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Makita DGA900 - 18v X2 - 9Inch Grinder


kornomaniac

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2 hours ago, Makita_2233 said:

The makita 5" is fine for all day use with a flap disc. I've had the fuel but get heaps of thermal overload of the batteries when pushed hard 

 

Good to know! And it's all I need too. At the end of the day, it is a little below a regular 700W electric grinder in power, which is fine for heaps of people and applications.

 

I'm just saying that there a people who aren't satisfied with a 700W grinder, and upgrade to a 1100W - 1500W 5" grinder. These types (heavy industrial grinding) aren't going to be satisfied with the regular 18V 5". 

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Yep, the BL Bosch on a CORE battery was the first 18V unit I've used that was about equal to my basic 720W grinder at home. Hopefully the new Dewalt 18V/20V with FV battery will too. oztooltalk is going to review the Metabo 5" with LiHD battery shortly, so I'll know the answer to that question :)

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10 hours ago, dwain said:

 

 

 

I'm just saying that there a people who aren't satisfied with a 700W grinder, and upgrade to a 1100W - 1500W 5" grinder. These types (heavy industrial grinding) aren't going to be satisfied with the regular 18V 5". 

The rpm on the fuel and makita is painfully slow when cuttung/grinding, good for a flap disc. 

 

Check out the metabo 7" bl 18v, its same size at the 5" 

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10 hours ago, dwain said:

 Hopefully the new Dewalt 18V/20V with FV battery will too.

The new dewalt grinder will get longer run with the 20v max XR6.0 with double row 20700 cells vs the FV 6.0. My dch293 gets more holes drill with the 20v max XR 6.0 than the FV 6.0. I'm only assuming at this point until I get the new dewalt grinder 

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12 hours ago, Makita_2233 said:

The new dewalt grinder will get longer run with the 20v max XR6.0 with double row 20700 cells vs the FV 6.0. My dch293 gets more holes drill with the 20v max XR 6.0 than the FV 6.0. I'm only assuming at this point until I get the new dewalt grinder 

 

Hmm interesting point. I don't even know if we're getting the 18V 6.0Ah battery in Australia, so I may never know :(

 

There's an interesting relationship between current output (A), heat/resistance and runtime (Ah), and it's one that I don't think I'll ever fully understand. Battery cell chemistry, who could understand it!?

 

I've picked up that 7" 18V Metabo grinder, and you're right, the body is the same as the 5". Hope I get to review it some time ....

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4 hours ago, dwain said:

 

Hmm interesting point. I don't even know if we're getting the 18V 6.0Ah battery in Australia, so I may never know :(

 

There's an interesting relationship between current output (A), heat/resistance and runtime (Ah), and it's one that I don't think I'll ever fully understand. Battery cell chemistry, who could understand it!?

 

I've picked up that 7" 18V Metabo grinder, and you're right, the body is the same as the 5". Hope I get to review it some time ....

Dewalt were talking about the end of the year maybe but I have my doubts. They just released flexvolt kits with 18v tools and FV batteries. U.K. Doesn't have the 18v 6.0 and we get what they get. I bought some in America, also a eBay seller in Melbourne importing and selling them here. 

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5 hours ago, dwain said:

 

 

There's an interesting relationship between current output (A), heat/resistance and runtime (Ah), and it's one that I don't think I'll ever fully understand. Battery cell chemistry, who could understand it!?

 

Looking at the XR 20v max 6.0 next to the FV 6ah you wouldn't think you would get longer run time. Like you said who would understand it haha. Another reason why they may hold off bring the 18v 6.0 here they don't want it competing with the FV 6.0  

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On ‎27‎.‎09‎.‎2017 at 12:35 AM, dwain said:

 

Hmm interesting point. I don't even know if we're getting the 18V 6.0Ah battery in Australia, so I may never know :(

 

There's an interesting relationship between current output (A), heat/resistance and runtime (Ah), and it's one that I don't think I'll ever fully understand. Battery cell chemistry, who could understand it!?

 

I've picked up that 7" 18V Metabo grinder, and you're right, the body is the same as the 5". Hope I get to review it some time ....

Current output (power density) and energy density is a tradeoff in the first place, you can't be very good at both. Runtime depends on both in a way, more capacity - more runtime is logical and correct, but at high loads (which tools are) internal resistance as an effect on runtime as well. Internal resistance decides how much Energy is wasted in the cell, and how much you can use. The power wasted in the cell grows at square to the current you draw (as power does), therefore the effect can get very considerable.
 

With 18650 cells the goal over the years was (at least we can assume from how the cells react) to get more capacity and not hurting the internal resistance too much (we know it is a tradeoff). So you can draw 30A for 5s from an 2009 1,5Ah cell and from an 2016 3Ah cell and get basicly the same. The voltage will drop according to the internal resistance and you will get similar power out, and heat up both batteries about the same. So, now you look at the datasheet and see, wait the 1,5Ah cell is rated at 30A continuous discharge, and the 3Ah cell at 15A. The reason beeing, the 1,5Ah cell is empty before it can get too hot. They can supply both similar currents - if you use it in a drill or an impact, but in an angle grinder you would send the batteries with 3Ah cells into thermal overload quickly.

 

So with 20700 (and 20650 and 21700) cells they went a new direction. They could use the bigger cells to lower internal resistance. Low internal resistance is very pleasant, you can get more current output, more power output and less wasted power due to heat. The first generation 20700 cells are the 3,1Ah Panasonic NCR20700A cells, featured in Metabo LiHD, DeWalt 18V 6Ah, FlexVolt 9Ah, Bosch Core/Eneracer and as we know these work an absolute dream. Continuous discharge rating is 32A with room for 40 or 50A overloads, no worries.

 

To get back to the FlexVolt 6.0 and XR 18V 6.0 comparison, DeWalt wanted to make an physically smaller 18650 version and the beast 20700 version of FlexVolt batteries. But the FlexVolt tools are very much high drain tools, and to avoid thermal issues they hat to go for a quite low energy 18650, a 2Ah cell. Samsung INR18650-20Rs Of course they may have been revised for extra % at internal resistance over the years, but the 20R is a quite old design still. Nothing really wrong using them, they are well chosen for the application and as we know with 18650 at those levels of power you can't make a better choice. Now the XR 18V 6.0 (which is really a 6,2 Ah to be honest) are a few years newer and get you just very good power density and still good energy density, as you expect with the latest technology. As far as i know the internal resistance of 3 paralleled up 20Rs (FV) and 2 NCR20700 (XR6.0) should be similar, the XR6.0 has a slight capacity advantage - so the runtime is comparable. The advantage you get from the newer tech is the size in this instance.

 

And what does a third row of 20700s do to your runtime?

50% more capacity + lower internal resistance = over 100% more runtime.

EDIT: Oh and DeWalt, we do want the 18V XR 6.0 battery EXTREMLY bad here in europe, at least i do. Pleease make it happen :o

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5 hours ago, m.k said:

 

 

50% more capacity + lower internal resistance = over 100% more runtime.

EDIT: Oh and DeWalt, we do want the 18V XR 6.0 battery EXTREMLY bad here in europe, at least i do. Pleease make it happen :o

Great post 

 

I get more holes drilled on the dch293 20v max sds 28mm rotary with a 20v max XR 6.0 vs the FV 6.0 

 

From memory I was getting 4 more diameter 18mm holes at 160mm deep vs the FV 6.0

 

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