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Battery Charging Issue


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Yep, thats a good alt. Here is another - The Balmar 6 series...

Am I missunderstanding what you are saying IT? Because isn't that what I have said. Or dd I not say it well?

Even driving at 2 to 1, th engine at 1300RPM, the ALT at 2600rpm, that Balmar is going to be producing 50%(ruffly) of it's max output. About 75%(ruffly) at 2000 eng.rpm /4000ALT.rpm.

 

FLA and AGM can stand higher providing temperature is monitored and compensated for. Gel is one that excessive charge current will kill it. In fact 25% is probably too much and I would be pulling that back to 20% of the total battery capacity. This is because gassing causes bubbles in the Gel which them lifts the Gel away from the plates and the Battery loses it's ability to charge and produce current. FLA and AGM is is far more accepting, but because AGM is not " flooded" with electrolyte, it does not have the luxury of cooling like FLA and needs temp monitoring. FLA likes hard charging to a point. As long as it does not over heat, hard charging keeps the electrolyte stirred up and the plates cleaner from Sulphate. Hard charging can mean monthly equailization charging does not really need to be done. But regular checks of electrolyte needs to carried out and care not to overheat the battery while charging.

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The way I see that graph, and the performance of the actual alternators, take the red line. At 1:2, so 2600 engine revs, the alternator produces around 50-52 Amps indefinitely. Most automotive alts dont really get going to 2000 engine rpm, so what I'm saying is that the marine ones start up at lower speeds.

Lower speeds, like motor sailing, have much more use for charging than other alts.

Pulley ratios should be adjusted where needed.

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The guy installing the set up in the cat asked if I wanted to go to 1:3 ratio.

That is fine at 2000 rpm but means you can't motor at 3000 rpm + for long without giving the alternator a hard time.

There are times when cruising (getting in that reef pass before dark) when you really want to.

We accepted the lower performance and stayed with 1:2

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Keep in mind here I have a system that is all the same brand and has been designed to work together.  It's all mastervolt gear.  Anyhow nothing like getting up there and taking a look, I suspect it's the batteries as age is unknown.  

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Understood. However, if your battery splitter is a diode type, and you cannot adjust the voltage for the loss in the splitter, your batts will NEVER have been properly charged, and that will cause (may have caused already) premature battery failure. If it is a diode splitter and this is the case, you either need to change the regulators, OR you need to remove the splitter and replace it with  more modern system - like a VSR...

That being said, I use a diode splitter myself. My shore-power battery charger is 3 bank capable and goes direct to the batts, not via the splitter. My alt output is controlled by an Ample Power 3 stage external reg that has adjustable voltage, so the diode loss is compensated for.

Yours could be the same/similar, every boat is a bit different!

If it were me, I'd remove the batts and do a proper 20 hour capacity test on them to see where you are starting from. It's easy to waste quite a few $ changing stuff that's not broken, or that's broken because of another issue, so the replacement will fail as well!

Good luck!

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If it is a Mastervolt unit, they use FETS and thus no voltage drop. So there will be no problem there. I still prefer a splitter like those units over a VSR. I certainly wouldn't call them a more modern system though.

I 100% agree that a proper 20hr test is required to get a proper and accurate result. A Battery load tester is often misused by many and often used to sell new batteries to unknowing customers. Unless the battery has been properly charged and the Load tester is a real McCoy digital device, then all these thing will tell you is the battery is not giving what is written on the side and that is then used to sell the customer a new one.
 

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So just heard from last owner batteries were new in 2012 hence potential problems I'd suggest.... I'd consider these old?  
 

My battery isolator is some fangled thing that says no or very low charge voltage loss, one of these:  http://www.studer-innotec.com/en/products/battery-splitters-mbi-series-12-24v/

 

Manual says "The Battery Isolator has no voltage drop when the batteries are fully charged. This is achieved by using the latest electronic technologies, other diode splitters have at least a voltage drop of 0,7 Volt and at a high charging current this voltage drop can reach 1,5 Volt.

The voltage drop of the Battery Isolator will never exceed 0,4 Volt at max amperage. At a charging current of 20 Amps. per battery, the voltage drop is negligible.

 

I'm thinking it's replace batteries time???

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The specs for that unit state 

 

  • Voltage drop

So, consider that a fully charged FLA batt is 12.8v, but at 12.5 its 50% down. Half a volt is a LOT.Those batts are 5 years old, but may never have been fully charged by the alternator. Does the solar charger go via the splitter? What about the shore power? 

While it is likely the batts are tired, you dont know for certain.Your call, but personally even though I might make the call to replace, I'd still want to make absolutely certain that the new ones are being charged properly. A good multimeter  to check the batt voltage -AT THE BATTS - when charging will tell you whats up.

Your call of course, good luck!

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So just heard from last owner batteries were new in 2012 hence potential problems I'd suggest.... I'd consider these old?

Mine went in in 2004. Still going strong.

 

The Studor is a great splitter, probably the best on the market. They use the MOSFET as I said earlier. 0.04V is the max voltage drop at 100A which even with an 800Ahr bank, would only be seen during Bulk charge stage. However, this os compensated for anyway. You will see that the ALT " sense" wire is connected to the splitter and the splitter than adjusts what the ALT " sees" as it's output voltage. When the Charge is down in a much lower absorbtion stage, the current loss is virtually nill and once again, the sense control is compensated for any loss.

 

SM, the most important thing to keep Batteries living as long as possible is to ensure they are not flattened to far, too often. The second important thing is to insure they are fully charged again. But this " fully charged" part is often never understood by many and it is essential that the user reads the information the monitor tells them and allows the Battery to always reach Float mode. Which many Cruisers never do because getting that last bit in takes the longest amount of time. And often it is thought the Solar/wind or whatever will top the bank up anyway. However, the Bank never reaches full and as soon as that main charger is turned off, the bank is being used and thus dropping and on the cycle goes.

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Wheels you are right on there.  The main issue is that we hardly run the motor preferring to sail everywhere.  Therefore we are relying on two solar panels to keep batteries charged.  That is not been helped by the reduced output from the alternator, however my main concern is that this was all working back in NZ but the alternator output has reduced.  

 

Anyhow I'll get up there and take a look and sort it.  Arrive tomorrow, can't wait to get out of the cold weather!!

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I'm in Fiji today and it's actually quite cool this morning. If you live aboard and anchor out a lot 5 years is pretty good.
Sure you can run the engine forever and make them last longer. Or stay in marinas more and plug in.
Probably cheaper and a lot more fun to enjoy your boat and swap the batteries every five years or so.

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Now this thread is getting long, I am forgetting which thread had the comment about Solar panel voltage upsetting ALT charge voltage. I don't think it was answered anyway. Yes, voltages from different sources will upset the Charge current from the ALT. As we all know, the ALT is controlled by the sense wire that measures the voltage of the battery. Even with a smart reg on the ALT, the charge can be upset by some other device lifting the Battery Voltage. So the ALT does not poke in a good current. That is not to say the Battery is not being charged, but the Current being read on the display will be showing a lower figure from the ALT. The only way this can be compensated for is a display that has all charging sources running through it. Depending on how clever it is, this info could be a very simple calculation of current in/out over time, or the more clever units will perform complex calculations based on the offsets like Purkets law.

Another point I am not clear on and just popped back to the beginning question. So the batteries are standing at 13V at rest? Are they lasting the time they normally should while supplying all the boats electrical needs? It could well be that the reason the ALT is inky providing the lower Voltage level is that the Batteries are not discharged. They may only be 25% down rather than 50% down.

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