hi, anyone know of any device that can help me check the life and the rating of my rechargeables? like something that will enable to let me know the amount of charge left and the mah of the batteries? And where would i be able to get them and the cost?
rechargables
- Thread starter lordpain
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A multimeter cannot tell you much.
The capacity is usually marked on the battery. To measure that you need an elaborate setup, as you have to fully chrage the battery and then discharge it with a fixed current while monitoring the output voltage.
Once you have the discharge curve (voltage versus mAh already drawn) then you can estimate the remaining charge by a simple voltage measurement. However, the voltage remains very constant until the charge is about 70% gone, so it is very difficult to tell if the cell has 90% left of 40% left by voltage measurement.
In some systems a charge counter is used to measure the current draw from a cell to estimate the rremaining charge. That only works from a full charge and the charge counter has to be attached all the time to the battery.
In short I do not know of a device that can do the measurements you want easily.
The capacity is usually marked on the battery. To measure that you need an elaborate setup, as you have to fully chrage the battery and then discharge it with a fixed current while monitoring the output voltage.
Once you have the discharge curve (voltage versus mAh already drawn) then you can estimate the remaining charge by a simple voltage measurement. However, the voltage remains very constant until the charge is about 70% gone, so it is very difficult to tell if the cell has 90% left of 40% left by voltage measurement.
In some systems a charge counter is used to measure the current draw from a cell to estimate the rremaining charge. That only works from a full charge and the charge counter has to be attached all the time to the battery.
In short I do not know of a device that can do the measurements you want easily.
I use those simple square clamp on battery checker to see if the rechargeables still needs charging. But this method is mere an estimate by observation so not for accuracy.
My usage observation for few common brands, mAh independent (based on the batt checker I used but you need to determine the pattern). When the rechargeable battery is at full charge, the pointer will swing 80% to the right (unless it is normal 1.5V, meter will never be 100%). A used one will have the meter around 70% right but still safe to ok.
An indicator of centre or 60% means battery is unreliable for usage. However, to check a faulty self discharging battery will need 1-2 days depending on the severity. A good battery will stay 80% for 1 week but faulty one will drop to 70% after a day or two.
My usage observation for few common brands, mAh independent (based on the batt checker I used but you need to determine the pattern). When the rechargeable battery is at full charge, the pointer will swing 80% to the right (unless it is normal 1.5V, meter will never be 100%). A used one will have the meter around 70% right but still safe to ok.
An indicator of centre or 60% means battery is unreliable for usage. However, to check a faulty self discharging battery will need 1-2 days depending on the severity. A good battery will stay 80% for 1 week but faulty one will drop to 70% after a day or two.
Maha has a charger which comes close.
Once you run through an analysis/ break in mode, it shows you something called the "available capacity" if I remember right. Don't quote me on this, it's been a while since I did it last, check the manual (available online) if you are not sure.
http://www.mahaenergy.com/store/viewItem.asp?idProduct=423
Once you run through an analysis/ break in mode, it shows you something called the "available capacity" if I remember right. Don't quote me on this, it's been a while since I did it last, check the manual (available online) if you are not sure.
http://www.mahaenergy.com/store/viewItem.asp?idProduct=423
If you want to know the mAH left, you'd probably need a battery analyzer. These do not come cheap - frankly it would be more affordable to simply replace the whole bunch of batteries at one go, unless you have a need for an analyzer/charger.
Analyzers can recharge batteries, so typically what you'll do is that you start it in charge mode, top up the battery, then let it run its discharge test. It will put a load on the battery and run it down, while counting the mAH. Once the battery is discharged to its minimum safe level (overdischarging DOES damage them), the analyzer stops and reports the mAH it successfully discharged from the battery.
I have used the Maha C777Plus2 and the Hyperion EOS5i AC/DC and they do the job well, they are not cheap though. I bought them as a charger for the varied kinds of rechargeables I work with.
If you want to know the mAH left without discharging the battery, guesstimation is the best way to go unless your battery has the electronics to record how much has been drained from it. Much easier to just put it back on the charger and top it up full.
Analyzers can recharge batteries, so typically what you'll do is that you start it in charge mode, top up the battery, then let it run its discharge test. It will put a load on the battery and run it down, while counting the mAH. Once the battery is discharged to its minimum safe level (overdischarging DOES damage them), the analyzer stops and reports the mAH it successfully discharged from the battery.
I have used the Maha C777Plus2 and the Hyperion EOS5i AC/DC and they do the job well, they are not cheap though. I bought them as a charger for the varied kinds of rechargeables I work with.
If you want to know the mAH left without discharging the battery, guesstimation is the best way to go unless your battery has the electronics to record how much has been drained from it. Much easier to just put it back on the charger and top it up full.
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sloth, thanks for the quick reply. i read from the powerex website that the c777plus2 can analyze and charge any battery. may i know where can i get the battery holders for them? and how fast do they charge my AAs? i am also a hobbyist for other electronics stuff, so i might be considering in getting it to help me check the life of my batteries.
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