LTO (Lithium Titanate Oxide) batteries have some huge advantages, for example, amazing longevity - more than 20000 cycles under normal conditions, i.e. not very high or very low temp, charge and discharge current not exceeding "normal" 0.5C for lithium batteries; extremely low internal resistance (fractions of a milliohm) and as a consequence extremely high working current output in the range of hundreds of amps; they have a much wider range of operational temperatures going to as low as -30 deg C retaining normal charging capability; they can be charged in just 6 minutes from 0% to 100%.
However, two of their main disadvantages are relatively low energy density (about 1.5-2 times less than LFP) and very high price.
I wanted to use the batteries for powering my computer from solar panels, so I'm currently playing around with technologies around that and selecting parameters for solar panels/batteries/controller/etc.
So, this is my honest experience of buying LiTiO4 batteries on AliExpress for a small solar generator. The purpose of this video is not to tell you the sob story of how I was essentially lied to and robbed but to prevent people from falling for the same trap.
Sorry for the subpar video quality for the most part. In the end, I realized that I recorded most of it using default camera settings which for some reason was something very bad - like 1280x720 10fps if I'm not mistaken... yeah, something THAT terrible. Luckily, almost all of it went into the time-lapses, so it didn't really make that big of a difference at the end of the day.
Couple more clarifications to the video. All tests were performed as follows: batteries were charged up to 2.5-2.6V and then discharged to about 1.9V. These numbers were chosen because the cells have just a couple percent of their capacity outside of this range, so it doesn't really make sense to pump them up to full 2.8V (or 16.8V for 6S configuration), for example. Besides, my inverter has OVP cut off at about 15.8V and UVP cut off at about 10V (and starts beeping at about 10.8V), so pumping cells up to a 2.8V effectively switches off my inverter together with the load (that's tested in reality :)). Thus, starting voltage for the tests was about 15.3V - 15.6V for the whole pack, and I cut off discharging manually at the voltage of 10.9V - 11V cause below that my inverter starts beeping very loudly and my kids were sleeping already during some of the tests, so I didn't want the inverter to go off and wake everyone up in the process. Besides, at that point battery doesn't have any usable capacity left anyway, so it just doesn't matter if I cut them off at 10V or 11V. The difference will be negligible.
I performed one more test that I have not recorded. That one was for a full 6S4P assembly - all the batteries I currently have. That test ended up yielding a surprisingly big capacity of 141Ah which is better than I would expect from 62 + 31 + 40 = 133Ah based on the tests performed in the video, but it still falls short of the advertised capacity. It calculates to about 33.5Ah per string of new batteries... but it still is far from 40Ah which they are labeled as.
And the store in the question is here: www.aliexpress...
I think they deserve to be widely known. What do you think?
12 окт 2024
