Plotter dies when starting engine

[Cadence]

Originally Posted by Stu Jackson

Before you question your switch consider the wiring, voltage drop and connections to your plotter.

Agree!
I'll bet you are wired to the state battery directly. The switch is no factor and your start battery is about shot.

[Bluemansailor]

This happened on my boat when i first brought. What some idiot in the boatyard did was wire a fuse panel for the gps directly on to the starter......trace your power wire from the gps ....

[handcrafter]

You can spend a lot of time chasing electrical gremlins. Behavior might give you an edge, however. Turn on all engines before turning on marine electronics and in reverse, turn off all marine electronics before shutting down engines. At least you'll be protecting against known possible power fluctuations.

Consider that for our AC powered computers we have UPS devices to guard against power spikes or brown-outs plus they deliver pure sine wave proper voltage. How many non-commercial boaters have a DC powered UPS protecting their precious marine electronics? Hint, they're big and bulky and expensive and generate a lot of heat. Perhaps the same companies that manufacture marine electronics will come up with compact & affordable DC UPS devices. OK, maybe I'm dreaming.

[Squanderbucks]

I like to have a separate sub-panel for all of my electronics with it's power coming directly off the batteries or right after the main fuse on the DC power line. also, I have a Newmar StartGuard that the power feeds into before going to the electronics subpanel. Essentially a capacitor and internal battery similar to described by a few above but all in an easily installed commercially built component. Works well. I have the same Garmin chartplotter and do not get the restarting issues any longer since I made these changes.

[Martkimwat]

Just solved a similar problem on my boat by replacing the house battery 'red' key type switch which had obviously developed a high resistance. My coolbox would keep going into fault mode even though the battery voltage was saying that there was 12.9V present at the battery and around 80% charge. It got worse over the last few weeks and ended up with me losing all my instruments after a couple of hours of sailing and the power would only come back if I started the engine momentarily. Swapped out the key switch and order was restored.

[Martkimwat]

Further to my last post, I noticed you said you had always had the problem since you have had the boat, in which case it could be undersized wiring to the plotter. Surprisingly I have noted on several plotters in the past that the supplied wiring is only just adequate even if you do not need to extend it. If the wiring run is longer than the supplied wire then definitely need to up the wire gauge.

[frankmulder217]

I have been reading all of the comments and what I mis here is the reason why your voltage drops when starting the engine from the other bank. That really does not make sense, since the + of the starting battery is not connected to the + of the service battery, but you might be mistaken! Through your 1, 2 both switch you have an almost perfect isolation between the plusses, but almost perfect is enough to make them the same when your minus levels are floating.

What happens if you have a floating zero when you start is that you"lift" the negative from the engine to for instance 10 volt below the common plus of both banks. If you wired your plotter to plus of the service and the minus of the engine, your voltage would be between the plus of the service and the minus of the engine which is reduced when you start.
The solution is simple: Connect minus from both banks.

Even if that is not the problem you should always have a common zero level on the boat.

[dw1979]

I agree with the suggestions to put all of the electronics on a separate circuit with their own battery. You can use an ACR-si to isolate the electronics on start up. It will keep your voltage to the electronics from dipping on startup of the engines and protect from potentially damaging voltage spikes.

[barnakiel]

Just a voltage drop. I was forced to sort it out on a friend´s boat where his Furuno kit behaved exactly the same.

There can be a number of reasons starting with the starter, moving on to the batteries then on to the switches, cables, connectors, etc.

Our boat is started from the starter battery so the electronics is never affected.

Can you possibly adjust your wiring and have the starter wired only to a dedicated starter battery?

b.

[roland stockham]

1,2 both switches are notoriously unreliable in my experience and almost certainly what is happening is that the starter is drawing power from the house bank. Voltage normally drops below 10.5 when the starter is running which will knock out all nav instruments. The remedy is either connect the start batt to the alternator then a no volt drop relay to the house bank. Or use a diode distribution block to isolate the batteries from each other and create an automatic charging setup. Remember that if using a diode block you MUST also fit an external battery senses regulator to the alternator or the batteries will never get to full charge. Diode block correctly set up give the best results as you then have a full 3step charger just like the shore power one and it will reduce charging time by about 60% compared to a machine sensed alternator but it is both more expensive and more technical to set up, depends how often you charge from the engine as to whether it is worth it. Most marine electronics manual give you all the details. Machine sensed alternators are fine on motor boats where engines run most of the time but not good on a sailboat that only runs the engine for short periods. They are designed to maintaine batteries at full charge and provide power to services not to recharge significantly discharged batteries (less than 80% discharge)

[Sandibar]

Wow. Thanks for all the information and suggestions! A couple more clarifications. The negatives are common for both banks. The main switch specifies which battery is used for all jobs, so "1" uses the starter for starting but also for the electronics, and "2" the house bank. Same goes for the charging from alternator.
The problem also occurs when using house bank for starting (which is rare). Based on the reading here, I guess the quickest potential fix would be to run the nav electronics through a separate panel straight off the house bank, bypassing the main switch as well. That's a 30 min job and I may well do it, the VHF is already done that way. Will still try to get the root problem fixed if possible, i.e. check all the connections for excessive resistance. Will let you know how it goes.

[Uncle Bob]

Originally Posted by Sandibar

Wow. Thanks for all the information and suggestions! A couple more clarifications. The negatives are common for both banks. The main switch specifies which battery is used for all jobs, so "1" uses the starter for starting but also for the electronics, and "2" the house bank. Same goes for the charging from alternator.
The problem also occurs when using house bank for starting (which is rare). Based on the reading here, I guess the quickest potential fix would be to run the nav electronics through a separate panel straight off the house bank, bypassing the main switch as well. That's a 30 min job and I may well do it, the VHF is already done that way. Will still try to get the root problem fixed if possible, i.e. check all the connections for excessive resistance. Will let you know how it goes.

Ah, so the plot thickens . The start bank should be used for just that, starting the engine, all other loads should run from the house bank, with perhaps the exception of the electric windlass. A charged house bank that is separate from the engine will suffer no voltage fluctuations on start up so the electronics should not be affected.

[Sandibar]

Originally Posted by Uncle Bob

Ah, so the plot thickens . The start bank should be used for just that, starting the engine, all other loads should run from the house bank, with perhaps the exception of the electric windlass. A charged house bank that is separate from the engine will suffer no voltage fluctuations on start up so the electronics should not be affected.

Starting to see that . I really thought the set up I have is 'normal', but maybe it's not. Actually, come to think of it, it would be just as easy to bypass the 1-2-both main switch and feed the existing panel directly from the house bank (add a dedicated main switch for it). Then the original switch would just be used to control which battery is charged from the alternator (or, of course which battery fires the engine if starter battery for some reason dies).

[hzcruiser]

Originally Posted by handcrafter

[...] DC powered UPS protecting their precious marine electronics? Hint, they're big and bulky and expensive and generate a lot of heat.

Hint: they already exist and are generally referred to as "batteries". Maybe that's why your Google search for "DC powered UPS" came up empty?

But to add my 2c to the discussion, there is a slight chance that it's not (just) brown outs but also voltage spikes induced by the starter motor that might throw your electronics off.
A simple remedy for that could be to add a $2 powdered iron toroid into the supply voltage cables. Just 3-5 wraps will reduce voltage spikes and drops as well. You can get them at any electronics shop.

[guyrj33]

MRM's advice and instructions on how to check the circuit for voltage drops is spot on. Following this advice will allow you to find the root cause of the problem and fix it. All other suggestions about isolated batteries and switch replacements are just suggestions that may or may not solve the problem.
Trace and measure the circuit, understand the cause of the problem and then design and implement your repair.

Originally Posted by mrm

Certainly. Given a circuit with a charge source, a battery and a load, including multiple connections as illustrated, measuring abnormal voltage drop in a part of the circuit narrows down the search. For the pictured example, say:

voltage 'e:m' is 12V (battery voltage under load)
voltage 'g : o' is 10V (voltage at load)

so 2V are lost somewhere. Now you measure, for example:

'e:d ' = 0.1 V
'd:f'' = 0.2 V
'f:g' = 0.4 V
'm:l' = 0.1 V
'l:n' = 0.9 V
'n : o' = 0.3 V

Such measurements would prompt for closer examination of the l:n part of the circuit including wiring and connectors. Charging side can be tested using the same method.