The component in the battery pack is a THERMISTOR - the sensor that you plugged in to your multimeter (DMM) is a THERMOCOUPLE. The two are completely different: a thermistor changes its resistance with temperature whereas a thermocouple generates a (very small) temperature-dependent voltage. The thermistor in the battery pack does not generate any voltage - its change in resistance is sensed elsewhere in the system, either within the battery or within the charger (depending upon the design). When you set your DMM to measure a resistance, it puts a small voltage across the probes in order to make that measurement. When you try to measure the resistance of a thermocouple, the voltage generated by the thermocouple will interfere with the voltage from the DMM and cause it to give a reading which is, in part, dependent upon the thermocouple's temperature. That's why the reading changes when you hold the thermocouple - you are NOT measuring its resistance.
Hi all. The sensor is NTC 5K means its resistanse at 25C is 5Kohms. Quick test can be done on battery by measuring pin resistanse as 20~22Kohm for 14.4V batteries, 6~8Kohm for 18V batteries. Good luck.
For Quick test the resistanse reading higher than 5Kohms since as can seen on video that there is resistanse on pcb board line of NTC. Thats why the readings are different.
Nice video, just a bit of advice from me: learn the difference between thermistor and thermocouple. Thermistor does not generate any voltage, thermocouple does. Have fun ✌️
Yep. The thing with the yellow plug that he plugs into the meter is a thermocouple. As soon as i saw that, I came here and looked for a comment :) However, good advice apart from that, I have a bad battery and will be breaking it apart to see if it's the same problem.
Hello Do you have a part number for the replacement thermister either from Mouser or Digi-key or any other supplier, there are so many out there with multiple vairiations. thanks in advance
Thanks for your video, btw, Would you know the use or purpose of the last one among three cables connected with LED indicator, i.e., it's attached with (+) & (-) cables seen in the playing time of 05:40. * Thank you for this reading in advance.
Thanks for that. The good news is, looks like this is precisely what's wrong with my battery here. The bad news is, mine is a "home and garden" battery from a hedge trimmer, which appears to be the exact same pack inside, but the casing is different (can't fit the same charger) and, though four screws gets me in to the outer case, then I find the controller is soldered to the top of the pack, so next to impossible to get the thermistor out or replace it without de-soldering the board, altogether a more fiddly fix. Which I won't attempt until Bosch have a chance to do the right thing and replace my just-over-a-year-old unit.
I take it back - I found out something important about the CHARGER. Basically, it will not start to charge the pack unless it sees at least a minimum voltage. I took a 12v bench supply attached across the entire battery pack - but inside the control circuits - and fed it *brief* pulses (no more than ten seconds at a time, with a few seconds pause in between) of 12v, for a couple of minutes. This put a small charge in the cells. I showed a voltage across the pack now. It was going down fast as it was a very small charge BUT on attaching the pack back to the charger, the charger decided it liked it and started to charge normally! Once full, I ran the trimmer for about five minutes, then left the pack overnight and it was still good the following day. So I don't know why it fully discharged, but now I know how to get it charging again. Of course, fully discharging the pack is not good for it. Now I'm storing the battery NOT on the trimmer, and will check it again in a couple of weeks.
@HYDRARAPTOR Gaming I've not analysed a "good" battery in either full state or when the trimmer reports it too low to run, so, I don't know what the expected voltages are for either end of "normal" operations, I'm afraid. 3v is the lowest voltage recommended for these cells however, so I assume if it's only 3v per cell, the trimmer *should* refuse to run, but the charger should be happy to charge.
You are conflating an thermistor with a thermocouple, the one on your meter is a thermocouple ie it generates a small voltage, the one in the battery is probably a thermistor, its resistance changes with temperature. But thanks for the video.
Where can i buy this thermistor as it looks like same issue on my battery. It is a Bosch 36v 4a for lawnmower. Very interesting guide well done. Any info please, it is worth a try before i bin it.
For everyone, a thermistor comes in two types. The negative temperature coefficient can be negative or positive. If warming the thermistor, them resistance goes up, this is a "Positive Temperature Coefficient" type or PTC. The "NTC" type goes down as it gets hotter. I choose to remember this by using a phrase " The hotter you girl gets, the lower her resistance gets". They have limits at temperature and the most popular are 10k. Like all resistors they have an accuracy of +/- value. A GM transmission temp sensor is a NTC with 90,636 ohms at -40 degrees F, while at 72 degrees F, is 25 degrees C. The last is 42.5 ohms at 302 degrees F / 150 degrees C. This info is posted on GM's diagnostics service info but true as there is max of 110.778 F and 51.9 F on the low end. Lithium Ion batteries are charged between 20% die-charged to 80% fully charged. Techs, construction workers and the general user never where told this is why they quit without warning. If amps are flying, they get hot. This is where the thermistor shuts off the circuit and the tools die. Many good videos show how to test components in an electronic circuit can be tested with a good digital multimeter or called DMM. Best of luck to everyone, stay safe during this "WU-FLU" era. Unfortunately as hospitals open in NE, I will have my 4th Lumbar fusion...Yeh! Can you say L3-L2 disc & spinal stenosis? All from my 1987 stupid boss; argument and using me instead of hourly employees instead of a seasoned ASE Master. Do I sound bitter? Dam straight, I will place hose nose where it needs to go. Nice video buddy!
I am unable to tell you as each company builds the battery management control board differently. If you have a two wire device that sits near the batteries then take photos for future reference. Look for any marking like #'s and letters, use these to search for data sheet. If no marking or not readable, de-solder it and measure with digital multi meter. Just the heat of a hand or hair dyer to make it change. If resistance goes down or up, it is probably set to voltage comparator the stops charging or disconnect from the tool if driving large screw, fast drain, then heats up and a MOSFET opens, no tool voltage. I wish i could help you more but i have trays of Motorola chips no longer published in data sheet. You don't even need an expensive digital multi meter. 80% full to 20% of empty or too hot, the lithium ion battery has to be protected. That all. Hope this helps.
Based on the look of the battery (sticker design and 3-bar status LED) it's the old 18650 design. The ProCore 21700-based batteries have a different design and a 5-bar status LED.
"So there is no resistance whatsoever, it is just an open circuit"... :-) Anyway, good video but would be even more useful if you could let us know the type of the thermistor used, the battery type etc.
Hi, great vid! I lost the charger but have a 4 pin alko (+, Bs,Tv , -) output 10.8 - 20V. Can I pin up the batt to this to charge bosch gba 18v 6ah batt? Yes... batt has 5 conn and charger only 4... dont want to break battery ;-) possible? Thx Lis
Hey can we do this with the new Bosch profactor battery? I have the 8ah. All I'm getting is a temperature reading in the charger. I took apart the battery but it has a completely different board. Any idea where the thermistor is in the new batteries?
hi, i'm not sure if my power drill has the same problem. when i turn it on, the drill spins slowly in a few seconds then stops spinning, then the led will also die a few seconds after that. (sorry for my bad english 😁)
Debes medir el voltaje del pack y de forma individual cada baterías por si surge diferencias. Estaría bueno tener un cargador inteligente para obtener datos de la resistencia interna, quizás ya cumplió sus ciclos o simplemente falló 🤔
Thank you so much. This is my exact problem with 2 of my Bosch 18v 2Ah. Fully charged but no power to drill. Where do I buy these thermisters and what is the power of these ? I had to buy new ones but the others are only 15 months old and in great shape. I assume they got overheated in the car as they worked before the job and not after. Thanks again, where do I buy these. very grateful.
The device you used on your multi-meter to measure temperature is a thermocouple, not a thermistor. They are not the same, they work differently. This does not really change how you fixed the battery. They just can't be used interchangeably.
Yup, thermocouples generate a small voltage, thermistors vary their resistance - in this video the two functions were confused. The would have actually been a whole lot more useful if the replacement thermistor type had been identified.
Hey, got an idea where i can buy a few for a good price? Got 2 18v Bosch old type and 2 Bosch 18v procore that i need to change the thermistor on .. Google makes me dizzy …
Might just need new cells. Problem is with new cells you'll need a spot welder to weld the strips back on. If you have that ability, rip the case apart and see what size the cells are and order new ones. Otherwise you can try to rebalance the cells that are in it.
Drill into the seal very gently with a 6mm drill until you touch the head of the screw underneath. It should now be possible to remove it with the t10 screwdriver
I have 5 pieces of Bosch PeoCORE18V 4.0 Ah, all the cells are correct, the machines work but they won't charge? The charger has been tested and works properly.
Very good. do you know how to get rid of that thermoster (i know it is not safe)? putting that conector to ground? Do you have the schema of that simple board? Thank you
@@Electronicle Thank you. Can i reformulate the question and put it in a safer way? I have a bosch tool that operates at 18v. With lithium. On the other hand i have a perfertly safe lithium pack with its board bms and a thermistor inside. The problem is that if y connect the positive and negative a get the light up but does not work. Should i put one of the connector of the thermidtor to the pin in the tool? Just to clarify the battery is a 3s4p lithium from a third party provider. Any help would be very apreciated Thank you. In the case of this third party battery the thermistor is connected in serie from the negative. I understand if the temperature goes up then it makes an open circuit until it goes down.
Why is my battery charging up but draining over a couple of days I noticed the power indicator light was not working correctly and was coming on on its own is it just a bad indicator and am I'm OK just to delete it ?
If it's draining when you aren't using it then one or more of the cells in the battery are bad and internally shorted. Nothing you can do other than replace the cells or the entire battery
If the indicator comes on on it's own... that is bad too. You can most likely just disconnect it without any issue. If it still drains, cell(s) might be bad.
Hi, Thx for the video! It is quite rare to get infos how the bosch battery is built. For me, replacing the thermistor by a 6.8k resitor worked (just connected to middle pin and minus). of course, this is not replacing a thermistor, but may help. use at own risk!
Entonces podría usar una fuente externa para alimentar amoladora...🤔 Pensaba en energizar con fuente de laboratorio y conectar NTC mediante resistencia de 6,7K = 20°C pero me gustaría confirmar si el terminal Código 1 (R1) = 7,6 K Ohm 1% ? Código 2 (R2) = 51,3 K Ohm 25% para simular Batería Bosch 18v 4 Amperes ?
Very informative video. I have a 6ah bosch 18v battery and when it is charging it stops changing before its fully charged, only goes up to 2 lights on the battery monitor then the charger cuts off, its not the charger as it charges my other batteries fine.
the internal cells may have become unbalanced, or they are just shot. Check out this video, might help: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-SfwEKrBVd8s.html
No the trick is to warn others about shorting the battery and then wrecklessly wave a conductive screwdriver tip around, hitting it off live circuit boards. That's how it's done xD
