PaulRainbow
Well-Known Member
Richards description is that of a solenoid/relay connected to the alternator D+, as used to be used on caravans and the like in the olde days.
1/2/Both switch bust?
- Thread starter richardabeattie
- Start date
Richards description is that of a solenoid/relay connected to the alternator D+, as used to be used on caravans and the like in the olde days.
VicS
Well-Known Member
PaulRainbow
Well-Known Member
pvb
Well-Known Member
I doubt that there'll ever be a consensus on the best way of configuring a 2 battery system.
Many people favour the 1-2-Both switch; I don't, simply because it introduces the chance of things going wrong if the switch is set incorrectly. The chance of the batteries getting discharged so that the engine can't be started. And then it's a call to the RAC, sorry RNLI, to rescue you. OK, people say that "only the skipper can touch the switch", but what if the skipper gets it wrong? Or what if the skipper is indisposed, and a well-meaning crew member sets it wrongly? It's simply an unnecessary risk, when there are fail-safe solutions.
The best solution, in my mind, is to have two separate on/off switches - one for the engine battery, one for the domestic battery/ies. This then requires some way of charging them without letting one battery discharge into another. So it needs a VSR, or a diode splitter, or best of all a low-loss splitter. Then it's just plain sailing! Arrive at the boat, turn the engine and domestic switches on, use the boat as much or as little as you desire, then turn both switches off and go home. There's nothing else to do; no messing around changing the switch every so often, no chance of things going pear-shaped. No need to call the RAC, sorry RNLI. I admit it's not traditional, but tradition isn't necessarily the best solution.
RichardS
N/A
I've never seen that web page before but that circuit is exactly the same as mine so you are spot on Vic.
It's strange that they call it a relay though. I've replaced both the "relays" recently as one had failed and the other was developing the voltage drop mentioned in the article. However, they both lasted around 4000 hours so I can't complain and they less than £20 each.
These are the ones that were fitted to me boat and I have replaced them with identical ones: https://www.motoelectrical.co.uk/ty...oid-spl6008-clarke-case-ford-delco-equipment/ but they are always called solenoids rather than relays. I've no idea which is the proper term in this context.
Richard
PaulRainbow
Well-Known Member
The lines between "relay" and "solenoid" are a bit blurry these days. They often serve the same purpose, but not always. In the case of a starter solenoid (pre-engaged) it will engage the pinion, then activate the motor, a relay cannot do that. A relay is an electrically operated switch.
VicS
Well-Known Member
The webpage is part of Tony Brooks' " Boat electrical notes" which may interest you if your electrical knowledge is limited. It is all very basic though and hardly a degree course.
http://www.tb-training.co.uk/
I expected something like the Lucas split charge relay but that is rated at only 60 amps which wont be enough with a more powerful alternator
http://www.autoelectricalspares.co.uk/lucas-srb630-33441-33ra-12v-60a-split-charge-relay-1583-p.asp
The difference between a relay and a solenoid is I think that a relay is wound on a fixed core and operates the ( relatively light) switch contacts via a moving armature whereas a solenoid has a moving iron core which operates the ( heavier duty) switch contacts or some other mechanical device such as a valve. I'm not an electrical engineer though so may be wrong!
PaulRainbow
Well-Known Member
That's as good a description as i've seen Vic :encouragement:
RichardS
N/A
Yes, that sounds like a good distinction Vic .... and explains why relays "click" and solenoids "clonk".
Richard
rogerthebodger
Well-Known Member
Yes, that sounds like a good distinction Vic .... and explains why relays "click" and solenoids "clonk".
Richard
Just to confuse matters even mote there are electrical contactors that are heavy current electrical relays that generally operate in the same way as a solenoid.
A Solenoid is in fact only the mechanical part of a contactor and a solenoid is also used where only mechanical movement is needed as in the case of a pneumatic valve or fuel cutoff of the mechanical injector pumps on newer engines.
in the case of a starter solenoid there is both mechanical movement of the bendix and the electrical connection of the heavy current contactor.
In the older type of petrol engines with a inertia engage bender the solenoid the power to the motor was in later cars through a heavy current relay / contactor or in the case of my old A35 a mechanical pull contactor.
