Backyard Aquaponics
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I bought an in-line watt meter for $15 from eBay that just has a + and in and the same out. It has an LED screen that shows lots of nice info. Some of it I don't understand.

So for eg, my display is connected to my old 100 AH deep cycle lead acid battery, and running my trolling motor in a bucket of water on speed 2 of 5.

Battery voltage 11.18 V
Amps that the load is drawing 9.41 A
Watts that the load is drawing (is that the right language?) 105.2 W

But I'm not sure what these other things are telling me (the numbers might not add up exactly because the draw was changing a bit as the display was scrolling between the different info)...

16.1 Wh

1.516 Ah

I know what amp hours and watt hours are, but I have no idea what it's trying to tell me about them.

363.2 Wp (might be peak watts because that's about right for speed 5 of 5 on the motor (By the way, Yay!!! that means I can cruise all day on my existing solar set-up - I wasn't sure until today what the motor would draw)

9.90 Vm (Might be minimum volts as that's probably where my tired old battery dropped to when I ran the motor flat out.)

35.94 Ap (Might be peak amps because that's about right for flat out as well.)

I'm guessing a watt hour and an amp hour would be a measure of capacity but I have no idea what this thing is trying to tell me.

Is this telling me I have 1.516 Ah left? If so my battery is in worse shape than I thought.

The battery was showing 12.5 V without load, 10 minutes after the load was removed, then dropped to 11.18 with a 9.41 amp load.

what make and model is that device, it sounds very nice. Love getting new tools, and having to figure them out. What i like less is having to read the itty bitty manual. You've probably seen these before, but I like reminders, as I don't have space in my head to remember things from college some 25 odd years ago

Manual!

Clearly you shop in better places than I do

It came with a slip of paper telling my how good it's thunder protection was

No name or model number, but it did come with a sheet of paper. It says it reports Amp hours and Watt hours, but doesn't tell me what they are telling me.

From those numbers, can you tell if the Ah and Wa numbers are telling me the remaining capacity of my battery?

Posting a link to the actual product is a bit pointless because in another month it probably wont exist, but as of today, the following google search brings up some images of small blue boxes that look like mine...

https://www.google.com.au/webhp?sourcei ... r+60v+100a

I found this extra info on another listing but I still cant tell if the Ah and Wa readings are telling me the capacity I have left or something different.

Does anyone have any idea?

How could a device like this work out the capacity of my battery (if that's what it's doing) without draining it with a known load and seeing what it does? Putting a load small enough so that it wouldn't cost too much in battery power would surly not be relevant to a real world load and the behaviour a battery would show.

I wish everyone on earth would just presume they were writing for me and pitch their information and documentation accordingly

-----------------------------------------

Introduce:
Professional RC Watt Meter is an excellent addition to your RC hobby, DC circuits, Solar system, Boat/RV & Battery Backup systems!

This isn't just a watt meter-it's the All-In-One Meter! A power meter, a volt meter, an amp-hour meter, ammeter and energy meter. Everything all in one unit! This is the perfect troubleshooting tool. This all-in-one watt meter is indispensable for analyzing, testing and troubleshooting any DIY DC power project.

Feature:
100% Brand new and high quality.
Digital LCD screen gives clear crisp number readings.
Handles up to 100 amps intermittently and 50 amps continuous duty.
Connecting load end to the battery provides real-time battery charging reading.
Handles 0 to 60 volts. Works on 12, 24, 36, and 48 volt battery bank systems.
Extremely low power consumption of 7 mA. More efficient than any LED meter.
Measure energy(wh),charge(ah), power(w),current(A) and voltage(V).
Accurate & precise 0.01 A current and 0.01 V voltage resolutions.
Measures peak Amps, peak Watts(except for Doc Wattson) and Voltage minimum(sag).
Rugged- handles 50A continuous and 100 A peak at 60V.
Acts like a wire so doesn't affect model's performance. Precision Alu-Chrom current sensing resistor, with only 0.001 Ohms resistance and circuitry that draws only 7 mA.
USes DSP to increase ADC resolution and differential measurement amplifiers to increase noise immunity.



Specifications:
Color:Blue
Voltage:(0)V-4V-60V 0.01V (Resolution).
Current:0-100 A peak 0.01A (Resolution).
Power:0-6554 W 0.1W (Resolution).
Charge:0-65 Ah 0.001Ah (Resolution).
Energy:0-6554 wh 0.1 Wh (Resolution).
Measurement Update period:400mS.
Signal Sampling Rate:sample/s.
Data Queue Sequence time: 2 seconds.
In Circuit Resistance:0.001 Ohms.
Operation Current: 7 mA.
Auxiliary Power Voltage: 4.0V ~ 60V
Size:8.3cm x 4.7cm x 2cm - 3.27inch x 1.85inch x 0.79inch
Display Screen: 1602 STN LCD

so they suggest, but I'm skeptical. The better battery monitor systems data log over a full cycle of the battery charge and discharge before they suggest how much is left. This one seems to guess how many amp hours the battery has, then use the power formula to calculate something from amps over voltage, as I said the volts drop as the load rises. We don't really need a meter to tell us we're smoking our old battery by running the trolling motor full-till into the wind and against the current as we head into a lake, right?

Always wanted to have my very own solar system. True egocentric thinking

Is there some method of entering information, such as brand new battery amp hour rating? Otherwise it is a very rough guess. Even the data log full charge cycle estimates are guesses, albeit more accurate

Not that I can see.

Perhaps they just use a dump load like a heating element or something for a zillionth of a second every few minutes to see what the battery does.

Is there anything else Ah and Wh could mean other than battery capacity?

I can't think of anything else while a load can be thought of in terms of amp hours it isn't because the power switch throws a monkey wrench into the equation. Many measuring techniques used in the electronics industry have nothing to do with what they measure. For example to control the current in a flooded cell battery, designers add cost of manufacture into the technique and came up with a brilliant way to keep current flow steady. They put a thermister (a resister that changes resistance with temperature) in the circuit in series. They know the relationship between current flow and temperature rise and the thermister simply shuts off the current, this creates something called duty cycle (Off time compared to On time.) http://en.wikipedia.org/wiki/Thermistor Time for me to go to work, I hope this helped

Is there anything else Ah and Wh could mean other than battery capacity?

Hi Mr B
I am so happy that your meter is blue. I think calming colours are important when Volt amps or watts are important.
Two thoughts for your epic adventure. Can you take one of those GPS thingies with you. We could then track your progress. I once watched a turtle cross The Pacific via a GPS thingy. I must confess that the best bits were when he went the wrong way but I don’t think that is relevant in your case.
Secondly, and on a different level. If you get ten hours of sunshine and do say ten miles. Good! If you get two and do two. That is also good.

I'll have a gps to show me where I am, and I hope to take a time lapse record of the entire trip so the river will have street view.

If I can I'll upload the days pics that night. Also if I can I'll have the geo-tag info on them so that will also be a record of where I am.

There's an iPhone app called trigger-trap that can do it, but I'm not sure if it will work on my old iPhone. The plan is to just silicone it so it points backwards, plug it into a power source, and leave it running.

Yes, how much you have used.

Doh!