recharging electric bicycle batteries

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Hi there ...

I am trying to figure out how to run my electric bicycle 'off the grid'.

My bike uses a kit from www.electricrider.com. It has three 12v 10ah sla batteries wired in series for 36v to the motor. It uses a 36v Soneil brand charger that plugs into a 115ac wall outlet.

My wish is to ride to work, then ride home, then charge overnight. How? I live in an apartment with a balcony that gets good sun half the day. I don't like to mess with high maintenance stuff so I want, you know, stuff like reverse polarity protection, no maintenance battery, no worry about overcharging etc.

My idea so far... get one big 12v deep cycle sla battery, stick a solar panel and controller on it, and leave it on my balcony all day. Then at night, I hook up the deep cycle battery to an inverter, and plug my Soneil charger into it, and charge the bike batteries overnight.

It might seem overly complicated... but what is the alternative?

Two sets of bike batteries...charge one while i use the other set? well, these battery packs are wired together in series, so id have to find some 36v charging system... and from what i can tell all the popular , and thus economical stuff, is 12v. i could alternatively unhook the three batteries, charge them as 3 separate 12v batteries, but that is totally inconvenient.

i also like to stick with the charger that my bike kit dealer gave me with the bike batteries, as from what i can gather, batteries and chargers are somewhat 'matched' to each other and the application... i could be wrong of course..

but in the future i might like to switch battery sytems (to lithium or whatever) and of course the cheap charger for that will be 115 vac input, not 12v input. so if my solar charging side gives 115vac output i can , you know, have an easier time using the charging equipment likely to be sold in kits.

Id also like to stick a little wind generator out there to supplement the solar, but i figure id start with solar and figure out how to get that working first.

If anyone can point me in the right direction i'd be grateful. if anyone else has already done this, done it better, etc, id like to know about it.

and if my solution is not totally crazy then how can i pull it off for like, 200 bucks? Thanks.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    Re: recharging electric bicycle batteries
    decora wrote: »
    and if my solution is not totally crazy then how can i pull it off for like, 200 bucks? Thanks.

    Good hearted, but stick with your plug-in charger. The size solar panel you need, and the quantity of them will be way beyond your budget. Heck, the 100AH SLA battery will be more than half your budget.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: recharging electric bicycle batteries

    agreeing with mike here i would say you could get another set of batteries to charge up while using a set in the bike. try not to let the batteries drain below 50% so as to allow for longer battery life.
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  • System2
    System2 Posts: 6,290 admin
    #4
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    Re: recharging electric bicycle batteries
    mike90045 wrote: »
    Good hearted, but stick with your plug-in charger. The size solar panel you need, and the quantity of them will be way beyond your budget. Heck, the 100AH SLA battery will be more than half your budget.

    ok... lets just say that i won the lottery... then what?
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
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    Re: recharging electric bicycle batteries
    decora wrote: »
    ok... lets just say that i won the lottery... then what?

    We need to know how much power it takes to recharge after your "typical" day.
    The first step to discover that is to measure how much power your charger consumes in a charge cycle. You can calculate it, or measure it with a Kill-A-Watt meter, which will total the power used. Wild guess is 2 KWH

    Knowing that, you need to calculate how much sun shines on your porch/balcony
    3 hours Bright charging sun (I know - you get 5 hours, but only the brightest are worth anything for charging)

    Then you need to size a solar panel nearly 30% over requirement, to account for the 5 minutes the sun is not in prime position, controller losses, etc
    2KW / 3hours = 666W * 1.3=866W of solar PV That's 7ea 125W panels, only $609 ea or 8 for $4,720 Mitsubishi 125 Watt, 12 V
    http://store.solar-electric.com/mi125wa12vos.html

    4 stage Charge Controller is next - another $200, and for the most efficiency, an AGM battery, that needs no venting or water refills. Count on $300 for that.
    Another $300 for your sine wave inverter (300W)

    This all is based on my wild guess of using 2KWH per cycle. You can reduce the panels, and maybe find a less expensive battery, but you still need charge controller & inverter, and racks to mount the panels on.

    or you can use the supplied charger for less than a $1 / day
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
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    Re: recharging electric bicycle batteries

    "ok... lets just say that i won the lottery... then what?"

    buy a tesla electric sports car.
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  • System2
    System2 Posts: 6,290 admin
    #7
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    Re: recharging electric bicycle batteries

    That reminded me of this article I was reading the other day about the same thing. This guy charges his while at work or wherever.

    http://www.builditsolar.com/Projects/PV/pvscooter.htm
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  • System2
    System2 Posts: 6,290 admin
    #8
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    Re: recharging electric bicycle batteries

    thanks for the info all
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