mobile battery for pi and monitor help

looks like recovered Laptop batteries, I have maybe a hundred or more from that process, most of them are still good so it is a great source of cheap power

Must be careful of charging and discharging though, if you are going to parallel them either use brand new from the same batch or keep the sets parallel as they come out of the laptop pack, your asking for problems of self discharge, leakage or worse, fire if not, also packs in series need to be monitored for equalization during charging (Unless your charging them all individually), also if your saying your putting 3 in parallel and there from laptop pack where there typically in pairs, it can be bad for the same reasons.

Also try to limit them from full cycle swings as it will age them very quickly

Either way, be very carful

Thanks for the very good advice.

One more I can add ... always monitor closely the charging, do not leave unattended ...

The dangers or parallelling Lithium batteries is severely overestimated. Sure, you won't hurt anything if you're careful, but things tend to go well even without "super" care.

For example, any single cell is already a parallel connection between  two cells: the left half and the right half. So parallel connections are not an unusual sight.

Do take care that at the moment you connect them together, they have the same voltage. This is most easily achieved by fully charging the to-be-paralleled batteries to full charge before connecting them. From then on, there is no problem if they differ a bit. Suppose one is 2200mAh and the other is 2000mAh, they will simply share the load  and charge currents in that ratio. If the chemistries differ (and I don't recommend you go as far as THAT) then one might be taking the full load say between 3.85V and 3.75V while the other takes most of the load while discharging  between 3.75 and 3.65V. In that case you have to make sure that the discharge current stays below the rating for EACH cell separately instead of being allowed to discharge at the sum of the ratings of the batteries.

I recently disassembled two battery packs. One was 4x2 and the other was 3x3. So for my bike-light I'm using a "1x3" pack now. So the "three-in-parallel" can already be found in laptop packs "as is".

The dangers or parallelling Lithium batteries is severely overestimated. Sure, you won't hurt anything if you're careful, but things tend to go well even without "super" care.

For example, any single cell is already a parallel connection between  two cells: the left half and the right half. So parallel connections are not an unusual sight.

Do take care that at the moment you connect them together, they have the same voltage. This is most easily achieved by fully charging the to-be-paralleled batteries to full charge before connecting them. From then on, there is no problem if they differ a bit. Suppose one is 2200mAh and the other is 2000mAh, they will simply share the load  and charge currents in that ratio. If the chemistries differ (and I don't recommend you go as far as THAT) then one might be taking the full load say between 3.85V and 3.75V while the other takes most of the load while discharging  between 3.75 and 3.65V. In that case you have to make sure that the discharge current stays below the rating for EACH cell separately instead of being allowed to discharge at the sum of the ratings of the batteries.

I recently disassembled two battery packs. One was 4x2 and the other was 3x3. So for my bike-light I'm using a "1x3" pack now. So the "three-in-parallel" can already be found in laptop packs "as is".