Morning and thanks for reading,
We have been working on the concept of powering our products from batteries for some time. We produce a breadth of products ranging from integration of embedded computer hardware (ie Single board computers running Windows) to what we actually design - data acquisition products.
We are quite unified in that everything we run is (as a minimum, and for the purposes of battery operation) designed to take a 12 VDC input (although some select areas are better than this). On this particular system we're using for development we have a single board computer using about 2 A at 12 V, an acquisition card at about 1 A max and a screen, again at around 1 A/ 12 V.
Space is of importance. We don't really have the space to put lots and lots of cells in to make vast voltages. Our first attempt thus ended up as an odd system. We had two LiPo cells in 2s1p with a nominal voltage of 7.4 V overall. In the original design we had an LT charger (heresy I realise) and a TI bq20z95 gas gauge device. An again LT ideal diode device was in place which was essentially a low loss diode OR for flipping between adaptor and battery power. Between the battery/bq20z95 and OR diode is a boost converter supplying just under 12V (to ensure the diode OR works correctly with the external PSU winning).
Something we seem to have observed is that the boost converter is not supplying any load whatsoever when an AC adaptor is present. It did not reliably sustain output power when the PSU was pulled and seemed completely incapable of starting the system.
It dawns on me that this was doomed to fail but we tried it at least. I anticipate that a 4 cell system with a minimum voltage of 12V (3.0 V per cell at discharged), a boost converter to give me about 17V @ 2A to charge the cells (using a 12V PSU as my source) and a straightforward diode OR from the adaptor or cells into a 12V buck converter might be better.
If anyone has any comments on a system topology or can direct me to any application notes with some examples I'd be really thankful. I've looked but failed strangely. Also I'm quite interested in trying a TI battery charger device as I've grown really fond of the bq20z95 and its features. I think the chargers may be worthy of note. That's why I picked this forum to post!
Thanks in advance for any comments.