Hot grips, install a relay, winter's coming!

[gspd]

I use my heated grips a lot, as soon as there's a chill in the air, they're 'ON'. Even if it's summer.
I don't know how many of you use heated grips and whether or not they're OE or aftermarket, but this will be helpful to all hot grip users.

My bike came factory equipped with heated grips, and the factory decided that piggy-backing their wiring on the brake light circuit was a good idea. Well, I guess it was, sort of.
I used them that way for three decades without a complaint, loved 'em.

Yesterday, on a whim, I isolated the heated grip circuit and powered it from a fused relay, so now they get direct battery power.

Two (good) things happened.
1 - The grips get REALLY REALLY REALLY HOT now. Like almost burning hot, even with gloves on. I've never ever felt that kind of heat from them since the bike was new. It's GREAT!
2 - My voltmeter used to show a slight drop, like .2V, when the grips were on, probably cuz the voltmeter and grips were on the same circuit. Now the voltmeter doesn't budge when I turn the grips on, it stays at 14V.

I highly recommend adding a relay to your grips if you don't already have one.

[Zombie Master]

I've used this company for wiring up my bikes.

https://easternbeaver.com/Main/Elec__Pr ... elays.html

I used this system to set up my dual sport bike. Easy to use:

https://easternbeaver.com/Main/Wiring_K ... cs-hd.html

Interesting good quality stuff.

[gspd]

Having recently rewired my grips directly to the battery via a relay and toggle switch I'm realizing that I need a 2 position switch now because they get so hot that I have to turn them off after a while on the type of days that I would have previously just left them on all day.

I no longer have, nor do I want to use, the OE 2 position low and high heat switch that came with the bike.
I want to install a three position (ON-OFF-ON dpdt) toggle switch.
One side would be direct for full intensity, the other would run through a resistor to cut down the heat a bit.

2 questions:
1 - What was the resistor in the OE switch for LOW heat? (ohms and watts)

I think I know the answer to this one but I'll ask it anyways...
2 - Will the power draw be exactly the same on low heat through the resistor as on high with full power to the grips?

[Airbear]

With a double pole, double throw switch you can switch between parallel (12V) and series (6V) to power the grips:

HGrips.jpg (39.17 KiB) Viewed 1113 times

FWIW, I am very happy with my Oxford Heaterz. They are 5 speed, use pulse width modulation and will switch off if the battery voltage gets too low.

[gspd]

With a double pole, double throw switch you can switch between parallel (12V) and series (6V) to power the grips

Thanks Airbear.
Sounds like a plan. Are there any downsides to doing it as you illustrated?
Sounds too easy. What's the catch?

EDITED THIS PART BECAUSE I'M HAVING BRAIN FREEZE
So the grips connected in series should put out about half the heat as when in parallel? Is that correct?
What about total power consumption.
I was thinking (ohms law?) that it should be half total current draw when in series but not sure if that makes sense.

Alternate plan B - Could one of these work for grips? any downsides?
I think with one of these the power consumption would be lower as the grip temp gets set lower. not sure.
https://www.amazon.ca/Controller-Adjust ... 9229&psc=1

[Airbear]

Sorry GS, I can't answer those questions with any confidence. Hopefully Rob F will be along shortly - he knows about electrons.

[Rob Frankham]

With a double pole, double throw switch you can switch between parallel (12V) and series (6V) to power the grips:


HGrips.jpg


FWIW, I am very happy with my Oxford Heaterz. They are 5 speed, use pulse width modulation and will switch off if the battery voltage gets too low.

I'm afraid that there is a flaw in that way of wiring things. I have done a quick generic wiring diagram to show why this isn't going to work well. I hope it is self explanatory but, in principle, arranging the loads in series will actually reduce the power output by to one quarter of that if the same loads are arranged in parallel. Please note that the figures aren't intended to represent any particular heated grips, just to show the way in which power output is affected by way the loads are arranged. In fact, the figures were chosen so that the arithmetic is simple...

series-parallel.jpg (88.38 KiB) Viewed 1056 times

Actually, the situation works for constant resistance loads but is over simplified for heated grips because of a phenomenon known as the 'temperature co-efficient of resistance' of the material used for the heating elements. As the temperature of the element increases, the resistance also increases which means that the power increase with voltage will not be linear. In effect the power output of our elements linked in series will actually be somewhat higher than 25% although it's highly unlikely to be anywhere near 50%. It depends on the material chosen for the elements.

There is also another factor to consider... If the elements are designed to run in series at 6 volts, feeding them with 12 volts is very likely to considerably shorten there life.

Rob

[Seth]

Honda does something similar with the radiator cooling fans on my 2009 Civic.
The fans run in series for low speed operation, and parallel for high speed.

https://www.youtube.com/watch?app=desktop&v=yZKb-xXdrdo

[gspd]

I'm afraid that there is a flaw in that way of wiring things. I have done a quick generic wiring diagram to show why this isn't going to work well. I hope it is self explanatory but, in principle, arranging the loads in series will actually reduce the power output by to one quarter of that if the same loads are arranged in parallel.....In effect the power output of our elements linked in series will actually be somewhat higher than 25% although it's highly unlikely to be anywhere near 50%... If the elements are designed to run in series at 6 volts, feeding them with 12 volts is very likely to considerably shorten there life.

Thanks a million for the explanation Rob, you saved me a ton of wasted time.
Airbears' schematic seemed too damn perfect, and it is for certain applications, but I couldn't understand why it wasn't universally used in all grip applications if it was so good. Why would most manufacturers use resistors or resistor wires to provide a lower heat setting? I thought that if parallel was full power, series would be half power, but now you say it's closer to 1/4, and I'm confident you know what you're talking about.

Here's where I'm at now.
1 - I've established that my grips get toasty hot wired in parallel running at 14v. Perfect!

2 - I need a lower heat setting for milder weather. The Oxford Heaterz WPM controller Airbear recommends would do the job perfectly, however I don't want one on my handlebars, mostly for aesthetic reasons.

3 - The BMW switch has a resistor wire for the lower heat position, and depending on who you want to believe it's 1.6 to 1.9 ohms resistance and power is cut down to about 75% on the low setting. The BMW grips are supposedly 8 to 9 ohms each. I haven't confirmed these figures. It would solve the problem but I don't want to use the BMW switch, it just doesn't 'fit' my dash the way I'd like.

4 - The multi use WPM light and DCmotor control boxes I've looked at are too big and mostly chinese crap, if you read the reviews. Not even sure if they'd work.

5 - My solution for now would be to substitute my current push button on/off switch with a two position mini spdt toggle switch, with one position providing full 14v power and the other position running trough a readily available heavy duty 50W 2ohm resistor like this:

50w 2ohm.jpeg (9.27 KiB) Viewed 1048 times

2 questions:
1 -Would this resistor drop the voltage from 14V to around 9 or 10 volts, which is what I need, and would it negatively affect increase actual power consumption.
2 - Would it need to be mounted on a heat sink plate or would it cool adequately if it was just hanging in the air on its own.
I'm open to alternate solutions.

Thanks again Rob.

[gspd]

Honda does something similar with the radiator cooling fans on my 2009 Civic.
The fans run in series for low speed operation, and parallel for high speed.

Thanks Seth-
I think heating elements react differently than fans when wired in series.
Something to do with 'temperature co-efficient of resistance' as stated by Rob F in his above post.