battery set up- whats best?

[Mike k]

I would be very interested hear the panels advice on how best to select and set up my batteries on my system.

To explain the pictures there are 2 batteries and the red cable from each goes into a single BEP 701 master switch, after that there are 2 more BEP 701 switches - from them one red lead goes to the starter motor and the other to the mains panel. The earth strap goes from one battery to the next then onto the engine earth.

My first question is how can I tell if the two red leads that go into the master switch effectively joins the two supplies- i.e does the BEP 701 join them or keep them separate?. 2nd what's the point of the two following switches- surely there is no point just having either one or the other ''on'' when you need to have starting and services supplies? 3) What does the black unit below the 2 BEPS actually do?.

Finally if the two systems are connected in the switch- is there any point having different types of batteries ( starter and leisure) ...any advice on the best combination?

 

[rafiki_]

A bit more info about your boat, and how you use her would be helpful.

 

[spannerman]

The black box is a split charge relay, which allows the alternator to charge the start and service batteries separately which is the recommended set up.
From your description you have a battery switch for each system, the 3rd switch with two red leads is a crossover switch, in the event you drain your start battery you can turn this switch to connect the start and service batteries together so you can use the service battery in an emergency to start the engine. Normally you run with this switch off so the two systems run and are charged separately. Very typical setup, I have installed this setup in dozens of boats and have it in my own, but with a simpler 1/2/both selector switch.

 

[Mike k]

hi its a 250hp 24feet weekender, I use her mainly for 2 hour cruises or 8 hour fishing trips at anchor.

 

[Mike k]

The black box is a split charge relay, which allows the alternator to charge the start and service batteries separately which is the recommended set up.
From your description you have a battery switch for each system, the 3rd switch with two red leads is a crossover switch, in the event you drain your start battery you can turn this switch to connect the start and service batteries together so you can use the service battery in an emergency to start the engine. Normally you run with this switch off so the two systems run and are charged separately. Very typical setup, I have installed this setup in dozens of boats and have it in my own, but with a simpler 1/2/both selector switch.

that's interesting thanks very much but just for clarity the first switch ( on far left) is the one that both battery positives go into direct from the batteries- so does this not just activate the whole system as a master switch as it precedes the next 2? I,e if this is off will the other two switches on the right still work and what is the point of them? many thanks

 

[5teve]

The black box is a split charge relay, which allows the alternator to charge the start and service batteries separately which is the recommended set up.
From your description you have a battery switch for each system, the 3rd switch with two red leads is a crossover switch, in the event you drain your start battery you can turn this switch to connect the start and service batteries together so you can use the service battery in an emergency to start the engine. Normally you run with this switch off so the two systems run and are charged separately. Very typical setup, I have installed this setup in dozens of boats and have it in my own, but with a simpler 1/2/both selector switch.

When using a split charge relay or vsr or other black box to charge the batterys together without being together - I use the blue sea dual circuit switch which have off / on and combine https://www.bluesea.com/products/5511e/e-Series_Dual_Circuit_Plus_Battery_Switch - therefore no switching from one bank to the other (which you shouldn't need to with the split charge device)

Saying that what is shown here seems reasonable.. and is how the new boat we are looking at is configured... but as the electrics are a bit dodgy (am I am fastidious about good electrics on a boat) i'll probably change things

Steve

 

[spannerman]

The switch with a red cable either side isn't a master switch it just allows you to transfer power from which ever battery has the most charge to the other one. The other two, one to engine and one to main panel are your master switches.

Just to clarify I have a 1/2/both battery switch similar to 5teve with no split charger, my charge output goes to the common terminal of the switch and then feeds to which ever battery is selected. I always set it to both for starting so all 3 of my batteries get to do some work and all 3 then get charged while running, I select 2 when I stop as this is my 2 service batteries to power the music and fridge, loo etc while at anchor, then back to both for the run home, this way 1 (start) is never drained and will always get me home if we use up the service batteries, this has worked perfectly for the past 20 yrs in both my boats which had identical set ups.

 

[Mike k]

The switch with a red cable either side isn't a master switch it just allows you to transfer power from which ever battery has the most charge to the other one. The other two, one to engine and one to main panel are your master switches.

Just to clarify I have a 1/2/both battery switch similar to 5teve with no split charger, my charge output goes to the common terminal of the switch and then feeds to which ever battery is selected. I always set it to both for starting so all 3 of my batteries get to do some work and all 3 then get charged while running, I select 2 when I stop as this is my 2 service batteries to power the music and fridge, loo etc while at anchor, then back to both for the run home, this way 1 (start) is never drained and will always get me home if we use up the service batteries, this has worked perfectly for the past 20 yrs in both my boats which had identical set ups.

Brilliant explanation I have got it now. Just one final question , with my system will it charge both batteries even if the crossover switch is set to off ( presumably the starter only setting) ? Many thanks indeed. Best wishes

Mike

 

[spannerman]

Yes as you have a split charger ( black box with 3 terminals under the switches), and this has a cable coming in from the alternator, then it has two supplies out to your two battery banks, start and service, so these will all get charged even if you have turned off the service switch while running, which is unlikely as you won't have lights, plotter, trim tabs etc.

 

[Mike k]

Yes as you have a split charger ( black box with 3 terminals under the switches), and this has a cable coming in from the alternator, then it has two supplies out to your two battery banks, start and service, so these will all get charged even if you have turned off the service switch while running, which is unlikely as you won't have lights, plotter, trim tabs etc.

many thanks,much appreciated

Mike

 

[Sailorsam101]

I wish mine were that simple...

So far i've got..two isolators outside in the cockpit that only turn off power to the port engine.

A DC master switch inside that turns everything off apart from the bilge pump and heater...which can't ever be turned off..!!!!

Three batteries....2 are for the port engine and power all domestics..but cannot be separated. The other is for the stbd engine only for starting and nothing else.

I think i'm going to rip it out and start again and keep it simple.