Oscilloscope battery swap

Thread Starter

liteace

Joined Mar 7, 2012
135
Hi ALL, need help, I have here a portable oscilloscope, its new old stock. it works a treat but the batteries are not to good as they're passed their sell by date. What I would like to do is add 18650's and a charging /bms board, Im not to worried about removing the old batteries or using the units charging / bms, if I can it'll be a major bonus but there is room for extra charging / bms and socket. what I really need is that it charges from a 12 volt supply.
here's is what is what is already fitted, whats the best way to to got about this

Thanks

scope_bat_1.PNGscope_bat_2.PNGscope_bat_3.PNG
 

twohats

Joined Oct 28, 2015
97
Just a thought, you mentioned a12v charger. You could fit a 12 volt battery (Cells to suit), then regulate it down to suit the 'scope. Good luck...
 

Thread Starter

liteace

Joined Mar 7, 2012
135
I had another look today, theres not as mush space in there as I though so adding the 18650's could be a problem + the original batteries are 6100mah thats way more than any 18650 is it not
 

Audioguru again

Joined Oct 21, 2019
940
The original battery is Lithium-Polymer (Li-PO) that is flat and has a thin polymer case instead or the round metal cylinder of an 18650. Its average voltage is 7.4V which is two lithium cells.
I have never seen single flat Li-PO cells larger than only 500mAh.
 

Thread Starter

liteace

Joined Mar 7, 2012
135
So they are then 6100 mAh, adding a 3+3 pack of 18650 im not going to get anywhere near that am I ?

Thanks
 

digley

Joined Mar 15, 2016
1
Hi ALL, need help, I have here a portable oscilloscope, its new old stock. it works a treat but the batteries are not to good as they're passed their sell by date. What I would like to do is add 18650's and a charging /bms board, Im not to worried about removing the old batteries or using the units charging / bms, if I can it'll be a major bonus but there is room for extra charging / bms and socket. what I really need is that it charges from a 12 volt supply.
here's is what is what is already fitted, whats the best way to to got about this

Thanks

View attachment 198273View attachment 198274View attachment 198275
There are plenty of 7.4V [2S] Li-Po batteries of many different shapes/sizes and capacities for radio control models. Two places to look would be Banggood and Hobbyking. You will need a good quality [read safe] balancing charger,but reasonable ones start at around $45.00. Alternatively it's easy to make your own Li-on 18650 packs as the specific heatshrink/spacers/and tabs are all available-once again at Banggood and /or Aliexpress.
 

RPLaJeunesse

Joined Jul 29, 2018
86
The battery has 4 wires so the BMS in the 'scope has both balancing and temperature sensing, given that both are needed for safe battery management. The 7.4V rating is exactly twice 3.7V, so that is the nominal cell voltage the 'scope is designed for. The 6100mAh energy rating is a nominal value to give the required 'scope operating time when on battery. Anything within +/-10%-15% of the 6100mAh rating would probably work fine. I'd consider 2 banks of 3-in-parallel arrangement of new, identical (same lot), unprotected 18650 cells each accurately rated about 2000mAh (2Ah). That would give you a 2S array of about 6000mAh, close enough to the original. The one "gotcha" is the temperature sensor. One would have to measure the original (likely resistance, at both room temp and heated), then replace it with two sensors in series that are the same value. Why two in series? One in each bank of 3 paralleled cells. Of course, all this needs to be wired exactly as the original was. Or just get 2 flat cells of 6Ah and use the original temp sensor as you package them up: https://www.digikey.com/product-detail/en/jauch-quartz/LP906090JH-PCM-WIRES-70MM/1908-1377-ND/9560999
 
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Thread Starter

liteace

Joined Mar 7, 2012
135
The battery has 4 wires so the BMS in the 'scope has both balancing and temperature sensing, given that both are needed for safe battery management. The 7.4V rating is exactly twice 3.7V, so that is the nominal cell voltage the 'scope is designed for. The 6100mAh energy rating is a nominal value to give the required 'scope operating time when on battery. Anything within +/-10%-15% of the 6100mAh rating would probably work fine. I'd consider 2 banks of 3-in-parallel arrangement of new, identical (same lot), unprotected 18650 cells each accurately rated about 2000mAh (2Ah). That would give you a 2S array of about 6000mAh, close enough to the original. The one "gotcha" is the temperature sensor. One would have to measure the original (likely resistance, at both room temp and heated), then replace it with two sensors in series that are the same value. Why two in series? One in each bank of 3 paralleled cells. Of course, all this needs to be wired exactly as the original was. Or just get 2 flat cells of 6Ah and use the original temp sensor as you package them up: https://www.digikey.com/product-detail/en/jauch-quartz/LP906090JH-PCM-WIRES-70MM/1908-1377-ND/9560999
Super helpful, Perfect info, Thank you very very much, please could you help me measure the temp sensors, where would I do this at the battery plug also I don't know whether Ive a problem with the battery pack or the built in BMS as the charge indicator will got from yellow, charging to green. charged but then when I switch the scope on the corner screen battery level indicator is showing half charged, if I disconnect the battery pack 4 pin plug from the PCB whats the best way to test the batteries. Its a nice hand little scope and would like to get it up and running so I can get proper use out of it

Thanks
 
I will assume (high probability but no guarantee, sadly) that the 4 wires are battery low, mid, high, and temp sensor. A simple voltmeter test will identify mid and high, those we ignore since the temp sensor is most likely tied to battery low (again, no guarantee). That leaves the low and sense pins identified. Measure between them with an ohmmeter, both normal and reverse polarity. Same reading both ways - then it's a thermistor. Different readings - then it's probably a silicon diode. If a diode, the meter's diode function should indicate between 500 and 700mV to designate a silicon diode. Job's basically done, most any small silicon diode works. If it's a thermistor what is it at 25C room temp, and what is it when you put the battery in a waterproof plastic bag and let it sit in 50C water for a few hours? Look up a thermistor equation, fit the 2 numbers to the equation (I'd use a spredsheet to verify), and get the B25/50 "beta" value that describes how strongly the resistance changes with temp. Using the 25C value and the B25/50 beta number a replacement temp sensor can be chosen that matches the original.
 

Thread Starter

liteace

Joined Mar 7, 2012
135
I have a new soldering iron with a very fine tip. I had the scope apart again on sunday and reflowed nearly every solder joint, I gave it a charge and the charge light took just over 2 hours to change from the charging, to charged, its never done that before, normally after 10-45 mins the LED is showing charged but switching the scope on the battery level indicator is not showing full.

after the 2 hour charge the battery level indicator showing full, I let the scope run for 2 hours and it was down to 1/3 on the battery level indicator, charged it again. just under 2 hours and again its showing charged.

I hope the reflow has fix a dry joint
I'll make sure it gets some heavy use and see how it goes

Thanks all for your halp
 

Thread Starter

liteace

Joined Mar 7, 2012
135
Its been fine for the last 3 times I used and charged it, so I was dead happy, battery run time about 2 hours.
Ive used it again, Its charge time again and its playing up again.
Now Im pee'd with it so Im going fit the 18650's on the outside with their own independent bms/charger unit and just connect up the 2, power and ground wires to the scope and let the bms/charger take care of the rest with an extra jack socket somewhere for charging, something like this:

2s.PNG

what you guys think?

Thanks
 
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