Split Charge Rely

[plainsman]

Having read a lot about poor, weak and generally useless relays with a tendancy to burn out quickly, which make/type can be recommended? In my case I have an engine battery and three 110 domestics. These are presently controlled through a blocking diode with the associated voltage drop of about 1v.

 

Alex

[Guest]

I got one off this company. No problems after four years of hard work.

 

http://213.143.4.21/contactors.htm

 

Specifically this one:

 

http://www.intellitec.com/PDF/5300629.120.pdf

 

ps don't advise the black 180Amp ones (d*r*te) found often in chandlers. I have changed a few that had simply melted.

Edited October 19, 2008 by Guest

[John Orentas]

Hi Alex.

 

A relay is a relay the important thing is that you need a current capacity on the average boat of around 80 amps and of course they must have 12 volt continuous rated coils.. In my case I used two relays in parallel each with two changeover contacts of 20 amp capacity.. I know very well the arguments against this, that one contact will close before the others and all that but in fact the relays rarely open and close 'on-load'.

 

My system worked perfectly for the best part of 20 years, each relay cast about a fiver.

 

P. M. me for a circuit drawing.

 

P.S. Don't be tempted to use an automotive starter relay, they are not continuously rated.

Edited October 19, 2008 by John Orentas

[n.b.Goldie]

Having read a lot about poor, weak and generally useless relays with a tendancy to burn out quickly, which make/type can be recommended? In my case I have an engine battery and three 110 domestics. These are presently controlled through a blocking diode with the associated voltage drop of about 1v.

 

Alex

 

Having had nothing but grief with split charge relays I junked mine and went for a Sterling Power Products Alternator to Battery Charger. Extremely easy to fit and totally transformed the system. Charges in a couple of hours and now got more power than i know what to do with.

 

A major problem with split charge relays is that although they can handle the power of the alternator say 70amps or so, if it shorts the other way 330 amps tends to melt them very quickly with the associated risk of fire! Of course a blocking diode overcomes this but a standard alternator will not bring the batts up to their full potential unless there is some form of alternator controller used.

[Guest]

Having had nothing but grief with split charge relays I junked mine and went for a Sterling Power Products Alternator to Battery Charger. Extremely easy to fit and totally transformed the system. Charges in a couple of hours and now got more power than i know what to do with.

 

A major problem with split charge relays is that although they can handle the power of the alternator say 70amps or so, if it shorts the other way 330 amps tends to melt them very quickly with the associated risk of fire! Of course a blocking diode overcomes this but a standard alternator will not bring the batts up to their full potential unless there is some form of alternator controller used.

Sorry but that is urban legend. Quite simply; a good relay will cope with all this and more without combusting, a poor one won't.

 

If you don't believe me, perhaps you will believe somebody who has dedicated many years to battery charging technology:

 

http://www.smartgauge.co.uk/choosesb2.html

 

http://www.smartgauge.co.uk/more_relay.html

Edited October 19, 2008 by Guest

[n.b.Goldie]

Sorry but that is urban legend. Quite simply; a good relay will cope with all this and more without combusting, a poor one won't.

 

If you don't believe me, perhaps you will believe somebody who has dedicated many years to battery charging technology:

 

http://www.smartgauge.co.uk/choosesb2.html

 

http://www.smartgauge.co.uk/more_relay.html

I wonder how many boats are chugging around with poor ones?

[Guest]

I wonder how many boats are chugging around with poor ones?

There are loads of boats with the dreaded black 180 amp relay used, simlpy because they are cheap, and the chandlers always sell them. To be fair, I think it was "Snibble" who claimed that they were OK if one changed the spring washers for a different type, but I haven't tried this yet. Believe me, I have changed loads for stricken boaters. They generally melt at the base, causing the contact pillar to lean, and lose contact. If a good quality relay is used with a 200 amp rating ontinuous, and a 1000 amp surge, then there is no problem. That is what I have, and it has worked very hard indeed. I burned a couple of the popular black 180A ones out.

 

[Nickhlx]

It seems that the Intellitec, the Sterling and the Smartgauge ones may be the same - they all appear to claim 200 Amps continuous and 1000 or 1200 amps for less than 30 seconds, so should be entirely capable with most narrowboat charging systems.

 

The Intellitec one is latching so power is only drawn to change state ( a few amps) so this would be least likely to melt.

The others may be as well but didn't see that in the specs.

 

Nick

[1066]

I burned a couple of the popular black 180A ones out.

 

What would you recommend as an acceptable readily available [uK] relay?

 

I know the Smartgauge unit is mentioned, but are there any others?

Edited October 19, 2008 by 1066

[Guest]

What would you recommend as an acceptable readily available [uK] relay?

 

I know the Smartgauge unit is mentioned, but are there any others?

As somebody else siad, Smartgauge (Gibbo) and Intellitech could be the same item,but they all sell them. Vehicle Wiring Products used to sell a hefty one too. I have been very pleased with the Intellitech, but I think others are probably as good. Ihave heard of people putting two Durite 180 in parallel(as John suggested earlier). I know one company, whos name escapes me, modifies the Durite 180 with a delay circuit, and advise using two in parallel for large battery banksl. There are theories about this as John points out, but paralleling relays is not uncommon in practice.

[chris w]

Hi Alex.

 

A relay is a relay............................

 

Nope. Two "identical" relays (in terms of current capacity) can employ very different contact materials in their construction and so have very different applications.

 

see (for example) here

[John Orentas]

The usual problem with the "180 amp rated types" is not the contacts or any problem with the switching, it is the coil or primary circuit which is not continuously rated, they were probably originally designed for an entirely different purpose probably for a very momentary application to do with a starter circuit, but they will overheat and fail if energised for more than a minute or so.

[chris w]

The usual problem with the "180 amp rated types" is not the contacts or any problem with the switching, it is the coil or primary circuit which is not continuously rated, they were probably originally designed for an entirely different purpose probably for a very momentary application to do with a starter circuit, but they will overheat and fail if energised for more than a minute or so.

 

 

You are incorrect yet again JO. Just do the maths..........

 

A typical coil will have a resistance of about 120 ohms, so will be dissipating around 1 watt.

 

However, suppose the contacts are carrying 80 amps and, through pitting, have a resistance of just 0.1 ohms. The contacts will be dissipating 80² x 0.1 = 640 WATTS!!!!!!! Even if the resistance is only 0.01 ohms (100 milliohms) that's still 64 WATTS!!!!!!!!!!!! See what I mean?

 

Do you still say it's the coil circuit causing the problem?

 

Chris

[John Orentas]

You are incorrect yet again JO. Just do the maths..........

 

A typical coil will have a resistance of about 120 ohms, so will be dissipating around 1 watt.

 

However, suppose the contacts are carrying 80 amps and, through pitting, have a resistance of just 0.1 ohms. The contacts will be dissipating 80² x 0.1 = 640 WATTS!!!!!!! Even if the resistance is only 0.01 ohms (100 milliohms) that's still 64 WATTS!!!!!!!!!!!! See what I mean?

 

Do you still say it's the coil circuit causing the problem?

 

Chris

 

 

It is the coil circuit that exerts the contact pressure and in the application we are talking about it must do it for hours on end.

[chris w]

It is the coil circuit that exerts the contact pressure and in the application we are talking about it must do it for hours on end.

 

Even if it did it for eternity , the coil is still only dissipating 1 watt. It's NOT the coil circuit causing the problem!

[n.b.Goldie]

Sorry but that is urban legend. Quite simply; a good relay will cope with all this and more without combusting, a poor one won't.

 

If you don't believe me, perhaps you will believe somebody who has dedicated many years to battery charging technology:

 

http://www.smartgauge.co.uk/choosesb2.html

 

http://www.smartgauge.co.uk/more_relay.html

Had a look at the websites - interesting.................... I am sure it does what is says on the box but the box seems to contain mechanical relays. Hmmmmm...... a few thoughts occur to me:

 

* not sure how it can be urban legend when you admit to having replaced relays that have melted. If it gets hot enough to melt there must be a fire risk.

 

* anything mechanical must be subject to wear and tear - arcing of the contacts on make-and-break

 

* took the cover off my sterling digital charger unit - no mechanical relays but quite a few microchips and a blocking diode

 

* took the cover off my computer - no mechanical relays just lots of microchips

 

* British Telecom seem to have junked mechanically switched (strouger) exchanges in favour of digital

 

* my flat screen tv and dvd player does'nt contain any mechanical relays

 

* even the cheapest cheap-as-chips digital watch is more accurate than the most expensive mechanical watch. Just ask the swiss - digital nearly did for them

 

Digital seems the way forward! - on the other hand......................

 

when a renegade soviet pilot flew a foxbat into japan the american technicians fell about laughing when they inspected the machines' low-tech avionics. Until they realised that in the event of a nuclear exchange any surviving american microchip based avionics would cease to work but any surviving low-tech soviet avionics would continue to function.

 

However this was not enough to persuade the americans to abandon digital!

 

So what does all this mean? In the event of a nuclear exchange those of us with digital charger units will pretty soon have flat batteries but those of us who have stuck with old technology will be assured of fully charged batteries during the nuclear winter that will follow!!!

 

I think i am going to lie down for a while now.................... anyway it is almost time for my landlady to pour me a beer and give me an indian head massage - its all in the rent you know!

[Guest]

Had a look at the websites - interesting.................... I am sure it does what is says on the box but the box seems to contain mechanical relays. Hmmmmm...... a few thoughts occur to me:

 

* not sure how it can be urban legend when you admit to having replaced relays that have melted. If it gets hot enough to melt there must be a fire risk.

 

* anything mechanical must be subject to wear and tear - arcing of the contacts on make-and-break

 

* took the cover off my sterling digital charger unit - no mechanical relays but quite a few microchips and a blocking diode

 

* took the cover off my computer - no mechanical relays just lots of microchips

 

* British Telecom seem to have junked mechanically switched (strouger) exchanges in favour of digital

 

* my flat screen tv and dvd player does'nt contain any mechanical relays

 

* even the cheapest cheap-as-chips digital watch is more accurate than the most expensive mechanical watch. Just ask the swiss - digital nearly did for them

 

Digital seems the way forward! - on the other hand......................

 

when a renegade soviet pilot flew a foxbat into japan the american technicians fell about laughing when they inspected the machines' low-tech avionics. Until they realised that in the event of a nuclear exchange any surviving american microchip based avionics would cease to work but any surviving low-tech soviet avionics would continue to function.

 

However this was not enough to persuade the americans to abandon digital!

 

So what does all this mean? In the event of a nuclear exchange those of us with digital charger units will pretty soon have flat batteries but those of us who have stuck with old technology will be assured of fully charged batteries during the nuclear winter that will follow!!!

 

I think i am going to lie down for a while now.................... anyway it is almost time for my landlady to pour me a beer and give me an indian head massage - its all in the rent you know!

I repeat from my original reply:

 

" Quite simply; a good relay will cope with all this and more without combusting, a poor one won't."

 

It is not good relays that are the problem, it is poor relays that are vastly overrated (current wise, not popularity!). I have never said anything different. (quality) Relays have been used for many years for several good reasons. It is poor relays that have given rise to the legend that "relays are dangerous and catch fire," plus of course the sales pitch of an infamous digital regulator manufacturers website. Then again he would rubbish relays wouldn't he when he can make a couple of hundred quid turnover?

Nobody on this or any other site will convince me any differently.

[John Orentas]

Relays and contactors have been in use since the time of Michael Faraday, why anyone should imagine that they habitually burst into flames like an American car in a cheap film is beyond me (some half-wit is about to say that lots of things are beyond me)..

 

They have been produced in their millions for the best part of a century and I for one have never witnessed one even getting warm when used correctly, why should they, it is a fantasy.

 

Some of this rubbish probably stems from the time when an engine manufacturer would throw into the packing case a cheap automotive relay, originally designed for powering a pair of fog lights on an Austin Cambridge, even now chandlers still stock those cheap little pretty coloured things and call the split charge relays.. Even that absurd name is a misnomer, I wonder who came up with that.

Edited October 20, 2008 by John Orentas

[Guest]

Relays and contactors have been in use since the time of Michael Faraday, why anyone should imagine that they habitually burst into flames like an American car in a cheap film is beyond me (some half-wit is about to say that lots of things are beyond me)..

 

They have been produced in their millions for the best part of a century and I for one have never witnessed one even getting warm when used correctly, why should they, it is a fantasy.

 

Some of this rubbish probably stems from the time when an engine manufacturer would throw into the packing case a cheap automotive relay, originally designed for powering a pair of fog lights on an Austin Cambridge, even now chandlers still stock those cheap little pretty coloured things and call the split charge relays.. Even that absurd name is a misnomer, I wonder who came up with that.

Lots of things are beyond you John Sorry, couldn't resist; I don't even qualify as a half-wit

As you say, a relay that is fit for purpose will give many years of good service. Compared to motor starting etc, a relay used for split charging has a fairly easy life. My particular relay is well capable of jump starting the engine from the domestic bank with a surge capability of 1000A. I see some quarters have now changed their tune about relay dangers, and now state that it is the INVERTER that may cause the relay to burst into flames rather than starting! Well guess what, a decent relay will piss it. Urban legends, I love them.