Old subject, new approach.

[philip_stevens]

[pedant]I think you're thinking of the X-Split, the X-Alt is an alternator regulator.[/pedant]

One problem with any sort of diode or other splitter is that, if one "leg" fails, stopping the charge reaching one battery/bank, it's possible for a smart regulator to increase the charge voltage to an extreme level, thereby boiling the other battery/bank. I've seen this happen. The VSR route combines zero-loss with no risk of the overcharge happening, and it's cheaper too.

Quite correct - getting my X's mixed up. Had one on a previous boat along with the X-Alt.

I stand corrected

 

[Roger_D]

slave charger

I rewired so that the alternator charges the house batteries directly & a Xantrex slave charger (much cheaper I recall than a sterling B to B) charges the starter from the house when the house batteries are being charged.

A Smartguage sensing the house and starter batteries tells me voltages and state of charge of the house batteries.

The one two both switch comes off the house batteries and can engage both or just the starter battery for house or starting in emergency.

I have hidden away isolator switches for both house and starter batts, so if these are not meddled with the engine running, the one two both switch can be turned off with no damage to the alternator.

Seems to work a treat.

 

[Danny Jo]

With a VSR, the failure consequence isn't the same. It doesn't have "legs", it just links 2 batteries/banks together when the engine's running. The worst that can happen is that one battery (or bank) doesn't get charged.

I think what I have fits the description of a VSR (voltage sensing relay). It draws very little current in the off position, at which the two battery banks are separated, but links them as soon at the voltage rises above 13 decimal something volts. This state occurs when the alternator is running, the 240 volt battery charger is running, or the wind generator is producing power surplus to domestic requirement. It returns to the open/off position when the battery voltage drops below 12.5 v. This is backed up by a parallel one/two/both/off switch normally left in the off position.

So the VSR is a solution not just to the question of how to distribute alternator current, but also to that of the distribution of all sources of battery charge.

 

[LadyInBed]

As someone already noted in an old thread, swinging the engine for 30 seconds even at a couple of hundred amps only drains 1.7 Ah out of a battery,

From cold I find that 30 secs on the heater means that the starter motor only runs for 5 seconds, so the drain must be even more negligible.

 

[mattnj]

But is it one way only?

yes, one way B2B charger, about 7amps....in th OP situation could be handy to run between domestic and engine battery.

 

[Red Admiral]

Old problem - old solution

I have a separate switch in the heavy duty positive lead from each battery. The output side of the switches are joined together. Simple. Cheap. No problems. I have all batteries switched on only after engine has started and is charging.

The switches I use have removable paddle keys and their on/off positions are obvious.