tubthumper said:
Also, is there anything stopping me simply hardwiring my CTEK optimiser / charger into the van and just forgetting about it?
Ctek make a range of optimiser chargers, and there would be not problem using the XS - 7000 or the XS - 25000 that is what they are designed to do.
However I would assume if the MSX - 7 would do the job they would not make the XS - 7000! I don't have a Ctek, I have the cheap Lidi however I think they are similar, and if I connect the Lidi charger to the battery and mains it will show if battery leads reversed, and the battery voltage, but nothing else, it does not start charging, to start it charging I have to press a button, I have four options, 1) Small battery under 14 Ah. 2) Large battery 14 to 120 Ah. 3) Cold charging with raised voltage. 4) Off again.
Once charging has started with large battery mode it drops current in stages, starts at 3.8A then 3A then 0.8A then 0.1A and then zero. If the battery self discharges it will return to 0.8A stage, but there is nothing to make me believe it will return to 3.8A stage without my pressing buttons.
I would like to test this, but as yet have not, but if it does not return to 3.8A then it would never maintain a caravan battery in use. Maybe you can test the Ctek you have and report back, it would be interesting to know if they return to max output when battery is loaded.
I have been testing the Lidi charger, but to measure charge rate on 12 volt side it would require me to sit there monitoring a ammeter, however what comes out, must go in, so I use an energy monitor on the 230 volt side to record what the charger is using, which shows me clearly at what point it changes stages. Mine is linked to PC so can see what a battery in garage is using from my bedroom, however even the basic units will show how much it has used so average 2W means charging at 0.1A etc. So 3.8A x 13.8V = 53 watt, there will be loses and as voltage varies so will watts so 60W in = 3.8A charge as it drops to around 45W you know at 3A charge, the massive drop to 12W shows 0.8A charge and 3W 0.1A charge, far easier than trying to connect up an ammeter to 12 volt side, that is assuming of course you have a plug in energy meter.
I am monitoring a battery at the moment, so don't really want to reallocate what the charger and energy monitor is doing, once complete I will test to see if when under load the Lidi charger returns to higher charge rate. However that does not really help you as your using a Ctek not a Lidi charger.
I do carry a Lidi charger for emergency use, and I would connect it and press the mode button when required to be able to finish holiday, however if the built in charger was to fail it would be replaced with another large charger, although you can use 20A in evening and then allow battery to recharge over night, I think it is better if for most of the time the charger takes the load, and battery is not discharged and recharged many times through the day. So I would think most caravans need at least a 15A charger to not discharge battery when lights are used. This clearly will vary, some caravans have LED lights, some have mixture 230 volt and 12 volt lights, so there is no one charger fits all.
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