Author Topic: Larger alternator or dual alternator? Bavaria 38 2002 - Volvo Penta D2-55A  (Read 118 times)

Seagoon

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I have a 500Ah AGM house battery bank and am looking at doing some longer passages and remote cruising. I have some solar and wind charging installed but I still have the stock Valeo 60-amp alternator installed.

I have been thinking of a larger alternator such as the Volvo 115A offering or a Balmar, and/or a dual alternator installation to more efficiently charge this bank.

Volvo seem to only do dual 60A kits for the D2-55A, with single or dual 115A kits only for later models - see https://www.volvopentashop.com/epc/en-US/Details/AccessoriesCatalog/2784?path=1532%2F2783%2F2784

Has anyone worked out why the Volvo dual 115A is not for the D2-55A?

Has anyone had success with higher output single or dual alternator installations on D2-55As?

tiger79

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Has anyone worked out why the Volvo dual 115A is not for the D2-55A?


I think the D2-55A uses an ordinary V-belt to drive the alternator, whereas later versions of the engine have a multi ribbed poly-V belt, which is necessary to drive the larger output alternator.  With an ordinary V-belt, around 90A is the maximum 12v alternator which can be reliably driven - larger than that and there's excessive belt wear.

If you change the pulleys, you could no doubt fit a 115A alternator to your engine.

IslandAlchemy

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Neither.  Fit a Sterling Alternator to Battery charger (AtoB).

It will give you far more charge than a bigger alternator.

I had (until recently) a Valeo 60A alternator on a VP engine and 675Ah of house batteries, and it worked perfectly.

tiger79

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Neither.  Fit a Sterling Alternator to Battery charger (AtoB).

It will give you far more charge than a bigger alternator.


Well, an A-to-B charger will help to maximise the charge rate by increasing the charge voltage at the batteries, but it can't magically create any more charge than the alternator is capable of producing.  A typical 60A alternator, with the engine running at cruising revs, might be able to produce 40-50A.

IslandAlchemy

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An alternator on its own will not produce 40-50A for 2 hours.  It will produce it for about 20 minutes, and then reduce down to a fraction of that.  The Sterling unit basically makes the alternator pump the full output into the batteries until they are full (taking a breather every 15 minutes to let the batteries cool and settle down).

It works.

sy_Anniina

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If you have or can borrow a clamp ammeter capable of DC-measurement, I would suggest you to measure the true charging current you get from the current alternator. I suspect IslandAlchemy is correct here, but measuring your own alternator output you can be sure.

Based on findings of collagues, my guesswork is your current alternator does supply about 30A to your 500Ah battery bank after short initial rush close to 60A.

Changing to bigger alternator only (with identical charge controller) will still produce the same steady-state 30A current, just the initial rush will be bigger.

If increase 30->60A is enough Sterling AtoB or other regulator (like Sterling Pro RegDW) is enough

If more is needed, you need to upgrade both the alternator and the regulator.

BR,

Tommi
s/y Anniina

tiger79

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An alternator on its own will not produce 40-50A for 2 hours.  It will produce it for about 20 minutes, and then reduce down to a fraction of that.  The Sterling unit basically makes the alternator pump the full output into the batteries until they are full (taking a breather every 15 minutes to let the batteries cool and settle down).


No, the A-to-B charger only increases the charging voltage at the batteries (to 14.4v in the case of the OP's AGM batteries).  If this is higher than the alternator's output voltage, the charging current will be greater, but the actual current will depend on the ability of the batteries to absorb that current.

IslandAlchemy

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From the Sterling literature....

ProAlt AtoB optimises the available output of the alternator (that varies with engine speed) and converts the output to mimic that of a mains powered multi stage battery charger.

How it works

In order to maximise the alternator output current, the alternator-to-battery charger pulls the alternator output voltage down to about 13V. Then this low voltage is amplified to a higher voltage suitable for effective battery charging, i.e. 14.1V to 14.8V.
The unit’s intelligent software automatically calculates the optimum charge in any cycle and absorption time. When the batteries have been fully charged, the voltage is reduced to float voltage (appr. 13.5V to 13.8V).

It is designed to pull this voltage down a little in order to enable the standard alternator regulator to produce its full current.

tiger79

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Don't necessarily believe the Sterling hype.  The A-to-B charger is a clever bit of kit, but it can't generate any more electricity than the alternator can generate, at any given engine speed.  Alternators generally achieve their rated output at 6000-7000rpm, depending on pulley sizes this could be 3000ish engine rpm. 

The A-to-B charger achieves better charging purely by increasing the charge voltage at the batteries to an optimum level (the same thing can be achieved by adding a "smart regulator" but that requires some alternator modification whereas the A-to-B charger needs no alternator modification and hence preserves warranty).

One thing the A-to-B charger does do is allow the charge voltage to drop to a float level, which is something that add-on regulators don't do.

IslandAlchemy

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I don't believe the hype.  I have one and believe what I see happening.

When I got it, the people at the boatyard said "it's just a box with flashing lights and won't help you.  What you need is a bigger alternator".

Well, I fitted it, and it took my batteries from 12.2v to float in 2 hours every day for 10 days during the second half of a transat from the Azores to the UK, where before we were having to run the engine for 6-8hrs/day just to get the batteries to break-even.

tiger79

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I don't believe the hype.  I have one and believe what I see happening.

If you had an add-on smart regulator you'd see a similar effect, it's simply a case of getting the charge voltage correct at the batteries.

tiger79

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Well, I fitted it, and it took my batteries from 12.2v to float in 2 hours every day for 10 days during the second half of a transat from the Azores to the UK, where before we were having to run the engine for 6-8hrs/day just to get the batteries to break-even.

12.2v is generally considered to be 60% state of charge.  To fully charge your 675Ah of batteries would therefore need at least 270Ah (40% x 675).  Your 60A alternator simply can't supply that in 2 hours.