48v battery life

[cware05]

Hi I have posted a few times,built 6 low budget bikes broke all of them never managed to exceed 32 mph on power alone due to battery and motor shortcomings but i now have a reasonable set-up and some average batteries to play with.

all I need at the moment is one of you clever chaps that listened at school in maths lessons and has battery experience to give me a little hand .

my set-up is as follows:-

24v brushed 180w rear hub motor
48v 10a lim2co something or other (light lithium but i can never remember it)
36v controller with brake cut off and pedalec sensor

it has no guts off the line without massive help but pulls very satisfyingly above 25mph on power only on the flat.

I have 3 quite straightforward questions to help me make my mind up on my next move please.

the battery charges to 54.6v constant volts and amps according to the charger and leaves the garage at this voltage and after a 10 mile full throttle blast on/off road it is down to 48.5v .

question 1, is this my limit of drain or am i killing the pack at this level or by going further/should i leave the pack on charge whenever it isn't being ridden or just till the green light comes on?

my last 2 brushed motors ceased quite dramatical in clouds of nylon dust from exploded gears in the hub or the brushes arced themselves to death yanking segments out of the commutator.

so question 2, I can get a fairly cheap geared brushless rear hub motor(gng)£130 inc kit and post but not sure what voltage to go for they offer 24v 350w or 36v 350w and I will run the 48v pack to get the speed boost i crave but need suggestions on the voltage ?

last question if your not rolling your eyes and growling yet I also have a lithium ion 24v 8a pack in reasonable condition,can i run this in series with the 48v pack I mentioned earlier to get 72v,or will the imbalance in voltage and amperages cause one to suck the life out of the other or overheat or something (only a general enquiry as you cant see or touch my pack and i am rubbish at describing stuff correctly as borne out by my previous posts responses.

I am 6'2" and 17.5 stone on a good day and pedal fast and hard often averaging 15/16mph without power anyway but want to keep up the 25mph sort of area if poss not too worried about more than 10 miles range as i just pedal home anyway.

thank you in advance for even taking time to check over my ramble.

 

[dogman dan]

Your distance at speed for a 48v 10 ah pack is spot on with my experience doing similar speed, 25-30 mph. In fact, I'd expect less from brushed motors, more like 8 miles. Slowing down to 20 mph would extend your range.

You could series connect your 8 ah pack to your 10 ah pack. You would only have 8 ah, since the smaller pack would be your limiting factor. Charging would of course be by splitting back into a 48v and a 24v pack, so nothing bad would happen there.

You'd need a 72v controller. And very likely overvolting that particular motor to 72v would damage it, if nothing else, it might tend to burn down your brushes fast, and pit the commutator. I don't know that from experience, but another member here years ago found that over 60v wore out his brushes in no time. He was using Aotema or Cyrtalyte brushed hubmotors. Once the motor overheats, the brushes start burning. I've done that myself to many many saws and sanders that had motors too small for what I was putting em through.

Your best bet for real speed start with a good solid bike, strong frame with good lateral stiffness so you don't get the death wobbles. Good brakes, if rim brakes have em set up good, with quality pads.

Then a generic brushless hubmotor, 72v batteries capable of 40 amps continuous, and a 72v 40 amp controller. With 26" wheels, that generally just barely gets you legitimate membership in the 40 mph club. With smaller wheels, a fast winding motor is used to make it still go 40.

The motor will melt used this way, unless you spend $$$$ on more powerfull models. But generally if you only carry 10 ah of RC lipo battery, you run out of juice just about the time you should stop, about 10 miles or so. So keep the ride short and fun, and you won't melt motors.

 

[energyi]

I am 6'2" and 17.5 stone on a good day

For those who are stones challenged, 17.5 stones = 245 lbs = 111 kg
and 6'-2" = 1.88 m ~smiley~

 

[cware05]

OK 72 volt on the bike both battery and controller but i have opted for a crank mount kit from the same supplier a 48v brushless gng kit running through my 7 speed rear wheel and it seems to be very promising so far smokes the crazy bobs on pulling away and 32 mph on the flat after running out of gears so I am looking into a different rear cassette 32/12 i think with a slightly larger front ring,
I have run 48v,60v,and 72v so far but am tempted to give 96v a go and see where it gets me !

it has snapped 2 belt's so far on the gear reduction as some guy's on here have mentioned so i will be looking into this before i run out of spares,I am also going to try and source a better free-wheel for the crank to get more reliable sounding and feeling free-wheeling (it sounds like it's just about to give up every time i ride it so far)

cheers

 

[dnmun]

you are using an SLA charger if it only gets to 55V. pack is unbalanced if it is 16S lifepo4.