Myth of alternator damage cause by BMS disconnect?

[RaymondR]

Originally Posted by LeighC

Thanks Raymond, I have bought a 10 amp motor speed controller (as you suggest) that I wanted to put in series with my negative field coil brush before the reg but it has a common + (pos), (eg controls the - neg) I cant see how it will let the original reg. work as a back up. My alternator is 12 volt 80 amp driving from one 10mm gates V belt so I want to back it off a bit.
Cheers - Leigh

I appear to have created confusion here, sorry.

The narrative about the motor speed controller being wired in parallel to boost alternator output was to demonstrate that you can access the internal regulator wiring of an alternator to modify the performance of the excitation circuit. The motor speed controller was wired in parallel to the regulator to allow the excitation current, and consequent alternator current and voltage output to be increased. However this cancels the automatic control of these to the battery and constant monitoring of battery voltage is required to avoid damaging the battery.

I used the above narrative to suggest that the internal regulators wiring can be modified and that doing so by putting a relay controlled by the lithium battery's BMS in series with the alternator's regulator to interrupt the excitation current and thereby stop the alternator from outputting any voltage or current might be the best and simplest way to do this without creating voltage spikes in the charging circuit.

[PaulCrawhorn]

Only if that alternator is dedicated to charging House.

Taking House offline from the engine circuit is simply not a problem so long as the Starter batt remains.

Or any old cheap lead batt, high tech solutions are simply not needed.

[SOLAR SUPPORT]

Originally Posted by RaymondR

Nah,

I have a 5 hp Honda belt driving two alternators as a battery charger.

Both alternators have internal regulators which are mounted with two screws and which connect to the alternator through a couple of spring devices when contact when you insert the regulator into the alternator body.

I have previously soldered wires to these terminals on other alternators to allow boosting the alternator current and voltage output (Generally by using the wiring to connect to a DC motor speed controller in parallel with the regulator)

There is absolutely nothing to stop me modifying the regulator wiring so that the BMS relay disconnects the alternator's excitation current with a few dollars worth of wire and a half hour with a soldering iron.

Yes, I followed the path you described before and I shared under this discussion topic.

First of all, you need to separate the alternator, which works with the regulator connected from the inside, from the engine and disassemble the alternator. Get help from someone who can do this.

Focus on one of the brush wires used for the alternator excitation and disconnect it from the regulator. Solder two opposite wires to the cut and apply insulation to avoid contact with the cut. It is sufficient to use two 2.5 mm2 cables for this job. Because the current passing through this circuit for rotor warning does not exceed 7-8 Amperes in a 115A alternator.

I made this circuit on my own boat and had very good results. This is the electrical infrastructure required to turn the alternator on and off when necessary without damaging itself and other electronic devices. To deactivate the alternator, which is operating under load, it is sufficient to separate these two wires from each other.

Connect these terminals to a simple 10A, 70°C, normally closed thermostat and prevent the alternator from burning while operating under overload.

If the lithium battery is capable of giving a warning before bms HVCutoff, connect it to a simple relay and place this relay between the alternator thermal control circuit described above.

If there is no Lithium battery HVCutoff warning, you can cut the alternator charge with a voltage sensitive relay in the same way when the target voltage is reached.

You can find the application photo showing the cut point of regulator connection to the brush below. Also a link about the application and discussion.

https://www.cruisersforum.com/forums...es-259773.html

[goboatingnow]

Originally Posted by Stu Jackson

Thanks so much for a dose of reality. It bears repeating: no one can build something that doesn't exist, so you use what is available that supports the mission. That and KISS without breaking anything, knowing well ahead of time what the pratfalls are. Thx again.

External lithium suitable alternator regulators ( with temp sensing ) are widely available , you install that, adjust the profile suitable for charging lithium’s ( just like all your other charge sources are adjusted to have a lithium charge profile ) you connect the alternator to your lithium bank and use a small 10A dc dc to charge the starter from the lithium. This also gives you a secondary recharge ability of your starter battery if your alternator fails

All this stuff is commercially available and any alternator rewind shop will make the field available externally if required , ( many alternators have the wire readily available also )

High powered dc dc converters are both expensive and another point of failure.

In the scenario, I’ve outlined you get proper alternator charging of your lithium domestic , you have the full efficiency of a direct connection and you can leave the internal regulator in place to allow you to rewire , in an emergency and directly recharge the starter , if the dc dc converter fails

I say it again there is no evidence Ive seen that a full loaded up alternator which is connected to a fully charged small starter battery will actually protect against a load dump completely ,It will certainly attenuate the spike. Remember HVC disconnects tend to happen when the alternator is not putting out much current into the lithium , but that is not the worst case scenario and the system must be designed for the worst case.

Note that it’s entirely possible to side step the issue and deploy TVS diode quenching solutions , however these will typically limit the spike to about 28V in 12v systems. I have these devices fitted on my own electronics. Automotive qualified electronics and most marine electronics should handle that type of spike but these days all sorts of cheap electronics are often connected to the 12v feed and many of these will be damaged at 28v. Cheap invertors are a classic example.

There’s nothing “ high tech “ about TVS diodes , widely available and cheap , used in car electronics every day of the year

Don’t use workarounds. You are spending several boat bucks to do a good lithium solution. Do it right

[RaymondR]

Originally Posted by goboatingnow

External lithium suitable alternator regulators ( with temp sensing ) are widely available , you install that, adjust the profile suitable for charging lithium’s ( just like all your other charge sources are adjusted to have a lithium charge profile ) you connect the alternator to your lithium bank and use a small 10A dc dc to charge the starter from the lithium. This also gives you a secondary recharge ability of your starter battery if your alternator fails

All this stuff is commercially available and any alternator rewind shop will make the field available externally if required , ( many alternators have the wire readily available also )

High powered dc dc converters are both expensive and another point of failure.

In the scenario, I’ve outlined you get proper alternator charging of your lithium domestic , you have the full efficiency of a direct connection and you can leave the internal regulator in place to allow you to rewire , in an emergency and directly recharge the starter , if the dc dc converter fails

I say it again there is no evidence Ive seen that a full loaded up alternator which is connected to a fully charged small starter battery will actually protect against a load dump completely ,It will certainly attenuate the spike. Remember HVC disconnects tend to happen when the alternator is not putting out much current into the lithium , but that is not the worst case scenario and the system must be designed for the worst case.

Note that it’s entirely possible to side step the issue and deploy TVS diode quenching solutions , however these will typically limit the spike to about 28V in 12v systems. I have these devices fitted on my own electronics. Automotive qualified electronics and most marine electronics should handle that type of spike but these days all sorts of cheap electronics are often connected to the 12v feed and many of these will be damaged at 28v. Cheap invertors are a classic example.

There’s nothing “ high tech “ about TVS diodes , widely available and cheap , used in car electronics every day of the year

Don’t use workarounds. You are spending several boat bucks to do a good lithium solution. Do it right

We are doing things with alternators, such as connecting them to large amp hour house banks and now large acceptance lithium batteries, which they were never designed for anyway so why not innovate to solve the problems in the best and simplest way.

If removing the excitation provides the simplest and most effective way of implementing a system of charging circuit interruption which will not cause equipment damaging voltage excursions in attached devices then this is the logical way to go.

This discussion has been helpful to me in another way in that it suggested a solution to another problem I have.

One of the alternators on my gas engine battery charger does not have a battery sensing terminal on it's regulator and consequently does not accept it's full share of the charging load.

So, I am going to remove it's regulator from the alternator and relocate it to the battery and run a wire from it's excitation output back to the alternator. It's my alternator and I wont be bound by where the manufacturer though it best to locate the regulator and will relocate the damned thing to wherever I want it.

[SOLAR SUPPORT]

Hello to everyone,
I replaced my 380 Ah AGM batteries with 2 Lifepo4 200 Ah batteries. While making this transition, I aimed to use new Lifepo4 batteries without changing the existing solar, Shore and engine charging equipment. I did not use a dc-dc charging unit. The alternator was displaced and disassembled at the electrical repair shop. One of the rotor warning brush connections was cut and the two ends were isolated. Two heat-resistant cables were soldered to the cut points and extended out of the alternator.
One end of these two cables is first connected to the thermostat mounted on the alternator. A voltage sensitive relay operating in the range of 12.0-14.0 volts triggers the timer with a delay of 5 minutes. At the end of the period, if the system voltage is within the specified range, the rotor's excitation current is allowed. There is also a manual on-off switch among them. The system works as I want.

The electric plan of relays: Time relay is on the left of Voltage sensitive relay in the photograph.

[sleepy]

does the balmer alternator protection module handle this ??

[rgleason]

It will improve the situation, but should just be used as a backup, to a primary protective system which protects the alt and lfp. (In my opinion)

[sleepy]

rgleason, i spoke to balmar they did not give me the warm fuzzy answer. they said the same thing! they suggested carrying 2 in case of failure that didnt make much sense to me.

[s/v Jedi]

Originally Posted by sleepy

rgleason, i spoke to balmar they did not give me the warm fuzzy answer. they said the same thing! they suggested carrying 2 in case of failure that didnt make much sense to me.

Imagine a job in a foundry where you need to use 6’ long tongs to put pieces of steel under a steam hammer. If you bring a tourniquet in your back pocket, would you do it without the tongs? Maybe you time it right 100%, yes?

[SOLAR SUPPORT]

Originally Posted by sleepy

rgleason, i spoke to balmar they did not give me the warm fuzzy answer. they said the same thing! they suggested carrying 2 in case of failure that didnt make much sense to me.

I think the APD device is not a different concept than disposable items. If the safe charge cut-off voltage setting is above the BMS Hvcutoff voltage, the LFP battery will isolate itself before the external regulator cuts off the alternator charge. This possibility always exists.

During such an accident, APD protects the alternator for once. You cannot just replace the APD and continue on your way. If you do not check the alternator charging cut-off voltage, you will throw away the second APD.

Why don't you choose solutions that do not require APD? Battery Isolator, which keeps the LA engine battery constantly connected to the alternator, protects the alternator against HV-LT Cutoff accidents caused by the LFP battery BMS.

[sleepy]

i just spoke to dale @ charging pros he was very helpful and suggested the same, and or charge la with alt, use dc to dc for lfp

[hjohnson]

Originally Posted by SOLAR SUPPORT

Why don't you choose solutions that do not require APD? Battery Isolator, which keeps the LA engine battery constantly connected to the alternator, protects the alternator against HV-LT Cutoff accidents caused by the LFP battery BMS.

Or just build your system so that a BMS disconnect will never happen. If my BMS throws an alarm due to cell overvolt, or pack overvolt, or under temp, or immenent shutdown, my alternator regulator kills the field, protecting the alternator and diode pack from a spike. This happens long before the contactor gets thrown disconnecting the battery.

[SOLAR SUPPORT]

Epoch's Victron compatible connection and Sunfunkits' Rs485 data communication are available. This communication line can be used to turn off the alternator rotor warning before the BMS isolates the Lithium battery. The necessary warning must be sent to the external environment by BMS before the isolation action is carried out. Can the Victron control system process the information coming from this battery and stop the alternator charging in a timely and safe manner? Maybe it can send a command to the alternator's external regulator to cut off charging. I am sure that if the battery BMS could send a direct electrical signal to the external environment for this purpose, it would be very useful in terms of safely cutting off the alternator charge at the right point and maintaining the continuity of energy.

[hjohnson]

Originally Posted by SOLAR SUPPORT

I am sure that if the battery BMS could send a direct electrical signal to the external environment for this purpose, it would be very useful in terms of safely cutting off the alternator charge at the right point and maintaining the continuity of energy.

That's precisely what an integrated system does. The regualtor is getting a constant flow of data from the BMS via CANbus including the target voltage/current, the actual voltage/current, and status multiple times per second.

if there's an alarm, it kills the field. If the BMS directs 0A into the battery, it kills the field.

As the battery approaches 100% SoC, it fades out the current and voltage so that it doesn't overshoot and overcharge a cell or battery.