AM dual motor = bafang middrive + rear hub motor

[John Bozi]

If I'm pulling 40-60 amps from a 25-35C 5.8ah 12s 1p battery what is the % of chances it will exceed its limit and explode into flames?

I have heard the actual c rating is about half what they state.

so lets say 12C x 5.8 = 69.8amps

or if capacity is more conservative 12 x 5ah = 60amps.

I am still below just below but in reality pushing the limits of the battery.

I also understand first hand all the advice Pendragon was giving me about the voltage sag now. I understand that I can't use the most the capacity because of the sag.

I set the CAV3 low voltage limit to 39v (3.25v x 12s) - does the cav3 cut the power completely or does it ramp down at that limit? I only saw a flashing V symbol momentarily at 38v so I rode back softly letting the volts creep up to 42v something.

 

[John Bozi]

Still got blisters on my hands, mate oldhack calls up to do the dam circuit - can't turn a ride down.

flying along the track, with a poorly mounted headway pack (took off because I was using lipo, but put back on hastely to go for a ride), so had to concentrate on balancing it between my legs, didn't judge some very deep dried old 4wd tracks hit them at high speed and hit the dirt wrists sprained, then head hit with full face helmet thank god as the gouges on the helmet and one big cut across my temple, grazes on my knees and elbows and general light grazing along my arms bruised thigh.

Probably the worst fall I have had in mtb or emtb.

wife wants to kill me.

gave the sick battery to oldhack,

im going to the shops for pain killer.

just hope cut on temple doesnt get infected as I ate the dirt.

frocken hobby

 

[pendragon8000]

Still got blisters on my hands, mate oldhack calls up to do the dam circuit - can't turn a ride down.

flying along the track, with a poorly mounted headway pack (took off because I was using lipo, but put back on hastely to go for a ride), so had to concentrate on balancing it between my legs, didn't judge some very deep dried old 4wd tracks hit them at high speed and hit the dirt wrists sprained, then head hit with full face helmet thank god as the gouges on the helmet and one big cut across my temple, grazes on my knees and elbows and general light grazing along my arms bruised thigh.

Probably the worst fall I have had in mtb or emtb.

wife wants to kill me.

gave the sick battery to oldhack,

im going to the shops for pain killer.

just hope cut on temple doesnt get infected as I ate the dirt.

frocken hobby

Sounds like you'll be OK in a couple weeks. Smash the neurophen. But take it easy on the piss if you do cos it Cains ya guts.

 

[biohazardman]

Ouch! If it were not fer bad luck you would not have any at all? Only one crash in 15K, on the e bikes, for me and in several inches of snow so a bit more padded of a landing. Hard to be careful when you are having fun until you are so beat up you know better or run out of fun. Take it easy and heal up better this time before you do any more damage. Take care.

 

[John Bozi]

ah the pain is ok, mostly hurts holding my daughter as she scratches into everything she touches.

I had a great test ride with remaining Lipo today.

two healthy batteries (was over the headway falling all over the place)

I dont know if my settings are wrong on the cav3 but it read 2.7 for a ride that is usually 4ah,
sure I pedalled a little more at start but not that much.

Plugged in the cell monitors for my ride to oldies and back and its seems Id have enough to do it again,

resting voltage was about 45. something, when I returned.

3 batteries need soldering and one is being replaced and on its way, and have two chargers now for the power supply which can deliver. Lets see how it alll goes, maybe not so bad after all.

 

[John Bozi]

[youtube]1w24EuTBzpo[/youtube]

second attempt at riding with lipo

 

[John Bozi]

Can some explain why I can't charge @ 18v @ 10amps a charger?

[youtube]eqdkJjvqR0k[/youtube]

 

[deffx]

Nice video John, what a clean work area, i would show you my chaos but id be embarised

I think your charger draws up to 250 watts to do its magic, example 16volts at 250 watts = 15.625 amps

So your really on the limits of your psu to drive two of them chargers at there max ratings as its a 540w psu

Your better off in the long run sticking around 16 volts and charging at 8 amps

Trying to deliver 18v which is the chargers max, is asking for trouble, i doubt your psu is large enough or stable enough to deliver a good clean constant 18v, especially under fluctuating loads of charging when both chargers are drawing current intermitantly

Something will give out, the psu or the chargers if you push them to the edge and cost you money

Hope this is correct, helps and makes sense, its early and im hungover :-]

 

[John Bozi]

Nice video John, what a clean work area, i would show you my chaos but id be embarised

I think your charger draws up to 250 watts to do its magic, example 16volts at 250 watts = 15.625 amps

So your really on the limits of your psu to drive two of them chargers at there max ratings as its a 540w psu

Your better off in the long run sticking around 16 volts and charging at 8 amps

Trying to deliver 18v which is the chargers max, is asking for trouble, i doubt your psu is large enough or stable enough to deliver a good clean constant 18v, especially under fluctuating loads of charging when both chargers are drawing current intermitantly

Something will give out, the psu or the chargers if you push them to the edge and cost you money

Hope this is correct, helps and makes sense, its early and im hungover :-]

I've actually spent hours downstairs now, waiting for things to charge so in the meantime have tidied up. Having said that, I prefered having my crystalyte charger shelf next to bike and power point. That was easy. It's a pain to pack away all these bits all the time now. I can't leave them lying around in the carport, so the only other option is the laundry. The laundry if far from ideal for charging. Water & electricity in the same room makes me worry when charging. At least is built in asbestos fibro walls and ceilings for fire protection. It's the only room away from my family... I will get more tiles on the table soon.

The chargers are only capable of 10amps. 10amps x 18v = 180watts. Why write 250w on the specs? I guess the 70 watts are lost to safety margins of about 4amps. Anyway as you say lower and slower is safer and should last longer. cheers & bon appetite at the same time.

hair of the dog, I used to hate bloody Maries, but Im hooked on them once a week, and today it's hot and sunny 8am feels like lunch time, and lunch time is a good time for a drink that tastes like food.

 

[deffx]

[youtube]1w24EuTBzpo[/youtube]

second attempt at riding with lipo

Great commentary

"No entry my arse" LOL

Not sure how many amps your controller is set at, but its probably asking alot from just two parralleled batteries

The more you parrallel shares the load between them, i usually run 6 or 8 and they barely warm up

I like how you love the lightness and manuvrability though,

Its a fine line of how much weight and range to have, lighters always nicer, i notice the difference just between adding a couple of extra batteries

And that "POP" when you plug in can be eliminated useing a Pre-charge resistor set up

thanks for the vids keep em coming

 

[deffx]

The chargers are only capable of 10amps. 10amps x 18v = 180watts. Why write 250w on the specs? I guess the 70 watts are lost to safety margins of about 4amps.

I think your looking at it wrong, they can deliver 10 amps to the battery, but to do this magic of converting the input voltage to the roughly 25 volts at 10 amps charging current requires the charger to draw up to its 250w rating, rough calculation each charger requires 15 amps at 16 volts from the psu

 

[John Bozi]

Thanks dffx

I got a whole bunch of pics of the bike in this public album, couldn't be bothered adding all the pics here...

Not Safe For Work :lol:

 

[John Bozi]

I like how you love the lightness and manuvrability though,

Its a fine line of how much weight and range to have, lighters always nicer, i notice the difference just between adding a couple of extra batteries

It is the first time I have felt it feel like a bicycle. The weight is a big thing for me. I don't mind riding bicycles and pedalling. I don't like pedalling hills though and getting out of breath. Those two little packs actually have a much longer range than I was thinking. The leg space is a fraction thicker than a bicycle because of the controller, and the two batteries is less than 2kgs mounted forwards and lowish. I need exercise.
I have ridden it across to my parents place and down to the shops on the same battery charge. I try only ever use 2000w if I need to climb a big hill, or say escape traffic or something.

I'm actually starting to think I bought the wrong motor for most of my rides. Don't get me wrong I would like to get a speed machine happening, too.

I think a geared hub would suit my local rides much better. More efficient for freewheeling. The drag and weight of the 4065 seems wrong for a two battery set up.

I don't even need a cav3 to monitor temperatures if I am going to be peddaling most the time. I can just gauge everything I need from the cell monitor alarms.

 

[deffx]

I'm going to try bafang bbso2 mid drive soon. On a lighter bike.

Don't want the weight of the motor in the wheel of road

 

[nicobie]

surprised the customer service @ hk is so good.

Why is that?

 

[John Bozi]

surprised the customer service @ hk is so good.

Why is that?

Read a lot of bad comments about it. But they were real quick to replace my battery. I checked the new one today and she looks perfect.

deffx = Ive studied up on those bafang 750w - I just wonder how long they can sustain that power.

I would love to get a proper downhill bike and bomb around on the single trails with something that doesn't take away from the experience and the weight of most electric bikes does.

I've thought about having multiple booster packs. Use one to get to the tracks, one to fly around on them a bit, and another to get home.

In a really good back pack 2kg is hardly noticable.

Main worry is will it have enough clearance for off road riding, and is it tough enough for knee height drops.

 

[deffx]

Main worry is will it have enough clearance for off road riding, and is it tough enough for knee height drops.

Well the clearance will just have to be something your aware of, and log crossings are probably out

Tough enough, who knows, probably not that great being chinese, i havent heard of any one breaking or bending a crank yet though.

For mild trails and foot high drops im hoping its ok as thats about my limit at 44 years old and a year since I broke my neck and back

I like the fact it is happy on 48v, keeps thing simple

I see you asked Kepler his opinion and will be interested in his answer, i think it will be the answer for mild single track riding, no big motor in the rear, and I am looking forward to the PAS. My mum and dad have PAS bikes and its awsome, makes you feel bionic

I have not ordered yet, but i will soon once christmas is out the way, i got 6 kids

 

[John Bozi]

Main worry is will it have enough clearance for off road riding, and is it tough enough for knee height drops.

For mild trails and foot high drops im hoping its ok as thats about my limit at 44 years old and a year since I broke my neck and back

I have not ordered yet, but i will soon once christmas is out the way, i got 6 kids

ouch, every time I have a stack, I say out loud "I'm too old for this shit". I had enough big jumps and stacks when I was kid, I don't need them now.

I don't plan to do big jumps and we actually have some huge ones not far from home. I got A kid, enough for me and it puts a different perspective on doing risky things. A few people have died on mtb on trails I ride, which would probably be better than spending life in a wheel chair right, having people change your nappies and feeding you.

My last stack brought it home to me again, that was on softish dirt. It makes me often picture as I'm riding on bitumen much faster what would happen. I've come off on bitumen at slow speeds and it took ages to grow back skin so that I could even have a good nights sleep...

 

[pendragon8000]

hey man just watched your charger video.
so i think the amps thing goes lik this:
17v x 25 amps = 425 watts from psu
each charger gets 212 watts puting out 25v = 8.5 amps
the system would be less than 100% efficient though
charging at 8amps is fairly quick and is about a safe healthy limit IMO

 

[John Bozi]

Why are the first 3 cells slowest to catch up to the desired voltage on charge and usually never get to the same as the cells 4,5,6?
Similarly why do the first 3 cells get used up more than the last 3 cells?

My cell alarm hit 3.25 momentarily, although this morning when I connected the batteries to charger, after no use, lowest was 3.5v

How much does the monitor suck out in 24 hours?

[youtube]L71V_dpds1w[/youtube]

 

[John Bozi]

great short exercise ride this morning. About 30 minutes.

Up looked like this:

down the mountain bike single trail looked like this:

Coming home looked like this:

I have to come back up the mountain that I single tracked down on.

I was happily surprised with how balanced the cells were at the end of the ride. Almost all of them were on 3.75v. The pack was just mildly warm. Temperature outside is about 30 degrees celcius though.

 

[John Bozi]

As I was charging for this mornings ride I recorded this:

lighting on the display I have to remember does not like showing up on film.

basically first 3 cells and last 3 cells had lots of difference, which is different to after the ride (I didn't drop below 43v - which might be the point at which things start going pair shaped or maybe the more the battery is used the more it is balancing?)

[youtube]FwCsnNyevfw[/youtube]

 

[deffx]

Interesting observations John, i dont know the answers, hopefully someone will pitch in with the answer.

Its a shame your thread isn't in the ebike section, as the majority of people on here probably only browse that thread, and heaps more people would view your posts and you might get more knowledgable replies. You may be able to get a mod to move it, maybe to photos and videos

I have similar issues with my batteries, low cells on one end, they are getting real bad lately, im loosing the odd cell to, i had put it down to old age and abuse, the hot weather lately and being zippys. Also i charged to 4.2v and quite often twice or more a day. also had a few sparky moments, sometimes i bulk charge, my bc168 also got fryed and i continued using it. All the above i figured contributed to fuking them up. Ill do better next time

I bought the cheap 20c zippys, i here the 40c turnigy's are supposed to be the best. I have some 3 cell 40c zippys which are perfect, wierd shit

I need a new battery solution, but my weird box is difficult to fit normal square preconstructed batteries in. So im kinda stuck with modular lipos

Was looking at the 4s hardcases this morning as im a cheapskate but that will be even more spaggeti wiring.

hopefully yours get better with a few cycles as they are new

I also seem to remember (but i might be imagining it) people recovering rc model lipos by discharging and balance charging really slow like 0.5A . RC forums are a huge resource on lipos

 

[John Bozi]

You may be able to get a mod to move it, maybe to photos and videos

done - thanks for the suggestion, you go to 4.2? I am bit scared and only go to 4.17 (usually means half at 4.17 half @ 4.15 & up out of the drive way and to my first turn off my street I've lost the surface charge.)

anyhooo

Finally the video of the above 3 photos ride uploaded. BIt boring - as I realized my wrist is still feeling the bumps too much and went very slowly.

Lot slower than I am used to but hey, I pedal until out of breath and let the motor do it until I regain oxygen, or if a big hill is coming I don't pedal until I get to it as I will need full energy for it.
[youtube]7WhyjjAz7rk[/youtube]
Down the single track only used the motor for about 10 seconds...

After I got home and recharged the battery I had a few shopping things to do on it, was to lazy to do anymore pedalling - gunned it to the shops and back twice on one charge. That's cool!

If I ruin these batteries because they are not in parralel, I don't really care - if I get about a year out of them, I'll be happy.

I wonder what a 4 pack on the back feels like...

 

[John Bozi]

Would it be stupid to have both a mid drive and rear hub on one bike?

you could use the middrive to get you up to the best operational speed of a high speed hub which would give you the non pedalling end of the ride. If a mountain turned up you'd have both to help. It would help in not overheating either as you could alternate them if need be.

- extra weight / double maintenance
+ gearing / less heating /back up system if one failed / less stress on both