Myth of alternator damage cause by BMS disconnect?

[Dieseldude]

Thanks goboating now! one Farad is a huge capacitance, should be able to suck up some serious transients. I have in the past run vehicles without a battery after starting on a boost, but that was risky considering no battery capacitance. Not to doubt your contribution, but is there any official source for that rule of thumb if needed for future? It could be quite obscure to find from battery manufactures, since it is seldom, if ever, thought of by most battery users.


Again, thanks for your insight.

[goboatingnow]

Sorry I just realised my typo it’s 1000F per 150aH

This is the “ typical “ value that was bandied about when I was in the research area around high speed charging

Search for some papers here’s one

https://digitalscholarship.unlv.edu/...sdissertations

This is the simplified model of a battery consisting of a internal resistance representing

[Wotname]

Originally Posted by goboatingnow

Sorry I just realised my typo it’s 1000F per 150aH

This is the “ typical “ value that was bandied about when I was in the research area around high speed charging

...........

Are you sure it is 1000F per 150ah; that seems awfully high!

I would have thought maybe 1000uF.

[goboatingnow]

1000uf is a very small capacitance

Here’s a summary from the two time constant model used in the EPA model

This model is a more precise model. Separates the discharge and charge capitances etc.

https://www.epa.gov/sites/default/fi...technology.pdf



Note the capacitances are essentially in series and in Farads. This is for a 68Ah battery

This averages around 600F if both are computed together which agrees with my rough rule of thumb.

These capacitances are highly variable
As can be seen




For reference the EPA battery model is



Representing short term electro magnetic double layer effects and long time electro chemical transport effects.

As you can see the short term capacitance dominates in general ( remember capacitors in series are lower )


In the previous reference a more simplified model was used



Again Rt and Ct were determined experimentally



Simple maths on the RC time constant for a Rt of 0.02 will show equivalent capitances in the order of 500-600F for 80 Ah

[goboatingnow]

Remember this is a battery model. A battery isn’t a capacitor per se

But ask yourself this if you charged up a 1000uF cap to 12v and connected it to your boats system , how long would you think it’s would keep the lights on Then scale up the equivalent capacitance needed to equate to 100Ah ( hint lots and lots of farads )

This is why replacing a battery with a capacitor isn’t going to work for load dumping , the cap would be 10s of farads

[witzgall]

Hi Chris from Balmar here.

As you may know, we are introducing protection modules (APM-12 and APM-24) that meet ISO16750-2 for load dump & surge protection; ISO 7637-2 for surge capability, and SAE-j1171 for ignition protection. We also had them salt tested too (ASTM B117). We designed them to be easy to install, and have both a visual and audio feedback of their protection state.

They should be available sometime in January.

When testing in the lab, it is quite hard to damage the diodes in one of our alternators due to disconnects. We use either high quality avalanche or 400v diodes.
However, damage does happen in the field. Loose connections (repeated disconnects, perhaps with arching) is a possibility for how this happens.

https://balmar.net/wp-content/upload...PDS-APM-12.pdf

The APM could be used to protect electronics installed at the breaker panel, but we are not making this claim as we have done no testing for this, and do not plan to do this testing at this time.

Some additional comments on this thread thusfar:

TVS or Zenier diodes alone have typically little impact on the survivability of alternators (due to load dump) on their own. Some have used a zenier with a large capacitor. This can work, but if the capacitor is "Filled up" then the spike gets through. This means that it could work for short duration spikes, but not longer ones.
Varistors can catch on fire, so we do not recommend their use for transient protection.

Chris

[Wotname]

Originally Posted by goboatingnow

1000uf is a very small capacitance

Here’s a summary from the two time constant model used in the EPA model

This model is a more precise model. Separates the discharge and charge capitances etc.

https://www.epa.gov/sites/default/fi...technology.pdf

Attachment 249430

Note the capacitances are essentially in series and in Farads. This is for a 68Ah battery

This averages around 600F if both are computed together which agrees with my rough rule of thumb.

These capacitances are highly variable
As can be seen

Attachment 249431


For reference the EPA battery model is

Attachment 249432

Representing short term electro magnetic double layer effects and long time electro chemical transport effects.

As you can see the short term capacitance dominates in general ( remember capacitors in series are lower )


In the previous reference a more simplified model was used

Attachment 249433

Again Rt and Ct were determined experimentally

Attachment 249434

Simple maths on the RC time constant for a Rt of 0.02 will show equivalent capitances in the order of 500-600F for 80 Ah

OK thanks for the detail, it all makes sense now. Nevertheless, 10000F is a sizeable capacitor <insert 'understatement' icon>

[team karst]

Originally Posted by witzgall

.,,.

Varistors can catch on fire, so we do not recommend their use for transient protection.



Chris

There is a line of MOVs now with built in thermal fusing. I’ve been designing those into products lately.

[Dieseldude]

Originally Posted by witzgall

Hi Chris from Balmar here.

As you may know, we are introducing protection modules (APM-12 and APM-24) that meet ISO16750-2 for load dump & surge protection; ISO 7637-2 for surge capability, and SAE-j1171 for ignition protection. We also had them salt tested too (ASTM B117). We designed them to be easy to install, and have both a visual and audio feedback of their protection state.

They should be available sometime in January.

When testing in the lab, it is quite hard to damage the diodes in one of our alternators due to disconnects. We use either high quality avalanche or 400v diodes.
However, damage does happen in the field. Loose connections (repeated disconnects, perhaps with arching) is a possibility for how this happens.

https://balmar.net/wp-content/upload...PDS-APM-12.pdf

The APM could be used to protect electronics installed at the breaker panel, but we are not making this claim as we have done no testing for this, and do not plan to do this testing at this time.

Some additional comments on this thread thusfar:

TVS or Zenier diodes alone have typically little impact on the survivability of alternators (due to load dump) on their own. Some have used a zenier with a large capacitor. This can work, but if the capacitor is "Filled up" then the spike gets through. This means that it could work for short duration spikes, but not longer ones.
Varistors can catch on fire, so we do not recommend their use for transient protection.

Chris

Thanks for the info. Good to see a convenient product that can be connected right to an alternator without having to order individual parts and fabricate a circuit.

[SOLAR SUPPORT]

It finally happened, it took some effort but it's totally worth it. After disassembling my alternator I took it to a good repair center. They made a bridge circuit to stop the alternator charging by cutting off rotor exciting brush lead to the regulator. I put my alternator on the engine and made the electrical connections. Trials are positive. While the engine is running: When the ends of the cables extended out of the bridge circuit soldered in the alternator come together, the battery is charged. Charging stops when the ends of the cables are disconnected. In the meantime, the engine rev counter on the control panel continues to operate, the ignition light does not turn on. I mounted the thermostat which is normally closed type on to the alternator. Thermostat opens at 70 degrees Celsius and charging stoped by the thermostat control. For now, the ends of these wires are connected to the thermostat. With the AGM batteries at 50% SOC, my alternator was overheating more than 130 C° under a 75 Amp charge load. This issue has been resolved by turning on and off the charge load. Alternator is being cooled by its internal fan when not charging the batteries.

When I upgrade to Lithium battery in the future, I can directly charge the lithium batteries with full alternator capacity without using a DC-DC charger. Now there is something important I need to know.. Does the HVCutoff event of a lithium battery change according to the internal temperature of the battery? The HVCutoff level is important because I want to add a second circuit breaker to stop the alternator charging when necessary, with the help of a voltage sensitive relay connected in series with the thermostat connected to the Alternator's rotor exciting terminals. How many volts do you think the trigger voltage setting should be before the voltage sensitive relay kicks in?

[Cadence]

Originally Posted by SOLAR SUPPORT

It finally happened, it took some effort but it's totally worth it. After disassembling my alternator I took it to a good repair center. They made a bridge circuit to stop the alternator charging by cutting off rotor exciting brush lead to the regulator. I put my alternator on the engine and made the electrical connections. Trials are positive. While the engine is running: When the ends of the cables extended out of the bridge circuit soldered in the alternator come together, the battery is charged. Charging stops when the ends of the cables are disconnected. In the meantime, the engine rev counter on the control panel continues to operate, the ignition light does not turn on. I mounted the thermostat which is normally closed type on to the alternator. Thermostat opens at 70 degrees Celsius and charging stoped by the thermostat control. For now, the ends of these wires are connected to the thermostat. With the AGM batteries at 50% SOC, my alternator was overheating more than 130 C° under a 75 Amp charge load. This issue has been resolved by turning on and off the charge load. Alternator is being cooled by its internal fan when not charging the batteries.

When I upgrade to Lithium battery in the future, I can directly charge the lithium batteries with full alternator capacity without using a DC-DC charger. Now there is something important I need to know.. Does the HVCutoff event of a lithium battery change according to the internal temperature of the battery? The HVCutoff level is important because I want to add a second circuit breaker to stop the alternator charging when necessary, with the help of a voltage sensitive relay connected in series with the thermostat connected to the Alternator's rotor exciting terminals. How many volts do you think the trigger voltage setting should be before the voltage sensitive relay kicks in?

?????

[PaulCrawhorn]

Originally Posted by SOLAR SUPPORT

With the AGM batteries at 50% SOC, my alternator was overheating more than 130 C° under a 75 Amp charge load. This issue has been resolved by turning on and off the charge load.

Confused, it seems to me your overtemp cutoff is stopping the output at source right? That is very different from this thread topic, isolating the load (battery) from the alt.

Are any other loads fed by the alternator are now running off bank storage? Or is that alt dedicated to charging only?

Personally I prefer current limiting solutions that keep output going, while also preventing the alternator from going overtemp in the first place.

...

No, HVC does not need to change with temperature.

Yes, if you are regulating current, going over say 0.4C, but in that case protecting against too-cold temps, going WOT when the LFP is hot is fine.

Your charge termination HVC should ideally be adjustable, between say 3.3V and 3.6V

And your BMS acts as failsafe redundant backup for when that primary HVC fails.

[SOLAR SUPPORT]

Bavaria standard electrical installation on my boat is available in its original form. In addition to this system, solar charging support works directly connected to the battery terminals. The engine and service battery group are connected to the system with a diode type isolator. Engine and service batteries have two separate on-off switches, both of which are on when the engine is running. After the alternator adaptation was completed, I observed that the current was reset from the battery monitoring panel during the on and off attempts and returned immediately when the circuit was closed, and I tried this many times. Since the entire system was connected to the batteries, all electrical devices remained operational during this event and no problems were encountered. It makes sense to me to keep the engine operating hours required to fill your batteries with the alternator at the lowest level by preserving the alternator and thus to save fuel. Lifepo4 upgrade is already a high expense. In addition to this expenditure, I do not think it is necessary to make some additional expenditures that I do not consider necessary at this stage. Like adding DC-DC charger and/or Lead-acid battery. I bought the low cost HVCutoff circuit to add to the alternator on-off control circuit. This device offers wide and very precise voltage adjustment possibilities. This upper cutoff setting needs to be set somewhere in the 14.2~14.5 volt range. This circuit will be added to the system when Lifepo4 batteries are installed. After learning the temperature-dependent HVCutoff values ​​of the Lifepo4 battery, which has not yet been purchased, for the product, I think it would be best to adjust the voltage slightly below this. This will probably be 0.2~0.3 volts below the Lifepo4 battery HVCutoff value.

[more]

Originally Posted by SOLAR SUPPORT

I mounted the thermostat which is normally closed type on to the alternator. Thermostat opens at 70 degrees Celsius and charging stoped by the thermostat control. For now, the ends of these wires are connected to the thermostat. With the AGM batteries at 50% SOC, my alternator was overheating more than 130 C° under a 75 Amp charge load. This issue has been resolved by turning on and off the charge load. Alternator is being cooled by its internal fan when not charging the batteries.

The thermal challenges have also been compounded by the rise in underhood ambient temperatures in automotive vehicles. In the 1960’s the typical underhood inlet cooling air temperature to the alternator was 90°C. By the 1980’s this had jumped up to 110°C. Today, applications approach the 130°C range.


So, what has been done to meet this challenge? First let us look at the device itself. Early 1960’s vintage rectifiers incorporated diodes that were typically packaged in a can configuration. It had a maximum reliable operating case temperature of roughly 160°C. Later in the 1980’s, button and sandwich configured diodes became popular and with improvements in diode manufacture the temperature capability was raised to 180°C.

Today, the trend among several manufacturers has been to use press-fit diodes with a maximum operating case temperature of 200°C. These temperature improvements were driven primarily by improved package designs that reduced fatigue failures resulting from thermal expansions and contractions in the diode attachment area. Clearly, these improvements in diode temperature capability have greatly helped in meeting this thermal design challenge.
https://www.electronics-cooling.com/...r-electronics/
https://scholar.harvard.edu/files/sc...lternators.pdf

[SOLAR SUPPORT]

In addition to the high temperature resistance of the regulators and diodes in today's aternators, the temperature resistance of the insulation coatings of the stator windings is also important. My alternator has completed two years, I think, it has worked 60-70 times every year. During the disassembly of the alternator, I observed that the bright copper tone color of the stator windings turned gray on the side away from the fan. I have no doubt that the cause is definitely the alternator overheating under load. I think that the engine and alternator, which operate in a closed compartment with heat and sound insulation on the boat, operate under less demanding conditions in terms of temperature under the hood of the automobile, which can occasionally accelerate and cool itself with cold air. 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. The first step of this protection is overheating. First-stage alternator protection is sufficient for boats using lead-acid conventional batteries. However, boat owners who upgrade to Lithium battery technology say that the internal HVCutoff circuit of the batteries that come with this technology protects the battery itself, but; They should be aware of the possibility of damaging the alternator and other electronic devices while it is running. For this, it is necessary to use a low cost external HVCutoff protection circuit as the second alternator protection stage.