Flooded "leisure" or Trojan AGM?

[BabaYaga]

So you're saying that the Dual AGM lasts 3 times longer than the Dual? But the Dual AGM costs more than 3 times the price of the Dual. Where's the advantage?

I am mainly relaying information from the manufacturer. I have zero experience of AGMs as house batteries.
As for advantages, for someone like the OP (or myself), with limited space for the battery bank, one could be that more usable Ah's would extend the time between charges (at anchor for instance). Another could be the quicker charge acceptance, as you yourself point out. Or the non existent risk of acid spillage.
Whether this outweighs the higher price...I think it might.

 

[lw395]

It's funny how so many people can assert the OP won't gain from a bigger alternator, without knowing what alternator he currently has.
It was one of the best things I did to my old boat, because the bigger alternator was a) regulated at a higher voltage and b) capable of giving the batteries whatever they wanted at tickover.

There are still a lot of alternators out there on boat engines which are not really optimised for cyclic charging on a yacht system.

 

[ibbo]

Hi Tom,
I run 2x105ah leisure batteries for the house batteries, and usually 2 x 50w panels one each side of the top of the spray hood. They are in parallell, so whichever tack you are on at least one is working. They ran the fridge all summer. (Waeco cool box, not a plate fridge.)I also have a diesel heater that gets used sometimes on an evening, and led lights.
As soon as the nights draw in it's not enough.
I have a spare 100w panel that can go out on the appropriate side for shorter days, but even with that it's not enough in winter, and only works early / late season.

Starter battery is 75ah high cranking amps one. Std alternator, but I rarely use it for charging as such.

Mike

 

[Graham376]

It's funny how so many people can assert the OP won't gain from a bigger alternator, without knowing what alternator he currently has.
It was one of the best things I did to my old boat, because the bigger alternator was a) regulated at a higher voltage and b) capable of giving the batteries whatever they wanted at tickover.

There are still a lot of alternators out there on boat engines which are not really optimised for cyclic charging on a yacht system.

I've found that just replacing a standard alternator with a larger one when changing engines, makes no difference to charge rate, the batteries still just draw what they need. If using an external regulator such as Sterling or Adverc, then a larger alternator should remain cooler but to give the batteries full charge rate at tickover, indicates a smaller pulley was fitted.

Which makes and models of alternators (without changing or adding anything) are regulated to a higher voltage and optimised for boat cyclic charging?

 

[lw395]

...

Which makes and models of alternators (without changing or adding anything) are regulated to a higher voltage and optimised for boat cyclic charging?

A lot of generator and plant engines have alternators regulated at 14V or very little more. Particularly older units or older designs. That's ideal for an engine that might have a high duty cycle and only needs to recharge the engine start battery and run a few accessories while the engine is running. Hitachi made a lot of these alternators. Some of these alternators don't chuck out much current at tickover, these applications are not much concerned with tickover.

A lot of car alternators from the (vaguely) 1995 to 2005 era are regulated at a higher voltage. 14.4V is common. These units may be made by Bosch, Hitachi or anyone else. Some of these will put out a lot of current at tickover, to cope with heated windows, heated seats, electric power steering and all that.
The Bosch I fitted to my boat (to replace a Yanmar spec Hitachi) was designed to give (something like) 120A at max rpm and 90A at tickover.

A lot of (vaguely) 2010 onwards car alternators do not simply regulate at a fixed voltage. Especially, but by no means only, stop-start cars.

It is unhelpful to tell someone that a simple alternator upgrade won't help them, unless you know a reasonable amount about their existing alternator.
Since there are almost limitless varieties of alternator, measuring what you have may be the best way forwards.

 

[pvb]

Which makes and models of alternators (without changing or adding anything) are regulated to a higher voltage and optimised for boat cyclic charging?

Many Prestolite Leece-Neville alternators have adjustable regulators, so you can set the required voltage. They also tend to have a good output curve, with decent output at lower revs.

 

[Graham376]

Many Prestolite Leece-Neville alternators have adjustable regulators, so you can set the required voltage. They also tend to have a good output curve, with decent output at lower revs.

The problem is, those who just say "fit a bigger alternator" are leading people astray in many cases as, unless they're advised to fit a different type such as the Prestolite you suggest, they won't get any benefit. In most cases, it would be cheaper to fit an external regulator/booster than change alternators.

 

[lw395]

The problem is, those who just say "fit a bigger alternator" are leading people astray in many cases as, unless they're advised to fit a different type such as the Prestolite you suggest, they won't get any benefit. In most cases, it would be cheaper to fit an external regulator/booster than change alternators.

In some cases, an external regulator may be disappointing, if the alternator is current limiting at low RPM.
It depends what you want. Some people want to run fridges or inverters at low rpm and also expect the batteries to be getting a good charge.
I think the best way forwards is to measure what you have and consider what various upgrades might do for a particular pattern of use. Rather than reciting a favourite 'solution'.