Split charge intelligent relay update

[dandywarhol]

Here's an update to the recent discussions about Towsure's split charge realay.

I inadvertantly left on my hotbox after picking up a carryout on Sunday and ran the leisure battery down to almost nothing.

When I started the engine I could hear the split charge relay clicking in and out so I put on the interior light (wired to the 115 A/h leisure battery) to see what wa shappening.
The "intelligent" relay was protecting the circuit from overcharging and by doing so saved the 40A line fuse between the main and leisure battery from blowing.

The relay doesn't open it's circuit until the main battery has reached arouind 13.5 volts so the alternator first charges the partially discharged (through starting the engine) main traction battery, then tries to charge the heavily discharged leisure battery. It seems to realise the battery is very discharged and "pulse" charges it under 40 amps until it is stable enough to take a full charge - clever fella!!

BTW............it took nearly 12 hours to fully recharge the leisure battery from a mains charger to show fully 1.280 on a hydrometer! I thought the leisure discharged too quickly bit now I realise that it probably wasn't really fully charged from the alternator. The Auto Electrical lecturer at college reckoned that the alternator only really gives about 75/80% of charge and always best to mains charge every so often.

Sorry for the long windeed post - hope it helps to clear up any doubts/misunderstandings about these relays.

[madmile]

What sort of price is the towsure relay dandy. I struggled to find an auto switching relay for a sensible price and end up going for a towequip one. It is a 30amp relay and although I have not had trouble with this level I would be interested in getting one that is rated at more than 30A.
They certainly save the hassle of tapping into the alternator wire.

[dandywarhol]

This one at £11.75 madmile



It's had a slagging on here before but I find it just fine and dandy.
It's only rated at 30A but seems to cope with more..........

Towsure also do a "SMARTCOM" orange relay on the same part number but I've had one fail (which they replaced immediately, got the impression it wasn't the first!)

[madmile]

Exact same one as mine (although I havent tested to see if it would handle more than 30A). Obviously one of those items that gets packaged up by many companies.

[timhum]

Hi Dandy,
I have a Voltage Sensitive Relay like yours which switches in at 13.7 volts, it switches out again if the volts drop below 12.7 to avoid the clicking happening.
In the instructions it mentions the clicking you noticed and says it is to do with the alternator finding the load from the main battery and the nearly flat leisure battery too much, dropping the output volts below the 12.7 volt threshold, switching out, the volts go up again and so on until things stabilise eventually.
If this happens a lot, the relay will fail sooner rather than later due to the contacts wearing out (many cycles of many amps being switched).
They say possible remedies are increasing the size and/or shortening the cable to the relay contacts, getting a bigger alternator or choosing a smaller leisure battery. The last two are not applicable to us chaps but if we were equipping a fleet of ambulances or less Amp Hours were acceptable, they might be.
I guess if it only happens when the leisure battery is exceptionally flat it isn't an issue but if it happens frequently, I'd keep a spare handy!

I am shopping for a new battery at the moment and notice that the Elecsol website advises a top up charge from the mains for full performance, very honest of them to mention that I thought, the other battery manufacturers don't let on.

[dandywarhol]

Good info timhum................I've a 115 A/h leisure so what you're saying and I was guessing is right - best not to let the leisure drop too much........................less ASDA reheat curries in the microwave methinks - the 1200W invertor draws a fair bit from the battery

[madmile]

Quick question for Dandy - did you connect two input wires from your starter battery to 1+2 pins?. I thought the instructions were a little vague so havent bothered yet, but van has not been used since installation.

[dandywarhol]

Hmmmmmm........don't think so MM..........I'll look in the morning - it was nearly a year ago I did it and my brain's getting more fried by the day................

[dandywarhol]

I only fitted 1 cable from the main battery into the relay, one out to the leisure and one to earth.
I fitted the earth to the wiper motor bracket and double sided taped the relay behind the main fuse box away from heat/dust

[pistonbroke]

Just read your post and note that you are looking for a leisure battery. This month's Caravan Club mag has tested a number and recommend an Elecsol 90/110, rrp £93.

[vanvliet]

[quote="madmile"]What sort of price is the towsure relay dandy. I struggled to find an auto switching relay for a sensible price and end up going for a towequip one.

Bad news I am afraid .I ordered one of Dandy's green relays from Towsure They sent me - -yep - -an orange Smartcom one When i complained they said that they were no longer supplying the green one. So if you order from towsue or towequipe you will receive a Smartcom!

[madmile]

The green ones are also available from indespension trailer centres -approx £16.
Chatting to them earlier - they recon they fit thousands every year with no problems.

[vanvliet]

Thanks Madmile. I will get hold of one from indespension I treid to google the name of the company which makes them ( on the pic of the green relay in previous post) but could not get a website link