Knowing that most lithium batteries sold from China have extremely inflated capacity numbers, and knowing it’s usually around 2-3 times as high as the real capacity, I decided to take a calculated risk and order a lithium pack direct from China via Alibaba.com. This particular unit started to appear on Alibaba not too long ago, and very recently they are showing up on eBay.
This pack was billed as a 12v 100aH unit with integral BMS made of 18650 cells. I got it for $159 + freight. I already see these going for around $700 on eBay. Let’s see what arrived in the mail.
The listing claimed 120a max discharge rate. Label says 110a. “Made In China” has a typo…
Somewhat sloppy label application. I have no idea what it says.
Label says LiPo pack. That would NOT be 18650 cells. Also, the aH is not checked off.
Camo carrying case. Kinda neat. Not sure about strapping a giant LiPo pack to my back though!
Initial charge. Battery arrived essentially depleted. Charger is rated 10a, so it should take 10 hours to fully recharge.
I had to see what was REALLY inside. It’s a LiPo pack; no 18650s in there!
There’s the BMS, and USB DC-DC converter. The BMS is attached in parallel with the load posts and charge port, therefore I presume the charger is just a dumb switching power supply and the BMS is integral to the pack. This means charging from an external solar controller should be fine.
We have 3 sets of 5 LiPo cells in parallel (known as a 3s5p configuration). That means each cell should be 3.7v nominal and 20aH in capacity.
As of 2pm today the pack is still recharging. It’s been taking 10a from the charger for almost 3 hours so far. I’m roughly estimating true capacity at 60aH but this will be determined in time.
Update December 30, 2016: It’s now been about 5 months and the battery has been in service as part of the solar power system on my Tacoma since I got it. It’s charged with a 285w solar panel, Blue Sky MPPT 3024i charge controller set to 12.5v max charge. Even though the battery says 12.6v is full charge, I figured to play it safe with a LiPo battery in my truck and slightly under charge it, which coincidentally is what EV manufacturers do to prolong the battery lifespan:
So far, so good! I believe this battery may be close to its rated capacity after all. If I leave my truck in the garage for 24 hours (no sunlight at all), and considering the controller + loads at rest draw a constant 1a or so, I lose approx 1/4 the capacity per day based on a lithium battery voltage to charge ratio chart.
I now see on Alibaba that the same manufacturer has a bunch of new offerings. Bigger batteries in the same style. The descriptions also have been updated to not say 18650 cells and instead say “Li(NiCoMn)O2” prismatic cells. It’s a LiPo as far as I’m concerned, though they don’t use that term. Now they also have ones in red cases that say 18650s. I really want to buy more to test out.