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SeniorShizzle

Expected Range from miniPRO 260? App range drops instantly when mounting.

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Hello guys,

I've spent quite a bit of time perusing the forum (and others), but I haven't found much information about the new miniPRO 260 model, which I own two of.

I bought my first miniPRO 260 from Amazon during the last sale. I was hesitant because of the smaller battery, but I figured that 1.5mi deficit was not a huge dealbreaker. When the unit arrived, however, I was surprised to see the app estimating an 11mi range with 100% battery. I know that range is dependent on riding style, temperature, weight, etc, but I at least expected the app to estimate the full 12.5mi range when fully charged. 

Furthermore, I have only ever achieved about 7 miles of actual range on the miniPRO, with normal riding over flat terrain, and tires at 45psi (I weight 175lbs). Based on my research, I figured that this was way too low, so I exchanged the unit. The new miniPRO 260 now advertises 14mi on a full charge, but that instantly drops to 11mi the second any weight is placed on the foot sensors!

Does this happen to anybody else? The drop is universal at 3mi, meaning it will, for instance, go from 9 to 6 mi when at that level.  I guess I'm curious what other miniPRO 260 owners report their app saying, and if the range is actually that much different than mine. I just got the replacement unit this evening, and I haven't had a chance to ride it to empty yet, but so far it seems about in-line with my previous miniPRO.  

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Posted (edited)

The MiniPro 260 has, I believe, a 236Wh battery.

Stated Range really is a fiction in the “how long is a piece of string” category. The four biggest variables, all of which make massive differences to the range, are: rider weight, speed, tire pressure and temperature.  Weight usually has the greatest effect but cold weather (temperatures less than around 40 Fahrenheit) can easily halve the range and so can too low a tire pressure. Most EUC manufacturers, being in or near China assume a rider of less than 100lb so real range with a Western rider is invariably no more than half the stated figure. I would expect Segway, even if their wheels are manufactured in China, to be more accurate than most though?

Generally, on Electric Unicycles (EUC’s which I know a lot better) range is in the 16-30 Wh per mile range. 20Wh/mile is probably a good ballpark figure for a 175lb rider at MiniPro speeds.  That should give you a full to empty range of around 11.8 miles.

I cannot see a MiniPro doing better, it’s slower speed will help increase range but two small wheels must result in more drag than one large one so I would expect figures to be VERY similar.

Estimating range on an App is even more of a “how long is a bit of string” guess. There are only two ways to do it:

  1. The battery voltage reflects the state of charge 4.2V/cell is full and around 3.5V/cell is empty. Since a certain voltage equates to a level of charge, assume a range based on present voltage. Every Personal Electric Vehicle I have come across uses this method.
  2. have a sophisticated wattmeter built into the vehicle, and assuming the battery actually has the Wh it is supposed to have, keep track of battery watt delivery with an accurate odometer as well. No personal electric vehicle I am aware of uses this method, it is more usually seen in phones (minus the odometer bit!)  and I suspect Tessla do it as well but Segway might possibly do this (I doubt it)

The problem with (1.) is that voltage is proportional to current flow as well since batteries have internal resistance - small batteries have way more internal resistance. As soon as you draw power from the vehicle it’s range will appear to drop. If their algorithm hasn’t been adjusted for the smaller battery it would be way more inaccurate than the larger battery version.  

The problem with (2.) is it easily gets screwed up and often needs a deep discharge/charge cycle (a damaging thing to do to Lithium Ion batteries) to get it reading sensibly again.

Finally the best ways to ruin the range of Lithium Ion batteries is to cycle them from full to empty regularly or leave them fully charged for long periods. They can lose a third or more of their capacity in a year - especially in hot climates. Ideally leaving them stored at 40-50% and cycling from no more than 90% to 30% keeps the best capacity in them for the longest time (but that has nearly halved the range again of course.) 

I remember reading some posts saying MiniPro chargers were not giving a full voltage so as to improve battery life, at the moment I cannot find the posts, but it is mentioned in passing in the last post of the second link below - that would very much reduce range and cause the apparent range to drop suddenly.

see also: 

 

And 

 

Edited by Keith
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@Keith Thanks for that very detailed analysis of battery life and milage! Very thorough! To address some of your points: the miniPRO charger does undercharge the cells to prolong life (it has 15x2 18650 cells, but charges to 59.9v instead of 63v, meaning charging to only about 81%). The "undercharge" figure is actually where Segway quotes their range for marketing, and some people have gotten as much as 20mi on the 310wh unit with a 63v charger. The miniPRO's BMS is very intelligent, and also does track instantaneous wattage/amperage of discharge and charging; it displays the full and remaining mAh/mWh, which I believe is how it determines range.

 

What I am interested in, though, is a comparison between what other miniPRO 260 owner's are getting in their app estimates at full capacity. I have pretty substantial reason to believe my miniPRO has a faulty cell somewhere in that battery (I have contacted Segway and they have suggested sending in for cell voltage testing). 

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Sounds to me like they needed a quick hack to account for the new battery while at the same time support their ridiculous marketing claim for mileage, and the software has some bugs.  10-12 miles seems pretty standard for a MiniPro with standard charger, so you're mileage may not be that far out of line.  Unfortunately the BMS has little chance of detecting a single dead cell, and will in fact just over charge the other cells in the parallel group shortening their life.  So if the pack over all has a shortened life it will become clear there was a problem earlier in the pack, that was made worse because it was undetectable.  Unfortunately probably no one monitors each and every cell in a pack unless the pack is very small or a single series string.  It's not so easy without causing other issues.

The mileage estimate is just for show, you can watch the charged capacity which they can track closer, but they only report mAh I believe not Wh so you have to try to do that calculation on your own, but I would use the nominal voltage, not the reported voltage. so you can compare relative to the nominal rating of the Battery Pack, rather than the apparent Wh remaining at any point represented by the current voltage of the pack.

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I am using my new minipro 260, CHARGE up to 100%, in a golf course with very Low slopes.

The ambient temp is 25 °C, my weight is 78 Kg, the tire pressure is 45 psi. 

Three times I have achived 7 Kmts útil the battery is 3%, just enought for 15 Holes, then I am intending to CHARGE the unit during 15 minutes, at the end of the 9 first Holes. 

 

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