RE: Battery Charger
- Thread starter Horus
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Well, there is no way you can actually measure the remaining charge in a battery.
What you can measure is the voltage. For regargeable batterries, the voltage stays pretty constant (1.2V per cell) until the charge is almost depleted, then the voltage sort of plunges.
So measuring the voltage is not a very accurate way of determining how much more energy is left in the battery. You can probably only tell roughly if a battery is freshly charge (higher than 1.2V), in mid life (roughly 1.2V), or just about to run out of juice (lower than 1.2V).
If the voltage measurement is very accurate (better than 1%) the battery can probably be profiled and a more accurate accessment is then possible.
- Roy
What you can measure is the voltage. For regargeable batterries, the voltage stays pretty constant (1.2V per cell) until the charge is almost depleted, then the voltage sort of plunges.
So measuring the voltage is not a very accurate way of determining how much more energy is left in the battery. You can probably only tell roughly if a battery is freshly charge (higher than 1.2V), in mid life (roughly 1.2V), or just about to run out of juice (lower than 1.2V).
If the voltage measurement is very accurate (better than 1%) the battery can probably be profiled and a more accurate accessment is then possible.
- Roy
The Maha MH-C777PLUSII Universal Battery Charger & Analyzer gives a LCD readout of the battery current voltage level as well as its charge capacity in mAh. It's the best battery analyzer available. It's retailing for US$90 in the states and I am selling it for S$169.95 in Singapore.
Maha official product website:
http://www.mahaenergy.com/products/prosumer/mhc777plus.htm
Maha official product website:
http://www.mahaenergy.com/products/prosumer/mhc777plus.htm
Then again, measuring pure voltage without a load gives false readings. An alkaline cell can give you a 1.5V reading under almost no load (since the voltmeter has such a high impedance), but the voltage can drop rapidly with a load applied.
Some of those battery testers out there actually put a load on the battery, then measure the voltage across the load.
Regards
CK
Charge is actually the amount of current flowing over a period of time. The MH-C777PLUSII Universal Battery Charger and Analyzer uses a microprocessor to measure the current coming out from a battery over a certain time period and calculate/display the charge capacity of the battery accordingly.
The amount of charge put in or taken out of a battery can be measured, by accurately monitoring the charging and dischargin current at sufficient sampling rate, but given any battery of unknown amount of charge left, there is no way of telling how much charge is left in it except by measuring the voltage and make an estimate.
The MAHA charger can measure the CAPACITY of a battery by measuring the voltage versus charge current with very high accuracy but it cannot tell how much charge is left in a battery - this is my understanding of the charger as well as the thread originator's question.
- Roy
As charge = current x time, the MAHA charge doesn't "meaure the (charge) capacity of a battery by measuring the voltage". Your first statement
would be a more correct description of how the MAHA charger works.
Hence it is POSSIBLE to tell how much charge is left in a battery on the MAHA charger, by running the battery through a discharge cycle and measure the amount of charge taken out of a battery. However the results cannot be obtained instantaneously but only after the battery is discharged.
would be a more correct description of how the MAHA charger works.
Hence it is POSSIBLE to tell how much charge is left in a battery on the MAHA charger, by running the battery through a discharge cycle and measure the amount of charge taken out of a battery. However the results cannot be obtained instantaneously but only after the battery is discharged.
The voltages for rechargeables actually ranges from 1.4+V when freshly charged to 1.1-1.2V when discharged. I used the voltage (measured using a multimeter) as an indication of remaining charge left and it worked well so far. Experience is from the >30 NiMH and 5-6 brands of batteries used over the years.
The Charger has to monitor both the voltage and current to determine as accurately as possible the point which the battery is considered fullt charged. Measuring current alone is not sufficient. Yes, charge = current X time, but how much time? The time value has to be determined by the voltage variations across the battery.
I took it as the originator is more intested in a way to know the remaining charge in a battery without having to deplete it. My take was that he is interested in a way to tell the remainiding charge in a battery so that he can estimate how much longer or how many more shots he can use the battery for.
So the MAHA charger does not do that - telling how much charge is left in a battery without depleting it in the first place.
I agree the Maha charger can tell the capacity of a battery by monitoring how mch charge is used to charge it until full, and can tell the remainiding charge by depleting it and measuring the amount of chartge that was taken out during the process.
I don't think we have a different technical understanding of chargers, but we need to clarify the origianl question first. If we both agree on the originator's true question, I am sure we will both agree on whether the Maha charger can do the job for him or not without the need for any debate.
- Roy
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