Battery isolator that isn't a switch

[seafox67]

After buying my 1989 boat two years ago, I'm finally going to try and tackle upgrading the electrics.

I have what I think is a typical starter and house battery being charged by an alternator, shore electrics charger and solar.
I have the big red 1 - 2 - both switch... however, I also a smallish black square box with two bigish positive terminals and a label saying battery isolator. This is the little thing that is confusing me at the moment! With a little help from google search, I beleive it stops the other battery from draining so I guess if you spend a night on the hook, you will only ever run flat one battery leaving the other to get you home.

Does this sound correct?

Should I connect the solar to the house or starter battery? I also wondered if it really matters as this isolator box would allow both batteries to be charged by the solar.

Thanks for any advice or pointers to a web site with an explanation

Cheers
Paul

 

[VicS]

After buying my 1989 boat two years ago, I'm finally going to try and tackle upgrading the electrics.

I have what I think is a typical starter and house battery being charged by an alternator, shore electrics charger and solar.
I have the big red 1 - 2 - both switch... however, I also a smallish black square box with two bigish positive terminals and a label saying battery isolator. This is the little thing that is confusing me at the moment! With a little help from google search, I beleive it stops the other battery from draining so I guess if you spend a night on the hook, you will only ever run flat one battery leaving the other to get you home.

Does this sound correct?

Should I connect the solar to the house or starter battery? I also wondered if it really matters as this isolator box would allow both batteries to be charged by the solar.

Thanks for any advice or pointers to a web site with an explanation

Cheers
Paul

Here we go again another thread about battery isolation switches and split charging systems !

Only the two terminals ?

A diode splitter would have two connections or the two battery positives and a similar sized terminal for the alternator input.

A VSR would have two biggish terminals for the two battery positives and a smaller negative connection.

Sounds more like the latter but you have overlooked the negative connection


A 1, 2 , both switch does not sit well with either. You are in a sort of half way position between purely manual battery selection ( which works well for some people) and a dedicated battery system with VSR ( or diode ) controlled charging

If a VSR is "bidirectional" it will respond to a charging input on either battery

 

[PCUK]

Tell us the answer please!

 

[seafox67]

Here we go again another thread about battery isolation switches and split charging systems !

Only the two terminals ?

A diode splitter would have two connections or the two battery positives and a similar sized terminal for the alternator input.

A VSR would have two biggish terminals for the two battery positives and a smaller negative connection.

Sounds more like the latter but you have overlooked the negative connection


A 1, 2 , both switch does not sit well with either. You are in a sort of half way position between purely manual battery selection ( which works well for some people) and a dedicated battery system with VSR ( or diode ) controlled charging

If a VSR is "bidirectional" it will respond to a charging input on either battery

Vics

Thank you for nudging me in the right direction. Despite the box labelled 'Battery Isolator'... a bit more searching and the information you provided. I have identified the box as a Cargo Split Charge relay.

Looking at the condition of the wiring, I think this was added later in a refit and the old 1,2,both switch was left in from when the boat was built.

I'm adding a mppt solar charger this weekend so it looks like I can just connect it to any battery. The original solar panel (looks like around 30w) which was outputting around 19v had been directly connected to the split charge relay!

Cheers
Paul

 

[VicS]

Vics

Thank you for nudging me in the right direction. Despite the box labelled 'Battery Isolator'... a bit more searching and the information you provided. I have identified the box as a Cargo Split Charge relay.

Looking at the condition of the wiring, I think this was added later in a refit and the old 1,2,both switch was left in from when the boat was built.

I'm adding a mppt solar charger this weekend so it looks like I can just connect it to any battery. The original solar panel (looks like around 30w) which was outputting around 19v had been directly connected to the split charge relay!

Cheers
Paul

If there is no distinction between the two + terminals ( not labelled main and aux for example) then I would assume that it is bi-directional, dual sensing, or what ever you want to call it which means that you can connect your solar system to either battery. The house battery would be the normal choice .

If you can identify exactly what you have ( part number, catalogue number for example) it would be wise to fully check up on it to see exactly what it is and its specification

Remember though that it is only controlling the charging. You will still need the same degree of discipline in using the 1,2, both switch to avoid running both batteries down overnight as you would without it.

 

[seafox67]

If there is no distinction between the two + terminals ( not labelled main and aux for example) then I would assume that it is bi-directional, dual sensing, or what ever you want to call it which means that you can connect your solar system to either battery. The house battery would be the normal choice .

If you can identify exactly what you have ( part number, catalogue number for example) it would be wise to fully check up on it to see exactly what it is and its specification

Remember though that it is only controlling the charging. You will still need the same degree of discipline in using the 1,2, both switch to avoid running both batteries down overnight as you would without it.

Thanks Vics... i'm starting to feel a little more comfortable with the the planned mppt install this weekend.

I take lots and lots of photos around the boat so going through them now i've identified a part number. I have a Cargo 160740 Split Charge Relay

The current solar panel has been connected to the terminal labelled Main+.

Would you advise the mppt charger should be connected to the Aux+ terminal?

Many thanks
Paul

 

[VicS]

Thanks Vics... i'm starting to feel a little more comfortable with the the planned mppt install this weekend.

I take lots and lots of photos around the boat so going through them now i've identified a part number. I have a Cargo 160740 Split Charge Relay

The current solar panel has been connected to the terminal labelled Main+.

Would you advise the mppt charger should be connected to the Aux+ terminal?

Many thanks
Paul

It seems that is not bi-directional

The main terminal should be connected to the engine battery and the aux terminal to the house battery

Any charging source connected to the main terminal, or to the engine battery, will also charge the house battery once the volts have risen to 13.4 volts regardless of which battery is selected by the 1,2,both switch and if it is set to off.

Any charging source connected to the Aux terminal, or to the house battery, will only charge the house battery, ( except of course when the 1,2 both switch is set to both.)

 

[seafox67]

It seems that is not bi-directional

The main terminal should be connected to the engine battery and the aux terminal to the house battery

Any charging source connected to the main terminal, or to the engine battery, will also charge the house battery once the volts have risen to 13.4 volts regardless of which battery is selected by the 1,2,both switch and if it is set to off.

Any charging source connected to the Aux terminal, or to the house battery, will only charge the house battery, ( except of course when the 1,2 both switch is set to both.)

Brilliant, understood and thanks for your help

Paul

 

[PaulRainbow]

Brilliant, understood and thanks for your help

Paul

I'd concur with all that Vic has said and i would connect the solar controller to the Aux terminal. This will keep the domestic bank charged and leave the engine battery to fend for itself.

It is OK to connect the controller to the VSR, if the VSR location is more convenient, provided that the VSR cabling is rated for the solar controller (which it should be). You also need a suitable fuse to protect the solar controller wiring, which should be connected as close to the battery as possible. You may already have such a fuse fitted for the protection of the VSR and its wiring, if so, it's fine to use that, if not, fit one.