After many incidents, a new technology has emerged, which uses gelled electrolyte instead of liquid electrolyte: therefore there is no need of a rigid metal casing around the battery to hold the liquid, the gel is still, and a much lighter plastic coating can be used. Moreover, the gel is much less volatile and flammable than the liquid electrolyte, so in case of damage the battery is less dangerous.
Now, lithium is used as lithium ions enclosed in another material such as polymer: the above mentioned problems are partially avoided at the expense of the Wh/kg energy density.
Used properly, a Lithium-polymer battery is no more dangerous than any other rechargeable battery. However the LiPo batteries require different charging schemes compared to Ni-CD or Ni-MH, and there may be a significant risk of fire in case of non compliance with instructions.
If the LiPo battery suffers a short circuit or excessive discharge, the internal components can be damaged and cause significant overheating, and catch fire. As lithium is highly reactive to contact with water, it can produce toxic gas emission and fire.
Therefore, our beautiful actresses, wired with an RF transmitter, must avoid dropping it into the toilet, as it happens between sequence shooting. They might then have “fanny on fire!” according to cinematic expression,
LiPo batteries should never be exposed to direct sunlight, or left in a location where temperatures may exceed 60 °C (car in direct sunlight). The LiPo should not be stored or discharged with a voltage below 3 V per cell (i.e. 6 V for a 9V battery) for fear of damaging it permanently.
That’s the reason why iPowerUS 9V batteries have electronic protection, which prevents internal voltage dropping under 6.5 V. These iPowerUS LiPo batteries (purple model, named "Professional") have a capacity of 520 mAh, with 8.4V~6.5V working voltage, with 80% capacity loss after 500 cycles (according to manufacturer).
Tests made on a LiPo battery with less than 200 charge cycles, using an Audio Ltd. TX-2020 transmitter, with 73-74 mA consumption, show a quasi-linear 8.3 V - 6.6 V discharge in six hours and a half. This is to be compared with the logarithmic 8.95 V - 6.2 V discharge of a Varta High Energy battery, in four hours and fifteen minutes. See, about this (in French), the additional '09 “9 Volt 6LR61 Batteries” review on perchman.com site
The LiPo batteries must only be recharged with chargers specified for this application, using the load profile of the industry standard CC/CV (Constant Current/Constant Voltage). The load current shall not exceed in any way 1C (one nominal capacity): for example for a 500 mAH battery, load current must be less than 0.5 A.
The iPowerUS “9V Battery Fast Smart Charger” charger respects this principle, but make sure to setup charger switch on the “Li” position, and not the “Ni-CD or Ni-MH” one, which would damage or shorten the battery's life. Charging time of a Professional 520 mAh LiPo battery is one hour. This charger is 110-240 V powered, and comes with an US/FR DC adapter and a DC-12V car cigar-lighter power cord. Batteries come in a very handy 4-unit container, which insulates battery contacts and prevents short circuits (position upside down, opposite to the picture).
Of course, with this new technology, we have much to learn and also we have to follow the recommendations of a leading Lithium-polymer battery manufacturer
« The use of lithium-polymer batteries requires a careful user in full possession of his mental and physical faculties. Persons, who may handle cells thoughtlessly or inappropriately, must be kept away under all circumstances. »
We can therefore conclude that in our profession, the use of our old alkaline batteries is not quite over.
The iPowerUS Professional LiPo 520 mAh batteries are sold at DC Audiovisuel; sale price is 17 euros ex VAT per unit, and dedicated charger 40 euros ex VAT.
Given that using a Lithium-polymer battery, with high fire risk, can cause serious damage to property and persons, user agrees to accept risk and responsibility. As neither manufacturer nor DC Audiovisuel can control proper use of the battery (charge, discharge, shock, exposure to heat, storage, etc..), they cannot be held responsible for damage to persons and property.