Hi,
I made my first electric bike with a conversion kit I got from the internet. I attached 3 12V batteries to a 36V controller.
The controller has several wires going to the brakes, motor (36V, 350W), brake lights, on/off switch etc... (in the picture below you can see the circuit as it is now => black circuit)
My question is how to deal with charging.
I tried to find the answer on youtube but most of the time, you don't get the right answer for conversion kits.
What I would like to do is to put on a small solar panel (red circuit) + an additional charger (blue circuit).
The additional charger would be used when I don't have enough power from the solar panel.
Would this be the right way to connect the charger and solar panels to the bike? (just parallel over the batteries?)
+ Is it safe to keep these circuits all connected, even if I switch the batteries on?
View attachment 35977
Thx
Yves
Basically, IMHO, you are wasting your time with a small solar panel. Either a big one, or simply forget the extra complication. Size matters in this case.....
I can see the point of a reasonably sized panel, kept at home, that you plug your bike into when its not in use, but you have not mentioned this.
A larger and efficient panel is usually not cheap, especially if efficient, and it will take years to make any payback, unless you can find one for either nothing, or very much under the market price. Secondhand ones, are secondhand for a reason.....
Guessing only, but are the batteries possibly Lead Acid?
If yes, very inefficient and very heavy for the amount of power they hold. The best efficiency of a LA Battery, is at around 70% of charge sadly....
Once you get above that SOC, efficiency simply gets worse, and if the English language actually allowed it, "and worser!"
Tell me please that they are something more efficient than LA Batteries!
With any such project, to reduce the possibility of a big disappointment, you should always keep "efficiency" foremost in your head. Part of that is finding and purchasing "efficiently!"
Bu we here on KP can help you with design!
Furthermore, every battery (even ones of the same size, same manufacturer, same production batch!) is different to another one, especially in the e-bike world, the (generally) Li-ion cells have to be kept to the peak of performance
POSSIBLE, by a BMS.
One battery (36 volt in your case), covered by one BMS.
This BMS has a hugely important job to do to keep the charge within the battery evenly distributed, and to cut power out, if that is not possible anymore.
Your schematic does not show any method of cell/battery balancing.....which could mean that the first battery/cells that get discharged, will be reversed polarised by the ones still supplying power.
This damages the depleted battery/cells, from any chemistry that you might be using, though some tricks with special diodes can protect the empty cells and batteries.
I really applaud your efforts, but to help you further, we would need you to state your goals and how you plan to achieve them, so that we all can help you around the many pitfalls in front of you....Though I myself, knowing quite a bit about power and batteries, would hesitate very long before trying to go in the direction you seem to wish to take.....
The big solar cell, at home for free (not quite the right word!) charging, would on the face of it, appear to be the easiest to achieve I feel, though I am not up to date with current pricing and power output, especially in the UK where some summers, tend to not be that sunny!!
Furthermore, ANY Solar cell array, needs to be correctly orientated during the day, to achieve maximum output - follow the Sun, so to speak!
That in it itself, is a reasonable starting point for such a project I feel....and there are plenty of DIY electronic schematics around to help with that!
Best regards
Andy
