I'm just completing a controller and battery upgrade on my Giant Trance conversion and I've run into a problem.

 

I'm permanently installing one of those cheap Ebay wattmeters, the GT Power RC.

 

The 48v battery, BMS S12S sine wave controller, and MXUS cassette motor are all working fine, but the wattmeter is flashing on and off.

 

When the power is first switched on it starts up ok and shows the figures for a second or so, then flashes the backlight but the display letters disappear.

 

When it's switched off, the numbers reappear briefly, but then fade away, (as they would when switched off).

 

I'm thinking that the BMS in the battery is maybe pulsing the output ?

 

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I've not come across that before. Does it work with any other battery controller combination?

I'll try connecting it up to my 36v 10ah lithium battery and report back !

 

Strange though, the BMS controller LCD display works fine, with no flashing, and all of the S12S controller functions work ok, (throttle, PAS, and brake cutoff).

I've just tried hooking the wattmeter and S12S to my 36v lithium battery.

 

I'm now wondering if my wattmeter is faulty.

 

It's a different problem to what happens with the 48v battery.

 

Instead, it does show the figures, but some of the characters are flashing in a sort of "negative" image.

 

It's difficult to describe, but the figures are sort of "haloed" with a flashing bright fringe.

 

Once again though, the S12S controller, LCD panel and motor work perfectly on the 36v too.

Yup - it's fooked.

Open it up and check the solder joints of the main wires to the PCB. It looks like the connection is breaking down under load. Check your connector solder joints too - maybe first.

Ok, will do, Dave.

 

It's a new watt meter, but I'm pretty sure that when it arrived a couple of weeks ago that I quickly tested it by holding the "source" red and black on a 12v battery to make sure it lit up ok before giving ebay feedback.

 

Since then I did open it up to fix it to an angle bracket, and also divert the cable entry points into its plastic case. They were either side, and I needed them to turn straight out of the back instead.

 

I'll open the case and see if it's me that's "fooked" it.

 

It is actually the second unit that I've bought from the same seller, and the other one is fine. I set that one up with a variety of interchangeable input and output connectors, and it's very handy to check how many Ah it takes to recharge my 36v batteries after various rides.

I've opened it up and looked over the solder joints carefully. The main pos and neg wires are a bit scruffy, not a clean shiny blob, and quite a bit of dried flux.

 

I desoldered the leads and removed the excess with a solder sucker, and then tested the source contacts directly to various voltage batteries.

 

I was unlucky that I only tested it at 12 volts when it arrived, (and then put it back in the box till this project).

 

It works perfectly at 12 volts and 36 volts, but has the flashing problem with the new 48v battery.

 

I then opened up my original GT power meter (exactly the same model, from the same ebay supplier, about a month before), and it works perfectly on all of my batteries, including the new 48v.

 

I must have just been unlucky (again !), and it was dodgy from the start.

 

It's a good job they're so cheap to buy. Incredible value, even at BTGOTW rates. (buy two, get one that works).

Jeez! You don't get a lot of luck!

Maybe I should switch my login ID to eJonah....

 

(though my latest BMS order came very quickly and all seems to working fine, I've always been "lucky" with them.)

Here's the live solder joint on the power meter that was flashing.

 

It looks a bit "dry" with flux lines rather than a clean blob. I desoldered it and sucked the solder off, but the meter still flashes when connected to 48 volts, (though 12v and 36v display ok.

 

I guess as Dave said, there's something else breaking down in there as the voltage rises. (They're supposed to be suitable for up tp 60v 130 amps).

 

I opened my other GT meter and the solder joints were much better, and that does work ok with 48 volts, so I've wired that one in to my new 48v pannier bag mount, and have ordered another GT power meter via Ebay ( £12.50, delivered). I use that one with a variety of interchangeable leads, and it's very handy for checking how many a/h it takes to recharge after a run.