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Forum Index : Microcontroller and PC projects : Picomite Battery Power
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| Swiftwind Newbie  Joined: 07/07/2025 Location: United StatesPosts: 10 |
I'm in process of building a couple LCD Picomites, and was looking for advice on battery power. Im planning on using 18650 batteries, they will connected to TP4056 lithium battery chargers, and I was lead to believe that I should use MT3608 Boost converter modules with them. One PicoMites I'm building is going to have a 7" LCD, and a second Pico running as an active USB TO PS/2 adapter so I can use it with a 60% mechanical keyboard... which I'm having a hard time finding without backlights. While it seems pretty obvious, I was initially going to power it with 2 18650's, but I'm thipnking I'm probably better off going wit 4 cells. |
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 8232 |
Quite likely. The Pico isn't terribly good on batteries as the RPnnnn chips don't have an accessible low power mode under MMBasic. The interpreter has to keep running. You can forget keyboard backlights - there'll be a way to turn them off. :) The big battery killer will be the LCD backlight probably. They can take quite a bit of current. If you run the PicoMite from it's built-in switcher supply the input can drop down to less than the low voltage drop out protection point of a lithium cell. Most LCD displays will be fine at that too, but as usual it all depends where they stop working. If the display is ok down to 3V then it might be an idea to parallel two 18650s rather than series them. If the display simply has to have 5V then a boost converter would seem to be the answer, but they aren't terribly efficient. There would be plenty of current available though. Personally I wouldn't like to charge from 5V, up convert to 7V2 then have to down convert to 5V for the display and 3V3 for the Pico, although you could. It just seems messy to me. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| dddns Guru Joined: 20/09/2024 Location: GermanyPosts: 673 |
I have a setup with 2 Sony VTC6 3Ah. With a 7" at 100% plus hub and keyboard and another Atmel and small LCD controlling the power = 0,65A at 5V. And that really runs for more than 1,5 hours. With 30% brightness it takes 0,4A and runs about 2,8 hours I use a 2S BMS and a stepdown converter with LM2596S. Nowadays I would use these mini 3A converter. It can be charged while operating like a UPS Edit: For charging I use a 12V 2A power supply and a constant current stepdown converter set to 2,5A at 8,7V. That's a bit more than 20W and from 0% to 80% it take some minutes. I wouldn't use 5V as power source either, I've seen some blowing up when the load is over their limit or the charging time would be long if you limit the current so much Edited 2025-09-28 04:58 by dddns |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8232 |
You can, of course, get USB-C PD chargers now (you might need a separate cell protection module). One of those would be very efficient if using 18650s in series as the charging voltage would be high enough to feed the charger directly. There could be one (if 3V3 will do for everything) or two (if you need 5V as well) buck converters to get the supply rails. These are much more efficient than buck or buck-boost converters. The little 600mA S09 boards would probably be ok up to 15V input. The EN inputs could lock them off during charging. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Swiftwind Newbie Joined: 07/07/2025 Location: United StatesPosts: 10 |
This is another of those situations where I know just enough to start off in the right direction, but not enough to get to quite the right destination without inadvertently taking the scenic route. The first set of parts I'd gotten were half right, more inline with a single 18650 rather them multiples. A second set of I ordered takes care (I think) of multiples, but it was the BMS part I was missing, so ordered several of them... and then some all-in-one battery boards, because hell, who doesn't need more spare parts. Given what you all said, and a few examples I found, I think I got it... Puffs of blue smoke will tell. |
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Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1646 |
Maybe you should have a look at the Game*Mite. https://github.com/thwill1000/mmbasic-gamemite Bill Keep safe. Live long and prosper. |
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| Swiftwind Newbie Joined: 07/07/2025 Location: United StatesPosts: 10 |
The Gamemite uses the TP4056 pretty much how I though it worked, what I'd missed is how many cells it supported, and how to configure it for 2. Once I got that, the inclusion of the boost module in the examples I'd found made sence. the BMS suggestion was the part I missed, and answers a lot of questions. Currently, I've got enough parts on the way to try it a couple different ways, and I'll go with what ends up fitting into the enclosures. |
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