Charger or charging circuit for use with MoPi-2?

Support
1

Greetings All!
I have a Pi application where there is an interruptible but generally reliable 12-15V DC supply. The plan is to put the 12-15V supply on input 1 of the MoPi-2 with a pack of 8 rechargeable NiMH AA batteries on input 2. The DC supply would also power input to the charger point (X1). The MoPi-2 will automatically cut over to input 2 if input 1 drops out and will shut down gracefully if the battery pack discharges.

Could anyone point me at suitable circuit for the charger or, alternatively, at a piece of kit that will do the job? If it made life easier, I could get a LiPo battery but I already have the AA battery holder and batteries so that seems like a sensible starting point. Circuit design is beyond me but soldering is OK 8-}

Thanks!

2

I would probably suggest the swap to LiPo to be a good move, as there are a lot more modules out there that handle charging them than there are for NimH.

Something like the Adafruit Powerboost1000 (https://shop.pimoroni.com/products/powerboost-1000-charger-rechargeable-5v-lipo-usb-boost-1a-1000c) could do quite well at what you’ve described, I think.

3

Thanks for this suggestion.
I’m not clear how this would work with a MoPi-2 which expects a minimum of 6V5 input and which will work with LiPo in pairs to deliver 7V2. From what I read, the Powerboost does not provide a seamless UPS, which is essential for my application and which the MoPi appears to do.
Have I misunderstood?

4

I was envisioning you using the MoPi2 as the UPS element, with your 12-15VDC on input one, and the powerboost/lipo combo on input 2.

As I said in my original reply, I’m not aware of a NiMH charging module that meets the criteria, without finding something from an RC site or similar.

5

OK, I undertand now. Thank you.

As the kit will be in a wooden structure that may be occupied by people of limited mobility, I am pushing the LiPo option down the stack because of the fire risk associated with LiPos.

The current option looks like a Minwa MW3168 charger driving a 6 or 8 cell NiMH pack. I may even have a redeployable set of NiCd that could be used.

Thanks for your help.