Li-ion batteries

Flying.
No restrictions below 100Wh.
Possibly a max of 2 per person.
Have to be in hand luggage, unless installed in the appliance in the hold.
Compulsory above 100Wh, but recommended to tape up the terminals and put in poly bag.

1 cell
3.7V nom. 4.2 charged, 3V cut-off, but 2.7V OK 
2 cell
7.4V nom. 8.4 charged, 6V cut-off, but 5.4V OK 
3 cell
11.1V nom. 12.6 charged, 9V cut-off, but 8.1V OK 

ok to constant current charge at marked capacity for 1 hour, but lower better. Cut off when current drops.

Capacities at Feb 2017

Bosch 11.1 3 cell 1.3Ah ~2008. ~1Ah.
Dell laptop 6 cell 11.3V 4700 orig. >2Ah left Charger 90W, 1 hour, so ~5A
New 'elfeland' 3.6Ah. mass too low, sound hollow. ~1Ah.

Examples. boot heater, 33 ohm each (normally 17R)
2 cell, 7.6 cut off (1.76W)
I = V/R = 7.6/33 = 0.23A each
hours run = Ah/A 
For 1.3Ah, hours = 1.3/ (.23 x 2) = 2.8h
3.8Ah = 3.8/.46 = 8.3h
2Ah = 2/.46 = ~4h, but in practice get >6 hours on pwm as the higher start voltage means a lower current draw, and in general full power not required (3/4 power ok in cold weather)

Japan 2017
Dell 12V/2Ah 17R each heater
PWM used to reduce demand. Had to re-scale software to give full power as a percentage of max - 25% - but check.
the 3/4 setting of this new max was enough

PV array low IR

PV cable went low IR. Inverter warns below 1M. Got down to 600k without shutdown.
After about 6 years in the ground a joint got water in it. 
Replaced it with one length. Just under 16m, allowing 1m at the panels.