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This is my homebuilt EV
Running on total of 7 12v Lead-Acid batteries
With nominal voltage of 84 volts
Initially used Schumacher off-the shelf chargers
One per battery
But moving to self made CV-chargers
Testing showed almost no difference in range.
Between SMART and CV overnight charge
I used scrapped 8A Laptop power supplies
Nominal voltage is 16.6v,
Using primitive way to drop voltage – run thru Diodes
To achieve 14.4v output voltage.
Charging requires no control, and provides full charge overnight.
Monitoring block of individual voltages
4 batts are connected to CV chargers,
and 1 is in float mode on smart charger
When voltage reached above 14v – means batteries are full.
Batteries won’t overcharge.
Equalization will be done manually once in a month or so
6th volt meter is dead :(
My new dash board
Top scale shows current in Amps, lower shows total voltage.
1A shows is going to contactor
That plugs the 7th battery in. There is a trick.
Trick is
Motor controller is only designed for nominal 72v (6 batts), but will work up to 90v
Because immediately after charge voltage of 6 batts will rise to near 90v.
However, after surface charge is gone - even 7 batteries will stay below 90v. If 90v exceeded - controller will go in self-protect mode.
That is why I use remotely controlled contactor to temporarily remove 7th battery from link.
Only 1 minute drive is needed to remove surface charge voltage,
and then I will reconnect 7th battery back for maximum performance.
Dring with 7 batteries is noticably faster..
For car heating in winter I have installed ceramic heater core in place of water core.
This is control knobs from original heater. I can select power level and temperature.
Hot air is delivered thru standard car's system.
Heater is capable of running on both batteries voltage and 110v AC voltage. Thermostat allows to keep car warm when car is plugged in.
To avoid wasting heat, I use household timer, which I manually program to start heating 30 minutes before I plan to finish work
During driving, DPDT relay reconnects heater to battery voltage.
For short rides I don't use batteries for heat, as car stays warm, with enough heat left over in ventilation.
Heater draws about 10 Amps from batteries. But in Oregon I only need it during the coldest 2 months. Other fall/spring time it's enough to warm up car while it's plugged in.
I didn't buy enough batteries to support full-time heat.
Motor came from 1978 Hyster 48v forklift, and manufactured in England.
Paid $100 for motor and some cables, while new similar motor is $1300 and up.
Motor is designed for 48V continious operation, but runs great on 84v nominal, with almost no heat up.
I use Alltrax 4572 controller. They are available used, got mine for $210 from Ebay. It is designed to use in high-performance Golf-cart.
Nominal voltage is 72v, but works up to 90v, and I was happy to use this feature.
Additional batteries (#5-7) and trick-contactor are located in back compartment under cover.
Contactor is normally open, not connecting 7th battery for safety reason.
Back compartment was widened to fit up to 4 12v batteries.
Suspension was not modified, and still handles OK. But I can feel speedbumps with my butt, so it's on the edge.
Here is a set of diodes, which help to lower the voltage. Bolted to adapter plate, to dissipate the heat.
Not the most effective, but absolutely simple and reliable charger
Adapter plate and adapter itself made by myself on milling machine. Bolted to manual 5 speed transmission that came with car.
Transmission is original 1985 with 160000 miles. Still works ok.
All 12v car components (light, turn signals, music and seat heat) are powered by 12v aux battery, in it's original place
Battery is charged every time car is plugged in, and is enough at day-time use.
For night time I have another IBM power supply, that is powered by DC voltage, and produces up to 8A at up to 16v to help battery.
That power supply is just the right size to have enough 12v power for all car coponents when headlights are on.
Purpose built DC-DC converters are $300 and up. Mine is FREE :)
AUX battery is charged using the same method as tracktion pack - with IBM power supply thru 3 Diodes, bolted to heatsink on chassis to dissipate heat.
Diodes and heatsinks came from scrapped desktop PSUs, and are also FREE. On video I still have SMART chargers working to compare effectiveness, and so far I don't see any difference in overnight charging.
DC shunt, rated at 500A. Used by Ampmeter to control DC Current.
Ofcourse you can't route 100-200A thru amp meter itself.
Batteries I used - 125AH Marine deep cycle batteries from WallMart, $85 each.
Regular starting batteries aren't bulit to work in EV due to deep and long discharge. But I decided not to buy real deep cycle (i.e. Trojans) due to it's high cost.
Emergency cut-off switch, in case things go wrong when I'm workign under the hood.
All inter-battery connections are flattenned copper water pipes.
Power meter - tells me current AC amps, Watts, and total Watt*Hours for the charge.
This costs $20 new for standard 110v AC. Similar model for DC usage, to monitor car's performance is $300+
But, Hey, this is an experiment only:) I'll save my money to buy Aptera!
Most components are used. Car itself was another $300.
And this is the biggest good thing about this car - it was only $1000 to convert!
LETS GO TAKE A RIDE!