A few points:
1) Battery technology has improved a lot over the 8 years we have been in operation. That stated, we have mowers with batteries manufactured in 2016 that are still operating without any issues. Batteries in electric mowers are comparable to what you will find in advanced electric vehicles.
2) Batteries are a collection of cells - so, it’s best to think of them as a collection of
individual batteries, rather than just one unit. As a result, the chances of a whole
battery failing is almost zero. We actually had a battery become totally emerged in the Auckland floods and managed to recover it. Battery cells are replaceable, so even if a failure did occur, you would not face having to replace a whole battery, unless it was at the end of its useful life.
3) Modern mower batteries have advanced battery management systems (BMS) that constantly monitor battery cells and keep them in balance. If cells do get out of
balance, this can reduce run times, but this is remedied by balancing the cell bank -
basically, voltage from the higher charged cells is directed to the lower charged cells bringing them into balance.
4) The life of batteries is measured in cycles. One cycle is equivalent to the charging
cycle from flat to fully charged. Commercial mower batteries have a 1200 cycle rating. If a mower operates for 7 hours per day, then we multiply the 7 hours times the 1200 cycles which offers 8,400 hours of battery life. This offers comfort to commercial operators as the mower will be replaced well before any battery issues appear. For residential clients that only mow 100~200 hours per year, the cycle life calculation is less important than the time that batteries take to gradually degrade over time. With proper storage and use, batteries can have a useful life of 10~12 years.
5) So, we hope the above information makes the “How much to replace a battery?”
question redundant. If you did want to replace a battery in the future the technology is likely to be different, and we have the capability of also building batteries to suit your situation - i.e., you may prefer to have a high quality mower, but do not need to have many hours of mowing capacity. We can adjust the kilowatts of storage to your needs, which can make things more economical as well.
6) Batteries can be used as an emergency power source - we often hook one up via an inverter when the power fails in a storm.
7) Swappable batteries - batteries where you may purchase one or two and insert them to create a larger pack are not as reliable as one large stationery battery. Swappable batteries require more connections and without constant maintenance these can cause issues over time.
8) There are different battery chemistries - Lithium Nickel Cobalt Manganese Oxide
(NMC) and Lithium Iron Phosphate (LP) two of the most common. Both have
advantages/disadvantages, but other new chemistries such as Sodium Ion that don’t use rare metals are also coming on line.
9) Difference in voltage doesn’t really matter. Some manufacturers use 48v systems,
others 76v. What is important is power. Power (Watts) = current (amps) x voltage
(volts)
10) Chargers are set to turn off at a certain voltage. If the charger does not shut down, the battery management system will not accept power over a certain voltage so in most cases it is safe to leave mowers on charge over the weekend.
11) Batteries are recyclable and as they approach end of life we will be able to help with recycling options.