20 watts=how many amps ?
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    Default 20 watts=how many amps ?

    i know next to nothing about electricity but am interested in adding heat to the stock 02 seat

    found what appears to be a nice seat heat kit on ebay for $50 delivered

    they say it puts out up to 20 watts of heat and comes with a hi-lo switch

    would like to hook it up to the 5 amp accessory terminals on the wing but since i already have Dual Star grip heaters hooked up there i am wondering if they will be able to handle the additional load ?
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    Seasoned Member Dream Catcher's Avatar
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    Default Re: 20 watts=how many amps ?

    Hey Mike....
    20 watts at the typical 14 volts DC coming from the running alternator regulator
    would be approximately 20/14 or 1.43 amps.
    The heat from the unit would be measured in BTU's I imagine.
    The electrical power used by the heater would be 20 watts.
    If they specified that power at the maximum, as it should be, then that 1.43 amps would be
    on the high heat setting of the switch.
    The low heat setting would probably be a setting of something more than half of that max.,
    as heater elements stop producing heat when the amps get too low.
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    Default Re: 20 watts=how many amps ?

    THANKS Dream Catcher

    so it sounds like the seat heater and heated grips combined will not come anywhere near the 5 amp limit of the accessory terminals, i will probably order the kit tommorrow, heated seat should be great up here in wisconsin
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    Seasoned Member Lone Ranger's Avatar
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    Default Re: 20 watts=how many amps ?

    Simple formula I use:

    watts divided by volts = amps or

    volts times amps = watts
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    Seasoned Member Auswing's Avatar
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    Default Re: 20 watts=how many amps ?

    The battery is listed as 12V 18 Ah. It is incorrect to calculate the current based on 14.4 volts.
    The workshop manual also states that it is fully charged at 13 - 13.2 Volts.
    Current should be calculated using a nominal 12 Volts.

    VOLTAGE (20°C/68°F):
    Fully charged: 13.0 – 13.2 V
    Under charged: Below 12.3 V


    14 volt batteries exist, but the Wing does not have one.

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    Contributing Member WingCdr's Avatar
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    Default Re: 20 watts=how many amps ?

    Quote Originally Posted by Auswing
    The battery is listed as 12V 18 Ah. It is incorrect to calculate the current based on 14.4 volts.
    The workshop manual also states that it is fully charged at 13 - 13.2 Volts.
    Current should be calculated using a nominal 12 Volts.

    VOLTAGE (20°C/68°F):
    Fully charged: 13.0 – 13.2 V
    Under charged: Below 12.3 V


    14 volt batteries exist, but the Wing does not have one.

    Trev.
    Auswing is correct. Alternator and battery voltages may be over 12V when you put a meter on 'em but will drop to around this nominal 12V value when in use/under load. The bike is a 12V vehicle and everything should be calculated on that basis.

    Formulae:
    V=IR where (V)oltage equals (I) current [amps] * (R)esistance [ohms]

    thus R=V/I etc

    P=VI where (P)ower [watts] equals (V)olts * (I) current [amps]

    thus I=P/V or V=P/I etc

    P=I2 R where (P)ower [watts] equals (I) current [amps] squared * (R)esistance [ohms]

    thus.....you get the picture - change the side [of the equals sign] change the operator - haven't got a square root symbol for this font and bulletin board!!
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    Default Re: 20 watts=how many amps ?

    Please explain why my volt meter reads 14 at idle and 14 + cruising? It's an 08.
    Thanks
    Jim

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    Seasoned Member LD_RIDER's Avatar
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    Default Re: 20 watts=how many amps ?

    My guess is that the alternator is charging the bike. Check the voltage with the alternator not charging (bike is off) and see what you get. The Goldwing alternator will begin charging at around 800 engine rpms...
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    Default Re: 20 watts=how many amps ?

    Quote Originally Posted by cycledude
    i know next to nothing about electricity but am interested in adding heat to the stock 02 seat

    found what appears to be a nice seat heat kit on ebay for $50 delivered

    they say it puts out up to 20 watts of heat and comes with a hi-lo switch

    would like to hook it up to the 5 amp accessory terminals on the wing but since i already have Dual Star grip heaters hooked up there i am wondering if they will be able to handle the additional load ?
    cycledude,
    To eliminate your concerns, use a relay(s) that takes power directly from the battery (fused) for both the grips and the seat. The power to trigger/operate the relay(s) would come from the accessory terminal. Radio Shack has a good selection of 12v relays.

    As far as the low side of the seat heater goes, it depends on how the heat is reduced. My old grip heaters had a single heating element and used a large resistor to cut the voltage to the heaters thus reducing the heat. That resistor did nothing to reduce the power that was used.

    The newer grip heaters (Dual Star & Elect Connection) use heaters with dual elements; both are on for high and only one for low. With these the low setting actually uses less power.

    Heated clothing uses a controller (HeatTroller?) that actually pulses the 12v to the clothing. For warmer clothing it sends 12v to the elements longer, with max heat gained with a constant 12v. It's basically an electronic on/off switch.

    Just more info for your to consider.
    Cruise On,
    Ron
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    Seasoned Member Stan Wright's Avatar
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    Default Re: 20 watts=how many amps ?

    There's not really a wrong answer when using 12V or 14V to calculate the current draw. When the bike is running the alternator is putting out around 14V, and when it's off the battery is supplying around 12V. Either way the calculated current isn't that much different:

    20 watts @ 14V = 1.43 amps
    20 watts @ 12V = 1.67 amps

    When I calculate current draw I like to use 12V because it gives me a small safety margin over the actual draw at 14V.

    I agree with DrtiBird about using a relay. It wouldn't take much of a current spike to toast that 5 amp fuse at an inopportune time.
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    Default Re: 20 watts=how many amps ?

    The wheel... If you know two of the variables (Like you knew wattage and voltage) the formulas below will cal the rest..

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    Seasoned Member Dream Catcher's Avatar
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    Default Re: 20 watts=how many amps ?

    Quote Originally Posted by Auswing
    The battery is listed as 12V 18 Ah. It is incorrect to calculate the current based on 14.4 volts.
    The workshop manual also states that it is fully charged at 13 - 13.2 Volts.
    Current should be calculated using a nominal 12 Volts.

    VOLTAGE (20°C/68°F):
    Fully charged: 13.0 – 13.2 V
    Under charged: Below 12.3 V


    14 volt batteries exist, but the Wing does not have one.

    Trev.
    Sorry Trev....but when the bike is running the battery has 14+ volts at it's terminals most of the time.
    If the loads the bike applies were to bring that voltage down to 12 volts, the battery would never get a full charge.
    Also, when the bike is running, it is the regulated output of the alternator that runs all electrical devices on the bike (including charging the battery at the same time).
    For this reason, in normal operation, the battery is not supplying anything to the system, but is in fact, just another load on the alternator's output.
    When calculating current draw for various wattage loads, the 14+ volts is the correct voltage to use, unless you only plan on connecting the load when the bike is not running. Then it would be correct to use the 12 volts in the calculation.
    Actually, the AGM batteries, in common use today, run closer to 13 volts than they do to 12.
    New vehicles will have a higher voltage regulator output to allow them to fully charge these newer style batteries. If you put an older (standard lead acid) battery in one of these newer systems, it will tend to overcharge...or boil the fluid off....the battery, possibly shortening it's life significantly.

    Stan... I wouldn't go so far as to put it like you did "There's really no wrong answer...."
    But I agree with you that it's not that critical and you should be fine using either 12 or 14 for most situations. 13 volts would be a good compromise for estimates.

    Mike, remember that some devices have a higher start up or "in-rush" current draw that only lasts for a blink as the device is turned on. Some heaters will draw more current than normal when they start heating the elements.
    If you install something and it blows the fuse, you can install a slightly large fuse to see if it's just the start-up current that is blowing it. If it blows with a slightly larger fuse, you should get the proper meters on the circuit and determine what it's doing.
    The Honda accessory terminal is fused at 5 amps and Honda sized that fuse with it's usual "buffer". The circuit can handle a couple more amps with no danger. So, if you need to put a 7.5 amp fuse in to keep it from blowing, it will work fine.
    I tend to agree with DrtiBird about using relays, just because I have boxes full of that stuff and like to overkill things..... but have to say that it's not required if the heaters are only drawing a couple of amps.
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    Seasoned Member Waldo's Avatar
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    Default Re: 20 watts=how many amps ?

    Use relays and there will be no worries. One should only use the 5 amp fused ACC terminal for tripping relays which do the heavy lifting. Relays are easy once you understand how they work and what goes where. Click the pic for a complete explanation.



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    Default Re: 20 watts=how many amps ?

    Here's the formulas I use... easy to remember and write even

    P
    ----
    I | E

    E
    ----
    I | R

    The first one, PIE is for power (watts) where I is current (amps) and E is voltage (volts)
    The second EIR is similar but uses resistance in ohms instead of power.

    Just write out the one you need to use (PIE) in this case. You want to find the current so put your finger over the I. That leaves you Power divided by Voltage. Or 20/12 which = 1.666667 amps

    Knowing the current and voltage, if you wanted to figure the resistance of the circuit, you'd use the second formula and put your finger over the R which would leave you with E/I or 12/1.666667 which would equal 7.2 ohms

    Quick, dirty, easy to remember and use and works for most circuits.



    The mnemonics I use are PIE and EIRE (Ireland in Irish Gaelic)
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    Default Re: 20 watts=how many amps ?

    Well after all that is said and done, 20 watts of heat ain't much. 20 watts X 3.414 = 68.28 Btus/hr. The average male body produces 450 to 500 btus/hr its self, so that 20 watt heater would do little to help warm you while riding in even cool weather. It would take 4 or 5 of them to produce enough heat to help.
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    Default Re: 20 watts=how many amps ?

    Quote Originally Posted by JohnACman
    Well after all that is said and done, 20 watts of heat ain't much. 20 watts X 3.414 = 68.28 Btus/hr. The average male body produces 450 to 500 btus/hr its self, so that 20 watt heater would do little to help warm you while riding in even cool weather. It would take 4 or 5 of them to produce enough heat to help.
    first of all THANKS everyone for all your help !

    John yes i agree 20 watts does sound like pretty low heat, my Dual Star grip heaters draw 36 watts on the hi setting, but then again there really isn't much chance of the heat from a seat heater escaping so i suspect 20 watts might be plenty, i ordered the 20 watt seat heater kit and will likely install it sometime next week, will give a report of how well it works then
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    Resident BBQ Expert loren's Avatar
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    Default Re: 20 watts=how many amps ?

    compare the 20 watt output of this seat heat kit

    to a set of gerbings pants or jacket liner

    and you will soon see its of little use

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    Default Re: 20 watts=how many amps ?

    Quote Originally Posted by Waldo
    Use relays and there will be no worries. One should only use the 5 amp fused ACC terminal for tripping relays which do the heavy lifting. Relays are easy once you understand how they work and what goes where. Click the pic for a complete explanation.
    Very good link Waldo. I saved the article to my Honda Tech folder. I save info like that because you never know when the web site will be taken down or when I can't find the link!
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    Default Re: 20 watts=how many amps ?

    Actually, it IS appropriate and necessary to calculate use amperage based upon alternator/regulator voltage; because that will be most common use current -- a wise rider does not sit and use the accessory with the engine off. The fuses specified will typically have enough marginal range to handel the difference even if you do calculate the amperage or wattage with 12V, but the charging voltage is the one that counts. Voltage is similar to pressure and the higher charging pressure is needed to force the current through the battery to displace the electrons so they can be stored.

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    Default Re: 20 watts=how many amps ?

    To be perfectly accurate you need to know at what voltage the seat heater manufacturer rated the heater to put out 20 watts. If they rated it at 12.0 volts then you can calculate the current draw at that voltage to be 20W/12.0V=1.67 Amps.. If they rated it at 12.6 volts then you can calculate the current draw at that voltage to be 20W/12.6V=1.59 Amps.. etc., etc.

    Now the important thing to know is that the heater will put out different wattage at different voltages, and draw different current. So if the heater is rated 20 Watts at 12 volts but your motorcycle battery is being charged to 14 volts (which is pretty typical while the engine is running) the the actual Wattage the heater will be putting out at 14 volts will be the voltage ratio squared times the wattage at the rated voltage or ((14/12)squared times 20Watts) or 1.361 times 20 Watts = 27.2 Watts! In other words a 20 Watt seat heater rated at 12 volts by the manufacturer will actually be putting out 27.2 Watts at 14 volts. 27.2 Watts at 14 volts is 1.94 amps, almost 2 Amps. Of course the difference will be less drastic if the seat heater manufacturer rated the heater to put out 20 watts at something higher than 12 volts, but it may be difficult to find out this information.
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    Default Re: 20 watts=how many amps ?

    Try here.

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    Seasoned Member John Baker's Avatar
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    Default Re: 20 watts=how many amps ?

    Quote Originally Posted by DrtiBird
    cycledude,
    To eliminate your concerns, use a relay(s) that takes power directly from the battery (fused) for both the grips and the seat. The power to trigger/operate the relay(s) would come from the accessory terminal. Radio Shack has a good selection of 12v relays.

    As far as the low side of the seat heater goes, it depends on how the heat is reduced. My old grip heaters had a single heating element and used a large resistor to cut the voltage to the heaters thus reducing the heat. That resistor did nothing to reduce the power that was used.

    The newer grip heaters (Dual Star & Elect Connection) use heaters with dual elements; both are on for high and only one for low. With these the low setting actually uses less power.

    Heated clothing uses a controller (HeatTroller?) that actually pulses the 12v to the clothing. For warmer clothing it sends 12v to the elements longer, with max heat gained with a constant 12v. It's basically an electronic on/off switch.

    Just more info for your to consider.
    Actually, that big resistor did reduce the current, and therefore the power being used by your grips. Since E=IR, I=E/R. Since E (voltage) stays constant, if the resistance goes up, the current goes down. It becomes more difficult to squeeze as much electricity through a smaller pipe! When you switch in the resistor, the resistance goes up, the current goes down, so the power (in watts) also goes down. The advantage of the dual heat elements is that as the available voltage is reduced to the heater element, the efficiency goes down, so if you are dropping half the voltage across the resistor, that means that only 6 volts is available for the heater elements, and they do not get half as hot as they would at 12 volts. You could do the same thing by having two sets of elements wired in parallel, and remove one set for the low setting. In parallel, they both get the same voltage, but the resistance is halved, so they get twice as much current and put off twice as much heat.
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    Default Re: 20 watts=how many amps ?

    The Warm & Safe Heat-troller™ is a DC (direct current), power controller designed for heated clothing, blankets, pads and other heated products that are powered by a battery. You can think of the Heat-troller™ as a dimmer switch for your heated products. It has a positive off and provides a full range of heat that is constant at any setting, just as a light dimmer switch gives you constant light at different levels.
    The Heat-Troller is a pulse-width modulated controller with a 1 second cycle time. That means that over a 1 second period, the power is turned on from about 10% to 100% of the time, adjustable with the knob on the controller. When the power is turned on, full power is applied to the load. In the example given, if the heated grip are 16 Watts each and the Heat-Troller is adjusted to 50%, the grips will get 16 Watts for half a second, then no power for half a second, giving an average of 8 Watts of power. The Heat-Troller is more efficient than a rheostat because it makes very little wasted heat when turned on. For two 16 Watt grips, the Heat-Troller makes less than 0.1 Watts of heat at 50%. A rheostat would make about 16 Watts of wasted heat at the same 50% setting.

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    Default Re: 20 watts=how many amps ?

    well the 20 watt seat heater kit is installed and it works GREAT, plenty of heat, actually maybe more heat than i needed, 15 watts probably would have been perfect for me

    so far i've only used it on a bunch of short trips

    today i plan to use it on a 100+ mile trip then should have a better idea if the heat level is acceptable or if i need to add somekind of heat control instead of just the simple on-off switch

    edit
    well i rode about 100 miles today, it was raining and snowing, good thing i am able to look over the windshield because it snowed hard enough to totally cover the windshield

    the 20 watt heated seat works great but it gets a little to hot sometimes, a heat troller would be better than just the on-off switch but i hate to spend the extra $50
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