Jobsite Battery Charging with the Dewalt DCB104

Tue Jun 29 2021

An in-depth review of how to use the Dewalt DCB104 4-port battery charger to keep your cordless power tools working all day long.

Jobsite Battery Charging with the Dewalt DCB104
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Our new property has electric at the road, but our actual build site is about 1,000ft further back along an old logging trail - far too long for an extension cord!

Clearing the Road

The land is ours and now the hard work starts. Our first project is to clear a road so that we can drive our truck onto the property.

Clearing the Road

Before we can pull power up to the house site, we need to clear some trees and build a mechanical shed where we will be terminating all our utilities - including electricity. But getting to that point needs power tools - a chainsaw, circular saw, drill, etc.

Conventionally, there have been several ways to brake this deadlock:

  1. Pull in temporary power
  2. Use a generator

Given the distance from the road, pulling in temporary power isn't a viable option for us until we have the driveway in place. And after full-time RVing for 3 years without a generator, we weren't keen to start using one now - they're heavy and noisy and need regular maintenance!

Modern cordless tools now offer an alternative, and that's the route we've decided to take - at least for the time being!

Dewalt Flexvolt Cordless Tools

As we embark on this house build, we're going to be acquiring a wide selection of tools across all types of work - land clearing, framing, plumbing, electrical, etc.

We were drawn to the Dewalt ecosystem because aside from their broad range of quality tools, their battery system sets them apart from the competition. Cordless tools have traditionally been confined to lower voltage (and hence lower power) than their corded counterparts - handheld drills, sanders, etc.

But with the release of their Flexvolt battery system in 2016, Dewalt have really shaken things up.

The uniqueness of the Flexvolt system is that compatible batteries can operate at two different voltages - either 20V or 60V depending on the tool they're plugged into. This means that a Flexvolt battery is capable of running your existing 20V drill or driver, but can then be connected to a chainsaw, SDS Max drill, and even a table saw! Using two batteries you can even run a double bevel compound miter saw!

Dewalt DCCS670 Chainsaw
The Dewalt Flexvolt chainsaw is much more powerful than its 20V predecessor.

These Flexvolt batteries are compatible not just with 20V tools, but also with 20V chargers, meaning no additional investment is necessary for more chargers. For us, building a collection of 20V and Flexvolt batteries knowing that they will allow us to power more than 200+ tools in Dewalt's catalog gives us a lot of flexibility.

Dewalt Flexvolt Batteries

The biggest complaint we heard about cordless tools is their battery life. Particularly on the more powerful tools, you'll find yourself getting through batteries pretty quickly!

To assauge these fears, Dewalt offers a range of battery sizes, although it's worth taking a minute to talk about these capacity ratings.

Before the advent of Flexvolt batteries, understanding battery capacity was simple. Batteries would be rated in Amp-hours (Ah), for example 1.5Ah or 3Ah - a 3Ah battery delivering twice the usable capacity of the 1.5Ah model.

But with the Flexvolt batteries, it's a little more complex since the current rating depends on the voltage the battery is being used at. For example, a particular battery might have a capacity of 2Ah when used in a 60V Flexvolt tool but a 6Ah capacity when used in a 20V tool.

That's because the energy capacity of the battery (measured in Watt-hours, or Wh) is always the same. We calculate Watt-hours as Voltage x Amp-hours. So with our sample battery from above, 20V x 6Ah is the same as 60V x 2Ah - either way the battery stores 120Wh of energy.

To simplify things, Dewalt typically always rates the battery using its 20V capacity - e.g. a 6Ah Flexvolt battery is really 6Ah @ 20V (120Wh) and not 6Ah @ 60V (360Wh).

There is one exception to this rule - batteries in Flexvolt tool bundles. I've noticed that oftentimes, when I look at Flexvolt product listings on online retailers (e.g. Home Depot), if the tool is a Flexvolt tool and comes with a Flexvolt battery, its capacity will be listed at its 60V rating. For example, when we bought our chainsaw, it came with a Flexvolt battery rated at 2Ah but but this was really 2Ah @ 60V (120Ah) and not 2Ah @ 20V (40Ah).

This confused me enough to almost avoid buying the tool as I thought it was a laughably small battery for the chainsaw. But I understand why they do it - in this case, the battery is rated using the voltage it will be used at in the tool you're buying. One to watch for.

Pro Tip: Shop around when looking for batteries. The best deals can sometimes be found in bundles, sometimes in standalone batteries, and sometimes in combo packs. Also check mulitple retailers for special offers and deals!

To kick-start our collection of tools and batteries we bought a 2-pack of 6Ah Flexvolt batteries, the Dewalt DCCS670 Flexvolt Chainsaw that came with another 6Ah Flexvolt battery (although it was described as a 2Ah battery on the product listing) and a Dewalt DCPS620 Pole Saw which runs at 20V but can use the Flexvolt batteries.

Dewalt DCB104 4-Port Simultaneous Charger

The next question is how to charge these batteries. Our chainsaw came with a battery charger but it only charges at 1.5A - in other words, it'd take around 4 hours to charge just one 6Ah battery! We needed an upgrade.

We decided to buy the Dewalt DCB104 battery charger which can charge 4 batteries all at the same time and unlike some others, charges just as fast whether you're charging 1 or 4 batteries. Better yet, it charges at a staggeringly fast speed of up to 8A (@ 20V) per battery!

Regardless of whether you have 20V batteries or the Flexvolt batteries, they always charge at around 20V. Charging slows down as the battery nears full charge, but this charger is still capable of charging one (or up to four!) 6Ah batteries in under an hour.

DCB104 Power Consumption
Measuring the power consumption of the DCB104 while charging a single 6Ah Flexvolt battery - the y-axis shows Watts as measured at the plug.

This chart was taken for a 6Ah Flexvolt battery that I had used until the chainsaw wouldn't run any more. There may have been a little more energy left that a 20V tool such as a drill could have eked out, but for all intents and purposes the battery was dead.

The chart above shows the power consumption of the DCB104 as measured at the plug (i.e. at 120V AC). You can see the power consumption rise steadily around from around 160W to 189W after 42 minutes - this is the bulk charge phase of the battery, charging at around 8A. It then steps down at what roughly equates to 6A, 4A and 2A of charging for periods of 3-4 minutes until the battery is fully charged.

In total, the battery took about 52 minutes to fully charge. The charger consumed a total of 134Wh which, if we assume the battery was completed depleted, would equate to an efficiency of ~90%.

DCB104 Energy Consumption
This chart shows energy (measured in Watt-hours, or Wh) consumed over time. The battery has a rated capacity of 120Wh and the charger consumed 134Wh to fully charge the battery.

For us, this means we can plug in our three 6Ah Flexvolt batteries at once and have them all charged in an hour. So we can charge them at home, then take them to the jobsite ready to go.

When charging multiple batteries (two 6Ah batteries in this chart), the power consumption of the DCB104 is doubled (y-axis shows power in Watts) - the batteries are charged independently of one another.

Battery + Inverter Charging

From our experience so far, the chainsaw lasts about an hour of regular usage, although that's been as low as 30 minutes during an almost non-stop limbing session!

With our three batteries, this realistically means we can run the chainsaw for about 3 hours. Not bad, but not exactly a full day of use.

Game of Logging: Chainsaw Training

This week I attended a Game of Logging training course by Northeast Woodland Training to learn the basics of safe chainsaw operation and tree felling.

Game of Logging: Chainsaw Training

As full-time RVers, we're used to working off-grid, and one item we carry around is a backup battery pack. It's actually an Inergy Kodiak Solar Generator that a friend gave to us when the inverter inside died - I ripped out the inverter components and it now functions as an easily rechargeable 12V battery.

Theoretically when new it had a capacity of around 1,100Wh (90Ah @ 12.6V), or the equivalent of about 9 of our Flexvolt batteries. An alternative would be something like a Bluetti AC200P Power Station.

We also carry a 500W pure sine wave inverter that we bought to charge our video editing laptop in the truck (its 230W power supply seemed to overwhelm our truck's built-in inverter).

Dewalt DCB104 Charger
Powering the Dewalt DCB104 4-port charger using a 12V power station and 500W inverter.

Using the 12V battery and 500W inverter we can power the DCB104 in the field. Even accounting for the inverter losses and reduced capacity of the battery due to age, it should still have enough capacity to charge 3-5 Flexvolt batteries, extending our working time to a full day. We've not tried charging all three batteries at once, but that's likely pushing the limits of our inverter.

We can always buy additional batteries (as I'm sure we'll end up doing as we acquire more tools anyway), each one extending our working time by about another hour.

For now, each time one of our batteries is depleted we plug it into the charger and swap in a new battery. Using this approach, we've not yet run out of charged batteries while working on site.

Obviously if you have a bigger crew or are using multiple high power tools simultaneously then you might need a different solution - perhaps a small generator or temporary power hook-up connected to a couple of Dewalt DCB104 chargers for example.

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