Overkill Solar 120A 4s 12V BMS, Instruction Manual

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USB module and cable (optional)
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The BMS may be ordered with optional cable upgrade (C- and B- cables can be upgraded to 8
AWG, 12” or 24” cables. see section ​2.2.3​ for why this may be useful). Crimped copper lugs
may also be specified at order-time.
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A pair of ​power distribution blocks​, with two or more 3/8" lugs, rated for at least 150 amps (most
with 3/8" lugs will be rated for over 200 amps). We recommend a matched pair with one black for
negative, and one red for positive. These will be the interface between the battery pack, and the rest
of your system.
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An ​enclosure​ for your battery pack. Popular choices are:
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Overkill Solar sells a stainless steel frame for the 100Ah LiFePO4 batteries. This is arguably the
strongest and most durable way to build a battery pack, and would be suitable for mobile
installations, for example an RV.
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1/2" plywood is a very popular choice. This can be assembled in a few hours with very basic
tools. A pocket-hole jig (e.g.: Kreg K4) is the quickest and easiest way to attach 1/2" plywood
at 90 degree angles without splitting the material.
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Plastic snap-top battery boxes can be purchased for under $10.00, and are intended to be used
in a mobile setup (e.g. RV or boat). They have locking lids, adjustable dividers, two handles, a
recess for a mounting strap, and pass-throughs for large battery cables.
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Any large plastic box will suffice for a permanent, non-mobile installation. Storage boxes from
companies such as Rubbermaid and Sterilite are available in a multitude of shapes and sizes.
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Many DIYers will also choose to forgo the enclosure altogether. Typically, the electronic
components are mounted to a piece of vertical 1/2" plywood, and the batteries are usually
placed near the floor, but ideally elevated up a few inches. Sitting on a closet shelf is perfectly
fine. These cells do not offgas in normal operation, so they may be placed inside a living space.
Admittedly this setup isn’t for everyone, but it might be the right choice for some people.
2.2.2 Gather Consumables
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16-22 AWG Insulated ring terminals​ ​ (needed for the balance leads)​ . We include 3/8" ring terminals
with the Overkill Solar 100Ah LiFePO4 batteries, which have 10mm lugs. If purchasing other
batteries, you will need to provide your own.
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8-10 AWG ring terminals​ ​ (needed to connect the BMS’s pig-tail leads to the battery). ​ Crimped ring
terminals and longer pigtail leads are optional items for the BMS at the time of purchase. See the
Bill-of-materials in ​
Appendix B​ for exact sizes.
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4 AWG, 2 AWG, 1 AWG, 1/0 AWG, or 2/0 AWG stranded insulated wire, 3/8" ring terminals, and
heat-shrink tubing​ ​
(exact size will depend on the charge and discharge currents. See ​ Appendix B​ for
bill-of-materials for specific configurations. See ​ Appendix F​ for wire sizing guidelines)​ .
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Kapton tape​ ​ (needed to secure the temperature sensor(s). We recommend every DIYer to have Kapton
tape on hand. Buy it in assorted sizes)​ . If you don’t have Kapton tape, or don’t want to buy it, you can
use whatever tape you have laying around.
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2” gaffer tape​ ​ (optional; if you plan to tape your batteries together instead of fastening them inside of a
box or within a frame)​ We recommend gaffer tape because it does not leave a residue in most cases.
Duct tape works too, but gaffer tape is superior. And if you don’t have either of those, then any tape
will work in a pinch.
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Double-sided foam tape​ ​ (optional; place between battery cells to prevent them from sliding around, and
also as a convenient way to attach the BMS to the battery pack. ​ We recommend 3M™ VHB tape, and
this is what gets included with the 100Ah LiFePO4 frame kits).
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Light-duty 6” zip ties​ ​ (for wire bundle management)