Charging Question - is a battery to battery charger the right way forward?

[pvb]

Ah, OK, this sounds a plan. I had found such a unit from Sterling with 2 outputs, not 3, but using the isolator to further split the charge between the engine and bow thruster would make sense.

Sterling kit the best way to go?

I think Sterling are the only people to make A-to-B chargers at the moment. With your 400Ah or so of batteries, you're not likely to see a charging current much higher than 50-60A for very long, even with the A-to-B charger, so I'm not entirely persuaded by PaulRainbow's warning of overheating. What the A-to-B charger will do is help with getting the last 15% or so into the batteries; it also gives a proper multi-stage charge regime (including a float voltage) so your house batteries will be better treated than before.

If you find that your Hitachi alternator isn't up to it, there's no need to pay Balmar money for a better alternator - you should be able to get a 90A Prestolite Leece-Neville alternator for around £100. These are good alternators with a high output at lower revs, ideal for boat us (indeed they make the alternators which Balmar sell). Don't be tempted to try to fit a large-case higher output alternator, getting the bracketry right to resist vibration is tricky, and you don't need any more output than 90A.

 

[West Coast]

I think Sterling are the only people to make A-to-B chargers at the moment. With your 400Ah or so of batteries, you're not likely to see a charging current much higher than 50-60A for very long, even with the A-to-B charger, so I'm not entirely persuaded by PaulRainbow's warning of overheating. What the A-to-B charger will do is help with getting the last 15% or so into the batteries; it also gives a proper multi-stage charge regime (including a float voltage) so your house batteries will be better treated than before.

If you find that your Hitachi alternator isn't up to it, there's no need to pay Balmar money for a better alternator - you should be able to get a 90A Prestolite Leece-Neville alternator for around £100. These are good alternators with a high output at lower revs, ideal for boat us (indeed they make the alternators which Balmar sell). Don't be tempted to try to fit a large-case higher output alternator, getting the bracketry right to resist vibration is tricky, and you don't need any more output than 90A.

Thanks, you had given me advice re the prestolite alternators earlier as I was beginning to think about this project. Certainly, there mixed reports regarding the hitachi alternators.

 

[PaulRainbow]

Those Hitachi alternators will reduce voltage for every degree above 20c. Your typical engine compartment will be much warmer than that, force the alternator to increase output and you're wasting your time. It's a well known issue with these alternators.

Doesn't have to be a Balmar replacement, that was just an example.

Solar is still the best answer

 

[dunedin]

Solar is on the agenda, but initial focus is making best efficient use of the engine.

For a sailing boat using anchor, personally would tend to start with
(A) lowering consumption (eg all LED lights, for cabin and navigation) then
(B) adding solar (which is very effective these days),
before spending more on engine charging

 

[lw395]

For a sailing boat using anchor, personally would tend to start with
(A) lowering consumption (eg all LED lights, for cabin and navigation) then
(B) adding solar (which is very effective these days),
before spending more on engine charging

Exactly.
The OP seems to be using 20% of 4 x 110Ah. That's 88Ah overnight?
A bit of casual motoring on a sailing boat isn't going to replenish that.
It needs about 4 hours of solid charging.
Given good sailing weather or no desparate need to motor from A to B, I'm not going to be motoring 4 hrs every day on a cruise.

 

[West Coast]

Exactly.
The OP seems to be using 20% of 4 x 110Ah. That's 88Ah overnight?
A bit of casual motoring on a sailing boat isn't going to replenish that.
It needs about 4 hours of solid charging.
Given good sailing weather or no desparate need to motor from A to B, I'm not going to be motoring 4 hrs every day on a cruise.

Really 88 Ah over 24 hours - with plotter, instruments, etc during the day, fridge 24 hours and heating when needed. My wife really feels the cold (previous threads!!) so heating is used a lot. I have minimised power consumption wherever I can, all is LED for example.