Boat wiring and charging

[davidej]

Which all leads to the inevitable conclusion that the motor battery should normally start the motor, not just in an emergency

Halcyion - why go for some non-standard solution which may work but no one except you will understand. Use the normal solution recommended by me and all the other contributers.

As regards the VSR, I think it will always draw a small current while the motor circuits are energised by switching the motor isolator battey on - but I think it will be in milleamps.

 

[davidej]

Sorry - I meant the advice to be to Portvasgo, not Halcyon and sorry for the misspelling

 

[VicS]

As regards the VSR, I think it will always draw a small current while the motor circuits are energised by switching the motor isolator battey on - but I think it will be in milleamps.

Which means then that the VSR should be connected to the switched side of the isolators then, not the battery side as the OP shows at the moment?


The spec below thanks to a bit of YBW time warp is presumably for the Blue Seas ACR
15mA consumption in the open state. Could be significant over a long period.

 

[mitiempo]

VicS
I guess it depends which VSR is being used. The Blue Seas ACR draws a small amount, more when closed than when open.

poetvasgo
The revised wiring sounds good to me. I agree the fuses should be close to the battery.Good plan to find where the wires go to from the Lucas relay. In wiring close doesn't work.

 

[davidej]

Which means then that the VSR should be connected to the switched side of the isolators then, not the battery side as the OP shows at the moment?
.

As I understand it the sensing side of the VSR should be fitted to the switched side of the motor isolator and the other to the unswitched side of the domestic - I assume to charge the domestic even if it is switched off.

 

[VicS]

The only problem with wiring the VSR to the switched side is when he installs an AC charger

Good point, unless he uses a charger with two independent outputs.

Time warp strikes a again

 

[mitiempo]

VicS
The only problem with wiring the VSR to the switched side is when he installs an AC charger he'd want the switches on for charging both banks. I favor the Xantrex Echocharge which does the same job with no electrical draw. It is a bit more expensive over here though than an ACR (VSR).

 

[VicS]

I'll Try to get my comments in the right place

The only problem with wiring the VSR to the switched side is when he installs an AC charger

Good point, unless he uses a charger with two independent outputs.

Time warp strikes a again

 

[Stu Jackson]

The one point I still fail to understand is why there remains an insistence to have the alternator output go to the engine bank instead of the house bank. The engine or reserve bank, regardless of whether it is used all the time to start the engine, or if the house bank is used, is almost ALWAYS FULL. The house bank, OTOH, after a night on the hook or on the boat at a marina without shorepower, always needs the lager amount of charge.

So why run all the current through the relay when the alternator output charge wants and needs to go to the house bank?

Whether using two switches or a simple 1-2-B switch (which will do the same thing BTW), the most important feature of any system should be to be able to run LIMITED house loads (like a VHF and navigation light) from the engine bank just in case the house bank dies, and do it without rewiring or jumpering.

An argument was made that once the alternator starts it will charge the house bank. But if the house bank is truly dead (dead cells, small bank, whatever the reason) even alternator charging won't help the house bank, and the ONLY "live" bank is the reserve bank.

I do agree that separate switching does avoid the possible voltage drop and subsequent impact to electronics. Since my boat doesn't have a large electronics component, the 1-2-B switch, using the house bank for everything (and checking the reserve bank regularly by using it and checking the status with our Link 2000) works for us.

 

[VicS]

The one point I still fail to understand is why there remains an insistence to have the alternator output go to the engine bank instead of the house bank.

Normally one would hope that the engine start battery is pretty well charged so you can quickly replenish the juice used for starting, then within a very short time anyway the VSR will cut in and the house bank will be charging.

If the house bank has priority and is low it could be some time before the starter battery is topped up. The engine may not even run long enough for that to happen! Therefore make the starter battery the priority and then you know it's recharged. The short delay before the house battery is on charge is not important.

 

[halcyon]

The one point I still fail to understand is why there remains an insistence to have the alternator output go to the engine bank instead of the house bank.


most important feature of any system should be to be able to run LIMITED house loads (like a VHF and navigation light) from the engine bank just in case the house bank dies, and do it without rewiring or jumpering.

Why charge the engine battery, security of power for starting, only alternator failure stops charge, not effected by service loads, no re-wiring engines for production builder, no danger to OE warrantee. Starting of the engine battery maintains a clean power supply for electronics, avoids low voltage during cranking.

Critical power supply, for years we supplied production yards with a unit that allows equipment to draw power from both service or engine battery. So this is no issue, no problem, and all solid state.

A lot of this idea of charging the service battery, came from the " blow up your alternator with a 1, 2 both switch ", why did it blow alternators, does it it still blow an alternator ?

The problem was that a alternator generates watts, open circuit the output, you get no amps. But still have amps, so volts go through the roof, i.e. 400 volt, and blow the 50 volt rectifier diodes.

But in the mid / late 1970's Lucas ( and most other manufacturers ) fitted avalanche diodes, these limited the output voltage, so the diodes were not blown with an open circuit output.


Brian

 

[Stu Jackson]

A lot of this idea of charging the service battery, came from the " blow up your alternator with a 1, 2 both switch ", why did it blow alternators, does it it still blow an alternator ?

Thank you both for your explanations.

I do believe that the issue you mention in the quote above simply had to do with the fact that boat manufacturers took the cheapest way out when they built boats by wiring only one wire between the alternator and the C post of the 1-2-B switches, with the small wire between the alternator output and the starter solenoid. This single wire ended up running power in two directions: for engine starting that one one wire went FROM the switch TO the solenoid, and then, once the engine started, FROM the AO back to the C post on the switch and then batteries bsed on what position the switch was in. Because of the lack of understanding by owners as to just HOW the "system" worked, and how batteries got charged by using the 1-2-B switch as the "gate", problems ensued.

That is why the simplest and best thing to do for your electrical system and alternator is to MOVE the AO off the switch, OF ANY KIND, and run it directly to the bank(s). The choice of how to charge the second bank has multiple answers. I've chosen the existing 1-2-B switch because I don't have "fancy" electronics. I can also use the B switch position for charge my reserve bank if my relay (combiner) ever fails. Others I have worked with have used separate switching and relays.

I have chosen to run my AO to my house bank because the wiring on my 1998 combiner is relatively small compared to the #2 AWG AO wire. The installation manual for that West Marine combiner also said to do it that way. The small amount of current required to replenish the reserve bank does not require the large wires.

If, however, your relay wiring is sized for the full house draw for a depleted house bank, then your suggestions make sense to me, although it does require larger wiring between the banks and the relay. Thus, the direction of flow is immaterial.

The original and persistent problem was NOT the 1-2-B switch, it was where the AO was landed. In fact, I'd bet most new boats today still come with that ridiculous arrangement. "When will they ever learn?" Switching of any kind of the AO is a recipe for disaster.

And last week or so there was the discussion of "live wires" if the AO was run to the bank(s). The answer above about the diodes in alternators seems to have answered that one.

Thanks again.

 

[VicS]

do with the fact that boat manufacturers took the cheapest way out when they built boats

In may cases probably more basic than you suggest.

The engines are likey to come as a package, complete with control panel, all pre-wired with the alternator output connected to the main battery lead at the starter solenoid.

All that is then required is a positive and a negative connection to the battery via the isolating switch.

 

[portvasgo]

Halcyon quoted
‘may I say the diagram is a very complicated way to solve a simple problem, but I will leave you to it.’

Please don’t leave me to it! I thought I had simplified the system. If you have the time, I would be very interested in simplifications! My main thoughts when coming up with the new schematic was to try and follow the very good advice from posters. And to also try and make it as easy as possible in the practical sense of rearranging stuff on the boat itself. Any help on simplification I would indeed value.
And davidej I was trying to follow you recommendations, but must have lost the thread somewhere. Will be happy to be put right, as I said to Halcyon, I’m on here to be corrected and to be led in the right direction. What’s non-standard on my diagram? Thanks for your help.

I was also curious by the battery drain from the VSR. The following link shows different connections for the dual sensing VSR as compared to the single sensing VSR.
http://www.bepmarine.com/store/web/.../Battery Charging/VSRs/Docs/710-125A_Inst.pdf

Does the fact that I have a solar panel trickle charging negate the worry of the small draw from the VSR?

 

[VicS]

Does the fact that I have a solar panel trickle charging negate the worry of the small draw from the VSR

The solar panel should more than offset the small consumption by the VSR unless you are fitting a very small one.

You would do well to adopt the wiring scheme in your link.

 

[mitiempo]

portvasgo
I find most questions on this and other forums receive answers that don't always agree. Wiring seems to be one of the more contensious subjects.
Some prefer the original dollar saving wiring by the builder and others like myself and Stu have found from experience and trial and error better ways (as have others). There is no "right way" to wire a system with only 1 battery even. But there are better ways and that is what I have tried to suggest. Your system looks fine as planned, save for the unexplained relay.
As far as the VSR I notice that the suggested wiring has the single sensing relay wired to the switched side of the start battery while the dual sensing is wired to unswitched for both banks. They state the continuous draw at .01 amps which is pretty small. Roughly 1 amp each 4 days. I'm not sure which side the dual sensing VSR is pulling this small draw from but the single sensing pulls it from the house bank as that is all it is constantly connected to. As I stated the Xantrex Echocharge doesn't have such a draw and would work also. For a boat plugged in to the mains and with an AC charger this is never an issue but without this a boat used less often could end up with the house battery down a bit after a number of weeks or months of being inactive.

 

[mitiempo]

I agree with VicS. Even the smallest panel should give you 1 AH every 4 days.

 

[VicS]

the single sensing pulls it from the house bank as that is all it is constantly connected to

Surely no. The single sensing one is only sensing the engine/start battery side. The connection to the house bank is only an output delivering current to the house bank when the relay closes.

 

[mitiempo]

They state that the sense circuit draws .01 amps continuously. They don't differentiate between single or dual sensing but I read it as both.

 

[VicS]

state that the sense circuit draws .01 amps continuously

but the single sensing one is sensing the volts at the alternator output/ start battery. It is sensing that so that when the volts there rises to 13.7 the relay closes. It does not care what the volts are on the house bank.