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Car Forum / Australian Car Forums / 4x4 Cars (Australian group) / November 2006Fridge Timer
Hi Guys. Is there any such thing as a 12v timer, similar to a turbo timer, that will keep something running for a preset time once the vehicle is turned off? I am thinking of something like this for my fridge (Evakool RF47). I have it in the back of the Landcruiser and it comes in great for keeping drinks etc cold. Problem is, especially around town, the constant turning on and off of the car does not allow the fridge to run long enough to stay cold all the time, and on really hot days, sitting in a hot car, it really struggles. I thought if I could put in a timer, similar to a turbo timer, that would keep the fridge running for, say, 30 minutes while the car is switched off, then the problem would be solved. 30 minutes would have minimal effect on the cars battery, but the fridge would stay nice and cold. If we parked for longer than 30 minutes then the fridge would shut down and not drain the battery flat. Is there such a device? Does it sound like a good idea or am I being stupid?? Garry Gary, I think its a bit unneccessary. As long as you remember to turn it off at night a decent battery should run the fridge all day , even without the vehicle running at all. I have an EvaKool FM55 and the stated current consumption is 0.7 A/H. @ 6 deg. In practice its better than that. Even if the fridge was working hard and the consumption was as high as 1 A/H thats still fairly insignificant over a few hours. I have a 100 A/H battery which I use to run the fridge when camping . I have left it running continuously for 5 days and the battery voltage was still above12 V If you're still nervous about leaving it on there are various programmable timers available from Dick Smith etc which would require a bit of adaption to suit your purpose. Check what the current consumption of your fridge is. I also use a smaller cooler in the front which draws about 2.5 A continuously and my standard vehicle battery will run that for hours without the motor running I'm very happy with the Eva Kool by the way.An added bonus, each basket neatly holds 1 dozen stubbies so they don't move around or rattle and theres still plenty of room on top for less important items DP > Hi Guys. > [quoted text clipped - 23 lines] > > Garry Thanks Richard. If we were only using the fridge for travelling and camping I don't think it would be a huge issue with having it hardwired, but we actually have the fridge in the car all the time and it would be good to have it running all the time without having to worry about leaving it too long and flattening the battery. I think, from memory, the running consumption of the fridge is about 20 amps / 24 hours so it certainly would not flatten the battery in 1 day, but I just don't like to take the chance. As you mention, perhaps another way is to give it its own battery to run off, and use a smart charger to charge that battery while the car is running? I just thought the easiest way would be to use some kind of timer that would allow the fridge to run for 30 mins or so, maybe even a couple of hours, each time the car is turned off. Best regards Garry > Gary, > I think its a bit unneccessary. [quoted text clipped - 51 lines] >> >> Garry Garry said.... > I think, from memory, the running consumption of the fridge is about 20 > amps / 24 hours so it certainly would not flatten the battery in 1 day, > but I just don't like to take the chance. I s'pose you could trial it at home. Pick a warm day, put stuff in the frige (particularly stuff that's great on a warm day) and let it go. Then after a few hours see how much charge is in the battery (try starting it). Just have a second vehicle nearby with a set of jumper leads... > As you mention, perhaps another way is to give it its own battery to run > off, and use a smart charger to charge that battery while the car is > running? A mate set up twin batteries in his 4WD with some sort of diode arrangement so that they'd charge but wouldn't deliver power to the car, only to what it was intended for (accessories such as car fridges). > If we parked for longer than 30 minutes then the fridge would shut down and > not drain the battery flat. > > Is there such a device? Can you build electronics kits? If so, contact silicon Chip magazine and ask if they have a circuit/kit for what you want. Really is is just a basic timer circuit.when the car is turned off, it stops topping up a capacitor which slowly discharges and after desired time drops a relay, Hi Garry Perhaps another approach might suit you better - 1. connect the fridge to a point in your car where the 12v is on all the time - ie doesn't go off when the ignition is off etc 2. buy one of those 'disconnect when battery falls below ??v) devices - it will switch off the fridge before your battery reaches the '%$# wont start the car' stage Then all your probs are solved - though if it was me I would fit a 2nd battery if I was doing a lot of travelling David > Hi Guys. > [quoted text clipped - 22 lines] > > Garry Good idea Dave, I like it. I will investigate one today. I think if I was doing a lot of travelling then there would be no need for it as the fridge would be running more often with the engine also going. It is because I am using it around town that I am a little concerned with running the battery flat. Too many stops and starts. Best regards Garry > Hi Garry > [quoted text clipped - 46 lines] >> >> Garry Or, you can do a rough-as-bags job and get a normal 340v timer, one that works on a mechanical spring arrangement. Modify the pins/socket to take a 12v connection and plug it into an always-on outlet (some 4WDs have them in the back luggage area). Just turn the dial to the required on time and leave it. > Or, you can do a rough-as-bags job and get a normal 340v timer, one > that works on a mechanical spring arrangement. Modify the pins/socket > to take a 12v connection and plug it into an always-on outlet (some > 4WDs have them in the back luggage area). Just turn the dial to the > required on time and leave it. Just a small word of caution in relation to running 12 volts through switches designed for 240 volts. The air gap in DC switches is much greater than the air gap in 240 volt switches as Ac current tends to self quench any arcing. You may well find that the switch on your timer will weld closed due to arcing. I sort of found this out the hard way in our old weekender which was wired for 32 volt power (and had an ancient flat head 4 cyl engine driving the 32 volt genny too). I used a couple of standard swithces to replace unserviceable old bakerlite ones and one managed to comprehensivley fry itself with arcing. The mechanical timer switch fitted to Simpson dryers is rated to 32 volts DC so would be a safe one to use, unfortunately you need tofind one at the dump because new they are around $35 trade. How about a turbo timer and a relay? -- >> Or, you can do a rough-as-bags job and get a normal 340v timer, one >> that works on a mechanical spring arrangement. Modify the pins/socket [quoted text clipped - 21 lines] > one at the dump because new they are around $35 trade. How about a > turbo timer and a relay? How about he just plain sorts it out properly with a seond battery and a split charging circuit. Best possible outcome and you can run for days on end and still start your car. If it draws approx 3amps for 20min at a time for 8 hours thats equivelent of a 8 Amphour battery. A small 26Ahr would set you back stuff all (Retail around $80) and as long as you recharge once down to say 11 volts (approximately 18 hours running without charge. Or three days at 6hrs a day) it will last ages. Or if you are close to SEQld I can provide you with a decent larger battery at a VERY good price. Scotty >>> Or, you can do a rough-as-bags job and get a normal 340v timer, one >>> that works on a mechanical spring arrangement. Modify the pins/socket [quoted text clipped - 34 lines] > > Scotty Hi Scotty. Thanks for the tip and I agree. I think the battery is the way to go. I could be interested in a battery at the right price. We are dealers for Optima Batteries and I use them in my boat, but they are very expensive. I could be looking for something cheaper for the car fridge and also another one for the new camper trailer. Best regards Garry >>>> Or, you can do a rough-as-bags job and get a normal 340v timer, one >>>> that works on a mechanical spring arrangement. Modify the pins/socket [quoted text clipped - 46 lines] > > Garry Well if your a battey dealer you should have the best deals around. I usually pass on second hand (but still with years of life) Sealed Lead Acid Batteries. 65-100 Ahrs I usually let go for $40 each unless they are exceptionally good in which case $60 each. Kevs had a few and hes happy with em so far. Even though they are second hand they sit in service with a fully regulated charge in perfect conditions for up to two years then I pull em out. Most have a 5-10 year service life and the ones I pass on are always good uns. I dont get em daily or anything, more like they come along when they come along. No pattern to when. But I do put the good ones aside for those that are interested. Scotty >> Hi Scotty. Thanks for the tip and I agree. I think the battery is the way >> to go. [quoted text clipped - 22 lines] > > Scotty Hi Scotty. Mate we are not a battery dealer, but rather marine electronics. We also stock UHF and other items including Optima Batteries. yes it is tempting to grab an Optima and throw it in the new camper, but even at my dealer price it is still a very expensive option (The 75amp deep cycle & starting combo battery retails at over $500!!) I think a good second hand one would be the way to go. Let me know when you get some more in, especially the 100amp hour ones, as I have a medical machine I need to use which chews about 25amps per night (on 12v) Best regards Garry >>> Hi Scotty. Thanks for the tip and I agree. I think the battery is the way >>> to go. [quoted text clipped - 35 lines] >have a medical machine I need to use which chews about 25amps per night (on >12v) gee whiz ! thats a power hungry vibrator <(:~-)) >Best regards > >Garry > On Sat, 25 Nov 2006 20:41:44 +1000, "Garry Beattie" >>Let me know when you get some more in, especially the 100amp hour ones, as [quoted text clipped - 4 lines] > > gee whiz ! thats a power hungry vibrator <(:~-)) Ha!! Yeah well, you know how it is!!! Garry > Hi Scotty. > [quoted text clipped - 12 lines] > > Garry Umm what do you mean draws 25amps per night? What is the current draw and how long do you use it? Amp draw is an instant measurment. If you mean draws 3amps for 8 hours thats 25A/Hrs. Thats the calculation you need to determine before you get yourslef a battery. Also take into account that the 100Ahr batteries are around 30Kgs. You dont want to keep carrying them around all the time so an easy removal for daily use is a good idea. >> Hi Scotty. >> [quoted text clipped - 19 lines] > the 100Ahr batteries are around 30Kgs. You dont want to keep carrying them > around all the time so an easy removal for daily use is a good idea. Sorry I should have been a bit more specific as I am looking at 2 separate projects at present. 1 is a smallish battery for the fridge in the car and the other is for a larger battery for permanent placement onto my new camper trailer. The one I was referring to in the last post is for the trailer. The machine I use keeps me breathing at night and uses about 2.5 amps per hour, over 8 hours. I always allow a bit more so I calculate about 20 amp hours per night. As far as the fridge in the car goes, I think I will organise the install of a 2nd battery system under the bonnet and then run a constant power feed to the fridge in the back, as well as my electric boat winch outlet. The worst that could happen is that I would flatten the 2nd battery but still be able to start the car from the original battery. That's the theory anyway. Garry >>> Hi Scotty. >>> [quoted text clipped - 30 lines] > machine I use keeps me breathing at night and uses about 2.5 amps per > hour, **You mean its current draw is 2.5Amps. This isnt a rating its a measurment (Sorry, Im not trying to be awkward just accurate for your purposes) Any batteries you get derate at at least 20%. So if yoru drawing 2.5 amps for lets say 10 hours (You may sleep in!) thats 25AHrs. Derate at 20% and you will need a 40 AmpHr battery (Thats the next size up from 26AHr) Even the 40AHrs are resonable to buy new, less than $100 from memory. But if you want a second hand one or three I can provide those at around $25 each for ones with plenty of life in em. If this machine of yours cant do without power in the middle of the night Id buy a new one if I were you. Or at least one backup and a decent charger set up. Scotty > over 8 hours. > [quoted text clipped - 8 lines] > > Garry >>>> Hi Scotty. >>>> [quoted text clipped - 45 lines] > > Scotty Hi Scotty. Yes the machine draws an average of 2.5 amps per hour. It is very doubt full I would sleep in as I never do that. The machine can not live without power, however I can live without the machine, so if the battery fails through the night it does not become a life threatening thing, but it can be if I do away with the machine all together. (If you understand what I am trying to say?) I am sure a smaller battery would be fine but keep in mind that we will also run camping lights etc off the same trailer battery, so I would like to get something quite powerful. I like the idea of a 100amp hour battery as that would have power to spare. I do intend fitting a good charging system to the trailer that will charge the battery off the car when travelling, but also charge if plugged into 240v. Best regards Garry > Hi Scotty. Yes the machine draws an average of 2.5 amps per hour. It either uses 2.5AHrs or draws a constant 2.5 Amps, both are different consumptions. It is very > doubt full I would sleep in as I never do that. Ive kids, I cant do that either! Damn it! > The machine can not live without power, however I can live without the > machine, so if the battery fails through the night it does not become a > life threatening thing, but it can be if I do away with the machine all > together. (If you understand what I am trying to say?) I hear you. > I am sure a smaller battery would be fine but keep in mind that we will > also run camping lights etc off the same trailer battery, so I would like [quoted text clipped - 4 lines] > the battery off the car when travelling, but also charge if plugged into > 240v. How do you intend on doing this? Im not having a go Im curious because theres soooo many ways of doin it. Some are a waste of time some are perfect. Obviously the perfect ones are dearer. > Best regards > > Garry >> Hi Scotty. Yes the machine draws an average of 2.5 amps per hour. > > It either uses 2.5AHrs or draws a constant 2.5 Amps, both are different > consumptions. I would have to consult the manual. I thought they were the same. >> I do intend fitting a good charging system to the trailer that will >> charge the battery off the car when travelling, but also charge if [quoted text clipped - 4 lines] > Some are a waste of time some are perfect. > Obviously the perfect ones are dearer. I am asking questions about this now with various people, but I think the simplest solution would be to mount a battery charger inside the battery compartment with a 240v inlet wired up to it from the outside. That way when you plug into 240v, the camper will still work off 12v but the charger will be charging the battery. Otherwise the battery will charge direct from the car when plugged in through an Anderson plug. Garry >> Or, you can do a rough-as-bags job and get a normal 340v timer, one >> that works on a mechanical spring arrangement. Modify the pins/socket [quoted text clipped - 21 lines] > one at the dump because new they are around $35 trade. How about a > turbo timer and a relay? I thought about a turbo timer but they only go up to a couple of minutes tops. I was looking more at an hour or so. I think the best and easiest way to do it would be to have a second battery with a charger attached. The fridge runs off the second battery constantly. When the car is running it is charging up the 2nd battery. If the 2nd battery happens to run flat then the fridge stops, but doesn't flatten the car battery. Garry > Or, you can do a rough-as-bags job and get a normal 340v timer, one that > works on a mechanical spring arrangement. Modify the pins/socket to take > a 12v connection and plug it into an always-on outlet (some 4WDs have > them in the back luggage area). Just turn the dial to the required on > time and leave it. Thanks for the idea, but I want one that automatically resets each time I turn the car off (or on, whichever way you look at it). Garry |
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