battery booster idea

[shokjok]

I am designing a new method of boosting weak car batteries. My plans are to use a two-wheel dolly trimmed down to carry a two-stroke engine, belt-driven alternator, voltage regulator, spring coil load and booster cables. In theory, connecting the cables to the battery and cranking the engine should substitute the vehicle recharging system. I have to get a suitable engine before I build this unit. I'll be using loose Ford Motorcraft parts from a scrapped Econoline van, the coil from a battery tester. Once I know the engine rpm I can get a suitable pulley on the engine shaft. there will be several issues to address, including running the engine with the cables clamped to the frame and some sort of a kill switch if things get scary.

 

[tcmtech]

Countless others have built similar devices so its not all that big of deal.

Most alternators are rated for full output at around 3600 RPM or higher and handle up to around 18 - 20K RPM which means if you have a two stroke engine capable of that minimum RPM or higher, which most small ones are, you can set it up as a direct drive with a simple shaft coupler system.

As far as engine choices go I would go for a larger string trimmer, leaf blower, or chain saw engine. All are easy to find cheap at garage sales and will have enough power (2 -3 Hp) to run a stock 60 - 100 amp alternator at a reasonable charging rate as well.

As far as the load bank coil I don't see why exactly you need it. If the vehicle does not crank over fast enough then obviously it has a weak battery, bad cable, or bad starter and that can easily be determined by a simple volt meter and ammeter built into your machine.

If the volts are up and the amps are low the battery is as charged as it is going to get. From there if the voltage drops way down while attempting to start the engine its pretty clear the battery is junk. If it doesn't then it's either a bad cable connection or a bad starter

One thing I would be tempted to add is a peak voltage adjustment to get the peak charging voltage over the stock 14.4 or so volts typical alternators put out. Most bigger battery chargers with a high boost mode, 100+ amps cranking mode, will put out around 16 - 17 volts in that high charge range.

Just my thoughts.