Lipo Charging

We’ve been discussing using a proper LiPo “smart” charger here. Not a cc/cv charger.

A proper LiPo charger will sense and properly recondition a battery if necessary.

What “smart” algorithm are we talking about? Just a variation of piecewise linear cc/cv states dependent on voltage and temp ranges? Or the higher end battery characterization chips that do soc/soh and coulomb counting then yes they are more sophisticated than cc/cv chargers, but they usually require a separate main controller to interface with for monitoring/configuration and would be wayyyy overkill for something like an arduboy.

In the case of the Adafruit Mico-LiPo Charger, discussed here, see the MCP73831 datasheet.

Yeah that’s an analog piecewise linear cc/cv controller. I wouldn’t really consider that a smart charger, but looks like it does uvlo and precondition trickle charging. Not sure though how safe it’d be on reconditioning unknown batteries without some sort of temp sensing to cut off in the event of thermal runaway.

Also, does the micro lipo have battery protection?

Were talking small, hundreds of mAh, single LiPo cells here. Not a Tesla Powerwall.

The Arduboy uses the same MCP73831 controller chip as the Adafruit Mico-Lipo. It should be noted that, due to a design mistake, the charge current programming resistor value is incorrect, resulting in an “unsafe” 2.8C charge current. See the discussion here. There have been no reports of any Arduboys overheating, blowing up or catching fire (although I’ve seen one report of a bulged battery).

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No, but most LiPo cells of the type you would use have protection circuitry built in. The Arduboy’s battery is an exception, which is why there’s a protection circuit on the Arduboy circuit board.

If you post a clear photo of your battery, we may be able to determine if it has its own protection.

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Yeah I was assuming extended battery mods and not the stock arduboy battery. I know a lot of the media hysteria of batteries randomly catching fire is way overblown, but I’ve had a few close calls on recycling cells from packs to know it’s also not completely a non-issue either lol.

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Is the protection that small circuit board in the yellow part?

Probably. If there’s a circuit board, it will be for protection.

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This is what my battery looks like (sorry if it’s flipped!)

Yes, that circuit board in the battery is for overcharge/overdischarge/overcurrent/overvoltage protection.

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Alright so I keep on forgetting but how do I wire up the micro lipo to my arduino, as well as wiring up a 3 pin slider switch to turn the console on and off?

Assuming you’re powering the Arduino with the raw ~3.7V battery voltage:

Battery+ and Battery- to charger.
Charger GND to Arduino GND.
Charger BAT pin or battery+ to switch.
Other side of switch to Arduino VCC.

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What do you mean by that?

No regulator to boost or drop the voltage (the same way the Arduboy does it). This has already been discussed in the topic you started here:

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I disagree? A battery’s chemistry, construction, and size is what determines, well, everything a battery is capable of. And to say that the mAH has nothing to do with the maximum current a battery can provide is just factually inaccurate. Doing some quick research, every source I find is saying that to find the maximum current you can provide with a lipo you need two pieces of information: the capacity, and the discharge rate. Most lipo batteries discharge at a 1C, meaning a 250mAH battery can provide a maximum current of 250mA.

So I stand by what I originally said. mAH determines the possible amperage, with the other factors being discharge rate and load. That said, I wouldn’t have found that out had you not said anything so thanks :slight_smile: I didn’t know discharge rate would be a key factor but it makes total sense.

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So if I remember correctly, the battery will take longer to charge at 100 mA, and it will charge faster at 500 mA. But it will take longer until the battery is dead, and vice versa for 100 mA. Do you think that 500 mA is better? Or with 500 mA there isn’t much battery life and 100 mA is better?

No. A battery’s discharge current is determined by the voltage at the battery terminals and the resistance of the circuit being powered. Current (I) = Voltage (V) divided by Resistance (R).

The maximum 1C discharge rating is for continuous current and is specified for safely running without overheating. That says nothing about the instantaneous current that a given battery could provide, which could be much higher. This is all determined by the battery’s internal impedance. However, for a given series of batteries of similar construction, those with a higher mAh rating will likely be able to provide a higher peak current due having a lower internal impedance.

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No. The charge current only determines how long it will take to charge. Once the battery is charged, it will last just as long (when powering the same circuit) regardless of what current it was charged at.

Charge current can also have an affect on the number of total charge/discharge cycles you will get from it. Charging at a lower current is generally better for the life of the battery (within reason).

Another thing that affects the life of LiPo cells is the amount of charge and discharge. It’s better to only charge up to about 80% of a full charge and discharge down to about 10% of empty. However this is difficult to accomplish with the circuitry used by the Arduboy.

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