Split Charge Relays

Brian Kirby · October 25, 2010

If timetraveller is still reading this, it seems a better understanding of how he uses his van is essential before any proper advice can be given.

It would be helpful to know, in addition to his usual stays not exceeding two nights and being off hook-up, how long he usually drives the van between stops - and I think duration will be of greater help in this respect than distance. It would help to know whether these activities continue year round, or are seasonal, and at roughly what frequency they take place. It would help to know when the van is not in use, whether or not it is connected to mains. It would also help to have some idea what the 12V consumption is, or at least what the main consumers are. Is an inverter fitted to run 230V appliances: if so what is run, and what is/are the Wattage/s?

I agree that it is odd, with 170Ah of battery power available, that a generator is considered necessary for stops not generally exceeding 2 nights. With that battery capacity, and with reasonable management of consumption, I would have thought about a week off hook-up should be feasible.

As above, I doubt there would be any great benefit from the intelligent relay in replacing the standard split charge job, I too have wondered if the driving time is simply too short to replace what is progressively removed (and also wonder if it would be adequate even with a B2B charger), and I further wonder if the existing batteries (or one of them) are defective and incapable of holding their charge, or are mis-matched.

I should also be interested to know how the state of charge of the batteries is being monitored, because some of the standard kit installed by motorhome manufacturers is rudimentary, to say the least, in the level of detail it provides, and at what charge level timetraveller becomes anxious.

October 25, 2010

Brambles - 2010-10-25 10:10 AM
Manufactures fit fusible links, can be in the terminals themselves, built into the cables or a seperate fusable link cable. Whatever the cables are acually protected.

You will find many vehicles do not have fuses in the main cable from the battery to the starter motor.

Brambles - 2010-10-25 10:10 AM

Relay contacts can weld togther for a number of reasons. From sparking/arcing, mechanical failure of relay, or excessive currents, oxidation or burning from sparking causing high resistance so low currents will heat them up, or other faults which can occur in the relay circuit.

True, and many of them will not be prevented by fuses. But since the contacts sticking will only keep the main and leisure batteries permanently connected, the worst that is likely to happen is you will drain the main battery.

Brambles - 2010-10-25 10:10 AM
An alternator does not produce surplus current.

Surplus current is what is not being used to run the vehicle, so is available for battery charging.

Brambles - 2010-10-25 10:10 AM Typically the power taken to start an engine is very small and is under 1Ah of battery capacity. Ancilliary equipment standby power over 24 hours is greater and typical over 24 hours you could have a drain of up to 5 Ah. Not a lot to recharge and so voltage on main battery should rise rapidly and no delay is really exists or is worth worrying about.

Ancilliary equipment will be draining the main battery too. You can't know how drained the main battery will be. Thats why its an advantage having a voltage sensing relay to charge the main battery first.

....... (waffle removed)...

Brambles - 2010-10-25 10:10 AM
It is also desirabe to have some resistance in the leads supplying the leisure batteries which solves a multitude of other charging related and battery life issues.

What advantage could there be in having resistance in the leads supplying the leisure batteries? (apart from slowing down the charging of the leisure battery so you can sell them an expensive charger ;-) )

Brambles · October 25, 2010

Brambles - 2010-10-25 10:10 AM

Going to leave it at that, as really can't be bothered with this anymore and is just turning into an argument.

waffle reinstated.

(and I still stand by what I have posted)

one advantage is reduced peak currents when battery is flat which is not good for the battery and damaging to a gel battery.

October 25, 2010

Brambles - 2010-10-25 3:21 PM

waffle reinstated.

one advantage is reduced peak currents when battery is flat which is not good for the battery.

Peak charging current will have been set by the vehicle manufacturer for the main battery only. Its hardly likely to damage both batteries connected together.

Brambles · October 25, 2010

James, I have added a bit to my post which is not in your quote.

Oh heck, you do go on. The main battery is rarely flat, if it is the charging from the alternator at a high rate can damage it. Most manufacteres stopped using gel batteries for starter batteries because they could be charged at such a high rate damage resulted not just to the battery but also the alternator. AGM is more tolerant to high charge currents as permanent voids in the electrolyte cannot be formed.

The operation of an engine battery is quite different to a leisure. If an engine battery gets low enough for immediate fast charging from the alternator to be a problem then it will not start the engine. Jump starting will get the ball rolling again, but then you should idle the engine for 10 to 15 mins before driving off to save damaging the battery or the alternator.

Brian Kirby · October 25, 2010

Peter, in the nicest possible way, I don't think you are helping the OP very much. He has a motorhome. His motorhome has (big) leisure batteries. His leisure batteries get charged (albeit inadequately) so, ipso facto, his motorhome must already have some kind of charging regime, most probably - because that is what motorhome manufacturers generally fit - a split charging relay.

It is very difficult to see how merely changing one kind of split charging arrangement for another (albeit more sophisticated), will solve his problem.

If you look back to the original post there are numerous other factors, as yet unexplained, that would appear more relevant to the (apparently, though not yet confirmed) poor charge levels his batteries are achieving, than merely the relay, and it seems he may be labouring under some misunderstanding as to what the "intelligent" relay is/can do. Instead of getting heated with each other, might it not be more helpful to the OP for us collectively to try get to the bottom of his actual problem, before proposing possible remedies?

Sorry if this may seem rude, but I'm getting a bit fed up with the argument, that seems to be largely irrelevant, and to be going nowhere useful.

Timetraveller · October 26, 2010

Wow what a can of worms I seem to have opened up - so many answers & differences of opinion.

Okay let me try to put the records straight (hopefully!)

Yes we 'wild camp' all the time; we can be away from home for a number of weeks, sometimes over a month. Due to my having a chronic back problem our travelling time is limited, an hour to an hour & half tops. Consequently it takes time to get anywhere, but that's not a problem; we make it all part of our holidays & know many wonderful places to hide away. Sometimes we go for 'a walk in the motorhome'. This means meandering along at anything from 10 - 25 mph. I get to enjoy the countryside & we stop whenever we feel like it.

My concern has always been 'how long will our leisure batteries last without recharging?' We have a 1000 watt inverter to power up our 15" TV which is seldom used, perhaps for an odd sporting event or if we are following a particular programme. It certainly isn't on for more than two hours at a time. We have better things to see & do rather than be glued to the box.

We charge our phone, cameras & camcorder whilst travelling.

Our Seascape is fitted with an eberspecher heater & this is put on when we are feeling a bit cold. When temperature reaches around 21 degrees we turn the gauge down & it maintains a very comfortable temperature.

When it gets dark we will put on the rear strip light & at bedtime we use the individual reading lights.

At home the motorhome is usually permanently hooked up to our electrics & in winter (when at home) we put a small heater in to keep things aired.

We holiday throughout the year, spring, summer, autumn & winter. Since losing a very close friend we have adopted the philosophy that we only have one chance at living, so we do it to the fullest whilst I'm able. My condition isn't lifethreatening but neither of us is getting any younger so we are enjoying our motorhome whilst we can - then the kids can have it.

How do I measure what charge is left in my batteries? - by a rocker switch on a control panel. Not brilliant is my guess but it gives us an indication.

Initially we experienced very poor battery service, with it not holding it's charge - Avondale even sent one of their engineers to Darlington one winters night & still it lost it's charge. We added another battery ( two new ones) & things were not much better. It wasn't till we had eberspacher involved that things got better & we stayed warm & cosy!! Since then I've always been cautious, perhaps overly so. I purchased the generator as a 'belt & braces' job & have used it twice; not because the power was showing low but because we hadn't gone far in the past few days & no-one was around to disturb so I felt better using it for an hour to give the batteries a boost. But having read about intelligent battery chargers I thought that was the way to go. I did contact CTEK but their sales person said their chargers were 'mains chargers' so either I didn't explain things correctly or they got hold of the wrong end of the stick. I then Googled & came up with RAW Components who said they had a kit that would do the job; but I got 'cold feet' as I'd never heard of them!

Anyway many thanks for all your comments; I know it's costly but I may go back to CTEK again - unless you can convince me otherwise.

Sorry I'm not a technical whizz kid so hope my terminology hasn't offended

All I wanted is for us to stop worrying if our batteries :$

Brambles · October 26, 2010

Hi, absolutely great to read of your lifestyle around the motorhome and how you enjoy it. You get a lot out of the hobby and obvioulsy make the most of it you can emjoying life.

Anyway I think a few questions are needed to help with your problem of batteries discharging.

Am I correct in saying the Eberspacher(sp) heater was fitted at a later date after the discharging problem arose. The reason I ask is because they are quite heavy on power when being used. Someone else on the forums (Tracker) has one an with not too disimilar wildcamping finds his two batteries last about 3 or 4 days in winter. But he also has a solar panel to help boost. Guessing without looking up again but I think it must be an average of around 8 Amps the heater will be using. It draws a lot more , 20 Amps or so when starting up for the ignition cycle.

So to summarise question. Did problem exist before heater fitted, and did it get worse after heater was fitted. ( edit - hmm, guessing now is standard orignally fitted)

Next question, do you have a capacity problem 1st few nights after leaving home with batteries fully charged or is it something which gets progressively worse the more days you wild camp?

3rd question. If you leave everything switched off, do the batteries drain, I suppose seemingly all by themslelves just sitting there? In other words do you suspect something unknown is mysteriously draining them? I am wondering if your 1000-Watt invertor is permanently left connected as might have a very high standby current drain. It needs to be isolated from the 12 volt supply when not in use by its own or seperate switch.

Next question. Do you have a voltmeter or multimeter and know how to use. If not then it is worth buying yourself a cheap one. Almost a must to really be able to know what is going on with batteries as an accurate way to measure the voltage during charging and disharging.

How old are your batteries, make and model if you know?

Now some answers for you.

Forget the intelligent split charge relay.

Ctek, might be worth considering for keeping batteries charged at home rather than using on board charger.

So what make model is your on board power supply?

I need to go back and read your posts again to see what I might have missed.

Jon

edit - corrected typos etc.

October 26, 2010

Timetraveller - 2010-10-26 2:52 PM
RAW Components who said they had a kit that would do the job; but I got 'cold feet' as I'd never heard of them!

I got my voltage sensing relay and cabling from RAW components when I fitted out my new X250 van from scratch 14 months ago. Arrived next day, battery charges very quickly, never had a problem with them.

Not suggesting you should buy another relay if you have already got one though.

Timetraveller · October 26, 2010

Brambles,

Thanks for your quick reply & kind words - yes we do love our way of life & would reccommend it to anyone.

To answer your queries:

The eberspacher was already fitted when we purchased the van new; unfortunately Avondale had not fitted it correctly. We should have sensed something was amiss when we first saw it because the salesman couldn't get it to work & took us to another van to show us how efficient & quiet the heater was; stating that their electrical engineer would have the problem solved when we go to pick it up. It did work on pick up day but was not left on for more than a minute or so......fast forward - it never worked & drained our single 85amp battery very quickly, even though we were told we could leave it on all night if we wanted too!!! And YES they DID KNOW that we wild camped all the time. Eventually we fitted two new 85amp batteries to try & sort out the problem.......fast forward again - still did not work, so I got eberspacher & their local agent to sort it all out & bill Avondale.

2nd Question: Capacity problem; I can't say I have a capacity problem. It's more of a historical problem (see above) which I think still haunts me & I have no wish to spend any more freezing nights. Since eberspacher got involved we have had little problem (only habitation service engineer fitted something incorrectly last year - quickly sorted by eberspacher agent) so why am I looking for something to keep my batteries better charged? Possibly I don't need anything but once bitten........ That's why I have the generator (belts & braces); so if I can find something to give me that confidence without having the bulk & weight then I suppose I will be happy

The inverter is only switched on for the short time that it is in use.

Sorry to have to say but no I don't have a multimeter or voltmeter & am a little ashamed to admit; no I wouldn't know one end from the other - but I know a man who does so I will make it my business to pick his brain. Dad was wonderful & I wouldn't have wanted to swap him - but he was not practical, consequently I was never shown practical things & on leaving school I was office bound!

Batteries are fine, I changed them only last year - again better safe than sorry.

Again sorry I don't know what make or model my on-board power supply is; I will try to find out tomorrow if it is important.

My initial query was to find out if I could use something to keep my batteries better charged. Perhaps I should have been clearer on my intensions - sorry for any mix up.

If you see an Avondale Seascape parked up by a loch, reservoir, glen, mountain or other outstanding scenes (okay some may not be outstanding) come on over, introduce yourself & join us for a natter. You can instruct me on all things practical & I can tell you all about the joys of 'wild camping'.

This is my first blog to MMM & wasn't quite ready for the amount of interest shown. It has certainly shown me that other motorhomers really care & want to help.

Thanks for your comments, help & information; I do appreciate it.

Timetraveller · October 26, 2010