Bob's Homemade Battery
"Make-A-Volt” Model 5-12,
Serial # HM-2
following project and article were constructed by my good friend Bob
"KC9BUZ". For the time being, questions and comments can be sent to me, and I will forward them to Bob.
I built this charger in the spring of 2005.
It was based of a similar charger that I saw in the early 1980s at
Nevin Park Raceway in Corydon, Indiana. I had seen some plans for
similar units on the Internet. I started to seriously research this
project in February and began to collect parts. The engine was given to
me this spring, it had been removed from a broken garden tiller. It is
a 5 H.P. Briggs & Stratton.
The first thing
that I did was to mount the engine on a wood pallet and get it
running. It had a broken flywheel key and needed a set of points.
Some tinkering, a bit of online reading, and a couple of trips to the
hardware store had it running fairly well a few days later. A trip to
the junkyard produced an alternator from an old Chevy. I bought a 5"
diameter pulley at the local farm supply store.
I wanted to make
sure the machine would work before I spent much time or money on it.
Now it was time to mount the engine and alternator to the pallet and
rig up a drive belt. I sawed up some more pallets for some lumber and
made some rough mountings from scrap metal. And old power steering belt
from my truck coupled it all together, After things were fastened down,
I wired the alternator using scrap wire and a headlight switch from a
Dodge van. And old battery was attach to the contraption for the test
run. Above photo: Everything it put together and ready for a test run.
All of this hardware was quite a sight. I checked
the belt alignment and tension, it was time to try the thing out. I
pulled the starter rope, the engine flooded and needed a shot of
starting fluid to get it going. After it warmed up a minuet, I turned
the switch on. The engine sound changed and the thing was producing
electricity! The engine had a burned out muffler and was very loud
under load. I was surprised that it worked the first time. I had to
brace the belt tensioner and generally tighten things up to get
everything to run true. The machine was made of junk, but it worked. I
ran the machine in this state for around a total of ten hours over a
few days using it to power inverters and charge a battery.
The engine turns
at aprx. 3100 R.P.M. at full throttle and it will charge at idle speed
with reduced current. The alternator turns at about 5000 R.P.M. at full
throttle. The 5" pulley gives nearly 50% overdrive to the alternator.
The wooden test mounting really saved a lot of work as I could easily
change things as needed. I experimented with pulley size and control
circuits until things were ready to make more permanent. After some
more testing, I decided to make a real project out of it. The rig
looked like something from the "Green Acres" television show, but it
and Different Uses
The machine is
labeled " Make-A-Volt" Model 5-12, Serial #HM-2. This represents 5
H.P., 12 volts, home made #2. H.M.-1 was a deep cycle group 27 battery
mounted with a 300 watt inverter that was built in 1999. It has worked
well for a variety of tasks and is still in use. Machine H.M.-3 is in
the planning stage now. Below Photo: The name plate.
What is it good for? I built it to do
several jobs. It can jump start a vehicle with it's on board battery,
and or supply 12 volt power to an inverter to operate power tools and
lights. The unit has powered my electric drills, grinder, sawzall, and
rechargers for cordless tools, It does an excellent job of powering my
ham radio equipment as the battery will last several hours and a short
engine run will recharge it with minimal noise and fuel consumption.
The machine does best as a charger. I ran a test by
powering two 13 watt fluorescent trouble lights from an inverter for 25
hours. A twelve inch B.& W. TV was added for another two hours.
When the inverter alarmed on low voltage, I ran the engine for about an
hour to fully recharge. This took around two quarts of gas. This is
much better fuel economy that a conventional generator that would have
burned almost 15 gallons to run this small load for the same time.
Speaking from experience, listening to a generator run all day gets old
quickly after a while on a job site or during a five day power outage.