Newbie! - Panel needed to charge 18v (3 6v in a series)

[Classified]

I am VERY new to solar and electricity in general. So, please forgive my basic questions and respond assuming I know nothing. Please!

I have purchased 3 of the below batteries and wired them in series to a Power Wheels car to create 18 volts of power. My daughter has been riding this for a couple weeks and all is going well so I don't have any issues with running 18v to Power Wheels. (I visited modifiedpowerwheels.com to make sure this was good.) 18v is SO much better/faster than 12v

Batteries:

http://www.gruberpower.com/6-volt-12-amp-hour-ah-battery

I want to charge these batteries with solar power, just a fun project to learn and do something cool. I don't really want to just buy a solar panel, I would like to build one (I know, probably not the best idea but I am doing this to learn). I will move over to DIY for actual build but I am here because I don't know what I need to charge my batteries.

MY QUESTION:
How many volts/watts/etc do I need to put out to charge my batteries? I would like to put a roof on top of the Power Wheels that holds my solar panel, this way it can be charging the batteries at all times when the car is outside. I understand I will need a charge controller as well, so any suggestions there would be appreciated. Should I wire the batteries in series to the motor to get 18v but wire them to the charge controller/solar panel in parallel so I charge 6v? Is that even possible to have them wired both ways at the same time?

Possible Solar Cells:

http://www.ebay.com/itm/High-Efficientcy-3x6-solar-cells-for-DIY-solar-panels-GREAT-PRICE-ships-from-USA-/171705831315?pt=LH_DefaultDomain_0&hash=item27fa770f93

Or

http://www.ebay.com/itm/40-WHOLE-3x6-Solar-Cells-Factory-Short-Tabbed-1-8W-Each-/201390437137?pt=LH_DefaultDomain_0&hash=item2ee3ce3311

Or
Your better suggestion?

Thanks in advance!

[Mike90250]

Welcome.

Well, don't buy anything more yet.

18V is a odd voltage, and to properly charge batteries, you need to have a charger configured for 18V. Some small chargers from Morningstar are programmable with a computer and special data cable. http://www.morningstarcorp.com

12V or 24V are the common charge voltages that off the shelf gear is available for.

Sealed batteries need precise recharge voltages, any overcharge pops the safety vent, and electrolyzed water (H & O) is irreversibly vented and capacity is lost.

If it's not too late to configure for 24V system and 4 batteries, that would be a lot easier.

The 12AH batteries you selected could be fast charged at about 4 amps (but the data sheet is incomplete regarding this) and a PV panel of about 35V and 5A (about 200W) could recharge a dead pack in 3 or 4 hours of good sun. Building a large DIY PV panel out of scrap cells from ebay would be a interesting learning experience but not practical at all.

[Classified]

Thanks Mike
My research has led me to agree with you about 18v being odd to work with. I just figured I didn't know what I was looking for though. I see that 12V and 24V are common but what about 6V? Would I be able to charge these batteries from a panel in parallel at 6V, or is that an odd voltage also?

Thanks for the safety vent info, like I said newbie so I didn't know that.

It would be very easy for me to go to 24V but can't. Everything I have read says that if you put out 24V through the Power Wheels motors you will fry them.

Are you saying that a 35V/5A (200W) panel could recharge 1 6V battery in 3-4 hours?

When you say large DIY PV panel, what size are you talking? And by not practical? Sorry, remember I have done NOTHING with solar to this point but am very interested so I want to learn.

Since we agree that 18V is hard to work with, I want to reiterate the 6V idea. (Run the batteries in series (18V) to the motors but at the same time have them hooked up in parallel (3 - 6V) to the charge controller/panel. This way I get 18V of power to the motors, but only have to charge 6V.)

Thanks again!

[Mike90250]

there are few to none 6v solar chargers. So that is a dead end avenue.

Forget I said anything about DIY PV panels (from a kit of parts, cell wafers, tab wire, backing sheet, cover glass)

Are you saying that a 35V/5A (200W) panel could recharge 1 6V battery in 3-4 hours?

No, it would recharge the 3 pack of batteries all in a couple sunny hours.

[SunEagle]

Thanks Mike
My research has led me to agree with you about 18v being odd to work with. I just figured I didn't know what I was looking for though. I see that 12V and 24V are common but what about 6V? Would I be able to charge these batteries from a panel in parallel at 6V, or is that an odd voltage also?

Thanks for the safety vent info, like I said newbie so I didn't know that.

It would be very easy for me to go to 24V but can't. Everything I have read says that if you put out 24V through the Power Wheels motors you will fry them.

Are you saying that a 35V/5A (200W) panel could recharge 1 6V battery in 3-4 hours?

When you say large DIY PV panel, what size are you talking? And by not practical? Sorry, remember I have done NOTHING with solar to this point but am very interested so I want to learn.

Since we agree that 18V is hard to work with, I want to reiterate the 6V idea. (Run the batteries in series (18V) to the motors but at the same time have them hooked up in parallel (3 - 6V) to the charge controller/panel. This way I get 18V of power to the motors, but only have to charge 6V.)

Thanks again!

Even if there were solar chargers for 6v batteries you could not wire them in series (18v) to run the power wheels motor and in parallel (6V) to be charged at the same time. They need to stay in one configuration for both usage and charging.

While building (DIY) your own solar panel may be fun and educational, it is not practical due to the high damage rate of the cells during the soldering process and very short life of the panel due to moisture intrusion.

Another area to think about is that to get the most out of a solar panel, it needs to be directly facing the sun as much as possible between 10Am and 2 Pm. Mounting the panel to a flat roof will not get you much if any time to recharge the battery system which can over discharge and kill them quickly.

[PNjunction]

While building (DIY) your own solar panel may be fun and educational, it is not practical due to the high damage rate of the cells during the soldering process and very short life of the panel due to moisture intrusion.

I couldn't have said it better. And with today's panel prices usually cost-ineffective due to having to replace it with the real thing in a year or so.

The links show an interesting sales-tactic about how the cells are just a bit off "cosmetically". Far from it. Cells that fail the manufacturer's flash-test do not get any sort of ARC or anti-reflective coating applied before being pitched to the dumpster. This lowers the cells efficiency in the first place, nevermind "dark spots", missing "fingers", sloppy solder-paste etc.

Cells also have internal problems that may not be visible or detectable to the normal users, like micro-cracks that once put into a diy panel which heats up in the sun, crack wide open. Nevermind the lack of any ARC coating in the first place.

A DIY panel makes a good SECONDARY learning project after one has experience with a properly running commercial panel just for these reasons.

[Classified]

Thanks

I have been away and busy, sorry to post and ditch.

I hear you guys on the DIY panel and you have convinced me to not go that route.

*****
Do you have a recommendation on a panel for 18v? If 18 is just too weird to work with I might just convert our other Power Wheels to run off a 12v car battery and use a panel to charge it. And just charge the 18v the old fashioned way.
*****

BTW, my 5 year old LOVES the extra speed she gets on the Power Wheels. I am going to need to purchase new tires REAL soon, she peels out every time she takes off and is able to power slide, hit the "gas" and do donuts. Real funny and cool, but tears up those plastic tires.

Thanks Again

[PNjunction]

Do you have a recommendation on a panel for 18v? If 18 is just too weird to work with I might just convert our other Power Wheels to run off a 12v car battery and use a panel to charge it.

If you are looking to go that route, then do what the previous generation of EV'ers and mild-to-moderate users of custom wheelchair users do - ODYSSEY AGM batteries. They are pure-lead and very high-performance that you WILL notice due to the extremely low internal resistance. It is just short of going lithium.

Other AGM's (other than say an Optima, but that is too big for the toy car) PALE in comparison - most notably a higher internal resistance.

Thing is, these need a *decent* charger or solar setup. At least about 0.4C charge current of the 20-hour ah rating in your application, (or more - current isn't limited to a point, but charger absorb voltatge is) which is likely to get a pretty deep discharge. Get a voltmeter in the little car, and don't let it run down below about 12.2v, if your child can keep an eye on that before returning home.

If you can wing it, a Tecmate-Optimate 6 would do nicely on those smaller Odyssey agm's and of course your own solar.

[PNjunction]

An Odyssey PC-545 (13ah) or maybe an Odyssey PC-680 is what I am thinking about as a simple direct swap in for that "Gruber" ups style little agm, although you might have to reroute the terminal leads.

[PNjunction]

UGH! Still can't edit posts ...

Those Odysseys are 12v models, and you would need to make sure they physically fit. The Optimate 6 would make a fine 12v charger for this application.