100Kw (ish) DC electric motor
24-06-2009, 04:07 PM
#41
Well if I had 36 batteries, which is what I would need to have 3 circuits of 48V a piece each at 500A, then it would weigh around 95kg
Add the weight of the gearbox and motors, and you are talking 150-200kg total, so not dissimilar to an engine.
Those batteries are rated to 10ah, so at 180a, will in theory last 1/18th of an hour, but in reality probably more like 1/30th, so 2 minutes, which is plenty of quarter miles.
They are small though, 6 of them to the size of one medium car battery, so its just like finding a home 6 car batteries basically, which could of course be a sensible way to go down if I am now talking about much lower voltages, bear in mind when this thread started I was talking about hundreds of volts and much less current.
Might be that 2 truck batteries for example, would do 48V and 2000A on their own, and that would be dead easy to fit into a car
Or 4 car batteries likewise, at 500A is reasonable to expect from a decent car battery.
24-06-2009, 04:14 PM
#44
Too many posts.. I need a life!!
Join Date: Mar 2005
Location: south yorkshire
Posts: 638
Likes: 0
Received 0 Likes
on
0 Posts
Well if I had 36 batteries, which is what I would need to have 3 circuits of 48V a piece each at 500A, then it would weigh around 95kg
Add the weight of the gearbox and motors, and you are talking 150-200kg total, so not dissimilar to an engine.
Those batteries are rated to 10ah, so at 180a, will in theory last 1/18th of an hour, but in reality probably more like 1/30th, so 2 minutes, which is plenty of quarter miles.
They are small though, 6 of them to the size of one medium car battery, so its just like finding a home 6 car batteries basically, which could of course be a sensible way to go down if I am now talking about much lower voltages, bear in mind when this thread started I was talking about hundreds of volts and much less current.
Might be that 2 truck batteries for example, would do 48V and 2000A on their own, and that would be dead easy to fit into a car
Or 4 car batteries likewise, at 500A is reasonable to expect from a decent car battery.
Add the weight of the gearbox and motors, and you are talking 150-200kg total, so not dissimilar to an engine.
Those batteries are rated to 10ah, so at 180a, will in theory last 1/18th of an hour, but in reality probably more like 1/30th, so 2 minutes, which is plenty of quarter miles.
They are small though, 6 of them to the size of one medium car battery, so its just like finding a home 6 car batteries basically, which could of course be a sensible way to go down if I am now talking about much lower voltages, bear in mind when this thread started I was talking about hundreds of volts and much less current.
Might be that 2 truck batteries for example, would do 48V and 2000A on their own, and that would be dead easy to fit into a car
Or 4 car batteries likewise, at 500A is reasonable to expect from a decent car battery.
there jus so big coz each battery is typically 750-900 Ah each but bear in mind these also run coffe machines toilets, tv etc
24-06-2009, 04:26 PM
#47
Too many posts.. I need a life!!
Join Date: Mar 2005
Location: south yorkshire
Posts: 638
Likes: 0
Received 0 Likes
on
0 Posts
if you need new starters of to have them overhauled let me know
we get good discount at volvo for new one (with warrenty hahaha) and my sparky could also sort some out if u get second hand ones that need looking at
24-06-2009, 04:29 PM
#49
Nice one mate.
I'll do some tests on a car starter at 24v to predice what a lorry one at 48v will be like in terms of if it will melt and wether it really will double the power.
10 seconds across a field on the starter in gear in a scrap car, then put 24v into it and see if it can get back again in 5 seconds, lol (wont be quite that linear I realise, but should be certainly 7 seconds or less)
Then I'll have to set about seeing what lorry starters are big and common, as I want something thats 9kw to begin with at least really, and cheaply available secondhand.
Then need to join 3 or 4 of them together and stick it in something.
I'll do some tests on a car starter at 24v to predice what a lorry one at 48v will be like in terms of if it will melt and wether it really will double the power.
10 seconds across a field on the starter in gear in a scrap car, then put 24v into it and see if it can get back again in 5 seconds, lol (wont be quite that linear I realise, but should be certainly 7 seconds or less)
Then I'll have to set about seeing what lorry starters are big and common, as I want something thats 9kw to begin with at least really, and cheaply available secondhand.
Then need to join 3 or 4 of them together and stick it in something.
24-06-2009, 09:10 PM
#57
..BS Motorsport..
25-06-2009, 10:34 AM
#62
Professional Waffler
25-06-2009, 11:02 AM
#64
Professional Waffler
instead of laughing ill explain why it doesnt it theory
no machine is 100% efficient! i mean that you get less energy out than you put in
so your alternator takes energy to drive it, some of this energy is lost when you convert it into electrical energy, now you must run cables in your system, these aint 100% efficient aswell so we have another loss! now they drive our motor which now converts our electrical energy into torque, but sadly this comes at another loss! but remember that this motor is also driving the alternator! so we grind to a halt! lol
no machine is 100% efficient! i mean that you get less energy out than you put in
so your alternator takes energy to drive it, some of this energy is lost when you convert it into electrical energy, now you must run cables in your system, these aint 100% efficient aswell so we have another loss! now they drive our motor which now converts our electrical energy into torque, but sadly this comes at another loss! but remember that this motor is also driving the alternator! so we grind to a halt! lol
25-06-2009, 12:42 PM
#68
Advanced PassionFord User
Join Date: Feb 2005
Location: Solihull
Posts: 2,090
Likes: 0
Received 0 Likes
on
0 Posts
Try speaking to Simon Plummer at Flaktwoods (fan manufacturer) in colchester, or give Elta Fans a call. Both will have sources for motors of that size, I would've thought. They'll probably only be able to point you in the right direction rather than supply one, as fans tend to be 3phase ac....
Chris
Chris
25-06-2009, 12:52 PM
#69
Thanks for the tip.
TBH its looking like the batteries are going to kill it dead in the water though at the moment, unless I can find a 250v+ motor as otherwise the amount of battery weight to get the CCA high enough is ridiculous.
12 optima red tops = 20000A but also = 200kg+
TBH its looking like the batteries are going to kill it dead in the water though at the moment, unless I can find a 250v+ motor as otherwise the amount of battery weight to get the CCA high enough is ridiculous.
12 optima red tops = 20000A but also = 200kg+
Last edited by Chip; 25-06-2009 at 12:56 PM.
25-06-2009, 02:11 PM
#70
BANNED
BANNED
iTrader: (1)
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes
on
0 Posts
The CCA is the quoted value that the battery will supply current safely.
After that, the battery will attempt to deliver as many amps as it can until it destroys itself or the load in which the power is going in to.
At the point of the maximum destructive current or limit, the batterys voltage will begin to fall which will cause the amps to fall too but the battery is then at a point of destroying itself and continued/cummalative use of this will have a detrimental effect fairly quickly at the power ratings you are talking about.
Relying on the battery to do your current limiting is madness and dangeous as batteries even small ones can explode dangerously !
Lead acid batteries as found on cars can tolerate short term overloading as the chemical construction allows for a large portion of the reversal in the detrimental effects.
Be carefull !!!!!
The word you need is "inverter"
25-06-2009, 02:17 PM
#71
Simon, I am aware of all that mate, and will of course monitor what happens to battery voltage and temp if I try it.
The voltage is most likely to drop far enough that the current will drop too, and that will end up being the limiting factor, pointless putting numbers on it until I can test it though, so the above was only a rough guide, I will perform tests on one battery before buying 24 of them or whatever, lol
Invertor = less efficient, which means an increased current drain from the battery.
To get 240V at 500A out of an invertor that is fed with 12V isnt going to take 10000A its going to take even more than that as they arent 100% efficient.
The voltage is most likely to drop far enough that the current will drop too, and that will end up being the limiting factor, pointless putting numbers on it until I can test it though, so the above was only a rough guide, I will perform tests on one battery before buying 24 of them or whatever, lol
Invertor = less efficient, which means an increased current drain from the battery.
To get 240V at 500A out of an invertor that is fed with 12V isnt going to take 10000A its going to take even more than that as they arent 100% efficient.
Last edited by Chip; 25-06-2009 at 02:18 PM.
25-06-2009, 02:34 PM
#72
BANNED
BANNED
iTrader: (1)
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes
on
0 Posts
Less power loss than over driving the motor into its overated working range !
Yes its best to match the battery voltage to the motor if its a single speed but you will need a "ramp up" as said earlier on.
Ultimately as you have said too, cost is an issue !
Converting 12v to 240v is a bad example as the amps numbers are huge as will be cables needed to connect to the batteries..LOL
Never the less, the power conversion is still the same level of efficiency if the inverter isnt a halfords special designed for running your phone charger in the car..lol
25-06-2009, 03:05 PM
#74
BANNED
BANNED
iTrader: (1)
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes
on
0 Posts
Chip,
An invertor can do both and is efficient either way, all depends on your motor and battery choice to what you need.
But thats the original $64000 question !
While I think of it, A simple solution is for example....
Say you have 12 volt motors.
Run them from 2 x 12 volt batteries in series and use 2 solenoids with timers, the first solenoid switches in 12 volts to start you off, then swaps over to the second to switch in 24 volts.
Then you coudl once upto speed, switch back to 12 volts to save the motors life !
An invertor can do both and is efficient either way, all depends on your motor and battery choice to what you need.
But thats the original $64000 question !
While I think of it, A simple solution is for example....
Say you have 12 volt motors.
Run them from 2 x 12 volt batteries in series and use 2 solenoids with timers, the first solenoid switches in 12 volts to start you off, then swaps over to the second to switch in 24 volts.
Then you coudl once upto speed, switch back to 12 volts to save the motors life !
25-06-2009, 03:15 PM
#75
Simon, so you are suggesting I use an invertor, but dont know what for? 
Maybe I could use two, once to go up and once to come back to where I start, as if im just using one for the sake of it I may as well use two instead
If I have 20 batteries, I can have 12V through to 240V all without needing an invertor anyway, and im sure any motor I use will fall in that range.
Yes using different numbers of batteries for different amounts of power is one obvious way to do speed contorl and that would be moderately useful for a totally different application, have you tried actually reading the thread though as its not what I want, i want 15 seconds of the motors utterly flat out cramming every last watt I possibly can through them until the batteries nearly explode from trying, I dont want to cruise along at 30mph on it anyway saving the motors.
You input is very appreciated, but in this instance is somewhat off target.
If I do go ahead with this though, i will certainly tap you up for some info, I'll just make sure I ask very clear questions, lol
Maybe I could use two, once to go up and once to come back to where I start, as if im just using one for the sake of it I may as well use two instead If I have 20 batteries, I can have 12V through to 240V all without needing an invertor anyway, and im sure any motor I use will fall in that range.
Yes using different numbers of batteries for different amounts of power is one obvious way to do speed contorl and that would be moderately useful for a totally different application, have you tried actually reading the thread though as its not what I want, i want 15 seconds of the motors utterly flat out cramming every last watt I possibly can through them until the batteries nearly explode from trying, I dont want to cruise along at 30mph on it anyway saving the motors.
You input is very appreciated, but in this instance is somewhat off target.
If I do go ahead with this though, i will certainly tap you up for some info, I'll just make sure I ask very clear questions, lol
Last edited by Chip; 25-06-2009 at 03:17 PM.
25-06-2009, 03:18 PM
#76
instead of laughing ill explain why it doesnt it theory
no machine is 100% efficient! i mean that you get less energy out than you put in
so your alternator takes energy to drive it, some of this energy is lost when you convert it into electrical energy, now you must run cables in your system, these aint 100% efficient aswell so we have another loss! now they drive our motor which now converts our electrical energy into torque, but sadly this comes at another loss! but remember that this motor is also driving the alternator! so we grind to a halt! lol
no machine is 100% efficient! i mean that you get less energy out than you put in
so your alternator takes energy to drive it, some of this energy is lost when you convert it into electrical energy, now you must run cables in your system, these aint 100% efficient aswell so we have another loss! now they drive our motor which now converts our electrical energy into torque, but sadly this comes at another loss! but remember that this motor is also driving the alternator! so we grind to a halt! lol
Cheers for the explanation too. 
25-06-2009, 06:02 PM
#78
BANNED
BANNED
iTrader: (1)
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Chip
Simon, so you are suggesting I use an invertor, but dont know what for? Maybe I could use two, once to go up and once to come back to where I start, as if im just using one for the sake of it I may as well use two instead
Maybe I could use two, once to go up and once to come back to where I start, as if im just using one for the sake of it I may as well use two instead
Originally Posted by Chip
Yes using different numbers of batteries for different amounts of power is one obvious way to do speed contorl and that would be moderately useful for a totally different application, have you tried actually reading the thread though as its not what I want, i want 15 seconds of the motors utterly flat out cramming every last watt I possibly can through them until the batteries nearly explode from trying, I dont want to cruise along at 30mph on it anyway saving the motors.
Taking the piss for giving those solutions/options is not in the spirit of the comunity !
Perhaps if I was someone else, you wouldnt have done so !
Originally Posted by Chip
You input is very appreciated, but in this instance is somewhat off target.
If I do go ahead with this though, i will certainly tap you up for some info, I'll just make sure I ask very clear questions, lol
If I do go ahead with this though, i will certainly tap you up for some info, I'll just make sure I ask very clear questions, lol
I actually have vast experience in motor control and inverter design and I was just entering into a friendly discussion with everyone with my knowledge.
I have given advice, feel free to use or ignore it
25-06-2009, 06:15 PM
#80
BANNED
BANNED
iTrader: (1)
Join Date: Jul 2003
Location: Wiltshire
Posts: 12,483
Likes: 0
Received 0 Likes
on
0 Posts
Stephen,
FYI, This is how most diesel trains work and they are quite efficient.
Generators dont need high revs to produce big power, just a constant speed so diesel engines are good at doing that !
FYI, This is how most diesel trains work and they are quite efficient.
Generators dont need high revs to produce big power, just a constant speed so diesel engines are good at doing that !