Hairdryer - My Soultion

Discussion in 'Tech/Mech General' started by Craig Rogers, Nov 24, 2011.

  1. Craig Rogers

    Craig Rogers Read Only Funster

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    Hi all,

    There is always talk about Hairdryers, so I thought I'd share my solution for it to help anyone else trying to work it all out.

    Firstly, a big thanks to everyone who helped along the way in getting this solution worked out! :thumb:

    The other half has very long hair that needs to be dried, so when out Wild Camping, we would need a hairdryer.

    12V ones, as most know are pointless, most modern hairdryers are at least 2000W. Go below 1000W and again, they start becomming difficult to use and would need more time to dry.

    So, I had a look through some of the dryers that Emma has and she has a travel dryer which is rated at 1200W and has 2 speed settings.

    Hmmmm? If 1200W is for speed 2, I wonder what the difference speed 1 makes? More on this later......

    1200W hairdryer when on EHU shouldn't be a problem as it's only 5 amps (maybe a bit more if on 220V). You still have to be carefull depending on the EHU supply and what else you have powered up, but generally should be ok.

    When EHU is not available, getting 1200W out of 12V is a bit tricky......

    So, I opted for an Inverter which will convert 12V into 240V. There are 2 types of inverter, "Pure Sine" and "Modified Sine". Without going too technical, this is the waveform of DC. Pure Sine gives you pretty much what you get at home where as Modified is not. Does this matter? For a Hairdryer, not normally, however, for Hair Straigteners (particulary GHD) it does matter but more on that later.

    Pure Vs Modified is down to cost, a Modified Inverter is a lot, no, LOADS cheaper than a Pure Inverter. Therefore, I opted for a 2000W Silverline Modified Sine Inverter. I'm never going to run it at 2000W, but it's there for capacity as the 1000W would be too low for the 1200W hairdryer.

    Now, let's do some calcs.........

    To get 1200W out of 12V, that's a serious amount of amps, 100amps, however, due to the efficiency of an Inverter, it's safer to divide the Watts by 10%, so 120amps.

    Run that through your Lesuire battery and it would be a serious draw on the battery. No problem you might say, just start the engine which will help.

    No, as the connection between the alternator and Leisure battery (via the Cab Battery) will probably have a fuse that isn't high enough rated and will pop!

    So, I opted to connect the Inverter to the Cab battery. Same rules apply here, run the Inverter and it will flatten the Cab battery. Therefore, when the hairdryer is being used the engine is started to provide charge to the battery. Again, you have to be carefull here as the alternator fitted to your MH might not run at the same ampage as being drawn out of the battery.

    It's unlikely the alternator will die as it's regulated and will only provide what it can provide, so won't over work it. However, some might say that running an alternator at it's peak for extended times might reduce it's life....... Judgements out on that one for me!

    When Inverters are not in use and even switched off, they can still draw power from the battery to keep it's capacitors charged, therefore, can still flatten a cab battery if left over time, therefore, I opted for an Isolation switch which sits on the Positive feed to the Inverter so that I can switch the supply off. There are loads on the market, but a lot of them only rated at 100amps. I opted for a 300amp one!

    Keeping the supply cables as short as possible is also recommended to avoid voltage drop. I was lucky as the Cab battery is fitted under seat in a MK7 Transit.

    Below are some photos (apologies for the quality, they are from my Blackberry) and explanations, including using a power meter to see what the hairdryer was pulling from the Inverter;

    Below: The Silverline 2000W Inverter fitted behind the passenger cab seat. Instructions do say to mount level, but I suspect this is to help airflow as they do have cooling fans. I'm sure it'll be ok vertical.
    [​IMG]

    Below: The Isolator fitted into the base of the passenger seat.
    [​IMG]

    Below: Back of the isolator inside the seat base. Taped up the connectors just in case something metal earths against the metal.
    [​IMG]

    Below: Here is a simple Energy consumption device showing the Watts being drawn by the Hairdryer (remember, the engine is running at this time). As expected it's just short of 1200W when on full power.
    [​IMG]

    Below: Now the interesting bit, turned the Dryer to speed 1 (low) and look at the huge difference in Watts being drawn. Down to just below 550, but on 12V, it's still roughly 55amps!
    [​IMG]


    Now, just out of interest, I grabbed Emma's GHD Straighteners and decided to look at the power draw these have. Remember, these are NOT being run through the Inverter......why? GHD's need Pure Sine so won't work on the Modified Sine Inverter. So, why don't I see this as a problem? Because you can get Gas powered straightners as an alternative making the extra outlay in a Pure Sine Inverter not financially viable (to me anyway).

    This little bit extra is to put to bed some thoughts about using GHD whilst on EHU. A quick look on the label and it will show you that GHD straigteners only consume 35Watts. Hmmm, I couldn't believe that so this is why I did this test. The GHD's are connected up to my home 13amp EHU for the test (not that it's important).

    Below: First picture shows a large power draw of 264Watts - Huh, so much for the 35Watts! On EHU, that only equates to 1.1amps, so you should never get any issue with them.
    [​IMG]


    Below: Now compare that to the photo below, this was once the straighteners had been on for about 3 minutes. Voila! Much closer to the 35Watts specified by GHD. Therefore, the 35Watts is only once it's got to temperature. That's now 145mh (or 0.145amps)!!!!!!
    [​IMG]

    So there, you go, hopefully, this will help anyone looking to take care of hair electric products.

    Regards
     
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