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where can i find a small/low power amp hour meter

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jpoopdog

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as in one which records actual AH [ Amp Hours ]

not an ammeter/ampmeter, an amphour meter.

its quite tricky to search for specifically and few results come up, but generally they are for mains and such.

i really need one of these however, i have multiple tests i want to perform which require this information.

I would imagine i could do it with an osciloscope, maybe, but im not up for buying one quite just yet even if it only costs $400-500 for the one im after.

if there are no cheap chinese standalone models is there some cheap circuit i can hook up to my computer via usb or VGA input (i have a laptop) or if really need be, my old packard bell pc which DOES have parallel , or to my raspberry pi or my 3d printers printrboard, whatever is most convenient/cheap, so that i can use my computer to monitor amp hours and/or watthours?

the two immediate tasks i have are to do a lifespan test on some small sample strips of overloaded MMO mesh, electrolysing a "gentle" solution, to establish a graph indicating the runaway point at which what power causes the coating to corrode unnaturally fast (its platinum substitute plat group metal oxide).

the other is in buying a cheap usb 20Ah power bank, my old one died but im not sure it truely was 20ah, so i want to test it for sure, and if it turns out its not, if its not even 10Ah, ill demand a refund and end up with a free <10Ah powerbank and ebay sellers will stop selling the fake powerbanks.


So, whats my best option or is there a relatively affordable product out there?

my voltage range and amperage range is going to be <20v and <15A
 
Start having a look at a good chandlers, you can get ah displays for marine batteries.
 
Do you want to measure A and Ah when A increase x% and stop the test and save the Ah result? or digitize the Ah & A results and analyze later?
 
kinda, but the exact opposite.

you know how houses have power meters (usually a dial) i want something like that, which would display either amp hours or if need be i would tolerate watthours.

like the way a pedometer says how far youve walked or a car odometer says how far youve driven.

in any case i think ive found one but now its moreso a matter of finding one which can definitely take 5v or less
 
I think this is what you are looking for but don't think it will go below 5 volts. Might if you use a separate battery to power the meter.
**broken link removed**
 
Because AmpHours is includes time, your measurement needs to be done over time as well.

If the load current is constant, then you only need an ammeter and a stopwatch. But if the current varies over time, then you'll need something that constantly samples the current at a known period, then integrates the results.

I would start with some sort of Data Acquisition hardware like a LabJack. Then find or write an application that samples the current every second, or at whatever rate you feel is necessary. Dividing that measurement by 3600 will give you AmpSeconds. Add all of those samples up for an hour and you will have your answer in AmpHours.
 
I can mod this to do it for you...
https://hackaday.io/project/1375-lead-acid-ah-capacity-testerlogger

It would need a more advanced menu system to permit setting the 'trip off' min. batt voltage instead of just using the fixed 10.5V for 12V lead acid batts. Also a separate 12V supply instead of drawing from the battery under test.

It stores a datalog in the Eprom of up to 250 voltage samples taken every 225 seconds to make up about 16 / hour. Upload to an Excel compatible text file via rs232 over USB. It also stores the overall avg amp rate and the total Ah measured.
The display also shows the running AH total during the load test. I suppose for lower voltage batteries , 6 volt lamps could be used as the load. The 12v lamp load would still work (not glow) for a lithium batt, but the max load will drop to about 3A or so given the lamps' resistance.
A bit of nichrome wire could substitute as the 'lamp' load for low voltage testing.
 
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