Solar Powered Portable Generator to Recharge my Electric Bike.

solutionsgem's picture

We have always wanted to become energy independent. We ware finally able to do it a few years ago when we got our 3 kilowatt photo voltaic system. By then we thought we only needed our electric vehicle to become independent from the oil companies. We got ourselves a XB-700Li Lithium power scooter on August 2008. We advertise the scooter as a Solar Powered in our area. People ask us how we power the scooter with the sun. For people familiar with Photovoltaic systems ask me where the solar panels are. We did think about installing solar panels on the bike but we quickly realized that was not a good idea because of weight and sun damage.
It is a great way to start a conversation. We explain that we have a Photovoltaic System at home. Then they ask me how much is the system. We have to be honest with them. It is an expensive purchase up front. But with all the incentives and tax breaks my system should paid itself off in seven years.
That to must people is too long and risky.
That got us thinking into building an affordable portable photovoltaic generator to recharge our bike. We liked the idea because it serves a dual purpose, it recharges our bike and it is a back up/emergency battery for all our computers. We wanted to stay under 300 USD.
We started with two SunPro automotive 15 watt Solar panels, one Exide Orbital Deep Cycle Non Spillable Battery. We liked the Solar panels because they include a Charger Regulator with each panel. The regulator helps protect our battery from overcharging. We then used our 300 watt DC to AC Inverter we already own. We have no idea how much energy the battery is capable of storing. The most we have drained it from the battery is approximately 400 watt/hour. We had to stop draining the battery because of the low voltage alarm went off in the Inverter. We measured the watt/hour with our Kill a Watt meter. We know the 400 watt/hour number not accurate because there is much current lost in the conversion from 12 DC volts to 120 AC and back to 48 DC Volts. We know there must be a more efficient way. That would involve a direct conversion from 12 to regulated 48 volts.
Does anyone know how much energy those orbital Lead acid batteries hold?

Here is the battery:


He is a closer look at its specifications:


We got the orbital battery because we were told they were easier to store and that it would not spill any acid.

Here are some of the connections, the DC to AC converter and the battery charger regulator that came with the solar panels.


Here are our two 15 watt rated Solar Panels on our roof facing South


We do not ride our bike on long trips. We have only put about 1000 miles in eleven months of owning it. The generator is almost enough for our riding needs. We sometimes use the regular AC outlet to finish charging the Scooter after longer rides.

We will eventually install a second battery and perhaps more solar panels. These solar panels are not very efficient but for the cost they are fine.

We recently found these same SunPro panels on sale at Costco for $250. The package included four 15 watt panels for a total of 60 watts, mounting hardware, battery charger regulator and a DC-AC converter. We though that was a very good deal. You can find a similar deal at eBay.

Harbor freight sells a similar package that produces 45 watts. Here is the link:

Our set up is not perfect and not much electricity is stored but it helps become oil independent on a budget.

Let us know what you think.

before comments


100 RC minutes = 41.6Ah at 25A load at 100%dod.
which is around 450-500Wh.

ideally you would not use more than 80% of that. Marine batteries have a poor service life in deep cycle applications.

stepping voltage up is a bit tricky. Down is alot easier.

If you bought 2 more panels, you could hook them directly to the scooter batteries (via the BMS).


Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC

Or go ahead and carry the panels with you...


solutionsgem's picture

We wished we knew how to hook the four panels directly to the scooter batteries. We are not sure the bike came with BMS. What would you make sure the battery is not overcharged?

Thank you for your input

Energy Independence For A Bright Future.

solutionsgem's picture

We though about this exact thing. But as we mentioned in our first comment, the additional weight and sun damage to the scooter keeps us from going that route. Besides we like to ride two people in the bike. We also though about building a roof on the bike, but again size and weight would be too much for the bike.
We found the fixed panels to be our best option with the lowest cost. The generator also serves as a battery back up for our electronic devices in case anything happens.

In the future we might consider four solar panels connected directly to an additional Li battery, like antiscab suggested . We just need to find out how to do it safely. There would be less energy wasted to charge the battery. That way we will have a back up battery for our scooter and one battery will always be charging. Just a thought

Energy Independence For A Bright Future.

kevin smith's picture

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in my videos on youtube...
name is otleyshev68
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Perhaps build a string of PV panels that outputs 52V, then build a custom charge-controller. This may limit you to using a 48V battery type that handles this type of charging well, but it would be newsworthy. Get the bugs worked out and I think you could sell some of these to wealthy early-adopters.

It would be great if I worked somewhere that my boss would allow me to permanently mount the 52V panel at work in a secure area (sun only shines during the day when you're at work) With a big enough battery, you could ride grid-free both ways.

48V is a common home RE battery (windmill/solar) so it shouldn't be hard to find that voltage of a panel, or charge-controller circuits.

edit: removed double post

You really want as many batteries as you can afford, and a minimum of 120 watts worth of panels. The good thing about solar, though, is you can add as you go. Grab those four panels at CostCo, and one more battery like the one you have, and you'll be well on your way. As a matter of fact, two batteries paralleled with three 15 watt panels each charging them may very well be all you need, as long as you aren't riding very often, or very far.

You are right with that. But what do you think about this Please leave me a comment. Thanks.

solutionsgem's picture

Hi, That is nice looking solution but very expensive. You can make it yourself for much less with readily available parts. We spent less than $300 and our solar charge is still working.

Thank you for the link

Energy Independence For A Bright Future.


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