I have a generic 1000 watt hub motor that is new and it has never been used. I ordered batteries, but I didn't have cables to hook everything up properly. I tried one battery without charging it and I didn't get so much as a flicker of light. Do I have to have all batteries charged before any indicator light would come on? I am hoping this bike hub motor is going to work and I am charging the batteries one at a time. Can one battery be used to see if things will function on this bike or do I have to wait until I charge the complete set of my batteries making it 48 Volts?
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Some of your recent comments suggest you don't have much in the way of a motor controller. With this much power you'll need more than a simple on-off switch, and many off-the-shelf ebike controllers would burn out in no time with that current. You're quite likely to break the batteries, not to mention the brakes and yourself.– Chris HCommented Oct 19, 2015 at 15:08
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2 Answers
Your 48 volt motor probably uses some modern flavour of lithium battery. It will probably refuse to run on anything less than 44-46 volts (actual numbers may differ) and this will be in the controller's manual.
If you're using 12 volt SLA lead acid batteries, then they must not be discharged below 10.5 volts per battery, which would be 42 volts in your scenario.
To get 48 volts, you will need 4x 12V batteries in series not parallel. 12V batteries in parallel will still only give 12 volts, just a lot more current for a lot longer. Since your motor is 48 volts it won't even start on one 12V battery.
I recommend you use the fattest wires you can to link your batteries. Electric cars eschew wires in favour of busbars for added cross sectional area.
If this sounds like alien gibberish, you should enlist the aid of an electrically-minded assistant.
As an aside, you'll need to change a lot of how you ride once you have that much power on tap. Riding in the door zone becomes a game of Russian Roulette, and you'll have to ride much more defensively, which means scanning ahead, eyeballing possible threats, and anticipating what might happen.
Also some locations would call a 1000 watt motor an electric motorbike, not an assisted pedal bicycle. You may need to check this out.
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Another thought - if you try using a 12 V charger, you'll need to unwire the 48V pack first, and charge each 12V battery separately. The risk of shorting something is high, even with covered spade connectors.– Criggie ♦Commented Oct 18, 2015 at 23:18
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Hello Criggie, I appreciate your detailed response. After I charged the batteries with a 24 volt battery charger charging two batteries at a time, I wired all four of them in a series. It worked perfect. You are right. It is a fast bike and I could barely hold on. After riding it a couple of miles, I stopped at a stop light and put the power on and the front hub motor fell off. Wow...I was so glad and thanked God that I was not traveling at top speed and that nothing was damaged. Commented Oct 19, 2015 at 3:37
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Did you not torque the wheel nuts up properly? Are you depending on a quick release skewer to hold in 1000W of power? Did you fit the torque arm(s) to the fork? And, can you limit the motor to 300W until you get used to it, then add some more power later?– Criggie ♦Commented Oct 19, 2015 at 3:42
It would help a lot to know what motor you have and the batteries that you are using – it would make it much easier to offer specific help.
The answer to your question depends on how the batteries will be wired. If they are, say 12 volt, batteries that are wired in series you will need to have them all charged before it will power up. If the batteries are 48 volt batteries that are wired in parallel, then one should do it.
I suspect that the batteries are set up to be wired in series, but without more specific information it is impossible to do more than guess.
When you wire batteries in series, the voltages add up. So until you've got at least the minimum running voltage in the batteries it won't start up. When the batteries are wired in parallel they all, in theory, contribute equally to providing the current that drives the motor. In fact there are slight differences between the batteries that prevent this and one of the batteries will take most of the load. As with people, this doesn't usually work out well…
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Thanks dlu for your response. Everything is okay now after giving the batteries a full charge. My problem now is how to keep the front hub wheel from falling off by the bolts coming loose. Commented Oct 19, 2015 at 3:39