gwhy

No, Sorry that was a little mis-leading, yes Im using 44 volts but not on a oset,, Its a grown up version of a electric trials bike

Your quite right, I was just talking about charging. The big risk when using different configurations of there batterys is if like me running 44.4v ( 2x 6cell) paralled with another 44.4v and only charging them with a 6cell charger but if your using just 6cell in parallel with another 6cell then all should be good. Still be wise to check each 6cell pack are balanced initially before paralleling them up. If one cell is no good in one pack this can kill the 2 packs, and that's not good.

Charge each 6cell pack separably first and check that the pack is balanced ( each cell is within about 0.02 of a volt from each other ) It may be wise to run a balance cycle on each cell pack first off anyway. once you happy with the batterys ( i.e all the cells are charging and discarging at the same rate ) you can parallel them up to charge them but you will have to either make yourself or buy a charging harness to allow this. Parallel charging is ok ( as long as the batterys are the same voltage and capacity ) but you really have to think about when you are connecting the batterys together to charge ( i.e the balance taps and the main outputs ) but this should be no problem if you are taking the batterys out of the bike to charge. Edit: I would also advise to put the batterys into a vented enclosure to help protect them from being damaged ( punctured ) in a fall. I use a diecast aluminum box like this one diecast box Use rubber grommets to bring the wires out of the box and drill a couple of small holes in one end to act as a vent

By increasing the voltage from 24 to 36 there will be a speed and power increase of around 30% and as far as I know the controllers should be current limited to around 30A so this should protect the motor ( as long as the controllers are ok on 36v ). The motor should be fine running on 36v if its a 24v motor. You do not have to up the voltage to get more power just the amount of current that can be drawn by the motor..so if you just want more power but without more speed then you will need to lift the current limiting which is done with the speed controller.

Just thought I will ask, But dont forget a charger as well ( You can not use a normal sla charger ) and also another bit of very good kit from HK is a watt meter , ( Im sure they do a cheaper Higher spec meter than this one but I cant find it ) This will give you running/pack voltage, AH used, max watts pulled and min voltage drop from the pack. If you want more detailed info on how to use/make the most of lipo's safely then drop me a PM.

It would be a improvement on sla's but only for the weight of the pack, LiFePO4 battery's can not deliver very high currents ( normally 2C about the same as sla's ) over extended periods, The pack in the link say's 10A Continuous discharge and only 25A Instantaneous Maximum Discharge so They are not really ideally suited to be a high performer but the pack will weigh about halve the weight of equivalent sla's and about halve the size you would need 2 of these LiFePO4's packs wired in parallel to really make them worth while on these little bikes . You can discharge them at higher rates but this will make them warm/hot and also make them deteriorate faster, So the extra cost may not be worth while. Where as a small 10Ah 22.2v lipo battery (15C or higher ) pack would be something like 150A Continuous and 300A Instantaneous Maximum Discharge so they should not get hot in use and the weight and size is about a third of sla's.

Personally I dont monitor at cell level when using my bike any more, I just monitor the whole pack (44.4v) and stop riding the bike hard when the battery voltage gets to around 40v , you start to get a feel for how well the pack is behaving by how quick it discharges. You can get cell level monitors in different shapes,sizes and functions and I used to use 2x6 cell monitors ( I use 12 cells ) that gave a voltage readout on a lcd screen with all 6 cells ( 12 cells in my case ) being shown at the same time and also has a audible alarm that can be set for a low cell each device was about 2"x1"x0.5" and was around

Lipo is the way to go.. as they can discharge at such a high rate there will be very little voltage drop under load unlike SLA so it will be a double wammy higher top speed longer running time and a lot, lot lighter. I have been using lipo for over a year now in my bikes and would never consider anything else. But care do need to be taken when charging, once in use they are as safe as any other battery. The 2 main things that can not be abused with lipo is never, never over charge them and never, never let them be discharged to lower than 3.2v per cell. A constant voltage/current charger must be used to charge them and I would recommend balancing the battery once in every 5 cycles. Ideally you need to monitor the cell voltage when in use to make sure no 1 cell goes below the danger zone.

Thanks Andy, I found it I Should have a rolling chassis by the end of the weekend, I will take some pics and get them up. The bike will be made with cycle components to keep the weight down, Im still looking for the complete bike to be around 25-30kg ready to ride and so far the frame/wheels/forks and shock weighs in at around 16kg so Im well on target. Also after a few tries at putting the pivot point in the same place as a gas trials and keeping the swingarm the same length I have given up for now.. and gone for a slightly easer design. There is also going to be a cycle bottom bracket on this bike so it can have peddles fitted so it can be ridden on the road as a push bike ( sort of legal if kept to 250W max for the road )except the motor/motors can produce upto around 11KW (15hp) The peddles will be quickly removable and allow foot pegs installed very easily. I want something that I can "cycle" upto the local wood/park/play area .

How do you post pics on here ? ..

Also thought I will post this up, Just incase no have seen it. Its very heavy and built on old tech but looks like fun.

Just another little bump... Just to try to keep this topic active. I have not got on as well as I have hoped with frame building.. But now its beginning to come together ( and Im on about my 4th prototype frame ) . I have also been working on a much better speed controller that will be much better suited to the abuse that a electric trials bike will demand.

You fund it and I will build it :-) , the one in the vid may not be upto it but the one im working on will be.

Another little bump update: Frame is sort of finished, I was originally going to use lightweight DH forks but the cost would be huge so opted for some motorcycle forks and I have been trying to source a cheap set that would be common enough to get spares or to replace/tune . This is the latest thing that is holding things up because I cant fit the steerer tube to the frame until I have some forks to get the angles/wheelbase right. Apart from this holding things up its all looking good and I have started to look forward to actually ride this thing on a easy route trial in the not to distant future, hopefully before the end of the summer...

I very much doubt that a GG 50 boy is 5-6kw more like 2-3kw and that would be peak power, ( A older Beta rev3 270 only peaked at around 12-14kw ) normal riding power would be around 500-750w, 750W on a small bike for a small rider should be more than enough to pull power wheelies as long as the bike is geared right, but 62lbs is very heavy for such a small low voltage bike . My suggestion would be to change the battery chemistry to a much lighter one and up the current limit on the speed controller ( as long as you are happy with the top speed of the bike ) this will help a lot. Edit : Or for a very quick/cheap looksy if you do not mind losing a bit off the top speed gear it down a tad maybe 1 tooth of the front sprocket or a 4-5tooth larger sprocket on the back.

Well its been ages, so I thought I will give this topic a little bump. My welding skills is coming along and have managed to start making a frame ( but I dont think its going to be the lightest thing in the world but its a start ). The bike what I have used to test the motor/controller and battery is holding up well and great fun to ride ( with more than enough power/speed for easy/novice routes and range) the frame that I'm trying to make will have enough space to use a electric motor that has twice the power of my current test bike so should be good enough for hard/expert routes but with the cost of maybe 1 battery swap in a typical 4 loop trial. cheers.

I think the throttles used are hall type, It may be possible to move the magnet or sensor in the throttle to get rid of this dead spot. I will have a look at one of the hall throttles that I have here to see how easy it is or indeed if it is possible. If its doable I will post some pic's. If they are resistive type throts then this is just a simple case of adding a simple resistor to the ground wire on the throttle connection.

A very small update, if anyone is intrested. Well I havent a heard a dicky bird from the chap who offered to make the frame for me so it looks like I will have to give it ago myself ( wont be until we start getting better weather tho ). I have also found a small problem with the electronics in my setup, the control of the bike is not very user friendly so some adjustment of some parameters are in order , the electronic 'clutch' needs a bit of work and also the throttle is a bit on and off'ish so I will be incorporating a throttle resolution 3 position switch ( hopefully this will mimic a 3 speed gearbox ).

As I have already said in a previous post electric bikes do make a noise its just different and quieter ( sounds more like a turbo ). And as far as can they compete with what we have now.. hell of course they can performance wise, there is just the problem of range ( cost of batterys is the limiting factor ).

All I know about this bike is it appeared in a forum ( not a Trials forum ) in 2006. Next time I talk to my mate I will ask him if he can remember where he had seen it.

If the old one is 24v then just over volt it to 36v but you would have to sort out a 36v controller. I know when these bikes first came out they used chinese motors and easy to come by controllers from china. The motors are fairly robust and can be over volted ( as long as they do not get to hot ). edit : I just have had a look at the spares for these bike and it looks like you will also have to change the motor sprocket. The controller will be a very simple mod to convert it to 36v ( It maybe just a power resistor on the input, you will have to compare the 24v and the 36v controllers to find the resistor value)

Know what you mean about lipo ( think safe sacks and a good BMS ) and all is well ) 2.5kw will be ok ( dependent on gearing ) I dont know what the max speed is on these little bikes, I am running a 170kv 3.5kw outrunner motor on a trials push bike geared for 22mph and that thing can have me off the back just as quick as my beta rev 270 used to ( with a highly modded controller ). I love these little bikes and my understanding is there is a upgrade to a 750w brushed motor which I think with the right controller will be the best combo also with a different bat chemistry. I would love to see videos if you do upgrade to the golden motor with lifepo4, will make one hell of a small bike .

10kw is a bit ott on such a small bike ( thats the sort of motor they put on full size motor bikes that do 60mph) look more in the range of a 2-3 kw motor max ( will still be to much power for a small rider ) and if you are comfortable with lipo batteries this chemistry is the best bang for your money ( smaller, lighter ,higher discharge rates and cheaper than lifepo4) the best way to upgrade one of these small bikes is to replace the batteries ( with a better chemistry of your choice ) and up grade the controller.

Just to keep this thread alive I thought I will post up a very nice electric trials bike ( it was found by a friend ) built from the ground up. I heard back from the chap whos is making the frame for me and he estimates to have it finished mid Jan, I am just tweeking the electrics and now have all the bits that I require to assemble a prototype.

I have taken delivery of a motor that I im thinking of using for this project, And on the up side its more than capable as regards power/speed but the down side it runs very hot and is very current hungry which will effect riding time per charge. Also I havent heard from the guy that is making the frame for a while, we decided on the dimensions that we will use and he was fine with that ( he came down with the swine flu so this has probably slowed him up a tad ). If I don't hear anything from him for another 3-4weeks I will have a go at making the frame myself ( which should be fun for someone who cant weld ), I still have plenty to get on with but my main concern is the motor current.