Second Life UPS Mark II
The final method is to attach the cells along with 8mm huge nickel strips utilizing spot welding. With the intention to facilitate cell voltage verification and equalization
inside every of the 24P blocks first just one facet of the block (the constructive cell terminals in my case) is welded first, then cells cost is equalized after which the second
cell terminals (unfavourable cell terminals in my case) are welded collectively. Most welds are carried out with 0.1mm and 0.12mm nickel strips however the terminal connections for the
whole battery are constructed out of 0.3mm strips for designed present capability.
A welding jig is used to maintain the cells in place throughout welding. Such a jig might be bought or manufactured by your self because it’s merely a set of 4 items of wooden
with a protracted slot minimize alongside their size. The design for such a jig might be discovered under:
The cells for every of the 4 24P blocks are inserted into 4×2 cell holders refurbished from outdated “hoverboard” battery packs and aligned utilizing the jig.
That is really useful because the welded nickel strips can’t be used as the one mechanical help for the cells:
Nickel strips are secured to the cells utilizing small neodymium magnets to not transfer in the course of the welding course of:
The strips are welded to the cells utilizing a kWeld from Keenlab spot welder powered by a HV Stock Spec GRAPHENE-3 7300mAh Hardcase battery – 7.6V LiPo – 130C/65C.
The impact of welding each 0.1mm and 0.12mm thickness strips that join the cells might be seen under:
The cells in all 4 24P blocks are first checked with a voltmeter and if a few of them have self-discharged under 4V they’re charged individually. I take advantage of a DIY “charger”
which connects collectively 5 low-cost “Li-Ion charger” modules primarily based across the standard TP4056 chip.
The strips used for terminal present collectors (offering the constructive and unfavourable for your entire battery) are longer than the size of the block to be bent collectively
and soldered to 4mm² wires.
In any case blocks are welded and equalized they’re aligned side-by-side within the welding jig and linked with extra 0.1mm/0.12mm strips. This course of might be seen under. Care wants
to be taken at this stage so as to correctly orient the blocks making an allowance for the polarity in addition to last wiring within the enclosure. A fast photograph abstract of
these steps might be discovered under:
Further recommendations on the cell welding course of are:
- take some outdated cells and follow welding settings and approach with totally different nickel strip thickness earlier than beginning to weld the battery
- as a rule of thumb for a correct weld, once you pull off the strip from the cell there must be a maintain left within the strip, in different phrases the weld must be stronger than
the nickel strip itself - hold the cells and nickel strip clear (degrease with isopropyl alcohol if required) and use work cotton gloves throughout meeting
- for finest outcomes use pure nickel strips, some locations promote nickel plated metal strips that are cheaper however have extra resistance