Topic: converting 4 WD car to hybrid electric car

[piersdad]

Hybrid electric cars.

In today’s oil crisis the hybrid car will be the best bet to keep your travel costs down.
The conversion of a 4 wheel drive car to hybrid is the easiest and best solution for the DIY person.
I don’t mean the 4000 cc 3 ton ones they will still cost you a fortune to run.
The ideal car is the small 600 cc to  1500 cc  4wheel drive.
An example of this was the Suzuki alto I had to work on.
It had front wheel drive and a clear drive shaft to the rear axel.
This drive shaft has only to be removed and an electric drive attached to the rear diff.
This then still leaves it as a 4 wheel drive except the rear wheels are driven by electric motor.
The Nissan ‘cube’ has a 4 wheel drive exactly like this but the motor is more like a small starter motor and not really for highway use just to get you out of the mud drive.

The best motor to use for a conversion is the motors used for forklift hydraulic pumps as they are series wound and will act as a generator if a pair of the series  windings are replaced with shunt field windings making it a compound motor .
This means if you are going down hill you can use the rear driven motor as an electrical brake and the batteries will be charged as you descend
Also if drifting into a set of lights the electric drive will slow you and give the batteries a little boost.
Complicated electronics are not needed as with just two different throttles  you can use your judgment and foot to get the best drive for the circumstances.
For example taking off from home use the electrical drive and as you get to the main highway then use just the petrol motor where it is best for efficiency.
Any slow down needed such as intersections a quick blip on the electrical drive will slow the  car down a bit charging the battery as you do.
Taking off from thee same place can be also on electrics till the petrol motor is needed.
Of course if you are in a slow build up of traffic your electrics will really come into efficient drive and as they are super silent I can tell you from personal experience it is rather soothing in a frustrating situation.

As each car is different I can not really give details of a conversion.
Basically the rear diff is electrically powered and the rear seats removed and a strong frame for the batteries placed in their place.
Certification of this in New Zealand  will cost a bit as this can weaken the car.
So light weight batteries are needed.
Possibly no more that a ¼ the weight of the car,

In the hybrid I built in 1979 I used a special space frame sports car and with a V W rear diff I put an electric motor on the front of the gearbox welding an extension to the main gear shaft to protrude out of the gearbox.
It worked but not very strong

One of the other advantages of the hybrid is that it does not attract road user chargers as would a diesel or pure electric car

phone for further discussion is  03 9814888

[piersdad]

this is a letter i replied to helping a friend to convert a 4wd to hybrid

Fist of all thanks for you reply to my email.  As i said before the proposed car would be either Mira hatch 4 wheel drive 650kg or a Suzuki Alto hatch 4 wheel drvie 740kg.  I propose at this stage to shorten the drive shaft to the rear wheels and place the motor at the front of this drive shaft.  This would give me the diff gearing to the rear wheels,  Most diffs are a reduction of 3.5 to 1  to  4.0 to 1.  I note that my corolla does 1900 rpm at 50kmh in top gear.  Now an update on the motors. The 48 volt 5.5kw pump motor is definitely a series wound motor (not a shunt as i originally thought) Its rpm is a bit uncertain as it is not given is the service manual but i am told by the forklift people that its probably in the range of 2500-3500 rpm.
It has an internal fan for cooling.  I placed it on bathroom scales and it weight is approx 37kg cost $100.  The premanent magnet motor as given on the motor plate is 36 volt dc 59amp 2.25hp 2500rpm.  The second hand machinery place has 2 of these motors they are $180 plus gst each.  In round figures $200 each.
Now battery weight a 12 volt 60 amp deep cycle battery is 16kg, cost $190.
A 12 volt 105 amp dcb is 25kg $295 and 12 volt 120amp dcb is 28kg cost $320.
These batteries are the flooded and vented type.
As you can see they are not cheap?
The maximum discharge would be 75%
Question- could i get away with a standard heavy duty battery if discharge were kept at less than 50%?
Thanks again for anticipated reply.
 ----
 
If the motor on the diff is directly coupled then it will be revving a lot more than its designed speed if the petrol motor and car exceeds 90 km ph

Options are.
Use the pump motor direct coupled this will give you a plug and drive hybrid where all the batteries are charged at home.
And at 3500 you will be at near the max revs at 90 km/h

If you are to remove one of the pair of series windings in the stator(outside) and replace them with a shunt winding you will have a compound motor.

I can help you with the calcs for the voltage /turns/wire size here (just give me the dimensions of the metal pole and space  available around it)

With the shunt winding in place then any over speed or slowing down can be controlled  by dynamic braking
With series only the current in the series fields reduces as the motor tries to charge the batteries and thus can not charge at all. The shunt windings remain energised and enable braking when over speed for the voltage  of the batteries.
.

A 12 volt 105 amp dcb is 25kg $295 and 12 volt 120amp dcb is 28kg cost $320.
These batteries are the flooded and vented type.

Deep cycle batteries usually are rated at 5 hours discharge rate and have a life of 400 to 500  full discharges
So 3 batteries 120 amp(go for the largest +$25 extra)  cost $ 1280
And say 500 discharges before power falls off= $2.56 per discharge
 (put this into an auto savings account depending on average use per week)

28x4 =112 kg  (=one large passenger in rear  no trouble from certification)

I would expect the pump motor will be at max current of 100 + amps and this will give you about 50%  of the batteries capacity of 120 ah (about ½ hr full on 25 km) but with frequent small charges from braking etc the range  will be greater  but don’t expect  too much from the batteries.

The amp hour capacity drops dramatically as the current goes up
Ie at 1 hour discharge  with say a 5 hour rated amp hr battery the output is aprox 75% or less.

I once tried out regenerative braking and its effect on the batteries.
So I went up and down a reasonable hill and after I was expecting the batteries to die I got some 40% more energy
( BUT the acid in the batteries was just about water they were so flat)

Having some sort of direct clutch (dog sort) on the electric motor coupling would be a good idea so that if you want to drive at 100 kmph some where you can go on just petrol and not have the electric motor revving and dragging power from the petrol motor

I will be going to a lecture  on the 16 august and it seems to be popular as my ticket no is 82
I feel there may be the start of a club here will keep you posted.