Alternator Charging

[boeing1]

I have a single wire alt. system. the alt was just converted back from a external regulaor. My question is it puts out 14.6 volts when charging and has charged my batteries to 13.2 volts, when does the alt reg. back off to stop charging. do I have a problem with the alt internal reg or is this normal. I would of thought it should stop charging about 12.9 13.0 but still charges at 14.6

[courageous cat]

Sound like its working right. 14.6 wood be the cut out volt then. As volts go down amps will go up and in viseavesa. at 14.6 you might be putting out only say 3 to 6 amps, but at 12.5 maybe 40 to 50 ams depending on the size of your alternator is. Other here will want to know the make and amperige of the unit (and proble ever thang else about your electrical system) just keep an eye on it,

[boeing1]

Thanks for the reply,
I was thinking that I might overcharge my batteries at 14.6
at what votage does the alt. reg. lower charging voltage

[wolfaroo]

Although it's called a voltage regulator, it actually uses voltage measurements to 'regulate' current output, so the name is a little confusing to begin with!

A constant 14.6v is perfectly normal and will not overcharge your batteries. Most 12v charging systems will provide a fixed voltage of between 13.8v - 14.8v. The current being drawn by the batteries will vary depending on their charge state.

After switching off the engine, isolate the battery and wait for >3 hours before reading battery volts, to avoid higher readings caused by surface charge. This should give you an accurate battery state. Depending on battery type & temp etc, expect a reading of between 12.8v - 14.1v.

Hope this helps.

Cheers,

Wolfaroo

[DeepFrz]

Well, there is a reason for external regulators. Internal, automotive alternator regulators will shorten the life of your house batteries considerably.

[barnakiel]

I am not clear if I got you right.

On our boat, the internal regulator does not cut off.

It keeps on charging at the upper voltage no matter what. I guess only amps get fewer as as the voltage difference drops between the alt and the battery.

External advanced regulators cut down to float once the battery is full.

b.

[djmarchand]

Well, I must disagree with some of the previous posters. 14.6 volts if accurate is way, way too high. It will overcharge your batteries and boil (disassociate actually) off water.

An internal regulator is typically set at 13.5 volts or so. This will not overcharge batteries.

A properly set internal regulator puts out a fixed voltage subject to the alternator's maximum current output capability. With fully discharged batteries the alternator will put out its max. As the batteries approach fully charged, the current will be reduced because it takes more than 13.5 volts to produce near full current into mostly recharged batteries. This reduced current will slowly fully charge the batteries but it takes a long time. That is why cruisers use external regulators.

An external, three stage regulator will push the voltage to above 13.5 volts as it tries to maintain the alternator's full output. The voltage will start low, maybe 12-12.5 with fully discharged batteries, but the voltage will rise to as high as 14-14.5 volts until the batteries are near full charge and then the regulator will switch to its float voltage of 13.5 volts just like the internal regulator.

Since your internal regulator isn't working right, I would recommend going back to an extenal regulator. Balmar and Ample Power make good ones.

David

[wolfaroo]

Originally Posted by djmarchand

14.6 volts if accurate is way, way too high. It will overcharge your batteries and boil (disassociate actually) off water....

...Since your internal regulator isn't working right... David

I'm not trying to be a PIA, honestly! But please check this info... His alternator reg IS working!

Nearly all modern automotive-type alternators output a FIXED 14.4v. Some output 14.8v. Some older type output at 13.8v, but this is often considered too conservative and will reduce the battery capacity. Whilst charging, the voltage across the terminals will increase. Initially the difference between the terminal voltage & alternator voltage will allow current to flow into the batteries. As the terminal voltage increases, the voltage difference lessens and just a trickle charge flows to keep the batteries topped up.

In order for the trickle charge to overcome the battery resistance and flow from the alternator to the battery it is recommended that the charging voltage be at least 20% higher than the battery (12v + 20% = 14.4v). This will not damage your battery. Many solar/wind regulators will output at 14.4v-14.8v too.

OP - 14.6v is within normal levels and will remain fixed while your engine is running and will not destroy your batteries.

YES an external step charger/reg is much better for charging/managing DOMESTIC batteries in the long term - NB during absorbtion stage of charging voltage may be as high as 15.5v.

Obviously there is another debate about how much longer your batteries will last with ext reg v int reg, BUT a standard alternator will do just fine for most requirements.

Finally, long-term battery deterioration as a result of using a standard alt reg is generally the result of REGULARLY supplying too much current too quickly during the early phase of charging very FLAT batteries, not from continuing to apply a constant voltage after the batteries are fully charged.

I hope this clears a few things up.

[GordMay]

Originally Posted by djmarchand

... 14.6 volts if accurate is way, way too high. It will overcharge your batteries and boil (disassociate actually) off water...

FWIW: Dissociation is the process by which a molecule separates into ions.

Originally Posted by djmarchand

... An internal regulator is typically set at 13.5 volts or so. This will not overcharge batteries ...

Nor will it fully charge batteries (not even nearly).

[DeepFrz]

Finally, long-term battery deterioration as a result of using a standard alt reg is generally the result of REGULARLY supplying too much current too quickly during the early phase of charging very FLAT batteries, not from continuing to apply a constant voltage after the batteries are fully charged.

I have never heard this but I assume this is a result of battery overheating. If you have a reference to research on your statement I would appreciate it.

External regulators can and should be equipped with temp. sensors that will protect the batteries and alternator from overheating. Overheating will quickly kill batteries and alternators.

[wolfaroo]

Originally Posted by DeepFrz

I have never heard this but I assume this is a result of battery overheating. If you have a reference to research on your statement I would appreciate it.

External regulators can and should be equipped with temp. sensors that will protect the batteries and alternator from overheating. Overheating will quickly kill batteries and alternators.

You are of course right about temperature. From memory I think charging with a very high current when a battery is in a high state of discharge will cause more overheating (and eventually lead the plates to deteriorate & buckle sooner) than when the battery is in a lesser state of discharge, due to differences in internal resistance. Most battery manufacturers will give info on safe charge rate covering all states of discharge.

This bit is too technical for me to understand (to do with chemistry) - if no-one else can explain I will have a look for a detailed reference for you.

Thanks.

[barnakiel]

Originally Posted by wolfaroo

- NB during absorbtion stage of charging voltage may be as high as 15.5v.

I hope this clears a few things up.

It might, except for the 15.5 Volt that I have never seen on the regulators I used or installed.

What is it? Some Balmar toy? Or is it a setting for some specific batteries?

I have seen 14.4 to 14.8 as the top Voltage.

b.

[wolfaroo]

Originally Posted by barnakiel

It might, except for the 15.5 Volt that I have never seen on the regulators I used or installed.

What is it? Some Balmar toy? Or is it a setting for some specific batteries?

I have seen 14.4 to 14.8 as the top Voltage.

b.

My sterling regulator is limited at 15.5v, as are many other regulators (wind & solar too - just google '15.5v' to see) There is some basic info here: LEAD ACID BATTERY CHARGING INFORMATION, BATTERY TYPES AND OPERATION - SOLAR NAVIGATOR WORLD ELECTRIC NAVIGATION CHALLENGE, NELSON KRUSCHANDL, BLUEBIRD ELECTRIC LAND SPEED RECORD CARS

and a useful voltage table here:
How to charge sealed lead acid batteries. Custom battery chargers for OEMs in a hurry from PowerStream

[barnakiel]

Look guys the info says that:

The higher voltages (above the gassing voltage) should only be used on flooded batteries that can have the water replaced.

With 15+ Volts for temperatures below freezing.

So I have to bark it back: (whof, whof) - 15.+ is fine - for low temps charging.

That's probably why I have 'never' seen it - I have been in tropics last 8 years.

A lesson taken today is a trouble spared tomorrow ;-) THX

barnie

[DeepFrz]

Remember also that your electronics are connected to the batteries while they are charging. I don't think you want 15 volts and higher at your expensive plotters, radios, etc. even if it is cold. I'm not sure what the max. voltage for those devices are (I suppose it depends on make/model ) but I doubt that voltages over 15 volts would be good for many electronic devices.