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Backup Battery

Gerhard Kreuzer
Expert 2600 points
Other Parts Discussed in Thread: TPS2115A

Hi,

I am new to battery management and so I have some naive questions:

I have a core System running at 3V3 and a cellphone module, which needs 3V3 and 3V7 for the cell phone transmitter part. Normally the System is powered by two car batteries in series (20V-30V) doing automatically measurements in the field. If the main supply Drops (no sun or fuel cell dry out and batteries pretty empty) the core should try to live for a while to send Status/ error messages and waiting for new energy. During this phase no measurement were taken.

==> I Need a battery management chip, taking 5V at the Input (USB Client to have a Interface for Service personal) and delivering 3V7 for the cell phone Transmitter and I will make 3V3 out of 3V7 using a linear LDO. A SMPS makes 5V out of 20V-30V as Long as this power source is available. If Service takes place, the Service guy can take the core and power it by USB from his Laptop or tablet using USB-OTG of his tablet. I dont Need USB-OTG at the measurement System.

Is the bq2426x such a chip? Or is there another chip recommended? My core can deal with UART, SPI, I²C, no Problem there where also GPIOs leftt if needed. The current dramw by my core isn't that high, all in all less than 1A. The cell phone/GPS/GLONASS module type isn't fixed at that time, so I can't give a certain value, sorry.

THANKS FOR HELPING A NEWBIE.

With best regards


Gerhard

  • 0
    TI__Genius 13700 points

    Hello Gerhard,

    Let me try and understand you application.

    You have a stack of two car batteries that provide 20-30V. This voltage is stepped down to 5V by an SMPS. The 5V rail is then used to generate a 3.7V & 3.3V. Will the final 3.7V / 3.3V have a battery connected or in parallel that you will charging?

    Right now from how you are explaining your system topology it sounds like an input selector switch that will take 5V from the SMPS or a USB that is then bucked down to 3.7V and 3.3V would fit the application.

    Something like a power multiplexer such as the TPS2115A which can can transition between two different power inputs.

    Let me know what I might be missing so we can help you reach a quick solution.

  • 0 in reply to Ryan May
    Expert 2600 points

    Hi Ryan,

    yes, to batteries stacked, other part of the System Needs 24V ...

    The core, a controller and a cell phone/GPS module (SIM968) running control Tasks and allow remote access. Sometimes the battery stack dries out and the system is offline, with the current Version of prototype HW. Now we want to go one step foreward and include a backup battery to power to core.

    On the other Hand, Service personal can power the system core from USB no Need to carry heavy batteries around.

    There were power mux for 5V, thats not the Problem, but which battery mamagement chip will fit best?

    Currently I read all about bq24261, but I just picked this randomly ..

    Power requirements:

    Controller 3V3 150mA, GPS 3V2 to 4V8 Peaks up to 2A for 577us.

    With best regards

    Gerhard

  • 0 in reply to Gerhard Kreuzer
    TI__Genius 13700 points

    Hello Gerhard,

    So I apologize but I am still a little confused.

    Are you wanting to charge the 24V battery stack from the USB or are you adding a single cell Li-ion battery to serve as a secondary battery back-up for these cell/GPS/processor loads.

    If the plan is to add such a Li-ion battery the BQ24261 should work fine. It works well off of a USB input for power. To accomplish the voltage rails you are going to need a boost supply to bring the Li-ion voltage up to the 4V8 and then you can regulate the 3V3 & 3V2 from this rail

  • 0 in reply to Ryan May
    Expert 2600 points

    Hi Ryan,

    the 24V battery stack is charged by solar power or a fuel cell. The LiIon is for backup so the System is online after the 24V stack dries out. We have such a Situation last winter, fuel cell Fails and too less sun. The System wasnt reachable by Service personal cause too much snow.

    So we want to have a backup cell so we know more about the Status.

    You think I Need a stepup? My processor runs between 3.0 and 3.6V, the GSM/GPS module runs from 3.0V to 3.6V, and the GSM Transmitter Needs between 3.2 und 4.2V, cause it is made for powerd by a single LiIon cell like a cell phone.

    But the bq24261 should fit basicly, so I will order a eval board today.

    Thanks a lot.

    With best regards

    Gerhard

  • 0 in reply to Gerhard Kreuzer
    TI__Genius 13700 points

    Hello Gerhard,

    Thank you for your patience in helping me to understand your application.

    If you loading devices have the operating ranges above a step up converter will not be needed but it would be wise to look into a buck converter to to step the voltage down unless you intend on only charging the Li-ion battery up to 3.6V.

  • 0 in reply to Ryan May
    Prodigy 20 points

    0550.POWER.pdf

    HI,

    We are using BQ24261 for our battery charge. But  battery is not charging. We have not programmed the IC. I am attaching power section Schematic. kindly provide me solution. if we have to program the ic, send us any sample code so that we can use. 

  • 0 in reply to chaitu jasti
    Expert 2600 points

    Hi,

    the IC is in 'Charge disabled' mode and you have to use I²C Interface and the Manual to set this bit (and probably others to set Charge current and ...).

    With best regards

    Gerhard