Battery charging arrangement on Solar & Mains
Hello, and I apologise if this topic is already covered elsewhere
Having just got into caravanning (after 12 years of tents), we decided to buy a 'new' high spec one for our longer term retirement plans, but I am unsure and somewhat concerned about its battery charging.
We ordered a factory fitted 80W solar panel but it came with cheap controller that provide over-voltage to our ‘full’ battery when the caravan was in storage (and over-voltage also when in partial charge use on a sunny day). We replaced this full working controller with a high spec Voltronic MPPT controller that has 3 charging levels; all is now well for both off-grid use and storage.
My concern now is what happens when we connect to a sites 230v supply.
The caravan manufacturers handbook says our battery is then supplied with a constant 13.8 volts (regardless of battery charge state), but is this technically correct as the battery should surely have a similar charging multi-level voltage and current methodology as used in both our new intelligent solar panel controller and in our home used intelligent CTEK charger ??
My own though is that on providing 230v to the caravan, the battery should be totally isolated from the solar panel AND totally isolated from the caravan's 12v load (e,g, by a relay) so that it can be charged at an ‘independent’ voltage and current according to its own needs, using something akin to our intelligent CTEK charger AND that there should be a separate ‘’regulated 12v supply’’ for all our caravan needs such as pumps and lighting, provided directly from the 230v supply, without needing the battery for smoothing peak use.
Does anyone have any ‘technical’ thoughts on this ??
I am happy to invest in a proper system and am not concerned about warranty.
Am I perhaps too concerned for the limited days a caravan is used with 230v hook-up and should I just leave the caravan PB leisure battery charging on 230v at 13.8v ??
Thank you for kind comments and advice
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far too technical for me, dont have solar panels for caravan, but what happens basically, as i understand it, is that when on EHU battery is kept on charge and is monitored by the onboard charger as to how much power goes to battery, and obviously when on site and connected to EHU you still use 12 volts for some things such as some internal lights. When caravan is parked at home, during summer months I dont usually bother about connecting to my domestic mains supply, until maybe a couple of days before i go off on tour just to top battery up so that i can use mover, get fridge cold etc. In winter/cold periods if parked at home I leave domestic 240v supply connected so that battery does not get cold and freeze up, never had a problem, onboard charger keeps battery charged to 12.5 v, i normally check this weekly, i have an onboard volt meter in the caravan control panel. Caravan is 10 years old and still using original battery so i must be doing something right
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The caravan manufacturers handbook says our battery is then supplied with a constant 13.8 volts (regardless of battery charge state), but is this technically correct as the battery should surely have a similar charging multi-level voltage and current methodology as used in both our new intelligent solar panel controller and in our home used intelligent CTEK charger ??
One would think so, even the simplest of charges drop down to a trickle charge once a battery is fully charged. It might help to know what is the model of your caravan battery charger? Someone will know more about it and might be able to give further information on its performance.
If it is indeed a quality on board charger then in my view there is no need to isolate anything. Both the MPPT controller and the on board charger should react to the battery terminal voltage and neither should overcharge the battery.
All on board appliance designed to function from a 12v battery supply have a wide operating range to allow for charge and discharge voltages. I can therefore see little point in having a separate regulated supply when on EHU. To do so would only complicate things unnecessarily.
peedee
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Thank you for your replies
To answer peedee, our caravan is away in storage, but as far as I can ascertain without visiting, it is fitted with a BCA power distribution unit that incorporates an integrated 20A power supply unit. BCA make one that is a ''constant 13.8v'' so this fits exactly with the caravan manufacturers hand book (page 15) although I have been unable to find a detailed spec and manual for it.
If indeed the 12v caravan load ( radio, pumps, led lights etc) are all tolerant of voltages up to around 14.4 volts, then yes I would be happy to keep the circuit simple (smile). Would these sort of voltages be ok do you think ?
It would then beg the question whether it is worth upgrading to an 'intelligent' internal charger .... would such a unit 'fight' with the intelligent solar panel controller if they were both working at the same time, or would it be better to turn the solar off when the 230v charger is running ??thank you
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Many caravans are supplied with rudimentary chargers, some though are fitted with more sophisticated so called "smart" charges, ie multi stage charging like your CTEK and Voltronic units.
The 13.8 volts of the rudimentary charger is adequate for a reasonable state of charge, being set at the upper limit where gassing off if left continuously on is hopefully avoided. It is not good however to leave that on continuously as it is too close to gassing, the better for that trickle duty is 13.4 Volts but that's inadequate to exploit the battery's capacity.
If you put the EHU on whilst the Voltronic is doing its solar thing there will be no issues, the intelligent Voltronic will adapt and where necessary push up to higher voltages to best charge the battery. It should be or exceed 14.4 volts at times, but back off before gassing sets in.
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Excellent, thank you all very much.
I think I will give BCA a quick call in the morning and clarify their supply. It would be great if their charger in our new 2018 caravan proves to have some 'intelligence' as per the above spec.
( 'if so' a pity it was not mentioned in their caravan manual ! ).I equally feel that 13.8v ''continuous'' as a float voltage from a charger is certainly not ideal long term, as indeed it is too close to the gassing point IMHO.
I also favor 13.4v as a fully charged float voltage (when using an intelligent charger). Actually I prefer even lower, such as the 12.8v final float voltage of the Votronic MPPT intelligent solar controller, which is what led me to choose this particular one as it will be constantly connected all year to the battery ( I have no association with their company, but I did my research ).
I will post what I learn from BCA, but I will be away from the internet now for a few daysMuch appreciated !
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BTW, the solar controller I removed from my 2018 caravan was a Solar Technology International STCC10, apparently fully working, with specification as follows :
Over voltage disconnect = 16v
Charging limit voltage = 15.5v
Equalize charging voltage = 14.6v
Float charging voltage = 13.8v
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"I also favor 13.4v as a fully charged float voltage (when using an intelligent charger). Actually I prefer even lower, such as the 12.8v final float voltage of the Votronic MPPT intelligent solar controller, which is what led me to choose this particular one as it will be constantly connected all year to the battery."
I am confident that 12.8 volts you are seeing is not as you suggest the MPPT's "float charge" but the rested voltage of a properly 100% charged battery.
Here the solar charger like mine has dropped right down to a zero current output so not charging at all, however the readout is reflecting the battery's standing voltage.
And a very healthy battery maintenance routine that will be for a unit continuously connected. It will automatically revert to charging only when that is needed.
Other battery brands/technology will have slightly different standing voltages to 12.8, reflecting mainly the alloying in the lead specifically used by the battery builder. These days somewhat higher resting voltage than yesteryear.
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A basic caravan charger provides 13.8 volts which is enough to maintain a full charge but not too high for the caravan 12 volt system. This type of charger is still fitted to many makes of caravan such as Bailey (unless they have changed recently). A charger such as this will not properly charge a sealed lead acid battery if it becomes discharged, for which you need a proper charger providing 14.4 volts maximum but you have a solar panel so this may not occur.
The modern way is to provide an intelligent charger like a Sargent system which will take the battery off line and recharge it with a proper charging profile whilst still maintaining the correct caravan system voltage.
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I only mentioned Sargent because it is one of the larger suppliers but I can’t comment on how it compares with other makes. There are ma y posts on the Autosleepers forum where people have problems but that is often the case with electronic equipment. Mine works fine.
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BCA gives a constant 13.8 volts and is adequate to fully charge a battery. It will also prevent excessive electrolyte loss.
As mentioned Bailey use the BCA, and I used a battery for 9 years which never left the caravan. In fact it would have lasted longer if I hadn't inadvertently flattened the battery.
Swift use a multistage charger, with I have now along with command. The only advantage with a multistage charger is it gives a faster recharge time for a discharged battery. 14.4 volts initially followed by a maintenance voltage afterwards of 13.8 volts.
I also have a 80watt solar panel which has maintained my battery now while ever off mains, and I only use mains on site now. Bailey fit a 100watt panel which is more than adequate.
I've been checking my voltage levels daily using command since I took the wheels of in October and its never dropped below 12.5 volts, and is usually at 12.6v or higher when its daylight on solar charge, where its around 13volts plus.
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"I've been checking my voltage levels daily using command since I took the wheels of in October and its never dropped below 12.5 volts, and is usually at 12.6v or higher when its daylight on solar charge, where its around 13volts plus."
Given it is probably a modern technology battery then seeing 12.5 volts or even 12.6 off load and of course during the night when not receiving solar charge, is IMO not indicating a healthy state of charge.
As said, if a modern reasonable quality battery, then I would be far happier if it was indicating at least 12.7 volts,. At best 12.5 is indicating only an 80% SOC so its potential life would be being shortened. Some modern batteries 100% SOC voltage is now as high as 12.9, therefore, with these higher resting voltage units seeing 12.5 means the battery is way down.
You could determine this characteristic of your battery either from its maker's data sheets, or more practically by measuring it 12 odd hours after charging with your van's smart charger.
Daytime readings with a solar system attempting to charge will not give practically meaningful readings about the battery's SOC, it is those off charge that tell the story.
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I don't agree.
My last battery a cheaper from a dealer with only a 2 year warranty went to 9 years, while only ever showing around 12.6 on the Bailey voltmeter.
I do have an excellent battery fitted at present, I bought a quality category two battery this time round of 90AH to save a little weight and size, instead of a cheap 110Ah one.
Its a Varta LFD90 recommended to me and well liked on the Swift forum. Its SOC is normally 12.7v, so I'm happy to see it go to 12.5volt at 1am on a cold night, confident that its got more than enough to operate my movers if required.
I'll only put it on mains if the voltage shows 12.4v or less, it does no go at all to keep a battery constantly fully charged IMO.
With my last two batteries one 7 years before I let it go with the caravan, and my last at 9 years before I flattened it, both batteries over winter would only ever get a monthly charge via the Bailey 13.8v charger for a few hours during the day.
Ps as I said using command and can view the history of the voltage readings ever 6 hours approx. through the day and night. I take note of the early morning reading to establish a minimum voltage, and the daylight ones to confirm the solar panel is doing its work.
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Ive just got back from business travels and would like to really thank everyone for their replies and input which I have very much taken on board and researched further. Your replies have been GREAT and pointed me in the right directions – THANK YOU
Our new caravan’s handbook says that a battery must be connected at all times.
The next paragraph below (that may not be directly connected to the above statement) says that the Thetford fridge requires a battery connected for its gas ignitor to work.
I can find no indication in the Thetford fridge manual that not supplying 12v is a H&S risk
Does anyone know why a caravan battery MUST be connected at all times ??
Sure 12v is needed into the low voltage circuits but MUST this involve a battery ( e.g is it needed for smoothing ) ??Im interested to think about whether I could isolate our battery from the complete caravan 12v demand using a simple battery on/off switch; run the total caravan demand only from the 20A 230/13.8v PSU and during this time allow our ‘’intelligent’’ solar controller to remain connected to charge the battery to 100% (something a constant PSU 13.8v will not do - and it would also reduce the battery float voltage from the PSU 13.8v down to the solar float of 13.4v ).
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May I ask why all the worry. If fitted at dealers then the solar will/should go through the PSU and be controlled by that so if hooked up to ehu the solar will take no part in the charging. If no ehu then the solar charges battery and when the car is connected the solar again takes no part as vehicle charges battery. In the darker days of winter I remove the battery and take home and give it a boost every couple of weeks via a smart charger at home. If no battery fitted then nothing 12v will work even when on ehu. by the way when I say psu will control I mean what is charging the battery, not what the voltage is going into the battery.
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Worried - no (smile)
As posted, I am regretfully just sorting out all the factory supplied set-up and equipment that came with my new caravan ( including factory fitted solar panel) and in the process i am upgrading some things.
First I had to upgrade the supplied solar panel controller 'if' I did not want the cheap controller to overcharge the battery under 2 x sets of conditions and reduce its working life. Now I am looking at what happens when EHU charges our battery.
Solar panel controllers should be installed direct to the battery as per their instructions and not through caravan equipment, so it follows that Solar will always try to charge a battery (subject to voltages and sun). Our PSU certainly does not turn off our Solar charging and I cannot see any way that a car hook-up would influence it either. .
I am happy I now have a proper working solar system, which is important to me as its hooked up all year, BUT I am not so happy that on EHU my system gives a constant 13.8 volts float voltage to my battery under all charge conditions and that at 13.8v can be expected to only give the battery an 80% charge
Im wondering about purposefully isolating the battery when on EHU so I can charge it correctly using an intelligent charger such as CTEK
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As the 230v EHU PSU gives 13.8 v into the caravan system, I am interested in why my caravan handbook states that a battery MUST always be connected ... I dont know why ... it could be for smoothing reasons ?? !!
Hope that explains where I am coming from. I would welcome more explanation of your comments as it could be very applicable if I have misunderstood our caravans wiring logic.
I should highlight that we are new to modern caravaning but find a number of caravan design matters quite aggravating ... a good example is the battery locker (smile)0 -
The battery provides smoothing to the rectifier (charger) which may be necessary for some electronic devices hence the statement about having a battery connected. I suppose that it is possible also that without the battery the open circuit on the charger may produce a higher voltage than the system design.
13.8 volts is fine as a maintain voltage but over a period of time will degrade the battery so the standard advice is not to leave on EHU for long periods unless you have an intelligent charger. The other problem is that if the battery becomes discharged it requires 14.4 volts or thereabouts to properly recharge. 13.8 V will not do it and your battery life will suffer suffer. If it ever gets to this stage take the battery out and recharge with a CTek or similar.
A solar panel can produce quite high voltages but the current is low so is unlikely to damage the battery.
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Solar panel controllers should be installed direct to the battery as per their instructions and not through caravan equipment, so it follows that Solar will always try to charge a battery
never heard that before as my lunar delta wiring diagram shows wires to the ec500 psu ready for the solar to connect to and that's what I used and also displays on the panel above the door for solar info and believe that all new caravans have this facility on the psu.
Hitch, its true that solar can give a very high voltage but that's what the controllers there for to limit the voltage to approximately 14.7v peak and hence protecting the battery.
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The fridge control circuit requires 12 dc to work, its possible that I battery isn't required while on mains with the charger on, but I have never tried it as I require a battery for the mover.
You could pull the battery fuse located near the batter, if one is fitted, and see if the fridge still works, they will be no damage due to high voltages.
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It should do what size is the solar panel fitted? As long as you don’t have a component failure. You fit SP and forget it. But it should keep your battery charged in storage, unless your battery is creme crackered or you have left something on.
Must say this thread has amused me. Talk about overcomplicating a subject.
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Mine battery lives in the van 12 months of the year. The only time they are removed are if we have screwed up a left something on ( outside light most recently). Or after 4 day’s on a new year rally time to give the battery a bit of a charge. This is with a 150W panel and a PWM controller.
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Even with decent sized panels, the output at this time of the year is quite small. Enough to replenish an alarms consumption but not much else.
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