Quote:
Originally Posted by ElectroBoy
Hi
@ Bumbo
, what operating guidelines would you recommend for using these type of batteries to get the best performance and longest life? I have the Jackery 500 WHr Li-ion NMC battery. I contacted the vendor asking about how low I could deplete the battery while powering a DC fridge before recharging. They said not to let it get to 0% but to recharge at about 15%. Does that sound about right?
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It most certainly does sound about right if you are trying to be nice to your batteries. Same goes for lead, but lithium has a much deeper discharge allowance.
Generally speaking... If you need the power, you can use significantly more of the stored energy from a lithium cell than from lead without causing harm or damage to the service life of the battery.
If the goal is to significantly increase the service life and general health of a lithium battery, then there are fundamentals worth understanding...
Unlike lead batteries that want to be kept at near full or float/maintenance voltages when not in use, lithium batteries (in an ideal world) want to be stored at their nominal voltage, which is about 50% state of charge.
I have had cells in storage for 4-5 years without any maintenance and did not show any signs of capacity loss, voltage drop, or degradation when stored correctly.
If you ever owned RC toys that uses LiPo batts you might be familiar with the "storage" function of the chargers which do just that, put the batteries at their nominal voltage, or close to it.
Now in the real world, most people are not going to keep their lithium power banks, flashlight batteries, and other devices sitting at 50% all the time. But even on it's worst day, charged to 100% and discharged to 0%, it will likely still have a longer service life than a lead battery.
But if you keep the cycle depths closer to its nominal voltage, for example 80% max charge and 20% max discharge, theoretically that could significantly increase the amount of cycles/service life.... could be hundreds, could be thousands, it just depends on the cell chemistry and quality of batteries used in your Jackery. It's always a good idea to have more power than you need as well because you leave some power on the table with this strategy.
Conversion about quality: I have a friend that did some full charge/discharge cycle testing of some 18650 cells … here is an example of the degradation between a quality brand name cell from Samsung and a Chinese imported cell "Re-Volt"
It held up well to about 360 cycles and then the imported Chinese no-name cell starts to degrade at an expedited rate. It's certainly enough to get a product past its warranty period. I'll have to ask him if he ever did the same test at reduced depth of charge/discharge but it's a clear indicator of "you get what you pay for"
This is the reason I like to build my own... no idea what these OEMs are using. I have limited confidence the commercial portable power packs, but I have not confirmed if the batteries they use are good for the long haul either. That wasn't to discourage anyone from buying one because I know DIY isn't for everyone.
The battery in the above photo came out of a production EV car that was salvaged... it's Samsung SDI cells, and the spec sheet rated for 6000 cycles at 80% capacity retention.
For running a fridge... I don't even worry about it. I'll probably sell the batteries or get tired of them before it's even a concern.
You could get the same quality buying a premium lithium battery from a company like Battleborn, Valence, or other brand of known quality and making your own, but EV cells are pretty easy to source these days for cheap, but you have to do some additional work and wire up a battery management board.
Hopefully not too much rambling, but I felt it was relevant. And that was me trying to keep it short lol...