Instruments turn off when starting engine having added extra battery,

[bedouin]

I'm trying to keep it simple, and not making the same mistake as you by overestimating........

Unfortunately as this thread has shown there seems to be no way to simplify it sufficiently for the average forum users to understand

 

[PaulRainbow]

Unfortunately as this thread has shown there seems to be no way to simplify it sufficiently for the average forum users to understand

How arrogant !!

You're so well versed in electrics you can't start your own engine without affecting the plotter

 

[bedouin]

How arrogant !!

You're so well versed in electrics you can't start your own engine without affecting the plotter

QED. Pretty much everyone now realises you are wrong - however much we (now not just me but several others too) try to explain you don't get it and so you resort to insults. Behaviour most people grow out of by the time they get to secondary school. Perhaps if you were a little more open minded and realised that you don't in fact know it all you might learn something yourself.

Are you yet prepared to admit that what I said in my original post was 100% correct?

 

[Sandy]

QED. Pretty much everyone now realises you are wrong - however much we (now not just me but several others too) try to explain you don't get it and so you resort to insults. Behaviour most people grow out of by the time they get to secondary school. Perhaps if you were a little more open minded and realised that you don't in fact know it all you might learn something yourself.

Are you yet prepared to admit that what I said in my original post was 100% correct?

If this was a serious issue why do those who have a common negative, and I suspect the majority of boats are set up like this, are not suffering this every time we start the engine?

From what the OP has posted he has changed something in his set up, only after that is he reporting a problem.

This old cynical engineer thinks that the OP has accidentally changed something.

 

[bedouin]

If this was a serious issue why do those who have a common negative, and I suspect the majority of boats are set up like this, are not suffering this every time we start the engine?

From what the OP has posted he has changed something in his set up, only after that is he reporting a problem.

This old cynical engineer thinks that the OP has accidentally changed something.

Not that long ago (well last century but who is counting) 1-both-2 switches were pretty common and with that you have to accept everything cutting out when you start the engine.

With the increase in demand on the domestic side (fridges etc) it became more common to have genuine 2 battery set ups with separate switches and presumably these include separate -ve from the start - it would be silly not to if you understand electrics and it only costs one extra wire.

So it is only likely to be an issue in boats like mine that were built with 1-both-2 but later had a second switch added to split the circuits. It would only take an extra length of wire for me to remove the common element but it really isn't an issue. While the GPS moans about the voltage it doesn't reset and even if it did being without GPS for a couple of seconds while I start the engine really doesn't bother me. I can use DR to project my position forwards for those couple of seconds.

 

[AngusMcDoon]

If this was a serious issue why do those who have a common negative, and I suspect the majority of boats are set up like this, are not suffering this every time we start the engine?

Most boats now are not set up as the circuit in #66 which is why most people don't have the problem. It's not a case of a common negative point that all boats have, it's a case of a common section of negative cable shared by both circuits, which most boats now don't have since the prevalence of VSR's.

Despite your cynicism the Bedouin Theory is a real effect, although I like everyone else agree that it may not be the cause of the OP's problem.

 

[billskip]

From what the OP has posted he has changed something in his set up, only after that is he reporting a problem.

This old cynical engineer thinks that the OP has accidentally changed something.

Quite possible.

There are two discussions in this thread.
1) the original op's .
2) the bedouin theory...

 

[billskip]

it's a case of a common section of negative cable shared by both circuits

Despite you cynicism the Bedouin Theory is a real effect,

Another excellent explanation example from Angus.

 

[AngusMcDoon]

Unfortunately as this thread has shown there seems to be no way to simplify it sufficiently for the average forum users to understand

While Kirchhoff's laws are not difficult to understand solving circuits by hand using them quickly becomes an algebraic nightmare as the circuit & node count increases. CAD software packages dump all the simultaneous equation parameters in a matrix & use something like MATLAB underneath to solve them.

 

[B27]

If this was a serious issue why do those who have a common negative, and I suspect the majority of boats are set up like this, are not suffering this every time we start the engine?
...

It could possibly be that the starter motor is faulty, causing a bigger voltage drop?
Or the batteries are not fully charged?
Or the start battery is on its way out?
Or the engine is taking longer to start?
Or some common/bus-bar connection needs a clean?
Some exploration with a multimeter with a min/max function might be worth while.

Properly wired boats IMHO, should generally have the -ve of the starter battery wired straight to the engine.

Many years ago, I sailed on a boat with a 1-B-2 switch, the GPS would sometimes drop out, sometimes not, depending on the state of the batteries. We fixed it by running the GPS from a little sealed 12V battery and a handful of diodes.

It could be irritating back then, because early GPS sets took longer to wake up.

 

[Sandy]

Not that long ago (well last century but who is counting) 1-both-2 switches were pretty common and with that you have to accept everything cutting out when you start the engine.

That was never my experience, but my power demands have never been high. A VP2002 (18hp) and with everything on I struggle to consume 10 amps.

 

[Refueler]

QED. Pretty much everyone now realises you are wrong - however much we (now not just me but several others too) try to explain you don't get it and so you resort to insults. Behaviour most people grow out of by the time they get to secondary school. Perhaps if you were a little more open minded and realised that you don't in fact know it all you might learn something yourself.

Are you yet prepared to admit that what I said in my original post was 100% correct?

Blimey - how long have you been on this forum ??? And you haven't learnt to apply 'Paul factor' to his replies at times ??

I take far more stick from Paul than you ... and I apply the 'Paul Factor filter' ... and move on ..

No disrespect intended Paul ... just we all have our ways and styles ...

 

[Refueler]

Not that long ago (well last century but who is counting) 1-both-2 switches were pretty common and with that you have to accept everything cutting out when you start the engine.

[/QUOTE]

That only happens if the supply is not compensated to the instruments as I mentioned ages ago by use of a capacitor - to pick up the drop in voltage to the instrument.
The strange thing is that my Surrider with a 43HP Perkins started by a 90Ahr Cranking battery - usually does NOT cause my plotter etc. to drop out .. unless engine is really cold and doesn't start first press of button ... .

With the increase in demand on the domestic side (fridges etc) it became more common to have genuine 2 battery set ups with separate switches and presumably these include separate -ve from the start - it would be silly not to if you understand electrics and it only costs one extra wire.

So it is only likely to be an issue in boats like mine that were built with 1-both-2 but later had a second switch added to split the circuits. It would only take an extra length of wire for me to remove the common element but it really isn't an issue. While the GPS moans about the voltage it doesn't reset and even if it did being without GPS for a couple of seconds while I start the engine really doesn't bother me. I can use DR to project my position forwards for those couple of seconds.

I am intrigued by this 'adding a switch into a 1-0-2-B' setup ... I'm trying to get head around such an arrangement ... unless there's some fancy trickery going on - as soon as you engage that switch - surely you are powering as common base ?? Only way I can see any change - is if the 1-0-2-B switch is relegated to a charge only path switch ... but then how to de-power everything.

 

[bedouin]

I am intrigued by this 'adding a switch into a 1-0-2-B' setup ... I'm trying to get head around such an arrangement ... unless there's some fancy trickery going on - as soon as you engage that switch - surely you are powering as common base ?? Only way I can see any change - is if the 1-0-2-B switch is relegated to a charge only path switch ... but then how to de-power everything.

In the original set up the 1-2-both switch has three connections points. 2 for the +ve from each battery and a common that connects to both the engine / start and the domestic circuit.

To add the additional switch all you need to do is to take a (+ve) wire from the connection to which the #2 battery is connected and move the domestic supply to the other side of that switch. 1 switch and 1 short length of wire and we have independent +ve supplies - but still with a common -ve. In fact you also need to make sure the engine panel is powered from the same circuit as the starter so you may need another connection to the 1-2 switch common for that - depending on how your engine panel is connected. That leaves you with two separate positive feeds, one to the engine, starter, engine panel and one to the domestics. But you still have elements of the -ve circuits in common.

The old switch primarily switches battery 1 to start the engine but by switching to "both" still parallels the battery to allow both to be used for starting, or to allow the engine battery to help the domestic.

That is very similar to what would now be a standard 2 (or 3) switch set up with the 1-2-B switch serving as the engine/starter switch but with the both position serving as the "emergency parallel". And in fact it has the added benefit that it is possible to start the engine using only battery #2 - should one ever wish to do so.

 

[bedouin]

Blimey - how long have you been on this forum ??? And you haven't learnt to apply 'Paul factor' to his replies at times ??

I take far more stick from Paul than you ... and I apply the 'Paul Factor filter' ... and move on ..

No disrespect intended Paul ... just we all have our ways and styles ...

I think you know the answer to that

It concerns me when people say "I am an expert and this is gospel" and then go on to spout total nonsense. I think it is important to post the correct information. If people don't choose to believe me then that is their look out but at least I have challenged Pauls "alternative facts" and allow people to investigate further should they wish.

 

[AngusMcDoon]

It concerns me when people say "I am an expert and this is gospel" ...

I claim to be expert at nothing other than eating Jammie Dodgers. It's then easier to backtrack after inadvertently spouting wibble.

 

[Buck Turgidson]

Most boats now are not set up as the circuit in #66 which is why most people don't have the problem. It's not a case of a common negative point that all boats have, it's a case of a common section of negative cable shared by both circuits, which most boats now don't have since the prevalence of VSR's.

Despite your cynicism the Bedouin Theory is a real effect, although I like everyone else agree that it may not be the cause of the OP's problem.

#66 was my botched attempt to draw a simple circuit to discuss the problem. I think we all know that the diagram provided by Paul with the only common neg being a busbar (or stud) reflects the reality of how boats are wired.
I take full responsibility for derailing the discussion with an inaccurate diagram but we have subsequently shown that the normal method of individual circuits with separate negative tie between the batteries prevents the start induced voltage drop on the house circuit.
In the OPs case he didn't have the problem before adding battery capacity to the house circuit so there is no reason to suspect he is wired like #66.

 

[Refueler]

In the original set up the 1-2-both switch has three connections points. 2 for the +ve from each battery and a common that connects to both the engine / start and the domestic circuit.

To add the additional switch all you need to do is to take a (+ve) wire from the connection to which the #2 battery is connected and move the domestic supply to the other side of that switch. 1 switch and 1 short length of wire and we have independent +ve supplies - but still with a common -ve. In fact you also need to make sure the engine panel is powered from the same circuit as the starter so you may need another connection to the 1-2 switch common for that - depending on how your engine panel is connected. That leaves you with two separate positive feeds, one to the engine, starter, engine panel and one to the domestics. But you still have elements of the -ve circuits in common.

The old switch primarily switches battery 1 to start the engine but by switching to "both" still parallels the battery to allow both to be used for starting, or to allow the engine battery to help the domestic.

That is very similar to what would now be a standard 2 (or 3) switch set up with the 1-2-B switch serving as the engine/starter switch but with the both position serving as the "emergency parallel". And in fact it has the added benefit that it is possible to start the engine using only battery #2 - should one ever wish to do so.

Think this needs to go on a different thread to stop spoiling this one.

More explanation I think is needed because I cannot see any advantage with your setup as when you engage that extra switch surely you are just doing a BOTH scenario ??

I looked at adding a switch to my 'old switch' setup - but whichever way I drew the circuits I came back to BOTH ... the only way I could do it was to basically ignore two positions of the old switch and just use it purely as a single ON - OFF ... with other circuit completely independent with another switch to bridge if needed to put both systems together ...

 

[bedouin]

Think this needs to go on a different thread to stop spoiling this one.

More explanation I think is needed because I cannot see any advantage with your setup as when you engage that extra switch surely you are just doing a BOTH scenario ??

I looked at adding a switch to my 'old switch' setup - but whichever way I drew the circuits I came back to BOTH ... the only way I could do it was to basically ignore two positions of the old switch and just use it purely as a single ON - OFF ... with other circuit completely independent with another switch to bridge if needed to put both systems together ...

In normal operation the 1-b-2 switch is switched to "1" and connects battery #1 to the engine starter and circuits. The domestic switch is on and connects battery #2 to the domestic circuit. Only when the 1-b-2 switch is set to "B" are the #1 and #2 batteries connected together.

You wouldn't install it that way from scratch - you would use 3 separate switches as you describe - but given that I had a 1-b-2 switch to start with it only took one new switch and a short length on medium wire (about 6mm2) to do. And it does the job. (In fact I also added split charging diodes and a smart charger but that is a different issue).

 

[B27]

In normal operation the 1-b-2 switch is switched to "1" and connects battery #1 to the engine starter and circuits. The domestic switch is on and connects battery #2 to the domestic circuit. Only when the 1-b-2 switch is set to "B" are the #1 and #2 batteries connected together.

You wouldn't install it that way from scratch - you would use 3 separate switches as you describe - but given that I had a 1-b-2 switch to start with it only took one new switch and a short length on medium wire (about 6mm2) to do. And it does the job. (In fact I also added split charging diodes and a smart charger but that is a different issue).

This can make sense on many boats, for instance if the rest of the electrics are just a fridge, lights, VHF, instruments etc, the 'main domestic' switch can be much lower current