necessary but not sufficient. It is the most rational way to terminate the alternator charge in a safe way by cutting the Alternator's rotor warning current temporarily when the charge voltage is equal to 0.2-0.3 volts below of the HVCutoff trigger voltage of the Lifepo4 battery. In order to do this, it is necessary to use a voltage sensitive regulated relay. When the Lifepo4 battery voltage drops to a certain value, the alternator warning current circuit will be closed by the voltage sensitive relay and the alternator continue charging untill the alternator charge voltage reaches the safe voltage level of the Lifepo4 battery.

I don't need a Lifepo4 battery upgrade yet, as the AGM batteries on my boat have not reached the end of their service life. It's ready to hang in my hand. When I upgrade to this Lifepo4 in the future, I will definitely provide this additional protection by mounting the external control HVCutoff protection circuit next to the thermal control circuit in series.

[Cadence]

Originally Posted by CarlF

I agree that this risk is wildly exaggerated in today's typical cruising boat installation.

To have a BMS disconnect is evidence of an improper installation.

I have never had my BMS disconnect for the simple reason that all charging sources are set well below the voltage that the BMS would disconnect. In my case they are set to a 14.1v bulk and 13.4v float (from the battery manufacturer) while the BMS won't disconnect until 14.6v. And the maximum charge amps for my solar panels plus alternators running together is less than 50% of the maximum charging amps for the bank.

And since my bank consists for five drop-ins in parallel, all five would have to disconnect to bother the alternator.

Still, if the very small risk bothers you it's easy to:

a) install a Sterling Alternator Protector for less than $100

b) Parallel a lead/acid battery as suggested previously

c) do a+b

An electrolytic capacitor might be better than a lead/acid battery since it doesn't require maintenance.

[team karst]

Originally Posted by Cadence

An electrolytic capacitor might be better than a lead/acid battery since it doesn't require maintenance.

That might work. The cap smooths out the V transition from full load to zero load. It will become a race to the finish; either the VR will reduce the field current in time to save the cap from OV, or, it won't. A strict calculation on the VR time constant would be in order. Even a 10000uF 25V cap won't take 60 inbound Amps for long, depending on its V rating.

[Cadence]

Lets go back to a generator and a black box regulator with a voltage and current coil as I recall. No pun intended. Most won't have the slightest. :-)

[team karst]

Last seen by me on a ‘70 VW van

I wonder how big a 100A one would be

[goboatingnow]

Originally Posted by Dieseldude

As if Engines and their accessories were not already complex enough. I microprocessor inside an alternator that talks to the engine computer sounds like an expensive can of warms when part of the system fails. It seems to be fantastic to monitor heat of the alternator and battery and current demand and to delay charging the battery until engine has warmed through, this adds a whole order of magnitude to complexity and certainly bumps up the cost. If the system is designed with switching to override the automation into a "get home" mode, this would help.



Turning something as basic as an alternator into a complex data controlled system is certain to create opportunity for a host of new kinds of failures. An alternator can simply be protected by fuses, breakers, and thermal overload devices. Going a step further, an independent system with current sensing with feed back to the exciter coil would be helpful to control overcharge and overload, but if not designed for ease of trouble shooting and repair, could cause as many problems as it would prevent.

There’s already a “ micro processor “ inside your boats alternator.

The LinBus based regulators are a single dedicatedintegrated IC. Not any different to the current non linbus alternators.

Electronics are far more reliable then mechanical things.

Your “ external “ system of course is also a microprocessor.

Loads and loads of microprocessors on boats these days. Mine has 28. !!

You can’t protect alternators with breakers by the way or fuses.

[goboatingnow]

Originally Posted by team karst

That might work. The cap smooths out the V transition from full load to zero load. It will become a race to the finish; either the VR will reduce the field current in time to save the cap from OV, or, it won't. A strict calculation on the VR time constant would be in order. Even a 10000uF 25V cap won't take 60 inbound Amps for long, depending on its V rating.

10000uF would be far too small values in excess of 1F would be needed , batteries are equivalent to 100F

The VR can do nothing to regulate the load dump response. The output spike is not a function of the field current at that point and is not influenced by it.