Alternate Power System for GoPiGo using Li-Ion Battery Pack


#1

I have designed a potential alternate system for powering the GoPiGo using a Li-Ion Battery pack. The pack uses 3x3.7V 18650 rechargeable Li-Ion cells (3S1P) to create a nominal 11.1V battery pack. Each cell has an individual protection PCB for over-current, over charge and discharge protection. The bill of materials for the alternate power system is as follows:

• QTY:3 - TrustFire PCB Protected 18650 3.7V 3000mAh Rechargeable Battery (1pairs), $16.99x3 = $51 CAD, http://www.amazon.ca/gp/product/B00KTTFFCU?psc=1&redirect=true&ref_=ox_sc_act_title_11&smid=A6Y9N4PV5Y6GJ
• QTY:1 - 3pcs Spring Loaded Black Plastic 3 x 3.7V 18650 Batteries Holder Case, $7.50 CAD, http://www.amazon.ca/gp/product/B00O9W691E?psc=1&redirect=true&ref_=ox_sc_act_title_1&smid=A2D9L39QUE9EAD
• QTY:1 - TrustFire Multifunctional TR003 Charger Cylindrical Li-ion Battery Fast Charge For 18650, $26.97 CAD, http://www.amazon.ca/gp/product/B00IMXOSTG?psc=1&redirect=true&ref_=ox_sc_act_title_10&smid=A17VWINQQL02TU
Total cost ~$86 CAD

The system includes two sets of 3 batteries (6 total), so that a new set can easily be swapped in after the old system runs out of juice. For wiring I was just planning on cutting the provided power cable that came with the GoPiGo and splicing it to the power leads on the 3x3.7 18650 battery case.

Here is the wiring diagram that I have created:

Note1: The wiring that was on the 18650 battery cases I purchased was only 26 AWG and likely should be upgraded to 22 AWG or lower to handle the current draw of the GoPiGo.

Note2: If you live in the USA a better option may be to get a multi-cell battery pack with a single PCB protection circuit (i.e. http://www.amazon.com/AT-Tenergy-2600mAh-Protected-Rechargeable/dp/B00U0P3CNM/ref=sr_1_1?ie=UTF8&qid=1456295453&sr=8-1&keywords=Tenergy+Li-Ion+11.1V+2600mAh+Rechargeable+Battery+Pack) & compatible charger (http://www.amazon.com/TLP-2000-Tenergy-Universal-Charger-3-7V-14-8V/dp/B001BEXDRQ/ref=pd_sim_sbs_23_1?ie=UTF8&dpID=31Ni-yXswGL&dpSrc=sims&preST=AC_UL160_SR160%2C160&refRID=1033GAHKDP0924J4E3RK). This was not a good option in Canada because multi-cell Li-Ion batteries are very expensive to import whereas single cell Li-Ion typically have free shipping and no extra customs charges.

I have read the guidelines for power options on this website (http://www.dexterindustries.com/GoPiGo/getting-started-with-your-gopigo-raspberry-pi-robot-kit-2/3-power-up-2/) and understand this system falls under “3. Using a custom power supply” and that the requirements are for a voltage between 9V and 12V with a rating of 2A or above. I know that the GoPiGo does not have reverse polarity protection and that I will triple check the polarity of the battery pack before plugging it in.

My question is whether the voltage regulator and related components on the GoPiGo can temporarily handle an input voltage of up to 12.6V while the battery pack is fully charged? Each cell is 4.2V when fully charged, so 4.2V x 3 cells = 12.6V. According to this website at a discharge current of ~1A the pack will only be above 12V for about 5 minutes (http://lygte-info.dk/review/batteries2012/TrustFire%20TF18650%203000mAh%20(Flame)%20UK.html).


Lithium polymer Batteries for Brick Pi
#2

HI slashrc,
Thanks for the detailed post about the alternate power supplies. All the options really look great.

There is no problem with the batteries being at 12.6V. The GoPiGo voltage() function would report a 12.5V till the voltage comes down and would start reporting it correctly below 12.5V. Just make sure that the batteries can supply 1A continuously and 2A peak.

Do let us know how they work for you. It would also be interesting to know how long does the GoPiGo run on these batteries.

-Karan


#3

Can the GoPiGo2 be powered separately? like one separate power pack for the Raspberry Pi and another battery pack just for the GoPiGo.


#4

It can be done but we haven’t tried it. You can try to power the Raspberry Pi with a 5V battery connected to the microUSB port and use a 9-12V battery connected to the GoPiGo to power the battery. The reason we haven;t tried it is that the Raspberry Pi also takes a lot of power and in the end you’ll end up having two big batteries on the GoPiGo.

-karan


#5

How about Pi power on the Micro-USB (with the charger) and simultaneous battery power for the GoPiGo? This makes development easier so you don’t have to go through a full reboot when changing from Pi power to Go power.
If the GoPiGo is not being driven (no motor activity) the batteries will not really run down, right?
Can the two power sources be going in at the same time?


#6

Hi @salvideoguy,

Yes, you can power up the Pi using the USB- Micro cable and the GoPiGo using a battery or a power supply capable of supplying 9-12V at 2A, simultaneously. Yes you can have both the power sources on at the same time and the batteries don’t drain out when the motors aren’t running.

You can look at this page) to learn more about powering the GoPiGo and your various options.

Do let us know if this helps,


#7

Ok, I know what my problem was. The external 12v p/s was rated at 1 amp. You recommend 2.0 Amps or better. I will get one of those today. I think it best where the longest cycles are development so that the GoPiGo sits upside down over a shoebox so you can test code without chasing it around the floor and running the batteries down.

Cheers


#8

Something is seriously wrong with the forums.
It no longer recognizes my email address (login name) and when I try to change p/w it says ‘invalid username or email’.

Can you please check?

Obviously I have an account and have been posting in the forums so why is my user unrecognized?

Thanks,

Steve Levine

(Former Community PM for Autodesk Community a 25 million member Lithium site)


#9

@salvideoguy: Just sent you a PM. Can you have a look at it and sorry for the troubles with the forums


#10

Hi,
Salvideoguy could you post a link of the battery you found working when you have it? We have several robots for students and we’d rather buy one rechargeable battery per robot than a whole pile of 1.5V batteries.

To Karan and Shoban: when looking at battery specification on the internet, they usually indicate voltage (fine) and the mAh but no information about peak intensity. Is there a way I could guess the later from the mAh?
(like: considering industry standards, a battery with 3000mAh, can for sure/most often supply 2A in peaks)

Thanks


#11

Hi @vberry,
Batteries have a C rating and their instantaneous current is equal to Capacity(mAh)*( C rating), ie: for a battery of capacity 1300mAh and a C rating of 2 will give an instantaneous current of 2.6A. You must be careful in choosing batteries as over discharging may cause fire with certain batteries.

You should have a look at this before choosing your battery.

To know more about the options for batteries you can refer to the post of slashc , which is the first post of this page.

-Please do let us know if this helps,
Shoban


#12

hi @karan

one question, the docs have this warning: “Make sure the power wall adapter is never connected when you are running the motors or sensors.” here’s the link: gopigo step1

Just confused, because this forum seems to suggest that it’s ok to have the pi in the adapter and have the motors running (just running how to test code with out using the battery).

Also would a power supply like this one work to power the gopigo(and rpi), simultaneously?

so that i can test sensors and software without using the battery pack.

thanks,
malik woods


#13

Hi @mkowoods,

Yes it is fine to have the Pi powered with the Micro USB Power adapter and the GoPiGo powered by the battery pack. However what we meant was, you should not run the motors with a 5V power adapter alone which is just powering from the microUSB. When you have the Motors running you should have the battery powering the GoPiGo.

The power supply that you have posted should work to power the GoPiGo. You can have the GoPiGo and the Pi powered simultaneously.

Please let us know if this helps,
-Shoban