veloman wrote:If you don't want to go above 25mph, get the 10T. The 8T will handle the 8-10% grades okay, but there's no need for the extra speed (30mph) on 48v, if you only want 25mph top speed. Better to have that extra torque.
And I can guarantee you that you will be blown away how much faster off the line and up hills these geared Mac motors are than a basic DD on the same 'commuter power' of around 1000w.
o00scorpion00o wrote:There are new clutches on the way, though you might have to wait a while. They can fail. Mine did by running far more power than I should have been!
o00scorpion00o wrote:The battery is also a good choice, though you might find 11.5ah a little on the low side if you are riding up a lot of hills, depending on how much you are willing to pedal, and how far you have to go!
dogman wrote:But in fact, a 72v 20 amp controller on your existing motor might make you very happy. You won't be crazy fast, but fast when it would fit your needs, like approaching those steeper hills.
If your battery can handle it, just upgrading your existing voltage to 40 amps will perk up the hill climbs too. Nothing you are doing requires special stuff unless it's a really long 15% grade.
dogman wrote:Your real reality check is this. Upgrade your bike first. Get a nice full suspension frame, or complete bike if possible on the used market. It doesn't have to be a DH monster bike. Just a decent suspension bike with a fork better than a cheap pogo stick. The bike might cost more than you planned for a choice one, so you might need to ride your existing kit another season.
dogman wrote:Replacing just the motor with a Mac 10t or the 2810 9c would get you up those hills better, but you will not hit your target speed of 25 mph unless you run more than 48v with the slower motors.
veloman wrote:Regarding motor temperatures, I see very little mentioned about ambient temperature. It makes a pretty big difference, even 65 vs 85 degrees F. If I run my 8T Mac at full speed on 1200watts on fast roads, it won't get warm at 65 degrees temp outside for at least 10 miles. If it's 85+, then the motor can't shed it's heat nearly as well.
So, your climate has a big influence on how much you can push your motor too. Although, at ~1000w, I'm told then handle it fine even in hot weather. Lots of variables though. LOTS.
veloman wrote:Regarding motor temperatures, I see very little mentioned about ambient temperature. It makes a pretty big difference, even 65 vs 85 degrees F.
Joe Perez wrote:My primary concern in mentioning the battery was in whether the 11.5Ah battery using a 30A-rated BMS would be sufficient for a controller operating at 30A. In other words, am I likely to damage the battery or BMS by subjecting it to a continuous 30 amp discharge? (see next section of message for why I am particularly sensitive to this concern.) It's well within the specified c-rating of the cell themselves, and assuming that This is the BMS used in that pack, I believe that the notation of it having a "50-80A Protection Current Rating" means that there will be a sufficient margin of safety (and I'd likely fuse it at 35-40A anyway), I just wanted to ensure that this specific area was not a cause for concern.
Joe Perez wrote:It would be nice if it were fast (I very much enjoy being able to pass the more serious-looking Armstrong Jr's on the uphill sections) however it would be devastating if I wound up with something that was very fast on the flat sections and yet unable to scale the hills that I really need it for. So if a 10T motor is ballsy enough for the climbs, then I'd pick it over a 12T. But if a 12T is what I really need to make the hills without destroying the motor / controller / battery, I'll gladly sacrifice top-end speed for that.
chroot wrote:Here another MAC 10T tested by Hightekbikes at 20% grade hill in SF so 12T will be more faster climb up the hill at ease than on 10T MAC. Here the video show
GMUseless wrote:If you are staying under 60V, you really don't need the 4110 fets...the 3077s will run better (less heat) at that voltage....and they cost less.
o00scorpion00o wrote:cell-mans triangle battery and bag might be worth the extra money if your triangle can take it ?
o00scorpion00o wrote:How would you feel about LiPo ? IF you don't know much about it I would stay clear, but the reason I asked is because the 12T would probably give you only 15 mph on 48 volts, so I would go with 60 volts.
o00scorpion00o wrote:The other thing about the 10-12T is how fast will it actually go up the hill is what you need to ask cell-man or someone who actually has those motors, you might find that 48 volts is awful slow while climbing!
Something to consider for sure. I'm not sure what the single-block BMS options for such a battery would be- I need to figure out with certainty if the series-BMS idea is valid. Two 39V packs in series would really be something.Lebowski wrote:If you want speed and hill climbing, get a 12T and a 80 to 100V battery.
dogman wrote:Very true. Most of the people I have steered towards the 2810 9 continent are running them at 72v, and very happy with 30 mph top speed. And even happier when they have a steep hill to climb. But if you run that motor on 48v, it's too slow for most people, at 19-20 mph. It definitely will climb 15% without any problems, even on a lame 48v 20 amps.
dogman wrote:The advice about making a really good bike the first priority remains. The rest is an easy solve, the only problem is deciding which slower winding motor to choose, and what voltage to run.
Joe Perez wrote:GMUseless wrote:If you are staying under 60V, you really don't need the 4110 fets...the 3077s will run better (less heat) at that voltage....and they cost less.
Well, I'd like to leave my options open for the future. And, to be honest, the difference in efficiency between the 4110 and the 3077 should be so trivial as to be immeasurable.
Looking at the International Rectifier's datasheets for the two devices, the 3077 has a maximum steady-state RDS(on) of 3.3mΩ as compared to 4.5mΩ for the 4110, and the VDS / ID and recovery curves appear virtually identical. So if we assume a constant 30A load, then in a worst-case scenario the 4110 would dissipate 4.05 watts at a forward drop of 0.135 volts vs the 3077 at 2.95 watts at 0.099 volts. (Granted, current in a polyphase inverter is not steady-state, however I assume that the operating frequency of the device is so low as to be functionally indistinguishable from DC to a device whose rise and fall times are well under 100ns, and whose dynamic properties are specified in the Mhz range.)
I think I can live with 1.1 watts and 0.036 volts.
GMUseless wrote:OK, I've got to admint I haven't done the math on this one (like you did!) I was re-stating what seems to be the conventional wisdom here posted by many of the gurus...such as: viewtopic.php?f=31&t=19587#p357997 and http://www.endless-sphere.com/forums/vi ... 45#p142287
Joe Perez wrote:I specialize in the Megasquirt family of ECUs
pwbset wrote:I sometimes dream of ditching my single Solex progressive carb in my '72 VW bus and throwing an FI megasquirt system in there as others have done. *sigh* Too over my head for now I'm afraid.
GMUseless wrote:Thanks Joe. From your first reply, I indeed assumed the magnitude of the losses (though 25%) must be quite small. But what isn't quite small is the amount of heat generated from these controllers. That's indeed quite sensible. And at face value, you'd think 25% of that would also be significant.
Users browsing this forum: jbalat and 15 guests