XML - Low voltage warning with full battery: FastTech Forums

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#1 (permalink) 5/11/2013 3:23:10 PM US Central quote/reply + tips
Ombudsmann Member JoinedFeb 2013 Posts 9 Reviews 1 Kudos0	XML - Low voltage warning with full battery Hi I'm getting the low input voltage blinking on a full battery. Tested it with two of the drivers and U3 and T6 LEDs. I found out that it only works if I use a looong (50cm+) ground/minus cable between the led and the driver board, instead of the original short one. I don't get that issue with "smaller" LEDs like the XR-E. Anyone an idea how to fix it? I would be very grateful. The long ground cable doesn't fit fine inside the flashlight ;) Working...
#2 (permalink) 5/24/2013 3:07:11 AM US Central quote/reply + tips
geek Tech Staff JoinedJun 2012 Posts 3102 Reviews 19 Kudos4039	Sorry for taking so long to reply. This is caused by your batteries. When certain batteries are under heavy stress (high current drain), their output voltage drops due to internal impedance. This causes the driver to think you're out of juice. However, when you have a long wire going out, the effective drain is lowered because the wire limits the current going through the LED. Thus your batteries are not so stressed and puts out a higher voltage. This is why you don't get that warning with a long wire. Try using some IMR high current batteries, and you'll see the problem go away. Edited on 5/26/2013 at 11:22 PM. Reason: I'm not a CS staff but I help answering questions here. If I missed your questions, I apologize and you are not being ignored :). Working...
#3 (permalink) 5/24/2013 6:23:09 AM US Central quote/reply + tips
Ombudsmann Member JoinedFeb 2013 Posts 9 Reviews 1 Kudos0	I tested it with SKU 1050702, 1053200, 1084200, 3 x 1140601 and 3 x black Eneloop. All the batteries are working fine (under the same <3.9V condition) with Nanjg 3A drivers with 750mA, Nanjg 1.4A, Nanjg 2.1A, Nanjg 2.8A, and also with an other 1A driver. But not with these two... Working...
#4 (permalink) 5/26/2013 11:25:08 PM US Central quote/reply + tips
geek Tech Staff JoinedJun 2012 Posts 3102 Reviews 19 Kudos4039	The drivers may have different voltage limits. Have you measured the output voltage at battery terminals when the LED is on? I suspect that voltage has dropped under 3.3V causing the driver's low voltage blinks. I'm not a CS staff but I help answering questions here. If I missed your questions, I apologize and you are not being ignored :). Working...
#5 (permalink) 5/27/2013 5:26:06 PM US Central quote/reply + tips
Ombudsmann Member JoinedFeb 2013 Posts 9 Reviews 1 Kudos0	Thanks for your replies geek. I measured the voltage, it drops from 3.92V to 3.5V. Surely it is lower than 3.5V for a very short moment and my meter doesn't capture this. But why is the voltage drop so high? It is even higher as with the 3A Nanjg driver. It makes the driver almost useless. "Perfect for use with 1 lithium battery or 3 AA/AAA batteries" With 3xAAA it is useless. And "Perfect" should be replaced with "Horrible" ^^ Do you maybe know a simple workaround for the issue, maybe a small capacitor? Or can the component for the voltage check be soldered-out/shorted-out/bypassed? Or can I take an other Nanjg driver, solder some AMC7135 out, and make a 1A driver out of it? //Edit I did a little research. It seems that the low quality diode for the reverse polarity protection causes the excessive voltage drop. Without the diode, and of course without the protection, no blinking appears at 3,9V. With the diode the voltage drops on switching from 3.92V to 3.5V and during operation it goes up again to ~3.8V. Without the diode the voltage drops on switching from 3.92V to 3.90V and stays at the same. Edited on 5/31/2013 at 9:22 PM. Reason: Working...
#6 (permalink) 6/21/2013 12:49:55 AM US Central quote/reply + tips
EVGENIY12 Member JoinedApr 2013 Posts 3 Reviews 0 Kudos0	Thanks Ombudsmann. Had the same problem. I shorted diode. The driver began to work normally. Only now there is no Reverse Polarity Protection. Working...
#7 (permalink) 6/21/2013 9:54:45 AM US Central quote/reply + tips
Ombudsmann Member JoinedFeb 2013 Posts 9 Reviews 1 Kudos0	привет EVGENIY12, the diode doesn't need to be shorted. It is enough to solder the positive led lead to the other end of the diode. I have replaced the diode by a (way too big) 3A Schottky diode, with which the driver has worked great. Now I'm waiting to get smaller Schottky diodes. Working...
#8 (permalink) 6/21/2013 12:09:48 PM US Central quote/reply + tips
EVGENIY12 Member JoinedApr 2013 Posts 3 Reviews 0 Kudos0	RUS: Привет Ombudsmann. Тоже в начале хотел поменять диод, но по причине его отсутствия просто закоротил. Фонарем пользуюсь только я, так что неправильная установка аккумулятора практически исключена. Интересны последствия неправильной установки 18650. Драйвер или диод могут выйти из строя? ENG: Hi Ombudsmann. Also in the beginning wanted to change the diode, but because of its lack of it just shorted. Only I use a flashlight so that incorrect installation of the battery is practically impossible. Interesting effects of improper installation 18650. The driver or the diode may be damaged? Working...
#9 (permalink) 6/21/2013 2:15:55 PM US Central quote/reply + tips
Ombudsmann Member JoinedFeb 2013 Posts 9 Reviews 1 Kudos0	Interesting effects of improper installation 18650. The driver or the diode may be damaged? Я напишу на английском: I'm no expert. I think you can break the IC. I wanted to try it once or twice :) But the flashlights belong to children, and they certainly would not like it if I make their toys broken. Edited on 6/21/2013 at 2:17 PM. Reason: Working...
#10 (permalink) 1/29/2014 12:45:22 PM US Central quote/reply + tips
Jerommel Member JoinedJan 2014 Posts 132 Reviews 3 Kudos27	So, the "polarity protection" is just a diode? That eats away about 0.6 Volts.. What a waste.. :( Makes it useless for a single LiPo (like 18650) So it's best to bypass it. Schottky's are still at least 0.4 Volts drop (waste).. Anyway, is it possible to add more 7135's to this driver? Working...
#11 (permalink) 3/2/2014 1:36:40 AM US Central quote/reply + tips
Ghost.of.Fast.Tech Member JoinedDec 2012 Posts 158 Reviews 1 Kudos104	+1 details Jerommel, the diode does not waste power in this setup. Power for the amc7135s (and your led) does not go through the diode. I am Not a FastTech staff member. Working...