Cheap Power Meter Mount

[Deleted member 4366]

I just thought I might share this idea with you. I bought a power meter and was wondering how to mount it until I looked at my iphone mount which was nearly the same size. I warmed up the clips with a heat gun and was able to bend them so that the meter clipped in perfectly. The mount cost £2.37 inc. postage from Ebay:
Bike Bicycle Handlebar Mount Holder For iPhone 3G 3GS on eBay (end time 09-Oct-10 18:46:54 BST)

Installation picture: SANY0025.jpg picture by d8veh - Photobucket

I have yet to finish insulating the wires. I have tried it out and was surprised to see that my Bafang 250watt motor gives over 600 watts up steep hills. One hill was a mile long and continuously steep. The motor didn't drop below 500 watts all the way up. It used about 2AH just for this one hill.

 

[fishzx7r]

I just thought I might share this idea with you. I bought a power meter and was wondering how to mount it until I looked at my iphone mount which was nearly the same size. I warmed up the clips with a heat gun and was able to bend them so that the meter clipped in perfectly. The mount cost £2.37 inc. postage from Ebay:
Bike Bicycle Handlebar Mount Holder For iPhone 3G 3GS on eBay (end time 09-Oct-10 18:46:54 BST)

Installation picture: SANY0025.jpg picture by d8veh - Photobucket

I have yet to finish insulating the wires. I have tried it out and was surprised to see that my Bafang 250watt motor gives over 600 watts up steep hills. One hill was a mile long and continuously steep. The motor didn't drop below 500 watts all the way up. It used about 2AH just for this one hill.

Hi mate I was thinking of getting a power meter for my bike, but being pretty useless at electrics I have so far gave it a miss,
is it very difficult to wire, some pointers and diagrams would be helpful if you think it could be done by a layman,

Rob

 

[Deleted member 4366]

Fairly straight forward, but requires soldering. All the power goes through it so all connectors should be soldered rather than crimped. If you want one like mine it was £18 inc postage from E-bay: Search for Watt Meter. It comes with a short piece of wire with two soldered connectors . I unsoldered these to use later. They are the red connectors that fit in each end that you can see in the photo. Next point is that you need thick wire. I don't know what is ideal, but I used wire from the flat grey ring main type - I would guess about 30 amp. After that all you need to do is find your main battery connection (probably in your controller box), pull it apart and then solder similar connectors to the ends of the thick wires and run it to and from the power meter. making sure that you keep the positives and negatives the right way round. If you can't match your battery connector, cut it off and use good quality bullet connectors. As my bike doesn't appear to have a fuse between battery and control box, I soldered in a replaceable 20 amp car-type fuse while I was at it. Another thing to consider would be to make additional connections near the control box so that if anything goes wrong with the external wiring or meter, you can unplug it and bridge the wires. That's about it. If you decide to go ahead with this mod and/or need any more help,please ask again.

 

[NRG]

Don't forget if the battery is rear mounted you are inserting approx 2m of extra cabling with associated losses and inductance between battery and controller, by all means do this as an experiment to monitor under different conditions but best if the battery leads are short as possible.

 

[fishzx7r]

Cheers for that D8evh.
Might give it a try when I'm feeling a little braver, also mate what bike are riding,the back battery box looks the same as mine,

 

[Deleted member 4366]

More often than not, the battery is at the back of the bike and you need the meter where you can see it when riding. So, you don't really have a choice with the length of wire. That's why I said you need thick wire. In my installation, there is no measurable or noticeable reduction in power from the 5 meters of 2.5mm sq. wire. I calculate the loss from the wire (0.02 Ohms per meter, 5 m = 0.1 ohm) is approx. 4 watts at 6 amps (250 watts) and 15 watts at 12.5 amps (500 watts) - if I've done my sums right for for my 40v Sunlova bike. When you can see how many watts you are using, you can see how to ride more power-economically, so you can easily save the few watts that you lose.

 

[daniel.weck]

More often than not, the battery is at the back of the bike and you need the meter where you can see it when riding. So, you don't really have a choice with the length of wire.

The Cycle Analyst has an optional remote shunt sensor...but it's not a cheap power meter.

The Cycle Analyst Homepage - Ebike Amp-Hour and Watt Meter

 

[vhfman]

Monitoring power usage a with meter is a good idea. And as Daniel mentions the Cycle Analyst has remote shunt resistor option, which means that you can run lighter gauge wire to the handle bar mounted meter. Unfortunately the CA is quite expensive @ £120 +, so if you are using the RC model types that do not have a remote sensing shunt resistor. Then heavy gage wire has to be used between the battery through the meter to the controller.
I would not be happy using solid core 2.5mm wire on any vehicle where it is subject to vibration and constant flexing. Especially round the handle bar to frame area. I think in the long term you should replace the solid core stuff with some multi strand wire, like auto or RC (14-10awg) wire which is much more flexible, so should not work harden and fracture.

Or if you are adventurous with the soldering iron, then I read an item on ES by Jeremy Harris about modifying the Turnigy 130A power meter to give remote shunt monitoring.

Endless-sphere.com • View topic - Mounting Turnigy Watt Meter

 

[Deleted member 4366]

VHFman, Thanks for that. I guess mine is similar inside, so I might see if I can copy that mod when I get a bit of time. In case of problems with the wires breaking, I made sure that I used connectors such that I can unplug my meter wires and restore the previous connections at the roadside. You're also right about the danger of the single strand copper wires breaking due to fatigue. I have tried to arrange the wires so that they get the minimum amount of movement. I estimate they will last a few months or more, by which time I will probably have changed something.I agree that high quality stranded wire would be better, but I didn't have any to hand. So, if anyone else is reading, don't copy me - use decent stranded wire.

 

[Deleted member 4366]

Thanks for the link VHFman. I have now done this modification. I disassembled the unit, then the most difficult bit was unsoldering the LCD. It might have been possible just to bend it out the way, but I thought it safer to unsolder it, as I have a good solder sucker. Underneath the LCD were two shunts. They're like two long peices of thick metal wire. I unsoldered the two shunts, power connectors and the piece of plain copper wire which connects the -ve directly between them, then I soldered the shunts and the piece of copper wire directly to the connectors, and finally 4 thin wires out of an old serial cable to this assembly: one to each end of the shunts and a + and - to the battery side connector. I connected the other ends to the corresponding positions on the circuit board from where I removed the components. After re-assembly and installing the shunts next to the controller, everything worked perfectly, with similar readings to what I had before. I think the only thing to look out for would be not to get two much solder up the shunt wire because this has the effect of shortening it and changing the readings. I have ordered another meter for my other bike and will take some photos next time if anybody is interested.