120 replies to this topic

[Silicon Skum]

Gota say, I'm a little worried by the lack of direct airflow over that motor! Even with forced cooling, you just going to be recycling the hot air over the motor again.

With a stiff head wind, and a long steep hill......that motor is going to be TOASTY!

Also, why did you mount the motor in that way, couldn't you have turned it around, so that the motor was up against the boot lid - and so no need to cut into the rear bulkhead / seat area? Wouldn't you just need to turn the whole thing 180 degrees around, and run the motor in reverse (with brush adjustments - if using off-set brushes), so the diff still turned in the right direction....??

Cooling would be easier that way too, a ducted fan from below, blowing across motor, and exiting through a vent in the boot lid (would also provide some natural air flow incase of fan failure!).

SS

[brightsparkz]

Hi SS,

Some good points there. I did think about motor cooling, this motor was designed to run 25hp continuous and 100hp peak so if you are running 100hp for more then a few min you will start melting things in the motor. I doubt that I will need 100hp that often so wasn’t so worried about cooling but then I guess going up a long hill could cause things to get hot. remember the motor will get hot at low rpm, i have a feeling with that much power the motor will rarely be at stall. You are more likely to get wheelspin.

I think you will get a fair bit of circulation due to the fact that the boot has been cut out. The sudden change in profile under the car will cause the air to swirl up into the boot area. As long as you have an outlet for this air to escape you will get good circulation in the boot. This will also cause a bit of drag, (so does the rear valance ,basically a air catcher) so will think about other ways to improve air flow. I was thinking about adding side pods like on a mini I’ve seen on the forum somewhere but then the motor will need cooling at low rpm at high speeds when the side pods will be pumping the most air the motor wont need so much cooling.

The way I have it now was the easier option. I did try the way you suggested but I couldn’t get the diff to work. See pic… Just couldn’t get it lined up properly and didn’t want to fork out for a quaife diff. The project just stopped and i just gave up on it. It is the cleanest solution but what i have now will work too.

[Silicon Skum]

Hi SS,

Some good points there. I did think about motor cooling, this motor was designed to run 25hp continuous and 100hp peak so if you are running 100hp for more then a few min you will start melting things in the motor. I doubt that I will need 100hp that often so wasn’t so worried about cooling but then I guess going up a long hill could cause things to get hot. remember the motor will get hot at low rpm, i have a feeling with that much power the motor will rarely be at stall. You are more likely to get wheelspin.

Motor doesn't have to be at stall to build up too much heat - just needs a fairly heavy work load (a car with the areodynamics of a brick and pulling half a ton of lead, perhaps.... ) and little or no airflow, will get the heat into the coils quite quickly. Don't forget, the conditions on the road will change constantly (slow, fast, hills, stop - starts etc), so the power you use will change too. If you don't plan on going faster than 30Mph and avoid hills, then the motor will prolly be fine......if not - I wouldn't take any risks.

Would be best to mount some sort of temperature probe on the motor (could hook it up to the temp guage on the mini dash) with a warning when temp is too high, OR if the controller supports it (or add an extra circuit / module in) - the over temp warning will adjust the PWM of the motor to reduce the amps to protect the windings, and turn on a cooling fan (the fan should be rigged up so that it remains on even if the car is stopped, until the motor has cooled - same as a rad fan). The automatic fan would be good to help cool the motor down once the car has stopped and the motor is already a bit too warm (say at traffic lights after climbing a hill - no air flow....hot motor with no cooling!). Even just using a car radiator fan and bimetalic switch would be enough to protect the motor - cheap to install too.

Better safe than sorry.


Can't wait to see this thing running!

by the way, have you thought of a name for it yet?

SS

[Ethel]

Seems like your project has moved on a bit. Last time I looked you were looking at putting the motor up front and using a propshaft. So ignore my comment about the high diff - I realise the hole is for the motor now!

I see the subframe has slimmed down a bit too. Not sure where the axle would normally sit. A look at a standard Mini's lower shocker bushes should indicate if it's likely to interfere with the floor. Rear coil over wouldn't fit as the driveshaft has taken their location. May be front coilovers would go better as the weight will go up too?

[brightsparkz]

Hi SS,

You are right about the cooling. will look more into it. Regarding temperature gauge, the controller has the facility to monitor temperature and ramp down current if the temp is too high. it also has the ability to limit the rpm. These motors can be over reved and the coms are known to explode. Better order the controller soon, have 6 month lead time!

Ethel,
i know very little about coilovers. My swing arms will have coilover mounts welded on but i'm not sure what length coilover to get. any advice would be appreciated. I can move the suspension turret to accomadate whatever coilover is suitable. I have looked at the standard shock on the rear subframe. would i need a coilover with the same stroke and open length? Need to get a coilover soon!

Have no idea what to call it! too busy trying to figure out how to get it to work!

[Silicon Skum]

These motors can be over reved and the coms are known to explode.

Yep, I've blown up a few motors myself, through over speed. Destroyed a small 3hp motor when a com bar lifted at high speed (about 5000 rpm) - didn't notice it at first, other than a slight "stutter" which I thought was just a bad connection......until it ripped a few more off, broke the brushes, smashed a brush holder off it's mount and pulled the wires around the com......THEN it let the magic smoke out! Had another bigger one that suffered over speed after the field current dropped to zero (shunt motor, bad controller), while it was under test with no load........armature windings pulled out, and snagged around inside - nasty! I thought it was going to explode when it sped up- so I ran like hell.

They were free motors I got from a junk pile, to make a high speed electric go-cart. Never did finish that project.


Only name I can think of for the car is "Sparky"....


SS

[brightsparkz]

These motors can be over reved and the coms are known to explode.

Yep, I've blown up a few motors myself, through over speed. Destroyed a small 3hp motor when a com bar lifted at high speed (about 5000 rpm) - didn't notice it at first, other than a slight "stutter" which I thought was just a bad connection......until it ripped a few more off, broke the brushes, smashed a brush holder off it's mount and pulled the wires around the com......THEN it let the magic smoke out! Had another bigger one that suffered over speed after the field current dropped to zero (shunt motor, bad controller), while it was under test with no load........armature windings pulled out, and snagged around inside - nasty! I thought it was going to explode when it sped up- so I ran like hell.

They were free motors I got from a junk pile, to make a high speed electric go-cart. Never did finish that project.


Only name I can think of for the car is "Sparky"....


SS

Haha, hope i dont blow mine up. it cost enough! You are not ment to use series woind motors with no load as they rev up past their design max speen and fall apart as you found out. the controller i am using should stop that. What you need for your project is a lynch motor or a etek. Check them out...

sparky sounds good haha, any other ideas anyone? I'm off to weld triangles all over the rear sub to stiffen it up.

[Silicon Skum]

Haha, hope i dont blow mine up. it cost enough! You are not ment to use series woind motors with no load as they rev up past their design max speen and fall apart as you found out. the controller i am using should stop that. What you need for your project is a lynch motor or a etek. Check them out...

Yeah, very dangerous to use a series wound motor without a load, however this was a shunt wound motor (the field coils have a seperate current feed from the armature, so are safe with no load) - but losing the current on the field coils has the same effect (back emf drops, armature pulls a LOT of current and speeds up FAST!).

I know about the Lynch and Etek disc motors, very nice - expensive though. Keeping an eye on fleabay. Slap a Sevcon Milipak controller in the mix, and it should be a nice setup!
I have an old washing machine motor (universal motor - so works on DC) that is sitting under the bench in my garage....been toying with the idea of chucking it on the go-cart and running it as a series motor (it's actually shunt wound, but you just connect the armature and field coils in series), and "see what happens". I have enough SLA batteries to make about 110V - should be enough to get a bit of speed out of it - don't know the wattage rating though (prolly only about 300W or thereabouts). So not exactly fast, then...

Hehe, DIY Sinclair C5!

The project I'm working on at the moment is a small electric trike (just for giggles, plus I will be using it to test home brew PWM controllers), and this is what I want the etek motor for. Just need to get a few bit together first. Will be trying and get it road legal and have it MSVA'ed and taxed (tax should be free....I think). If this works out, then I'm going to start investigating a car conversion.

SS

[brightsparkz]

I have a 200mm dia Lynch motor but its all mine! You never know when it might come handy Good luck with your project!

[getthewheelsinline]

Hey Guys!

I was considering looking into the feasibility of undertaking an electric mini project using some equipment I can acquire:

I can get my hands on the following from work - this was removed from a redundant automatic guide vehicle (AGV).

Would these be of any use - obviously I would propose to reduce the size of the battery banks - as each 48volt(420AH) bank is 504KG!
( I can get my hands on 4 banks - so that would do a few minis I would think!!!)

Spec plate on them:
Varta Perfect - JHB Industrial Batteries
Type 4P25 420L
Capacity 5H 420AH 48Volts



Battery Charger for the above (2-off):


Im am still investigating the motor that is in the actual AGV - once I know the Spec, I will post up!!

Any of you electric gents out there know if these would be of any use?!? If so, What size should i reduce the bank to?

...........or should I agree with the rest of my work colleagues that I am wasting my time? HA!

Thanks in advance,

Callum

[Silicon Skum]

Hey Guys!

I was considering looking into the feasibility of undertaking an electric mini project using some equipment I can acquire:

I can get my hands on the following from work - this was removed from a redundant automatic guide vehicle (AGV).

Would these be of any use - obviously I would propose to reduce the size of the battery banks - as each 48volt(420AH) bank is 504KG!
( I can get my hands on 4 banks - so that would do a few minis I would think!!!)

Spec plate on them:
Varta Perfect - JHB Industrial Batteries
Type 4P25 420L
Capacity 5H 420AH 48Volts

As far as I know, those are lead acid batteries, and use a gel acid electrolyte - and they have prolly been in service for some time, and will by now be likely nearing the end of their usefull life. They could be reconditioned and give another few year service, but I don't think it would be worth while as gel electrolyte batteries are sensitive to shock / vibration, or over charge / discharge abuse, which causes the gel to seperate from contacting the cell plates. Difficult to cure this problem.
These rail batteries have a life time of about 8 - 10 years, so depending on how old they are (and if they have been charged in the last 6 - 12 months) they might still have a bit life left in them yet. I don't really have any more info about these batteries, though a rail engineer could prolly shed some light. I think these Varta batteries were manufactured by Hawker, under the "Hawker Perfect" brand, might be able to find out about them from there. Rail batteries are not realy my area, so I'm not much help on this.

Chances are you could prolly make up a few decent battery packs out of them, and if they are free - it might be worth doing. You will need to find out the Ahr rating of the individual cells so you know how many you will need in parallel and series to make up a pack for the right voltage and capacity (depending on motor voltage). Prolly worth a go at least.

Might be worth while to test the waters on e-bay, these might just be worth something on there. I susspect they would be used for a battery bank for a wind generator or solar setup for those running "off grid" power systems, rather than for electric car use (sounds like they might a little too heavy for the average car setup). Obviously postage would be out of the question.


Depending on the motor size, weight and output power, it might be ideal for a car conversion - if you can get the motor control gear that goes with it too. I would defo get these bits if possible, and use some new AGM lead acid batteries (traction duty - golf cart or similar) which should be easier to handle and install in a mini or other car (the Varta cells will need to be individualy seperated and insulated from each other - or they will short out).

SS

[mrbell321]

One nice thing about free stuff like this is if you can make it work now and it will last you a couple years, new battery tech will be out and you might be able to swap in a new pack w/ minimal effort. Get's you done sooner with too much expense, and it's fairly easy to upgrade whenyou need to.

[brightsparkz]

Hi Callum,

You should be able to use those batteries but it wont be ideal. Those batteries are pretty heavy, the huge capacity will help you with the range of your car but you have a low voltage of 48V. I plan on using 156V in my project and using 40-50Ah batteries to get me 40-40mile range. Lower voltage means that your motor will produce less rpm meaning that your top rpm will be lower. I think you should use those batteries as a test bed for now and get sealed lead acid (SLAs) once the car is done.

Suren

[Silicon Skum]

Hi Callum,

You should be able to use those batteries but it wont be ideal. Those batteries are pretty heavy, the huge capacity will help you with the range of your car but you have a low voltage of 48V. I plan on using 156V in my project and using 40-50Ah batteries to get me 40-40mile range. Lower voltage means that your motor will produce less rpm meaning that your top rpm will be lower. I think you should use those batteries as a test bed for now and get sealed lead acid (SLAs) once the car is done.

Suren

Another point to make regarding the voltage, is that the higher the Voltage - the LOWER the Amperage needed for the same power! This means that the cables used to provide power to the motor, battery interconnects, switch gear etc, can be thinner and will run cooler, than if you are using a lower voltage. This will be cheaper and MUCH more easy to route the cables.
Still requires heavy duty stuff, mind - but it will not be as heavy a guage wire as you would need to use at low voltage to get the same power from the motor.

48V is doable though, though I would be tempted to run the 48v traction motor at a higher voltage, say 72V wich it should be able to tollerate OK. This will require six 12V batteries in series (to increase voltage), and the same number in parallel (to provide more current) or even more - depending on the Ahr (current) rating of the batteries used. Depending of the control gear, this too may be able to handle the higher voltage - but you will need to confirm this first. 72V is quite common voltage to use, so switchgear is available for this voltage.


Also I mentioned AGM batteries (Absorbed Glass Mat - electrlyte (acid) is absorbed in glass fibre, not gell or liquid), these are a type of sealed lead-acid battery, simmilar to an "SLA" type battery - BUT are the ones you should use, as opposed to standard SLA types (which are usually gelled electrolyte). There are many advantages to AGM over standard SLA types, the primary one being the ability to handle higher current delivery, and handle abuse better - so are better suited to motive use.

The battery banks you have at work, are gelled electrolyte types, but I belive these are NOT sealed - I think they have vent caps and may require monitoring of water levels (as I said, rail batteries are not my thing - so not 100% on all deatails).

As said above, they would be ideal as a testbed for the vehicle - so would be worth a risk.


SS

[bigmotherwhale]

i like your ideas, been wanting to make my own electric mini for a while now but i dont like the idea of lots of batterys weighing things down, also i wanted to make my own motor, a brushless repulsion motor run pulse discharge from 5000v microwave oven capacitor banks charged by an inverter. tho this is very dangerous as 1 jolt and you could lose a finger or even your life. tho doing it this way makes things alot easier on the control electronics side as you dont have to handle such high currents. high voltages are easyer to control just harder to keep in the wire lol

1 thing i sugest you look into, tho this is very complicated and makes some people go "thats imposible it violated the third law of thermodynamics" or "your insane" is charge recycling, it is possible to power inductive loads and charge batterys at the same time by the use of clever switching it will not run forever but the efficiency of the system will increase quite alot. its something to think about for the future, its wise to start with a small model and make that work and understand it before atempting to build one into you current system (no pun intended)
il give you more details so you can have a play with the circuit and see for you self if it works