DISCLAIMER. THIS IS A REVIEW OF A PRODUCT I BOUGHT. I DO NOT HAVE ANY FINANCIAL ETC. INTEREST IN RECOMMENDING THIS.After years struggling to find an easy way to measure battery capacity I think I have the answer. Previous attempts by say discharging into a car headlamp bulb gives an answer but only approximately and it’s easy to come back after setting up hours of discharge to find the bulb barely glowing, which means you have little idea when it reached the 10-11V usual end point for a car battery. Over discharge damages the battery.
The Atorch DL24 tester is here https://www.aliexpress.com/item/4000925725225...2010612.8148356.13.b0426f31FADmei
Good points of product.
• This unit is an electronically variable <=150 watt resistor. You set a resistance value to connect across the battery (better substitute for the lamp bulb above) and it then measures the discharge curve. The resistor dumps its heat into a large heatsink, which the fan cools. (For the techies amongst you the resistor is actually a transistor under the heatsink.)
• It can measure batteries from 2V to 200V and up to 20 amps. But it is limited to 150W so at 12V that is 12.5A. There is a more expensive 180W DLP model but can’t see the point for any normal car battery unless you are a garage wanting to test lots in a hurry or have huge UPS or solar batteries. Capacities displayed vary from 1mAh to 99.999Ah so it covers a huge range of battery sizes.
• To use it take just a few secs to clear the non-volatile saved results from the last battery tested, set the discharge current, e.g. 10-20% of the rated Ah to give a 5-10 hour discharge time. Set an end voltage limit like 11V, when the unit stops the discharge and a max time (these will all be saved from last time so no need to change if you are testing several similar batteries). Press start and walk away. Come back hours later and the screen tells you how many Ah it measured. Simples! It even will cope with power cuts as can just restart the discharge. Or can run it with a high current for the first part to speed the test and cut to a lower current later. On old batteries with their higher internal resistance using too high a current to the end will trip the end point voltage early due to the voltage drop in the internal resistance.
• The unit is confusingly marketed as a USB tester, which nearly stopped me buying it as I thought it did not do ordinary battery testing as well. But what it means is that it has a row of small USB sockets in parallel with the battery leads, which can be used to test the capacity of USB power banks. Also can test mobile phone etc. chargers by setting their rated current and seeing if it actually can deliver it without getting hot or dropping its voltage. There is a temperature sensor you can tape to the battery/charger to check it but don’t think you can set a cut off temperature limit.
• There are 4 modes: 1. Constant current operation. 2. Constant resistance operation. 3. Constant power operation. 4. Constant voltage operation.
Not sure any other than CC are particularly useful. CP will speed discharge a little if doing large batteries at the max power.
• Well-made and robust so should be reliable, albeit without a case.
• It comes with a 12V mains adopter with USA plug. One could make up a DC lead to power it off the car battery instead, but be careful you don’t use other than 12V on this.
• A website provides files for Apps, instructions, etc. But hard to know what all the files are for.
• Possibly one could use it “in reverse” to record the charging Ah into a battery. There are other similar products that will be better at this. Search for coulombmeter.
Problems with product
.
They are few and not serious but:
• As a bare PCB you have to be a little careful, like keeping metal away from it to prevent shorts and, if testing batteries >35V, there is a shock risk. But it’s by no means a geek only device, which many non-cased electronic items are. Don’t need to solder anything. Has good plastic feet to keep the bare connections off the table. Hard to put a case around it without severely restricting the cooling air and visibility of the screen.
• Don’t know how accurate it’s readings are. The spec makes no claims. There are lots of decimal points on the displays but that does not necessarily translate into accurate measurements, e.g. if the shunt resistor used for measurement is inaccurate. Manual and screen talks of calibration settings but don’t know how to set them. May be from the Windows App.
• The supplied battery crocodile clip leads are short, thin and with small clips. So for car batteries make your own ones with large clips and thicker wire or can clip to larger clips but risks more voltage drop. Mine has black clips for both +ve and -ve, which is probably just a packing mistake as the website shows red and black. I don't know if it is protected against reverse polarity connection. The normal trick of inserting a protection diode in one battery lead does not work on such meters, as it completely distorts the answers, due to the diode’s voltage drop. But maybe there is one downstream of the voltage and current sensing points, as under the heatsink there is a large diode.
• Instruction sheet is fairly brief and in Chinese and poor English.
• There is a crude Android App to display the progress and instantaneous current, voltage, capacity, etc reading . The graph could be useful but it is scaled to 60A, 300V and 1 minute so on a typical car battery test all you get are lines across the bottom of the graph for the last 1 minute of data. Can’t change the scaling. It is Bluetooth connected so, like a covid contact tracing App, has limited range. You might as well walk to the tester and read its excellently clear and data rich colour screen. Maybe the PC App using a USB cable is more useful. Not tried it or the Apple App.
There might now be an App update that can rescale the graphs.
• Does not do 1.2V or 2V single cells, like the many AA rechargeables I have, as the minimum cut off voltage is 2V. You could do them in sets of 2-4 to bring the voltage up to more than 2V and, if the overall capacity is poor, discard the one that measures the lowest loaded voltage at the end of the test. But then have to retest the better one(s) by replacing the discarded one.
I see there is talk on the Aliexpress link above of modifying the cut off voltage so can then probably do 1.2V cells.
The instructions are only in Chinese through. Anyone able to help translate these? Appears you load new firmware through a USB memory stick. See https://www.mediafire.com/folder/m09i9bjv8703d/DL24-DL24P
• Does not do Cold Crank Amp (CCA) testing as with the testers garages use, e.g. https://www.sealey.co.uk/product/5637185942/digital-battery-alternator-tester-12v. These I think, like a starter motor, extract huge current from the battery, but in very short pulses, measuring the dip in battery voltage during the pulse; takes just seconds to work out its internal resistance. On Hybrids and EVs CCA is rather irrelevant as their batteries don’t ever deliver heavy discharges such as cranking an engine. I think one could do a pseudo CCA measure with the reviewed tester by say briefly measuring battery voltage at 1 and 12 amps; then internal resistance = (voltage 1 – voltage 2)/(12-1). There must be crude relationship between that and CCA. (There is no easy relationship between CCA and Ah so can’t accurately use such garage testers to check capacity of say solar or leisure batteries, although I have been doing this in my charity work on African solar PV. I could now use the reviewed tester but it would take a long time to discharge the typical >200Ah solar battery.)
• By doing one complete battery discharge you are using up of one of its rated life cycles. New batteries typically can do only 200-1000 full cycles depending on the technology and quality (maybe 500-1000 for a car's 12V battery) so one less cycle is significant. Whereas the CCA testers hardly discharge them.
I do have a similar cheaper unit but it is much more limited in capability and you have to supply a fixed resistor and heatsink or a light bulb and a relay to cut off the battery when the set voltage limit is reached. Also have to be there to record the discharge time when it clicks off.
I wrote this for another website and thought it was would be of interest to you too.
The Atorch DL24 tester is here https://www.aliexpress.com/item/4000925725225...2010612.8148356.13.b0426f31FADmei
Good points of product.
• This unit is an electronically variable <=150 watt resistor. You set a resistance value to connect across the battery (better substitute for the lamp bulb above) and it then measures the discharge curve. The resistor dumps its heat into a large heatsink, which the fan cools. (For the techies amongst you the resistor is actually a transistor under the heatsink.)
• It can measure batteries from 2V to 200V and up to 20 amps. But it is limited to 150W so at 12V that is 12.5A. There is a more expensive 180W DLP model but can’t see the point for any normal car battery unless you are a garage wanting to test lots in a hurry or have huge UPS or solar batteries. Capacities displayed vary from 1mAh to 99.999Ah so it covers a huge range of battery sizes.
• To use it take just a few secs to clear the non-volatile saved results from the last battery tested, set the discharge current, e.g. 10-20% of the rated Ah to give a 5-10 hour discharge time. Set an end voltage limit like 11V, when the unit stops the discharge and a max time (these will all be saved from last time so no need to change if you are testing several similar batteries). Press start and walk away. Come back hours later and the screen tells you how many Ah it measured. Simples! It even will cope with power cuts as can just restart the discharge. Or can run it with a high current for the first part to speed the test and cut to a lower current later. On old batteries with their higher internal resistance using too high a current to the end will trip the end point voltage early due to the voltage drop in the internal resistance.
• The unit is confusingly marketed as a USB tester, which nearly stopped me buying it as I thought it did not do ordinary battery testing as well. But what it means is that it has a row of small USB sockets in parallel with the battery leads, which can be used to test the capacity of USB power banks. Also can test mobile phone etc. chargers by setting their rated current and seeing if it actually can deliver it without getting hot or dropping its voltage. There is a temperature sensor you can tape to the battery/charger to check it but don’t think you can set a cut off temperature limit.
• There are 4 modes: 1. Constant current operation. 2. Constant resistance operation. 3. Constant power operation. 4. Constant voltage operation.
Not sure any other than CC are particularly useful. CP will speed discharge a little if doing large batteries at the max power.
• Well-made and robust so should be reliable, albeit without a case.
• It comes with a 12V mains adopter with USA plug. One could make up a DC lead to power it off the car battery instead, but be careful you don’t use other than 12V on this.
• A website provides files for Apps, instructions, etc. But hard to know what all the files are for.
• Possibly one could use it “in reverse” to record the charging Ah into a battery. There are other similar products that will be better at this. Search for coulombmeter.
Problems with product
.
They are few and not serious but:
• As a bare PCB you have to be a little careful, like keeping metal away from it to prevent shorts and, if testing batteries >35V, there is a shock risk. But it’s by no means a geek only device, which many non-cased electronic items are. Don’t need to solder anything. Has good plastic feet to keep the bare connections off the table. Hard to put a case around it without severely restricting the cooling air and visibility of the screen.
• Don’t know how accurate it’s readings are. The spec makes no claims. There are lots of decimal points on the displays but that does not necessarily translate into accurate measurements, e.g. if the shunt resistor used for measurement is inaccurate. Manual and screen talks of calibration settings but don’t know how to set them. May be from the Windows App.
• The supplied battery crocodile clip leads are short, thin and with small clips. So for car batteries make your own ones with large clips and thicker wire or can clip to larger clips but risks more voltage drop. Mine has black clips for both +ve and -ve, which is probably just a packing mistake as the website shows red and black. I don't know if it is protected against reverse polarity connection. The normal trick of inserting a protection diode in one battery lead does not work on such meters, as it completely distorts the answers, due to the diode’s voltage drop. But maybe there is one downstream of the voltage and current sensing points, as under the heatsink there is a large diode.
• Instruction sheet is fairly brief and in Chinese and poor English.
• There is a crude Android App to display the progress and instantaneous current, voltage, capacity, etc reading . The graph could be useful but it is scaled to 60A, 300V and 1 minute so on a typical car battery test all you get are lines across the bottom of the graph for the last 1 minute of data. Can’t change the scaling. It is Bluetooth connected so, like a covid contact tracing App, has limited range. You might as well walk to the tester and read its excellently clear and data rich colour screen. Maybe the PC App using a USB cable is more useful. Not tried it or the Apple App.
There might now be an App update that can rescale the graphs.
• Does not do 1.2V or 2V single cells, like the many AA rechargeables I have, as the minimum cut off voltage is 2V. You could do them in sets of 2-4 to bring the voltage up to more than 2V and, if the overall capacity is poor, discard the one that measures the lowest loaded voltage at the end of the test. But then have to retest the better one(s) by replacing the discarded one.
I see there is talk on the Aliexpress link above of modifying the cut off voltage so can then probably do 1.2V cells.
The instructions are only in Chinese through. Anyone able to help translate these? Appears you load new firmware through a USB memory stick. See https://www.mediafire.com/folder/m09i9bjv8703d/DL24-DL24P
• Does not do Cold Crank Amp (CCA) testing as with the testers garages use, e.g. https://www.sealey.co.uk/product/5637185942/digital-battery-alternator-tester-12v. These I think, like a starter motor, extract huge current from the battery, but in very short pulses, measuring the dip in battery voltage during the pulse; takes just seconds to work out its internal resistance. On Hybrids and EVs CCA is rather irrelevant as their batteries don’t ever deliver heavy discharges such as cranking an engine. I think one could do a pseudo CCA measure with the reviewed tester by say briefly measuring battery voltage at 1 and 12 amps; then internal resistance = (voltage 1 – voltage 2)/(12-1). There must be crude relationship between that and CCA. (There is no easy relationship between CCA and Ah so can’t accurately use such garage testers to check capacity of say solar or leisure batteries, although I have been doing this in my charity work on African solar PV. I could now use the reviewed tester but it would take a long time to discharge the typical >200Ah solar battery.)
• By doing one complete battery discharge you are using up of one of its rated life cycles. New batteries typically can do only 200-1000 full cycles depending on the technology and quality (maybe 500-1000 for a car's 12V battery) so one less cycle is significant. Whereas the CCA testers hardly discharge them.
I do have a similar cheaper unit but it is much more limited in capability and you have to supply a fixed resistor and heatsink or a light bulb and a relay to cut off the battery when the set voltage limit is reached. Also have to be there to record the discharge time when it clicks off.
I wrote this for another website and thought it was would be of interest to you too.
