Swapping a 1,2,both switch to a split charge relay..

[floatsyourboat]

you already have a 'split' system in that you have two alternators charging separate banks (by the sound of it). so is what you actually want to do is 'parallel' your alternators so your domestics make use of the usually under utilised starter alternator as well ?- in which case your relay will do that - see post #12 in the thread bottle linked to.

 

Yes that is what I mean thanks I will have a read.

[floatsyourboat]

I'm confused, how does the starter battery get charged if everything is going to the domestic bank?

[Tony Brooks]

I'm confused, how does the starter battery get charged if everything is going to the domestic bank?

 

The poster does not mean charge splitting, they mean alternator/battery bank paralleling and as long a sits not done with some fancy electronic gizmo everything will not go to the domestic bank unless the domestic bank is shorting out big time.

 

The amount of charge going to one particular bank will be proportional to the difference between battery voltage and charging voltage. The domestic ban will normally be more discharged than the engine battery but its voltage will normally be high enough to ensure the charging voltage is higher than the well charged engine battery voltage (see other topics as to why the engine battery spends most of its time all but fully charged). This means that the charge will apportion itself between the two batteries depending upon their relative states of charge. Unless something is very wrong the engine battery will always receive some degree of charge. This low rate of charge is the excuse some manufacturers/vendors use to sell gizmos that prioritise the engine battery at the start of charging but experience from probably thousands of boats with straight forward slit charge relays show that the engine battery is charged perfectly well. You will also see claims from some voltage sensitive relay vendors that the relay prioritises the one battery bank but while true in extreme cases where when the bank the alternator is connected to is exceptionally well discharged their claim is no more than relying upon the fact that a well discharge battery will suppress the charging voltage and if it is suppressed to below the relay closing current so it can not parallel the batteries. If they claim it prioritises the engine battery they are admitting their wiring scheme is just asking for relay problems caused by overloading at some point in the future (alternator output wired to the engine battery rather than the domestic bank - see other topics as to why).

 

In my view there is far too much spin and misdirection in the enhanced charging industry.

Edited October 31, 2014 by Tony Brooks

[Robbo]

I'm confused, how does the starter battery get charged if everything is going to the domestic bank?

Relay

[jonathanA]

I'm confused, how does the starter battery get charged if everything is going to the domestic bank?

Ok let's go back to basics

 

What is the problem you think you have / are trying to solve ?