SpinDaWheel Posted April 6, 2016 Share Posted April 6, 2016 I have only rolled out once, going up hill on a low battery, i wasnt going all that fast mostly because it was an Airwheel q3 but the 2 wheel design cause the wheel to slip directly backwards and deposited me straight onto my feet so neatly i was much more relaxes about going uphill on low battery below a certain speed, but now what is concerning me is going down hill on an mcm4 with only one wheel, is the possible/recommended descent angle the same as the recommended maximum uphill ascent angle and is it about as safe going down them on low battery? thanks for any advice Link to comment Share on other sites More sharing options...
Keith Posted April 6, 2016 Share Posted April 6, 2016 Way I understand it, it should be safe to descend any hill you can climb, I.e. If there is enough power to climb there should be enough to brakie to descend as well, providing the battery isn't already full. Not all wheels are born equal in this respect, so I would always approach a steep or long descent with caution. Descending with a low battery is ideal as there is plenty of capacity to take the charge, the biggest problem is descending with a full battery, this may leave you with nowhere to put the regenerative braking power you create and the wheel may switch off or simply significantly reduce torque. Climbing a hill should always use more energy than braking down the hill puts back so climbing first then turning around should be OK. Starting at the top of a long (not necessarily steep) hill with a fully charged battery is worst case I believe? The biggest 'hill' that I climb is two quite high floors on a travellator, by the top the wheel start beeping and tilting back a little, going down again is fine. However, we have a few members in nice hilly places like Switzerland so they may have better practical experience. Bottom line: try to go slowly enough to get off, if the peddles start to feel softer or the wheel starts to accelerate turn sideways to the hill and stop if you can. Link to comment Share on other sites More sharing options...
Gimlet Posted April 7, 2016 Share Posted April 7, 2016 It takes a lot more power to hold back going down a steep hill than it does to climb it. When climbing you are fighting the force of gravity on your total all up weight whereas when holding back going down a hill you have the force of gravity plus the momentum that you build up and that can be huge depending on your speed. Link to comment Share on other sites More sharing options...
DS Posted April 7, 2016 Share Posted April 7, 2016 55 minutes ago, Gimlet said: It takes a lot more power to hold back going down a steep hill than it does to climb it. When climbing you are fighting the force of gravity on your total all up weight whereas when holding back going down a hill you have the force of gravity plus the momentum that you build up and that can be huge depending on your speed. Interesting. Never have thought it that way. There is a rationale for this force of gravity + momentum needs more power...but at the same time, the energy regenerates back into the battery. Am I missing something? Link to comment Share on other sites More sharing options...
Gimlet Posted April 7, 2016 Share Posted April 7, 2016 Only the laws of physics! Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted April 7, 2016 Share Posted April 7, 2016 The big question is - has anyone had a EUC battery failure going down a steep hill, and what happens? Do you still fall forwards or do you tend to fall backwards? If the wheel just lets go, I would tend to guess falls backwards? Link to comment Share on other sites More sharing options...
Gimlet Posted April 7, 2016 Share Posted April 7, 2016 I've had loads more motor overloads/cutouts going downhill than up. You tend to do a very uncomfortable seat drop if you don't get your legs moving fast enough. Link to comment Share on other sites More sharing options...
Keith Posted April 7, 2016 Share Posted April 7, 2016 4 hours ago, Gimlet said: It takes a lot more power to hold back going down a steep hill than it does to climb it. When climbing you are fighting the force of gravity on your total all up weight whereas when holding back going down a hill you have the force of gravity plus the momentum that you build up and that can be huge depending on your speed. There is no power consumed in constant momentum (that's Newton's first law of motion). Going up hill the power required is to overcome gravity plus losses, friction, windage, etc, going downhill the braking is combating gravity but friction, windage, etc is helping keep the speed down i.e. it is working with braking so total power required in both situations to maintain a constant speed has to be less going down hill than up. I would agree that in order to slow down further or stop, additional braking power is required (and may well not be available) that is why I advised keeping slow and aborting if speed starts to increase by itself. what, I think, Gimlet is experiencing is that the braking on many wheels is not as efficient as acceleration, indeed regenerative braking may be generating voltages that are too high for the battery to absorb, which is why I warned to be careful. Link to comment Share on other sites More sharing options...
Shoe73 Posted April 7, 2016 Share Posted April 7, 2016 Another way to think about it: as you go uphill the wheel is pulling you against gravity so Consuming energy. On the way down the hill, you are using gravity to push the wheel down the hill, the wheel is resisting (braking), so on the way down you are Generating energy. The total energy generated downhill will always be less than the energy consumed going up the same hill, because in both cases there is friction causing heat, which is consuming energy. Link to comment Share on other sites More sharing options...
Gimlet Posted April 7, 2016 Share Posted April 7, 2016 The concept of it taking a lot more power/force to stop something that is moving going downhill than to move something that is still uphill was first revealed to me by Gregory Peck in the old filM The Power and the Glory when they were manhandling a huge cannon across Spain. It is a simple fact that once an object starts moving it's effective g force is multiplied by a factor of its speed. Link to comment Share on other sites More sharing options...
dmethvin Posted April 8, 2016 Share Posted April 8, 2016 3 hours ago, HunkaHunkaBurningLove said: The big question is - has anyone had a EUC battery failure going down a steep hill, and what happens? Do you still fall forwards or do you tend to fall backwards? If the wheel just lets go, I would tend to guess falls backwards? I had my one and only BMS cutout going down a rather steep hill with a battery at totally full charge. I wasn't going that fast, fortunately. The EUC basically just starts to freewheel. Since you're leaning back you're more likely to fall backwards, but I just kind of fell off standing up. The wheel kept going for about 10 feet and fell over. Link to comment Share on other sites More sharing options...
Gimlet Posted April 8, 2016 Share Posted April 8, 2016 My son had an overcharge problem on the mcmv2s+ only last Saturday. After going down the the long hill into the city with his brother on the KS and travelling a little faster than usual, they do tend to race a bit, the wheel went into beeping juddering mode and wouldn't balance. When he phoned I suggested he lifted the wheel and let it run free for a while to reduce the charge. After 10 minutes it was working again and after some riding around the pedestrian precinct for a while it carried him back home no problem. Link to comment Share on other sites More sharing options...
WakefulTraveller Posted April 10, 2016 Share Posted April 10, 2016 Would it be safe to go faster than the ordinary max speed of the wheel if going down a steep slope without breaking? Link to comment Share on other sites More sharing options...
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