What kind of Alternator on a Volvo D2-55?

[Florian68]

Hello!
I am thinking about installing an Alternator-to-Battery-charging device to reduce engine run time if I have to recharge my batteries with the engine. Looking thru the literature I realized that the charging device needs to fit the alternators charging ability, so I looked in the manual of the D2-55 that is installed on my Bavaria 38, year 2003 and found different information on the alternator, The operators manual states 14 V, 60 Amp in the chapter, the workshop manual states 14V,115 Amp! So I looked at the Volvo Engine parts and found out, that the D2-55 Version A and B were equipped with the smaller generator, while the D2-55 Versions C-F come with the bigger, 115 Amp Generator.
The question that came immediatly to my head was that I just install the bigger alternator with nearly twice the amps to charge my batteries, instead of installing an A2B-Charger! A new generator costs 139 € at SVB.de (https://www.svb.de/de/lichtmaschine-12v-115a-volvo-penta-d1-d2-d4-d6.html) in contrast to the 1120€ for an official Volvo spare part!!! (https://www.marinepartseurope.com/de/volvo-penta-explosionsdarstellung-7744440-30-6749.aspx) but can I do any harm to my engine or the electrical system if I install a generator with  higher amps?  Since all engine versions of the D2-55 have more or less the same cruising rpm it is a  beautiful idea that I could charge with higher amps.....
Is there a decal or some kind of sign on the alternator that tells me the amps with which it is charging the batteries?
Thanks for your help!

[tiger79]

Fitting a higher output alternator won't necessarily charge your batteries any quicker.  The current which a battery can accept depends on the charging voltage and the state-of-charge of the battery.  A bigger alternator won't "force" more current in unless the battery can accept it.  Larger battery banks naturally can accept larger charging currents.  If you only have 2 or 3 domestic batteries, you may not gain much by fitting a bigger alternator.

An alternator-to-battery charger can increase charging current by raising the charging voltage, but your existing alternator is probably already charging at 14.2v or thereabouts, so raising it to 14.5v, say, won't make a huge difference.

Your 60A alternator is probably driven by an ordinary V-belt.  These are good for alternators up to about 90A output.  The 115A alternator fitted to later versions of your engine has a flat multi-V belt to cope with the added power requirement.  If you fit one of these alternators, you'd really need to change the pulleys on the crankshaft and water pump to accommodate the different belt.

[Florian68]

Thanks for your answer and your remarks on the alternator; I have two 140 Ah lead acid batteries as a domestic battery bank and I just remembered that these traditional batteries should be charged with about 10 to 15% of their capacity, so the smaller  generator is just the right size, but it takes a while to charge them with the engine. A bigger generator would only make sense if I replace the batteries with AGM types, which may take a charge of up to 35% of their capacity.....
The former owner of the boat got along well with the given setup, so maybe I should just wait for the upcoming season and find out, if I can live with the given solution as well.......let hope that this f......corona virus is gone by spring.........
Thanks again for your answer

[SYJetzt]

I have a D2-75F Engine with an 115A Alternator and i have had 2x140Ah lead acid batteries in the same arrangement as you, with the similar problem (boring long time to charge the batteries with the engine). As you mentioned, these kind of batteries should only take 10% of their rated capacity to charge. So the problem is not the alternator, but the battery. If your battery-set isn't fresh anymore, the charging time until full is growing further more .
At first i would suggest to install a battery-monitor-system, which allows to see the state of charge of the battery and the in- or outgoing battery-current and the voltage as well.
With the experience, what's really happening, you are able to decide what to do.

As a long term cruiser i finally dropped the lead acid batteries and ended with 400Ah Lifepo4, but this is another (expensive) story, but i didn't touch the alternator or the charging regulator.

 

 

[Rampage]

I think that the figures quoted of 10% of capacity as a mix rate of charge are too low. I’d suggest 20-25% of capacity as a max rate (suggested here https://www.upsbatterycenter.com/blog/charging-current-use-lead-acid-battery/ amongst other places).
That said, the most that unaltered alternators will output is a fraction of their rated capacity.  I have a 90 amp alternator fitted to my 2030 feeding 500 amp hours worth of batteries and rarely see more than 40 amps being delivered to the batteries.  And that’s with a Sterling AtoB box fitted.  It’s 10-15% less without the AtoB.

[catlotion]

Sorry to drift the thread a bit but are the benefits of voltage sensing alternators over-stated?

I have a d1-20 and the Volvo literature states:

The 115A alternator with an electronic sensor makes it possible to use a higher battery capacity and have fully charged batteries on board. Even at idle speed, the alternator gives more than 35A, and at cruising speed it delivers approx.100A.

I imagine the charging rates are exaggerated but surely it does something better?  Maybe a better option for op?

[elias]

Exactly same engine and battery setup for years . 3 years ago we installed for just a test a 40w panel , helped a lot . Now 3 40watt panels and almost no need for idle run . We choose the 3 40watt cause we didn’t want to install extra unix tube arcs , and we just attached them with an aluminium one on the Bimini

[symphony2]

Sorry to drift the thread a bit but are the benefits of voltage sensing alternators over-stated?

I have a d1-20 and the Volvo literature states:

The 115A alternator with an electronic sensor makes it possible to use a higher battery capacity and have fully charged batteries on board. Even at idle speed, the alternator gives more than 35A, and at cruising speed it delivers approx.100A.

I imagine the charging rates are exaggerated but surely it does something better?  Maybe a better option for op?

As you say, overstates what you see. Just saying that it is capable of producing that amount of current at low revs and cruising (around 2200 at a guess), but as explained earlier the actual current in amps depends on what the batteries can expect. So, if you have a battery that is deeply discharged, it will take a high current initially, and fall off as charge increases. Typically though you are only charging from partially discharged, so although you may see 20+amps for few minutes after start up it will fall eairly quickly as the battery accepts less.

[catlotion]

Isn't that what the electronic sensor is for though?  I.e. much like the adverc/sterling solutions?  'Fooling' the alternator into pushing out more current for longer..?   

I'm sure I read somewhere that it has this behaviour.  Will be off the marina in march so will be doing some serious monitoring of current in and out using a smart shunt and will post my findings..

[tiger79]

Isn't that what the electronic sensor is for though?  I.e. much like the adverc/sterling solutions?  'Fooling' the alternator into pushing out more current for longer..?   

I'm sure I read somewhere that it has this behaviour.  Will be off the marina in march so will be doing some serious monitoring of current in and out using a smart shunt and will post my findings..

You can't "fool" the alternator, all you can do is increase the charging voltage.  I think the Volvo Penta alternators simply have battery-sensing and are set at around 14.4v which would be OK for most batteries.

[Lazy Pelican]

10 years ago when we bought our B39 with a D2-40 engine i spoke to Adverc regarding a smart  charger. The advice was that with a voltage sensing alternator an Adverc unnecessary. Basically they refused to sell me one!

[catlotion]

You can't "fool" the alternator, all you can do is increase the charging voltage.  I think the Volvo Penta alternators simply have battery-sensing and are set at around 14.4v which would be OK for most batteries.

I though that was how they worked?   (for the ABC devices anyway).   From the Sterling literature: 

We put a "load" on the alternator to pull the alternator voltage down. This fools the alternator into thinking that there is a major drain on the system and as such, the standard regulator works at full current. However, the voltage is pulled down to a totally useless voltage for charging batteries. So the new system takes in this high current, but low voltage, and amplifies the voltage to charge the auxiliary battery bank at a much higher voltage than the base system voltage.

As the Volvo spec talks about benefits in terms of current output I hoped (probably optimistically) that it was applying a similar approach...

Did the Adverc chap give any more detail?   I'm particularly interested as I'm working out charging needs (moving to swing mooring soon)

once again - apologies to OP for thread drift!

[Lazy Pelican]

Adverc just said that with a voltage sensing alternator I’d get no benefit from an Adverc unit. This was 10 years ago.

[tiger79]

You can't "fool" the alternator, all you can do is increase the charging voltage.  I think the Volvo Penta alternators simply have battery-sensing and are set at around 14.4v which would be OK for most batteries.

I though that was how they worked?   (for the ABC devices anyway).   From the Sterling literature: 

We put a "load" on the alternator to pull the alternator voltage down. This fools the alternator into thinking that there is a major drain on the system and as such, the standard regulator works at full current. However, the voltage is pulled down to a totally useless voltage for charging batteries. So the new system takes in this high current, but low voltage, and amplifies the voltage to charge the auxiliary battery bank at a much higher voltage than the base system voltage.

As the Volvo spec talks about benefits in terms of current output I hoped (probably optimistically) that it was applying a similar approach...

Did the Adverc chap give any more detail?   I'm particularly interested as I'm working out charging needs (moving to swing mooring soon)

once again - apologies to OP for thread drift!

The Sterling Alternator-to-Battery device is unlike any alternator system.  The VP alternator doesn't work that way, it's basically just battery-sensed to ensure a decent charging voltage is present at the batteries.

[catlotion]

Thanks everyone

[SofiaB]

Added a generator instead, to my D2-55F.  Mounts opposite the alternator which still charges the battery under power, unless I switch over to the 3PH/208V generator.  I've been seeing more and more of these introduced as an alternative to a genset.