Battery condition

[KREW2]

Wow certainly oped a can of worms here. Since I bought the boat it has always been an enigma to me, so I just follow instructions taped onto the switches and batteries.
They say to start, batt 1 to pos 1, batt 2 to pos 2
Switch #1 says port engine start, plus electric supply to instruments.
Switch #2 says starboard engine start, VHF and windlass.
They don't say 1/2/both off they say 1/1+2/2/off which I assume is the same.
There are also instructions on the battery box. In emergency turn both switches to 1+2, or maybe both to 2, I cannot quite recall.

 

[PaulRainbow]

Paul, Surely you would show the connections and wiring for the "BOTH" arrangement.

That is shown, no additional connections are needed, just the two battery connections and the common (load) connection. The both connection is made internally within the switch.

I know I am probably being picky and understand what everyone says but was really just curious as to the apparent discrepancy between the diagram and OP's description. Not going to get my underwear knotted about it

Best not

 

[PaulRainbow]

Wow certainly oped a can of worms here. Since I bought the boat it has always been an enigma to me, so I just follow instructions taped onto the switches and batteries.
They say to start, batt 1 to pos 1, batt 2 to pos 2
Switch #1 says port engine start, plus electric supply to instruments.
Switch #2 says starboard engine start, VHF and windlass.

Makes sense, given the setup, except that the schematic doesn't show the VHF and windlass coming from the Stb battery.

Out of interest, what is the boat ?

They don't say 1/2/both off they say 1/1+2/2/off which I assume is the same.

Yes, the same. 1+2 + both

There are also instructions on the battery box. In emergency turn both switches to 1+2, or maybe both to 2, I cannot quite recall.

Both switches to 1+2 connects both batteries and all loads in parallel. Works in some emergencies, bad idea for others.

For instance, if battery one failed and was very hot, you don't want to be using that. So turn switch 1 to position 2. Everything works from battery 2.

Same if battery 2 fails, move switch 2 to position 1 and everything works from battery 1.

If a battery is a bit down and struggles to start the engine just switch it to the other battery, or to 1+2, start the engine and return the switch to its normal position. Leave the windlass on battery 2, move the VHF to battery 1.

I still think it's a poor arrangement. One battery for engines, the other for domestics. A simple on/off switch for each, with a 3rd for emergency use. A VSR for split charging.

 

[lustyd]

if battery 2 fails, switch 2 to position 2 and everything works from battery 1

I may have confused myself so forgive the daft question - would that depend on which way around the switches are wired? I'm now struggling to visualise whether the 1 and 2 could be loads rather than batteries and vice versa and the system still work?

*I don't have 12B switches I have the modern battery isolation switches and a joiner, which may be why I can't visualise

 

[PaulRainbow]

I may have confused myself so forgive the daft question - would that depend on which way around the switches are wired? I'm now struggling to visualise whether the 1 and 2 could be loads rather than batteries and vice versa and the system still work?

Sorry there was a typo for switch 2, it should read : "Same if battery 2 fails, move switch 2 to position 1 and everything works from battery 1"

The switches select which battery is used. Switch 1 is for Port engine. Position 1 uses the port battery, position 2 uses the stb battery, 1+2 uses both.

*I don't have 12B switches I have the modern battery isolation switches and a joiner, which may be why I can't visualise

Me too. 1-2-B switches are a poor design on todays boats, having 2 of them is doubly complicated without any benefit.

 

[lustyd]

The switches select which battery is used. Switch 1 is for Port engine. Position 1 uses the port battery, position 2 uses the stb battery, 1+2 uses both.

**Probably thread drift**
could they be wired "backwards" though such that 1 is for port engine, 2 is for stbd engine etc and each switch is for one battery rather than one load? I'm not suggesting they are here, just trying to get my head around the switches

 

[PaulRainbow]

**Probably thread drift**
could they be wired "backwards" though such that 1 is for port engine, 2 is for stbd engine etc and each switch is for one battery rather than one load?

Technically, yes, they are just changeover switches. The common could go to battery X, with an engine to positions 1 and 2. The switch then determines which engine is started from battery X.

I'm not suggesting they are here, just trying to get my head around the switches

They aren't. In this case (which is typical), the common connection goes to an engine, terminals 1 and 2 are connected to different batteries, so the switch selects which battery starts that particular engine.

So, the port switch (1) is for the port engine. It can be started from the port battery (position 1) or the stb battery (position 2) or both batteries in parallel (position 1+2).

The Stb switch (2) is for the Stb engine. Position 2 uses the STB battery, position 1 uses the port battery, 1+2 uses both in parallel.

Can't beat a couple of on/off switches, can you

 

[lustyd]

Thanks Paul, very useful

 

[KREW2]

Thanks Paul, I'm trying to make some sense of it, glad it confuses others as well. The boat is a Seaward 25, as you may gather not the sailing variety.
The schematic is from the initial build and things that come as standard. Radar, plotters, windlasses, fridges and radios are all customised extras specified by the owner.
What I really want to know is with the VHF and the windlass isolated will there be any drain on battery 2 if left switched on?

 

[PaulRainbow]

Thanks Paul, I'm trying to make some sense of it, glad it confuses others as well. The boat is a Seaward 25, as you may gather not the sailing variety.
The schematic is from the initial build and things that come as standard. Radar, plotters, windlasses, fridges and radios are all customised extras specified by the owner.
What I really want to know is with the VHF and the windlass isolated will there be any drain on battery 2 if left switched on?

Impossible answer that with any certainty as the schematic is obviously not fully up to date. Only way to be sure is to check with an ammeter.

 

[pmagowan]

The typical configuration (one that is not shown in your schematic) is that coming from the house battery (you are using one of your engine start batteries as 'house') you would have an un-switched loads bus bar and then a switched loads panel. The un-switched loads are for things you never want to have turned off (which would otherwise be wired directly to the battery causing a mess) such as automatic bilge pumps, monitors, charging etc. The panel can have a main switch to turn the whole thing off and then individual switches for each load. With the main switch off then the only potential drain are things on the un-switched side. Your whole schematic is not visible but it appears that there are a few wires going from the engine which will connect to the battery through the 1/2/b switches, none of which have an obvious individual switch. One goes to a panel which may have fuses or circuit breakers of some kind. 2 more disappear off the page. You will need to look at the battery and trace the wires.

PS: I would change the whole setup, but I like to understand how things are working.

PPS. technically you can use any battery for starting and for house but whatever you use for starting the port engine will be your house as it is all wired through the engine in the schematic. This may not reflect reality and is confusing in any event.