battery
similar to galvanic cells
# Today’s batteries
- lithium batteries
- lead-acid batteries
- nickel-metal hydride ($\ce{ NiMH }$)
- alkaline (lúgos)
# Ideal battery
convers chemical energy into electric with 100% efficiency
→ constant voltage
# real battery
has losses
internal resistance due to resistance of metal parts and also the speed of electrolytic process