Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
10-14-2011, 04:56 AM   #1
pete-tarmigan's Avatar

Join Date: Apr 2009
Location: Conception Bay South, New-fun-land
Photos: Gallery
Posts: 1,266
Load-testing Batteries

Does anyone know how to load-test D-SLR batteries? That is, how can I quickly determine whether a battery will hold its charge for a long time or become exhausted quickly. I have two Li-90 batteries and want to figure out which lasts longer.

10-14-2011, 11:02 AM   #2
Veteran Member

Join Date: Mar 2011
Location: Eastern Kentucky
Posts: 416
Load testing may not give you a time frame just the voltage under load,probably not worth the effort to set up.
10-14-2011, 01:27 PM   #3
noblepa's Avatar

Join Date: Sep 2007
Location: Bay Village, Ohio USA
Posts: 1,139
I'm not an electrical engineer, so take this with a big grain of salt.

It would be fairly easy to rig up something with a resistor and an ammeter in series with the battery. I calculate that a 100 ohm, 1/2 watt resistor would result in a current flow of less than 100 milliamps, which should be safe. Just connect the battery, resistor and ammeter (not voltmeter) in series and monitor it to see when the current flow begins to drop off.

If my calculations are correct, a fully charged battery should last around 15-18 hours at 100 milliamps. This is long enough to allow a fairly accurate measurement.

What I'm not sure of is whether there would be any significant heat buildup in the battery under long-term constant current flow conditions. Even though the current flow would be small, these batteries aren't designed for a constant load. Even with constant shooting, the battery is drained in spurts, such as shutter actuation and flash charging. In between, the battery has time to cool.

Also, because this sort of test does not simulate actual shooting conditions, the results might not reflect real-world performance.

BTW, the formula is: e = ir, where e is the voltage of the fully charged battery, i is the current in amps. Pick a value for i that is safe (keep it under 500 milliamps or .5 amp). Solve for r and that's your resistance in ohms.
10-15-2011, 06:39 AM   #4
pete-tarmigan's Avatar

Join Date: Apr 2009
Location: Conception Bay South, New-fun-land
Photos: Gallery
Posts: 1,266
Original Poster
Thanks for the advice. I guess there isn't an off-the-shelf device designed specifically for load-testing those kinds of batteries. I got the idea from the practice of automobile mechanics of load-testing automobile batteries when a customer brings a car in with a battery that has gone dead.

10-15-2011, 09:49 PM   #5
noblepa's Avatar

Join Date: Sep 2007
Location: Bay Village, Ohio USA
Posts: 1,139
I don't know of any off-the-shelf device to load test small batteries of any kind. There may be such devices for professional engineers, but it would probably be expensive.

Such a test would be interesting, from a scientific viewpoint, but I don't think it would make much difference in the real world. Load testing auto batteries is done, not to measure the life of a charge, but to determine if the battery can deliver the current needed. The starter motor on a V-8 can draw several hundred amps, even in good weather. In cold weather, it can climb. Lead-acid car batteries also drop in voltage quite a bit during cranking. Batteries, like any other electrical component, have internal resistance. A bad battery may show a full charge with no load, but drop to almost zero volts under load. A good battery should drop to about eight to ten volts during cranking. A fully charged battery should measure 13-14 volts, with no load.

I suspect that any difference you find between your batteries would not be that significant. I have a genuine Pentax battery for my K10D, plus a couple of third-party ones I bought for cheap on eBay. I haven't noticed any significant difference. I suggest that you just shoot with them and, as long as you're not running out of juice at a critical moment, forget about it.
10-16-2011, 02:12 PM   #6
Veteran Member
Ex Finn.'s Avatar

Join Date: Nov 2007
Location: Southern Maryland. Espoo. Kouvola.
Photos: Gallery | Albums
Posts: 7,926
Load testing lead-acids is fairly straight forward, testing lithium's is a different matter. Unless you are looking for fireworks.
Any doubts about the batteries, just get new ones, cheaper and safer on the long run.
My 2c worth.

Last edited by Ex Finn.; 10-16-2011 at 03:35 PM.

  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
batteries, camera, dslr, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Question. Silkypix software won't load. granitic Digital Processing, Software, and Printing 2 03-02-2011 07:46 PM
Macro In Flight with a Load eaglem Post Your Photos! 12 12-28-2010 03:20 AM
Kx software won't load adwb Troubleshooting and Beginner Help 4 11-05-2010 12:06 PM
Macro Carrying a Load eaglem Post Your Photos! 2 06-05-2010 12:59 AM

All times are GMT -7. The time now is 10:56 PM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]