6.4V Lithium iron phosphate battery

Hi!

The JST connector can only be used with Li-Ion or Li-Pol that has a maximum voltage of 4.2V and nominal voltage of 3.7 V. If you used it on VIN, then it is okay but it becomes the charging source in this case.

Do take note, when powering from VIN or VUSB, you won’t be getting the 18 uA of sleep current. Only when a valid Li-Ion/Pol is used on the JST connector, the desired 18 uA of sleep current can be achieved.

Hi,

Using VIN, it will be 1.5 mA nominally with VIN at 6V. You can take a look at this section of the datasheet of the power path IC BQ24074. So, that’s the best you could get unfortunately.

Usually VIN is considered as the 2nd source of power like solar and DC voltage.

As more and more people are requesting for LiFePO4 usage, I’m currently looking into possible version of using LiFePO4 and NiMH also. But, currently still in development.

Hi Brett,

Would be very interested in a LiFePO4 version but also if you are already looking into it LTO support (though there aren’t any chipsets I can find for it yet) would be even better. The cold performance and charge cycling ability of those batteries is super amazing.

I did look into LTO too. But, I’m looking at a chip currently that supports Li-Ion/Pol, NiMH and LiFePO4. Unfortunately, LTO support is on another separate chip. To support the 3 battery chemistry above, only some configuration components will be different, That would allow me to use a single design but different components are populated based on different battery chemistry. And yes, LiFePO4 and LTO battery charger are less in the market. And to make things worst, I needed a solar panel input compatible (MPPT) and ultra low current uA range. That makes things harder but I’m working on it.

The driving force behind this decision is definitely temperature as you have mentioned. The number of charge cycle is also way much better than Li-Ion/Pol batteries.

There’s no ETA just yet but samples chip are coming in. So, I’m evaluating….

Hi Lim,

I would also be very interested in a solution where one could use NiMH batteries or a LiFePO4 battery. Especially the latter. In the regions where we deploy we can’t afford to have issues (fire related) when it comes to batteries so the Lipo’s are a no go. I am also designing shields on top of the board on which I mount battery a holder so a VIN power pin that can use the low power (18mAh) would be a real “wannahave”. On top of that having a solar charge solution for the LiFePO4 batteries would be great.

Please let us know if you made any progress on this. This would be a great improvement on our system.

Cheers,

Roy

Thanks Lim for the update.

That is good news, I will keep track of the progress on your new boards. Please check with the RN2903 if you can make it work in the Malaysian/Indonesian frequency. Although it is advertised as being able to run in the 915mHz range, when I bought them (3 months ago) they came pre-programmed with the US settings and so they don’t work out of the box.

After asking Microchip how to change it, because I couldn’t figure out how to, there wasn’t much in the docs, they said I had to update the firmware and they advised me to write it myself because they had none for AS923. Needless to say I wasn’t happy about this, also because it took them over two weeks to respond to this question. Note that this is for LoraWAN, when using Lora only you can change the frequency.

Long story short, although they look easy to use with the TX/RX build in support. For us costs wise and limitations on software adjustments actually made us abandon our custom build boards around this chip. Hence I moved on and started ordering your boards with the RFM95 chip 🙂

Cheers,

Roy

Hi Lim,
Do you think about changing the MCP1700 (Mini Ultra Pro V3 board) on Buck-Boost regulator e.g TPS63051.
I believe it will be more efficient for using a LiPo. These batteries have a voltage that goes from 4.2V to 2.7V typically during their discharge cycle.

And, if I understand, Mini Ultra Pro V3 board would not work if the voltage goes lower than 3.3 v (e.g. 3V).

best regards,
Dmytro