Basic starting circuit

reeltime · Mar 12, 2020

Hi Guys .Im rewiring a boat and want a basic functional start circuit and wondered if this would work , 3 switches near the helm out of the engine room 2 mtr run for the wire from batteries in the engine room to the starters via the main switches .Any imput would be appreciated.

Redhook98 · Mar 12, 2020

I would have a separate for the gen. keep that in reserve. Are any of these serving a house-battery function?

rslifkin · Mar 12, 2020

Given 2 engines, I'd want 2 start batteries. Gen can share with one of the engines as it likely needs less power to start. Just add switches so either engine or the gen can be started from either battery. Personally, I like to keep house completely separate. Partly to avoid ever killing a start battery and partly to keep electronics separated from voltage dip at engine start (it sucks to have all of your electronics reboot when you start an engine).

Bacchus · Mar 12, 2020

Keith
I moved this from Welcome Mat to Maint & Systems - Power Systems to hopefully attract more responses.
Welcome aboard TF.
My $0.02
You don't show any solinoids (relays) to separate hi Amp circuit from low amp circuit which are used on essentially all starting circuits.
As a reference I'd suggest you take a look at Nigel Calders book "Boatowners Mechanical and Electrical Manual"
https://www.amazon.com/Boatowners-Mechanical-Electrical-Manual-4/dp/0071790330
It is a well regarded reference for boaters.
Be very cautious with modifying starting circuits as they are very high amp circuits, frequently not protected by fuses and can be hazardous if not installed safely.
Advice and an inspection by a marine electrician is advised if you are new / untrained in this area.

High Wire · Mar 12, 2020

Yes it will work for engine starting. Lots of extra connections shown. Simplify. The port engine may need a separate post to hold all of those terminals.

No chargers.
No house bank.
No monitoring.
No accessories like a windlass or thruster that are powered while the engine is running.

The ground symbol is simplistic of what is actual.

DavidM · Mar 12, 2020

That diagram is more of a charging/power distribution diagram than a starting diagram. No starting switches, stop switches, solenoids, etc. But as far as it goes, ok.

The one thing to reconsider is that you are using the port engine's battery to start the genset. I would prefer a separate genset start battery for redundancy with appropriate isolation from the others.

David

tiltrider1 · Mar 12, 2020

I can’t really tell you that it will work, there are to many details left out of the starter connection. My questions are why 3 switches and not a 12all switch and what is the goal, simplicity, use less wire, batteries in different locations?

reeltime · Mar 12, 2020

Hi , Yes this was just power to start engines ,each engine has a battery except the gen set shares with port engine , I no no stops /start etc shown , that's easy enuff to sort later .The gen set runs to house batteries for dashboard and winch etc .This diagram is starting only and link if needed to recharge .A 12both wouldn't work in my mind ,please explain how ?cheers

rslifkin · Mar 12, 2020

In my mind, each engine and the generator should have their own 1-2-both-off switch. That allows any engine to be started from either of the starting batteries in case something happens to one of them.

Peter B · Mar 12, 2020

Bacchus said:
Keith
I moved this from Welcome Mat to Maint & Systems - Power Systems to hopefully attract more responses.
Welcome aboard TF.
My $0.02
You don't show any solinoids (relays) to separate hi Amp circuit from low amp circuit which are used on essentially all starting circuits.
As a reference I'd suggest you take a look at Nigel Calders book "Boatowners Mechanical and Electrical Manual"
https://www.amazon.com/Boatowners-Mechanical-Electrical-Manual-4/dp/0071790330
It is a well regarded reference for boaters.
Be very cautious with modifying starting circuits as they are very high amp circuits, frequently not protected by fuses and can be hazardous if not installed safely.
Advice and an inspection by a marine electrician is advised if you are new / untrained in this area.

I would very much echo this post above, re not only the best place to put the thread, but the bit about getting a marine electrician to check it all out - preferably do it as well. :flowers:

tiltrider1 · Mar 12, 2020

I just realized that the OP is from the Cook Islands so a marine electrician might be difficult to come by.

The diagram is not how I would do things and I feel it leaves a lot of room for ending up with dead batteries but the system would work. However if the starboard battery was dead there is a real probability that you will be unable to start the starboard engine off the port battery due to no ability to isolate the dead battery from the system. The same is true for the port side.

reeltime · Mar 12, 2020

True ,cook islands not a lot of options here.
If the STBD battery was flat ,yes I cant isolate it ,but couldn't I charge it from the port motor by closing #2, switch until charged enough to help crank stbd engine after closing #3

reeltime · Mar 12, 2020

I like that idea , just need to sort out the circuit , thanks

reeltime · Mar 12, 2020

A

Another simple circut

reeltime · Mar 12, 2020

Gen set only does house bank and 12 v & 120 v & Windlass

rslifkin · Mar 13, 2020

If you're going to do 3 switches, I'd just do a 1-2-both-off switch for each engine / gen. Makes life easier if one of the batteries fails, rather than going dead, as you can just switch all 3 to the other battery and leave it until you can get a new battery.

FF · Mar 14, 2020

IF you purchase a 1-2-All rotary switch be SURE it included field disconnect terminals .

Switching off an operating alt will usually blow the diodes in it.

The field terminals in the better rotary switches are "break before break " they cut the field before cutting off the battery .

Began · Mar 15, 2020

I'm in late and trying to understand- how is it you have 2 separate 12v connections on the genny? One 12v is house and the other is the port battery? You indicate them as separate circuits?

Began · Mar 16, 2020

Are you saying that the Gen alt charges the house battery but uses the port battery to start?

Basic starting circuit

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