Greetings, my YouTube friends, in this video I will repair and improve This battery. It’s from a Black & Decker brand drill by Samsung The first step is to know the characteristics of the old battery and also the one I want to build This battery is Nickel / Cadmium These batteries are not bad Their useful life is quite long, they have about 3000 charge and discharge cycles These batteries have a very strong memory effect If we charge these batteries when they still have power left, they will never fully charge This does not happen with lithium batteries, although all batteries have a memory effect The electrochemical pair of Ni-Cd batteries It is made up of nickel and cadmium, hence its name The electrolyte contains sodium hydroxide, which is very corrosive what’s inside the battery is poison that’s why I’m going to transform it into a lithium battery The energy that a battery can store in the form of chemical reagents is calculated:
Just a single one of these little batteries When you connect batteries in series The voltages of both batteries add up (3.7 + 3.7 = 7.4 Volts), but the capacity is the same (3.6 A / h) but if you connect the batteries in parallel, but as the 3 groups are connected in series, the capacity is maintained (11.1V and 7.2 A / h) The real battery voltage when fully charged is 4.2V (4.2 + 4.2 + 4.2 = 12.6V) the capacity is maintained (7.2 A / h) 79.92 W / h (new battery) and 20.4 W / h (old battery). the difference is abysmal It is called BMS circuit (Battery Management System) BMS module is very easy to connect
With a Torx tool, I unscrew the four bolts of the battery´s top Provide enough space to fit the 6 18650 batteries there is enough space There are the connection terminals. I´m going to cut the wires
so I will not have problems when I put the 6 18650 batteries inside the case I have already modified the case. Keep in mind that you don’t just have to put the batteries inside Also the battery holders and the BMS module must be inserted inside the housing or a polyurethane adhesive continuing with the Ni / Cd to lithium ion conversion process The BMS module is of paramount importance in any lithium battery I am going to explain what the BMS is, why lithium batteries need it and not others, and how to choose the most suitable one for our battery and most importantly: How it connects BMS is an acronym in English, which means “Battery Management System”
The most common batteries; Pb / acid, Ni / Cd, Ni / MH, do not usually have this circuit because they withstand overcharges well, for example car batteries when fully charged And in alkaline batteries (Ni / Cd and Ni / MH) something similar happens And in the case of alkaline batteries, they withstand deep discharges well, which is not the case with Pb / acid batteries In addition, Ni / cd batteries had to be fully discharged to avoid memory effect problems But these batteries do not tolerate overcharging or deep discharge. They can also be dangerous being able to explode or catch fire when the battery is fully charged the BMS stops charging When the battery is deeply discharged, the BMS interrupts the circuit when the recommended minimum voltage level is reached A very important function of the BMS This is very important in batteries made up of several cells, as is the case 6 18650 batteries Now I am going to choose the most suitable for this project in this case, 12 V The BMS for a power tool must be able to withstand the passage of very high currents
support those current levels without problems, reaching peaks of 60A the BMS connections are as follows: P+ and P- The connections marked as B+ and B- are the connections through which the battery is charged with all cells connected in series those connections are to individually load each cell or group of them here we have it P+ and P- B+ and B- and finally, B1 and B2 here we can see the 3 groups of batteries connected in series
And the negative terminal of the battery, connects to the B- terminal of the BMS terminal B1 of the BMS connects at the junction of group 1 and group 2 BMS module is very easy to connect The BMS could have been made by me, but it’s not worth it cheapest the box full of battery supports, cost me 2€ little bit money Now I have to wait for the batteries and nickel to be sent to me so that I can solder them and start the assembly Thanks for watching !!!!