B300 connected to PV for long period

Is it ok to leave my B300 connected to the PV panels for a couple months? The unit won’t turn off if the panels are plugged in. When I return in a couple months I would like the unit to be fully charged when I arrive.

The important question you have asked—what happens when a lithium power station is continuously charged—is at the heart of many posts in this forum. In a better world, manufacturers would clearly explain the facts, but that’s not how marketing works.

A basic property of lithium batteries is that they suffer slow damage when they are in a fully charged condition. The longer they spend in the fully charged state, the more damage accumulated. (That damage reduces their energy storage capacity.)

For a device with a lithium battery that is used intermittently, one can prolong the service live of the battery by storing it at a reduced state of charge. For example I fully charge the battery for my electric lawn mower the night before I plan to use it. When I’m finished mowing I leave that battery at a moderate state of charge. A power station (e.g. Bluetti) used for planned events (e.g. camping trips) should be managed similarly—store at moderate state of charge, charge fully before use.

Other devices with a lithium battery are used continuously. The mobile phone is the prime example. There are no “storage” periods—you use it every day. You can’t do much to alter the lifespan of the battery. Some Bluetti customers want to use their power stations as uninterruptible power supplies, which requires continuous operation of the charging device and continuous operation of the inverter. The battery is going to be at a high state of charge almost all the time. It’s lifespan is inevitably shorter than it would be if used once a month for camping, and stored at a moderate state of charge. Using the Bluetti that way is not “wrong”—you just have to expect a reduce lifespan of the product.

Your situation is the same as people who buy power stations to use at home in a power failure. The power station is needed infrequently, but when it is needed you would prefer that it be fully charged. You can choose to store it fully charged, and accept a reduced life span for the battery. Or you can choose to store is at a lower state of charge, and expect a longer lifespan.

Alas, Bluetti provides no quantitative information to help us make this decision, e.g. a plot of storage state of charge vs damage rate.

After that long preamble, I can finally say that yes, it is “ok” to leave your Bluetti continuously charging. Nothing will immediately break. But the lifespan of the product will be reduced (by an unquantified among), compared to what you would get if it was stored at a moderate state of charge.

One final, important point. Numerous references on the web say that the temperature at which a lithium battery is stored is very important. High temperatures really damage them. (That’s one reason why there are no lithium car batteries.)

2 Likes

Thank you Landlocked for the explanation. I was somewhat aware of what you said but you clarified some of the details.
My primary concern was the electronics being on continuously for months at a time. It would be nice if Bluetti could design a limiter into the controls (like Tesla does) so you can adjust the percentage of charge.
I don’t always have time to charge my unit before I leave and don’t want to leave it at 20% for months. Like you mentioned, there are various applications for the way people use batteries and, right now, Bluetti is a one size fits all situation. Maybe the next generation of products will be a little smarter.

If it was my unit, i would leave it charged up to about 70%, make sure it was hard shut off (long depress to be 100% sure it is fully off, and not in standby!) and not leave it connected to any power inputs.

It does not matter what brand or chemistry of Lithium solar-generator, i just don’t feel they are 100% safe to leave connected if un-attended for more than a week or so. What if it caught fire? etc.

It would be nice if Bluetti could design a limiter into the controls (like Tesla does) so you can adjust the percentage of charge.

I second that fine idea! I believe the Goal Zero power stations have this feature. (But at the time I bought my Bluetti, GZ was using an inferior battery chemistry.)

The AC300 has an upper and lower limiter.

  1. LifePo4 is a lot safer than Lithium Ion.
  2. I think fires are associated with heavy fluctuations in load and charge.

I have B300 units and when switched off they keep the charge and drop very little of it due to time. I suggest keeping them off. The Sun will continue to power the PVs but if you cannot use it, don’t try to store it, unless you have a huge battery bank