Got 4Ah, not 5Ah, battery 18V (20V) - done right thing?

Amp-hours measures total stored charge, but I think your question is different, basically if the smaller battery will affect the ability to drill hard granite.

If drilling isn't much affected, then the take two and swap approach is perfectly serviceable.

My instinct is that drilling ability will be about the same, but will make fewer drilled holes per charge. Unless these batteries are awfully expensive, I'd just try it.

Joe Gwinn

Hi there

Ran SDS out of battery in one session at the mine - first time.

Is 18V - believe it's badged in the USA as 20V, but the physics of the Li-ion cells surely says in reality it's the same batteries and voltage (?).

Went by tool store - no 5Ah batteries I asked for. Said well it's 12 UKPounds per Amp-hour, and we do have 4Ah batteries.

Thinking - well take two identical 4Ah batteries, swap occasionally, running-down charge in both?

But the draw of the "big" SDS drill - the biggest which takes the "small" batteries - that power draw would go across more cells if a

What do you say?

Regards, Rich Smith

PS - SDS drill drilling the sockets in granite to insert the feathers&wedge to split granite boulders - simply a regular workhorse now. Also use for "misc" other tasks - drill holes into which hammer in wood for screws holding light-fittings, etc, etc.

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My understanding is that Lithiums can be formulated for various tradeoffs between high discharge current and high Ah rating. Unless you find a spec sheet for the cells with the discharge current rating and know how much the drill draws you have to trust the manufacturer's competence and honesty.

In this spec sheet example the maximum discharge current is 6.5A, about twice the Ah rating.

The C rating is the current the battery would provide for 1 hour before falling to some minimum safe or useful voltage, though it's usually measured at a lower current and longer time to get a more favorable higher number.

The Ah you can use in practice may be less than the rating because the battery's internal resistance rises as it discharges and will lower the output voltage under heavy load due to internal IR drop, so the battery terminal voltage hits the minimum before it's fully discharged. The indication is a higher battery voltage after removing the load, or with a lighter load that causes less internal voltage drop, if you have one.

My job was once building the production line test stations that determine if electrical products including op amps and computer memory meet their spec sheet rating. Much of what I bought from Radio Shack and on Amazon didn't quite pass my testing but was still usable, with care.

Hi there

Ran SDS out of battery in one session at the mine - first time.

Is 18V - believe it's badged in the USA as 20V, but the physics of the Li-ion cells surely says in reality it's the same batteries and voltage (?).

------------------------- Don't blame us.

When I bought NiMH replacements for my 14.4V NiCad Dewalt drill I monitored the charging current and voltage to see the difference. On a NiMH charger the "14.4V" NiMH packs cut off the charge at 22V and quickly fall back to

Are these lithium or NiMH? If lithium, which type? Some batteries can safely be discharged at only 1C (4 amps for a 4Ah battery) while others can be discharged at as much as 5C (20 amps), and others only .5C (2 amps) without over-heating or deteriorating the battery. Generally speaking the higher capacity battery is USUALLY better for high discharge loads (heavy duty operation)

On Thu, 16 May 2024 15:43:01 +0100, Richard Smith snipped-for-privacy@void.com wrote: ...

Are these lithium or NiMH? If lithium, which type? Some batteries can safely be discharged at only 1C (4 amps for a 4Ah battery) while others can be discharged at as much as 5C (20 amps), and others only .5C (2 amps) without over-heating or deteriorating the battery. Generally speaking the higher capacity battery is USUALLY better for high discharge loads (heavy duty operation)

-------------------------------- Lithiums for RC models may be rated to deliver 50 ~ 100C discharge current.

This is a good overview of batteries: https://rcplanes.online/guide3.htm

Hi Clare, Jim, everyone. These are DeWalt powertool batteries - 18V (20V?). This characteristic you identify "1C" etc. becomes knowable? Rich S

Hi Clare, Jim, everyone. These are DeWalt powertool batteries - 18V (20V?). This characteristic you identify "1C" etc. becomes knowable? Rich S

-------------------------- On 5/16/24 I wrote: "The C rating is the current the battery would provide for 1 hour before falling to some minimum safe or useful voltage, though it's usually measured at a lower current and longer time to get a more favorable higher number."

The only satisfactory way to determine a battery's C capacity is to discharge it while recording the current and voltage, stopping when the voltage falls to the specified end point, which may be either where the battery may be damaged or the intended load will no longer function. Since this is slow, tedious and requires special equipment there are ways to estimate it, with varying accuracy. The professional way to measure it is with a programmable electronic load. The one I used to test large electric car batteries dumped its heat into a barrel of water.

At home I measure remaining battery capacity on the cheap with multimeters that can send their readings to a computer and either the device that the battery will operate or old surplus high power variable resistors as the load. The rotary type (rheostat) can be adjusted while hot to keep the power draw fairly constant as voltage decreases.

Using the device the battery will operate, typically refrigeration, tells me if the battery can be trusted to operate it overnight, which is more useful than the numerical Amp-hour capacity. An AC powered fridge draws a high startup current which can trip an inverter's low input voltage sensor although the battery could still provide the run current.

This and similar inexpensive devices can be wired into a stationary battery system to act as a 'fuel gauge' that shows the amount of current drawn and the voltage, from which you can determine when the battery has fully discharged and program the Amp-hour value in as C so the meter will then accurately(?) display the percentage of remaining charge. The fuel gauge Amp-hour reading halts at the full programmed capacity and ignores subsequent float charging current.

Hi Clare, Jim, everyone. These are DeWalt powertool batteries - 18V (20V?). This characteristic you identify "1C" etc. becomes knowable? Rich S

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The problem with measuring C for battery tools is breaking the circuit to measure the current. Voltage is accessible by hacking the charger but there isn't room in the tool or battery for a shunt or Hall Effect sensor to measure current, and the battery connectors are very difficult to copy for a latching extension cord. I've had some luck reforming hobby store brass tubing into rectangular sockets and AC line cord plugs into solid brass male pins. I didn't try to fake the plastic housings, just made the electrical connections tight enough for non-mobile testing. Fine stranded silicone insulated wire is flexible enough to not dislodge the connectors.

Forming DIY electrical contacts is much easier with a lathe and milling machine. Collets are preferable on the lathe, to avoid squishing tubing and keep fingers away from chuck jaws. A small 6-jaw chuck is useful though not essential. Mine is on a 5C mount and last served in an indexer to mill a wrench hex on threaded rod, which a collet didn't grip securely enough.

Are these MAX or XR batteries?

If it is a MAX it is a 5S x 2P pack running LG HB4 1865 LiNiMnCoO2 cells rated at 1500Mah with a max current of 30 amps which is a 20C rating!!!.

I strongly suspect the 5Ah pack uses higher capacity cells - which ALMOST ALWAYS means lower max current rating - so you likely made the right move.

If it is a MAX it is a 5S x 2P pack running LG HB4 1865 LiNiMnCoO2 cells rated at 1500Mah with a max current of 30 amps which is a 20C rating!!!.

I strongly suspect the 5Ah pack uses higher capacity cells - which ALMOST ALWAYS means lower max current rating - so you likely made the right move.

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The SKU (Stock Keeping Unit) number matters.

I found in a lot of cordless tools the higher amp hour rated battery the better. Generally I have not noted it for light load tools like a cordless drill using small bits, but things like electric chainsaw, angle grinder, etc it was very noticeable. I do not mean just that the bigger AH rating ran longer. I mean it delivered more current in a short fixed time period. The tool performed better. I've experienced this with relatively cheap lines like Harbor Freights Bauer line and with better pro and pro-sumer cordless tools like Milwaukee and DeWalt. If you follow the YouTube channel "The Torque Test Channel" they mirror this result with more subjective data across a range of tools including drills and impact wrenches.

I found in a lot of cordless tools the higher amp hour rated battery the better. Generally I have not noted it for light load tools like a cordless drill using small bits, but things like electric chainsaw, angle grinder, etc it was very noticeable. I do not mean just that the bigger AH rating ran longer. I mean it delivered more current in a short fixed time period. The tool performed better. I've experienced this with relatively cheap lines like Harbor Freights Bauer line and with better pro and pro-sumer cordless tools like Milwaukee and DeWalt. If you follow the YouTube channel "The Torque Test Channel" they mirror this result with more subjective data across a range of tools including drills and impact wrenches.

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Interesting. My high powered tools are corded and I don't have recent experience with new battery tools, or much else that's new, I just prepped a

I think its more likely adjustment of the internal BMS depending on how the larger battery is configured to make it larger. For instance if it has an extra bank of cells it can 100% certainly deliver more current. Just like tying two car batteries in parallel gives you more current capacity. I expect larger cells might also be capable of more current if the conductors are sized accordingly.

I should note that there have been reports of some tools being smoked by running harder with the uber battery packs like the DeWalt 20/60 that delivers 20V and lots of capacity or 60V and less capacity depending on what tool its plugged in to.

I think its more likely adjustment of the internal BMS depending on how the larger battery is configured to make it larger. For instance if it has an extra bank of cells it can 100% certainly deliver more current. Just like tying two car batteries in parallel gives you more current capacity. I expect larger cells might also be capable of more current if the conductors are sized accordingly. Bob La Londe CNC Molds N Stuff

------------------------------------- Beyond the BMS limits, the capacity and internal resistance depend on details of the chemical formulation and physical structure, such as particle size, which may be trade secrets. I've read that they can be traded off depending on the intended load current, higher resistance for greater capacity and vice versa.

"XR" "XR 4Ah"

The 5Ah battery is physically bigger. So likely has the same "duty severity" as an other Ah size in the range? Anyway, I will take that bit that I might have made the better choice getting the 4Ah battery :-)

So yes, as replied previously, these are DeWAlt XR 18V 4Ah batteries

Just as a bit of perspective - having been using these batteries in the DeWalt DCH263

One intention being worked here in Cornwall is quarrying for lithium minerals... Some of the granites have lithium-mica. To make batteries...

Hi all Thanks for comment. At the time I needed it there were only 4Ah batteries in stock, and I got what I got.

I must be doing something right, because I got into the meet/introduce/interview event of a local mine which is re-opening.

For light tools 4Ah is fine and I now have two. If I do lot-lot-lot of bigger drilling, might stock-up on higher Ah batteries. Come that time there could be some "new" battery I am glad it is my option to get.

Comment / reminder - I got the biggest drill using "small tool" batteries.