In this article, we will discuss so of the losses when power is converted or transformed or used. Our niche is the conversion of energy and with that there are losses. For example, a light bulb was designed to provide light. It does this by making a small filament of wire glow. The glowing generates the light that's wanted but also heat and that is a wasteful by-product of a light bulb.
With battery charging which is a chemical reaction, there are losses through the chemical conversions of electrons moving between plates and acids. These losses are minimalised with improvements in the technology with over 100 years in development. Losses in charging lead-acid vary from 12% for AGM batteries to about 20-25% for wet cell batteries. That means a 100Ah battery requires 112-125 Amps to recharge and store 100Ah of usable energy.
When you convert DC power from a battery into AC mains power using an inverter the equipment inside the inverter uses power and that accounts for a 5% loss in available power. The same happen when converting AC power into DC power, these devices are called power supplies, or chargers, or power rectifiers. Switch-mode supplies are typically used in all modern-day equipment to help reduce these inefficiencies but they need to be calculated and allowed for.
An example of this might be an off-grid solar system with a small inverter for charging a cellphone.
Solar panels generate DC power 18-20% efficient, that's run through a solar controller 95% into a battery for storage 85% efficient. The mains power inverter converts DC power into AC mains 95% and you connect your phone charger in here. The charger is only 90-95% efficient which then connects to your phone's Lithium battery. Let's just say here it's 99% efficient at charging. All in all, you have four pieces of equipment all with up to 10% losses so your generation of the panels needs to be almost twice the power you want to consume.
When using mains power or grid-tie to power your home but have batteries for backup energy there are losses. You also lose more power in converting them back from DC stored energy in the battery back into usable mains power. This highlights an issue with grid-tie and battery backup. Multiple conversions, the storage, use and generation all have efficiencies and losses.
In future articles, we'll discuss DC versions much like our DC to DC chargers. Direct DC Coupling in a renewable energy system and more.