Does a solar charger work?

i think it will work, but how long to you plan to be idle?? there is a way to protect your 12 v battery from discharge for periods of 2 months. that would be easier and cheaper.

i have a portable radio that runs on solar, i would venture to say that even that would be enough to keep the battery in good shape if you disable SKS, etc.

 

150 mA is a 1.8 Watt panel; you only get the full 150 mA when the panel is directly lit by bright, overhead sun, so that's an hour or so a day in southerly climates in the summer, much less in most other places, especially since it is also dependent on how and where you park your car... If you're behind glass (ie, behind windshield on the dash, count on the output being cut 60% or more, particularly because of the solar-absorbing high iron-content glass used in the Prius. Then, also remember the parasitic drain caused by the systems that remain powered in the Prius even when the ignition is turned off. These drains are present 24/7 whereas you only get half that in terms of sunlight, and again, only the brightest part of the day actually contributes to any appreciable charging..

My own calculations and measurements show that for an in-car (behind glass) system, a *minimum* panel size of 5W is required for a minor trickle charge, and that's in totally ideal conditions.. In more typical conditions, behind glass and without direct sun, a 5W panel under load gives out enough to offset the parasitic load and not much more; certainly not enough to account for the drain at night when there is no contribution from the panel..

You can get larger panels that will definitely work, but most will need to be externally mounted due to their size.. This is both a good and a bad thing- good because the output will be greater if they are not behind the car glass, but bad because of the potential for theft or vandalism..

So, basically, the answer is that if you're thinking of one of those little tiny 6" x 12" 1-2 Watt panels that sit on your dash, forget about it.. a mid-sized 5W panel is the minimum size that will give some minor benefit, but for a system that can maintain the 12V battery indefinitely, you're looking at large solar panels that will be a challenge to mount.

 

I have a similar question, but a little more complicated.

We will take delivery of our 2006, package #8 in about a week. We get to enjoy it for less than three months and then we leave for Europe for 4 to 5 MONTHS. Ideally I would like to park the car locked in a garage for that time. Our daughter would love to drive it for us, but then we would have to leave it outside.

The Toyota salesman tells me to use a trickle charger on the battery. Fine, I say, but what about the NiMH batteries. No problem, he says, the little battery will charge the big ones. No, says I, I don't think so. Well then, he says, charge the big batteries directly, you can buy a kit to do that. I said, Maybe but it is very expensive and it voids the warranty. He says, No its easy and it does not affect the warranty. I said OK.

So now I need help from you guys and gals who know what you are talking about.

 

Well... I wouldn't describe myself quite like that... but I will tell you my experience with NiMH in my full battery EVs.

Leave the NiMH battery fully charged, and don't worry about it. At the SOC level that the Prius allows, the self-discharge rate is less than 1% per week. You should be just fine when you get back. I would recommend using some sort of high quality charger on the lead-acid Aux battery though. And no, of course the Aux battery cannot back-charge the traction battery.

 

1)Don't ever listen to that salesman again... he does NOT know what he's talking about.

I already knew that, I just wasn't going to argue with him! He was a nice guy. You should have heard what his boss told me (he was a real a**hole, rude and beligerant); tried to sell me every possible dealer add on and make me feel stupid for not wanting to buy it. I told him I just wanted to sign the papers for the MSRP plus tax & licence and get out of there. I hate to deal with people who lie to me.


2)6 months is how long the HV batt is supposed to hold it's charge unused.

That's good news. I am very familiar with high capacity deep cycle 12 volt wet cells on boats and I never let them discharge more than 50%. I had no idea what the static current draw was for the Prius. Outside of my digital camera batteries I don't know much about NiMH batteries


3)Why can't your daughter pull it out of the garage once in a while to drive and charge it?

Well, that's complicated. Parking is difficult, two other cars will be parked in front of it, one of them belonging to our renter whom we let use the single driveway when we are gone. I could park it in her driveway, but there it is unprotected from weather and possible vandalism. I am concerned with the complexity of the car if she got into a situation where she was stuck, or the car wouldn't start or run.
Also, and I hate to admit this as she is a very good driver and we borrow her Tundra when we need a truck, I really don't want ANYONE else to drive it for a while. (My wife would say: It's just a car!

Thanks for the feedback. I have a old 15 amp charger that's great for recharging a depleted battery, but for this I would like to have a trickle charger. Any recommendations would be welcome.

 

Be very careful when selecting a "trickle charger"- most of them are simply a low-wattage transformer with a diode on one leg forming a crude half-wave rectifier.. These things have absolutely no voltage or current control and if left on and unattended for an extended period, some models can damage batteries..

What you need is either a trickle charger with a charge controller on it which stops the charging when the battery is full; these are are available, but somewhat expensive due to the extra electronics, or for not too much more money, you can replace the old 15A "dumb" charger (which is really just a big scaled-up version of the "trickle charger") with one of the new intelligent computer controlled chargers.. These inverter-based (no big transformers) chargers will quickly charge a depleted battery, then go into a top-up mode where they do a controlled trickle charge only when the battery needs it, so you get the best of both worlds- just connect it to the battery and let the computer take care of things..

As for the NiMH battery, if you are going to be gone for an extended period, the one thing I would probably do is one last drive before I leave where I try for as much regeneration as possible to get the battery up to the green zone before you parked it, but in general I wouldn't worry too much about it..

Personally, I would let your daughter drive it- if you can't trust your own child, who can you trust?? And after all is said and done, your wife is right- it's only a car..

 

For charging the 12V battery, you could use a Battery Tender unit. Motorcycle riders recomend them highly, and I just got one for my bike. It has a trickle charge mode that will charge the battery when it needs it, and an automatic float charger that will keep the battery where it needs to be for months at a time without damaging it. It seems to work very well for bikes and I see no reason it wouldn't work on a Prius Aux battery. It comes with fused cables you can wire to the battery that have a connector on the end to plug into the main unit for charging. When you're done, disconnect, cap off the connector with the cap that's mounted to it, and you're done. You could hide the wire behined a panel or under the false floor in the hatch when it's not needed. It also comes with alligator clips if you want to do it that way. I paid about $20 for mine.

 

Thanks, I'll look into that. At $20 might it fall into the category that C4 warns about?

 

The 12v system disconnects when the engine is off. You'd need to rewire the switch to keep the 12v on if you want passive solar charging with the car parked.
B

 

Here is just the thing, a "Float" charger. Only $10 at harborfreight...
http://www.harborfreight.com/cpi/ctaf/disp...temnumber=42292

 

I use a VDC Battery Minder at my hobby farm on the batteries for my tractor, garden tractor, and old Ford pickup. They work very well and you never have to worry about ruining a battery by overcharging.

http://www.vdcelectronics.com/batteryminder_12112.htm

Note this unit will only condition and keep healthy a fully charged battery. The instructions state it will burn out of used to charge a seriously discharged battery.

As far as that goes, just remove that tiny 12 vdc battery from the Prius anyway. You're keeping it locked in the garage, right? I was overseas on business for a month and removed my Prius battery with no real issues. I left it hooked up to a Battery Minder while I was gone.

I did have to "normalize" the power windows and do the radio presets again. That's fine, I only listen to a couple of stations anyway.

 

I have this one in mind when I get ready to buy for the cars I don't use now that I have my prius!.... when you trickle charge and then at night it drops to nothing.. it really shouldn't hurt the battery any more than driving it every day......

Unless you boil and get it how and lose the electrolyte, it shouldn't hurt a thing... a solar charger will not do that unless it a very big one...

Here it is.... http://www.batterystuff.com/solar-chargers/

I had my eye on this 6.5 watter http://www.batterystuff.com/solar-chargers/PF6.5w.html
thats 30 inches long to fit on the dash "protects from sun too!"... If you feel you are getting too much power... just fold one or two leafs over so the sun can't see those cells!..

It looks very versitile for camping, hiking, and is very durable and compact..and is only 79.00.

Some of the cheaper models are rediculous on the amount of power they deliver as well as they are not very variable in thier use!..

Have fun!

 

The charger Jayman has suggested would fit the bill for maintaining a car battery indefinitely, but at $60, as I said, it's a somewhat expensive unit- for about $10-15 more, you can pick up a microprocessor controlled "smart charger" with the same desulfation and maintenanance modes, but also with the ability to full-charge batteries at 10-15A rates.. The Harbor Freight unit is quite obviously one of those diode-and-transformer jobs- this one has an extra box on the wire that may or may not do something, but I certainly wouldn't risk a battery by using this device..

As for the solar panel, if you're putting it on the dash, under glass, trust me, you will not get anywhere near 6.5 Watts- because you lose >50% to the glass, you'll have to leave the whole thing exposed to get any meaningful charge to the battery..

 

I think you made a typo.. you said 6.5 watts and mean't amps...

Thats why I prefer this larger unit.... this would put out around 700 watts in full sun.. you don't need near that much... even one - two amps is fine for trickle charge. "about one light bulb"

And so its not misunderstood.. this is only for the 12V battery to initially start the car "to boot up the computer"... the voltage is all wrong to charge the NiMh battery and is not necessary anyway.

I like the idea of not having to have extension chords running around all over the place outside and chargers people can steal.. this way, its all in the car. You can run thin wires out the door to underneath the hood if you won't want to tap into the system.

 

I agree. I already had quite a few conventional battery chargers sitting around, including a commercial 200amp unit that I bought at an auction.

I guess I was just impressed by this little wall transformer that could maintain the batteries.