electric car jack question?

Question

I want to use a car jack as a tipping mechanism for a wheel barrow. A basic electric carjack can handle a loading capacity of 1000kg(motor 12V,max current 10A). My problem is how do i provide a power source which can handle a load of 100kg rather than 1000kg. Is it just plain simple that i provide 1/10 of the current max current.

Answer 1

The car jack in question has the capability of 1000kg. If you desire to only have 100kg in your wheelbarrow at any time, then the jack will only be working at 1/10th capacity. There's nothing wrong about over-engineering a design such as this. Additionally, the current draw by the motor will be less than ten amps due to the motor not working at full capacity. If you were to get a power supply capable of providing 5 amps, that would be more than ample for your needs.
As for power supplies, you can go with a transformer from AC house current to DC capable of 5A, but you probably don't want an extension cord hooked to your wheelbarrow. I would personally get a sealed car battery and mount it beneath the wheelbarrow as close to the pivot point (axle) as possible as your rechargable power source. Mounting the battery there would minimize the noticed weight of the battery.
Hope this helps.

Answer 2

You provide the same car battery to the electric jack. The motor in the jack will only *draw* the current that it needs to operate. If it is jacking up 1000 kg, then it will draw 10A. If if is jacking up 100 kg, it will only draw the necessary current (approximately 1/10th -- plus a little more for base friction and other inefficiencies).

OR, if the motor is a constant speed type (instead of a constant torque), the 100 kg load will simply be jacked up faster (than a heavier load). If you want it to go slower, you could lower the voltage (6 V motorcycle battery).

Answer 3

Unfortunately, the motor doesn't work that way. You can cut down the current by cutting down the voltage. But a slow moving high capacity motor is not usually going to use 1/10 the amps for 1/10 the load. It is likely to use more like 1/2 the amps. And if it stalls, it will still draw amps while heating up.
One solution to your problem might be to use a 6 volt lead acid battery which can deliver high amps safely.