Alternator Charging problems

Hello,

I have a swan 38 with a Nanni 4.150 35hp engine and an 70 amps Prestolite alternator with a mastervolt alfa regulator (3 phase loading).

I use that to charge 330 Ah domestic batteries and a separate 110 Ah starter batterie with diode block in between.

When 150-200 Ah has been used I start loading. The maximum loading is about 40-45 amps for a very short time, then it rapidly goes down to 30-35 amp. it takes about 5 hours to load and the last 40 Ah is almost impossible.

The wiring is original and the batteries are of maintenance free type.

In my opinion 70 amps alternator should be enough and I cannot understand why it is charging so little ? Perhaps the temperature in the engine box is too high ?

 Does anyone has any experience or thought on this matter ?

Best regards,

Jan Kooistra

Swan38/110

Yulunga

Jan

Check that you have the correct split diode fitted, their are two types. It makes a difference to the charge voltage. When I change mine the charge voltage went from 13.5 to 14.2. The when I added an ADVERC battery regualtor the voltage went up to 14.5 at peak charging.     

Dear John,

Thanks very much for your suggestion.

I measure the voltage and amperes on a shunt. The voltage is ok and more than 14.2 volt when the batteries are loaded. For that matter I also have the mastervolt regulator with which I can regulate to compensate for the drop in voltage from the diode splitter.

I think the problem is in the alternator and not in the regulator or the diode splitter. The amps are too low in my opinion considering that it is a 60 amp alternator and nearly empty batteries.

Jan

Jan,

I have 3 X 80 AGM for domestic and 1 x 100 for engine start. Also a 70 amp alternator with ADVERC. regulator.

I used the wrong type of split diode for 9 years before somebody telling me it was the wrong type.  I am not a technical person but I belive one type is machine (alternator) controlled  the other battery controlled.  It made a big difference to my charging regime.  When your regualtor was fitted did they make the wiring changes to the alterntor? Again I am told sometimes electricians forget this.  Has the alternator been changed since the regulator was fitted?

If the batteries have been discharged below 60% then I understand they will be problematic in recharging to full capacity.   

Sorry I can't be of more help

John,
My alternator is 1 year old and was rewired for this type of regulator.
Everything works fine, that is the voltage is ok and corrected for the diode splitter.

When the batteries are reloaded with the batterie charger after being almost empty there is no problem. So there is not a problem with the batteries.

Can you tell me how much amps your alternator is and how many amps are loaded when the batteries are half empty ?

jan

Jan, the alternator is 70 amps.

I never allow the batteries to go below 80% of the total capacity without charging. I look over the weekend at amps being charged.

At what engine revs are you charging?    

John,
Does your alternator charge at maximum rate if the batteries are still 80% full ?
My strategy on trips that last a couple of days is to wait for loading until the batteries are more empty so that the charge current will be maximum. At least that is what I think is best to optimize loading time and engine running to a minimum. Otherwise I will have to run the engine every five or six hours (when autopilot is on).
Engine revs on maximum loading are about 1300 revs.
Jan

Jan, the regulator allows cycle charging at 14.5 volts for 10 minutes and then down to 13.5 volts and then back up to 14.5 volts. This goes  on until I get back to where I want to be. The charging cycle process does not appear to be effected by the capacity level of the battery. That is how my specific regulator works. I will let you know what my amps are when charging at both voltages after the weekend.

You should never allow batteries to go below 60% of their capacity, or you will damage them. By damage I mean accepting and holding the charge.  How low do you go in terms of capacity? Below 60%? 

My revs for charging only are also approx 1300. My optimium cruising revs are 1800 interms of speed / distance per litre.

Friends,
I must add a point about alternator ratings well explained, for example, in the extremely useful book by Nigel Calder: Boatowner´s Mechanical and Electrical Manual.
To be short: an alternator rated 70A will probably not be able to deliver more than 75% of this amount to the batteries.
Given a 300Ah house bank, a 70A alternator is fine with a traditional charge regulator while a modern smart charger needs a more powerful alternator (probably by 150%).

Daniel, 411/004

Hello eveyone, this is definitely a hot topic: electricity on board!

First I have a question for Jan: how do you know you have been using 200 Ah? Is this through voltage or measuring with a mastervolt/electronic system?

In any case this is far too much, I would say you shoud never go below 100AH before charging, and this should take you through 24 hours cruising with fridge and autopilot.

On 41/022 we have installed a full mastervolt charging equipment (alternator, regulator, measuring system) with the same battery bank as Jan, and when we start charging we get 60 Amps at 14,3V or so (measured at the batteries) which is a lot and means large wires.  We kept the original Nautor wires, and they get very hot!

Jan are you sure your batteries are OK?

Is your regulator really taking the voltage reference on the domestic bank?

Is the wire between regulator and batteries large enough?

Hope this helps. Kind regards. Philippe Vidal.

Hello Philippe,

I measure my Ah through a mastervolt batmonitor.

According to my battery dealer these baterries may be discharged to 40%. And I have never discharged them more then about 150-170 ah.

Anyway the batteries are still ok. They have been checked.

And when I am sailing 24 hours on autopilot I use between 7 (daytime) and 12 amps (at night) per hour in total.

I am very interested to know what sort of autopilot you use ? I have a robertson/simrad ap22 with a whitlock drive. And it varies depending on the weather but I my reference is 25-35 knots wind from astern (a recent trip to Norway from Holland).

Furthermore I would like to know what alternator and regulator you have installed and on what engine ?

What do you mean with the wire between the regulator and the batteries ? In my case the regulator has wires to the alternator and the alternator has wires (original) to the batteries ?

Sorry. A lot of questions. But as you said it is a hot topic.

And I was interested to hear from other Swan owners because of the rather small engine box in a lot of swans and the effect that could have on the temperature.

Kind regards,

Jan

Hello Daniel,

Thanks very much for the book title.

I have a modern charge regulator (mastervolt). Do you suggest an alternator of about 90-100 amps ?

Best regards,

Jan

Hi Jan,
after browsing the technical literature for a while I can tell you my choice when I will upgrade my charging system with a smart regulator: a good marine 100-120A alternator with twin pulleys and new cables. I must confess that, to date, I kept this expensive job at a lower priority with respect to other expensive boat works. In particular I solved part of the charging problem with a wind generator.

Daniel, 411/004

Hello Jan,

Our equipment is the following:

Autopilot is NKE with hydraulic actuator. It draws aroud 5 amps when working. The overall consumption depends of course on how long it operates. I understand you refer to a rather "busy" situation...

Engine: perkins 4108

Meter: Mastervolt Battery monitor, with the shunt just next to the domestic batteries. (measure on the engine battery only through original Nautor system)

Alternator: Mastervolt 12V, 90 Amps (and not 75 as stated before)

Regulator: Mastervolt Alpha regulator. The wire I was referring to is the voltage sensing wire. Reading back the instructions I noticed there are two possibilities. First is using a red wire and connecting it to the alternator. Second is using a brown wire (and changing a jumper in the regulator) and connecting it directly to the battery bank. This allows to compensate for any voltage drop in the system, including the diodes, and cabling resistance. It has to be done through a relay (it's fairly well explained in the instructions). We went for the second solution, and of course the engine battery gets what it gets. It seems incredibly happy with it!

Charging starts with 60 amps going to the domestic bank, 14,3 volts.

Hope this helps.

Kind regards. Philippe.

Jan and others.

I have attached two pieces of information which you may find interesting. I spoke to ADVERC who provided the attachments. The message from them is count your domestic battary bank only when sizing the alternator and use a ratio of 1-3. So your alternator should be larger. So should mine!

You must have the alternator working effecently i.e. at the correct revs which as we know is also a function of pulley size and engine speed. I need to do some checking on my alternator suppliers web site.   

Because I never let my batteries run as low as you, I found that over the weekend at 14.5 volts I was putting in only 5.6-8 amps with my batteries at 87% charged.  ADVERC told me not to use % but voltage as per the charge list with 12.2 volts being 50% charged. 

Hope this helps

John

Dear all

Thank you all for your input.

This topic seems to have many interest.

My conclusion so far must be:

- my power comsumption is, given the circumstances, acceptable

- no one reported any problems with the cooling of the alternator in the engine box

- my alternator should be around 100 amps (1/3 of the service batteries)

- the effective load of the alternator is 75% (when batteries are 50% discharged)

- I need bigger wiring with the bigger alternator

- I need a temperature sensor

- traction type batteries live longer when making longer passages

Any other input is welcome !

Thanks again !

Jan

Yulunga 38/110

Jan, three other points to think about:

A 100 Amps alternator will most probably need a pair of belts: do you have enough space to fit them, and will your engine accept such a new pulley?

Check that your splitting diodes will accept 100Amps

Install the voltage sensing on the domestic battery bank, not on the alternator

And also, use as many lighting diodes as possible, including in the navigation lights...

Kind regards.

Philippe

Jan

Would suggest that you first attempt to get the charging system to use the full output of your present alternator, and then check how long the full output is used before the system begins to reduce the charging current. It is the full output time that would be reduced by installing a bigger alternator.

Lars

Lars,

Do you mean bigger service battery capacity and bigger wires ?

And do you mean that a bigger alternator only puts in more amps in less time before the charge current will be reduced because the "system" (capacity) is the same ? And therefore the total loading time will not be affected ?

Jan

Jan

Suggest you first install bigger wires to see how this affects the charging. Then check the system and its settings, you should get the alternator to work near full output when charging begins. Then you can consider, based on the time spent at full output, if it is worthwhile to attempt to reduce this time by installing a bigger alternator.

Lars