Turnigy watt meter for $25

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Turnigy watt meter for $25

Postby Hyena » Thu Oct 15, 2009 11:45 pm

I just noticed hobby city have new turnigy watt meters for $24.95
They're a blatent rip off of a wattsup meter, but with the benefit of being half the price and look to be backlit.
According to the specs they'll read up to 130a but only 60v. Still, for those of us running lower powered bikes they'd be a good option - perfect for 12S lipo setups I'm planning to do for a few friends!

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Re: Turnigy watt meter for $25

Postby 1000w » Thu Oct 15, 2009 11:59 pm

Nice find Hyena.
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Re: Turnigy watt meter for $25

Postby amberwolf » Fri Oct 16, 2009 12:06 am

Interesting in that it could also use an auxiliary battery to power itself from--that should bypass that 60V limit for those running higher packs? Doesn't explicitly say that, though.
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Re: Turnigy watt meter for $25

Postby Hyena » Fri Oct 16, 2009 12:16 am

I think the rating of the internal components are the limitation there amberwolf.
wattsup meters are rated at 60v and can similarly be powered from an external source but will let out the magic smoke it you put 70v in.
They're ok for a bit over 60v though, mine has been fine for 6 months with my 15S lipo pack at close to 63v off the charge.
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Re: Turnigy watt meter for $25

Postby philf » Fri Oct 16, 2009 6:09 am

The voltage limit on the WattsUp meter comes into play in more than one place in its design. The obvious one is the voltage regulator. It's built on a component with an upper limit of 60V. It seems easy to put an external power source on the thing to remove this limitation, but the gotcha is in the voltage divider used to feed the ADC on the microcontroller (to provide a voltage reading). The resistor values used are intended to give maximum resolution to the ADC within the device's 60V operating range. The micrcontroller won't tolerate inputs that are too much above its own power supply (I believe the WattsUp internals runs at 3.3V), and this is why it'll smoke if you keep increasing the voltage too far. In all likelihood, they're using a voltage reference which is a bit less than the device's 3.3V to scale the ADC (probably closer to 2.5V), which means there's probably SOME headroom before the device fries, but the accuracy of the reading you get once the ADC is saturated will probably make it meaningless.

The WattsUp *is* a marvel, though. Considering its shunt is only 1 milliohm (giving 1 millivolt per amp) and that there is NO external amplifier used, it was poser to me how they were able to get the resolution that they do with any accuracy. This prompted me to download the specs for the microcontroller they employ (one of Atmel's AVRTiny series), and that unlocked the mystery. I'm guessing they're using differential ADC, and the chip has its own ability to add 20X gain. This, in conjunction with a bit of external dithering, as well as oversampling/decimation in their code, gives the device way more sensitivity than hardware alone is capable of. Pretty cool.
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Re: Turnigy watt meter for $25

Postby ZOMGVTEK » Fri Oct 16, 2009 8:26 am

Wow, very nice...

I was amazed at the accuracy of the watts up with its negligible effect on the overall system. Normally the shunt would actually have a somewhat noticeable voltage drop at 60A and 48V... But the only real effect this has is its 14AWG wire gets toasty! I ran over 100A in my RC car, through it even though its only rated at 50 or 60A, and its amazingly accurate...

This looks like the exact same thing, except it has the one feature I wanted, a backlight! If the watts up plastic casing wasn't welded, I would have put a backlight in by now.
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Re: Turnigy watt meter for $25

Postby Rifle » Fri Oct 16, 2009 12:25 pm

Has anyone tried this? I know a month or 2 ago someone found a Wattsup equivalent for about this same price, but when someone ordered it, it didn't work. It was definitely a different meter than this though.
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Re: Turnigy watt meter for $25

Postby Hyena » Fri Oct 16, 2009 5:54 pm

ZOMGVTEK wrote:This looks like the exact same thing, except it has the one feature I wanted, a backlight! If the watts up plastic casing wasn't welded, I would have put a backlight in by now.


Likewise.
I'll probably grab one with my new order.
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Re: Turnigy watt meter for $25

Postby StudEbiker » Fri Oct 16, 2009 6:23 pm

Thanks for posting, I'll be ordering one soon!!
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Re: Turnigy watt meter for $25

Postby SpeedEBikes » Fri Oct 16, 2009 10:27 pm

I ordered one several days ago. With luck it will be arriving soon. I've got 3 wattsup meters and it will be good to have a cheap equivalent.

btw, I've done some stupid things with wattsup meters. Plugged them in with reverse polarity, accidentally given them serious over voltage, even once momentarily shorted one while at 58 V, blowing both 30 amp fuses on the two 29 V packs. Never smoked one. They are pretty tough. Operating them at 0 F the screens go dead but internally they still seem to be working ok even at -20 F. Between 32 F and 0 F the screens get increasingly sluggish and dim. Probably a common property of lcds although I hadn't noticed it with anything else before.

Anyway, I wonder if the Turnigy will prove to be as robust, maybe the backlit lcd will have a bit better low temp performance.
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Re: Turnigy watt meter for $25

Postby Hyena » Sat Oct 17, 2009 12:03 am

SpeedEBikes wrote:I ordered one several days ago

It'll be nice to hear a comparison with the wattsup from someone who has both. I thought it was going to be me, but if you've already got one on the way it looks like you're it! :)
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Re: Turnigy watt meter for $25

Postby DerekG » Sun Oct 18, 2009 12:02 am

SpeedEBikes wrote:I ordered one several days ago. With luck it will be arriving soon. I've got 3 wattsup meters and it will be good to have a cheap equivalent.

btw, I've done some stupid things with wattsup meters. Plugged them in with reverse polarity, accidentally given them serious over voltage, even once momentarily shorted one while at 58 V, blowing both 30 amp fuses on the two 29 V packs. Never smoked one. They are pretty tough. Operating them at 0 F the screens go dead but internally they still seem to be working ok even at -20 F. Between 32 F and 0 F the screens get increasingly sluggish and dim. Probably a common property of lcds although I hadn't noticed it with anything else before.

Anyway, I wonder if the Turnigy will prove to be as robust, maybe the backlit lcd will have a bit better low temp performance.


Yep, that's just the way it is with lcd screen :-)

I've rode with my CA down to about 25 degrees F so far and I notice a little "ghosting" on the screen although it's hardly a problem... just something to be aware of. Even my Garmin GPS's display got sluggish when I went out at 5 above last winter

As far as the backlight goes, I would think it should run in the cold although that too will be dimmer.
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Re: Turnigy watt meter for $25

Postby SpeedEBikes » Sun Oct 18, 2009 10:28 am

Mine was shipped out a couple days ago but is still not here yet. I'm in the US and you are in Australia so you might still win the race to post the first review.

Hyena wrote:
SpeedEBikes wrote:I ordered one several days ago

It'll be nice to hear a comparison with the wattsup from someone who has both. I thought it was going to be me, but if you've already got one on the way it looks like you're it! :)
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Re: Turnigy watt meter for $25

Postby Little-Acorn » Sun Oct 18, 2009 11:23 am

Please forgive a newbie question. But can this meter be installed permanently on an ebike? (Or is that the whole idea?)

Sounds like the ampere-hour meter is a good "fuel gauge", at least to see how much "fuel" has been drained out of your battery. I assume there's a way to "reset" it after charging the battery, and/or when starting a trip?

Maybe it can also tell you that those 15# SLA batteries you've been lugging around, rated at 18AH, are dying after only 11 AH, too.

And the ammeter can tell you how much you're drawing right now, a measure of stress on hills, level ground etc?

Voltmeter is handy for telling when your battery gets low, or when you're pushing it too hard up a hill, right?

Are those the general uses for a meter like this?
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Re: Turnigy watt meter for $25

Postby amberwolf » Sun Oct 18, 2009 2:50 pm

Yes, to all.
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Re: Turnigy watt meter for $25

Postby SpeedEBikes » Mon Oct 19, 2009 1:34 am

amberwolf basically nailed it, but I'll fill in some details.

First, I've only been using the wattsup meters and not yet the Turnigy meter although I expect it will be very similar. The meters are very simple only having positive and negative source leads and load leads. The only distinction between the source and load is that it only tracks current flowing from source to load. You can pass current through it backwards and it will show zero current and no effect on the accumulated amp hours.

The meter can be powered off either the source or the load leads. As long as it is powered it will accumulate amp hours and will retain all stats like peak current, peak watts, etc. When powered off everything resets. The power draw is fairly low, so it isn't a big deal to leave them connected for long periods of time although I definitely wouldn't store a battery with one connected.

You could probably permanently mount one permanently on your bike, but I wouldn't. I've yet to have one damaged by weather, but I'd be surprised if they are 100% waterproof. I put self stick velcro hook tape on the back of mine and I put the mating velcro fuzzy tape in a bunch of places like on top of my controller, on the out side of my battery boxes, on a small plastic panel mounted on my handlebars, etc. Thus I can put one or more meters where ever I want. I used to always carry around a multimeter but now I usually just carry one or more of these things. For whatever sort of plugs you put on the meter it's handy to rig up some adapter cables with jumper clips, probe tips, bannana plugs, etc. so you can attach the device to whatever you like.

I really like to be able to see the voltages of all my batteries, chargers, power supplies, etc. and check whats on each side before connecting things together. Without checking it's easy to make mistakes. I also like to see when current is flowing and how much is flowing. When riding I like to be able to monitor my weakest pack to know how much juice I've got left. Frequent checking and monitoring will often let you spot trouble before it gets bad.
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Re: Turnigy watt meter for $25

Postby philf » Mon Oct 19, 2009 6:15 am

SpeedEBikes wrote:I've yet to have one damaged by weather, but I'd be surprised if they are 100% waterproof.


Actually, that raises an interesting point... Looking at the picture posted at the beginning of this thread, it looks like the Turnigy actually has a plastic window in front of the LCD. The Watts-Up meter DOES NOT. It's just an opening in the case, and what you're seeing is the face of the actual LCD module itself - not a piece of protective plastic. This case definitely ISN'T waterproof. Water pooling on its face will run inside. The Turnigy might actually fare better at this...
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Re: Turnigy watt meter for $25

Postby Hyena » Mon Oct 19, 2009 8:31 am

Yep, I have mine permanantly mounted on my handlebars and have had it fog up when I occasionally get caught in the rain.
I've also got a splash of solder in the corner of the screen that I can't get off, I think it's eaten into the screen and glued itself there!
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Re: Turnigy watt meter for $25

Postby nwmtnbiker » Wed Oct 21, 2009 8:57 pm

I have a question, I'm about to order the Turnigy watt meter. I installed the Currie conversion kit on my mountain bike so I've got a center off toggle that allows me to choose between 2 separate 24V batteries in the Rack Mount System. Right now I've only got one battery but that will change by next spring (if not sooner). I'm trying to figure the best way to wire in the watt meter so it will provide information for the battery that I've got toggled on, but I thought I'd ask the experts here for some advice since you're all more knowledgeable than I am in all things electronic. Here's a wiring diagram showing the wiring from the switch to the batteries and the controller. Thanks in advance.

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Re: Turnigy watt meter for $25

Postby Hyena » Wed Oct 21, 2009 9:32 pm

You'd wire it between the 2 blue connectors you have indicated going to the controller.

Why dont you run the 2 batteries in parallel ? It'd put less stress on each individual pack and you'd probably get a touch more range.
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Re: Turnigy watt meter for $25

Postby nwmtnbiker » Wed Oct 21, 2009 10:53 pm

Heyena,

Thanks for responding. So the red and black wire from the source side of the watt meter would be wired to the red and black wire on the switch side of the blue connector and the meter's load wire would be wired to the red and black wire on the controller side of the blue connector? (Sorry to be so dense about electronics.) I haven't done any mods on the basic Currie kit. Currie has set up the on/off switch using a center off toggle that the user must flip to the left or right, depending on which battery will be used (Currie's Rack Mounted Battery system allows the user to have two batteries but the kit comes with only one battery so I suspect they may assume that many people will only operate the bike with one battery but have created the option to mount two). I suspect at some point next year I will move the on/off switch to an area where I can reach it while seated on the bike (it's default location is at the end of the rear rack). At that point, I might drop the center off toggle configuration and wire the batteries in parallel.
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Re: Turnigy watt meter for $25

Postby amberwolf » Thu Oct 22, 2009 1:43 am

As soon as someone gets hold of one of these, I'd love to see the inside of it, especially the shunt, because I have a way I'd like to use such a meter that I must be able to replace that shunt with a different one:

What I want to do is have a "fuel gauge" for the pack Ah that counts up to the full capacity as I charge up the battery (it's ok if it's a negative number), then counts down to zero as I use it up. It ought to be easily possible with the Cycle Analyst, AFAIK, but I don't know enough about this one to tell if it would work.

The only three requirements are that
A) I can use my own shunt
B) the meter will read regen current as negative
C) that it will go into negative Ah
If it won't do C) I'd have to reverse the current thru the shunt so it reads negative during *use* instead of during *charge*, which is fine with me, but it does still require that it will count backwards as regen current passes back thru the shunt.

I have to be able to use my own shunt because the charging shunt is different from the discharging shunt, so that it makes up for the fact it takes more power to charge the batteries than I get back out of them. Like the old electromechanical EV meters from early last century.

I'm working on a way to do this electromechanically with recycled parts, but haven't got the idea worked out yet. If I can do it in one of these meters, that would be great, once I can afford one, as it is likely to be more reliable than my own contraption. ;)

Basically I don't want to have to "know" how much power a particular pack has in it, and subract that out manually for myself. I want it to count down automatically. Sure, I know it's not fully accurate, because of Peukert effect (especially with the SLAs I use), but it is easier than the other method.

I experiment with different packs sometimes, built of different combinations of different sized SLAs, and I don't want to have to remember which pack is on there which time. I want to just stick the appropriate charging shunt in there (if more than one is needed, which is likely), rundown the pack, recharge it, then go do whatever testing/riding/etc. and be watching it count down to zero on it's own.

One advantage of this kind of metering system is that since the batteries aren't ever fully discharged, I'm only metering what I put in, so that while I might indeed have power left when I get to zero on the meter, I can plan my trip and driving/riding style by the amount it *shows* I have left. :)

Using the idea of resetting the Ah usage meter as it normally would be used by most people, whenever starting out on a ride with a fresh charge, then keeping in mind the "known" capacity of the pack, and subracting as you go, may end up wrong easier (for me, anyway).

Better to think you're running out of gas and have half a tank than the other way around!
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Re: Turnigy watt meter for $25

Postby Hyena » Thu Oct 22, 2009 8:52 am

Amberwolf your intentions sound a bit convoluted!
AFAIK wattsup meters don't read current going the other way, hence the would not be able to capture regen if these devices are the same.
You could possibly run 2 though, one connected with the motor as the source and the other connected wtih the motor as the load. Its a bit of double shuffling though. I wouldnt have thought they'd be super useful with teh pekeurt effect on your SLAs anyway.

Also re: measuring the ah going back into a battery when charging, I dont think that's terribly accurate. I've only measured once or twice but I noticed that a full battery with say 4ah used from it would then take about 5-6 ah to recharge.
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Re: Turnigy watt meter for $25

Postby amberwolf » Thu Oct 22, 2009 3:53 pm

Hyena wrote:Amberwolf your intentions sound a bit convoluted!

The end result is simple, but I usually find I must fully explain my reasoning, as what *I* want out of things doesn't seem to be what almost anyone else does, and they have a really hard time understanding why I would want to do whatever it is. :)

AFAIK wattsup meters don't read current going the other way, hence the would not be able to capture regen if these devices are the same.

I expect they probably ignore negative flow, but I don't know for sure. I know the CA responds to it, but I don't know how it's meter counts (it *should* count backwards for charge current, but it might not be programmed that way).



You could possibly run 2 though, one connected with the motor as the source and the other connected wtih the motor as the load. Its a bit of double shuffling though.

Running two would force me to do the math between them just as if I had to carry a piece of paper with the "full charge" on it. Only better in that it would show the actual charge put in each time (in case of not having time to fully charge, opportunity charging, etc). Plus it would cost twice as much, and I don't even have money for rent/bills now.


I wouldnt have thought they'd be super useful with teh pekeurt effect on your SLAs anyway.

That's something I just have to deal with by determining my ride style with a pack over time, and factor in a correction using the charging shunt.

Also re: measuring the ah going back into a battery when charging, I dont think that's terribly accurate. I've only measured once or twice but I noticed that a full battery with say 4ah used from it would then take about 5-6 ah to recharge.

That's taken care of with the center-tapped shunt, with different values for the charge and discharge sides. The discharge side is left 1:1, and the charge side is made as a ratio to compensate for the difference between the input Ah and the expected output Ah, preferably based on the expected usage style (heavy draw, medium, etc) and type of battery (SLA, LiPo, etc) since those things greatly affect how much actual power will come back out of them.


Ideally, a charge/discharge curve could be created within the meter itself, so that it's software would do the compensation with only one shunt. If the current is positive it uses the discharge curve, and if it's negative it uses the charge curve, since it would be the same for regen or for normal charging. With meters like the CA, the menu system could be used to tell it whether to use a curve for SLA , LiPo, LFP, NiMH, NiCd, etc. Assuming there's room for that kind of data table within the MCU's flash. :)

But that kind of thing would have to be done as a completely new bike computer project, since I don't think Justin has the time (or probably motivation) to add something like this to the CA for the few people that would probably care about it. (I haven't suggested it to him for that reason). For normal people, the CA already works well enough; just not quite what *I* want, or possibly a few others like me.
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Re: Turnigy watt meter for $25

Postby SpeedEBikes » Thu Oct 22, 2009 6:47 pm

Amberwolf, just get the watt meter and start using it. Fully charge up your batteries and go for a ride. Every few minutes stop and write down how many amp hours you've used and what your voltage is. Run it down to near your cutoff voltage. Then using the data you've collected, work it backwards such that you have a figure for how many amp hours remaining at each voltage point. If you use many different batteries and your memory is fading then print the data up and tape it to your batteries. Then you'll have a pretty good guide for how much capacity you have at any voltage. If you only use a single set of batteries you won't need to be that thorough. Just ride around paying attention to the meter. Fairly quickly you'll be able to glance at the voltage and know from past experience how you are doing for energy remaining. For battery types with flat portions in the discharge curve, such as NIMH and LiFe the amp hour meter is more needed, but for sla and lipo/li-ion you can get by fine with just a volt meter.
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