We do it for fun, just bk quarantine.
5.7.4 Water pump for kayak.
If we return to the topic of our conversation, then on the one hand there is a pump / DC motor that consumes 12 Volts, 2.5 Amperes, on the other hand, we decided that to feed this pump from a lead acid battery is not right. Too heavy and not reliable.
If we return to the topic of our conversation, then on the one hand there is a pump / DC motor that consumes 12 Volts, 2.5 Amperes, on the other hand, we decided that to feed this pump from a lead acid battery is not right. Too heavy and not reliable.
Lithium batteries are significantly lighter. Widely used, and inexpensive, the 18650 is very suitable for this. The first circuit that will work. SW is a magnetic switch or 'reed switch', VT - Hi Power MOSFET from any motherboard.
The first annoying problem is that even good rechargeable batteries, as Panasonic or so, with 2.5A current will heat up quickly. And we know how to solve it.
I am not a 'big fan' of connecting batteries in parallel (because a bad battery always wins), but besides this, everything looks good here. We can expect that the 'battery pack' temperature will be at the level of the temperature of the laptop battery.
Another small problem that needs to be solved. In a good case, a our pack of lithium batteries will provide 11.1 volts, minus losses on wires / transistor. This means that we will never reach 12 volts on water pump terminals.
The last, a 'straight a head' solution is probably logical, but constant over-voltage leaves no chance, to a water pump, for reliable life.
One of the ideas that makes this project come to life is PWM. A simple multi-vibrator or 555 timer can do this. This requires minor changes to the last schematic diagram.
As a source of PWM, I like to use a multi-vibrator on conventional transistors. The biggest advantage is that it is predictable and always works.
One variable resistor (VR1) converts this circuit into a variable PWM. Two white LEDs (D1,2) with R5 stabilize supply voltage (as +5V regulator).
Finally, if we put everything together.
Almost the same design drives a high voltage transformer (which was removed from an old TV) in my air ionizer. It works better than I expected. The only difference is the output transistor. I have a high voltage MOSFET installed and on its drain the voltage jumps to 400V.
PS. With an average current of 1 Amp, the output transistor (Q4) operates without a heat sink.
It is it.