eos 300 battery problem

Hi there
Have a trouble with eos 300. When I try to shoot with EF 28-90 4-5.6 it shows that the battery is low (even with fresh battery) and doesn't work. However with 50mm af everything is just fine. Unfortunately I can't try this lens on other cameras.

Maybe someone had the same problem and knows how to solve it?

Remove the lens from the camera body.
Look at the electrical contacts, they should be shinny, straight, and at the same height.
Look at the corresponding electrical contacts on a working lens.
Compare the working lens contacts to the malfunctioning zoom lens. Are the contacts identical? Yes-defective lens electronics. No-repair bent contacts, remove burs between contacts.
Lens may be shorted internally, have it repaired or purchase another one.

As said above, make sure the contacts on the problem lens are clean. Use a rubber eraser to clean the contacts if they show corrosion or such. In the end if it works with one lens and not this one then the lens could just be shorted internally. You can get another 28-90 for peanuts on ebay so I woudn't cry too hard if you have to throw it away. If you can find another camera to try it that would be even better.