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I'm working on a Lithium conversion and was wondering if anyone's tried running a higher voltage in their Ranger? I was considering 20-24 Lifepo Prismatic Cells. Can the controller and motor handle it? Obviously would need another charger and dc-dc convertor.
 

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It is my understanding that in DC applications voltage should match for the best service life and reliability. A motor designed to operate on 48 volts will run faster in a no load situation if supplied higher voltage (under load the RPM may not be much higher) and will run at higher temperature which will eventually reduce service life. If the voltage difference is high enough the motor may simply fail.
 

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On the Conversion I supply in the UK , the voltage is upped. Charges to around 64v and runs around the 60v area for a lot of the charge. The inverter works fine but has to be re programmed to suit the voltage range. The motor isnt run at pack voltage but lower based on the power outpout of the sevcon. The DC to DC has to be changed. You cant run the sevcon at 72v. Outside its max operating voltage. The voltage makes no difference to the motor speed,thats controlled by the frequency of the AC output, Thats controlled by the sevcon, and the settings dont need to be changed for rpm, and in my mind shouldnt be done. The delta q can be reprogrammed, but does not charge the final couple of volts at max charge..
 

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Discussion Starter #4
Grumpy,

I know you work on these things regularly. So if I bump voltage to 64v nominal, the inverter can handle it (w/reprogram), the Sevcon and dc-dc converter would need to be changed, and the charger reprogrammed. I saw some of your other posts where you recommend higher ah packs in these buggies. I have a pretty good and fairly inexpensive supper of prismatic cells. I don't want this thing to fly down the road, but I do like the range, weight reduction, and life cycle of the lithiums.
 

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It is my understanding that in DC applications voltage should match for the best service life and reliability. A motor designed to operate on 48 volts will run faster in a no load situation if supplied higher voltage (under load the RPM may not be much higher) and will run at higher temperature which will eventually reduce service life. If the voltage difference is high enough the motor may simply fail.
JackA,

I understand. I'm not really worried about service life. If it breaks, I'll put in a bigger motor, kind of like drag racing. LOL I understand that running a higher voltage will actually make the system more efficient. Just from my research. I do know that the Bad Boy buggies running 72V are beasts.
 

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If building any conversion, you have to make a decision about doing it because you can and dont worry about the consequences, or like me I do this for a living and so have to build systems that work and dont damage the vehicles in the process. There is noting to be gained from pushing the vehicles to their limits, ie the talk of higher speed. These are not built for that without big changes, and those are not for the normal user. Who just wants a working reliable long lived vehicle. The voltage increase has some improvement. But even at a lower voltage, my first conversions were 16 cell Lifepo4 52v, with a decent Ah (these had 320ah) Li have the advantage over lead of a significantly reduced voltage drop in use and through the whole charge, unlike lead that constantly drops from the moment you start using the charge.
If you have separate cells, then build a pack that works within the original parameters , and give it plenty of Ah. But never forget the BMS and its link to the charger. Thats paramount.
 

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If you have a simple DC Buggy upping the voltage will up the speed. On a dc motor rpm is related to voltage. Thats not the case with an ac motor, its related to the frequency that the field coils change their polarity around the motor. And with feedback, ie an encoder, the controller knows which direction the motor is running and at what speed, the controller is told what speed to go for or what power level to achieve, (within the max set rpm) and delivers enough power at the correct frequency to meet the commanded power / speed. Very different from just upping the voltage on a DC vehicle. If I recall the Ranger motors are actually rated at 30? volts . But thats each field coil and these have three. so on a three phase motor the voltage seen by the motor is constantly varying as the coils are energised and partially over lap. Think of an ac motor being a bit like you laying a bar magnet on the table and pulling it around in a circle by circling a magnet outside of it. As you move your hand the object will be pulled around/ repelled by the opposing magnet fields. In an AC Induction motor, it has a series of three set of coils around the outside over lapping each other. As Each coil is energised in turn the magnetic field will rotate around all the coils, and by turning the coils on and off in sequence the filed will rotate. As the coil cause the field to impose upon the rotor that induces an electrical current in the rotor windings, and that current creates a magnetic force, that opposes the field coil magnetic field and rotates the rotor. If the filed coil didnt then turn off and another take over physicaly a bit further around the motor, the rotor would just stop, but it does and moves to the next coil set and so on causing the rotor to turn, the frequency that the coils change polarity then is what dictates the rpm. (and the number of separate coils in the rotor, The strength of the magnetic field is what gives you the power to move the vehicle. That strength of field is dependant on the magnetic power the coils can create and the rotor generate by induction.
Simple.
On a normal mains motor it will just run at a constant speed, depending on the number of sets of field coils and the mains frequency. So your 60hz mains motors run slightly quicker than the same motor would in europe 50hz.
In a permanent magnet AC motor, there are no rotor coils just expensive magnets set in the surface of the rotor, and these are pused and pulled around by the rotating field coil. Here the ultimate power outpput is limited by the inbuilt magnetic power of the fixed magnets. The torque is then related to the distance from the center shaft and the power applied. Such motors rely on high accuracy manufacture, and very close gaps between the rotor and the field coils. So not cheap to produce.
 

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Discussion Starter #8
Ok, I think I got it. Hats off to you Grumpy, you sure seem knowledgable. Thanks to guys like you who keep us knuckleheads straight. LOL

So I think building a higher capacity pack would be the best for this buggy. 320ah is a lot of capacity and must cost a few pounds in the UK. I've got (16) 152's but will save those for a golf cart or Bad Boy Buggy build. I've got an email in to my Chinese supplier on some 280ah Lifepo's which should cost about $75 a piece. I figure 16 of those should make a nice 58.4v pack. I plan on using a Chargery 16S BMS which will give me low and high voltage cutoff protection, so that will keep the charger from over charging.

One last thing. Do I need the pink wires on the current battery pack if I don't need a hot 12V?

Thanks again.
 

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If no 12v to pink, then you wont get any charge lights. Never tap off a 12v from a Li pack, it will unbalance the pack .
Remember a cheap price in china may not be a cheap price delivered. The transport costs will be surprisingly high, as may be the import and tax costs importing them. Then dont forget the carriage company (DHL, Fed ex UPS etc ) will also make a charge for their services collecting the taxes. Also on quality. If its cheap then the quality is likely not to be good. You should expect to pay around $1 / ah new cost. . If you buy a cheap product buy enough to accept that they wont all work as you expect. There will be failures and in a year or less you may not be able to get any replacements that match. You really do get what you pay for.
 

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what is the motor mount face called? is like a 19 spine dana/ team industry? couldn't a different motor option be available? I have been looking at this for several months now. its how I found this post. can some one answer this?
 
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