Power/Torque increase on a Powabyke Euro 6 speed?

[Jango]

Hi guys,
I have had a defunct euro 6 speed in the shed for about 6 months waiting for a diagnosis and repair but before I started on that I was hoping for some advice from the more knowledgable members about upgrading.

The root of the problem is that my daily ride to work involves 2 miles of hill, to be precise 1 mile at a gradient of approx 10-15% and 1 mile at 20%. When I first got the powabyke it was fine but a week of the hill and it could stand no more. Even with me helping we could barely manage 6mph up the hill.

So my question is: is there a way to increase the power of the bike without changing the hub motor? From a bit of browsing on the forum I have the idea that if I were to increase the voltage (ie to 48V) along with a commensurate upgrade in controller, this would give more power at the cost of a greater drain on the battery. Is this correct? if so will it damage the motor at all? do I need to drill holes in the hub for ventillation? can I simply put 4 12V batteries in series to achieve the 48V?
I am sure there are issues with this idea I have missed but if there were some way to increase the power it would great as I am changing the batteries anyway so it seems the best time to do other messing about.

Any help appriciated!
Cheers

 

[NRG]

Increasing the voltage with your current controller will make the bike go faster but only if the controller can handle the extra volts. It wont necessarily make it climb hills much better. You could try and solder the shunt in your existing controller in the first place to see if that helps on the hill, Fordulike put together a nice tutorial in the Technical section on how its done. Doing this will drain the battery quicker on the hills and if your battery is not up to much the voltage will drop more than before under load....so you may end up buying a better IE: stronger battery anyhow in which case a better controller may be in order!

 

[Jango]

Increasing the voltage with your current controller will make the bike go faster but only if the controller can handle the extra volts. It wont necessarily make it climb hills much better. You could try and solder the shunt in your existing controller in the first place to see if that helps on the hill, Fordulike put together a nice tutorial in the Technical section on how its done. Doing this will drain the battery quicker on the hills and if your battery is not up to much the voltage will drop more than before under load....so you may end up buying a better IE: stronger battery anyhow in which case a better controller may be in order!

Thanks NRG, have got as far as removing the LED power indicator section and since there are no more screws I assume the controller assembly has to be wheedled out gently with a screwrdiver which can wait until the morning when it is (hopefully) less cold!
Thats a great tutorial, looks like it may be time to break out the old soldering iron.
However unless the controller can handle 48v which there is no reason to think, as it is still the original controller, it might as well be replaced anyway it seems to me. On a side note if the controller is 36v could it handle 48v? I have no idea what the flexibility/range of these things are like.
Finally if I were to get a better controller such as a 48v 30A would this mean I would have to get batteries also rated at 30A or will it simply draw as much current as is present (and will this mean a shorter range)?

 

[NRG]

If you went for a 30A controller then yes you will need a battery that can tolerate that sort of discharge rate but you would also need to be careful that you do not destroy the motor in the process! With your motor 30amp is probably too much better to keep is down to 20 or less.

The controller may take 48v, check what FETs it uses and what the voltage rating of the capacitors are...usually caps will be rated for 50v sometimes 100v and the FETs 55v or so and the better ones 100v. On a cheap controller typically its 50~55v. Keep in mind a 48v battery when fully charge could exceed 55v...

 

[Jango]

If I were to use the shunt mod to increase the power the motor can draw would it be necessary to use a new controller or would the current one work (currently working with 12v 15ah sla batteries)? What would be the effect of the drop of voltage under load? Would you consider it more worth while to go for a new controller and batteries at 48v keeping ah under 20 or to simply replace the current batteries but perform the shunt mod to tackle the hill? A final point of interest would be if anyone has any idea what kind of life-span reduction can be expected from use of the shunt mod?

 

[Deleted member 4366]

SLA batteries can give quite good current - if they're good batteries. It's possible that ypur ones are simply knackered. I would take things in stages. First, get a decent battery. Then solder the shunt.Only then should you think about a 48v battery, which has the potential for more speed. Some people say that 1C (12A for a 12AH battery) is the max current for long life, while as others run at 3C (36A) and report long life. I think it depends on the quality of the batteries. Leaving them discharged and deep discharging can kill them pretty quickly. In my experience, you need 25 amps or more at 36v with a geared hub-motor to get you up a 10% hill without pedalling - less if you're a lightweight.

It would be good if you could post pictures here to show the controller and what's inside it so that others can learn from your trials and it's easier for us to advise. Upload you pictures to Photobucket.com and then copy and paste the IMG link for full sized detail.

Do you know whether your motor is brushed (2 wires) or brushless (3 or more wires)?

 

[NRG]

Take it in stages as d8veh says...I'd do the shunt first to see the effect, if the battery cant take it then look at replacement. Advantage of SLAs is the price, downside is the peukert effect they suffer under load which reduces the effective capacity by about 30%, the relative short cycle life, the high weight and size. With your motor keep the current down, 25amps is OK on the higher rated BPMs etc

 

[Jango]

Thanks NRG & d8veh, I think you are right, the 1st step being to get a working set of 12V 20ah batteries (that is actually the problem which stopped me using the bike, on the hill suddenly all the pulling power went and when I got to the flat there was almost no pulling power, barely enough to pull me along and keep upright even with me helping out!).


Well here is the controller extracted from its case after some small struggle, turns out that just behind the mounting screws that held the controller into the LED power indicator housing, the casing had been glued to the controller as well!

It is not what I was expecting and there is no obvious information regarding the voltage and amp levels it can handle.

Here is an oblique view of the controller in which the shunt is more obivous but it looks like its in an awkward position for working on but oh well.

The only information on the great big capacitor reads 100V - 200mF, recalling my standard grade days in physics I can dredge up that Fahrads are a measure of capacitance but no more. Where about would I look to find information regarding the voltage and amperes the controller can handle?

Apologies for the rubbish lighting, the light in the shed is pretty rubbish so I use a headtorch for working on the bikes to avoid loosing screws, the down side is it tends to reflect quite badly.

As for the motor, I cannot say for sure as I have not yet checked but since I have no reason to think it has been tinkered with I strongly suspect it will be a standard powabyke euro 250W brushed motor (though it could be a 200W, not sure how old it is).

SLA batteries are the only choice at the moment, at £300 odd for a LiFePO4 I will put up with the weight issue as well as the capacitance drop and cycle life for some time yet

 

[Jango]

Hey just had a quick thought while measuring my current 12V 15ah batteries (and discovering the replacement 12V 20ah I was planning to get dont bleedin well fit the case!). If I were to simply replace the current 3x12v15ah battery set up with the same but perform the shunt mod would the motor be able to draw more current? I know that the 3 volatages from the batteries is cumulative but is the available current actually 45A with the controller limiting it to 15A (or whatever it is currently using) or are Amperes not cumulative?
Sorry if this is an obvious question, my electronics knowledge is old and more than a little patchy

 

[flecc]

The Ampere hour capacity isn't cumulative in this case where the voltages are in series, it's either one or the other which is cumulative. In fact the Ah rating isn't an indication of what you can draw at any one moment, it's just a measure of content, i.e. 15 Amps available for one hour or 30 Amps for half an hour or 45 Amps for 20 minutes. Those are theoretical figures, in practice higher discharge rates mean less than the theoretical duration.
.

 

[Deleted member 4366]

I think that replacing the batteries is a smart move, and the new ones should be able to handle the 20amps that you want as long as you buy proper ones for electric vehicles. The shunt is that bit of wire in the middle of the PCB. The FETS are the upright components screwed to the aluminium heatsink. See if you can get a number off them.

 

[Jango]

thanks d8veh, I will hopefully get a chance to look at them tomorrow.
For clarification do you mean that the 15a (which are for electric bikes) batteries should be able to handle 20a?

Thanks also to flecc for the explanation of what amps actually are.

 

[flecc]

Per my post above, the 15 Amps available in an hour is equal to 20 Amps available for 45 minutes. As long as the batteries are of good quality and the right type as d8veh advises, they should deliver the 20 Amps ok.