Reconfigurable battery pack... and my new drill

[scaesare]

There's been talk reconfigurable battery packs since the new "350KW" CCS chargers have been announced, and a few installed. Those chargers only can deliver higher power at upwards of 1,000 volts. Most EV's today are ~400-450V max packs.

There's been some talk of reconfigurable packs that allow for 400V operation but 800V charging... in essence splitting the pack in 2 and placing those halves in series during charge sessions.

So I just bought a DeWalt hammerdrill, and it comes with a "Flexvolt" 20/60V (peak) pack. It'a a 15-cell pack that can configure itself as either a 20V/6Ah or 60V/2Ah pack, depending on the tool it's in. There's a physically-actuated contactor that turns it from a 5S/3P pack to a 15S/1P pack.

Although in this case it is the reverse of the car-scenario: it charges at the lower voltage, but can operate loads at the higher voltage (allowing for greater power delivery with the same sized conductors).

The also have 20V/12Ah/60V/4Sh version... an impressive 216Wh of energy. My guess is that handheld pack is capable of delivering over a kilowatt of power.... all without a cord.

They also have a clever shipping "guard cover" that is used... it not only covers the electrical terminals, it puts the contactor in to a "disconnected state", so that it's no longer a >100Wh pack, requiring special hazardous shipping/handling. Instead, it's a set of three 65Wh packs that happen to be in the same plastic case.

Pretty cool.

Here's the (admittedly testosterone-filled) video about it:

 

[scaesare]

To add to this topic not too many seem to care about, I just bought the DeWalt Flexvolt Circular Saw

In looking at the specs, I realized it say's this 60V battery powered saw has a power rating of 2400 watts. That's 40amps the pack would have to deliver. That's also 33% more power than a 120V corded saw could deliver

It comes with a 60v/3Ah battery. That implies over a 13C discharge rate for those cells at max power.

Impressive.

 

[animorph]

800V is a good way to get more power (and efficiency) through a connection than you could with 400V, simply due to halving the current. But if we're already charging individual cells as fast as they'll go it'll do nothing for charging speed.

I'd be more excited about battery cell charging speed enhancements than switching to 800V.

 

[skitown]

To add to this topic not too many seem to care about, I just bought the DeWalt Flexvolt Circular Saw

In looking at the specs, I realized it say's this 60V battery powered saw has a power rating of 2400 watts. That's 40amps the pack would have to deliver. That's also 33% more power than a 120V corded saw could deliver

It comes with a 60v/3Ah battery. That implies over a 13C discharge rate for those cells at max power.

Impressive.

Dangit, you've got me looking to replace my old Hitachi cordless toolset with these now! Let me know if you'd have any hesitation after you use them a bit.

 

[scaesare]

800V is a good way to get more power (and efficiency) through a connection than you could with 400V, simply due to halving the current. But if we're already charging individual cells as fast as they'll go it'll do nothing for charging speed.

I'd be more excited about battery cell charging speed enhancements than switching to 800V.

It indeed will be interesting to see what the technical capabilities of Porsche's 800V Taycan pack are..

 

[David99]

As @animorph said, switching the voltage in a battery pack doesn't change it's ability to charge faster. Higher voltage has the advantage of lowering the Ampere which eliminates some losses. This helps with wiring of high power chargers and performance cars for sure. I think that's why Porsche is going with 800 Volt.

It comes down to the C-rate when charging. Tesla charges at 1.5 C peak. But peak rate is only half the truth. My old 85 charges at up to 120 kW but only for the first 20%. Then it drops continuously. The 100 and Model 3 actually have a slightly lower peak, but can sustain a higher rate for much longer thus charge faster overall. On a typical road trip they charge 30-50% faster than the first generation packs (85). Without increasing the peak power Tesla increased the charge speed quite a bit. I wish people would see and discuss that rather than talking about the theoretical peak charge rate.

Here is a graph of the Audi eTron. It charges faster than any Tesla. The peak power is 150 kW which is only 25% faster than Teslas, but it sustains that high rate up to almost 80% SoC effectively bringing down the charge time by 50%.

 

[scaesare]

Dangit, you've got me looking to replace my old Hitachi cordless toolset with these now! Let me know if you'd have any hesitation after you use them a bit.

Sure thing. Thus far haven't used the circular saw yet... but it's no joke just in comparison to the previous one I had, which is the one based on their previous gen 18V Ni-MH technology (18V/2Ah packs).. probably going on 12+ years old. It's definitely beefier/torquier.

I have used the drill a bit, and it's also definitely superior to it's prev-gen 18V counterpart... and I put that thing through the wringer (mixing augurs on 5-gal buckets of quick-set).

My new sweetheart is the impact driver. This product didn't exist in the previous gen set of tools I had, and it's a game changer for driving fasteners. I just installed some heavy-duty steel garage shelving, and it drove 3" 5/16" lag bolts in to the stud in nothing flat with one hand and no wrestling. I broke one bolt off on only the second setting. It also made short work of some 3" drywall screws that wanted to round-out using a regular drill/driver.. the impact feature makes a significant difference.

I haven't had a chance to use the reciprocating saw yet either.

These are all the XR Brushless versions of the tools..

 

[scaesare]

As @animorph said, switching the voltage in a battery pack doesn't change it's ability to charge faster. Higher voltage has the advantage of lowering the Ampere which eliminates some losses. This helps with wiring of high power chargers and performance cars for sure. I think that's why Porsche is going with 800 Volt.

It comes down to the C-rate when charging. Tesla charges at 1.5 C peak. But peak rate is only half the truth. My old 85 charges at up to 120 kW but only for the first 20%. Then it drops continuously. The 100 and Model 3 actually have a slightly lower peak, but can sustain a higher rate for much longer thus charge faster overall. On a typical road trip they charge 30-50% faster than the first generation packs (85). Without increasing the peak power Tesla increased the charge speed quite a bit. I wish people would see and discuss that rather than talking about the theoretical peak charge rate.

Here is a graph of the Audi eTron. It charges faster than any Tesla. The peak power is 150 kW which is only 25% faster than Teslas, but it sustains that high rate up to almost 80% SoC effectively bringing down the charge time by 50%.
View attachment 360510

Agreed... not sure who you are speaking too, but I wasn't suggesting otherwise. C-rate is C-rate at the cell level.

Just drawing the comparison to how a pack can be reconfigured... and that's apparently what the Taycan is doing with their claimed "20 mins to 80%" charging.

Incidentally, the DeWalt FlexVolt 60V packs use 2170 cells, whereas their straight-20V packs use 18650's.

The FlexVolt backs are rated at 2, 4, or 4 Ah packs when operating at 60V (however they actually they market them with their 20V capacities, so 6, 9, & 12 Ah). Interestingly, each of those packs appears to be a 15 cell pack (their physical size looks identical). So, in the 60V (15S/1P) configuration, that means it's the current limit of a single cell that determines what the pack can deliver.

Thus even their largest pack uses only a 4Ah rated 2170 cell... a good deal less than the ~5Ah Tesla's 2170's appear to be rated at. The lesser packs are only 3 or 2 Ah cells, respectively.

My assumption is that they may be optimized for current delivery, over energy density. I'm not sure what pack that saw needs to deliver it's full 2400 watt output... but if it can do it with the 3Ah pack, that's a 13.3 C-rate discharge... and with the 4Ah pack it's still 10C.

2.4Kw from a 3.2lb pack that fits in the palm of your hand is kind of mind boggling... even if it would only last 10 mins at that discharge rate.

 

[skitown]

Sure thing. Thus far haven't used the circular saw yet... but it's no joke just in comparison to the previous one I had, which is the one based on their previous gen 18V Ni-MH technology (18V/2Ah packs).. probably going on 12+ years old. It's definitely beefier/torquier.

I have used the drill a bit, and it's also definitely superior to it's prev-gen 18V counterpart... and I put that thing through the wringer (mixing augurs on 5-gal buckets of quick-set).

My new sweetheart is the impact driver. This product didn't exist in the previous gen set of tools I had, and it's a game changer for driving fasteners. I just installed some heavy-duty steel garage shelving, and it drove 3" 5/16" lag bolts in to the stud in nothing flat with one hand and no wrestling. I broke one bolt off on only the second setting. It also made short work of some 3" drywall screws that wanted to round-out using a regular drill/driver.. the impact feature makes a significant difference.

I haven't had a chance to use the reciprocating saw yet either.

These are all the XR Brushless versions of the tools..

Thx. Sorry if I missed it, but did you get a combo kit along these lines or did you buy them piecemeal?

Edit: replaced incorrect link
DEWALT 20-Volt MAX Lithium-Ion Cordless Brushless Combo Kit (2-Tool) w/FLEXVOLT and 20V Batteries, Bonus Circ Saw and Recip Saw-DCK299D1T1W391380 - The Home Depot

 

[scaesare]

Thx. Sorry if I missed it, but did you get a combo kit along these lines or did you buy them piecemeal?

Edit: replaced incorrect link
DEWALT 20-Volt MAX Lithium-Ion Cordless Brushless Combo Kit (2-Tool) w/FLEXVOLT and 20V Batteries, Bonus Circ Saw and Recip Saw-DCK299D1T1W391380 - The Home Depot

I couldn't find a combo kit that had all the XR tools I wanted, so I ended up buying:

- This Flexvolt Drill/Hammer Driver Combo pack (by far best price I found for 3-speed hammerdrill & flexvolt battery)

-This Recipro Saw (bare tool), taking advantage of their $25 off $100 DeWalt special

-The bare tool version of this Framing Saw (they only seem to have the bundle now... the bare tool was on sale for $169, which was a substantial discount from the $219 best price I had seen), along with an additional Flexvolt on sale for $80)… the total was over $199 so free shipping.

- This Worklight (had some bunus points to spend)

-I had earlier bought an Amazon special of 2-pack of 5Ah XR batteries plus charger for ~$100 (hence getting the bare-tools above)


I was able to get the pieces I wanted that don't' come in a pre-built combo kit for similar combo pricing all told with sales and discount codes... and ended up with a couple extra batteries and to chargers.

I also snagged some bits and impact sockets.

 

[David99]

I can see how a swtichable battery pack can be good for power tools. Some tools were designed for 20 Volt, others for 60 Volt to accommodate more power draw. A switchable battery now can be use in the old and new tools. I don't see the need nor advantage for EVs, though. Once you design an EV for the higher voltage there is no benefit going to a lower one. Maybe to be able to charge at old charging stations that don't support the higher voltage?

 

[scaesare]

I can see how a swtichable battery pack can be good for power tools. Some tools were designed for 20 Volt, others for 60 Volt to accommodate more power draw. A switchable battery now can be use in the old and new tools. I don't see the need nor advantage for EVs, though. Once you design an EV for the higher voltage there is no benefit going to a lower one. Maybe to be able to charge at old charging stations that don't support the higher voltage?

I think that's one reason.

It would also make the cable management at chargers targeting significantly higher power delivery more tenable.

It also may be that motor and inverter design at the higher voltages may be more challenging and/or expensive.

 

[Brando]

Well, if someone with EE degree AND some practical experience, I'd like to read their ideas.
JB/Elon/Tesla Team aren't exactly stupid about these things. Interesting to know what they think.

Audi? Can't tell the truth about diesel. e-Tron not exactly impressive at this point. Charging networks for VW group seem a disappointment to me. Delays and more delays and distractions to keep us on big oil.

Not so sure I believe VW Group even about charging claims.

“Under the terms of the settlement, states can spend their share of the Environmental Mitigation Trust funds in several different ways, including by purchasing newer diesel vehicles, natural gas vehicles, and electric vehicles, as well as repowering older diesel vehicles with newer engines or electric motors. States are also allowed to use up to 15 percent of their award on electric vehicle (EV) charging infrastructure.”

more details:
Many States Squander VW Settlement Money, US PIRG Report Shows | CleanTechnica

side note: public transit - IF you have ever been on public transit most anywhere out side the US, you know how poor it rates.
Public Transit Buses ~ 70,000 in the US [please try to verify, my memory of US electric bus maker]
School Buses - only used twice per day = ~ 400,000 - Kids can't use public transport? Of course not. That is how bad our transit systems are. Sad.

PS- great to read about battery tools - thanks.