Battery Charging Issue

[southernman 73]

Guys,

 

I need help to fault find a battery issue.  Setup is:  

 

2 x Mastervolt 160 Amp hour batteries

1 x Mastervolt Alpha Pro Regulator

1 x Mastervolt Alpha 90 Alternator 

1 x Battery Splitter and brand new start battery

 

So the problem is this, Alternator used to charge batteries at approx. 80 amps no stress at all depending on RPM.  Now i'm only getting 30 to 40 amps.  

 

Voltage sensing wire is wired to house batteries so it's getting the correct voltage, the regulator seems to work ok too, certainly no fault lights etc.  

 

So I have made sure and the alternator is charging, voltage good, alternator seems good, belt nice and tight.  

 

Age of batteries is unknown, but when on shore charger they easily take 60 - 80 amps no stress at all.  Voltage holds when they are not charging, over 13.0 volts.  

 

So my question is being that the setup is Fiji and getting someone reliable up there is a bit hit and miss, what can I do to fault find more than I have done?  Or does anyone know someone in Vuda area who is great with Mastervolt setups?  

 

Cheers

 

 

[Black Panther 1,581]

have you eliminated the alternator itself as the problem?

[mcp 32]

Do you have or have access to a clamp meter?

[wheels 543]

Is the Regulator temperature compensated?
Mastervolt batteries, are we talking FLA? All battery types have a Temperature Window, where the extremes of such mean they do not like to accept the charge well.
Lead Acid don't accept charge well when below 10degC and they really don't like temperatures above 30degC. A good charger, which Master Volt tends to be, should have a temperature sensor and will vary the charge current in relation to the Temperature. So as the temp rises toward that 30degC, the charge current will be backed off. So it is possible all is working as it should and that the Regulator is Temperature compensated. This can be done very simply in the regulator itself, either manually by a simple setting, or a temp sensor built in, which is sometimes not the best, because the reg can often be in a different place to the batteries and not getting the same temperature, or best is with a sensor stuck to the Battery bank and sensing the actual Battery temperature. This is also great in that as the batteries are charged, they heat up and so if a Charger is large compared to the Bank, this stops the batteries being cooked.
Some chargers can have that Temp/charge rate altered by software. I don't know the Mastervolt gear well enough to know if that can be done. Because the Batteries are of reasonable size, you may be able to " trick" the regulator into giving more current by altering the Temp sensing setting. Simply tell it the temperature is actually colder than it really is. Providing you monitor the batteries and make sure they don't get too hot while charging. Or simply, leave it as it is and understand that this is working all OK.
I hope that helps mate.

[darkside 61]

My guess either high battery temp is turning off your regulator as suggested above.

Partly because you are in Fiji but mostly because the batteries are in poor condition (read old)

 

I agree with mcp get a clamp meter if you don't have one.

By far the coolest bit of electrical kit we have.

It tells you exactly what is happening now and so easy to use.

It made hunting down faults way easier especially on the cat where we had dual charging systems.

 

We had a battery collapse internally mid tasman and located the fault through the smell.

Lucky not to have it explode as it was really hot so they do fail randomly as well (not just age)

[bazzathemammoth 37]

Make sure you get a DC clamp meter. More expensive and less common than AC ones. Mine comes in really handy for fault finding.

[wheels 543]

While yes a clamp meter can be handy, I am not sure what it is going to tell Southernman, that in this situation, he does not already get to see on the display. He knows exactly what current is being produced and being absorbed by the batteries. What it is not telling him is why.
And in saying that, while yes a clamp meter can be handy, you can do just as good and even far better fault finding with a standard Volt meter. Because the Voltage at different places will tell you much more. Remember that Batteries are Voltage devices and the Current is the work required or produced by that battery at that Voltage. So for instance, if the battery is in bulk charge mode, then there will be a high current being delivered. How do you know the battery is in Bulk charge mode? The voltage will be anywhere from low up to the full bulk charging Voltage set by your charger. But the actual current will depend on what voltage point and temperature your battery is at. Acceptance charge is going to be a higher voltage but a very much lower current. Once again how do you know? it will be over 14V. Current will tell you nothing.
 

[southernman 73]

Great stuff, yip have clamp meter and have measured output and it's within .5 amp of what me amp meter on the boat says they they are charging at.  Temperature sensors are mounted on the top of the batteries.  Batteries are Gel type Mastervolts.  

 

I'm up there later this week will fault find and get back to the experts!  

[lawless auckland 1]

There is a marine electrician in the sheds by the marina at denerau who i used on lawless and found him very good and reasonable prices

[southernman 73]

Thanks guys, I suspect it's batteries really, but they load tested just fine, charge ok on the shore charger hence the doubt.  I am thinking that the temp sensors probably need investigation first which I will do to make sure I'm getting good feedback and they are attached properly.  

 

I can test this by tricking the charge regulator to accept a lower temp for a short period and see if the amps go up but the volts would indicate that at 13.6 I have an issue as I think this should be over 14V.  

 

Wait till i'm there then start the process

[Island Time 1,232]

Basics first. A voltage regulator is just that. It regulates voltage. Smart regulators are adjustable. Make certain that the smart reg is adjusted to the correct charging voltage for your particular model of battery. Read the battery product data sheet, and use the exact Max charging voltage recommended by the manufacturer. Nothing else, regardless of who told you.

In the case above, there is 0.1v difference in charging voltage. This can make a large difference in current (amps).

Remember that the regulator sets the voltage, the batteries "decide" how much current they will accept at that voltage.

Finally, be sure to read the book for your smart regulator, and follow the instructions on how to set the voltage correctly.

Only when this is done correctly should you start to concern yourself with temp sensing etc.

[Island Time 1,232]

If you cannot adjust it, it's not a smart reg, just a multi stage. In that case, especially if you use a diode splitter for multiple banks (which causes a small voltage drop), I'd replace the regulator with a real smart reg, as your batts will never be properly charged, and have a reduced life expectancy.

You may be surprised by what 0.1v does.

[wheels 543]

IT is bang on and yes 0.1V will make a huge difference. Remember it is only 0.5V between charged and flat.
Also, Revs have a HUGE affect on the output of an Alternator. Alternators area all different and are designed to produce max outputs at different RPM points. Most need to be spinning at a very high RPM to be getting max current out.
IT has made some very important points. The ONLY reason I have made a comment about temperature is the boat has gone from colder NZ temps to Warmer Fiji and the difference could be a result in less output.
Another point IT has brought up about having settings correct, make sure they are correct on the shore charger as well. It could be that it is poking out more than it should be. I think Mastervolts Batts are AGMS, so it is important that the correct setting is selected on both chargers.

[darkside 61]

From wheels post if you need high revs to get adequate output you have the wrong alternator for a sail boat.

Throw it away and get one better suited to your needs.

 

Inadequate cabling between the alternator and the battery bank can also limit charging ability.

On the cat the runs were around 10m from the port side alternator to the starboard battery bank and vice versa.

To get that to work we had damn near welding cable running across the boat.

Probably should have gone 24v but you live and learn.

 

A bit off topic but how is this for the future of power supply on a sailboat.

On board fuel cell regeneration anyone?

http://www.daedalusyachts.com/technology/

[Island Time 1,232]

A good marine alternator should put out full output at less than 1300 engine revs. Automotive ones usually need 2000 engine revs to reach Max output.

As above, big alts need big cables. And lots of cooling air. Also, any alternator over 80 Amps should have dual or serpentine belts.

[wheels 543]

Are you guys referring to cut in Voltage, or max Power output. Because unless you have a big ratio of Engine pulley to Alt pulley, you won't get full output at 1300RPM.
Most Alternators will require 3000RPM and many up to 6000RPM to generate their max output. As RPM rises, efficiency decreases. However, they will still be producing current at low RPM. All Alternators are designed with different cut in voltages and you need to ensure that the pulley ratio will spin your ALT fast enough to cut in while the engine is at idle. If it does not then you have no RPM display at idle ad it is good to have some amount of charge when at idle.
All Alternators have a current output in a curve form as shown in the graph below. As you can see, the curve becomes less as the output nears the top end and thus efficiency goes down.
A Smart Regulator will alter this output somewhat. Depending on the type of smart Reg. But in basic words, the smart reg will alter the sense voltage to ramp up the output of the Alt. But you can only go so far with that.

[darkside 61]

That is some alternator.

If I'm not reading the graphic wrong I see 22kW input power by 70% efficiency at 6000 rpm.

22x70% is 15.4kW output.

I see that is a 28v alternator which means 535 amps or thereabouts (perhaps the reason for the model number?)

I think that might be a tad bigger than most yachts use.

[Island Time 1,232]

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

 

Yep, and again, about a 1:2 ration, so the engine revs are 1/2 these...

[B00B00 310]

Great thread. I have more battery related questions but will start another thread for it to save confusion.

[Island Time 1,232]

One further thing. For FLA or AGM/Gel and VRLA, the alternator should be about 25% of the bank capacity - so say 400a/hr house bank = 100a alt. There is little point in going bigger, as the batts wont accept that current for much time at all...