Solar recumbent bicycle - how to hook up panels to lipo?

[swbluto]

I recently picked up a bikee recumbent bicycle with the intention of creating a long-distance electric bicycle. It seems to be a popular recumbent to convert to electric. Here's a pic.

I chose a recumbent because of the lower wind resistance and power demand and I'm using the highly efficient 9c motor on a 20inch rim (I'm modifying my bike's seat to reduce the frontal area to further reduce drag), and now I've ordered a semi-flexible solar panel kit that should be capable of 130 W and can be wired at 36volt, or can be configured lower (I haven't done the math, but I don't think I'll be able to get exactly between 24.6V-25.2volts for my battery without additional electronics). Here's the kit I ordered:

http://www.eco-worthy.com/catalog/product_info.php?products_id=267

I chose this one because it uses crystalline solar cells which are much more efficient than the thin-film variety (to get 130W required a ton of space for thinfilms) but it was also much lighter than the glass variety and because it's semiflexible, it should be durable to the strains of biking, but now I need to figure out how to hook it up on my bike. I'm guessing I'll probably either need to get a step-up or step-down buck converter (some sort of charger, probably), and it needs to constantly provide charging to the batteries while the batteries are being used by the electric bicycle.

Hmmm...

I'm just thinking of it.

Can I just hook these things up to my battery during use at 36 volts using a shottky, assuming my lipos are wired at 24V? I'm pretty sure I'll be using more power than my solar panels can provide, so I'm not really concerned about overcharging the batteries and I'm assuming the voltage output of the solar panels would decrease itself to match the voltage output at the battery. Then when I'm stopped, I could wire the solar panels up at 18V and plug in my lipo charger. Would that work? What if the power spontaneously decreases due to a passing cloud, would the Lipo charger just stop charging? I have a hobbycity lipo charger.

Thanks for any help! I have no experience with solar panels. ^_^

(The trip I'm planning on looks like it has about 80 miles in total, 40 miles one way, 40 miles the other, and I figure if the solar panels are providing 80watts power while the bike is consuming 150watts at 15 mph, it seems I should only need 140wh-200wh of battery one way and then 140wh-200wh the way back. And, I can reduce that further by pedalng though I want to minimize that - this bicycle seems to hurt my back. I'm not sure why, exactly, but I'm suspecting pedaling has something to do with it, along with the bike seat since I'm pressing my lower back against the bike seat. I can pedal on my upright bike and my back doesn't hurt at all. Since I'll be packing around 1000 watthours, and assuming I stopped in the area for 4+ hours, I could probably go 20 to 25 mph, though I might have to wire the batteries, and solar panels, upto 48v.)

 

[StudEbiker]

There are a couple of reasons you are probably experiencing back pain.

It is normal when first transitioning from upright bikes to recumbents to try and push too tall of a gear. Spin faster in a lower gear and you'll be happier.

The other reason is since you have a non-suspension model Bike E, you are taking more impact in your spine than you are probably use to since you are in a sitting position and there is nothing to absorb the shock. You can reduce this by "standing" in your pedals when you are going over big bumps. It's kind of difficult to explain, but you push both feet into the pedals at once and press back in the seat and your pelvis will lift off the seat some.

Only running at 24v will help your power consumption since speed kills (whs), but you aren't likely to win any speed races with 24v and 20" wheels.

 

[swbluto]

There are a couple of reasons you are probably experiencing back pain.

It is normal when first transitioning from upright bikes to recumbents to try and push too tall of a gear. Spin faster in a lower gear and you'll be happier.

The other reason is since you have a non-suspension model Bike E, you are taking more impact in your spine than you are probably use to since you are in a sitting position and there is nothing to absorb the shock. You can reduce this by "standing" in your pedals when you are going over big bumps. It's kind of difficult to explain, but you push both feet into the pedals at once and press back in the seat and your pelvis will lift off the seat some.

Only running at 24v will help your power consumption since speed kills (whs), but you aren't likely to win any speed races with 24v and 20" wheels.

Thanks for the advice! I'll keep it in mind when I go riding again.

Btw, do you think there's "gel pads" or some such to help absorb the shock?

Anyway, I have a 4pdt switch intended for switching between parallel and series in my 2 lipo packs, so that I can switch between 24v and 48v on the fly. 48v for the speed and hill climbing, and 24v for maximum efficiency, lower-speed, long-distance riding.

There's also a ping I'm adding in the mix somewhere, so that's why I need 4pdt instead of of dpdt.

 

[StudEbiker]

The gel pads may help, but I have found the spinning faster rather than pushing a higher gear to be the biggest help.

Other than my electric Bike E, I am now putting over a 100 miles a week on a loaded touring RANS recumbent and the standing in the pedals trick is harder to do on that bike since the riding position is more reclined. I have been able to avoid almost all back pain by spinning faster in a lower gear.

That's a nice bike you have. Pretty much a carbon copy of the bike I just built for my GF. I really like how nimble the short wheel base model is. Mine is the longer WB and it rides a little smoother since more of my weight is between the wheels, but hers is just a blast to ride! Once you get used to it you will probably really enjoy it. I know I do.

In case you missed it, here it is:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=46077

 

[swbluto]

Great bike!

I pedaled in a low gear, and it seems my back problems were no more. I also did ab crunches to strengthen the core muscles and I went on a long ride yesterday with some pretty hard pedaling here and there, and my back is doing just fine. Methinks I just needed to condition my body for recumbent use.

Anyway, in the quest to figure out how to hookup the panels to lipo, I'm thinking of using...

A boost converter! If I configure the 130watt panel at 18volts, and configure a boost converter to output 24.6 volts (The max voltage for the lipo), it seems like it should work. I might want to put a shottky on the output for reverse protection, dunno if it's desireable.

Does anyone have an opinion on this 600watt boost converter for solar panel lipo-charging use? http://www.ebay.com/itm/DC-DC-Power-Supply-Boost-Converter-Step-up-Module-10-60V-to-12-80V-600W-/290802073679?pt=LH_DefaultDomain_0&hash=item43b527804f

I could use a buckdown converter, but methinks using a lower solar voltage than the battery would be safer. Here's one that seems like it might work - http://www.ebay.com/itm/8-40V-to-3-30V-8A-DC-DC-Buck-Converter-HRD12008-Switching-High-Power-Supply-/390565039984?pt=LH_DefaultDomain_0&hash=item5aef7d8f70. Seems cheaper than the step-up and comparably efficient.

I also could use an HVC on the lipo and directly wire up 36volt solar to the lipo, but I'm having worries about the failure modes on an HVC and the potential for overcharging. It seems like should be more efficient than a 93% efficient boost converter.

 

[swbluto]

Extended the request for help to various relevant different forums. Just putting the URLs here so I can keep track of them.

http://www.rcgroups.com/forums/showthread.php?t=1869079

http://www.solarpaneltalk.com/showthread.php?10361-Charging-Li-poly-batteries

http://www.dutchforce.com/~eforum/index.php?showtopic=40917

 

[amberwolf]

Btw, do you think there's "gel pads" or some such to help absorb the shock?

Replace the seat with a suspended mesh seat. Can DIY one easy like I did for CrazyBike2, or you can build the much better one at http://recycledrecumbent.com
either way it will be suspending you in the mesh like a hammock or a lawn chair, and so it's WAAAAAY more comfy than any padded seat, especially on bumpy vibratey roads.

 

[swbluto]

Btw, do you think there's "gel pads" or some such to help absorb the shock?

Replace the seat with a suspended mesh seat. Can DIY one easy like I did for CrazyBike2, or you can build the much better one at http://recycledrecumbent.com
either way it will be suspending you in the mesh like a hammock or a lawn chair, and so it's WAAAAAY more comfy than any padded seat, especially on bumpy vibratey roads.

Hmmm, great suggestion! If I go on any long-distance journies that invariably have bumpy vibratey roads, I'll think about that mod.

Anyway, since I'm constructing this bike and it's going to be in a public area gathering sunshine, I have a feeling it's going to be tempting to thieves! So, I'm thinking a good way to secure the bike is with a good old fahgettaboudit lock, but a better way might be with a wireless security camera system! You look on your portable TV and you see some miscreants around your bike, and you yell in your wireless audio transmitter "Get away from my bike now or I'll call the cops!" and they scat. I'm researching now and I'm trying to find a good A/V transmitter and receiver, and I'll research the cheapo outdoor CCTV cameras later. Anyway, I'm asking the guys on the FPV forum on rcgroups in this thread about good A/V transmitters and receivers: http://www.rcgroups.com/forums/showthread.php?t=1871167#post24699226

It seems great that with an electric bike, you can power all sorts of neat electronic gadgetry.

 

[lifepo4ever]

Btw, do you think there's "gel pads" or some such to help absorb the shock?

Replace the seat with a suspended mesh seat. Can DIY one easy like I did for CrazyBike2, or you can build the much better one at http://recycledrecumbent.com
either way it will be suspending you in the mesh like a hammock or a lawn chair, and so it's WAAAAAY more comfy than any padded seat, especially on bumpy vibratey roads.

Hmmm, great suggestion! If I go on any long-distance journies that invariably have bumpy vibratey roads, I'll think about that mod.

Anyway, since I'm constructing this bike and it's going to be in a public area gathering sunshine, I have a feeling it's going to be tempting to thieves! So, I'm thinking a good way to secure the bike is with a good old fahgettaboudit lock, but a better way might be with a wireless security camera system! You look on your portable TV and you see some miscreants around your bike, and you yell in your wireless audio transmitter "Get away from my bike now or I'll call the cops!" and they scat. I'm researching now and I'm trying to find a good A/V transmitter and receiver, and I'll research the cheapo outdoor CCTV cameras later. Anyway, I'm asking the guys on the FPV forum on rcgroups in this thread about good A/V transmitters and receivers: http://www.rcgroups.com/forums/showthread.php?t=1871167#post24699226

It seems great that with an electric bike, you can power all sorts of neat electronic gadgetry.

i have a custom fpv set up tx and rx 5.8ghz for good for 1.5km the key is antenna not the output of the tx
asking 150$ + ship for the kit you will need a lcd monitor at 40$ on ebay and the kit is complete
my name is windfou on rcgroups
and here is my youtube channel: http://www.youtube.com/watch?v=FRfsaxuQq3s

 

[Cowardlyduck]

What ever happened to this build...still happening?

I'm thinking of doing a small solar wind faring on the front of my BikeE. Probably only 10-20W, but enough to add a couple of Km's to the range in charge let alone the increase efficiency gained from having a fairing.
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=57751&start=75#p1002550

Cheers

 

[wineboyrider]

Haven't heard from swbluto in a while? Banned?

 

[amberwolf]

Look at his profile.