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Post by huntsgemein on Sept 18, 2020 22:12:34 GMT -5
To illustrate this, I use the analogy of a water pipe or hose. If the hose is skinny, it's highly resistive. You can increase the flow of water (electrons measured in Amperes) by increasing the pressure (in Volts). Up to a point, beyond which resistance becomes a limiting factor with friction losses, or heat in a cable. Irrespective of forever increasing pressure, there's an absolute max flow possible from any given diameter.
With fixed voltage pressure, the limiting determinant in electron/water flow is solely the preserve of the pipe/cable diameter. The less resistance for a given pressure, the greater the flow. The wider the hosepipe, the less resistance there is.
If you want those big 1.2 or even 1.6 Kw peaks at such low voltage (18V) pressure, then you really need those nice big fat minimally resistive conductors.
I've had Li Ion batteries (& drill) get almost too hot to handle when worked hard: Bosch cordless drill hole-sawing cableways through structural steel girders.
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Post by holmz on Sept 19, 2020 22:30:42 GMT -5
To illustrate this, I use the analogy of a water pipe or hose. If the hose is skinny, it's highly resistive. You can increase the flow of water (electrons measured in Amperes) by increasing the pressure (in Volts). Up to a point, beyond which resistance becomes a limiting factor with friction losses, or heat in a cable. Irrespective of forever increasing pressure, there's an absolute max flow possible from any given diameter. With fixed voltage pressure, the limiting determinant in electron/water flow is solely the preserve of the pipe/cable diameter. The less resistance for a given pressure, the greater the flow. The wider the hosepipe, the less resistance there is. If you want those big 1.2 or even 1.6 Kw peaks at such low voltage (18V) pressure, then you really need those nice big fat minimally resistive conductors. I've had Li Ion batteries (& drill) get almost too hot to handle when worked hard: Bosch cordless drill hole-sawing cableways through structural steel girders. If we are using plumbing references then here is one, We use the dunny, we then want to send the processed meals through the S-Bend at a great rate of knots. If we use a 50-mm water pipe it can hurls it into the sewer pipe with a fast flow of water. This is the same way that we can use a massive cable for 1600W peak load. Or we can use a small water pipe and store the water in a cistern above the toilet bowl, and maybe it take a minute to fill that reservoir... Then when we need a great quantity of water, it dumps the reservoir instantly into the bowl. A capacitors is the electrical equivlent to a reservoir... so we can fill it (the capacitor) at the tool end and use a cable large enough for maybe 10A or 20A continuous load, but tha capacitor can drop 100A into the tool over a second or so when it is needed for startup... it smooths out the delivery in the cable leading to the tool.. |
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Post by alvychippy on Sept 20, 2020 6:19:05 GMT -5
okay, let me tell you, how clever I am! (  ) ("sparky"- electrician that explained few bits to me) put me straight, in relation to my 28v DeWalt plunge saw being cordless (gutless) and difference to the Corded one (110v) is that power delivery management electronics on the saw are very different. Yes, one issue is power delivery on start up (possible to solve by adding capacitor or a "soft start" circuit) is only half of a problem, but unbalanced power delivery upon load would mean the same issue for cordless tool, as how most corded tools get their brushes burned- too low of an amperage.... whilst to manage (28v) is easy from battery, from a charger set current (DC charger) is continuous (half) of optimal current, so as soon as you push the saw little faster, underpowered "charger current" will not be enough and brushes will take the brunt, instead of strong current power supply designed corded tool motor configuration. but, hey! I can only go by what figures say and in my circumstances half of designed delivery discharge, can not possibly be enough to make a cut of 5s or longer, unless to fit that big of an capacitor, that could deliver the right output (shortage) for the length of a cut (lets say 2 minutes)... unless someone with good electrical knowledge is willing to measure up actual power consumption at the motor and design an adapter with electronics to match it perfectly, I'll be thinking about it... To summarize, what I am mumbling about: The adapter would need to have electronics and capacitor to make/manage exact same delivery as battery discharge for at least 2 mins, load up and be ready to deliver again (in 30s perhaps)... Basically to end up better, than Ni-Cad batteries can deliver the power, hence rather mental prices for Li-ion batteries, that still lack behind normal corded tools for power delivery in practical terms, near 10 years later, said / promised "equal" to be. Really hope, I'm making sense. Really hope, somebody would be able to design such product properly Really hope, such would end up being made in order to end the nightmare of a solution for all power tools, as these days auto-take-off is more or less standard on all dust extractors, "Bluetooth" connection is one more of those "gimmick of an solution, to an additional industrial tool power delivery problem". |
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Post by hecon5 on Sept 21, 2020 8:16:06 GMT -5
Short Version: If you want a corded tool, buy a corded tool.
Long Version:
So, this is funnily enough an area I'm EXTREMELY well suited to pontificate about. Anyway, here goes.
The issue is multifaceted. - Battery tools are much more sensitive to over/under-voltage conditions than mains tools.
- They tend to have much more dynamic load profiles (who runs a battery screw gun / saw continuously for 20 minutes? No one, that's who) as they go up/down/up/down as you screw/drill holes and then stop to do the next/take a break/setup next cut.
- Batteries are really good at that loading profile, their internal AC and DC resistance is pretty low compared to a similarly sized mains driven power supply->DC->tool power train.
- Capacitors, for a given weight do not store anywhere near the same storage energy (watt hours / joules) that batteries have (5-20x depending on the capacitor type), they're a LOT more expensive, and finicky. As an example: a battery Capacitor / Battery comparison (full of Ads, but the information's solid).
- That said: they can handle 100/200x more charge/discharge cycles, and their internal resistance is considerably lower, so they can deliver more power in a shorter amount of time, but because they can't deliver as much quantity, unless you don't care about weight (think truck mounted power storage), they're really only good for inrush protection.
- Wires have different resistance for AC and DC loading. A load profile for a drill is ... very dynamic. Especially for new brushless motors. It's not anywhere close to what you'd think of "DC" it's much more like, AC with an angry bear tearing holes in your nice sine wave. As a result, for a drill applications, their effective resistance is closer to their AC impedance value. So you need to up-size them to compensate = weight.
That's just the capacitor part. Then there's the Power Supply (AC mains -> DC power). A 'dumb' power supply here would ruin your fancy brushless drill. Because of the dynamic loading, you need a larger power supply, and would need to set the voltage higher to compensate. This will have the undesirable effect of generating extra heat on your motor and potentially overvolting it when you stop (all that energy you're sending down the wire has to go somewhere, and it goes into increasing the voltage beyond what you'd like). The extra heat and the over-volting will take a big toll on the motor (it will ruin both brushed and brushless motors equally, but brushless will be especially unhappy about the situation).
Enter a smart/dynamic/compensating/pick your marketing term power supply. These will monitor the voltage at the pins and work really hard to keep the voltage right where you want it, and increase their output only when you actually need it, which keeps voltage fluctuations down, which keeps extra heat down, and reduces overvolting. Yay! Your fancy drill isn't blown up!
Downsides to that:
- They're 2-10x more expensive than a dumb power supply for a given watt output.
- They're 4-10x heavier (all those fancy electronics = weight!)
- They probably don't like generators. All those fancy electronics = needy little buggers!
All this to say: batteries, for this case win out EVERY time if you need portability. Even DeWalt's Multivolt system miter saw with a plug in adapter don't have the same available power as their corded counterparts. Sure, it's nice to be able to have both, but if you need the constant power of a corded tool in a battery package, buy a corded tool and a generator.
If you want a corded tool, buy a corded tool.
For all the faffing around you get trying to convert a battery system back to mains, you could buy 2-5 more batteries and be much happier.
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Post by alvychippy on Sept 21, 2020 13:02:04 GMT -5
Short Version: If you want a corded tool, buy a corded tool.
[/div] [/div][/quote] Awesome! Well, I'd love cordless to be as good as corded, hence plundered for ages searching for some solution... That's not happening. Will read it few times over, hopefully, will lay the whole idea to rest Hopefully 😉 Thanks and cheers for that! 🥂 |
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Post by hecon5 on Sept 21, 2020 13:26:30 GMT -5
I will say, that there are some really exciting new power supplies and the like that use GaAs and GaN that will make the above slightly less relevant, but in the shorter and medium term, batteries all the way for portability.
There's a reason MFRs don't make one you can just go buy, and why they keep making bigger batteries vs. wires + mains systems.
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Post by alvychippy on Sept 23, 2020 8:37:30 GMT -5
I will say, that there are some really exciting new power supplies and the like that use GaAs and GaN that will make the above slightly less relevant, but in the shorter and medium term, batteries all the way for portability. There's a reason MFRs don't make one you can just go buy, and why they keep making bigger batteries vs. wires + mains systems. One "minor" issue, when it comes to saws/routers/planers/sanders is dust extraction Cordless simply a joke-1; connecting (auto-start (take-off)) what is available (Bluetooth) is non funcional-2; where's plenty of cordless solutions for cordless tools, they all depend still on corded extractors and is becoming more important aspect, than noise, I would say for working health environment-3. |
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Post by huntsgemein on Sept 23, 2020 21:14:00 GMT -5
I will say, that there are some really exciting new power supplies and the like that use GaAs and GaN that will make the above slightly less relevant, but in the shorter and medium term, batteries all the way for portability. There's a reason MFRs don't make one you can just go buy, and why they keep making bigger batteries vs. wires + mains systems. One "minor" issue, when it comes to saws/routers/planers/sanders is dust extraction Cordless simply a joke-1; connecting (auto-start (take-off)) what is available (Bluetooth) is non funcional-2; where's plenty of cordless solutions for cordless tools, they all depend still on corded extractors and is becoming more important aspect, than noise, I would say for working health environment-3. This concern may not necessarily still be relevant: this new Starmix/Metabo vac has similar suction & capacity to corded iterations. Namely "M" filtration certification, 4000L/min airflow, 240 bar vacuum, 25L capacity, 12 Kg weight & 100 minutes quoted runtime (with 10.0 AH x 2 Li-HD batteries, wet & dry operation with full container shutoff & Starmix auto filter cleaning. Using the vibration sensing attachment on the power tool that is included in the package, this appears to be a true autostart/stop cordless solution. Not cheap at almost 1000 Euros inclusive of tax, I look forward to some user reviews. www.metabo.com/t3/fileadmin/metabo/be/070_actueel/00_specials/Specials_3_2020_BE_NL_web.pdf |
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Post by hecon5 on Sept 24, 2020 7:40:37 GMT -5
I agree, cordless vacs are a missing link. If that cordless vac can double as a supply via the vacuum's battery, it would be a great mobile solution. I still think they'll need a battery vs a mains>DC PSU, but darn if it's not close to great.
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Post by alvychippy on Sept 26, 2020 9:26:13 GMT -5
2x 10ah batteries, so realistically 4x batteries needed for a days work... that would need to be charging "on rota" (2x on; 2x- on charge)... total cost... in addition to the actual tool batteries costs and weight and need to charge...
I'm OK with having corded set up, as 99% of work would be having a power source and .... I'll still keep an eye for a charger /converter / adapter solution as in capacitor to supply what's needed in realistic terms
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Post by alvychippy on Nov 2, 2020 21:11:59 GMT -5
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Post by hecon5 on Nov 3, 2020 5:45:23 GMT -5
That's excellent! While it says only 36V,that's a huge step in the right direction! I also recently saw Makita has a backpack for 4 batteries that can plug into your tool. www.makitatools.com/products/details/PDC01 |
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