New GoPiGo3 Battery Discussion

ModRobotics is now offering a 3000mAh 3A 3S1P Lithium-Ion rechargeable battery for the GoPiGo3:

Prior GoPiGo kits shipped with an (empty) 8-cell battery holder that sometimes did not hold the cells securely, and required users to either purchase individual cells and a charger, or to purchase a Dexter Industries Rechargeable battery and Charger set.

In another thread:

Out of an abundance of caution, and to future users’ benefit the GoPiGo3 kit now ships with the above rechargeable battery at a price much less than the prior kit plus the separate rechargeable battery/charger.

Some questions:

  1. Does the new battery come with a DC supply for charging?

  2. I believe the current GoPiGo3 “red board” has a low voltage shutdown feature, and I read there is a new GoPiGo3 “red board” in process. Is the new board going to continue to support the existing low voltage shutdown feature (even though it cannot be triggered by the new 3S1P Li-Ion battery)?

  3. I believe the battery voltage sensing on the current red board maxes out under the fully charged 3S Li-Ion voltage. Will the coming GoPiGo3 board have a different voltage sensing range?

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The new rechargeable battery does come with its own smart charger. The smart charger is also good for 50V, 220, as long as you have a pin converter.

There is no new red board coming. There’s a slightly changed top acrylic, but no red board changes.

I hope this answers your questions.

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That is good news to my ears. Thanks.

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How do we get this “new battery” especially if we are stuck overseas?

How long does it take to charge from a “fully discharged”, (at lower limit), state?

Does it have low voltage protection? (i.e. automatic shutdown once the voltage gets too low.)

And the most important question of all:
Will @cyclicalobsessive’s wife let him bring them into the house without a built-in fire suppression system? :wink:

  1. From the specs, charging is at 500mA so I expect a full charge of 3000mAH would take 6-7 hours. Less if the battery is not discharged fully of course.

  2. From the battery web page:

Screen Shot 2020-11-05 at 8.18.08 AM

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Perhaps search your local Amazon for “Talentcell 3000” ?

Otherwise the web page says:

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Damn my eyes! I totally missed that.

Gotta get myself new glasses…

I still gotta figure out how to get one, or two, or so over here in Darkest Moscow.

Every thing I’ve found so far is a raw pack at 11.1v, no circuitry, no charger.

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Carl is very happy with an elastic band around his eight NiMH AA cells inside his belly. (I also have a spare holder and cables for him.)

My wife took Carl’s credit cards away until he is able to fetch take-out. I, on the other hand, have discovered “shopping therapy”.

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Back when I was investigating Li-Ion, I ordered a 3S1P 18650 holder with the battery board in it and a “1A” 12v wall wart (“1A” turned out to be for 220v, only 395mA at US voltage). My tests (outside on the patio) showed I would need to buy high quality Li-Ion 18650 cells to do better than my NiMHs.

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The rechargeable battery pack is definitely Li-ion 18650 cells. We hope they are high quality! They passed all our tests, and TalentCell is a serious battery manufacturer.

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What unit of measurement is “C”? It’s obviously not temperature.

Given these numbers, what number would you use as the “ET-Phone Home” voltage to send Carl back to the charger?

The difference between “charged” and “discharged” is 5v for the entire pack? Doesn’t seem like much. . . .

What are the conclusions that you drew from this data?

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Folks talk about charge and discharge rates in terms of x.yC where C = the capacity of the cells in milli-amp hours mAH. So charging is often 0.2C to 1C, and discharge is some “design rated” based on the application.

For my my FPV quad’s “high voltage” (4.35v) 450mAh 1S LiPo cells are rated 30C (~13.5A) but my quad only draws a max of 6A for a discharge rate of 13C.

The 18650 cells I tested were low quality, and delivered only 1700-1800 mAH to total shutdown.

Using 1750 as C, the 395mA discharge rate is around 0.2C.

“Playing” till the 10.5v “knee” would give about 4.5 hrs of playtime and only 15 minutes of “reserve for poorly aligned dock retries”. I probably would choose a voltage that allows more reserve with these particular cells.

The Dexter/ModRobotics battery pack contains better quality cells with a higher capacity, so I would need to cycle it a few times to get it to settle, then measure the curve at Carl’s “typical” discharge rate to identify the knee voltage and the slope after the knee.

Selecting a “time to get on the dock” is a trade-off between wanting a good long playtime but saving enough reserve for two failed docking attempts in Carl’s case.

As a comparison, I also tested a 3S1P “battery pack” which had a slightly better discharge profile:

What did I conclude from this study?

  • Quality 3SP1 Li-ion could provide up to 30% longer playtimes

  • 3SP1 Li-ion is heavier than 8 NiMH - which may affect turning accuracy (unknown)

  • I would need to build a new (simpler) ruleset for juicer - my charge management program

  • I do not have any cycle life data to compare to Carl’s Eneloop NiMH 750 cycles

  • 3SP1 Li-ion with onboard BMS does not fit inside Carl’s current body

  • I feel safer with NiMH chemistry,

  • Took study cells and battery to recycler to get them out of the house

  • Carl hasn’t complained that he wants a longer playtime.

  • And now, the new ModRobotics pack seems to offer benefits but does not fit inside Carl.
    (The “inside Carl” position improves turning accuracy and repeatability greatly. Rear deck mounting is totally a non-option.)

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Easy:
Create a run-time constant for which batteries are being used, kind of like the “ifdef” in C.

Ahh, well. . . .
Those are just a tiny bit harder to overcome. :thinking:

I guess you’re just “stuck” (:wink:) with the NiMH batteries.

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