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Old 02-08-2014, 09:36   #91
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Re: Alternator does not Fully Charge the Batteries

Doucement, says the French. Well, of course this is true but the overall situation is completely different compared to the case without Sterling, where I did not get ANY absorption charging at all (see the beginning of this long thread).
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Old 03-08-2014, 05:12   #92
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Re: Alternator does not Fully Charge the Batteries

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Doucement, says the French. Well, of course this is true but the overall situation is completely different compared to the case without Sterling, where I did not get ANY absorption charging at all (see the beginning of this long thread).
Tuomas - there seems to be an awful lot of arm chair science going on here in this enormously long thread but I see very little hard empirical data which is far more valuable than dubious theory. From having troubleshot charging issues in my motorboat and now on my yacht all I can add is a couple of suggestions, alternators on their own are terrible battery chargers:

1. Make sure your alternator is working properly, any good auto electrician can do that for you. Get it off and get it tested professionally.
2. Install a field sense wire per Sterlings instructions, maybe the techie can do that for you while he's testing it. This is different from the voltage sense you have connected to your house batteries.
3. With the alternator installed and working 100%, install one of the two Sterling external alternator regulators and hook it up.
4. Test charge rate with with the external regulator activated and with it deactivated - if you've got it setup right there will be no mistaking the extra charge being pushed into the batteries, you will say "wow"

Properly installed the Sterling does not "fire" the alternator, it should be doing that itself i.e. it must be working with the Sterling on or off. Both regulators must be active during run - I verified that with Sterling, ping him if you want to double check that.

If that doesn't fix the issue I'm willing to bet either the alternator is faulty or the Sterling is incorrectly installed (or guess 1000:1 chance the Sterling may be faulty)

I can tell you from 1st hand experience the external alternator regulator makes a huge difference to your overall charge system, no arm chair science just direct observation. I measure it on how long and how cold the beer is when it's almost 40c on the water - it works. I don't care about to what % my batteries are charged, I care about how long they power my fridge.

Lastly: Alternate solutions could be an Alternator to Battery charger or a Battery to Battery charger. I haven't tried either but according to Sterling they deliver the same result. They are several times more expensive than an external alternator regulator but then again one went on eBay just this week for 38.

12V 80A Alternator-Battery Digital Split Charge System (Boxed) | eBay
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Old 03-08-2014, 11:21   #93
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Re: Alternator does not Fully Charge the Batteries

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Originally Posted by nugeo View Post
Tuomas - there seems to be an awful lot of arm chair science going on here in this enormously long thread ....
....I don't care about to what % my batteries are charged, I care about how long they power my fridge....
I'm sorry if you don't believe, or maybe understand the science, but if you only use you batteries from 50 to 90% SoC that means you are NOT using 20% of your available capacity. If you used it all then your fridge would be powered 20% longer before you have to re-charge the batteries.

If you are only using your engine to charge the batteries then once you get to about 80% SoC the charge current falls away very quickly and it's just not worth running the engine anymore. So now you are about 40% down on how long your fridge will run!!!

All these figures can be verified in the real world on real boats.
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Old 03-08-2014, 14:10   #94
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Re: Alternator does not Fully Charge the Batteries

I hope this does not get messy... Anyway, I am happy with my Sterling, happy with my perfectly working alternator, happy with my battery monitor, happy with my amphr consumption and production and happy with my new batteries that will most likely stay good for many many years. My power is balanced
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Old 04-08-2014, 00:37   #95
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Re: Alternator does not Fully Charge the Batteries

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All these figures can be verified in the real world on real boats.
I'm no scientist and I'm the first to put my hand up and tell you the chemistry involved in LA batteries is to complex for me to want to even to try and understand it. What I write is simply what I see and there is no way I'm down 40% of available power when comparing an overnight shorepower battery recharge with for arguments sake 2hrs or so of engine time, it simply isn't the case. I accept there probably is some deficit but to say I'm down by almost half is over cooking it by quite a bit.

Having said that if you do have empirical data that you've gathered please post it, I genuinely am interested in seeing what tests you did and what the results are. I'm not for a minute suggesting I have all the answers.
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Old 04-08-2014, 00:46   #96
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Re: Alternator does not Fully Charge the Batteries

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I'm sorry if you don't believe, or maybe understand the science, but if you only use you batteries from 50 to 90% SoC that means you are NOT using 20% of your available capacity. If you used it all then your fridge would be powered 20% longer before you have to re-charge the batteries.

If you are only using your engine to charge the batteries then once you get to about 80% SoC the charge current falls away very quickly and it's just not worth running the engine anymore. So now you are about 40% down on how long your fridge will run!!!

All these figures can be verified in the real world on real boats.
I'm sorry SL - I got lost - How are you deriving the 20% and 40% figures?
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Old 04-08-2014, 03:50   #97
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Re: Alternator does not Fully Charge the Batteries

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I'm sorry SL - I got lost - How are you deriving the 20% and 40% figures?
Sorry if I didn't explain it fully.

If your batteries only get to 90% SoC that maybe doesn't sound too bad 'cos you're only 10 % down on fully charged. But your useable battery capacity is from 50-100% - so for a 100Ah battery you only have 50Ah that you can use. If you only charge to 90% then you only have 40Ah that you can use. 40Ah is 20% lower than 50Ah.

Take the worst case scenario of using your alternator or even a generator to charge the batteries - when you get to the absorption voltage the batteries are maybe 80% charged, so you are only using from 50-80Ah = 30Ah. 30Ah is 40% down on the 50Ah you could be getting from a 100% full 100 Ah battery. This is why when sizing a bank for your known Ah usage it's best to add 40% to the capacity if you know that most of the time you are only charging with an engine.

In the real world most banks never get to 100%, even those here who think they are getting fully charged on shorepower overnight should look very carefully at their charging system. If you go into a marina at 2000hrs and leave at 0800 hrs the next morning and you only have a small AC charger then there is a good chance you are not fully charged. Turn the charger off and back on. It will go back into absorption mode and quickly reach about 14.4v. If the charging current rises significantly from that in Float mode then the batteries are not fully charged. A current of 0.5% of the battery capacity means they are fully charged.
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Old 04-08-2014, 04:18   #98
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Re: Alternator does not Fully Charge the Batteries

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Originally Posted by nugeo View Post
.... .there is no way I'm down 40% of available power when comparing an overnight shorepower battery recharge with for arguments sake 2hrs or so of engine time, it simply isn't the case. I accept there probably is some deficit but to say I'm down by almost half is over cooking it by quite a bit.
Available AH is from 50% SOC to 100% SOC. Engine charging is not efficient after the batteries reach about 80% SOC as the last 20% takes a very long time - figure 6 to 8 hours - as the batteries' internal resistance increases and they accept less and less current. That is why long term cruisers charge to 80% with the engine and let solar or wind gen do the rest. 20% of total AH is 40% of available AH.

Overnight shorepower charging will fully charge a bank (assuming a large enough charger) or get very close. The last 6 to 8 hours is very slow.
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Old 04-08-2014, 04:21   #99
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Re: Alternator does not Fully Charge the Batteries

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Originally Posted by sailinglegend View Post
Sorry if I didn't explain it fully.

If your batteries only get to 90% SoC that maybe doesn't sound too bad 'cos you're only 10 % down on fully charged. But your useable battery capacity is from 50-100% - so for a 100Ah battery you only have 50Ah that you can use. If you only charge to 90% then you only have 40Ah that you can use. 40Ah is 20% lower than 50Ah.
OK got it - thanks...
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Old 04-08-2014, 07:16   #100
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Re: Alternator does not Fully Charge the Batteries

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It will go back into absorption mode and quickly reach about 14.4v. If the charging current rises significantly from that in Float mode then the batteries are not fully charged. A current of 0.5% of the battery capacity means they are fully charged.
Possibly a bit dogmatic, the idea the chemical processes in lead acid battery being "over" could be a bit misleading. Though most research points to 14. mid teens with 0.5/1% capacity current going in as a good ballpark, and you didn't mention temperature compensation which is also important.
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Old 04-08-2014, 16:00   #101
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Re: Alternator does not Fully Charge the Batteries

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Possibly a bit dogmatic, the idea the chemical processes in lead acid battery being "over" could be a bit misleading. Though most research points to 14. mid teens with 0.5/1% capacity current going in as a good ballpark, and you didn't mention temperature compensation which is also important.
Temperature compensation is of course very relevant, but I was trying to keep things simply which can often lead to more questions than answers.

So at 14.4v with a charge current 0.5% of battery capacity the battery is generally considered to be fully charged. So what is happening with the remaining 0.5% of charging current?

At 14.4v at 25deg C the battery starts to gas slightly, (at only 40 degC a battery gasses at 13.98v.) 'Science' tells us that every 10 degC rise in temperature reduces the battery life cycles by half.

Batteries need to gas slightly to stir up the electrolyte and evenly distribute the acid concentration. If when fully charged the voltage is left at 14.4v and not dropped to Float then the current is not charging but causing more aggressive gassing. This is what you should call 'overcharging' - too high a voltage for too long. Gassing is not good for sealed batteries. That is why some battery manufacturer's warrantee is conditional on multi-stage chargers reduce the voltage to Float when the batteries are fully charged.

So this begs the big question why doesn't my car alternator 'overcharge' my car battery?

Older alternators were always set to a voltage below the gassing voltage, modern alternators may be 14.4v or higher, but they now have temperature compensation which reduces the charging voltage as the battery temperature rises. A modern 14.4v alternator may easily reach 90 degC under heavy load and the temperature compensation will soon take the voltage down well below the gassing voltage.

On a boat with the same automotive alternator there's a problem because they only measure the alternator temperature and assume the battery is in the engine compartment, so the battery bank is likely to be severely undercharged. Deep cycle batteries need an external regulator with temperature compensation to charge them properly and extend their life.

If you don't mind replacing your batteries well before their natural life cycle then none of the 'science' really matters, especially with cheap batteries, but with quality batteries like Trojans that need a 14.8v absorption voltage and a 13.2v Float then correct charging will maybe get 7-10 years out of them. My Lifeline AGMs are now 10 years old and still going well.
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Old 04-08-2014, 17:03   #102
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Re: Alternator does not Fully Charge the Batteries

Lots of good info in this thread.
I'm no battery specialist. I have a bit of time working on these systems though.

I just wanted to say,that in my experience, the best single change you can make to a system charging deep cycle bats is to go to a proper, external 3 stage, temp compensated regulator.
Yes, I know it "might" kill your alternator from overwork, and if it does, you'll be up for a new one. However, it might not happen - I ran a standard ingram 55 amp (If I remember correctly) for 6 years, including liveaboard, with no issues. I still have it as a spare, but upgraded to a balmar alt as it does not need so many revs to charge well.
If it kills your alt, replace it with proper, hot rated alt.
Oh, by the way, I have an Amplepower external regulator. Had it for 13 years, never had an issue, works great.
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Old 04-08-2014, 23:58   #103
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Re: Alternator does not Fully Charge the Batteries

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Originally Posted by tuomas View Post
I hope this does not get messy... Anyway, I am happy with my Sterling, happy with my perfectly working alternator, happy with my battery monitor, happy with my amphr consumption and production and happy with my new batteries that will most likely stay good for many many years. My power is balanced
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Old 01-11-2014, 15:57   #104
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Re: Alternator does not Fully Charge the Batteries

I need help please, with the numbers. I've followed these threads until my eyes cross. I have a 300A AGM house bank, a 60A Balmar alt (largest that will fit), ARS-5 regulator, a link lite monitor, and 5-6 hours of motoring doesn't replace the 25-30 amps I used overnight. I know my usage is high (portable freezer) I also have solar and wind charging, but travelling the ICW doesn't use them.
The lit for the regulator says the max bulk volts is 14.4, and the max absorption is 14.7, and the batteries never get the least bit warm, as I check frequently with a handheld IR scanner.
I've played around with some of the settings of the ARS-5, but I'm really shooting in the dark here.
Many thanks!
Larry
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Old 01-11-2014, 17:07   #105
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Re: Alternator does not Fully Charge the Batteries

How many amps are going into the batteries while the engine is running, according to the monitor? Have you checked the voltage at the batteries while the engine is running?


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