Author Topic: Solar Recharge  (Read 12376 times)

Offline HapCow5

  • New Member
  • *
  • Posts: 1
Solar Recharge
« on: May 30, 2007, 11:09:05 PM »
I'm considering purchasing a front hub kit to help me ride to work, about 8 miles with the first third of it over some modest hills, and the rest on bike paths on former railroad lines. I've read that the SLA batteries need to be recharged immediately to keep them healthy, but that's not possible for me at work. I have a good quality solar panel that was used to charge a 12V battery at a remote stream recording station. I've measured about 17V in sunshine, but my multimeter blips out when reading current (more than 1A). Can this be used to trickle charge the 36V pack of batteries while I work? Is a controller necessary?

Offline myelectricbike

  • PhD. Magic
  • ******
  • Posts: 644
    • How to Build an Electric Bike
Re: Solar Recharge
« Reply #1 on: May 31, 2007, 01:43:10 AM »
Modern battery chargers work on the principle of applying a constant wattage such that the current becomes less as the voltage comes up. For 3 series connected SLA/AGM batteries this means that minimal amperage  of .2 amps is at 44.5 volts while maximum amperage of 3 amps is at 37 volts or less. SLA/AGM's will sulfate at or below 12.7 volts and need to be balance charged using a parallel connected 12 volt charger every few months. Trickle charge on the Tuos is at 41.5 volts at around .9 amps. Here is what Universal Battery recommends for cyclic use AVOID DEEP DISCHARGE! 14.5 - 14.9 volts at an initial 3.6 amps maximum. You could add a resistor or varistor to your solar panel circuit to limit current and voltage but many stores that have motorized carts for patrons are now allowing ebikers to recharge for free if you ask them very nicely and offer to pay them whatever they judge to be the cost - usually only pennies per mile - most right it off as good customer service and relations and you do not want to shop at the stores or work for employers that don't.
« Last Edit: May 31, 2007, 02:57:57 AM by myelectricbike »

Offline dlantz

  • New Member
  • *
  • Posts: 7
Re: Solar Recharge
« Reply #2 on: May 31, 2007, 11:38:20 AM »
I am in a similar situation, but I have a 20 mile trip and work will not allow me to bring the battery in "for safety reasons".  Last year I bought 15 watts of foldable solar panels (3, 5watt panels from northerntool.com)  At my best estimation, these give me an additional 3-4 miles of range.  The rule of thumb that I was given for needing a charge controller vs not needing one is 5% of capacity, basically if your solar wattage is less then 5% of your total watt hours of the battery, then you don't need a controller.  I don't use one, and my pack is just fine.  One thing to keep in mind is that the plug in chargers can be pretty sensitive to overvoltage, so don't use the charger and the solar at the same time, or it can blow your charger when the pack gets full.  Best of luck--Dave

Offline OneEye

  • Confirmed
  • Master of Magic
  • *****
  • Posts: 261
Re: Solar Recharge
« Reply #3 on: May 31, 2007, 04:06:15 PM »
diantz,

Bizarre your employer won't let you bring the batteries in to recharge them for "safety" reasons.  You must be using those untested nuclear radioisotope batteries with the Superfund Site (TM) sulfator on them.  Here at my work we have several Uninteruptible power supplies in the building that use (can you guess...) 12V, 12Ah SLA/AGM batteries.  I'll let them know we need to evacuate the building.  Go figure.

Do tell us more about your commute experience:  What batteries are you using (type, voltage, capacity)?  How often do you e-bike into work?  I'm assuming 20 miles is your round trip distance, correct?  How much pedalling do you contribute?  Do you have any ideas on your battery life and the total milage you've put on your e-bike?  I'd love to hear more.

Offline dlantz

  • New Member
  • *
  • Posts: 7
Re: Solar Recharge
« Reply #4 on: June 04, 2007, 01:08:19 PM »
Sorry it took me so long to reply to your queries.  I don't check this forum that often.  Not being allowed to recharge my batteries for 'safety' reason didn't seem right me either, as there is an emergency light every 20 or so feet... and you can guess what type of battery they use.  The security guard once had a car battery explode, or so he said.
No, it's 20 miles one way, 40 miles total.  I commute on the bike most of the time for 6-7 months out of the year, several days of the week I get a right back home with my bike on a rack.  My first battery pack I just retired, it was the stock 3x 12v 12ah set in the plastic box.  It is not showing any signs of wear, but was simply not enough to get to work and back without copious peddling.  I replaced it with two minimoto 36v batteries in a trailer.  I am honestly disappointed with the performance, I was expecting more range from them, but am only getting about 35 miles with an average speed of 15mph.  When the lifepo4 batteries mature some, I plan on upgrading to them.  I have a small lifepo4 I've purchased as pieces from batteryspace.com that I plan on wiring in parralell with the sla's to supliment power requirements, I'm hoping this will take the stress off the sla's and give me back some range.  It seems like it should work, the charging voltage of the 10 cell lifepo4 set is about 38v, which is what the start out voltage on the sla's is.  The lifepo4 has ultra low resistance, which I hope will allow the sla's to charge it quickly.  I plan on recharging the lifepo4 pack at night my connecting it to my old battery pack, which will recharge during the day....sooooo.... complicated.....
I hope to upgrade fully to lifepo4 at some point

Offline myelectricbike

  • PhD. Magic
  • ******
  • Posts: 644
    • How to Build an Electric Bike
Re: Solar Recharge
« Reply #5 on: June 04, 2007, 01:43:44 PM »
My controller cuts out at around 36 volts which gives me 5 volts of operating power. Now after 5.1 miles it gets down to only 38 from 41 whereas during conditioning it was down to 36 at 4.5-4.9 miles. I don't know how far it would go before it hit 36 volts but 20 miles, even with the new regen controller seems way out of line. Even 10 miles would required I get 5 miles from the 38 volts to 36 volts I have left before the controller cuts out. Am I missing something here like maybe that  20 miles is to the bottom of the hill?

Offline OneEye

  • Confirmed
  • Master of Magic
  • *****
  • Posts: 261
Re: Solar Recharge
« Reply #6 on: June 04, 2007, 04:27:01 PM »
Wow, 20 miles one way on (3) 12V, 12Ah batteries? 

That's at least double what many people are reporting for their experience.  I have to guess there is some serious Tour de France style pedalling to accompany the hub motor power. 

There is a significant difference in air drag between 15mph and 20mph; the air drag more than doubles (x 2.37) between these speeds.  I wonder if that is also contributing to the longer ranges you are getting.  Most of the reports I hear talk about running at 18~20mph top speeds.

The thing that scares me about LiFePO4 batteries is the up-front cost and limited experience with them in e-bike environments.  At least with SLA there is something of a known cost and life cycle to them that can be justified.  The LiFePO4 are supposed to have a much longer cycle life, but if they are fickle to how e-bikes drain them the astronomical initial cost can quickly disappoint if you don't get a substantially increased life cycle from them.

A few students at MIT paired up a ~300W hydrogen fuel cell with batteries to extend the operating range of a go cart.  That would be an interesting application for an e-bike.  Of course the fuel cell cost them $5K, so again the question of life cycle and startup cost becomes an issue (and weight, I couldn't get any information on the fuel cell they used).

Offline dlantz

  • New Member
  • *
  • Posts: 7
Re: Solar Recharge
« Reply #7 on: June 06, 2007, 12:23:07 PM »
Yes, 20 miles with a fresh 3x12v X 12ah pack.  That is a slight up hill the entire way, throttle full open, about 1 hour and 10 minutes travel time, no pedaling.  This is with the 500w (peak 700w) golden motor in a cruiser with slick, high pressure tires and me being a 200 lb man.  I only now got around to getting a speedometer (I wanted the old fashion dial kind to go with the cruiser look, but they are incompatible with the front hub motor, so I finally settled on a newer looking one), so I'm assuming I averaged 18mph.
My controller kicks out at 30 volts, not 36... did they change the controllers?
From what I've read (and info is pretty sketchy on lifepo4), the lifepo4's only real issue is out of balance situations.  I'm cheap, so for my experimental lifepo4 pack I'm wiring each cell to a terminal block and every so often I'll pull the wires and redo them all in parallel to even out the voltages.  One thing that bothered me about the golden motor lifepo4 is that it's rated amperage is only 15amps(by the BMS), while the controller can pull 22amps going up hills... I would like to see a higher continuous amperage on the pack then the controller could feasibly pull (I go up some long hillls).  On the RC forums, I have seen many people use the lifepo4's in highly abusive situation (like 30C pulls, draining the cells to nothing, etc...) with spectacular results (meaning 1000's of cycles), even without BMS's.  Most of them use balancing chargers though.
I think the confusion about range there comes from a few issues.  The first one is that the goldenmotor motor is brushless, and quite a bit more efficient then the brushed motors (which I've read about getting 10 miles or range).  The controller is also a slow start, current limiting type, which will add a great deal to range (many of the other controllers out there allow 35-50 amp pull from the battery, the goldenmotor one is only about 22 amps max).  The efficiency of lead acid drops dramatically when abused, and from what I've read, the non-current limiting, non-slow start controllers 'spike' the batteries, so every time you start from a stop, your taking many 100's of feet from your overall range. If I keep the speed to 15mph, and recharge with solar in between the trips, I get the full 40 mile range with two minimoto batteries in a trailer(two 36v X 12ah).  I'm discovering that the minimoto batteries are still conditioning, and they only have 10 or so cycles on them, so I'm not sure what they will do when fully conditioned.  I had hoped for more, like 18mph, 40 mile range.  When I wire in the small lifepo4, it should take the abuse of the higher current draws (I'm considering anything above 12 amps to be high here for the sake of lead-acid efficiency), especially when the voltage is low, and should add to range considerably.... We'll see, like I said, the info on lifepo4 is sketchy as far as specifications.
The only real complaints I have about the golden motor kit is the low quality of the connectors on the controller.  I would recommend  replacing them with waterproof connectors, like the kind used for trailers on cars, you can buy them at auto parts stores everywhere.  Another thing that irritated me what the there were no connectors near the motor so that you can remove the front wheel without pulling the whole wiring harness.  I used a trailer harness for the power, and a 5 pin AT style plug from allelectronics.com.  It's quite bulky.  My wife says that the bike looks like PeeWee Hermin was assimilated by the Borg, but a small connector capable of handling 3, 10 amp power lead and 5 signal lines in a waterproof design is pretty expensive.  My solution was less then $10.
I think I've gotten off subject, we were discussing solar charging.  So sorry--Dave

Offline myelectricbike

  • PhD. Magic
  • ******
  • Posts: 644
    • How to Build an Electric Bike
Re: Solar Recharge
« Reply #8 on: June 06, 2007, 03:47:32 PM »
Humm...  ??? 10.5 volts is the fully discharged state of a 12 volt battery.  >:(

 :'( To verify your claim, however, I need to recheck the lower limit my controllers will allow since my trips have been limited to 5 or 6 miles to be sure I wasn't stranded pushing. I have four I can use for testing.

That said the amp hours and Ampere-hour rating is not a measurement of maximum instantaneous output but rather a measure of total battery capacity.  ;D

Give me a week or so to do the tests.  8)

...as for connectors the Mylex connectors do a pretty good job and becasue they are dongles you can replace them with whatever you want. Many ebike owners use the same connector that is used on APC UPS 1500 watt units. I used European style terminal strips with hot melt or shrink wrap protection. As for removing the front wheel for tire changes I leave lots of slack between the axle and the first tie. That way I can slide a flat tube past the fork on the other side with no problem. However, I now use solid tubes since I hate fixing flats. ...back to battery testing.
« Last Edit: June 06, 2007, 04:19:45 PM by myelectricbike »

Offline dlantz

  • New Member
  • *
  • Posts: 7
Re: Solar Recharge
« Reply #9 on: June 07, 2007, 01:14:40 PM »
Yes, amp hours is overall capacity for a given amperage draw, given in C, so 1C for a 12 amp hour battery is 12 amps.  Most capacities for lead acid are given at the c/20 rate... meaning you would discharge the battery in 20 hours, or .6 amps.  At 1C, your efficiency drops to 40-55% (depending on which chart you look at) for lead-acid.  So your 12ah battery is actually about 5ah at these current draws.  The lifepo4's are suppose to only drop to 97% efficiency for astronomical draws like 10C to 60C (for a 15amp hour lifepo4, that would be 150amps to 900amps (!))  This has been verified by the RC world on a smaller scale (2-5 cell strings or small amp hour cells) and is for the a123 systems M1 cells, not the generic cells from China (although I'm betting M1's are made in china also).  The lifepo4 cells I bought from batteryspace.com are rated for continuous discharge of 10C.  The capacity is 1.3ah, so they should be good for continuous discharge of 13 amps and would last about 6 minutes.
Yes, European terminal strips are nice, I have those in the rear wiring box over the controller.  I never thought of heat-shrinking them, but that is a good idea.  Shortly I need to remove my front wheel and send it to the shop for truing... I've tried to do it myself, but have never gotten the hang of it.
I was unable to find solid tires for 26" wheels when I looked before, and the foam wheel had confusing information on weight capacities... I use the really heavy thorn resistant with a thick tire liner... and have still managed a flat with those.   I tried the self sealing tire, but it ruptured and the oozing gunk inside kept the patch from sticking.
How do you remove solid tires?  I had them on my first bike as a child and remember trying to pry them off with a screwdriver because my parents told me I wouldn't get a new bike until mine broke.  The darn things wouldn't come off.
oops, still of topic--Dave

Offline myelectricbike

  • PhD. Magic
  • ******
  • Posts: 644
    • How to Build an Electric Bike
Re: Solar Recharge
« Reply #10 on: June 11, 2007, 08:59:29 PM »
 :D :D :D I didn't have parents so.... Anyway after many years of experience with solids I can summarize everything by saying take your time and lots of breaks - let is sort of happen by itself - long before you let it get the best of you work on something else. Its the price you pay for having no flats later on. You have to be very careful especially with alloy rims not to let a screwdiver or pry bar puncture the tube or dent the rim. Also I use lots of screwdriver and pry bars and try to keep the tube from knowing whats going on or exactly what I'm doing. If you do then it will begin to fight you like Chinese handcuffs. Just relax. Sort of sneak up on it Before long you will have it off and it won't even know what you are doing. Go even slower putting it back on.

I know the previous owner of No-More-Flats, He was bought out by Bell. Bell tells me they plan to sell them again through Wal-Mart as he did before. The guy made a fortune but I don't know him that well. Otherwise I ask him to teach me how they are made and I'd go into business for myself.

There is another company that makes a solid urethane tire/tube combo in a variety of colors, treads, "pressure" equivalents but the No-More-Flats work fine for me. Oh Yes ...and use lots of Dawn liquid soap for lubrication before putting on or taking off.

Okay now where was I .... oh yes... okay the LiFePo4 are too expensive right now.  ;D

Offline radler63

  • New Member
  • *
  • Posts: 1
Re: Solar Recharge
« Reply #11 on: July 02, 2007, 03:12:43 PM »
Hi,

actually I did test solar only driving- the problem 55 W is not a lot- I'm waiting for tandem cells with higher efficiency
The storage are 8 supercaps with 120F each.

http://www.hyperbike.cc/docs/solarbike3.jpg


Regarding recharching I'm in need of a charger capable of loading LIPoly, I learned that does not exist.


Last but not least for solar only operation I'm in need of a better motor 75% efficiency is not enough- 66% at full load.

cheers

g.fried

Offline paulb

  • New Member
  • *
  • Posts: 10
Re: Solar Recharge
« Reply #12 on: July 23, 2007, 01:03:05 AM »
Hello All,  I have just ordered my kit and am trying to get an idea of the range I may expect with the various battery types.  This thread seems to have the most info in that area.  My goal is to ride the bike to work.  It is 16 miles each way with some large hills.  I will be able to plug in and recharge at work.  I also intend to pedal a lot, the kit is intended to help me up the hills.  From what I have read, it sounds like I could get by with the 12AH sla batteries. I weigh about 200 lb.  Any advice is appreciated, Thanks

Offline erdurbin

  • Confirmed
  • Magic Undergrad
  • ***
  • Posts: 70
    • not so Common sense
Re: Solar Recharge
« Reply #13 on: July 23, 2007, 01:19:52 AM »
I get about 12 miles on my 12ah batteries. That is up and downhills, about 18 start and stops. I weigh 170 lbs.

Offline paulb

  • New Member
  • *
  • Posts: 10
Re: Solar Recharge
« Reply #14 on: July 23, 2007, 01:26:19 AM »
Thanks for the reply.  Are you pedaling at all?