Bike options for a fat bloke?

I've had some advice on here about a year ago when I was looking to convert my bike to electric. I've decided that I'll keep my old bike and get an electric bike to use alongside it.

 

My usage will be approximately 10 miles a day with a sustained 300-ish foot climb one way. I'm 125kg so need something that can cope with this. (Looking at my post last year I've lost 15kg since then, which is just scratching the surface).

 

With a budget of between £800-1000 what would be a good option for me?

 

Also, living in the Sheffield area is there somewhere I can test bikes out to make sure they are really the right option for me?

 

Thanks

Take a look at the woosh big bear

Interesting.... thanks for the suggestion.

Alternatively an Oxydrive 13ah cst kit on a 700c bike would be awesome, just built up a Boardman MX with this kit and it flies 250w @ 24.3 mph and thats with only a 46t chain ring and 11t rear top gear.I also have a big bear kit on 700c frame it is very good but the Oxy is better.

I'd need a new donor bike for that option though, and I reckon that would blow my budget.

BBS02 500W conversion kit.

http://wooshbikes.co.uk/?cdkit

 

It won't blow your budget and it encourages you to pedal.

The Big Bear could make you lazy.

My bike has hydraulic brakes. Is there a way round this issue?

it's easy, plenty of members have done that.

I made mine with a pair of 20p microswitches. You cut the cable of the supplied brake levers, solder the yellow and black wires to the miscroswitch.

If you use use reed switches, buy the ones that have rectangular bodies, much easier to superglue to your brakes.

Is there any discussion on this that I could be linked to? Without the kit in front of me I can't get my head around the problem, let alone the fix! When you say this won't make me lazy unlike the bb, what exactly do you mean?

example of hydraulic brake sensor:

https://endless-sphere.com/forums/viewtopic.php?f=2&t=59378

 

The Big Bear is a bit like a motorbike, you just throttle it up and it goes. No need to pedal nor change gear. The CD kit makes you select the right gear and encourages you to pedal. The reward is that you can exploit the motive power better, climb hills faster.

Gotcha, thanks. So I am just looking for a way to introduce a 'push to make' circuit for each brake lever actuation in order to cut the motor? I'm sure I could manage that.

 

Next bit of research will be into making a battery pack from r/c lipo cells. Do I need to match the 36v 15ah or is there any benefit/risk to increasing the voltage?

you should look for a donor bike with a large triangle to accommodate a downtube battery. Don't bother making the battery yourself, the saving is not worth it. Batteries are the weakest link in any e-bike kits and expensive to replace. A good supplier is what you need more, just in case your battery dies.

Panda, Eclipse, Cyclezee and Woosh are members of this forum. Buy a battery from any of them.

This is mine: http://evans-images.spongegroup.com/?w=640&i=http://images.evanscycles.com/product_image/image/8f3/926/a2e/33988/mongoose-tyax-super-2009-mountain-bike.jpg

Gotcha, thanks. So I am just looking for a way to introduce a 'push to make' circuit for each brake lever actuation in order to cut the motor? I'm sure I could manage that.

 

Next bit of research will be into making a battery pack from r/c lipo cells. Do I need to match the 36v 15ah or is there any benefit/risk to increasing the voltage?

 

IF you are familiar with the care and feeding of r/c Lipo they are unbeatable for ebikes due to low weight, high energy density,low cost and capability to supply high current with almost 0 voltage sag.

 

If you are not sure of the handling go with a factory pack as Trex suggested The r/c LiPo have improved but are to be treated with care especially with larger packs.

10 cell is probably your best bet for reliability.

I've had a lipo RC car for a couple of years and am happy with how to look after them individually. I'm confident I could make a decent safe pack if I can get some help on choosing the combinations of cells.

RC lipo on a commuter bike is a no no.

For cheap transports, weight saving is good but not to the detriment of reliability and capacity.

You make a fair point. Is the woosh battery good value or are there better options?

SYEBC is just down the road from you. Why don't you go there and try a few?

Awesome, didnt know they existed! Thanks!

RC lipo on a commuter bike is a no no.

For cheap transports, weight saving is good but not to the detriment of reliability and capacity.

Ease of use, safety and at work storage make sense, I forgot about it being for commuter usage.

 

But capacity?

lipo is considered safe between 3.7V and 2.9V for electric vehicles against 4.2V to 2.5V for normal e-bike batteries. You pay for 10Ah and can only use 6-7Ah out of the pack and still have to alarm it. Another problem is voltage sag. If you draw a lot, then you have to up the voltage of the alarm.

lipo is considered safe between 3.7V and 2.9V for electric vehicles against 4.2V to 2.5V for normal e-bike batteries. You pay for 10Ah and can only use 6-7Ah out of the pack and still have to alarm it. Another problem is voltage sag. If you draw a lot, then you have to up the voltage of the alarm.

 

Have you used high capacity hobby LiPo's? voltage sag is not an issue, my packs are the cheapo low current ones ONLY rated for 200 amp continuous output and 300 peak (36v 10 Ah pack), any voltage drop at ebike current level is negligible.

I used to run my 5Ah pack down 4 to 4.5 Ah with zero issues and never hit low voltage alarm levels, I dont recommend going below 80% capacity regularly on any Lithium but it hasnt hurt my batteries capacity doing it occasionally.

 

Can you provide a reference for your statement about capacity at E-bike current levels with R/C batteries as I have never come across that idea before.

LiPo is normally used between 4.2v and 3.2v as an absolute minimum, I always goto 4.2v and have never heard an alarm as mine are set to 3.3v under load.

this is a typical 6C discharge curve, I suppose it is an approximate use of a 36V 5AH lipo pack on an BPM e-bike at full throttle climbing a hill:

 

http://i243.photobucket.com/albums/ff47/DrunkRabit/lipo_discharge_curve_sm.png

 

As you shouldn't charge it at over 3.7V nor discharge it below 3V, the useable portion on the horizontal axis is between 1 and 9.

that graph shows 1 minute discharge per unit.

When you approach 9, how close do you think is safe?

I reckon if people can see how little time they have from the alarm to overheating, they'd think twice about using RC lipo on e-bikes.

this is a typical 6C discharge curve, I suppose it is an approximate use of a 36V 5AH lipo pack on an BPM e-bike at full throttle climbing a hill:

 

http://i243.photobucket.com/albums/ff47/DrunkRabit/lipo_discharge_curve_sm.png

 

As you shouldn't charge it at over 3.7V nor discharge it below 3V, the useable portion on the horizontal axis is between 1 and 9.

that graph shows 1 minute discharge per unit.

When you approach 9, how close do you think is safe?

I reckon if people can see how little time they have from the alarm to overheating, they'd think twice about using RC lipo on e-bikes.

 

The low voltage alarm is just that, it is an alarm ie. the last line of defence, its not a case of ride until the alarm goes off and then keep riding.

Mine are set at that level for safety, I have never had an alarm go off, the same as I don't ride until the battery cuts off on a normal pack.

If either event occurred I would not use the battery to get home.

 

That chart if using a 5Ah battery as stated would be 30A continuous discharge, what is the tested batteries continuous discharge rating, is 30 Ah within its accepted range?

It would not effect my usage anyway as an alarm is the last line of defence, but you have not provided the data to know if the curve is relevant not mentioning the fact that most people would not consider a 5Ah battery the needed size for 30 A continuous discharge.

 

You never gave the reference for your previous statement?

That discharge curve isn't correct, neither is your statement about 3.7v. A lipo cell is nearly empty at 3.7v. Lipos have about 80% of their charge between 4.1v and 3.6v. The normal charge voltage is 4.2v. Once they drain down to 3.6v, they start to accelerate downwards so you have to be careful once they reach that voltage.

 

All the lipos that I've had gave the nominal capacity when used with an ebike, i.e. two 5ah packs would give 10ah of real use, as measued with a wattmeter.