Hacking a SkateMaster (UK) board - help needed!

Hi guys,

Brit and skateboarding n00b here. I've been hankering after an electric board for years, after discovering xkcd author Randall Munroe is a big user of them - this despite me never having ridden a board before, btw. So, I finally took the plunge last week and dumped £85 into a Skatemaster board... and I'm starting to wonder what kind of mess I've gotten myself into!

Bit of background, I don't know how many Brits there are on here, but the e-skateboarding craze doesn't seem to have made much leeway over here. There are very few for sale, and only a small number of vendors seem to ship over here, at pretty high expense, so I wasn't very confident about getting one for a decent price. Then I found this one, but I can't find much information about it. It was bought second-hand, as seen, and all I got was the board, controller and charger.

Now, the good news is that the board works, which is a lot more than I can say for many others I found on eBay! The trouble is that the batteries are past it - they seem to last about half a mile and then the board can't even propel itself, forget with a person on it. I've taken it to bits and it's the usual affair - dual Chinese-made 12V SLA batteries in series for 24V, at a guess 7Ah. And blimey they're heavy! Lugging the board back home after it ran flat was NOT fun...

So, since I'm going to be replacing the batteries anyway, I figure I might as well do some hacking. I'm pretty confident with electronics. Now, the trouble is that I was being very truthful when I said I know next-to nothing about the board's specs - the company that made it, SkateMaster UK, seems to have gone under. There's some vague references here and there, including a short list of models, but nothing on the motor power. I don't know what model I have (my suspicion is the SF-X, but that doesn't help much!) or what the output of the power train is, but this board does seem to be pretty big. This is the board exactly: http://www.ebay.co.uk/itm/ELECTRICAL-SKATEBOARD-SKATE-MASTER-/161713508051

I guess the first step is to determine what the motor wattage is and go from there. There are no stickers on the housing, and the model number stamped on the casing, SFX-53M, doesn't help a lot - 530W possibly? I accept that's probably way too powerful for what I paid for it. The motor's a bit bigger than a standard drinks can; the wheels are about the same diameter.

Rather than replace the batteries with SLAs, I was wondering how hard it would be to swap in a li-po pack instead. As long as the voltage is the same, it ought to be plug-and-play for the board's controller, right? Obviously I'd need to get a different charger specifically for the pack. Of course, the li-po packs I've seen for electric bikes are more expensive than the whole board cost! So I thought, my intention with the board is to commute to work, which is a 1.5-mile journey through hills, so whilst it'll be quite demanding on the battery, at least it won't be for a long distance. I wondered, would it work to use a battery pack out of an electric drill? I've seen 24V Ni-Mh packs that manage 3.0Ah and are obviously designed to turn motors - maybe I could chain a few in parallel to cope with the high amperage the motor's going to pull? It would be cheaper than a li-po pack, but still be lighter than the stock batteries. Perhaps I could even rig them up to quickly eject from the board for charging!

I'm planning on doing some proper Arduino hacking later on, provided I've committed to using this board. Right now it's in pieces, so the first step is to get it running and usable. Can anyone help out?

There's more than one UK member here!

I am busy hacking something similar(ish). I am at the point now where the only bits left are the trucks. The rest has been swapped out, including a longboard deck. I think that may be ok to use as a starting point, but may not power an adult? I may be wrong. I think brushless motors seem to be the way, but you may need to modify the mount and drivetrain. Counting the teeth on the big and little gears on the motor and wheel will give and idea of speed I think, but one of the experienced guys may need to help. I haven't even got my build up and running yet. Good luck though

actually i've had several things from the UK shipped as they seem to have the kit to make a board! Alien Drive and Alien Power both are in the UK i believe.

Alien Drive (beetboks) has been a huge help and really knows his stuff.

The max weight (rider) of that setup looks to be 65'ish kg.

If you are comfortable with wiring/electronics - it's probably doable to get it going. Simply swapping the batteries will give you more run time. Going to lipo should work but i'd also make sure you have a good low battery warning buzzer and don't run them too low (damage = shorter lipo pack life). Motor mounts and replacement motors might be next and then you are basically starting over. Deck, How many "s" battery/voltage? - which ESC works? charger for lipo. Brakes (controller card to adjust). Runtime - how heavy is carryable/doable... slippery slope!!

Have you looked at some of the kits from ADS to see if it makes more sense to build it that way? Not cheaper, but definitely easier!

GL!

I'm up in Newcastle, there are more of us here than it seems!

There shouldn't be too many problems swapping out the SLA batteries for an equivalent voltage lipo pack. A lot lighter! Resist the temptation to go for a higher voltage as you don't know if the control circuitry will take it, and it could burn out.

Here are some of the cells i am looking at from my board from hobbyking:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=31952
and here is a voltage checker:
http://www.hobbyking.com/hobbyking/store/__74027__HobbyKing_8482_Lipo_Voltage_Checker_2S_8S_UK_Warehouse_.html
these things plug into the balancing leads on the battery packs and alarm if the cells go too low. They are essential, as if you discharge a lipo cell below it's minimum voltage (approx 3.2 i think) the cell is buggered and won't work properly again.

If you do order stuff from hobbyking make sure you leave the page for a while before ordering as a popup appears offering the item at a reduced price. This happens on all the pages, so patience is rewarded! also make sure you order from the uk warehouse to reduce lead time and shipping fees.

Wow, thanks for the replies guys! Some great info already!

Magiced - perfect, those batteries are really cheap! Thanks for the advice on the li-po's as well - I know lithium batteries are tricky b*ggers!

Easy-pd and sl33py - I don't actually want to swap the motor or controller - as I said in my first post, I'm actually quite pleased the motor and controller are working fine. It's the batteries I need to work on.

The seller had another board brand new in its box, but wanted twice what I paid for this one for it, so I bought the used one (I very nearly recommended him to get the board on charge before he sold it, but it's gone now - the batteries in it are probably knackered as well). However, I was able to convince him to scan the owner's manual and send it to me.

Predictably, it hasn't helped at all.

The other board is identical to mine, but the user manual seems to be for a slightly different model - mine is the SF-X (I'm sure now), whereas the manual is for the lower model, FT-1. As far as I can tell, the SF-X is more powerful, but I still have no figures. The FT-1 has a lower model number in its motor though - 51M versus 53M in my board (from the parts page). However, this also suggests the 53 is no indication of the motor's output power.

Is there any way to work out the motor power without a dyno? I put an ammeter between the batteries and held onto the drive wheel while revving it up, and I saw it hit >10 amps on the lowest speed setting - I don't have an ammeter capable of reading higher currents so that's out! No load is between 1 and 3 amps. There are two thick wires connecting the batteries in series, each with a 25-amp fuse soldered in the middle, so it looks like this motor can shift some quite serious current! For those fuses to blow, the motor would have to be sucking down 1.2KW!!

I guess I need to know what kind of power it's going to draw before I spec the batteries - I know if you try to pull too much current from a battery pack it'll heat up like crazy, and that is the LAST thing I want to happen with a sizeable amount of lithium beneath my feet. Obviously I COULD swap the motor for one with a known rating, but a) that's extra expense and b) seems like this one could be rather powerful!

hmmm... how about looking at it from the other direction...

No specs on motor and concerned about over-drawing the lipo's.

What is the model and specs of the "knackered" (great word) SLA batteries you are replacing? If you can spec your new lipos to meet what they would've provided i think you are safe - right?

I'll go dig a bit as i think you should be fine when your Amps shouldn't be too extreme. Just about any of the newer "high output" (10-20c) lipos i think will work. But there are some 40c+ batteries if you are really worried about it.

Over drawing the batteries would equal heat. I'm testing a new build and a single 200kv 5065 motor on 6 and 8s batteries (25.2v and 33.6v respectively) has only drawn around 30-40A (says my inline "watt meter"). I've peaked at 750 and 825w output says the meter w/ me going up a pretty steep hill in my neighborhood. While the motor got warm, the battery stayed totally cool to the touch.

To understand Lipo "C" ratings:
Formula: (C-Rating) X (AH) = Maximum Constant Amp Draw

So my Zippy Compact 8s 5800mAh (25c, 35c burst) = 145A constant, 203A burst. (5.8AH x 25/35c = A)
My Turnigy nano-tech 6s 8000mAh (25c, 50c burst) = 200a constant, 400A burst. (8.0AH x 25/50c = A)

Thinking that my motorcycle SLA's (still likely bigger/heavier) only provide around 300'ish CCA, so just about any correct modern generation lipo of 25c and better would more than suffice for general running. Generally.

I'd be really surprised if the ESC was able to pull over 100a constant.

my .02! GL and HTH!

I actually average 10-20amps more so and 50-60amps on the higher end for a few seconds on a dual motor 5065 setup.

Thanks for clearing that up sl33py, great help!

Remember what I said about the stock batteries being Chinese junk? Guess what, they're labelled in Chinese as well!! I could unsolder one of them and compare it to similar batteries on sale at my local Maplin store to get an idea, but I can't find anything concrete on any part of this board.

Gargravarr said:

Thanks for clearing that up sl33py, great help!

Remember what I said about the stock batteries being Chinese junk? Guess what, they're labelled in Chinese as well!! I could unsolder one of them and compare it to similar batteries on sale at my local Maplin store to get an idea, but I can't find anything concrete on any part of this board.

Click to expand...

Cool, hope it's good info to tuck away.

LOL - my mandarin sucks (can say hi and thanks), but what about option C... Instead of specs, let's look at similar size SLA batteries. They are usually very similar in CCA and dimensions and weight should get you into a comfortable replacement battery range. Then just determine if your lipo's exceed the draw and you should be fine. I did similar with my Buell 25R battery when i went to LiFePO4 (for weight and geek factor).

If i have the size/dimensions and weight i bet i can find a replacement battery, then you can be confident your lipo's aren't the limiting factor. Again i'd bet with modern high output lipo - your ESC is likely the limit and likely doesn't do more than 100A.

GL!

Well, I took the battery case down to Maplin at the weekend and their Yuasa 7.0Ah batteries are a perfect fit, so I'll assume the stock batteries are about the same power.

I'm wondering, from a cost point of view to get this thing working, whether there's anything to be gained from buying a pair of cheap SLAs first rather than throwing a large amount of money into the li-pos. I watched a 24V 10Ah li-po electric bike battery (with charger) sell for £160 on eBay - whilst it would have been a perfect upgrade for the board, it did have all the hard work done for me. I could also see about getting a 50A ammeter and measuring how much current the board pulls at full throttle.

The alternative, as I noted, was a few ni-mh drill batteries - would these be any good? My fear with li-pos is their reputation for fireworks; making them power an as-yet unknown electric motor with a sizeable current draw is starting to sound dangerous!! Ni-MHs are much more stable, but I don't know if they can handle the current draw of a big motor.

What do you guys think:
-Replace the stock batteries with equivalent SLAs to get the board running
-Chain a few 24V ni-mh drill batteries in parallel or
-Stop being a wuss, li-pos are the way to go if you do it right!

back to offer more of my opinion...

I think you are going to throw good money away on a crummy solution with either the NiMh drill batteries or SLA. SLA will work (it's what it had), but you are carrying a lot of lower energy cells (weight) for no improved runtime.

Go Lipo. They are not bombs and with some common sense and caution you get all the benefits (more run time, less weight, etc.). Stupidity is your enemy. Do dumb stuff and not listen to "common" sense - you will destroy something. The lipo if you are lucky - your shop/garage/house if you are especially unlucky and/or stupid. Don't leave alone while charging. check for damage/puffing/bad cells. Lipo bag or pyrex dish just in case.

If you want to do it somewhat cautiously - get a inexpensive 24v lipo (small'ish mAh) and one of the watt meters like i have inline. Measure and check for heat in the battery and ESC frequently during a ride. On the flats first, then some hills, etc. to make sure it's doing OK.

I don't think you will over-draw a modern lipo. i'd get some inexpensive 3s lipo in series to test. Do you have a lipo charger?

My shopping list for you:
Inexpensive ZIPPY Flightmax 4000mAh 3S1P 40C $26 x 2!
Watt Meter $24
*Decent* Lipo Charger $30

If you want a nicer charger i think that's where good money should be spent... The Turnigy "dlux" one above i think will work at it's only $30. So quite a bit less than the bike battery setup w/ charger (but also not 10Ah). If you setup your board with swappable batteries - even the lower capacity batteries you get here can be in your bag for extra run time/miles!

Right, thanks sl33py!

I just placed my order:
2x ZIPPY Flightmax 4000mAh 3S1P 40C
1x Turnigy MAX80W 7A Lithium Polymer Battery Charger
1x 4.0mm Banana Safety Plug With 12AWG Silicone Wire (4pc)
1x HobbyKing™ Cellmeter-6 Lipo/Life/Li-ion Cell Checker & Alarm
2x Trackstar Fireproof Lipo Storage Case (145 x 50 x 30mm)
1x In-Line Voltage and Amperage Meter
1x HXT Simple Lipoly Monitor 2S~3S

Annoyingly, the cheapest power supply for the charger is out of stock in the UK warehouse, looks like I'll need to order it in from their overseas one. Other things listed were also out of stock, so I've substituted ones that I think are equivalent (charger and meter). I also plumped for a couple of fireproof cases and some decent discharge cables to solder into the board's existing power connector.

Thanks for picking out the batteries for me, that 40C constant discharge rate suggests a maximum drain of 160 amps! Pretty sure you could arc-weld with that kind of current! And yes, they are extremely cheap. If this system works out, I might buy a half-dozen or so and run them in parallel to increase the board's range - with the size of these packs, I can cram a silly number into the same space occupied by the SLAs!

Will let you guys know (and post some photos!) when all the kit arrives!

Cool! can't wait to see how it turns out!!

Power supply... For quite a while folks have been taking server power supplies and converting them for DC charging. ridiculously stable and HIGH AMP output! Single (12v) or in series for 24v. The nicer iMax really like 24v and charge much faster.

Regardless - for a cheap PS that is far superior to most, as long as you don't mind "server room fan drone" from 40-60mm high RPM fans... A single 12v setup might work perfect for you and not cost too much even w/ shipping. (*used* can fail at any time... but being server specific - not likely!!)

Here's one on ebay. I'd look at your local Ebay and bet you can find one closer to you w/ the right plugs. If not, standard molex is easy to get in your plug i'd bet.

As you get deeper and deeper into the dark side... i'd also suggest picking a "standard" plug you want to use. I have boxes of so many assorted adapters and plugs... XT-90 is my current. I swap all my batteries to them now and eliminate the adapters when charging and using. XT-60 is another good option, but my old favorite were deans. Just my .02 that if you are doing it now i'd pick one and take the time to swap connectors on batteries you get. The new xt-90's with anti spark are pretty genius IMO and helped me move to them as my new standard.

GL!!

All right, photo time gents!



This is the board itself, with my 360 controller shown for scale. Bit of a beast, I think, although I've never seen another in the flesh.



The bits that make (made) it tick, again with the controller so you can see the size of the motor.



Big box of fireworks - 'DANGER! LITHIUM BATTERIES!!'



Unpacking - 2x li-po packs with cases, charger, banana connectors, mini-alarm, mini-green/red cell monitor and in-line volt/ammeter.



The more observant will notice I didn't get a power supply for the charger - they were out of stock (Murphy's Law...) when I was buying, so I've ordered one from HK's 'International' warehouse. In the meantime, I realised the charger comes with a pair of crocodile clips and is clearly meant to run off a 12V battery - neat! I can put the SLAs to use! But first, let's see if there's any juice in the packs:



A good 11.6V! How about the other?



Snap! I also put the monitor/alarm on both packs and it reported the same, with a max cell variance of 0.035V for both batteries, so I assume this is good!



The first hurdle. HK didn't make it clear that the connectors for positive and negative are opposites! Also, only the positives from my pack of banana connectors are actually usable Damnit. So, before rigging all this up properly and taking it out on the road... erm, pavement... I'm going to have to get some proper connectors for the negative.



Got the soldering iron out and desoldered the wiring from the SLAs, then soldered in the inline volt/ammeter and then one of the banana connectors.



Moment of truth!

And this is where we are at present. When I touch the negative to the battery (done so twice), I get a pretty impressive spark, and that's with the board's controller switched OFF. Should this be happening? I don't want to connect them again until I know it's okay. Last thing I want is for something to short out and the first test of this whole rig is the fireproof cases!!

Am I doing this right?

Edit: okay, with regards to the whole battery-connectors/banana-plugs thing - looks like I totally misunderstood. The batteries have 4.0mm HXT connectors. Sl33py - I just put in an order for a batch of XT60 gear, including adapter cables for the batteries. Looks like 60 amps will be more than enough for this rig. I'll remove the original connectors from the ESC power cables and fit some XT60s instead. I guess I can try to re-use the banana connectors for charging.

Nice!! in series 24v i'm not surprised you are sparking. That's normal from what i understand and what my lower voltage 6s pack does as well. That's why i use the xt-90 anti-spark plugs for my 6 and 8s setup - they work great to avoid spark.

Can't wait to hear your report after the first ride. GL!

Just in case, hope this is how you have yours wired in series:


might be repetitive and something you already know.

I was more wanting to know if it should be sparking with the board's power switched off, especially since I can't see any obvious shorts or crossed wires - could it just be to do with the voltmeter? Again, I really don't want to short this thing out and be left with a smouldering crater where my board used to be...

And yeah, don't worry, I remember high-school physics I bought a 2-into-1 series cable to neaten the wiring. My original intention, as you might have spotted in the photos, was to plug the batteries together, but obviously I drastically misunderstood the connectors, so now I'll do it properly. Got another box of wires on the way, and if this works, I'll consider adding another couple of packs in parallel to boost the range.

Still can't get over the fact that my charger has a USB port, though!

Those red plugs on the lipos, I just cut down the joining part with a Stanley knife so that the + and - were not joined. I then was able to connect the two packs in series.

Okay, progress.

I got it working



I ordered some HXT-XT60 adapter cables plus some XT60 plugs and sockets. I painstakingly removed the original power connector and soldered on an XT60 connector instead. I also soldered XT60 plugs to the volt/ammeter, so I can disconnect it if I don't want it.



It works! After this, I bolted the carrier back to the board and took it down to the local park. It has way more power now than with the dying lead-acids, and is quite a few KG lighter. Most of all, it has uphill performance now! I even got brave enough to put it in second gear, and that was fast enough to be scary

Predictably, on the journey back home, the batteries ran out. They went pretty quick, too - little warning before the board was unable to power itself. This is a characteristic I'm going to have to watch for. I would like to put a power meter at the toe of the board - the original location on the side of the carrier is totally invisible while riding!

At present, I don't have a mains lead for the charger. The only thing I have capable of supplying 12V at 7A is the car; fortunately I bought a cigarette lighter cable with the other adapter leads, so I'm going to go run a fast charge. I'm also using the old SLAs off the board in parallel to begin the charging cycle.

Oh, and guess what - when I came home, I noticed a small hand-written sticker had fallen off the board, must've been on the motor. It says '350 / 24', which must mean 350W / 24V, so I finally have my motor rating Pleased with that, boards in that power range are about 4x what I paid for it! Max current draw will be just less than 15 amps by that logic.

Some charging questions about li-poly:
-Max charge current would be 1C == 4.0A, right?
-I have a parallel charge board. If I use this, I can wind the charger up to maximum (7.0A) because the batteries are in parallel?
-Is there any point using the charge capacity feature of the charger? Whenever I set it, the charger starts counting from zero; it doesn't seem to pay any attention to potential charge already in the battery, so should I just trust the voltage?

Finally, I couldn't find any on HK, but are there any convenient connectors I can get to bring the charge connectors out to the side of the carrier instead of taking the whole thing to pieces each time? It's not a convenient design from the start, so if I can mitigate it a little, it would help.

Nice! Looks great gargravarr.

Charging - 1C would be 4A. Those packs will support up to 2C (8A).

Did you get a parallel board to charge these at the same time or do you charge them independently? My favorites are usually like this one from epbuddy


Did you look at any of the 12v server power supplies on local/UK ebay? Also, anyone who has access to older HP and Dell servers - their power supplies (modular/swappable) make GREAT DC Power supplies (12v only). Going to try that next, a pair of them and possibly in series for 24v. Loud fans, but basically free from work!! If you are willing to tinker a bit. Cool writeup on this - http://www.tjinguytech.com/my-projects/server-ps

Here's a cool charging speed calculator i use:
http://www.csgnetwork.com/batterychgcalc.html

It looks like you have room for two more lipo packs! that in parallel would double your range. Did you setup a low battery alarm to avoid over-drawing the lipos? I recommend one for sure if you don't have a readout to monitor while skating.

As for charging them in the board - you could use simple extension cables for the balance plugs, but you'd still need to disconnect the batteries to charge them in parallel or individually. In series would only work if you charged them with a combining balance plug to 6s. I think that would work!

not my strongest area to help, but also found this adapter that *might* work:
http://www.hobbyking.com/hobbyking/store/__10993__Twin_pack_charge_lead_2_x_3S_6S_w_XT60.html

here's a 6s extension if the above worked.

http://www.buddyrc.com/12-6s-jst-xh-extension-cable.html

Alternative to the above, HK has 3s->6s:

http://www.hobbyking.com/hobbyking/store/__9910__2_x_3S_gt_6S_Splitter_JST_XH_5pcs_bag_.html

they also have 8" and 12" 3s balance extensions:
http://www.buddyrc.com/catalogsearch/result/?q=3s+balance+extension

You could get two more lipo's to do 6s2p, and then two 6s extensions w/ two plugs to parallel charge.

I don't mind pulling my batteries to charge (i want ease of access to swap and double range). If you want to do this *right* - BMS (battery management system) is the way to go. I'd look at torque or onloop's offerings. In your neck of the woods you could check out APS. I had a horrible experience with APS and don't recommend them, but they are local to you...

GL!!

Well, I was able to use the board only once more last week, and again it ran out very quickly about half a mile from home. The hills must be killing it quickly, but at the same time, I was expecting >10 miles range with the 7Ah stock batteries. Sure, these have gone down to 4Ah, but I would hope that would mean 6 miles? I'm not even making 3. The weather this week hasn't been cooperative at all, but I've made sure this time that the charger says FULL before stopping the charge. Both batteries hit the capacity cut-off (4,000mA) on the charger after the second run-flat, so I put them on a second time and coaxed another 160mA or so into both of them - I assume this is normal? Thankfully, neither battery has demonstrated any heating during charging, and I'll stick to 1C or less.

I am entertaining the idea of buying another pair of 3S Flightmaxes, although now I have the expected current draw (based on the motor being 350W), I no longer need extreme discharge. In theory the motor should never draw more than 15 amps, so I could go with a lower-C, higher-mAh pack. So the dilemma is - do I buy another 2 identical batteries and make do with 8Ah total with a totally overkill 320 amps of continuous current available, buy a pair of high-stamina/low-discharge batteries and charge them separately, or buy 4 high-stamina packs and totally replace the electronics already?

I do indeed have a parallel board, although I think it's safer to balance the batteries individually after a deeper discharge. The lowest the cells got was 3.1V the first time, but they're holding 4.2V now. I'll use the parallel board when the cells are more or less balanced. Thanks for the link to the 2x3-into-6 adapter though sl33py, that looks like a better option! Annoyingly out of stock, naturally, and I have another batch of things I want which are all out of stock, so I'm waiting to place another order.

Does anyone have any recommendations for charge controllers? I want to be able to just hook one (max 2) connectors into the side of the carrier, plug into the mains and leave it to it. Consumer products with li-po's have this ability (yes, I know, there is a lot of electronic monitoring, but surely this could be fitted to the rig I'm running?). Also, how about a decent 24V power meter I could surface-mount to the top of the board so I can see the battery state? Bonus points if I can tweak the 'low' range to the voltage where the board's controller essentially cuts off (which is well above 3.0V per cell, probably just under 3.5V based on the alarms, so 21V-ish?).

Getting there... although it really is doing a number on my feet!!!

Parallel board works great and/or just 6x parallel charging connectors and balance plugs for your S series pack.

I'd suggest iCharger 208B or higher.

I wouldn't ever leave LiPo without checking it while charging which is why I prefer to use an iCharger and charge at 15amps at least with (4) packs. Usually, wash the dishes or on the computer and it charges when I'm back.

You don't leave them charging without supervision due to the chemistry of lipos and what happens to them when they are overvoltaged - in case the charger does fail which is most likely more prone on cheaper $20-$30 chargers.

Just my 2cents.

Hmm... How about you look at it differently.

$ per Mile maybe? You have a *very* inexpensive setup. with only 3 miles range. (a lot of hills - have you tried max distance in the flats?).

Now compare a $1500.00 - 6 Mile Boosted... Before tax/shipping/import duties, etc.

Also - you know components and can replace to extend, or carry extra batteries and swap for more range.

It's easy to dive into replacing everything, but if you carry some spare batteries to get more range, would that work? Definitely save some $!

To your question though - I don't know about the 7Ah = >10mi. That might be a claimed range with a slight downhill and tail wind... marketing! Unfortunately i'm not the sharpest tool when it comes to building efficient setups like others here. So i can't help much with getting better range. I know motors have a "sweet spot" and if you hit that you can extend range, but i believe it also typically sacrifices lower end torque which is what i'm after (i'm a big guy).

I'd prefer to look at given range for existing mAh batteries, then adding batteries to get the range i want. If the startup and hill torque power are there - going all-out for range may impact those attributes which i consider more critical. I don't mind carrying an extra set of batteries and as an added bonus, when the first set runs out, the replacement set should get me home (automatic halfway point)! Unless it was all downhill...

I'd try getting more mAh. In parallel for higher mAh under the board, or in your bag and swap. Going down the path to all new electronics is a slippery slope.

hard to go wrong with iCharger models. with Torque on that as usual. It's an investment, but they work *really* well. I like the IR (internal resistance) measurement as well to gauge life of the cells.

GL!

Quick question - I bought a pair of 5,000mAh Flightmaxes and ended up using them (before giving them a full charge) when the board ran out about half a mile from home on Friday. Although I didn't use them much, I think one of them is giving me trouble. Whilst one of the pair charged up fine, the second is resisting charging beyond 3.98V in its third cell. The other two cells are at 4.18V and 4.20V. The charger gave up after 3 hours; I've put it on again, and it's been trickle-charging at 0.1A (or less) for nearly 2 more hours, and the third cell isn't crossing the 4V point. Does this mean the pack is defective, or is there a way to persuade the third cell to charge fully?

Sounds like the pack is damaged. How, could be damaged when you received it. From running the pack. Could be countless things perhaps.

Seems dead to me. You can try to repair it by charging one cell but i haven't done it.

Usually, I just chuck it as a lost and get a new pack. Could be your charger. I think this happened to me when I ended up running to low voltage. One will end up sagging faster than another and won't come back up to a full charge.

I do recommend the iCharger.