elle

okay, newbie here....

just bought an ebike conversion.......
800w 48v battery 48v 15ah 2c

I need to connect the battery to the kit - is there any rating on the connectors, or can i go to an auto place and use their electrical connectors (i have only used them previously for 12v)

I would also like to buy an inline fuse, but they have amp ratings with no Volt rating

i would also like an on/off switch - but same problem

***********
I found this on the internet

Amps = Watts divided by Volts.
Volts = Watts divided by Amps.
Watts = Volts times Amps.

which when calculated - i am trying to draw 16.66 amps from the battery, but i figure if i get a 30amp or higher switch and fuse holder????

is there a calculation for downing the amps to increase the volts??

any help would be appreciated, as i want to get onto my bike as soon as possible

once i got the kit, i thought it would be an easy connection

chvid

I imagine a 30 amp blade fuse would be about right - depending on your controller you might get a peak amp spike of up to 40 amps instantaneously as you accelerate and the motor is producing peak torque, but the fuses take a little while to blow. Setting it at 15Ahr x2C max continuous = 30 amps. If it blows, you could move it up a bit..say 35 or 40. I'd use 30 amp Anderson connectors for your connections....they are a bit tricky to install on the wires 12-16 guage approx. Search for "Anderson connectors" on the endless-sphere forums...available from www.powerwerx.com

I imagine the 800w referred to is just the "nominal" rating of your motor, with a typical, say 20amp, max controller. That figure is more dependent on your controller than on the motor. With a higher 30amp controller, you could easily pull 2C from that battery for short periods about 1400-1500 watts (52volts times 30 amps). Thats my pattern on my Ping 48V 15Ahr battery, also a 2C rating. I try to keep it under a 1000 watts though most of the time, by pedalling as much as possible, but i fairly regularly record spikes of 1200-1300 watts on my CycleAnalyst. I wouldn't think you would be limited to 800 watts with a 25-30 amp controller. I've seen 37amp spikes with a 35 amp controller, which is rather high for a 15Ahr 2C battery - the battery wouldn't like that too much, except for very short intervals...note: the 2C is the max continuous rating, not the maximum discharge which the BMS would shut the pack down at..that's more likely to be around 40 or 45 amps on your battery...

elle

Thanks chivid, i had no idea (second part of your post)..
have bought the anderson plugs (thanks)....
but am still concerned about the 30amp blade fuse - does it matter that i am using it with a 48volt system??

dumbass 

Forgetting the battery for a moment I'll talk about the botor/controller. The controller is where it's at......You need to know what size controller you have because the motor will take whatever the the controller throws at it until the motor burns out. Assuming the motor/controller is correctly matched your motor will normally pull twice the rated wattage under load. So figure on at least 1600+w devided by 48v = 33.3a. You can likely get away with connectors that are rated at 30a because they generally have a min. 20% under rating. Of course 40 or 40a would be better but they start getting a bit bulky. I prefer to use 30a Anderson connectors for all my work. The same thing goes for the fuse. You can find 30a fuse holder everywhere (even Wallie World) but 40 to 45a are a little more difficult as are the fuses. I would start out with a 30a fuse on your setup. I'm betting you will never blow it unless you short it. I've run 30a fuses with my 35a controllers for 3 years and have yet to blow a fuse.

The switch is your biggest problem to find. I am using automotive switches rated at only 15a. The voltage really isn't that important at this point. While the correct switch would be rated at 35+a I am guessing you would do fine with a 15 or 20a switch. Again they are generally very under rated. And the rating is more important is switched under full load. But the switch is not going to see full load amperage when you flip it on because the motor is not actually running. However, if you were to use the plug connector as your switch you might actually see a spark when pluging and unpluging. This is common and most people don't like it.

As for youe 15ah battery. Personally I think it's very undersized for the motor. With a 2c rating it's only 30a and that is not enough for the motor/controller setup you have. But I've been wrong before (but i don't think sooooo). I am assuming by the rating info that it is a lifepo4 pack and therefore, it likely has a BMS built into it (you better hope so). Should you have a problem with the motor cutting out under load it is a good indication the battery is to small and the BMS is trying to protect the motor. The controller could also do the same thing because as you load the battery the voltage drops and most controllers have a built in safety for low voltage and it will cut power to the motor. You may actually feel the motor studder because as the load is removed from the battery the voltage climbs and the controller starts again. So on some crazy motors/controllers it will actually cause the on/off to happen so fast that the motor studders on and off. Bottom line if you have any problem with any of these things the only solution is to add a second pack to increase your capasity. I would highly recommend you not use full throttle with that battery to much until you know the actual draw of your setup.

Bob

elle

I am just starting to realize how much we assume what we are sold is the right setup.... and someone who is in the field told me a 10 ah battery would do???? I wish i bought the 20 now
oh well,,,,,, yes lifepo4 and it has a bms

connectors that i bought are anderson plugs 50a

fuse : I take it dumbass that the voltage is not the problem with the fuse holder/fuse,,,,, just grab a 30a fuse/holder from an auto shop????

switch : voltage is not a problem with the switch, great, although i will try and get one with the correct amp - although i did notice some of the ratings on the toggle switches - as the volts doubled from 12 to 24, the amps seemed to half............

Thanks dumbass for your post

chvid

I think Bob is right, especially if the scenario is that you are pedalling very little. Otherwise I think you will be ok with the 15Ahr pack, if you watch your gearing on hills, pedal a fair amount on hills, and don't do unassisted (by you) starts from a standing start at max throttle. And pedalling's part of the fun! You can also hook up two packs for longer range, which babies the individual packs nicely in parallel. In general big batteries are the best, even if you don't use all the power, just to go easy on them. I typically average about 15 watt hours per mile, which at 52 volts on my "48 volt" battery is only around 3 amps average discharge, well under the 2C rating. An average hill and I might be just over 1C discharge rate, around 700 watts. A monster hill and I'm close to 2C (30amps) unless I gear way down and don't try to hold my speed - so I gear way down and protect the battery. So far so good on the battery. A cycleanalyst can help with protecting your battery, as you can set an amp limit in the controller, say to 20 amps. So, yes, a 20 amp controller is more conservatinve than a 30 amp controller, but with sufficient babying it (the battery) would probably be ok if you pedal a lot...I don't believe the voltage is relevant to the fuse rating...just the amp rating.

Sangesf

Brand of controller? And what is it set for?
That's the key.
More info needed pls

dumbass 

Our pleasure to help when we can. Yeah, I think you will be fine with a 30a fuse holder. Those 50a Anderson connectors must be monsters but at least you won't need to worry about them. Better to error on the safe side.


As chvid points out you should help your motor as much as you can and baby that pack. Have some fun and save your pennies so you can add a second pack and then go wild. If your throttle has voltage lights on it it can help a little. Of course a good CA meter would be the best but the throttle lights do help. If you have them try to stay out of the red. It's a sign that you are running the voltage to low on the pack. This will improve the life of the pack and give you much longer travel distance.

Have fun with it.

Bob

elle

Just a quick post, as i am excited i found it (after someone emailed me and told me to check out circuit breakers)

on ebay i typed iin "circuit breaker dc" and i found a marine 40amp circuit breaker which is also a switch - and the DC rating is 65 volts

https://cgi.ebay.com/ebaymotors/ws/eB...m=290444661444

in case you can't tell by the pictures, i am over the moon

now............. protecting the most expensive part of the kit - i need to check cycle analyst and ca meter

dumbass 

without question that is a cool switch/breaker. However, 45a?? That's way to high to actually protect your system so I would still through in the fuse unless you can find a lower amp rating.

elle

there are many different amps 30,40,50 (lower and higher) - I was going on a previous post (on this thread) that said i would use a max of 33 amp, hang on - I will check

:-) IT WAS YOU

you told me a 40 - 45 amp fuse would be best right at the beginning - are you changing your recommendation

also, the circuit breaker is a 40amp (or am i missing something??)

and i was just about to press buy but now i will wait for your reply..

Sangesf

Your best bet is to take a test ride, and see what the max amp pull is, and then get a fuse/breaker/whatever that's a little higher.

elle

I have no way to test amp pull

dumbass 

OH WAIT, NO IT WASN'T ME...IN FACT NO ONE TOLD YOU TO USE A 40a OR 45a FUSE OR BREAKER. Hmm, I wonder where you got that information. Maybe it was in a dream you had. I think you should read more carefully next time before you try to gety cute and spit your BS at someone that is trying to help you. Besides, if I were to error in any information I were to give you I think it would be better if I were to error on the safe side. DON'T YOU?? I told you to use a 30a fuse not a 40a or 45a. Would you like me to underline it for you? I did however, misread the Ebay posting and thought the breaker was 45a. Big deal 40a or 45a is still to damn big for your use.

You have been told that the size of the controller has a lot to do with the amperage draw. You were asked for that information. Have you provided it in any postings yet? NO!! But yet you feel justified in trying to tell me that I gave you bad advise.......Everything I recommended to you was 100% correct so don't blame me if you don't read what your being told.

As I said before, Have fun with it.

Bob

chvid

I think a 30 amp circuit breaker might be suitable..they seem to have a "tripping" level slightly higher than the nominal rating...

elle

sorry i caused you offense bob - i was not trying to do that, hence all the smiley faces.....

the confusion arose when you were talking about connectors - and then you moved into saying this

"Of course 40 or 40a would be better but they start getting a bit bulky. I prefer to use 30a Anderson connectors for all my work. The same thing goes for the fuse. You can find 30a fuse holder everywhere (even Wallie World) but 40 to 45a are a little more difficult as are the fuses. I would start out with a 30a fuse on your setup."

now that i am rereading it, ................

thankyou chivit - i will go and buy it now, the info you guys/girls provided was invaluable,,,,,,,, and i am glad i waited for this last post before i bought the circuit breaker..

I have everything i now need to complete my ebike, thanks

i also looked into the cycle analyst - was a bit surprised about the price initially... but thought it was a very good idea.....

but regrettably, my kit does not come with the plug - to just plug it in......... and it looks like too much of a hassle at the moment to wire it in....

the controller bob has just a sticker on it that says 800w - but because of the sticker (sticker type it is) i believe it is just a sticker for the factory workers to put this controller with the 800w wheel
but if you really want to know what the sticker says

brushless dc motor controllers
model : syk-48-80w
voltage : 48v
output power : 800w
control voltage : 1.1-4.2v
made in china

i may have the wrong controller for the job (just another salesman taking advantage) or it may be the right one........i have no idea, and i didn't know i had to be careful about it untill this post

anyway, thanks again

chvid

Elle...I think you are overthinking everything...I think all of your equipment is well matched, and should work fine together...you might pick up a watt meter from hobbyking just to keep an eye on the state of everything - power levels, amp draw, operating voltage etc. It sucks to fly blind...Don't worry quite so much. There are lots of safeguards built in...amp cutoffs in both the BMS and the controller, high voltage cutoffs, low voltage cutoffs. Just have fun...

dumbass 

No problem elle.......So is there a sticker of the motor also? I agree with chvid if your on a budget (who isn't these days?) pic up a meter from someplace like HobbyKing for $20 or $30. It will do most of the things a CA meter will do just not as fancy. But the wiring for it will be about (worse) then on a CA meter so if the CA meter scared you so will the HK meter.

I think the 30a breaker will work beter for you. Most breakers do open higher then the rating and they are generaly slower then a fuse. Keep an eye on the breaker because breakers are not actually intended to be used as a switch. Meaning they are not intended to be turned on/off several times a day. I'm not saying it won't work I think it will do fine just an FYI.

Bob