The next step is where I would like to hear your feed back and experiences please.
ie. Using the standard VP 115A alternator (D1-30F)
1- is the inbuilt electronic regulator good enough to charge my house batteries correctly?
ie. to return the batteries to full SOC - without excessive running of the engine
2- would you suggest an external regulator be better or smart charge A2B?
ie with bulk charge, float and equalisation charging profiles
3- I haven't decided on which type of house batteries to install at yet - Wet cell, AGM or ?
This very much depends on the above 1&2.
4- The spec for the VP 115A alternator is vague and says 14v, surly at 14v this will never fully recharge the battery or take extra engine running hours to return the battery back to somewhere near full charge.
Until I get the boat back in the water I cant actual test what voltage the alternator pumps out.
Smart Chargers,
I understand the principals of how they work, but aren't they stressing the alternator or battery by forcing the higher charge rates to reduce charging times?
I am using some basic battery principals.
Don't drain below 50% SOC
Size battery bank so that you only use a small portion of the total installed Ahr say somewhere around 30%
Battery acceptance charge is around 25% of the total installed Ahr (ie 100Ahr battery will only bulk charge @ 25amps max)
The very first thing to do is measure accurately the max voltage produced by the new alternator. With fully-charged batteries, see what voltage the alternator is producing - this will tell you what the standard regulator is set at.
Next, decide on the type of batteries you're going to use. I favour AGM batteries, because they're very clean, have a low self-discharge rate, and they have a high charge acceptance rate (which helps to maximise effectiveness of alternator charging).
Your plan to have around 450Ah of domestic battery capacity is sound - the most cost-effective improvement you can make to a boat's electrical system is to add battery capacity. The bigger the battery bank, the easier it will absorb the available charge, and the lower the depth of discharge for a given usage. If you choose AGM batteries, they should be able to absorb the max output of your alternator. If you choose wet flooded batteries, they may not be able to accept the max output, so you may need more than 450Ah. In my last boat, I had 660Ah of maintenance-free batteries as the domestic bank, with a 90A alternator, and rarely saw much more than 60A charging.
Rather than trying to get your batteries up to 100% SOC with the engine, you should find that running them no lower than 50% and then recharging to 80-90% is more effective.
Remember that the current output from your alternator is speed dependent; typically, the max output of 115A will be delivered at around 5000rpm alternator speed, which equates to about 3100rpm engine speed. If you're running the engine more slowly, say cruising at 2000rpm, the alternator typically won't be able to deliver more than perhaps 75A. Adding a "smart" regulator or an A-to-B charger won't change this basic truth.
You asked about "smart" regulators stressing the alternator or the batteries. Better systems will usually have temperature sensors on the alternator and battery, so will adapt accordingly. But you can't force charge current into a battery, it will only accept what it wants to, based on the charge voltage, the SOC and the battery's internal resistance. Similarly, you can't force an alternator to produce more charge current that it's rated for at a particular speed.
If you choose to have AGM batteries, the max charge voltage is usually given as 14.4v, so if your standard alternator is delivering close to that, there'll be very little benefit from fitting a "smart" regulator or an A-to-B charger. If you choose to have wet flooded batteries, they can be charged at 14.8v, and in this situation a "smart" regulator or A-to-B charger would help to achieve the 14.8v.
As you have a new engine, it's perhaps worth noting that an A-to-B charger doesn't involve alternator modifications which may otherwise void the VP warranty, so if you need an enhanced voltage, the A-to-B could be the better choice.
