My solar bike

[avandalen]

mmm :-/
What kind of battery chemistry are you intending to use? I fear that the battery won't like it at all. Do you use a BMS? if it's the case I do think it will go crazy because of the voltage's difference between cells. If not, you will more than probably have shitty performances and short cell life because of non equal load on every cells.
I woud really advise you to go for a 8S setting (24V). If you do, you will have a 40V no-load, 33.6V optimal on the module side and a standard (setted) 24V MPPT 250W on the other side. You would be done
Gruß,
H.

I use A123 LiFePO4, with a capacitive balancing BMS. 24V is a good idea. Although the loss is higher due to the higher currents in the motor regulation, cables etc. But because of shadow, the PV panel voltage is much lower sometimes and here a battery voltage of 24V is critical.
Albert

 

[wineboyrider]

@ Dodjob and Avandalen. I don't think Dodjob hijacked your thread. I wanted Dodjob to chime in, because I remember him talking about solar charging his bicycle and thought he might help you.
I can probably easily get away with half the solar panels you have. The temperature today is only 34 F (1 C) , but we are still going to get at least 8 hours of sun...

 

[dodjob]

Hi Avandalen,
From my experience. The MPPT will raise the voltage (on the panel side) as soon as the condition are not favorable (like cold or weak). This is all the trick
With 24V you may loose a little efficiency with higher current and lower voltage BUT I don't think you want to put 600W out of your motor. If you stay in some "reasonable" power like 250-300W you won't feel a big difference.
When you say "the PV panel voltage is much lower"do you mean no-load? If it's the case, this is bad... If the no-load voltage drop so hard, it means that you are really far away to extract anything from your cells.
Anyway, the MPPT will helps you will get the best of your installation. This is damn sure. He will find the maximum you can expect from your panels and deliver it nice and clean at the desired voltage. That's how it works and what we pay for
All security are also included in order to preserve your battery so you don't need any additional controller.
Gruß,
H.

 

[dodjob]

@wineboyrider
doooh!! so schööön ist das wetter hier nicht X-)) well see for yourself:
http://www.wetter.com/deutschland/regensburg/DE0008684.html
Damn If I could make it with only 60W :-(
Here even with 120W we are sometimes "just". Allso please keep in mind that even if the sun hit your cells 8 hours a day, it won't hit them straight, and that substantially decrease the output (actuallly a lot)
Gruß,
H

 

[avandalen]

Hi Avandalen,
When you say "the PV panel voltage is much lower"do you mean no-load? If it's the case, this is bad... If the no-load voltage drop so hard, it means that you are really far away to extract anything from your cells.

At shadow the voltage is much lower, it depends on how many groups of cells with a bypass diode are shaded. So here there the PV voltage can be for instance 20 to 40V.

 

[ddk]

hello

I just thought I'd add what I've been experimenting with, as I'm also toying with the idea of a "solar bike"
exception is my vehicle is a trike.

As I have an easily reconfigurable solar system I've been experimenting with various ways of charging batteries, particularly lithium ion batteries.
Currently I've rejected using a higher voltage setup @ 48V. Too much electrical stuff.

I've been testing having the panels wired for 20V peak directly feeding Turnigy MAX 80W chargers.
I'm waiting on another charger but my intentions are:
panel grouped into two isolated 20V panels
each panel feeding one charger
said chargers in a position on the bike (trike where I can observe their operation (or remotely- haven't gotten to that point yet)

I've tested this idea only using one charger for a couple of weeks.
Great Success so far.
If and when I aquire the other charger I'll have real results to share.

The advantage I see using the Turnigy charger sans mppt is that it will run with voltages of 10-20V before shutdown.
Very close to what I'd expect from the solar cells going from full sun/full or partial shade

 

[avandalen]

hello

The advantage I see using the Turnigy charger sans mppt is that it will run with voltages of 10-20V before shutdown.
Very close to what I'd expect from the solar cells going from full sun/full or partial shade

That is smart. But a MPPT calculates the maximum solar cell power point, the Turnigy not.