Start Engine w/ Electronics On?

[Dean Abramson]

I have long heard that it is not a good practice to start the engine when any electronics are turned on. The idea being that this could be bad for the electronic devices.

All that is well and good... until, while sailing I see a thunderstorm rapidly approaching. Then I want to drop sail and turn on the engine. I have been turning everything off before I do this. But it is always a little more suspense than I like, waiting for the GPS to get a new fix, and for the radar to warm up again.

Do I really need to do this? Is this just an old wive's tale in this day and age?

When I have forgotten to shut down first, and did in fact start the engine with everything on, all has always been well. But that has been very few instances in all these years.

I would really like to quit doing this, if it is safe.

Dean

[Dean Abramson]

bump

[sharkbait]

My guess is that it all depends upon how well your electrical system is designed. The major problem is that when you start the engine you place a tremendous load on the electrical system. Improperly designed the voltage will really drop when you hit the starter. This brown out will perhaps damage your electronics. At least, a lot of times, the systems will have to reset themselves. Put a meter on the circuit and see just how far the voltage drops when you hit the starter.

Hope this helps.

[jbenagh]

The voltage drop outs may cause parts in the power supply to operate slightly out of designed range but it is for such a short time there will probably be no ill effects. And really, if you are turning the starter, the voltage is probably within the electronics' design range.

I think the fear was voltage spikes, not the drop outs. At the starter motor turns you can get voltage spikes due to inductive effects. I think modern electronics (since 1990) is relatively immune to this due to the way power supplies have been designed since then. Especially so for electronics designed for the marine environment.

Jeff

[David VanDenburgh]

If it's any help, we have been starting the engine without turning electronics off for years and years. The electronics reset themselves afterward as a result of the voltage decrease, but there has been no damage. Seems like I read somewhere (Nigel Calder?) that there is a way to wire the circuits so electronics aren't affected by starting the engine, but I can't remember what it is.

[Maine Sail]

If you have a decent house bank with properly sized starting circuit wires, clean connections and a good ground there really should be no drop out of the electronics unless your bank is very small or getting long in the tooth. I have been starting on house banks for over 20 years and even with very deep cycle thick plate T-105's I've still never dropped electronics with a small diesel, when starting on the house bank, unless it was getting long in the tooth or the wire or connections were in-sufficient.

Keep in mind that automobiles with only one battery, often much more HP and just as "sensitive" electronics drop out many of those items with every start.

Now, if I start on my single group 27 'Starting Battery" I can see some drop out but not on my house bank.

I took a video a while ago after three nights on the hook and starting our 44HP diesel on the deep cycle house bank which was at 52% state of charge. Nothing dropped out. I'll have to dig it up and upload it...

A decent house bank almost always has more cranking amps than does a single "starting battery". Our house bank of three group 31 12V batts is well over 3000 cranking amps at 70F our engine requires about 300-400 CA by "spec" but actually only really uses about 130-160 amps for a couple of seconds....

I my electronics start dropping out on start, even 50% depleted, it is a good indication I need new batteries....

EDIT: Found the video and uploaded it.
http://www.youtube.com/watch?v=0Pzna7n1-fw

[Oswego John]

Hi David and all,

I would think that if the electonics were wired to the house batteries bank, then when you started the engine with the isolated starting battery, there would be no voltage drop or spikes affecting the electronics.

The various house circuits would have to be separate from the starting circuit by a selector switching system of some sort.

Best regards,
O J

Oops, sorry. I duplicated what Maine Sail had already told you. I guess that he sent his post in while I was writing mine.

As Archie says "Whatever",
O J

[David VanDenburgh]

Maine Sail and OJ,

Hi, guys. Nice to hear from you!

I agree with both of you. Ariel has two banks: Bank 1 is reserved for starting the engine; Bank 2 is used for everything else. Selecting Bank 1 powers everything from Bank 1, and selecting Bank 2 powers everything from Bank 2. When the battery selector switch is set to "Off", nothing on the boat has power except the bilge pumps. Here's where creeping senility plays a part: I can't remember whether selecting Banks 1 and 2 together provides enough capacity to prevent a start-up voltage drop from resetting the electronics. We'll have to get David Junior in here to straighten the old man out.

[Maine Sail]

You can have totally separate house and starting circuits but most boats don't and have the typical 1/2/BOTH/OFF switch instead.

If you have a 1/2/BOTH/OFF the multi-battery house bank almost always has more cranking amps available than does the "start" battery. The best way to avoid drop out, if it bugs you, is to try the house bank and use it for everything starting and house loads..

Doing this also avoids HEF (human error factor) and the forgetfulness of leaving the "starting battery" charging when you really needed the house bank charging.

I find it easiest for myself and customers to remember battery switch allocation like this:

Switch Position #1 = Primary/#1 Bank or House bank (this is your primary position and the one you use most often)

Switch Position #2 = Secondary Bank/Reserve Bank/Start Bank (this is your "secondary position" and one you only use in an emergency)

Many boats though are woefully under-wired when it comes to battery circuits and it may be wire voltage drop that is killing you not that the batteries can't deliver the CA without dropping below the electronics threshold.

Our boat has 2/0 battery wire and starting circuit wire. This was a HUGE difference from the 4GA it came to us with. We had over 1.5 volts of voltage drop JUST IN THE CABLE when starting the engine this is on top of how much the battery voltage dipped.

It was like we had a new starter installed. When I do this type of upgrade for customers they are always amazed at the difference in how their engine starts.

[John Danicic]

Starting.

I found it annoying that the electronics reset themselves after starting the engine so I completely separated the system so that the starting battery starts the engine only and the house does everything else including charging the starting battery via an Eco Charger. Much Much better this way. The engine could be started in a emergency by the house or a combination of both if need be. I simply added a second "1,2, both" switch and hooked the alternator output to the house bank. There is a start switch and a house switch. Both are left in their working positions while on the boat and off while away. Both banks charge when charging is available and only the house bank is used when there is no charging source on.
I second Maine Sail's suggestion that a larger starting cable helps immensely as Mariah came with a convoluted trail of cable from the starting battery to the starter. The engine could never start on just one battery. By shorting that cable by a good three feet and jumping two wire sizes, a dedicated starting battery, not a deep cycle battery is all you need to turn over the venerable Perkins and not effect anything else in the boat.

[David VanDenburgh]

John, thanks. I think we'll do just that on Ariel, beginning with a check of her conductor sizes.

Everything I know about wiring and electricity could be put in a thimble - with the girls finger inside.

BTW, if we were contemplating a first trip into Lake Superior from Lake Michigan - and could only stay a few days - where would you suggest we visit?

[John Danicic]

David:

I too am not terribly versed on electrics but I have Larry DeMers as my in-marina consultant so I am a very lucky CDer.

Larger cables are the way to start. The two switch system is also not too hard to do. I used the old switch and a new switch and mounted them thus.


There are also commercial versions available from West Marine that do the same thing.

You can view my crude wiring schematic minus the Echo Charger here.

Schematic

As far as Lake Superior is concerned, welcome! I know the western end the best. The Apostle Islands, and Isle Royal are not to be missed. A good start is to pick up Bonnie Dalhs book, Superior Way. A most excellent cruising guide for the big lake. I would be happy to speak further with you via phone or Email and would love to attempt a hook up somewhere in Gitche Gumee.

[David VanDenburgh]

John, and if you get into Lake Michigan, give me a call. Perhaps we can meet up somewhere around Mackinac or Beaver Island.

[Dean Abramson]

I guess this is a dumb question, but what do you mean the electronics "reset?"

As in: the GPS goes off for a spilt second, but then comes back on but has to wait for a new fix?

(The few times I have done this, nothing adverse happened at all.)

Dean

[John Danicic]

Before I separated the wiring, when ever the engine was started, the instruments; speed and wind would loose their maximums but the big thing was the auto helm would loose its course setting. It didn't seem to effect the GPS which had a battery backup. If you have old style mechanical or simple low power instruments, it wouldn't matter.

Electronics really are a house of cards.