| Author |
 Topic  |
|
|
rfrazier
USA
44 Posts |
 Posted - 02/09/2020 : 18:59:19
|
Hi all,
Been enjoying my meter. Unfortunately, I've discovered a significant problem with the battery (dis)charging circuit.
To other users, monitor the meter frequently to determine if it's posting a low battery warning (if running on battery). If so, charge it or discontinue usage and shut it off. Over discharging a Li-Ion battery can create a fire hazard. You can check the battery voltage with the menu, battery function. The manual says it shouldn't be below 3.3V.
I have the EMF-390v2 Rev 3.01. Whenever I get a new device, I drain the battery down and recharge it 3 times to break the battery in. The manual for this meter says the device will stop working when the battery is below 3.3V. However, it does not. I've been running the device and the battery dropped to 2.98 V before I decided to look at it. It's not shutting down. I've now started charging it and it seems OK. Please check this, as draining a Li-Ion battery too low can be a fire hazard. Please add a battery safety management circuit to prevent this from happening. You should modify the firmware to discontinue functioning and turn off the backlight, or just turn off the meter, when the battery is too low. But it would be better to have the battery management circuit shut the unit down, which would work no matter what the firmware is doing. I suppose that an uncontrolled shutdown could corrupt data being stored but I don't know. At the moment, the unit complains about the battery, but does not shut down. You could execute a controlled shutdown with firmware but still have the battery circuit do the shutdown if the battery continues to drain.
Also, as soon as I plugged in the charging cable, the display for the RF explorer immediately became filled with erroneous signals. The meter shows a full screen (all black) of pulses continuously at an intensity of about .25-.3 mW/m^2. I have auto scaling on. This completely prevents the meter's ability to read small signals, and at my RF alarm limit of .01 mW/m^2, is giving continuous alarms. Apparently there is RF leaking into the sensor from the power supply.
Sorry to be the bearer of this news, but I thought y'all should know.
Please let me know if you have a fix.
Ron
|
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
|
| Reply #1
rfrazier
USA
44 Posts |
Posted - 02/10/2020 : 11:46:58
|
Important additional information. According to this:
h**ps://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages
These batteries come in a couple of voltage types.
3.6V nominal with 4.1V max voltage and
3.7V nominal with 4.2V max voltage
quote form this web page -->
Make sure when you're buying batteries and chargers to match them up! Overcharging a 3.6V battery by attaching it to a 4.2V battery charger can at the very least permanently damage your battery and at worst cause a fire!
Important Note! When charging batteries you must make sure that the charger voltage is less than or equal to the battery voltage. For the best battery performance/life you should have them matched. For example: 3.7/4.2V battery and 3.7/4.2V charger: OK - 3.7/4.2V battery and 3.6/4.1V charger: OK (but not ideal) - 3.6/4.1V battery and 3.6/4.1V charger: OK - 3.6/4.1V battery and 3.7/4.2V charger NOT OK!
<-- quote off
The battery in my particular EMF-390 is labeled as a 3.6V battery. So, if I understand this correctly, that particular battery should never be charged above 4.1V. HOWEVER, as I was charging it, and monitoring it, it got up to 4.14V before I disconnected it. This means the meter was probably overcharging this particular battery.
Although the sticker on your device says 3.6V/3.7V, you need to determine if your charging circuit can distinguish between a 3.6V battery and a 3.7V battery. Assuming this article is correct (and it probably is), if you cannot distinguish between a 3.6V and a 3.7V battery, you must assume it's a 3.6V battery and terminate the charge at 4.1V rather than 4.2V in order to prevent possible damage to the battery and fire risk.
Not trying to harass you guys, but this is important. Please check your battery management algorithm or system and make sure that it's terminating the charge, and discharge cycles properly. If the capability isn't there, please add it in and provide a fix to us. And, don't ask the user to flip a switch or set a menu option to the battery type. That will never work. In this case, just assume a 3.6V nominal / 4.1V maximum battery if you have to.
If you want to know what these batteries can do when you tick them off, search youtube for 18650 lithium battery fire, or more generically for lithium battery fire.
Sincerely,
Ron
|
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
 |
|
| Reply #2
EmfDev
2250 Posts |
Posted - 02/10/2020 : 12:28:04
|
| Hi rfrazier, thank you for pointing it out. The threshold for automatically turning off the device is 2.9V. We will change it to 3.1 or 3.2V. And yes the RF Browser sensitivity decreases when battery is low. We will include them in the next firmware update. |
|
|
| Reply #3
rfrazier
USA
44 Posts |
Posted - 02/10/2020 : 14:13:12
|
I'm not a battery engineer, but I have read a lot about the topic. But I do believe that the low limit change you mentioned is a good idea.
It's good to know that there is a low level cutoff built in.
But, that's not all I was concerned about. Please see my reply above about the unit overcharging 3.6V batteries. That's very important and needs to be checked as well.
I wasn't concerned about a reduction in RF sensitivity when the battery is low, although that's good to know. What I was concerned about is that, when the charging cable is plugged into my power supply, the RF explorer screen is swamped with RF interference. Please see my description in my original post.
If there's a mailing list I can get on for product updates, I'd like to do that.
Thanks.
Sincerely,
Ron
|
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
Edited by - rfrazier on 02/10/2020 14:16:49 |
|
|
| Reply #4
EmfDev
2250 Posts |
Posted - 02/10/2020 : 16:13:29
|
Hi Ron, we have check with the battery datasheet from the manufacturer and it does say the nominal voltage is 3.6V and the Charge Voltage Limit is 4.2V. The circuit also has a current threshold that stops charging the device when the current didn't pass the threshold.
The RF Browser can be noise from the charging circuit or USB. When the battery charge is low, there will be more current on the charging circuit. |
|
|
| Reply #5
rfrazier
USA
44 Posts |
Posted - 02/10/2020 : 16:47:23
|
I appreciate you checking on the battery, and that you are responsive on the forum.
Interesting that the battery has a combination of 3.6V nominal and 4.2V maximum. That's a bit unusual. I'm glad you have some good safety features in place.
However, since the battery is user replaceable, you might want to account for the fact that the user could put in a battery with a 4.1V maximum. So it still might be a good idea to cut off the charge at 4.1V. Just a thought.
Thanks.
Ron
|
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
|
|
| Reply #6
EmfDev
2250 Posts |
Posted - 02/10/2020 : 17:18:00
|
| Thank you for your concern and I will let our engineers know about this issue that users can replace the battery with a different maximum voltage limit. I will also ask if this is going to be an issue or if it has more safety features. |
|
|
| Reply #7
rfrazier
USA
44 Posts |
Posted - 02/19/2020 : 13:37:41
|
Hello,
I've discovered another issue with the charging port. It is apparently severely altering the EF readings. I have the unit sitting on a shelf about 2 feet away from me. It's in EMF graphs mode. The EF is ranging from 40-50 V/M. The USB cord is plugged into the meter, but not the computer. If I literally move the computer end of the USB cord 2" and plug it into the computer, the EF reading jumps to over 500, more than a factor of 10X. So it appears that the charging port is also changing the EF reading. Now, regardless of whether the original number is close to correct, I don't believe it should change by a factor of 10X when the charging cable is plugged in.
Ron
|
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
|
|
| Reply #8
EmfDev
2250 Posts |
Posted - 02/19/2020 : 15:51:22
|
| Hi Ron, I believe it is because your computer contains a lot of EF, that it is also being detected/transferred to the EMF unit. It is not properly grounded. |
|
|
| Reply #9
rfrazier
USA
44 Posts |
Posted - 02/19/2020 : 16:19:03
|
| Thanks. However, even if that's true, I'm not sure there should be lots of RF (see reply #3) or EF coming from the charging circuit and affecting the readings from the sensors. Ron. |
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
|
|
| Reply #10
EmfDev
2250 Posts |
Posted - 02/20/2020 : 10:13:17
|
| It can be just dirty electricity or can be because it is amplified by the USB power. |
|
|
| Reply #11
rfrazier
USA
44 Posts |
Posted - 02/20/2020 : 10:35:05
|
I understand what you're saying, in that there may be rubbish on the USB power cord, either from the computer or the power supply. And, I'm not trying to be divisive. But, I don't believe that rubbish should be entering the meter and affecting the readings. It's essentially impossible for me to take reliable RF and EF readings with the power cable plugged in.
Ron
|
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
Edited by - rfrazier on 02/20/2020 10:36:00 |
|
|
| Reply #12
EmfDev
2250 Posts |
Posted - 02/20/2020 : 10:41:44
|
| Have you tried to plug it in to another computer? |
|
|
| Reply #13
rfrazier
USA
44 Posts |
Posted - 02/20/2020 : 16:43:10
|
I get similar results whether plugged into the usb port on my power strip or my pc. I haven't tried another pc.
|
-----
Ron Frazier - In training with the Building Biology Institute (https://buildingbiologyinstitute.org/) to become an independent Electromagnetic Radiation Specialist (EMRS). We measure, document, analyze, and recommend mitigations for harmful EMF exposures.
All my statements are mine alone though.
|
|
|
| Reply #14
EmfDev
2250 Posts |
Posted - 02/21/2020 : 09:43:00
|
| The EF going up is normal but the RF getting a lot of noise is a little weird. |
|
|
| |
Topic |
|
GQ EMF-390v2 significant problem with charging ckt
