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An electric riding mower is nothing without its batteries. The 2017 Cub Cadet RZT S Zero and the Ryobi RM480e electric riding mowers have four large batteries that require overnight charging after each use. By the way overnight charging is the most practical way to go about getting the correct charge to make your batteries last. Read on to find five other tips to keep your batteries running at their peak.
What type of batteries do electric riding mowers use?
Residential electric riding mowers use “deep-cycle” batteries and are designed to be discharged and recharged time after time. This is different than the starting battery in your car that is not designed for repeated deep discharging and recharging. Deep-cycle batteries for electric riding mowers use a gel instead of a liquid electrolyte internally, and are commonly referred to as “sealed” because they cannot spill, and they do not require the periodic adding of water.
Why don’t riding lawn mowers use Lithium-ion batteries? Almost all cordless hand tools nowadays use L-ion batteries. They are convenient and will last up to 1500 cycles if taken care of. Even autos like the Tesla and Prius use Lithium-ion batteries. So why doesn’t the Ryobi RM480E and Cub Cadet Zero use Lithium’s?
The primary reason at this time is current draw. When driving an electric auto you use a high current to accelerate from a stop and you use bursts of energy going up hills. The rest of the time it does not take a lot of power to keep the auto going down the highway at 65 mph so the batteries have a relatively low current draw. Lithium batteries can handle short bursts of high current but will overheat and burn/explode when subjected to heavy, long term current draw. Mowing the lawn is different than driving an auto because mowing requires a constant high current draw on the batteries for a long duration. In other words when you start to mow you usually keep the mower cutting grass for the whole time it takes to mow your lawn. Lithium batteries are not good for long duration, high current draw applications. Deep discharge, lead acid batteries are the best choice for this type of application.
The secondary reason is cost. A lithium battery pack with enough power (Watt-Hours) to operate the Cub Cadet Zero for an hour or the Ryobi RM480E for 2 hours would easily cost $2000 or more.
1. New batteries must always be fully charged
If you fail to fully charge them that first time. If you just go out and mow your lawn right away they will never be able to maximize their full charged range.
2. Only drain new batteries by 30 percent the first 10 uses
This fact is not listed in the operator’s manuals for either the Cub Cadet RZT S Zero or the Ryobi RM480e but to get the best life deep-cycle batteries must experience a “break-in” period to reach full capacity and ensure the longest life. To repeat, new batteries should be fully charged before the initial use. Then, during the first ten uses, I strongly suggest that you only use about 30% of the battery’s charge for the first 10 uses. Then promptly, fully recharge the battery overnight. Yes, you will have to mow your lawn in sections the first couple of times, but this process will maximize battery range and lifespan in the long-term.
3. Should I recharge my batteries, even if they’ve been barely used?
After every day’s use, without question, you should recharge your batteries – do not go multiple days before recharging. The charger that came with your electric riding mower is designed to charge up the battery, bring the battery to its peak charge and then maintain that charge. The charger and the batteries are designed to be left plugged in. Batteries love it when you do this, it’s like battery TLC-time whenever they get fully charged. In fact if you rarely drain them below 50 percent and charge them fully each night, you can nearly double the lifespan of your batteries. Never use your electric riding mower to mow your lawn and then let it sit without charging for a few days. This will greatly shorten the battery life.
4. Avoid depleting your battery over 80 percent.
If you can, avoid draining your batteries over 80 percent (20% charge left). Fully discharging them to 0% will destroy your batteries quickly. If you do this often your batteries may only last a year. If you do have to discharge them past 80% to mow your lawn I suggest mowing it over the course of two days instead. Let the batteries fully charge overnight between mows. If you don’t have enough capacity I suggest when this set of batteries fails look into a large capacity battery to replace them with.
While I’m on the subject is periodically recharging the batteries for a short time to finish the lawn helpful or harmful?
“Boost” charging ultimately harms deep-cycle batteries. The battery charger supplied with your electric riding mower functions in three charging stages* (charge, peak, and float) to optimize the capacity and maintain the batteries. Regularly plugging in the charger for short bursts throughout the day does not allow the charger or batteries to go through the proper charging stages and durations, ultimately destroying the batteries. It’s important to only fully recharge your battery after each day’s use, avoiding boost charging in-between full charges as much as possible.
Fun Fact: Warehouses that use electric forklifts will have more than one battery pack and actually switch out the entire battery assembly instead of “boost” charging. Remember, depending on your mower a new set of batteries will cost $600-$1000 so getting the longest life out of them is critical. See Is Owning a Ryobi RM480E Electric Riding Mower Cost Effective? at Todaysmower.com to learn more about battery costs.
*The Cub Cadet RZT-S Zero uses a 5 phase charger. It first checks the battery condition, then charges, peak charges. Once the charge is complete it automatically disconnects from your 110 v ac source and goes to sleep. Periodically it will wake up and check the state of the battery.
5. Can my batteries be overcharged? Hint – Always use your own charger
Never use a different electric riding mower charger other than the one that came with your electric riding mower. If your charger fails purchase the exact replacement. Never try to replace your charger with an “equivalent” charger off Amazon.
Remember, your electric riding mower uses an automatic battery charger that constantly monitors the recharging process, and turns off the charger when the batteries are fully recharged. For this reason, only a battery charger specified by the manufacturer of your mower should be used.
Bonus Battery Care Tips!
What’s the lifespan of deep-cycle batteries?
Do cold temperatures affect my batteries range?
The standard operating temperature of deep-cycle batteries is room temperature, 77F. Accordingly, battery capacity – or, range – decreases with lower temperatures Operating an electric riding mower at 32F will decrease the run time by approximately 20%. Additionally, varying temperatures can adversely affect the recharging process, which is why batteries should ideally be recharged at room temperature.
How should I store my batteries?
It’s recommended that batteries are stored in a cool, dry place, but not below 32F, and charged every one to two weeks, ensuring that they remain fully charged, preventing deterioration. Stored deep-cycle batteries, including those installed in a stored electric riding mower, lose up to 15% of their charge each month – and if left uncharged, sulfation will destroy the batteries. Also, extreme heat can cause the lead within the batteries to deteriorate, so storing them at room or cooler temperatures is important.
Click on this link: Buy the Cub Cadet RZT S Zero at Select Cub Cadet Independant Dealers.
Click on this link: The Ryobi RM480e is exclusively available at The Home Depot here.
Feel free to ask questions in the comments below.
- Cub Cadet Professional Shop Manual RZT-S Zero Electric #769-08008
- Ryobi RM480e OPERATOR’S MANUAL
- All About Batteries
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