A New Ryobi Tool

[Jim Frye]

Not an easy decision, is it? I've thought about a battery-powered mower but have not taken the leap. Please let us know what you decide, I'm curious where you will end up :-)

A neighbor down the street recently purchased an eGo self propelled 60 volt walk behind and swears by it. He's a retired electrician, sohe's pretty savy on such things. He also drives a Cmax and hasa good handle on battery costs. We also have another neighbor that has a battery powwred walk behind and 2 years into ownership. He also swears by the technology.

[Carlos]

That's another facet of it, but generally, we have less control over temperatures than we have over charge state. It's *easy* to pull batteries when done, or remember to not top them up all the time. But I'm unwilling to spend the effort to bring tools in from the garage every day. The rest of the batteries just sit in the house at room temp. So outside of freezing them, not storing them full is something you can do to preserve them. At room temp, you save about 15% of their life per year by not keeping them full.

[WLee]

This chart shows how much more damage is done to a fully charged battery in storage...

Actually it shows the problem of HEAT, especially HIGH HEAT conditions.

Keep in mind the degrees in the LH column are Celsius/Centigrade, not Fahrenheit. The *major* degradation occurs when the batteries are stored fully charged somewhere "HOT" (40° C = ~104° F, and 60° C = ~140° F) -- the degradation is significantly less at anything humans consider "normal" (or "room") temperatures... i.e. 25° C = ~77° F.

So I suppose it depends on where you live (locale).

One should also note that *performance* of batteries is also somewhat "temperature dependent" -- it's sometimes referred to as the "Goldilocks" zone or syndrome/phenomenon (i.e. MOST battery chemistries -- both in term of lifespan AND performance -- are "good" only when the temperatures are neither too hot nor too cold, but "just right" in the middle -- coincidentally WE like the temps about the same {although arguably batteries are at there BEST, just a bit COOLER than we prefer}).

[woodturner]

Yeah, I thought that at first, but after a lot of research, it may not be so outrageous. The Troybilt TB30 E (30") lists for $2,499 also, but only runs for an hour. The CubCadet RZT™ S Zero Electric (42") also runs for just an hour also, but lists for $3,999. The closest Toro is a 42" gas engine powered model that lists for $3,400.

Not an easy decision, is it? I've thought about a battery-powered mower but have not taken the leap. Please let us know what you decide, I'm curious where you will end up :-)

[Carlos]

Here's a start for your research:

[Carlos]

I did not express any opinions, I'm just repeating what's well documented. The information is right there, you can go look it up (you even posted the link to the article saying the same thing I said). Although I should have added one detail; the BEST way to keep the longest total life is to store them at about 40%. However self-discharge makes that challenging. So 70% is used by my chargers as storage voltage. Maybe that's where you take exception? Dunno. Either way, storing them full is always bad.

3.85V
If left fully charged, the cells in a LiPo will unbalance quickly. Proper storage voltage for a LiPo is 3.85V per cell. Most LiPo chargers have a storage function that will either charge or discharge your battery until it hits 3.85V per cell.

This chart shows how much more damage is done to a fully charged battery in storage...

[Jim Frye]

Seems quite high in price.

Yeah, I thought that at first, but after a lot of research, it may not be so outrageous. The Troybilt TB30 E (30") lists for $2,499 also, but only runs for an hour. The CubCadet RZT™ S Zero Electric (42") also runs for just an hour also, but lists for $3,999. The closest Toro is a 42" gas engine powered model that lists for $3,400. There are a couple of rear engine gas riders that list for less than the RM480e, but they have 30" decks with a single blade and don't cut as well and are not as well built. These $1,400 to $1,900 mowers are certainly cheaper, but according to reviews, are not as robust as the Ryobi unit. My neighbor is going to be using a CubCadet CC30 rear gas engine manual transmission mower ($1,399) to mow his 90'x320' lot. The 30" mower is new and it will be interesting to see how well it holds up to the job. He's an engineer, so he knows how to care for stuff.

[woodturner]

Lithium rechargeable batteries are best stored and shipped at 70%, not full. The Battery University link above tells you that, and it's easy to research it to see that everyone agrees on that.

You are entitled to your opinions, but please understand that engineers and scientists designing batteries and battery-powered products, as well as the battery manufacturers and documented research, disagree with essentially everything you have posted.

We essentially disagree with everything you posted, so it's pointless to continue discussing it with you.

[Carlos]

Lithium rechargeable batteries are best stored and shipped at 70%, not full. The Battery University link above tells you that, and it's easy to research it to see that everyone agrees on that. I unboxed a new tablet device yesterday, and it was at 65% out of the box. Normal. Straight off the manufacturing line, most rechargeable lithium batteries are 60-90%, depending on the manufacturer and process.

The law requires air shipments of rechargeable lithium batteries by vendors to be at 30% charge, no higher. I don't think it applies to consumers shipping them, but haven't researched that detail. Batteries inside a full device can be shipped at a higher level.

Self-discharge rates vary by the quality of the battery (impurities accelerate it). The self-discharge rate of the battery itself is only 1-3% per month. If it's a battery with its own brains, that can add another couple % of loss. I've seen this myself, and it's also well documented. We have some batteries that have sat for a year without use, and they are typically at around 70% remaining when I recharge them. Primary lithium cells have even lower self-discharge rates.

A lead-acid battery in a warm place will lose 50% in six months. It's very temperature-dependent and in cold, it will lose a lot less.

If you truly want the max lifetime from a Lipo, you should discharge it to 70% if it won't be used right away, until the next use. Of course, that's terribly inconvenient in most cases. But it's why they are normally not shipped at 100%. We have two high-end programmable chargers with a storage mode that brings them to that level automatically. This is yet another reason why they should never be left on the charger.

High temperature is the enemy. In particular, do not recharge them if they are hot from usage.

[woodturner]

WT,
I am glad you brought this up. The key to leaving them in is - many/most LiOn batteries / battery chargers are built for that purpose. However in the smaller electronic world of cheap cell phones and small size electronics, they want to get by as cheaply as possible to sell as cheaply as possible. THESE, that situation, is where leaving batteries in - is NOT recommended. Those cheap chargers as were many early LiOn chargers did not have the self regulators on them, causing problems and even fires. I cannot give specific facts, but I do remember that early LiOn battery chargers and accompanying batteries said not to leave it in much longer past full charge. I remember that because I thought that was pure stupidity - who in the world is going to stay around a charger to see when it was done to take it out! Then we got a cordless vac with LiOn batteries about 5 years ago. There were mixed reviews on Amazon with people saying that batteries were NOT supposed to stay in past charge, and those that said they could. The actual instructions said that they could. The charger did/does have the regulator.

If the charger does not have the conditioning electronics, it could damage the batteries. I was not aware of the cell phone issues you reference, perhaps it is limited to specific brands or models or has been resolved in newer products. I typically use $5 smart phones on free providers, and they have the conditioning circuitry - but they are also name brands like LG and Kyocera, just older models or refurbs.

One of the limitations of Li-Ion is the relatively high self-discharge rate, about 10% compared to 5% for a lead acid battery or 0.3% for an alkaline (source: industry standards, battery manufacturers, published research and testing battery education battery university ). Environmental conditions such as temperature and humidity can increase the rate significantly. As a result, people want to leave them on the charger so they are ready to use when needed. In addition, the batteries can self-discharge to the point of damage if stored too long without charging, one reason they are normally shipped fully charged and with a shelf life. I think most people leave their cell phones on the charger often, and it's impractical to expect the general public to monitor their cell phone charging carefully. FWIW the charging circuitry is usually in the phone SoC now, so it's essentially provided "for free".

Ryobi chargers and most tools have the regulator to allow charging only for what is needed, allowing a battery to stay in the charger for even days on end. I will often put an 18V battery in my charger and not go back into my shop for two or three days, at which time I remove it and it is not hot.

It would be interesting to know if there are still any current products that do not have the battery and charge monitoring circuitry. Everything I have looked at for the last couple of years has had it.

[Carlos]

I just had a weird battery experience. I have a brand new battery directly from the manufacturer of a quadcopter, which I got in March, and never used. I got it with 67% charge remaining, normal for storage. I charged it fully, and put it in the backpack for the quad. I haven't flow much recently, and had used the other batteries only. Today I was going to assess damage to a neighbor's roof from a recent storm, so I topped off the battery again, which was at 91% to start with. I flew around for a few minutes at slow speed, getting video and pictures of the damage and inspecting the rest of the roof. Just as I was finishing up, I got a low battery warning. I hit the auto-return button and the quad landed with just 6% left. This quadcopter normally has over 20 minutes of flight time even when being flown pretty fast, and this was mostly a hover and photo thing. It should have lasted 25-30 minutes. No idea what happened here, and I'll contact the manufacturer tomorrow. This would have been a very bad thing if it were in drone mode or I was flying far.

I've had short runs on batteries before when they start to go bad. The charger says full, but then you only get a few minutes out of it. But never on a new battery.

[Jim Frye]

Keep talking, it keeps reminding me how lucky I am not to have grass! LOL

Oh we have grass, but it's a dry grass!

[Carlos]

Keep talking, it keeps reminding me how lucky I am not to have grass! LOL

[Jim Frye]

I have learned some more about this mower and hopefully folks aren't sick of me blathering on about it. I'm getting more and more convinced that it's not a bad buy at $2,500. The RM480e packs 48 volts and 4,000 watts of power in its battery pack for two hours of run time. The comparably priced Troybilt TB30 E uses a 56 volt max., 1,500 watt pack for one hour of run time, but reviewers say that when votage drops to 50 volts, your'e pretty much done mowing. Troybilt (MTD equipment) says about a 4 hour recharge time from 50 volts. Ryobi says 12 hours to recharge the RM480 from completely discharged. If I have to mow more than an hour, I think I see the advantage.

The good news is that we just bought a year old Honda Fit executive car, saving $4,000 off of MSRP, so SWMBO thinks we can afford the electric Ryobi.

[Carlos]

Self-discharge rates are nearly nothing on Lithium batteries. The best case is that the charger is high end enough to disconnect the battery when it is done. Many are less intelligent and lead to things like ballooning batteries, as Hank noted. It is always safe to have the batteries off the charger for months, it MIGHT be safe to have them on the charger. I have close to 300 LiPo batteries in my house, there's certainly no way for them to live on chargers all the time. We have a couple of very smart programmable chargers. The tool batteries come off the charger within a day of finishing, and the daily-use 18650s come off when I happen to walk by and see the charge is done. Many years ago I had bought into the idea of leaving them on the charger and that they should always be topped up, which lead to a bunch of ballooned batteries. Expensive lesson learned, now we try to pull them right away.

Our Li-Ion hand vac recommends removing it from the charger, and not recharging all the time. The same thing that Apple says, in fact, and they lead in long battery life.

The article linked above explains the reasons why you should remove batteries from the charger for maximum overall life. Here's one gem from it (I've read that article a few times over the years).

Li-ion cannot absorb overcharge. When fully charged, the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium and compromise safety. To minimize stress, keep the lithium-ion battery at the peak cut-off as short as possible.