Plus, I don't have a spot welder that can deal with the thick interconnects.
And to obtain similar 30A rated batteries, I'll spend more on cells in small quantities as I will on a brand new pack. You're better off buying these packs to extract the HB4s than you are rebuilding them! I can buy the 3.0Ah battery packs for $40-$50 shipped, all day long. eBay isn't any better, at around $5/cell. BatteryBro has LG HB4s for $4.57/ea - in quantities of 50. If I can't - then there's no real point in the labor to rebuild it.įor me to buy 10 of these cells, I'm spending basically as much as a new pack. If I can rebuild the pack radically cheaper than I can buy a new one, I'm likely to rebuild it. You can buy them in nearly endless quantities at your local hardware store.Ĭost is my other main consideration. there are are over 800 listings on eBay - so not rare at all. How hard is it to get a DeWalt 20V Max pack? Well. If that's the case, rebuilding it makes a ton of sense. How rare is the pack I'm dealing with? For some of the packs I've rebuilt, they're rare, and either very difficult or impossible to obtain a replacement for. I make the decision to rebuild or not based on two major factors: Rarity and cost. What likely happened is that one of the cells shorted internally, and the other one dumped its current through as well. But these two cells aren't even nailed to their perch. Not knowing the pack history, I don't know if it was a cell defect, or if something happened to it. It seems like it shorted out and overheated, or overheated and shorted out. The plastic wrapper on that cell is incredibly brittle compared to the other cells. This cell is the 20mV group - even after charging. The observant reader may note that the cell in the middle here, with the model clearly visible, looks a bit off. These are hardcore power cells - a single cell at 30A is putting out over 100W! The low capacity (1500mAh - below half of what a high energy cell can do) is the price you pay for a cell with that kind of power output. With batteries, one can generally get a lot of energy (watt-hours) or power (watts), but not both. People have tested this cell (it's popular for vaping as well), and it's a legitimate 30A cell.
This is a solid, solid choice for a power tool pack - and not a cheap choice either! DeWalt didn't cheap out here with last year's discount cells. They're in every way better than the early lithium ion chemistries. This is one of the newer chemistries, which is nice to see. This works out to be a LG HB4 cell - which is a 1500mA cell rated for a 30A discharge! The battery chemistry is NMC (Lithium Nickel Manganese Cobalt Oxide or LiNiMnCoO2). One of the cells is very conveniently oriented so I can read the model number. I hear a rumor that things like center pins mean they're a "Security Bit" intended to keep people out. These, obviously, don't work with regular Torx head bits. Pulling the pack apart involves removing 4 Torx screws with center pins. If the voltages are accurate, there's something seriously wrong with this pack. You'd expect to see a nicely balanced pack like mine, not a voltage horror show like this. That's a stone dead cell bank, if it's accurate. I did double check this, thinking I'd made a mistake in transcribing numbers. Charging almost all the way (but not quite to 100%) means they'll last longer on the shelf when charged - and most people store tool batteries charged.įrom this "dead" pack right off the charger? Let's see! This is great news for longevity - sitting at 100% state of charge (which, for these cells, is 4.2V) is bad for calendar life. This is great news for testing a pack!Īlso of note is that the cells are charged to 4.1V instead of the more typical 4.2V. Conveniently, this also means that the cell group voltages are externally accessible. The per-cell voltages are almost identical (within 0.01v), which means a well balanced pack in good condition. My pack is fully charged (20.43V, 3 LEDs, solid charger light). Everything is measured relative to B-, with the relative voltages from the previous reading in parentheses. I grabbed some voltages from a good pack of mine (I've got 2 good 20V Max batteries).
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