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12V INVERTER
- Thread starter HERTS P&D
- Start date
I assume the jetter has a tank of water that can freeze. I would look at a mini 12 volt immersion fitted into the tank to give the most efficient use of battery power to heat the water.
The element from a 12 volt travel kettle with an added frost stat might be worth considering.
DetlefSchmitz suggested using large wattage resistors which if fitted to the tank would also be a very efficiency use of the power.
Direct heating of the water will require a thermostat to avoid wasting power by over heating the water above 5 degrees C.
With direct to tank heating some thought might be needed to prevent water left in pumps and hoses freezing.
The element from a 12 volt travel kettle with an added frost stat might be worth considering.
DetlefSchmitz suggested using large wattage resistors which if fitted to the tank would also be a very efficiency use of the power.
Direct heating of the water will require a thermostat to avoid wasting power by over heating the water above 5 degrees C.
With direct to tank heating some thought might be needed to prevent water left in pumps and hoses freezing.
So how would that work?
Andy
Andy
My goodness, those are hefty batteries! - how big/heavy are they, and how big is the van? I was thinking more in terms of 100-200 Ah.
Kind Regards, John
The water tank is emptied every night, I need to stop the pump and hoses freezing.
The van is a MK7 140hp Transit LWB/HR. It comes with 2 batteries as standard. I have also added an extra one, 3 in total.
I still don't understand how the 'large wattage resistors' would work?
Andy
The van is a MK7 140hp Transit LWB/HR. It comes with 2 batteries as standard. I have also added an extra one, 3 in total.
I still don't understand how the 'large wattage resistors' would work?
Andy
The most efficient (essentially 100%) way to covert energy from a battery into heat in a particular place is to simply use the battery to pass current through a resistor. A 1.2 ohm resistor across a 12V batter would result in 10A (12 divided by 1.2), hence 10x12=120W. Anything in addition (inverter, mains voltage heater) will just introduce potential 'inefficiencies'. Essentially 100% of the electrical energy used will still be converted into heat, but not necessarily where you want the heat (e.g. the heating of the inverter may not be where you want heat). However...
I assume it's was being suggested that you simply effectively 'submerged' the resistor in the tank, to prevent the contents freezing. However, if the tank is being drained, and the frost protection is needed for other components, the that obviously would not be appropriate.
Kind Regards, John
The tubular heaters are not much more than very large resistors in tin cans.
Using small resistors means you can put small 12 volts heaters where the heat is needed so you could fit one to the pump. To protect the hoses would require some way to confine the heat to the hoses.
If they are stored on metal reels then gently heating the reels and covering the reel and hose with a blanket to retain the heat would work.
EDIT There are heat pads for pet baskets that are 12 volt operated. Some of these are flexible enough to be wrapped round equipment.
Using small resistors means you can put small 12 volts heaters where the heat is needed so you could fit one to the pump. To protect the hoses would require some way to confine the heat to the hoses.
If they are stored on metal reels then gently heating the reels and covering the reel and hose with a blanket to retain the heat would work.
EDIT There are heat pads for pet baskets that are 12 volt operated. Some of these are flexible enough to be wrapped round equipment.
True (assuming you're talking about the value {i.e. resistance} of the resistor), if one wanted exactly 120W - but I'm sure the 120W was a purely arbitrary guess, based on what heaters the OP bought - and that he could have guessed something appreciably different. With a 1.2Ω resistor, one would get about 132W at 12.6V and about 150W at 13.4V.
A 1.2Ω 150W resistor would probably consist of just a coil of fairly fat wire.
However, as we now know, this approach would probably not be appropriate for the OP.
Kind Regards, John
I covered the hose reels with a couple of dust sheets last year but this year their will be some heat underneath the dust sheet this year.
But how would the resistor be wired up?
Andy
Either value or power rating.
The simplest way is two leads to a pair of croc clips to go on the battery with an insulated in line fuse in the lead close to the positive croc clip ( assuming a negativeto chassis system )
Much better would be to mount the resistor on a piece of heat sink with a thermal switch to prevent over heating and reduce the energy taken from the battery. In the shed there is ( should be ) one I made earlier so tomorrow I will dig it out tomorrow and post a photo.
OK - so in the case of power rating, higher than what? I don't think that anyone (certainly not me) had said anything about what the power rating of the resistor should be. Whatever, the rating would obviously have to be at least as high as the amount of power generated in the resistor at the highest possible operating voltage.
Kind Regards, John
Indeed, so for the suggested 1.2 ohms, it would need to be greater than the suggested 100W.
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