Hello!
I have a Maduino Zero SIM808 GPS Tracker v3.5 board, which I’ve written a basic tracker sketch for. Now I want to move it from the lab bench to a vehicle installation, so I want to attach a LiPo battery as a back-up in case someone disconnects the main supply.
I bought the battery (https://www.robotshop.com/uk/lipo-battery-cell---37v-1200mah.html) and the SIM808 board from RobotShop, and assumed they would be compatible. However, the battery doesn’t charge (the charge light doesn’t come on and the battery voltage gradually drops instead of increasing).
I’ve looked at the schematic, and used it to check that the charger IC has the “correct” 4.2v regulated input, so it kinda feels like a hardware fault, however this is my first project using a LiPo battery so I want to understand if I’m missing something here.
Is there anything I should be checking? There doesn’t appear to be any software control of the charger. Is there such a thing as an incompatible LiPo battery?
Thanks.
Hello @stevehobbs and welcome to the RobotShop community,
According to the manufacturer’s Wiki the Maduino Zero SIM808 GPS Tracker v3.5 needs a 2A pulse current when power on. However, the batteries you linked have a standard charge current of 0.2C (“C” is the rated capacity of the battery in amp-hours) in this case that is 1200mAh=1.2Ah so 0.2*1.2=0.24A, the specifications also mention that the max charge current is 1C so the maximum charge rate is 1.2A, but as I mentioned earlier the Maduino Zero SIM808 needs 2A which is higher than what the battery can provide.
If you need help selecting a battery I suggest checking this guide:
I hope this information can help you
Let us know if you need further assistance
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@geraldinebc15, many thanks for your reply. I hadn’t spotted the separate PDF specification until you provided the direct link!
Maybe I am not understanding the specification, but it seems to say the standard (by which I assume they mean continuous, steady-state) discharge rate is 0.5C, hence 600mA. They also mention that the max discharge rate is 2C, hence 2400mA, which would appear to be in excess of what the SIM808 requires for its pulses current when the radio is active. I think this one would be suitable, as it claims 5C continuous discharge, am I right? https://www.robotshop.com/uk/37v-2000mah-5c-lipo-battery-eu.html
Besides the discharge discussion, I still don’t understand why the SIM808 module isn’t charging the battery; my external power supply can supply up to 5A, so there should have been plenty of capacity to charge the battery, whether or not the SIM808 was active.
Hello again!
Yes, you are correct! I read the max charge current instead of the max discharge current which seems to be “lower than or equal to 2C” (2.4A) while the Maduino Wiki mentions the board needs “2A or more” (I also read somewhere else it needs 2.5A) so this may or may not be the problem. Either way, the 3.7V, 2000mAh, 5C LiPo Battery should definitely work.
Now, if you connect an external power supply you should see the CHG (orange) LED light up, indicating that it is charging the battery if this doesn’t happen there might hardware fault.
Note: Don’t operate when in power supply on (That is, don’t plug or unplug the Antenna ,SIM Cars, SD Card, in case of short-circuit that may burn the IC down.)
Yup, no charge light when powered from the bench supply. I’ll have to see if I can figure out which bit is dead and get a replacement part…
Oh, sorry to hear that.
Did you purchase the board in RobotShop?
Yes, I did. It’s actually the 2nd board I got from you; the first was bought as a v3.5 but you sent a v3.4. You then replaced it with the v3.5, as I had specifically wanted the external power jack option.
We are sorry you had problems with the products
I will put you in touch with the RMA team to see if they can help you out
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This topic was transferred to internal RobotShop Support.
