Battery Life Information w High Performance Flexible Solar Panels

Portable electronic equipment consumes power as Amps (Amperes) at various rates depending upon the type of equipment and what types of functions are being used. 

In general heaters, pumps & motors (physical motion), and bright lights consume much more power than small electronics, non-motorized equipment and dim lights. 

It is important to remember: 

Batteries store power, for use on demand ...in a short time.
Recharge is slow, low amp, trickle charge ...over a long time.

The more Amps consumed, the faster a battery charge is depleted.  Batteries are also limited by their inherent chemistry as to how fast they can deliver electron flow; AmpHr capacity is based upon battery slow drain over ten to twenty hours.  Due to the electro chemical properties of batteries, there is a practical limit of about 2.5 Amps maximum for equipment to be powered by any battery system.

To determine how long a piece of equipment may run in hours using a fully charged battery, one simply divides:

Theoretically, an 18 AmpHr battery could run a 1.8 Amp device for 10 hours ...at 100% efficiency. 

However, batteries and inverters are not that efficient.  Due to chemical and physical limitations of batteries and inverters,  we recommend use of 60% efficiency for practical expectations.  So, to estimate practical operating life:

If you only know the wattage of a device you may calculate Amps for estimation purposes using: 

	BullDog™ PowerPak™ Portable Power  Systems
Solar/DC/AC Rechargeable 110v Portable Power Systems

Note:  power conversion and battery life are subject to a wide number of variables.  These include chemical potential charges, environment temperature, circuit thermal resistance, as well as load factors of equipment connected to the system.  Also, because of loss through the inverter, Amps (AC) are less than Amps (DC) actually consumed.  Each of these variables are impossible to estimate for general purposes.  Therefore any estimation is inherently imprecise.  Assuming 60% efficiency should yield a practical expectation.

Battery Life calculations are further complicated by simultaneous recharge using solar panels, or 12vDC connections.  In this case recharge Amps IN are roughly equivalent to utilized Amps OUT. 

For Example:

• If your equipment consumes 1.8 Amps, but a solar panel is simultaneously resupplying the battery with 1.2 Amps, then the net consumption is only .6 Amps.  At that very low consumption per hour, an 18 AmpHr battery would theoretically last 30 hours.  In this example you could run your gadget all day without problem. 

(note: very few places on earth have 30 hours of uninterrupted sunlight at any given time of year)
 
• Alternately, if your equipment consumes 7 Amps (too much), solar panel provides 1.2 Amps, net 5.8 Amp consumption.  18 AmpHr battery would last only 3.1 hours at 100% efficiency (more realistically, 2 hours), even with the solar panel.  In this example to increase battery life, you need to reduce Amp consumption (turn off equipment, reduce brightness, etc.) and/or use additional solar panels to increase recharge 1.2 Amps per additional panel.

 
• Doing so, equipment reduced to 6 Amps, using (3) solar panels providing 1.2 Amps each (for 3.6 Amps INput), net 2.4 Amp consumption.  18 AmpHr battery could now last 7.5 hours at 100% efficiency in continuous use (at 60% efficiency, 4.5 hours). 

The time to fully recharge the battery depends upon the AmpHr size of the system battery, how low the battery was discharged, and input Amperage.

See Recharge Chart at below right.