solar charging scooter batteries

30 watts is too little. Your going to need something closer to 1000 watts. How much current is pulled from your charger? Multiply that by 120 to get the watts you need.

It depends on how much you ride your scooter. One of these meters will help you determine about how much energy you need: http://www.supermediastore.com/kilwateldet1.html "Kill-A-Watt"

A panel might provide 4 hours of its peak rating per day in energy, but I'm sure this depends on where you live. Where I live in NM I can probably get 5 hrs or more on average of a panel's peak rating in energy. So if it is a 10w panel than I'd get about 50 whrs per day. Does anyone know of any references to help determine this with a given area?

Also you need to factor in all the inefficiencies of the system.

The product you link to is a nice portable unit, but expensive for the amount of solar power generating capability.

Heres a unit that doesn't include the battery, but much more solar power generating capability: here. Idk about the quality of the panels however, or how long they will last.

For powering two lights a fan and a tv it depends on how much power they take and how long you will want to run them. I suggest you try and find 12v units, and as low power as possible. That way you could run directly from a 12v battery.

If you had:

two 30 watt lights: 60 watts
25 watt tv
15 watt fan

So total system power would be 100 watts. With a battery like one of these: http://www.trojan-battery.com/Products/ProductSpec.aspx?Name=T-1275%20Plus you could run such a system for about 18 hours. The above 60 watt solar panel system could help charge the battery but would only provide about enough energy to run the system 2 to 2.4 hours a day if you get full sunlight.

I work in renewable energy and get asked this a lot. Usually they want a solar panel direct to the batteries, which is a no-go for maintaining battery life.

Let's assume the ac requirement of the charger is 2 amps. 2 amps x 120 volts is 240 watts. If the battery takes 6 hours to charge, multiply 240 by 6 = 1440 watthours. So the ac device (inverter) would need to be about 300 watt to handle a 240 watt load. Assume the 300 watt inverter to be maybe 85-90% efficient so lets say for argument 270 watts per hour is consumed in providing the ac to the charger. 270 x 6 = 1620 watthours is a more realistic load on a battery system, 135 amp hours. The battery system to support this load would be 270 amphours (at 50% depletion), and the solar system to support the re-charging of the battery assuming 5 hours of full sun per day would be 324 watts.

Hold onto your socks, this is expensive.
qty. 4 - 80 watt solar panels at $495 each = $1980
qty. 3 - 86 ah gel cells retail $185 each = $555
qty. 1 - 35 amp charge controller $119 each
qty. 1 - 300 watt pure sine inverter $299
plus cables, lug ends, fuses, small parts
$3000 plus (sorry). You start to get the picture why solar for your home is way expensive. If you shop around you can get this for maybe 20% off list, and maybe procure Marine/RV batteries from the local discount store.

If your electricity from the grid is 12 cents per killowatt a 6 hour charge cycle costs about 17 cents off of the power company.

The reason to store the solar power in a separate battery is the power is collected during the day when the scooter is in use, and when you return home you hook up the charger, the power has to be derived from the battery bank storage.

You cannot go directly from the panel to the inverter, inverters need a minimum voltage and current to properly run, essentially the inverter will fail to run and could be destroyed without a battery as part of the circuit, and a charge controller will keep his gel batteries from frying with the 17 volts most panels output.

You may disagree with the prices because you can locate substitutes locally but the math is correct (+ or - 5%).

Jeff

jblamey,
while your math is correct, I think some things you estimate are overkill.

The XB-600 "electric bicycle" has four 20ah 12v batteries or 960 nominal whrs in energy storage. In practice you will probably only get about 70% of this due to the peukert effect. So even if you ride your scooter until the batteries are "dead" than you will only need to put 672 + (1/.95 * 672 [battery inefficiency]) = 707 whrs. AGM batteries are very efficient due to the way they recombine gas during charging so as you can see somewhere around 95%.

And you most likely won't discharge the scooter completely every day, but this depends on your ride profile. Lets say you ride enough to discharge the batteries 70% of the way every day. So now we are down to 495 whrs that needs to be put in the batteries every day.

To get past the inefficiency of both an inverter and a charger (if both are 85% than together they would be 72% efficient, but most chinese chargers are very poor in efficiency like 50%) you can use battery chargers which can take 12v directly, like two of these: http://www.powerstream.com/WC.htm . If the battery charger is 85% efficient than we are up to 582 whrs needed.

If you got 4 hrs of panel out put per day this equals 145.5 whrs of panels required. While that may be expensive, you may be able to find surplus panels. Solar panels may still generate electricity fine when old, they just generate less, but of course they are going to cost a lot less per watt of generating capacity.

150 watts of panels surplus: $300 (you'll have to find a source for them, try a google search for "surplus solar panel")
Two of these chargers: $240
Battery: Deep cycle golf cart flooded battery, check with battery supplier near you: $100-150
Voltage regulator off ebay (to prevent overcharge of battery): $50

So my estimate comes in at about $750 plus some for wire and stuff you have to buy. IMO whatever resources you can get for less or nothing the more practical your system will be. For example, if you could get used batteries that still have some life in them taken out of a golf cart than they may work fine for your application while costing nothing, and you are making more use of resources which helps achieve the ultimate goal---less expenditure of non-renewable resources. If you could get surplus panels that are going to be trashed anyway than this makes a lot of sense too.

And while your at it, you can investigate other sources of renewable energy such as wind, and what you have available that you can use. You may find you have the tools and material to build a wind generator. Some areas in the US are very good for wind generation while others are good for solar generation.

Hey, thanks guys for all the good info. I think that my scooter batteries are more than 20ah each. I thought I read someplace that they were 34 ah. Anyway, regardless of whether I put together a system or not...I've learned more from just these comments than from reading about solar online at several websites. I really want to learn more. Thinking about having a new home built in a couple of years and would like to have a solar installation on it. I live in Florida and the state will pay $4 per watt (min. 2KW) for such a system...as a "grant/rebate." Anyway, thanks alot for the info and advice!

Gushar

Oh, and here's something else...

I ride only about avg. 6-7 miles...or less. The longest ride I've had was 20 miles and only did this to see how the charge held up. And even then it seemed like there was plenty of battery power left. I believe I could have went another 10-15 miles. But anyway, often I ride just 2-3 miles max. I just ride for pleasure around the neighborhood...or to my workplace...just 2 miles away. And when I charge after each ride...it only takes at the longest maybe 2-3 hours of charge...often only an hour or so. So how much power will I really need to charge most of the time? Guess I can figure using the info you folks have provided...

Gushar

Hey, just thought this through some more....

First, you are right. The batts are 20ah according to xtreme's website. Ok. Assuming my average charge is more around 1/3 of the battery depletion...which I think is probably fairly accurate. Then, using your math...I'd need something like 240 watt hours of panels...which might end up as one 60 watt panel with 4 panel hours a day. Then, that system one of you recommended above from costco might just be the ticket! Am I correct here or have I left something out of the figures?

Gushar

Thanks for winding my numbers back. I did not have the time to check the specs on the scooter, more concerned with giving the numbers piece and let them substitute their real world numbers.

If you were to go to a locally procured battery I would do a marine/rv battery so there would be no maintenance. If you go with golf cart (2 - 6V) you need to worry about distilled water and equalizing to get decent life out of them.

I would not use the two 24 volt chargers unless they were servicing two batteries each, center-tapping the battery pack. Running the battery chargers in series to create 48v is not advised especially off of the same battery bank. Running them directly from the solar panels also not advised. The output of most 12 volt solar panels is around 17 volts, and by Avatar's recommendation 150 watts will produce around 9 amps. I am a little puzzled how their charger can state 240 watts output when 29.5 x 5 amp is less than 150 watts. Hmmm.

As far as buying used solar panels off of ebay, buyer beware, the panels are there for a reason, unless they come from a decommissioned perfectly running system and the seller will guarantee by sending you a replacement for a non-working panel I would bypass and consider spending the going rate of about $5 per watt and actually have recourse if the panel is a dud. The oldest solar panels out there can be as much as 30 years, and their watt output can be much diminished, also there are panels out there that are high voltage, but very low amps that were designed for water pumping solutions
that ran better with high base voltage - not usable for this application.

For battery-based solar systems (off-grid) the multiplier we use for figuring solar panel sizing is around 1.7 to account for Panel to p\Point of Use losses (wire, battery, and inverter).

Cheers
Jeff
84 Honda VF500 Franken'ceptor (hit 1000 miles this week!!) as seen on evalbum.

gusher, I think your calculations are about right. Something to consider is the efficiency of the charger you have which may be very poor. It might help a lot to buy a more efficient charger. You can get a more powerful inverter for pretty cheap, but I don't know about reliability. I have a 2,000 watt inverter that I got off ebay for $100 and it seems to work okay.

For solar panels, I don't recommend ebay. There are some other surplus sources on the web, but its really up to you to look around and find out if theres anything worth buying. Its worthwhile to check because there might be someone near you dismantling a system and selling the panels.

I like working with sealed AGM batteries much more because they don't leak acid or vent gas. They also might be a bit more efficient so they are definitely better for a renewable installation, but they are also about 3 times the cost of flooded batteries so its your call there. Whatever you get, don't get marine batteries, try and find those specially designed for deep cycle applications. Don't get UPS, or starter batteries either even though they might be cheaper.

If I'm storing power in batteries then how many batteries will I need???

Gushar

I recommend as much as possible that fits your budget, and minimum 100 ah at 12v.

I disagree on designing a system for 1/3 depletion. 50% would be the minimum, and 10 ah @48 volts is 480 watts (what happened to the 580 watt reasonable number from above?). So the 240 watts would be less than 1/4 and does not have any inefficiencies figured in. You're going to come up short with a single 60 watt, eventually needing to recharge your storage battery from wall current, okay if that's in your plan.

Where are you located Gusher, this will have a bearing on how many hours of full sun you can count on to charge your storage battery. Example: LA (Socal) would have 5.6 hours average, a low of 4.2 and a high of 6.6. These are the number of hours the panel will actually output at its rating (barring shade, overcast or intermittent clouds). I can give you accurate numbers for your locale. The angle for the collector(s) should be your lattitude, +15 degrees in Winter, -15 degrees in summer. The panel should be pointed to either true south (not magnetic) or light to the east of south (generally early sun is preferable to late sun).

Cheers
Jeff
84 Franken'ceptor (verified 21 mile range - stop and go 0-45 mph, bike could still maintain 40MPH max but battery was showing some sag and was less than 50% on Paktrakr)

Thanks Jeff for the input. I think at this point I'll just wait and try to learn a bit more. But again thanks to everyone who had comments. I've learned alot already...enough to know I need to rethink this and look at every aspect of it.

Gushar

I'd suggest looking up the nearest businesses that do solar installations to you and talk to them.