Battery model recommendation

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There are also a few specific PicoCalc related issues that are buried on the forum.

For instance, if you want to use two cells, you should ideally have them fully charged when inserted, since having them be at different charge levels may not be advisable, as mentioned here:

My 18650 batteries vented when I put them in the PicoCalc

The picocalc is a single cell device - or more accurately, it’s a 1s device. If you put two cells in, they’re connected in parallel and are electrically identical to a single cell with twice the capacity. The AXP2101 is being used appropriately. That actually brings up another issue with using 18650’s here - if you put two cells in, they must be charged to the same level (within 0.1v!). Otherwise the higher voltage cell will pump current into the lower voltage cell uncontrollably. This is bad. …

If you’re only using one cell then this isn’t an issue.

There was also some discussion about overcharaging on PicoCalc, which seemed to be a flaw in the design. My interpretation of it was another reason why it would be a bad idea to use cheap or untrusted batteries in the PicoCalc, and may also be a good reason to choose protected cells over unprotected ones.

When should deliveries of PicoCalc start?

I myself have found a issue on two different picocalc boards where plugging USB into the pico will apply that power directly to the batteries and overcharge them. I have also seen it happen to someone on discord, but he had no clue it was overcharged (his orange charge light had the fast “danger” flash when he plugged USB into his picocalc). I had been in communication with Alex, but his reply was a bit vague on whether or not they confirmed the problem existed. I had asked them to put out an o…

I’m using the protected Samsung 35Es myself (two in the PicoCalc) because I had already bought them for the DevTerm and uConsole in the past, from a reliable supplier online. While they are probably overkill in terms of quality and capacity for the PicoCalc, they’re also arguably some of the safest to use. The extra length makes them a tight fit, but I don’t plan on swapping them out until they die, which may outlast the PicoCalc’s life itself.

While it can be avoided with some care, if you choose unprotected, and put them in wrong, then you’ll likely damage the batteries and the PicoCalc, as described here. And the cheaper and “sketchier” the batteries you use, the more likely this will happen too. Even if they are inserted correctly, if they are fake/damaged batteries that could happen. In general, anything advertising capacity over 3500 could be a fake and shouldn’t be trusted.

My 18650 batteries vented when I put them in the PicoCalc

They were unprotected batteries, and when I put them in my PicoCalc recently, I may have put them with reverse polarity, which caused them to vent. I instantly removed the batteries from the PicoCalc, and I don’t think any damage has happened to my PicoCalc’s battery holder. I need to buy new PROTECTED 18650 batteries.

BTW, this battery discussion post is tagged on the DevTerm forum. But I guess it doesn’t matter much these days since the DevTerm has been end of life for a while, and activity had dropped to nothing anyway. It’s just that other PicoCalc users with battery questions may not find it as easily since it’s here.