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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: rec tech mower
Date: Wed, 16 Apr 2025 07:50:31 -0500
Organization: Yellow Jersey, Ltd.
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On 4/16/2025 4:28 AM, John B. wrote:
> On Tue, 15 Apr 2025 21:45:41 -0700, Jeff Liebermann <jeffl@cruzio.com>
> wrote:
> 
>> On Mon, 14 Apr 2025 22:48:59 -0400, Frank Krygowski
>> <frkrygow@sbcglobal.net> wrote:
>>
>>> Again, I'd love an electric mower, but I'm not aware of one with
>>> sufficient run time to do this lawn. Also, I've read some complaints
>>> that the (rather expensive) batteries last only a few years (like 3
>>> years in some cases) before needing replacement.
>>
>> Battery life is a complex problem.  For LiIon, the more energy (in
>> joules or watt-hrs) you drain out of or charge into a battery, the
>> faster it deteriorates.  You can make a mower where the battery lasts
>> many years, but you'll need to stop draining the batter at about 25%
>> SoC (state of charge) as well as stop charging at about 85% of full
>> charge level (about 4.1VDC with no load).  You'll also need to charge
>> slower than what the battery is capable of handling and use a motor
>> that uses far less power (watts) than what the battery is capable of
>> delivering.
>>
>> Currently (pun intended), battery powered tools are designed to
>> operate at just below the point where something will fail, usually the
>> battery.  With LiIon, both over and under voltage will kill the
>> battery.  Fast charging and fast discharging will accelerate
>> deterioration.  When larger numbers on the spec sheet sells more
>> mowers, then manufacturers will do what is needed to produce those
>> large numbers, even if it prematurely kills the battery.  If they
>> produce a mower or tool that lacks power, takes forever to charge, and
>> requires a physically large battery, the typical consumer won't buy
>> it, even if it promises a battery that lasts forever.
>>
>> There's also the matter of not providing features that will extend
>> battery life but are missing in order to provide a low selling price.
>> What is needed is something like what can be found in RV batteries.
>> For example (in order of importance):
>> - LiFePO4 instead of LiIon
>> - BMS to equalize the voltage of each cell in the battery.
>> - MPPT charging (usually external).
>> - BMS for over and under voltage protection.
>> - BMS with overcharge protection.
>> - BlueTooth wireless for battery on/off, telemetry, SoC, etc.
>> - Modular construction to aid in rebuilding battery.
>>
>> Electric mowers and tools might have a few of these features, but I've
>> never seen one that has all of them.  LiFePO4 and a BMS that equalizes
>> the cell voltages are probably the most important for best battery
>> life.  I've only seen a few LiFePO4 tools.  None of my DeWalt tools
>> have a BMS with cell equalization.
> 
> Why all this worry about electric mowers? Get a liquid fuel mower and
> build a proper exhaust system so it's quit :-)

Personal taste varies. Some guys like straight pipes:

https://www.yellowjersey.org/photosfromthepast/snowchv8.jpg

-- 
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971