Types of lithium batteries according to its composition
The lithium-ion battery technology has improved a lot, and the advantages of have no memory effect and greater energy density per kg than any other current technology, we can add that depending on the type of materials used, allows different power/energy density; We can have powers instant from 1 c (2A/hour for a 2000 mAh cell) of the typical LI-Cobalto notebooks up to 5 c manganese (LiNiMnCoO2) or even for the last 15 c used in the automobiles (LiNiCoAlO2) or 30 c with LIFePo4.
In a device of high demand instant as a drill we have to employ lithium/manganese or lithium/phosphate (LiFePo4), with less energy density but more specific power; If we use the usual economic and with high density LiCoO2 is would faster, degrade although they may serve if we make packs of several in parallel to meet the greater demand instant or limit the power with protection circuits (which often come already built into most battery Li-ion battery being sold loose).
Choosing the most appropriate configuration of batteries
Playing with the number of batteries in series we get the total voltage, and playing with the number of batteries in parallel of each cell got different total capacity and secure download speed (C). If we have 6 in parallel in each cell in 2A (2000 mAh) batteries each, will have 12A altogether, what gives us, if they are 2 c each, a capacity of 24 Ah-safe loading/unloading.
The famous "C" gives us the maximum download speed in relation to their ability to safely; If it is 1 c and has 2400 mAh capacity, it comes to say that we can get 2400 mAh at 1 hour. If it was 15 c, it could give us 2, 4A in just 4 minutes "intense". The lithium/cobalt used in laptops usually have 1 c.
If the lithium we do a range of voltages that the device in question to work (varies between 4, 2V fully charged to discharged 3V), always can use the LIFePo4 (with a suitable charger), with a range of work 3, 2V charged (up to 3 .6V fully charged) and 2, 5V download limit unless they degrade significantly.
Note: The total mAh total capacity of each unit in series; gives them in this case if we put 3 rechargeable Li-ion battery 4, 2V of 1500 mAh each, get a battery of 12, 6V and 4500 mAh capacity (which is equal to 4.5 Amps).
Repairing the battery
For the para la reparacion repair I have acquired "Trustfire" batteries with a capacity of 1500 mAh with control circuit loading and unloading that prevents the battery of uploads and downloads over allowed values, also if a current greater than 3 amps (possible short), disconnects the battery.
He could have welded directly batteries retaining your circuit board (PCB onwards), but I preferred to remove it and apply it directly to each pack of three, so balance the capacity of each automatically and the control is carried by each pack of 4, 2V which is what interests us.
These control circuits would not be worth if you need more than instant 2A, in that case would have to use other types of batteries (that accept more charge/discharge current) and different PCBs.
This model of batteries carry a plastic and positive pole (as if the PCB had subsequently added to its manufacturing), so it can start external protection coverage to let them original blue and raising the positive button, then leave them without PCB:
We proceed to weld together on the one hand, positive and negative each other on the other, 1.5 mm2 fine wired. It is sufficient (12V 2A) (here you can calculate cable size according to voltage, amps and length), and weld the pole B-the PCB to the negative pole of the pack, and the B + to the positive pole of the pack, leaving the PCBs to one side over so that we do not reduce space, since the hollow of battery 837621 is very limited.
Do the same with three packs, in a way that to put them in series it only remains for us solder the positive of a pack with the negative of the other, taking into account the two going in the bottom of the box take up PCBs (facing the positive and protecting with duct tape), and that goes over in the middle to take you to one side, because we are also limited in height:
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| The soldiers packs in series: positive to negative of the following PCB |
You can see that it is a pack of 3 in series with 3 parallel (3S3P).
Nomenclature: see in internet pages that refer to batteries with formats like "Lipo 3S6P" and the like; the s series and the P in parallel). Example: 3S2P: 3 packs of 2 cells in parallel connected together in series.
And only it remains for us to place the packs in place taking great care that the Poles are well insulated with tape so that there is no short.
Attention: A short circuit or overload a battery of this type is dangerous by the great capacity of energy stored by each battery; If working at a temperature above 60 ° C, they could ignite. So much care when soldering,not you stay longer than 30 seconds heating you one of the poles when welding!
Only it would be welding the negatives of the box (Brown) to the PCB of the lower pack and the positive (blue) to the upper pack plus and then isolate so there is no danger of short.
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| Already repaired battery |
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| Another example of 3 packs connected in series; one of each pack is different brand but same capacity. |
Cover and seal with duct tape:
We can only get a 12, 3V minimum, and between 1 and 2 amp charger, 13V recommended to charge the batteries; Thanks to their control circuits will automatically disconnect one time to reach the limit of voltage charge or discharge (4, 2V-2, 5V); with one 2A will take to charge 2 hours and half this pack of 4, 5A.
