Hi there.
I have 2 chargers. the E1 (5200mAh) and the big E7 (26,800mAh)
I was wondering is it possible to charge the small E1 from the large E7?
Im away at a festival for five days and hate to carry the big one with me all the time. the small E1 is perfect for the pocket, so charging one from the other would be great.
What do you reckon?
Thanks
A 
Hi @kuztardd,
This should work fine, but there will be some energy loss during the charging process. Therefore, you won’t be able to charge the small power bank 5 times, it may be more like 4.
In theory (used loosely) I would say yes but seeming you already have both, why don’t you just try connecting the E7 output port to the input port on the E1 to see?
Festival for 5 days is a good example benefit of solar. Accepting you own both batteries and you dont own the solar yet. You could just in the festival if sat away from your tent in the sun just connect a small solar panel to your phone? That also may fail your criteria as the solar panel is about the same weight and larger than the 26800 you dont want to carry.
Yes you can charge one from the other. As @TechnicallyWell said you waste energy in charging batteries from batteries to just make it smaller in the pocket.
The only potential issue I see is the smaller battery will enter a trickle charge period in its last 10% til full where its intake current is so low the 26800 may shut off the port, so you may struggle to get the smaller batter much above 85%-90% charged. If that is the problem then keep pressing the 26800 power button to wake it up and do it a few times to shove the smaller battery closer to 100%.