How can I convert 18v cordless drill battery to recharge laptop, compact camera?

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Discussion Overview

The discussion revolves around the feasibility of using 18V cordless drill battery packs to recharge a laptop and a compact camera during a week-long backpacking trip. Participants explore the technical aspects of battery capacity, efficiency, and alternative solutions for charging devices in a remote setting.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires whether it is possible to use 18V drill batteries to recharge a laptop and camera, providing details about the battery specifications and intended use during a trip.
  • Another participant points out the laptop's input specifications, noting the need for a compatible charging solution.
  • A participant suggests that purchasing additional laptop batteries may be more practical than attempting to build a charge controller, citing cost and complexity.
  • In response, another participant highlights the high cost of laptop batteries in their region, arguing that buying multiple batteries is not a feasible solution given their budget constraints.
  • One participant calculates the potential efficiency of transferring charge from the drill batteries to the laptop battery, estimating that under optimal conditions, the laptop could be charged to around 40-59.7% capacity.
  • This participant recommends using a car charger for the laptop as a safer and more efficient alternative to building a custom charge controller.
  • Another suggestion involves using deep cycle car or marine batteries with a charger and inverter, proposing a resupply system for charging devices in the field.

Areas of Agreement / Disagreement

Participants express differing views on the practicality of using drill batteries versus purchasing additional batteries or alternative charging solutions. There is no consensus on the best approach, and various options are debated.

Contextual Notes

Participants discuss assumptions regarding battery capacity and efficiency, as well as the potential risks involved in DIY charging solutions. The discussion reflects a range of technical considerations and personal circumstances that influence the feasibility of the proposed solutions.

Who May Find This Useful

This discussion may be useful for individuals interested in portable power solutions for outdoor activities, particularly those facing budget constraints or seeking alternative charging methods for electronic devices in remote locations.

BongEx
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I have 2 rechargeable 18v battery pack from cordless drill which I'm thinking of using as laptop charger and compact camera battery charger. These packs comes with 220v adaptor. Me and my 12yo son will be doing a week-long research for his school project (climate change) this Xmas break, backpacking in a remote island. I was thinking of using this packs to recharge our gears and then send the depleted 18v battery for recharge, and so on. Will this be possible? Thanks everyone for the help.

The link contains picture of the batteries in question.

http://www.flickr.com/photos/13780793@N02/5265695126/
 
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BongEx said:
I have 2 rechargeable 18v battery pack from cordless drill which I'm thinking of using as laptop charger and compact camera battery charger. These packs comes with 220v adaptor. Me and my 12yo son will be doing a week-long research for his school project (climate change) this Xmas break, backpacking in a remote island. I was thinking of using this packs to recharge our gears and then send the depleted 18v battery for recharge, and so on. Will this be possible? Thanks everyone for the help.

The link contains picture of the batteries in question.

http://www.flickr.com/photos/13780793@N02/5265695126/

Welcome to the PF.

What does your laptop specify for its input DC voltage?
 
Hi, I found this in the laptop adaptor:

input: AC 100-240V 1.7A 50-60Hz
output: DC 18.5V 3.5A 65W

Thanks!
 
There are several things to consider, but in the end, you might be better off simply purchasing a couple extra laptop batteries @ $27 each:

http://cgi.ebay.com/Battery-HP-DV4-DV5-HSTNN-CB72-HSTNN-UB72-Laptop-/200502553753?pt=Laptop_Batteries&hash=item2eaee22c99

Designing and building a charge controller is certainly very possible, but the time and cost associate would be extreme compared to the cost of spare laptop batteries. At least from MY perspective,

Fish
 
Hi Fish, Thanks for the suggestion. The cheapest Laptop Battery for HP DV4 DV5 HSTNN-CB72 HSTNN-UB72 is roughly $80 here in the Philippines (Php 3,500) so that would make $160 for 2 items. Though buying lots of extra batteries is the simplest option, cost-wise, it can't be my solution. I still have to deal with cellphones and compact cams batteries. Spending for all these batteries would imply draining our tight budget for our intended trip. It simply don't equate.
 
BongEx,

I assume this is similar to your drill:
http://www.ozito.com.au/productinfo.aspx?prodid=OZLICHD18A
Note the battery spec: 1.3Ah 18V = 23.4Wh
Your Laptop Battery: 4.2Ah 10.8V = 47Wh

Assuming you could transfer the charge from both your drill batteries to your laptop battery with 100% efficiency, AND assuming the Ni-Cad drill batteries are still capable of holding 100% rated capacity, you would be able to charge your laptop battery to 99% once, completely draining both drill batteries. I would doubt that your drill batteries will hold more than 75% of their rated capacity, and you would be lucky to transfer the charge with 80% efficiency (combined battery heat losses & DC to DC charge controller losses), so:

46.8Wh * .75 * .8 = 31.59Wh => 28.08/47 =59.7%

That is, you would, under what I would consider the best of circumstances, be able to charge your laptop to 59.7% using your two drill batteries. More realistically you might expect to charge your laptop battery to 40% to 50% using both drill batteries.

Assuming this is worthwhile, I would suggest you find a "car charger" for your laptop and modify it to connect to your drill batteries. This is far and above the cheapest/safest alternative. Your laptop already has the most efficient charge controller you could hope to find for that battery pack already built into it.

Using the same process for your 3.7V 1.08Ah cell-phone battery:

3.7V * 1.08Ah = 3.996Wh ==> 46.8Wh / 3.996Wh = 11.7 Charges In theory, in reality:
46.8 * .75 * .8 => 28.08 / 3.996 = 7 Charges

Again, I would strongly suggest you simply buy a "Car Charger" designed for the battery you are attempting to charge. While these are not likely to be as efficient as the laptop charger, they are cheap and safe for your intended purpose.

The camera battery is similar to the cell-phone.

While charging batteries is not rocket science, and designing/building DC to DC charge controllers is not a huge undertaking, adequate care needs to be taken to prevent damage to the batteries being charged. This includes fairly intimate knowledge about each battery being charged. Damage may range from shortened battery life to catastrophic failure (Read: Exploding Battery). I would consider the risk/reward ratio of designing and building three charge controllers for 46.8W of power abysmal.

If you purchased a "car charger" for your camera, cell-phone and your laptop and added a 25W solar panel, you could likely keep all three batteries charged with as little as 4 hours of direct sunlight/day. A 25W solar panel in the US ranges from ~$100 to ~$250.

I am sorry if these solutions do not meet your needs/budget, but maintaining high-tech devices in remote locations is generally expensive. Renewable Energy is typically quoted from $4/W to $20/W, but is typically far and away cheaper/more practical than toting generators to remote locations. Purchasing spare batteries for short duration trips vs purchasing and carrying something like a solar panel depends a lot on the trip/location/budget. In any case, I cannot see the 46.8Wh capacity of your two drill batteries doing much more than charging your phone/camera batteries. The laptop will require a more robust solution.

Hope this helps,

Fish
 
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If you have someone coming into resupply you every day (or even every few days) consider getting some deep cycle car / marine batteries, a plug-in car battery charger, and a small inverter that takes in 12 V as input (and, obviously, produces 110 V AC as output). You can just plug in your devices as you normally do.

Your supplier could then drop off the charged batteries while picking up the empty ones. You'll probably need a voltmeter to determine if your batteries are empty (around 10 V as opposed to the 13 they start out at).