High voltage vs Low voltage batteries

First Energy Solar Solutions

High voltage vs Low voltage batteries

Did you know cheaper inverters make you spend more on electricity each month? Why? Certain inverters use low voltage (12, 24, or 48v) batteries and others use high voltage batteries (100v +). Low-voltage batteries are 60% efficient, whereas high-voltage batteries are 97% efficient.

This means when you own a low-voltage battery you have to spend 40% more electricity to charge your battery.

Standalone low-voltage battery systems require thicker cables and a separate safety fuse to disconnect the DC power between the battery system and the inverter in case of emergency. These fuses are installed on a large wall-mounted DC fuse holder which comes with a large handle to break the DC circuit. When this action is done one can often see DC volt arching, if the process is not done quickly enough.

Some newer low-voltage systems offer an all-in-one solution, where the inverter, battery fuses, PV circuit breakers, cabling, and batteries are all housed in one floor-standing, wall-secured, fashioned enclosure. This solution is much neater than the older generation systems but, remember this is a low voltage system.

In South Africa, we have found that a 10kW high voltage inverter with 12kWh in battery backup covers most single-phase homes, with little to no compromise in lifestyle during load shedding.

View this video where we try to trip the inverter running off a battery by running lots of kitchen appliances all at once:

We recommend running a minimum of 10kW per phase.

This means if you have a 3-phase home (without a 3-phase appliance; such as a 3phase aircon or 3-phase water pump) you should opt for 3 x 10kW single-phase inverters or if you do have a 3-phase appliance then opt for 2 or 3 12kW 3 phase inverters.

Did you know a 3-phase 12 kW inverter only gives you 4 kW per phase? The good news is you can add more of the same inverter to cater to bigger loads.

The advantage of the 10kW single-phase inverter is it uses high-voltage batteries.

When opting for a low-running-cost system, the upfront cost will be higher.

Did you know that some inverters use heat sync technology to cool themselves down, whereas others use fans to cool themselves down? These fans are typically noisier too.

Battery Life Cycles

When choosing a battery study the battery’s life cycle, which can be found in the manufacturer’s warranty, normally on the last page and in small print.

A new battery should offer 6000 cycles at 90% depth of discharge. If it says any less then you are buying a 2nd hand battery. Some popular (cheaper brands) don’t allow you to discharge your “new” battery past 60% of its capacity.

Divide the price of the battery against the usable portion (40% in the above example). Then compare it against the more expensive battery that offers 6000 cycles and 90% DOD (depth of discharge), and you’ll see that the more expensive battery is actually cheaper per usable kWh.

First Energy Solar Solutions’ mandate is to offer solutions that give you the best performance at the lowest price, without any hidden agenda to make a quick sale.