solar bike

[ragez0r]

Hi there

I am the proud owner of an Ecoped e-bike


it goes about 35 kph and takes me just about wherever i want to go
but... what if i want to go just a wee bit farther ? what if i dont want to haul my 48V lead acid battery to my appartment each time to charge it ? so then i saw this
solar trike 095.jpg

SOLAR PANELS... genius!!
well cant i ? since the bike is parked outside all day long.. might as well take in some uv rays and hopefully i can absorb some sunlight while i ride.. or is it bad to consume the battery while its charging ?

im thinking 3 of these panels.. please tell me if they are the correct ones that i need
1 pcs 10W 17V 0.6A Solar Cell Panel Battery W/ Diode on eBay.ca (item 190424319090 end time 31-Jul-10 01:04:32 EDT)
17x3 is 51.. should be enough to reach the battery i hope


feel free to give me some pointers

[ragez0r]

oh and in case your wondering.. i have a big tote in the back so i can fit 2 there and i figure.. 1 in the front ??

[saand]

Hi ragez,
I like the idea, but hopefully i can let you know about the practical issues of doing this as i have done a lot of work with solar panels in the past.

First off, if your bike is out in public your solar panels will get stolen, they are expensive and easy to carry. In australia we have some electronic road signs with solar panels that are about 4 meters up in the air above the sign. I have seen signs where people have hacksawed through a very thick pole to get the sign on the ground then they have taken off with the solar panel.
Looking at the pic of the solar panel you linked to the cost of those panels would be about 1500 or more AUD and AUD is fairly close to USD so they would be very attractive to theives.

Now for some of the electrical info.
The ability of a solar panel system to charge your batteries is dependent on
- the area of your solar panels
- the time you have to charge between trips
- how much you need to charge between trips

So for some calculations you can do
the sun puts out about 1 kW of energy for every square meter (m2), this is without any cloud cover and is when the sun is directly over head.

So to work out the energy you can expect if your bike is sitting around for a day somewhere
work out the square meters of solar panel you will have, multiply this by 1kW. This give the amount of energy the solar panels would generate at 12 midday without cloud if they were 100 % efficient.

To compensate for efficiency your panels are likey to be 15% efficient unless you spend a lot of money to get better. so multiply the previous number by 0.15. This is the energy you will get out of your panels at 12 midday with no cloud.

now to work out total energy in kwh you will get for a day. you mulitply by about 5 because you get an equivalent of about 5 hours of full light per day. This varies dependent on location and season but use 5 for a ballpark guess. This give energy out of your panels over 1 full day

Now you want to work out the energy getting to your batteries
so multiply the previous number by the efficiency of your regulator and efficiency charging your battery
so multiply by about 0.9 then 0.9 again and you will get energy going into your batteries over a full day.

example for calcs
you can get maybe 0.5 m2 of area
0.5 * 1kw = 0.5kw
0.5kw * 0.15 = 0.075 kw, (note you are looking at getting 3 by 10W units so that is 0.03kw)
0.075kw * 5h = 0.375 kwh
0.375 kwh * 0.9 * 0.9 = 0.30375 kwh

so you could get AT BEST CASE 0.30375 kwh of energy into your battery for a 0.5 m2 panel



Now compare that to how much energy you are likely to use in a day.

also bare in mind if clouds come over or you park in the shade or a bird messes up your panel (even 1 location) that decresses the overall energy you will get significantly

Either way solar panels will help but i am guessing you will still need to lug that battery around for charging. You might do better off

also to answer one of your questions, no it is not bad to use the battery while charging

for solar panels at 51v and a battery charge level of 48v your probaby a bit close. Would have to look up the specs of the panels but if you get some cloud or anything to reduce the power output the voltage will drop below 48v and you wont be able to charge your batteries.

Possibly a better thing for you would be to change to lithium batteries which are lighter then just be happy carrying them around.

good luck to you, hope i havn't diswadded you too much, still a cool idea and hopefully with this info you will be able to know what your getting into.

[Bicycle Bob]

We use 17 V chargers on nominal 12 V batteries because they are actually over 14 V when healthy and fully charged, and we need a couple of spare volts to push the action. Get four.

[ragez0r]

@saand
thank you so much for all that great info, now i dont know if this is a conversion error but i doubt 3 panels will run me 1500.. perhaps 150$cad plust 150 for shipping (lol) plus other things like umm a voltage regulator.. that thing that will stop the charging process when the battery is full.. but your right.. i never thought of it that way.... as for buying a lithium, i really dont know... the shape of my 48v lead acid battery is so specific i have no idea if any other type of battery will fit but hey heres a photo...


is that a unique battery shape or are all electric bike batteries the same ?
also id like to add that it slides into this sort of bracket that keeps it in place..

@Bicycle Bob
thank you bob but.. 4 .. i have no idea if where i can fit the 4th one..

[saand]

Ragez your correct there, 3 times the 10 W panels you were looking at will not cost you 1500, i was basing my estimate on what the other bike picture had, they looked like higher cost commercial higher efficiency panels.
The 10W panel pointed to on ebay are only 10 W because they will likely have low efficiency and im guessing are probably made in china by a cheap manufacturer. If you are interested try researching some comercial solar panels, look up BP they make solar panels and will have size and efficiency i think they have datasheets too.

Regarding your battery shape, yep that is one unique shape. But i am fairly sure if you open up that case you will find a group of cylinderical battery cells (but open at your own risk, i give no guarentees you wont wreck your battery opening it up)

if you are feeling adventurous you could connect up a whole bunch of single cell batteries (the cylinderical type that is likely inside your uniquely shaped 12v battery)
this way you can make the shape/ size whatever you like.
This is exactly what they are doing in electric cars with new lithium cells, i think its the volt car (i might be wrong) that has about 4000 single lithium cylinderical cells. all connected up with wires.
you can use any type of cell, doesn't have to be lead acid, doesn't have to be a consumer type as long as you can get the voltage and the current you are after

also looks like your battery may have the charger inside it, cos it looks like you plug a mains power plug straight into the batter, so if you change batteries you will have to think about what to do with the charger. I might be misinterpreting the picture though.

sounds like a good project ahead of you, might take you a fair bit of effort though

[myzter]

hey Ragez, looks like your battery maybe 4 lead acid cells in that case ??
how many volts 48volts how many Ah ?

maybe a BMS (battery management system) is used ..
important to know before building starts ??

if you are going solar route, making a portable folding array of 4 panels (12"x12")
2 volts each panel
You can get a step up voltage booster, which can charge batteries from a 6-8V source.
In this case get 16/ 6"x6" -4 watt solar cells. these usually are .6v open voltage and 8Amps.
The solar cells will not cost as much as the voltage booster $200
and should charge your battery 50% in a couple hours

[ragez0r]

@saand
you could be right.. but i always thought that box in the middle of the cable was the charger but now with all this work you just told me about..and the fact that a 48v lithium battery costs 500-800$.. im starting to think i should just leave the bike AS IS

@myzter
4 cell 48v and 10-12 amps
could you link a Canadian site that sells those solar panels ? cuz all i got is ebay.ca and no stores apart from Addison sells solar panels in Montreal

[myzter]

ebay is probably one of the best places to get solar cells right now..
I have bought 6"x6" for as low as $2 each / $0.50/watt - not bad at all
Learn to make your own panels, would be the cheapest / most difficult

Im using 1/8" lexan bottom sheet, with 1/16" top sheet, with double sided tape in between. to attach to - 1/2" wood doweling, or 1/8" x 3/4" aluminum angle as the frame.

The lexan does affect solar cell efficiency, 90% light transparency//

[Bicycle Bob]

No Canadian Tire Stores in Montreal? No solar/eco specialty shops? No electronics stores? If you assemble what you want from small cells, you can get any shape or size. There's mail order, too.