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Old 22-11-2013, 08:27   #16
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Re: Alternator does not fully charge the batteries

Don't bother taking your alternator off until you run the following test.

1. disconnect dock power
2. Start engine and run until voltage stabilizes, then run for another half hour.
3. Turn on all the electrical equipment on boat and note voltage again.

If you can put 20 amps of house load on the alternator without affecting the system voltage by more than 0.1 volts, there is nothing wrong with the alternator.
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Old 22-11-2013, 08:28   #17
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Re: Alternator does not fully charge the batteries

Quote:
Originally Posted by tuomas View Post
What's wrong/broken? Suggestions?
Perhaps nothing. We have also motored for 10 hours to put the last 30 amps into a 220 AH bank. The fact is the alternator output starts of high then quickly drops down to single figures because that's all the batteries can absorb at our 14.2v.

Stick on an external regulator and raise the voltage as Mitiempo says.

Sterling Power Products: Alternator Regulators

This is worth a read:

http://www.sterling-power.com/support-faq-1.htm

Just check you have cool air flow to the alternator.

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Old 22-11-2013, 10:25   #18
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Re: Alternator does not fully charge the batteries

Interesting, seems I have to re-learn a few things
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Old 22-11-2013, 10:34   #19
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Re: Alternator does not fully charge the batteries

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Originally Posted by mitiempo View Post
...My point was that an external 3 stage regulator will not charge any faster than a built-in dumb reg as long as the bulk/absorption voltage is the same.....
Nobody said it would !!!!! There are many other very good reasons why you should fit an external regulator, even if your internal regulator is producing 14.4 volts.

1. With sealed batteries all battery manufacturers recommend an external regulator which will drop the charge down to float mode at 13.2-13.8 volts to avoid gassing and overcharging.

2. A good regulator will delay the charge current for about a minute at start up until the engine oil is well distributed. A 100 amp alternator draws 4 HP which is a heavy load on an engine when starting with a weak battery.

3. It is often too easy for the alternator on a boat to get too hot if used for long periods. A good external regulator will also accept a sensor to measure the alternator temperature and control the charge rate. Even a 100 amp alternator could be providing 15 amps to the boat systems, another 25 amps to say a watermaker or an inverter, and then a heavily discharged bank may be demanding 50 or 60 amps. In this situation the batteries may not get charged and the alternator will burn out from continually trying to deliver its maximum output if not protected by a temperature sensor.

4. A good external regulator will also accept a sensor to measure the battery temperature which will rise with a heavy charge current. At 25C batteries start to gas at 14.4v, at 40C they gas at 14v so the external regulator will reduce the charging voltage automatically to compensate for this. If batteries are fitted in an engine compartment it is very easy for them to get too hot and lose water. This is fatal for sealed batteries.

5. A good regulator should have setting for different battery types, but it should also be programmable to match the alternator and battery bank sizes. Balmar's regulators allow many parameters to be changed, for example they may set the Boost voltage to 14.6, hold that for 45 minutes and then reduce it to 14.4 for the duration of the absorption stage. They can be programmed to stay longer in the absorption stage without dropping down to float too early.

6. A good alternator will have a voltage sensor at the battery not on the alternator. This will compensate for split diodes or losses on cable runs to the battery.
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Old 22-11-2013, 17:18   #20
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Re: Alternator does not fully charge the batteries

When my fully charged batteries drop to 12.5V (or even 12.4V) immediately after charging it usually means the fridge is running.
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Old 22-11-2013, 17:29   #21
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Re: Alternator does not fully charge the batteries

"1. With sealed batteries all battery manufacturers recommend an external regulator which will drop the charge down to float mode at 13.2-13.8 volts to avoid gassing and overcharging."

There's sealed aka VRLA and there's sealed as in simple "maintenance free" sealed wet lead batteries. Almost all of todays VRLA batteries are AGMs that are in fact designed to run with a 14.4 volt "dumb" alternator and they'll work quite happily with it, as designed. (Gels are of course something else, they're not designed for 14.4 volts.)

And while smart regulators are better than the integral ones every time, the battery makers don't tell folks to run out and buy one "or else". They just accept that the battery life will be less than optimal, which is normal even with an external regulator that doesn't have temperature compensation or other frills.
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Old 22-11-2013, 17:36   #22
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Re: Alternator does not fully charge the batteries

how long after stopping was it 12.5 volts? That sounds typical to me. Dont expect your battery to stay at 13 volts.... I have a small powerboat I use around the bay. It got brand new batteries this summer. after a day of motoring and charging, the next day it wil be a bout 12.5 volts after sitting for the night and nothing on.
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Old 22-11-2013, 17:52   #23
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Re: Alternator does not fully charge the batteries

Plus what are you using to measure the battery voltage? I have a 0.1 difference between the battery monitor and a simple digital battery meter. Perhaps the batteries are full.

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Old 22-11-2013, 19:10   #24
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Re: Alternator does not fully charge the batteries

Quote:
Originally Posted by sailinglegend View Post
Nobody said it would !!!!! There are many other very good reasons why you should fit an external regulator, even if your internal regulator is producing 14.4 volts.

1. With sealed batteries all battery manufacturers recommend an external regulator which will drop the charge down to float mode at 13.2-13.8 volts to avoid gassing and overcharging.

2. A good regulator will delay the charge current for about a minute at start up until the engine oil is well distributed. A 100 amp alternator draws 4 HP which is a heavy load on an engine when starting with a weak battery.

3. It is often too easy for the alternator on a boat to get too hot if used for long periods. A good external regulator will also accept a sensor to measure the alternator temperature and control the charge rate. Even a 100 amp alternator could be providing 15 amps to the boat systems, another 25 amps to say a watermaker or an inverter, and then a heavily discharged bank may be demanding 50 or 60 amps. In this situation the batteries may not get charged and the alternator will burn out from continually trying to deliver its maximum output if not protected by a temperature sensor.

4. A good external regulator will also accept a sensor to measure the battery temperature which will rise with a heavy charge current. At 25C batteries start to gas at 14.4v, at 40C they gas at 14v so the external regulator will reduce the charging voltage automatically to compensate for this. If batteries are fitted in an engine compartment it is very easy for them to get too hot and lose water. This is fatal for sealed batteries.

5. A good regulator should have setting for different battery types, but it should also be programmable to match the alternator and battery bank sizes. Balmar's regulators allow many parameters to be changed, for example they may set the Boost voltage to 14.6, hold that for 45 minutes and then reduce it to 14.4 for the duration of the absorption stage. They can be programmed to stay longer in the absorption stage without dropping down to float too early.

6. A good alternator will have a voltage sensor at the battery not on the alternator. This will compensate for split diodes or losses on cable runs to the battery.
I did not say that there are not advantages to an external 3 stage regulator.

Actually you missed one feature anyway - some like Balmar's MC-614 allow you to dial the alt output back to say 70% output. A 100 amp alt at 70% will last longer than a 70 amp alt at max output.

As well #1 is not really an issue - if it were the batteries in millions of cars and trucks would boil and not last very long as they are at 14.4 all the time the engine is running.
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Old 23-11-2013, 01:21   #25
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Re: Alternator does not fully charge the batteries

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Originally Posted by mitiempo View Post
I did not say that there are not advantages to an external 3 stage regulator.

Actually you missed one feature anyway - some like Balmar's MC-614 allow you to dial the alt output back to say 70% output. A 100 amp alt at 70% will last longer than a 70 amp alt at max output.

As well #1 is not really an issue - if it were the batteries in millions of cars and trucks would boil and not last very long as they are at 14.4 all the time the engine is running.
Actually Not, Most modern autos are 14 v at the alternator output, after load and voltage drop somewhere around 13.8.

Every time I go to Blanchard Auto Electric, they say I am defeating the design by increasing the charge cable size to reduce V-drop.

Auto alts are designed to act as power supplies, not as battery chargers. There is not an automotive system in use/design that includes hotel loads on the battery/charge, as the primary function.

They are all by design SLI systems....period.

Thats why most auto stero stores will not sell you a system without an upgraded 2nd alt system.

Lloyd
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Old 23-11-2013, 02:22   #26
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Re: Alternator does not fully charge the batteries

Quote:
Originally Posted by mitiempo View Post
...As well #1 is not really an issue - if it were the batteries in millions of cars and trucks would boil and not last very long as they are at 14.4 all the time the engine is running.
This is always an interesting and controversial argument that people use to justify why they don't really need to spend more money or their boat. Yes you are correct, my #1 reason may be slightly misleading or mis-worded. But there is no denying that allowing fully charged sealed batteries to sit at 14.4v volts for hours and hours whilst motoring will cause excess gassing and drive another nail in their coffin and reduce their life.

In reality what is really happening in a car; the 14.4v will quickly be reduced by the simple temperature sensor in the alternator and by the loads from lights, instruments air-con etc., etc.. so the batteries are not getting excessive voltage for too long.

But there is a big difference between charging starter batteries in a car, and a large deep cycle service bank in a boat. You leave a dock with fully charged batteries, you have solar panels providing enough current to run the instruments, and you have a large alternator that is doing virtually nothing so it is not getting hot. It will reach engine compartment temperature but not normal alternator temperature so its temperature sensor will not reduce its output. So it MAY be sitting there producing 14.4v volts for hours when its not needed.

Alternatively it could be charging flat batteries and getting hot enough to reduce its charging voltage, because it thinks the battery is close by in the engine compartment. This shouldn't happen on a boat, sealed batteries especially should be well away from the engine compartment, so they will see a lower voltage than they need once the alternator has warmed up. This will lead to severe undercharging.

The Bavaria next to me yesterday asked me to look at his battery problem. The alternator on his Volvo was outputing 14.9v, via Split Diodes, to the batteries in the saloon where the voltage was 14.1v. So the internally regulated alternator was undercharging his batteries. At least the regulator did have a battery voltage sense cable which was trying to get a decent voltage to the batteries.

These were Delphi Freedom which need 14.8v or more - one had died prematurely due to severe undercharging!!! I didn't have a chance to see what the voltage was when the engine first started, but without an external regulator the batteries were never going to get their correct voltage.

So my #1 Reason for having an external regulator should now read:

1. An external regulator may help reduce overcharging due to excessive gassing, and reduce undercharging due to bad voltage and temperature regulation.

It is worth noting that with sealed batteries most battery manufacturers recommend that you use a multi-stage regulator to drop the charge down to float mode at 13.2-13.8 volts to avoid gassing and overcharging. This is a condition of the warranty on some batteries.

Perhaps this should be changed with #5, so my#1 reason becomes - A good regulator should have setting for different battery types.......
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Old 24-11-2013, 02:58   #27
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Re: Alternator does not fully charge the batteries

Thanks for further posts.. My judgement on the state of the batteries is based on the fact that after a shore charger I get 12.7 volts to the bank but some ten hours after the ten hour drive I got 12.5 volts in the bank, indicating a charge level of some 70-80%. All measurements are made with the same Nasa battery monitor as indicated in the original post.

Further symptoms indicating problems in the battery and/or charging:
-intuition that motor driving does not charge batteries as it used to do (I installed the monitor only on July)
-drawing 7 amps for the heater lowered the bank voltage to 12.0-12.1 volts (may also be due to battery temp of about +5 celsius).
- unexplained more than self-discharging battery drainage even with main switches open during longer idle periods (may point to a faulty rectifier; the main switches do not disconnect the alternator from the batteries).

Anyway, the alternator is easy to remove and have tested.
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Old 24-11-2013, 09:53   #28
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Re: Alternator does not fully charge the batteries

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... unexplained more than self-discharging battery drainage even with main switches open during longer idle periods...
This is a symptom of battery sulfation. See last sentence of sixth paragraph here: Sulfation and How to Prevent it - Battery University

By the way, check the rest of this website for battery care, lots of good information. Just click on all those items on the left of the screen.

If you have a bad alternator, sulfation is likely to occur because the alternator does not put out enough voltage to charge the battery all the way; therefore, with battery at partial state of discharge for a long time, you get sulfation. My experience with a battery at 70% state of charge is that with over charging with a manual charger at a few amps, it will bring the battery back to full charge, or maybe half an amp if you have a charger that will allow that rate would be easier on the battery. However, there is a problem with overcharging. The life of the battery is shortened from gassing. The bubbles formed from the excessive voltage, will erode the plates causing them to disintegrate with material falling to the bottom of the battery eventually shorting a battery cell. One cell will fail first so you need a way to check each one individually. If you do not have a sealed battery, you can check it with this: Amazon.com: Dorman 9-1302 Hydrometer: Automotive For an accurate reading, tap the hydrometer to get to bubble off the float inside the hydrometer. If the battery was recently charged, bubbles are there from the breakdown of water into hydrogen and oxygen. By the way, always unplug the charger before you take the clips loose from the battery posts to prevent sparks. When charging, especially over charging to the point of lots of bubbles, the hydrogen and oxygen are developed and are explosive. You do not want the acid in the battery in your eyes or the rest of you for that matter. It's 32% sulfuric acid. So avoid sparks when taking the charger off a battery. Unplug the charger first.

When changing to new batteries, I always wear old clothes. Synthetic fabric holds up well, cotton gets holes in it. I have gone as long as seven years with batteries showing full state of charge. Maybe it is possible to go longer, but one shorted cell can discharge all the batteries in the battery bank, so changing out sooner would be prudent. If you want to push the battery life to the maximum, then test each cell on a regular basis. Come to think of it, I should go check the cells on my battery bank with the hydrometer! The battery voltage can look fine, but a hydrometer can spot one cell partially discharged that's falling apart internally.
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Old 24-11-2013, 10:31   #29
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Re: Alternator does not fully charge the batteries

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Originally Posted by sailinglegend View Post
This is always an interesting and controversial argument that people use to justify why they don't really need to spend more money or their boat. Yes you are correct, my #1 reason may be slightly misleading or mis-worded. But there is no denying that allowing fully charged sealed batteries to sit at 14.4v volts for hours and hours whilst motoring will cause excess gassing and drive another nail in their coffin and reduce their life........
Here is some more to add to what you are saying from a radio amateur site for mobile users. The whole website has a lot of info: Alternators & Batteries
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Old 25-11-2013, 12:38   #30
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Re: Alternator does not fully charge the batteries

Quote:
Originally Posted by sailinglegend View Post
This is always an interesting and controversial argument that people use to justify why they don't really need to spend more money or their boat. Yes you are correct, my #1 reason may be slightly misleading or mis-worded. But there is no denying that allowing fully charged sealed batteries to sit at 14.4v volts for hours and hours whilst motoring will cause excess gassing and drive another nail in their coffin and reduce their life.

In reality what is really happening in a car; the 14.4v will quickly be reduced by the simple temperature sensor in the alternator and by the loads from lights, instruments air-con etc., etc.. so the batteries are not getting excessive voltage for too long.
I am not justifying not buying and fitting an external regulator - as stated they have many benefits and are essential with a large bank of Agm batteries for alternator lifespan.

But I will stick to my statement that millions of cars run at 14.4 volts alt output or close to it all the time, without adverse effect.

Measured mine yesterday - 14.43 at the battery cold and 14.21 at the battery when hot - with fan and light loads on.
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