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Old 15-11-2021, 08:20   #76
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Re: Alternator burn out charging lithium

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Originally Posted by goboatingnow View Post
I fail to see how raising the sense voltage will result in lower current to the battery. If the battery voltage plus the cell voltage is still below the alternator internal reference voltage , it will still pump out max field current.
I think the false hope here is that the 0.7V plus the B+ wiring drop will increase enough to partially limit alternator I.

Root cause of this madness is the long(er) wiring used in boats compared to cars, plus the very large storage capability in boats, which show the weakness of these simple designs.

You want a hard source of alternator volts, plus the obvious ability to drive that current without burning out the alternator. Those requirements make this more complicated, if not impossible.

ps: my 6 year old Chevy controls the Alt voltage set point using some algorithm. Boats, even more so, need a smart algorithm, obviously targeted by "smart regulators".
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Old 15-11-2021, 08:27   #77
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Re: Alternator burn out charging lithium

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I’m sorry there could be literally micro amps flowing in the sense circuit , and most sense lines are current sinks , A resistance in the sense line might have to be huge and would cause the sense terminal to have a lower voltage.

NOTE AGAIN I didn’t mention anything with the sense line and a diode.

The simplest way to reduce current is to place a high current diode in the CHARGING circuit and sense on the alternator side ( that’s even assuming your doing battery sensing which most people’s setup are not anyway. ) a splitter diode in effect achieves this and could be wired to provide two diode drops
Rarmond is correct.

Config 1-Putting a forward biased 0.7 V diode in series in the alternator's internal regulator sense line (that is sensing battery B+) will drop 0.7 volts, so 13v B+ at the battery looks like 12.3 volts to the alternator regulator, and the alternator charge current will increase as a result.

Config 2- Connect the normal sense line from the alternator to the battery terminal directly. Then put a forward biased 0.7v heavy duty heat sinked diode in series within the output wire between the alternator and the battery. This will result in less charge voltage reaching the battery terminal. The charge current will remain the same, and the alternator will work as hard as a diode-less configuration, but if there is for instance an internal 13.4 volt regulator, only 12.7 volts will be present at the battery at full charge, the other 0.7 volts having been dropped across the series high current diode. The power across this diode could be as high as 60*.7 or 42 watts (DC) for a 60A alternator.
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Old 15-11-2021, 08:40   #78
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Re: Alternator burn out charging lithium

Good god do people not read

A diode in the charging circuit SENSED ON THE ALTERNATOR SIDE will not change the alternator set point. The lower voltage will result in the alternator supplying less current. Most alternators on boats ARE not battery sensed anyway.

Secondly if you put a diode in the charge line and then still battery sense you will make the alternator work even harder. That’s not what you want to do.
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Old 15-11-2021, 08:53   #79
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Re: Alternator burn out charging lithium

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Originally Posted by Ericson38 View Post
Rarmond is correct.



Config 1-Putting a forward biased 0.7 V diode in series in the alternator's internal regulator sense line (that is sensing battery B+) will drop 0.7 volts, so 13v B+ at the battery looks like 12.3 volts to the alternator regulator, and the alternator charge current will increase as a result.



Config 2- Connect the normal sense line from the alternator to the battery terminal directly. Then put a forward biased 0.7v heavy duty heat sinked diode in series within the output wire between the alternator and the battery. This will result in less charge voltage reaching the battery terminal. The charge current will remain the same, and the alternator will work as hard as a diode-less configuration, but if there is for instance an internal 13.4 volt regulator, only 12.7 volts will be present at the battery at full charge, the other 0.7 volts having been dropped across the series high current diode. The power across this diode could be as high as 60*.7 or 42 watts (DC) for a 60A alternator.


Err the whole point is to reduce the charge current. With lithium’s that means reducing the alternator output voltage to close or slightly under the lithium cell voltage.

You can ( as was pointed out ) artificially raise the sense voltage. But you need to determine what that needs to be not simply placing an arbitrary cell in series. You could rig up a pot and an external voltage to allow you to adjust the sense voltage up to the point where the alternator will reduce field currents.
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Old 15-11-2021, 08:53   #80
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Re: Alternator burn out charging lithium

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...

Secondly if you put a diode in the charge line and then still battery sense you will make the alternator work even harder. That’s not what you want to do.
Suggesting here of "what DO we want to do"
1) don't overheat the alternator
2) charge the battery as fast as possible, without violating a requirement.
3) run a defined, two phase charge (absorption and top-off)
4) accommodate multiple chargers, at the same time. Solar, twin engines, mains to dc charger, etc.

I don't think this is possible without a computer, albeit a simple one, but mated to at least 4 analog inputs. Talt, Tbatt, I, Vbatt.

The larger the battery, and the smaller the alternator, will highlight the deficiencies.
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Old 15-11-2021, 08:57   #81
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Alternator burn out charging lithium

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Originally Posted by team karst View Post
Suggesting here of "what DO we want to do"

1) don't overheat the alternator

2) charge the battery as fast as possible, without violating a requirement.

3) run a defined, two phase charge (absorption and top-off)



I don't think this is possible without a computer, albeit a simple one, but mated to at least 4 analog inputs. Talt, Tbatt, I, Vbatt.


If you have a smart alternator regulator then you don’t need any of this as the set point will be adjustable and the regulator will no doubt sense case temp

The issue is specifically about lithium. Hence with a standard regulator the set point is simply too high and as a result the alternator puts out too much current

There is no proper absorption phase of any duration in lithium’s. You charge at CC followed by CV with CV set to to the just above cell voltage. This period is relatively short.

Since we want to lower the alternators output a diode in the charge line is a simple method. It’s crude and no substitute for a proper regulator.
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Old 15-11-2021, 09:09   #82
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Re: Alternator burn out charging lithium

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Originally Posted by goboatingnow View Post
If you have a smart alternator regulator then you don’t need any of this as the set point will be adjustable and the regulator will no doubt sense case temp

The issue is specifically about lithium. Hence with a standard regulator the set point is simply too high and as a result the alternator puts out too much current

There is no proper absorption phase of any duration in lithium’s. You charge at CC followed by CV with CV set to to the just above cell voltage. This period is relatively short.

Since we want to lower the alternators output a diode in the charge line is a simple method. It’s crude and no substitute for a proper regulator.
It appears you are trying to take a CV design, and turn it into a CC source. And, I know you know how different they fundamentally are.
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Old 15-11-2021, 09:55   #83
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Re: Alternator burn out charging lithium

Thanks for all your inputs, haven't had time to do the test yet, I am not suggesting anyone to try any of the above at the moment it is all experimental, I have the ability to try a few things eg I have a adjustable resistance (experimental) in my alternator field circuit so I can manually protect my alternator to a set temperature. I can manually increase my sense voltage (like I presume Nordkyn do) which puts the normal built in regulator to the absorb phase (lower voltage eg lower current phase)
Please note I am not on the water so nothing I do is dangerous.
My alternator is a normal simple automotive 85 amp Bosch BXF unit with a battery sensed RE60 reg. driving a 400 A/H CA400 CALB 12v LiFep04 battery via a Victron BMV 712 Blue Tooth shunt and I can monitor things correctly.
Will let you know how I go, will get back in a couple of days & try and post a couple of pics - Thanks - Leigh
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Old 15-11-2021, 10:11   #84
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Re: Alternator burn out charging lithium

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It appears you are trying to take a CV design, and turn it into a CC source. And, I know you know how different they fundamentally are.


An alternator like most battery chargers is designed to operate out of regulation , a power supply for example would shut down if it could not maintain regulation

Hence out of regulation you essentially have a CC source. Once regulation restarts , you have a CV source. This is a feature of the regulator.
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Old 15-11-2021, 10:32   #85
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Re: Alternator burn out charging lithium

Oh, now. You have to admit that a car alternator output voltage is a LOT more stable than its output current. V will vary around 20%, but the I varies from around 60 to .1 amps in normal use.
But your point is taken, as the load V is lessened, the alternator continues to put out power; unlike something like house wiring that will suddenly give up!
At the end of the day, I will call an alternator a CV device, that is rather “soft”. It has a feedback/control loop that does not have current output as a target value in the equation.
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Old 15-11-2021, 14:24   #86
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Re: Alternator burn out charging lithium

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Originally Posted by goboatingnow View Post
Good god do people not read

A diode in the charging circuit SENSED ON THE ALTERNATOR SIDE will not change the alternator set point. The lower voltage will result in the alternator supplying less current. Most alternators on boats ARE not battery sensed anyway.

Secondly if you put a diode in the charge line and then still battery sense you will make the alternator work even harder. That’s not what you want to do.
That is what config 1 is.

.
.
That is what config 2 is.


Agree

Calmage.
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Old 15-11-2021, 15:54   #87
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Re: Alternator burn out charging lithium

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Originally Posted by team karst View Post
Oh, now. You have to admit that a car alternator output voltage is a LOT more stable than its output current. V will vary around 20%, but the I varies from around 60 to .1 amps in normal use.
But your point is taken, as the load V is lessened, the alternator continues to put out power; unlike something like house wiring that will suddenly give up!
At the end of the day, I will call an alternator a CV device, that is rather “soft”. It has a feedback/control loop that does not have current output as a target value in the equation.
Voltage source by definition do not control current.
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Old 17-11-2021, 15:49   #88
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Re: Alternator burn out charging lithium

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Voltage source by definition do not control current.
E=IR, they are interdependent with the rest of the circuit seeing the battery voltage is as part of the circuit resistence.
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