Electronics > Projects, Designs, and Technical Stuff
DC motor voltages used on battery lawn mowers; 40, 60 vs 80 affect blade torgue?
james_s:
Mine is probably about that old, but it works so I haven't bothered to look st replacing it.
Forget the voltage, really it's irrelevant to the end user. Read reviews on Amazon and select a mower that is well rated then shop around for the best price.
NiHaoMike:
What I'm surprised about is the lack of power assisted reel mowers, which are far more energy efficient. The actual power needed must be on the order of 100W or less given that fully manual ones exist.
--- Quote from: Siwastaja on April 25, 2019, 04:20:53 pm ---But the sweet area tends to be quite large, as can be seen from the fact that 500hp muscle EVs have been built as sub-100V systems
--- End quote ---
I'm pretty sure Tesla uses 400V battery packs.
--- Quote from: videobruce on April 26, 2019, 07:52:24 am ---I have had my carbon brush, cordless mower for over 17 years which is why I'm looking for a replacement.
--- End quote ---
What's the reason for replacing it?
Siwastaja:
--- Quote from: videobruce on April 26, 2019, 07:52:24 am ---is the any disadvantage of going with a lower voltage design with the same watt/hr rated pack equivalent?
--- End quote ---
From the design viewpoint, when within sane limits, no, but extremes do have disadvantages. For a battery lawn mower, 40, 60 and 80V are all clearly within sane range, and any difference will be negligible. 10V would be clearly problematic, I think, as would 400V.
But because there is not much difference, nothing prevents them from resorting to "design-by-marketing" approach - since a good designer can build the thing at almost any voltage (within certain range and certain options), marketing can design the portfolio of voltages based on non-technical reasons, and the engineering provides. Simply put, need a 40V lawn mower? No problem, pay me and I'll design it for you. Need 100V? I'll do it. They'll perform the same. The 40V version may be even better or cheaper, I don't know without full schematic and BOM level design for both.
But, from the consumer viewpoint, there might be a clear correlation, that 80V mowers are more powerful, or provide more torque than 40V mowers; especially within one manufacturer. This works as long until someone gets the idea to build a very weak product with high voltage battery to get the marketing benefit. This actually happened to some extent on cordless drills; big players like BOSCH, Makita, etc. had (and still have) quite a good correlation of voltage vs. capability, but many cheap brands do use surprisingly high voltages to play the game.
videobruce:
--- Quote from: NiHaoMike on April 26, 2019, 03:24:19 pm ---What's the reason for replacing it?
--- End quote ---
Age,
what appears to be shorter operating time even with a battery replacement,
it's a bear to take inside each Fall since the batteries are not easily removed.
For the last 12-15 or so years, the newer mowers all have removable battery packs since they aren't gel-cells anymore.
james_s:
I removed the two large gel cells from mine after they wore out and replaced it with a harness that I plug in either 2 or 4 3S 2200mAh LiPo packs which is more than enough to mow my small lawn. For me it was a great solution because I already had the LiPo packs and charger for my RC airplanes.
I suspect the main reason drills were going higher and higher voltage is they were using sub-C NiCd/NiMH cells so the max power out of a cell was pretty much capped. Adding more cells was the only way to get more power and if you're adding cells you may as well put them in series and get more voltage rather than parallel which would require heavier wiring and controls.
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