smartcom relay

[martino]

Hi there,
I recently fitted a smartcom split charge relay,the type that senses voltage and switches charge from van battery to leisure battery when the former is charged.
(As I understand it).I left it unconnected to the leisure battery to test it,and found,after driving for about half an hour,and with the engine still running,that about 2.5 volts was coming through.Is that right? After a few days use of the van,without using the leisure battery,I found it had lost voltage a little,from 2.7 volts to 2.6.Any ideas ?

 

[n brown]

2.5 volts ? not sure that a smartcom will operate unless wired to both batteries ,so connect it to the leisure battery then test it.
don't forget it may take a few seconds for the relay to switch,but you can hear it when it does.it usually takes a little while to click off after turning off the engine

 

[st3v3]

It won't need the other battery connected to turn on - it has two small relays inside. One switches the output to the fridge and the other the feed to the second battery.

How are you measuring the 2.5V? Or do you just have a broken '1' on your keyboard lol.

 

[martino]

It won't need the other battery connected to turn on - it has two small relays inside. One switches the output to the fridge and the other the feed to the second battery.

How are you measuring the 2.5V? Or do you just have a broken '1' on your keyboard lol.

Measured across the leisure battery terminals ( disconnected) with a multimeter.Engine running,having been so for forty mins or so,relay connected to van battery as wiring diagram.Is that clear?

 

[n brown]

ah. you mean the LB is disconnected from the habitation circuit,but connected to the vehicle battery[VB] ?
this 2.5v is the mystery ! nothing should read that low .what reading do you get at the connections on the smartcom from the VB ?

 

[martino]

ah. you mean the LB is disconnected from the habitation circuit,but connected to the vehicle battery[VB] ?
this 2.5v is the mystery ! nothing should read that low .what reading do you get at the connections on the smartcom from the VB ?

That's right.just to be clear,the current coming through from the relay is 2.5v. I have just read my original post again and realize that there was a mistake there..sorry! The reading off the lb is dropping from 12.7 to 12.6.the reading from the relay is 2.5.

 

[n brown]

next thing i need to know is what voltage do you get at the LB when the engine is running ?.if you can,get someone to start the engine while you hold the relay and listen. there should be an audible click,if the engine's noisy you can feel it.if you don't get this then the relay may need adjusting.if you look in the end you'll see a small ound disc with a slot in the middle for a small screwdriver.turn this gently anti-clockwise to a stop- then,with the engine running turn it clockwise until you get the 'click' turn a little more and test the voltage at the LB it should be over 13v

 

[martino]

next thing i need to know is what voltage do you get at the LB when the engine is running ?.if you can,get someone to start the engine while you hold the relay and listen. there should be an audible click,if the engine's noisy you can feel it.if you don't get this then the relay may need adjusting.if you look in the end you'll see a small ound disc with a slot in the middle for a small screwdriver.turn this gently anti-clockwise to a stop- then,with the engine running turn it clockwise until you get the 'click' turn a little more and test the voltage at the LB it should be over 13v

Thanks for that,and taking the time to explain.I will try your suggestion tomorrow,and report back.

 

[Donk]

We have a 1.3 Suzuki Carry Pick-up onto which we put a romahome demountable and once attached the electrics are connected via a trailer plug and socket.

When i leave the van parked (without the camper pod on) the battery goes flat if the van is not run for about 4 days.

Its a New battery, so could the smart relay drain the battery even though nothing is drawing power through it ?

 

[martino]

I have done as suggested,adjusting the screw on the relay,and now the meter reading on the lb creeps up whilst watching it, 12.5,then 12.51,12.52 etc.I hope the adjustment isn't taking charge from the van battery prematurely! Time will tell,will keep the jump leads handy.

 

[Deleted member 5816]

I always thought the Smartcom relays were designed for a Car and Caravan not for Motorhomes

Alf

 

[n brown]

I have done as suggested,adjusting the screw on the relay,and now the meter reading on the lb creeps up whilst watching it, 12.5,then 12.51,12.52 etc.I hope the adjustment isn't taking charge from the van battery prematurely! Time will tell,will keep the jump leads handy.

something still wrong here !
did you hear a click from the relay after the engine started?
if so the voltage should have gone to over 13v straight away,possibly 14v,which is what your alternator should be producing .
when you turn off the engine,after half a minute or so,there should be another click as the relay opens again

 

[n brown]

I always thought the Smartcom relays were designed for a Car and Caravan not for Motorhomes

Alf

don't know,but same thing surely ? the caravan would have a LB charged from the car. a better circuit would be to have the smartcom to open a heavier duty relay,100a,but of course this would mean using heavier cables and fuses

 

[maxi77]

don't know,but same thing surely ? the caravan would have a LB charged from the car. a better circuit would be to have the smartcom to open a heavier duty relay,100a,but of course this would mean using heavier cables and fuses

I would suggest this is the only way to use the very good smartcom relay for battery charging. The likely inrush current for a partly disharged is usually more than the 30 amp rating and I have seen Smartcom relays smoking when they close on a battery circuit. Even if the alternator is within the Smartcom limit the starter battery will dump power into the second battery untill the second battery voltage rises far enough to cut thed charging current.

 

[st3v3]

I would suggest this is the only way to use the very good smartcom relay for battery charging.

Agreed. And the rating of the individual relays is not 30A either - they are tiny. I forget what it was when I looked them up, may have even been 10A.

 

[Deleted member 5816]

Leisure Battery Charging

The Smartcom unit is complicated to wire as it is designed for a caravan system with inbuilt fridge relay it is far easier to use a 30A or larger relay and wire and use the alternator D+ to fire the relay this way the relay will only close when the engine is running.Use a second relay to supply the fridge 12v from the van battery.

Alf

 

[Donk]

We dont use it to power the fridge as 12v current dosent seem to get it very cold. !

We use Gas when wilding and 240v when on an EHU,

We only use the smart relay to charge the 2nd leisure battery inside the camper pod.

 

[n brown]

the reason for having a 12v element is not so much to cool the fridge,but to keep it cold ,while driving,after it has been cooled by EHU or gas. unless you only drive short distances,it's well worth having,especially when driving through southern europe in summer !

 

[st3v3]

The Smartcom unit is complicated to wire as it is designed for a caravan system with inbuilt fridge relay

Electrically, a camper is a car and caravan that doesn't get unplugged!

it is far easier to use a 30A or larger relay and wire and use the alternator D+ to fire the relay
Alf

I would disagree - sometimes it's difficult to pick up this feed, and on some newer stuff it doesn't exist at all! The smartcom is also good because it will allow a certain amount of priority to the engine battery if that's really low.

It's not difficult to wire - 1 input from the main battery and a ground. Then it has 2 outputs that will switch to 12V when it sees over approx. 13.5V on the input. You can do what you want with them.

 

[maxi77]

The Smartcom unit is complicated to wire as it is designed for a caravan system with inbuilt fridge relay it is far easier to use a 30A or larger relay and wire and use the alternator D+ to fire the relay this way the relay will only close when the engine is running.Use a second relay to supply the fridge 12v from the van battery.

Alf

Not really, many vehicles react badly to using that signal to operate relays, the Bongo for one. In the old days it was good but it will only work on some vehicles now. It is an easy way to switch big cheap relays though using a 70 or 100 amp VSR is moreelegant though often more costly.