Nav instruments turn off when engine starts

davethedog

davethedog

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Hello all,

Just a question and am sure there is a fix for this, but if we are sailing and have the chart plotter and ray marine instruments on, when we decide to start the engine the chart plotter and instruments turn off as the engine starts (drawing the current).

So, is there a way to fix this, as the instruments not an issue but the chart plotter then has to be played about with to get the route we were following back up.

Thanks

DTD
 
Have had this when using the Anchor windlass - will rewire that to the Bow Thruster Battery as it's likely a spike ( what is a negative spike ) on the 12volt is causing it - in your case it's when you start your engine.

Can you describe your Boat and Electrical systems ( no of house batteries etc )

Kevin
 
Have 2 domestic batteries (115Ah each) and also a separate engine starter battery.

Are you saying we should only use the engine start battery to ever start the battery, and use the 1-2-both switch to facilitate this? As usually we start the engine at the marina using the engine start battery and then we switch to the 2 x domestic batteries after about 20 mins. When we have then decided to start the engine later have not turned the switch and let it on the domestic batteries.

paul, as you say it may be easier to just switch to the engine start battery every time we want to start the battery as the nav instruments are always powered from the domestic batteries even when all are turned off using the switch.
 
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davethedog said:
Have 2 domestic batteries (115Ah each) and also a separate engine starter battery.

Are you saying we should only use the engine start battery to ever start the battery, and use the 1-2-both switch to facilitate this? As usually we start the engine at the marina using the engine start battery and then we switch to the 2 x domestic batteries after about 20 mins. When we have then decided to start the engine later have not turned the switch and let it on the domestic batteries.

paul, as you say it may be easier to just switch to the engine start battery every time we want to start the battery as the nav instruments are always powered from the domestic batteries even when all are turned off using the switch.
Click to expand...

Your instruments die because the voltage drops. To avoid this, you'd need to turn the 1-2-Both switch back to the start battery. Frankly, 1-2-Both switches are outdated and potentially problematical - there are much better solutions today. If you rewired with a VSR or a low-loss splitter, you'd have none of these problems.
 
davethedog said:
Have 2 domestic batteries (115Ah each) and also a separate engine starter battery.

Are you saying we should only use the engine start battery to ever start the battery, and use the 1-2-both switch to facilitate this? As usually we start the engine at the marina using the engine start battery and then we switch to the 2 x domestic batteries after about 20 mins. When we have then decided to start the engine later have not turned the switch and let it on the domestic batteries.

paul, as you say it may be easier to just switch to the engine start battery every time we want to start the battery as the nav instruments are always powered from the domestic batteries even when all are turned off using the switch.
Click to expand...

No criticism of you intended Dave as I don't even have one of these 1-2-Both thingies ..... but I'll bet your experience sparks a series of "1-2-Both gizmo" condemnation posts. :)

Based on your experience, I'm glad I don't have one.

Richard
 
RichardS said:
No criticism of you intended Dave as I don't even have one of these 1-2-Both thingies ..... but I'll bet your experience sparks a series of "1-2-Both gizmo" condemnation posts. :)

Based on your experience, I'm glad I don't have one.
Click to expand...

:D Ha! As one of the most vocal haters of 1-2-Both switches, I reckon you'll find that the defenders will queue up to say "nothing wrong with mine, it's worked well for 65 years". But the opportunity for the wretched thing to be set wrongly, or accidentally left on the wrong setting, is huge, with consequent risk of inability to start the engine.

Still, I suppose it gives the RNLI lots of practise rescuing stranded boatowners.
 
1-2- Both, neither.

Does depend on what has happened to the wiring over the years.
THe experts will be along to confuse us all in a few minutes.

Our experience was that when we removed said 'switch' and put a Diode charge splitter in then all our problems and about 20 metres of surplus wires disappeared. Turned out the switch was actually bust and turning the switch just mean that all the batteries were connected to each other whatever happened.

All sorts of junk had been added to the system over the years and volts were wandering all over the boat before they got to do whatever they were intended to do. There was also a variety of wires that delivered electrons into the void, if that can happen. That is wires that were connected to the fuse board but not connected to anything.

Now the more enlightened members will also tell you the a VSR [voltage sensitive relay] is the way to go these days. Well, I spent more than £60 on diode splitter and I am using that until it expires.
 
davethedog said:
Have 2 domestic batteries (115Ah each) and also a separate engine starter battery.

Are you saying we should only use the engine start battery to ever start the battery, and use the 1-2-both switch to facilitate this? As usually we start the engine at the marina using the engine start battery and then we switch to the 2 x domestic batteries after about 20 mins. When we have then decided to start the engine later have not turned the switch and let it on the domestic batteries.

paul, as you say it may be easier to just switch to the engine start battery every time we want to start the battery as the nav instruments are always powered from the domestic batteries even when all are turned off using the switch.
Click to expand...

This will solve your problem ......... (but its a pain remembering to to do so and you will periodically forget!)

Then after allowing the start battery recharge again switch back to the domestic bank.

Take care that when you switch from one bank to the other you do so by moving the switch via the the "both" position if the engine is running. If you switch to "Off" you will probably blow the diodes in the alternator!


The way forward, if you want to, is to separate engine and domestic circuits, feeding them via separate isolator switches from their respective dedicated battery banks.

Some form of split, charging, eg a VSR or diode splitter, will also be needed to ensure both battery banks are charged. Diode splitters have the disadvantage that they introduce a volts drop of about 0.7v unless the alternator can be converted to "battery sensing"

A cross over switch will allow both banks to be combined if necessary, or allow one or other of the battery banks to be used exclusively if the need arises
 
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davethedog said:
Have 2 domestic batteries (115Ah each) and also a separate engine starter battery.

Are you saying we should only use the engine start battery to ever start the battery, and use the 1-2-both switch to facilitate this? As usually we start the engine at the marina using the engine start battery and then we switch to the 2 x domestic batteries after about 20 mins. When we have then decided to start the engine later have not turned the switch and let it on the domestic batteries.

paul, as you say it may be easier to just switch to the engine start battery every time we want to start the battery as the nav instruments are always powered from the domestic batteries even when all are turned off using the switch.
Click to expand...

A fix and a vastly better system is easily done Dave. Ditch the 1-2-both switch and fit a pair of separate switches, one for the engine battery, which only gets used for the engine and one for the domestics, which (you guessed it) are for everything else. A VSR will sort the charging of both banks.

No more fiddling with switches, no more electronics going off and a much better system in terms of redundancy. It's a good idea to fit a third switch, which acts as your "both" setting, for emergency starting.

Edit : Beaten to it by Vic :)
 
Try wiring the plotter with a suitably heavy gauge wire to a point close to the battery switch, then start the engine. I'd bet the plotter will stay on, and if so the problem is due to voltage drop in the wiring. No need to disconnect anything, just don't confuse the positives with the negatives!
 
VicS said:
Some form of split, charging, eg a VSR or diode splitter, will also be needed to ensure both battery banks are charged. Diode splitters have the disadvantage that they introduce a volts drop of about 0.7v unless the alternator can be converted to "battery sensing"
Click to expand...

Not necessarily, you can use a low-loss splitter (as suggested in post 6) which has minimal voltage drop. My boat has a Quick low-loss splitter, which drops less than 0.05V at a 20A charge.
 
PaulRainbow said:
A fix and a vastly better system is easily done Dave. Ditch the 1-2-both switch and fit a pair of separate switches, one for the engine battery, which only gets used for the engine and one for the domestics, which (you guessed it) are for everything else. A VSR will sort the charging of both banks.

No more fiddling with switches, no more electronics going off and a much better system in terms of redundancy. It's a good idea to fit a third switch, which acts as your "both" setting, for emergency starting.

Edit : Beaten to it by Vic :)
Click to expand...

Thanks for all this and may look at this option in the future and if so what is the best way to wire this in and get rid of the 1-both - 2 - off switch, and put in the split charge relay etc
 
+1 for ditching the "spawn of the devil" 1-2-both switch. Although you don't have to ditch it, as there are enough supporters on here than some mug will buy it in the For Sale section. :)

As said above, you can replace it with three individual switches. Wire them with one switch to connect the starter battery to the starter circuit, one to connect the domestic bank to the domestic circuit and a third emergency switch to connect the domestic bank to the starter circuit (note: that latter isn't a link switch - you'd have to turn both it and the starter switch on to link the batteries).

You can then wire in a VSR to take the alernator output and connect it to the starter battery and to the domestic bank (I use a Sterling A2B booster rather than a VSR but the connectivity is very similar).
 
davethedog said:
As usually we start the engine at the marina using the engine start battery and then we switch to the 2 x domestic batteries after about 20 mins.
Click to expand...

Why wait 20 minutes? Replacing the charge lost in starting (actually very little as it's such a short term load) should not take anything like that amount of time. Making up for the self-discharge since previous use is also unlikely to take long.

Of course, a VSR (voltage sensitive relay) between the engine and domestic batteries would take all the fun and skill/guesswork out of it, and start charging the domestics just as soon as the engine battery is back up to about 12.8 volts.
 
LittleSister said:
Why wait 20 minutes? Replacing the charge lost in starting (actually very little as it's such a short term load) should not take anything like that amount of time. Making up for the self-discharge since previous use is also unlikely to take long.

Of course, a VSR (voltage sensitive relay) between the engine and domestic batteries would take all the fun and skill/guesswork out of it, and start charging the domestics just as soon as the engine battery is back up to about 12.8 volts.
Click to expand...

In reality, it doesn't work like that. The relay "sees" the alternator voltage and the relay switches straight away.
 
davethedog said:
Thanks for all this and may look at this option in the future and if so what is the best way to wire this in and get rid of the 1-both - 2 - off switch, and put in the split charge relay etc
Click to expand...


Very straightforward to do. You leave all of the negative wiring as it is. Connect the engine to the engine battery, via the switch. Connect the domestic circuits to the 2nd switch and the domestic bank. Fit a third switch and connect this between the output terminal on the engine switch and the output terminal on the domestic switch. The third switch will then allow you to start the engine from the domestic bank or to use the engine battery for domestic use, in an emergency. A VSR is just a case of a positive wire to each battery bank and a negative to a battery negative. Fuses fitted where appropriate of course.

If there is any chance of adding a solar panel, fit a dual sensing VSR. That way, you can connect the solar panel to the domestic bank and if it reaches a set voltage the power also goes to the engine battery.
 
PaulRainbow said:
In reality, it doesn't work like that. The relay "sees" the alternator voltage and the relay switches straight away.
Click to expand...

Not on my boat, it doesn't! If the engine battery is low it takes a short while for the relay to cut in (as shown by the VSR indicator light).

According to Merlin, who make and sell the things: 'VSR's initially stay open (off) when the engine is charging the engine start battery, therefore, the engine battery is priority charged. Once the engine battery has reached 13.7V from the alternator charge, the relay will close allowing both engine and domestic battery banks to be charged simultaneously. When the engine is stopped, the voltage returns to normal levels allowing the relay to open again - separating the engine and auxiliary batteries. '

Link: http://www.merlinequipment.com/markets/group.asp?groupid=37
 
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