The charge you get from the car while towing, or on site when on mains, won't properly charge the battery (George Telford can explain why - I know it won't fully charge, but not the ins and outs of the process!!). we have a 'proper' battery charger at home that we use to keep our leisure batteries (we have 2 85amp ones - a 110 is a tight squeeze in the locker, but we are largely battery dependant as we like rally camping with no facilities, so we have a second battery for piece of mind - haven't needed it yet!) - it is an 'intelligent' charger that senses the charge level of the battery and alters the charge it gives accordingly - it doesn't matter if we forget there is a battery on charge as it won't 'over-charge' - it cuts itself down to a trickle once the charge is complete. The charger also stated it was designed for sealed leisure batteries and had a charge profile that limits 'gassing' (batteries can produce hydrogen when being charged) and prevents boiling (the electrolyte gets hot too).
I'm sure there are other members on here who can tell you the 'technicalities' - we just bought a charger that stated on the packaging that it was designed to charge sealed, 12V leisure batteries, up to a size a little larger than ours, and that it could not over-charge or boil the battery if it was left on, so we don't have to watch it all the time (we charge the batteries in the garage, at the bottom of the garden, so it's not easy to do the quick, 'oops - I left the battery on charge' run to check all is OK when you wake up at 2am!!!). Our charger cost considerably more than the battery though!!!
I just read an article in one of the magazines yesterday, sorry cannot remeber which one, and it said you needed at least a two stage charger to maintain the battery in good condition. I think it quoted £80 for the lowest priced one, but they can rise to several hundred for more complex chargers. The chargers in caravans, due to costs, are pretty much worst that useless. Hence the caravan suppliers are full of batteries in the spring as they know there is going to be a high demand for them. I'm no sure if you are supposed to have them on a charge/discharge cycle when they are not in use, must likely you are!
1& 2 with a staged battery charger Sterling marine do a basic staged charger around £50 is the best method.
3. after every use and as soon as possibe
4. No not ever and if you use a good charger at home it will fill the battery if you then use a towing Charge (split charge) it will actually drain the battery on the journey
5. looking at for lights only a basic charger from Halfords after every weekend would do, BUT iwould still get the sterling at around £15 more and a far better charger (also good as a power supply on site)
if a leisure battery goes completly flat you need a multi stage charger to charge up to full capacity a normal single current charger will not. this is due to a back e.m.f. (electro motive force ) caused by the internal resistivity of the cells (trust me i'm a sparky)
split charging whilst on tow does charge battery unless your tow car battery needs charging the alternator charge will be diverted to leisure battery but it will only charge to around 60 to 70% if battery is not u/s
never store a flat battery as this will render it useless always store fully charged and to fully charge?...............you need a multi (or two ) stage charger
Refering to my previous posting the magazine in question is the July edition of Practical Caravaning. What I don't understand is that the charger is wired up in such a way that the caravan electrics are taken from the same circuit that charges the battery. So assuming that the electrics are taking part of the supply, will this not confuse the charger with regards to charging the battery? I assume it mustn't do so but I remain confused.
Your battery is used as a buffer/regulator for the charger/transformer when under high load. On high load, the current from the charger is used to power the van with any shortfall being met from the battery. On lower loads, the demand is met from the charger in effect with any excess supply being drawn by the battery for charging if required.
Think of it another way: your battery is just a permanently wired load on your charger - it competes for charger output along with everything else unless fully charged.
When on EHU, during the day and when you're asleep, the van load is virtually nil. So all the output from the charger is used to charge the battery. Peak current is likely to be in the evenings with lights pumps TV's etc etc and maybe a bit in the morning pumping water for tea and ablutions !!
Yeah, yeah - I know there's some debate on whether a charger/transformer really charges your battery to capacity. I leave that debate to others. All I know is the output of my 'van charger is 5A max and my bench charger is 1A more at 6A - this current would only be drawn if the battery was anywhere near flat. I've never suffered a flat battery when on EHU and it doesn't need much if any charging on the bench charger when I get home - the on board charger and the car seem to do the job between them.
Post last edited on 21/06/2005 18:13:37
------------- Caught in the crossfire between childhood and stardom.................
dont worry it seems like you have the right idea towing /charging does not flatten battery if your split charge relay is working and your car alternator is working it will trickle charge.
2 stage chargers are good for charging up dead flat batterys (below say 15% of full charge or less)
this can happen if you do not use ehu on site and use a lot of 12v stuff or for a long period also if you have a mover fitted this can drain battery if used a lot.
I did a test last year basically fully charged a battery then discharged to a set point with a bulb, fully recharged the battery but then attached to an alternator by nice thick cable and then drove around for 1 hr and 14 mins, The battery was attached when the engine was running and disconnected before switching engine off.
That extra 1 hour and 14 mins of "trickle charging" cost 54 mins in the discharge test ie there was 54 mins quicker to reach the same set point.
So if you start a Journey with a fully charged battery (ie you charge it up at home or on site with a good multi stage charger) if you then drive with this battery attached via a split charge relay it will be depleting the leisure battery.
If you charge it at home then do not travel with a split charge in place it will be depleting your battery reserves.
George,
How come I never have to charge my car battery? Just curious..............
There's a few questions about your test -
Were you charging your test battery via a split charger?
What was the state of the car battery?
What is the state of the voltage regulator in your car?
What is the state of your alternator and/or its brushes?
What was the time of your test - ie. were there lots of lights on, a/c running, or any other electrical load on your car's electric system?
What sort of journey was it - was there lots of sitting around at idle?
So many variables to address before any hypothesis can be tested anywhere near scientifically.
------------- Caught in the crossfire between childhood and stardom.................
Right its accepted the world over by experts in the field that an alternator never gets the battery charged above 70% (generally accepted at about 65% now)
all a starter battery ever does is start the vehicle and then act as a capacitor smoothing the loads and allowing the regulator to catch up (the regulator reacts to loads and then the alternator catchs up) ergo they have no reason to improve the charging up ability. if a battery is designed to start a vehicle at 65 % full never a problem (see link at end for expert testimony re alternators)
Split charge relay, NO I did better than that made sure that the engine on van was started before attaching the leisure via meaty cable and disconnecting before switching off the engine.
The van battery was nearly new (about 3-4 weeks old)
Alternator had been replaced about 7 months before and was supplying around 14.2v consistantly even with loads switched on and off.
Loads were normal for driving side lights indicators as and when, fan blower on I remember it was a warm day and radio on, ie pretty typical.
The driving did not include loads of idling as it was a test it was more or less out and back.
When I organised this test to people with Honours degree's in electronics said I was wrong and after a big online discussion went away to prove me wrong 14 months later they still have not come up with anything.
If you connect a draned battery to a good one in parralel then the drained battery draws from the good one until they equal out, so if the leisure is full and the starter is at its normal 65% then it will see two supplies the alternator and the leisure battery, Basically what happens is this.
This as been seen and confirmed by several people since, if you have a decent charger you can do the test yourself.
All I am stating is the FACTS if you fully charge at home then drive with split charge or towing charge, its supposedly charging the caravan battery, what I am saying is this that in reality it will take some chjarge away from a fully charged battery. Proved it over and over.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.
Topic: Battery
