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Author Topic: Second life for the Dewalt DE9118 7.2-14.4V Ni-Cd charger  (Read 3372 times)

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Online Kiriakos GR

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Second life for the Dewalt DE9118 7.2-14.4V Ni-Cd charger
« on: July 02, 2020, 11:04:47 AM »
Dewalt DE9118 this is another old generation pulsing charger this be specially designed for Ni-MH & Ni-CD cells.
 
Unfortunately the Chinese Dewalt, does not hold any information's about it on their website.
And this is a great example of how much  the Chinese Dewalt this cares for it past.

I got this charger as half-gift and I say HALF because top cover this were missing.
In my surprise this PCB works.  :)

The Dewalt DE9118 does not include temperature detection for the battery due a sensor.
The charger will start charging immediately when the battery seems to have at least 4V at their poles.

DE9118 DC current specifications this is at 1.3A, when  Ni-MH or Ni-CD cells they are connected to it.
The internal resistance of the battery or battery pack, this is essential for this charger.

In my first test with one 12V 7AH (battery for small UPS) the charger delivered 1.6A
Then I thought that this is too much for a single battery and added and a second one in parallel.

Now the the DC current output become half
, but even so this is correct and upon the electrical specifications of those batteries.  8)

In conclusion the Dewalt DE9118 other than capable charging battery tools packs at 7.2 and 14V this is also capable charging two regular 12V 7AH OR a single 12V 17AH  ;)

True voltage output at charging this is 16.3V
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Online Kiriakos GR

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Re: Second life for the Dewalt DE9118 7.2-14.4V Ni-Cd charger
« Reply #1 on: February 11, 2024, 08:53:36 PM »
DE9118 this was and is Ni-Cd (for Ni-Cad only) exclusive charger, and therefore for the ones not using Ni-Cd cells this is unwanted stock.

At my fresh application, I did a combination of eight still working but aged Ni-Cd.
Sixteen Ni-Cd tested, the best ones are now installed at my second Bosch 9.6V battery pack.

Now I am investigating best method to top-up this battery pack as much as possible.

I did try as first regular pulse charging, due my Bosch charger, but this it did not go that well.
This pulse charger uses regular transformer and pulse circuit, the regular transformer creates a permanent amount of heat, no matter if this is at low current pulsing mode.
Old Ni-Cd they dislike this heat as it grow their own internal resistance and they cannot absorb energy more than up to a point.

Here comes in the game the DE9118 along of one accessory from Bosch, this is the non-smart battery charging port which is for 300mA constant current.
I did use my magic and a third thermistor contact point added and now any fast charger can sense the thermistor and start fast charging by the use of this battery holder. 8)
----------------------------------------------------------------------------------

By having the battery pack away of any heating source, the amount of battery voltage absorption this increased, which is good.

But I thought to elevate my game at an upper level, now I am using for a test,  pulse charge and active battery pack cooling, due external 230V AC Fan (120x120 mm).

By the use of 8846A and logging software, I do now monitor charging voltage absorption, and even discovered all DE9118 secrets.
     
 
DE9118 has non-load voltage output at 49.2V
DE9118 at charging mode deliver 1.4A, and stops charging every 60 seconds so this to measure battery voltage.
When this charger perform three measurement’s in which the voltage now decreases ( due the fact that battery pack cannot absorb the incoming energy and turn itself in to resistor), then the charger switch to low power charging.

When DE9118 this does Low power charging, at every 10 seconds a pulse of 1.4A this delivered at the battery pack.
The amount of energy absorption, this is now relative at actual battery pack internal resistance, along of the room temperature.

Room temperature this is at 17 Celsius at midday and drops at 14C at night.
With active cooling, at 17C the battery pack this maintain external (body) temperature of 21C at slow charge.
My new task this is to monitor battery pack voltage for several hours and even overnight, so to gain awareness if this unusual charging method does offer any benefits in comparison to the ancient of 300mA charging for several hours.

At slow charge with 300mA CC, the battery pack voltage did not succeed to elevate more than 11.482 V overnight.
Currently I am logging voltage spikes, when the pulse strike the pack, the average voltage after the first hour this at 10.882V and I hope to see this increasing within the next 16 hours.
Max spike 11.717V
Average 10.882V
Minimum 10.572 

Now I have to wait for 16 hours so to collect and analyze the data.
Only then a verdict will be possible.
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