GPS crashes on starting the engine

[Skylark]

I've recently bought a Beneteau Oceanis 361. The GPS and Plotter crash each time I start the engine. The Navman GPS will not restart until someone has been despatched below to press the buttons! The boat is 6 years old. It has 2 batteries but no separate "engine" and "domestic" circuits. One of the batteries was replaced at the start of the seaon, the other is original but seems fine. Short of re-wiring to provide separate circuits, which I'm not proposing to do, any suggestions to overcome the problem? Much appreciated, many thanks.

 

[fireball]

It does sound like it could be a voltage problem ... does it happen when using one battery in particular or both?

 

[hubert]

Almost certainly the problem is due to voltage drop under load. It could be simply a high resistance in the battery connection. Try cleaning the connections.

 

[gfbalduc]

Quite possibly your 6-years old battery may be near the end of its useful life.

Check with a voltmeter what is each battery's voltage at rest with nothing connected (should be at least 12.6V) and then check what happens to battery voltage when you start the engine: if it goes near or below 12V, it's not too surprising if some instruments reset.

If this happens, check all cable connections for anything loose or corroded, if all OK then your old battery is probably due for replacement, or your battery bank is badly underdimensioned to start the engine (unlikely).

 

[MacW]

Maybe this is a bit like a car ignition switch - as soon as you turn the key that last bit to start the switch turns other circuits off. Check what other items on the boat momentarily go off, - interior lights, nav lights, tape player etc. It may be that the GPS and the plotter are simply wired into the wrong power circuit

Pete

 

[billskip]

It is possible you DO have seperate circuits

However the easy way to do a quick check is to switch on a cabin light and see if it goes off or dimms significantly when you start the engine.

The norm is as said by others ...connections ,etc.

but it is possible that someone has cobbled the supply and connected it to an off position on your ignition switch..or connected the supply to the starter battery instead of the domestic..question is "has it just started to happen ?, or was it like it when you bought the boat?

do the simple checks first...but it wont do any harm to check all connections as a matter of service and keeping all in good condition

 

[Remmington]

Why not start the engine before powering up nav gear

 

[lw395]

They all do that Sir!
Same problem with my Garmin, it needs about 9V to survive, cranking reduces volts to about 8, which is pretty typical. Only solution is to power GPS from another battery, perhaps a small sealed type. You can charge this using a diode from main supply, but care is needed. Also consider effects of NMEA (etc) interface having different supplies at each end, if the instruments are not all on the same rail.

 

[duncan]

yes it's voltage but which bit of the system is at fault is difficult to predict - as others have highlighted.

I had it start to happen on my fishing boat and it's a real pain when running drifts to have the plotter restart every time - so I had to do something! Mine turned out to be the battery master switch starting to fail and causing excessive voltage drop when engine starting. Glad I found the problem and changed it.

 

[jleaworthy]

Forgive my ignorance but does your GPS have a facility for an internal battery? If so, fitting one should avoid the problem as it does with my handheld units. The internal battery kicks in automatically as voltage drops.

 

[pappaecho]

If you have two batteries, one engine and one domestic, as long as the electronics are connected to the domestic bank, there should be no voltage drop and hence your problem will go away

 

[Dave99]

As you say short of a little bit of rewiring so that the engine battery is separate from domestics it is a fact of life.

The changes required aren't that hard - at the end of the day the engine feed will come straight off the batteries anyway leaving a couple of wires feeding the domestics. You just have to isolate them from each other for taking power and then put in a split charge diode to enable both batteries to still charge from the alternator

 

[alan]

I think that you may find that your batteries are wired in parallel (Beneteau standard wiring trick on older boats) at the load side of the isolator switches. Which means that when both isolators are closed and you start the engine then both batteries are in use and the volts drop is "felt" on both batteries, and this can cause some instruments to drop out. I get used to get this on my 311 with the plotter. When starting at the dockside it wasn't usually a problem beacuse I started with only the engine battery and then closed the domestic breaker and then switched on the instruments; but when going from sailing with only the service battery in use and then switching on the engine battery and starting the engine the plotter would drop out and then need to be switched back on - a bit of a p.i.t.a.
A solution is to take off the wire that parallels the batteries (short piece of red wire joining the two isolator switches). However, this means that you won't be able to use the service battery in an emergency situation. So, cheap fix is to carry some car jumper cables with you; more expensive fix it to fit a third isolator which can parallel the batteries in an emergency; full fix is to fit isolating diodes, smart regulator and a third emergency isolator (for paralleling the batts) or an SCR and a third emergency isolator (for paralleling the batts).

Pretty sure that if you check you will find that Beneteau have put this parelleling wire on the isolators, so if you remove that the engine starting load will not pull your domestic battery down.

Alan.

 

[searover]

agree with most you need to have your instruments on separate supply to your engine start battery. which is i supose obviouse really!!

 

[Heckler]

have another look at your battery switches, the 361 is realtively new and the benes of this age have 1 common negative switch and 2 other positive. you can switch on your starting circuit or domestic circuit with the relevant switch. so common and on or common and the other or both so that all 3 are on to give equalising. Sounds as if you have all 3 switched on with a knackered battery in circuit.

 

[billskip]

Skipper_stu..If what you say is applicable to his boat ..ie..1common -ve and 2 switched +ve .. (altho he say he doesnt have a switch )

The problem might well be that he has a high resistant -ve ..which means that when he cranks the engine he does not infact get a volt drop at his instruments with respect to +ve and battery -ve..

The -ve cable could be in fact "going high" causing a lower PD at the instrument.

easy way to chech this is to put volt meter at starter motor -ve or engine -ve and the -ve pole on the battery..there should be no volts....when cranking if the meter shows volts (it should not) then the PD at any instrument will go down..and switch off.

problem is some people get confused by thinking the +ve is being "lost".. infact in some cases it has nout to do with the +ve..

remember (simple way) +ve charged is minus an electron and wants one back therefor
current flows from -ve to +ve Not +ve to -ve /forums/images/graemlins/confused.gif /forums/images/graemlins/grin.gif

 

[William_H]

High David 361 are you starting the engine on both batteries. If so what happens when you start on either battery alone. If it is your habit as do many to start on both batteries you may find that one has died without you knowing. In which case it is just time before the other dies and you can't start at all. Old batteries as one sign of aging have a greater voltage drop on starting resulting in slow cranking.
The main reason for having dual batteries is so you have a reserve for engine starting if the one used for doemestic is discharged.

Now a fix for the plotter/GPS dropping out is to fit a diode (silicon) in series with the power supply. This will reduce the voltage by .7 volt but this won't matter. On the GPS side of the diode you fit a large capcitor from +ve to -ve. This works like a battery but has much less capacity but no problem with being discharged or overcharged.
The capacitor must be an electrolytic type of 10000 microfarrads or so and rated at at least 18 volts. Capacitors can be wired in paralell to add their capacity. The more capcity the more capability to run the GPS for prolonged cranking. Less capacity may well do the job. It depends a bit on how much current the GPS draws.
The diode allows the GPS to function without having the capacitor charge run back to help start the engine. The diode needs to be rated at 5 amps or so. They and the capacitors are quite cheap at Maplins or RS. olewill

 

[Guest]

[ QUOTE ]
I've recently bought a Beneteau Oceanis 361. The GPS and Plotter crash each time I start the engine. The Navman GPS will not restart until someone has been despatched below to press the buttons! The boat is 6 years old. It has 2 batteries but no separate "engine" and "domestic" circuits. One of the batteries was replaced at the start of the seaon, the other is original but seems fine. Short of re-wiring to provide separate circuits, which I'm not proposing to do, any suggestions to overcome the problem? Much appreciated, many thanks.

[/ QUOTE ]

This is actually a common problem and is difficult to cure without wiring the GPS separately to power. You are dragging the voltage down when hitting the engine starter sufficient for the GPS to drop out. MY Magellan was a pain for it ... and my Lowrance until I led a separate fused lead for it.

There are ways to incorporate an electronic item as I've been told to momentarily hold the voltage up to stop it ... but I'm no electronics expert - so extra lead it was.

 

[Guest]

[ QUOTE ]
As you say short of a little bit of rewiring so that the engine battery is separate from domestics it is a fact of life.

The changes required aren't that hard - at the end of the day the engine feed will come straight off the batteries anyway leaving a couple of wires feeding the domestics. You just have to isolate them from each other for taking power and then put in a split charge diode to enable both batteries to still charge from the alternator

[/ QUOTE ]

Sorry Dave ... I like the ---- put in a split charge diode etc. Considering that possibly 99.9% of alternator / battery set-ups are not battery sensed - this will be a disaster ..... because he will now have lower charge voltage and basically batterys will soon give up.

His problem is that he has a common bank - he said so - this leads to sufficient voltage drop when he hits starter button .... QED. All he has to do is separate the batterys and wire GPS / other gear to one

It's one of the most common problem with gear on boats ....

 

[onarampage]

Electronics crashing during engine start...

David - are you still having this problem? I know this is kind of an old thread, but I'm new to this forum. I am coincidentally exploring opportunities with an aviation equipment manufacturer and looking at some potential cross-over products. I may (in the future, I don't currently) come to represent a company called TCW Technologies. One of their products provides a stable electrical supply regardless of voltage drop during engine(s) start. Apparently in an homebuilt airplane a common problem is having your electronics crash as you start your engine. TCW has come up with a cool product that over-comes this issue. They are a start up company and are starting to make some big waves in the Homebuilt aircraft industry and have come to me to explore the opportunities for some of their products in the marine industry. I know this seems like a spam post (especially since it is my first!) and I apologize for that, but hey everybody's got to start somewhere!
Feel free to contact me or check out www.tcwtech.com for their Intelligent Power Stabilizer
- Glen