Swapping a 1,2,both switch to a split charge relay..

[casper ghost]

I'm pretty sure my, 1, both, 2, off, battery switch is messing about.. When selecting 1 or 2, which is starter battery and domestic batteries respectively, the electric goes off.. The only way to get power through the switch is to select "both". This switch used to work fine and i've changed nothing, it just seems to be messing about.

I haven't looked in the switch yet, but my Dad is nagging me to fit a relay to do the split charging, as seems to be the consensus in most threads on the topic.

So, can anyone recommend a relay? I have 2 110 ah domestic batteries and 1 starter battery. The alternator is a 75amp, run off the flywheel, so spins fairly fast. I also have a 40 watt solar panel, currently connected, through a fuse, directly to the domestic batteries.

Thanks.

Casp'

[Robbo]

Note, You'll still need a isolation switch with a relay.

[casper ghost]

Note, You'll still need a isolation switch with a relay.

I have one of those isolation switches near the batteries on the negative cable, and then a 1,2, both and off switch too.

Casp'

[Tonka]

Fit a new switch

[Kae]

VSR - voltage sensing relay

[jonathanA]

there's a lot of debate about so called 'heavy duty' relays, I bought a 180A one from CPC for just over £20. http://cpc.farnell.com/jsp/search/productdetail.jsp?sku=CP02901

 

 

I'm not really convinced it would handle a 180A as a sustained load but for connecting my domestic and starter battery together it works just fine. - no fancy electronics, idiot proof if the engine is running the batteries are charging, no need to remember to do anything.

 

all you need to do is connect one side of the relay coil to the d+ or ind terminal of the alternator and the other to a -ve. the big terminals go to a nice chunky wire (25mm² at least) either between battery banks(connecting +ve's) or between the alternator B+ and the domestic +ve. you still need an isolator between the domesitic +ve and the main/distribution board for the 12v stuff.

 

once the charge indicator light goes out the relay operates coupling the battery banks so both starter/domestics are charging from your alt.

 

job done fit and forget.

[Tony Brooks]

Just to point out that it will probably require some rewiring involving battery size cables and also the main charging lead. If you want to avoid short reelay life the main charging lead should go direct to the DOMESTIC bank and the relay be used to connect that bank to the engine battery.

[alan_fincher]

Personally I would just replace the switch, which will probably be easier / cheaper than getting everything right for a relay based alternative. They are not that expensive.

[Tony Brooks]

Personally I would just replace the switch, which will probably be easier / cheaper than getting everything right for a relay based alternative. They are not that expensive.

 

I think I would tend to agree, especially as the OP must have got used to the regime involved. I don't like the things - too much chance of a break before make when they get old and thus possibly wrecking the alternator - but certainly the easiest way.

[casper ghost]

Thanks all. Must admit, I didn't realise I would have to move it and use battery size cable, although I do have some. The switch I currently have, retails at about £23. I'll have to think what I want to do.

Casp'

[smileypete]

For a split charge relay, the usual ones often aren't that 'boater proof', but Albright do decent 12V contactors:

 

http://www.thetoolboxshop.com/sw180b-2-albright-single-acting-solenoid-contactor-12v-continuous-6642.html

http://www.thetoolboxshop.com/sw60-1-albright-12v-dc-single-acting-miniature-solenoid-contactor-intermittent-80a-6946.html

 

cheers, Pete.

~smpt~

[NMEA]

Duplicate post deleted.

Edited September 27, 2014 by NMEA

[NMEA]

Thanks all. Must admit, I didn't realise I would have to move it and use battery size cable, although I do have some. The switch I currently have, retails at about £23. I'll have to think what I want to do.

Casp'

False economy, if its what you are accustomed to you can buy a quality Blue Seas 4 position switch for about £40, high quality, made using the right materials and will last and be reliable.

[casper ghost]

False economy, if its what you are accustomed to you can buy a quality Blue Seas 4 position switch for about £40, high quality, made using the right materials and will last and be reliable.

Looks interesting, certainly looks more robust than the one I currently have, shame it's red! They do a black one but it seems to be far more expensive..

 

Seems, you can get them from the USA, inc p&p and fees, for about £26, and yet they seem to be about £40 from the UK, as you said..

Casp'

 

My mistake, seems import charges are a further £8..

Edited September 27, 2014 by casper ghost

[NMEA]

Looks interesting, certainly looks more robust than the one I currently have, shame it's red! They do a black one but it seems to be far more expensive..

Casp'

The black ones are more heavy duty and will handle a constant 600a which is why they are higher cost, the red ones handle a constant 300a or 350a depending on the model.

Actually after checking my Blue Seas catalogue the 300a 4 position is available in black to special order, part # 6007200

Edited September 27, 2014 by NMEA

[Bee]

I fitted a 1,2, both out of choice when I built mine, simple, reliable. reasonably foolproof. 'Make before break' is important though otherwise alternator is vulnerable to a disconnect and hence damage whilst running.

[Tonka]

Having had a split charge relay stick so as the starter battery went flat (first nb) and a blocking diode catch fire (second nb). A switch is safer

[Tony Brooks]

Having had a split charge relay stick so as the starter battery went flat (first nb) and a blocking diode catch fire (second nb). A switch is safer

 

Fine, wait until the track or a wiper fails and then you are likely to blow the alternator as you switch.

 

Trouble is people do not RTFM so we get split charge relays wired so they HAVE to carry all the domestic charging current rather than the few amps for a short time required by the start battery. They fail to read that most diode's current rating is "in a cool airflow of not less than xx m/sec. They also fail to ensure the terminals are clean and tight.

 

Any device will eventually fail and it will fail more quickly if it is not installed and maintained properly. I do not see how sensible advice can be given based on just two incidents over an unknown time period with no information with which to diagnose the failure. Anything that relies upon human intervention is subject to extra chances of failure. This is why most of those with extensive experience recommend some form of split charge relay or Zero voltdrop diode. Also when they fail they are unlike to take the alternator with them.

[casper ghost]

As an update I did just fit a new switch, a Blue Sea one as recommended in this thread. I took apart the old switch, but couldn't see anything in it that looked wrong, so not sure why it didn't work? Anyway, the new switch works fine. One thing I always make sure is that I never move the switch when the engine is running, I also never put the switch in the off position.

Casp'

Edited October 26, 2014 by casper ghost

[floatsyourboat]

Does anyone have a picture of how these relays are wired up please as I've bought a 120amp relay but my mechanic friend said its only for split charging one battery/alternator.

[bottle]

What do you want to be able to do?

 

Do you have two alternators?

[floatsyourboat]

What do you want to be able to do? Do you have two alternators?

Hi I have two alternators one wired to the starter and one wired to 4 x 110 amp batteries I want to split charge. Edited October 29, 2014 by floatsyourboat

[bottle]

I do not think there is 'simple solution' with two alternators and two battery banks.

 

Post 559 in this thread may help you, in what you want to do.

 

http://www.canalworld.net/forums/index.php?showtopic=21827&page=1

 

It is a long time ago and some of the best brains that were on here at the time had a long discussion and a lot of chaff is in there as well.

 

good luck.

Edited October 29, 2014 by bottle

[Tony Brooks]

Hi I have two alternators one wired to the starter and one wired to 4 x 110 amp batteries I want to split charge.

 

???

 

The charge is already split or do you want to split one of the alternator' output to charge an undisclosed battery bank? Or maybe you intend something different.

[jonathanA]

you already have a 'split' system in that you have two alternators charging separate banks (by the sound of it). so is what you actually want to do is 'parallel' your alternators so your domestics make use of the usually under utilised starter alternator as well ?- in which case your relay will do that - see post #12 in the thread bottle linked to.

Edited October 29, 2014 by jonathanA