Replacing alternator with solar panel array on roof?

[blackjackel]

I just had an idea... what if I could buy a tiny lightweight battery charger that I can keep inside my car under the hood and I Can rig some sort of windup power spring thing to where i can pull out the power plug and plug my car in to charge the battery every day... But its so confusing with all the different kinds of chargers and powers etc..

[blackjackel]

Originally Posted by blackjackel

I just had an idea... what if I could buy a tiny lightweight battery charger that I can keep inside my car under the hood and I Can rig some sort of windup power spring thing to where i can pull out the power plug and plug my car in to charge the battery every day... But its so confusing with all the different kinds of chargers and powers etc..

In addition to the lightweight trickle charger, you could replace your regular battery with a deep cycle battery so discharging it won't do too much damage...

[MetroMPG]

Originally Posted by larryrose11

CarloSW2,
In my experience, a charge controller is unnecessary for anything less than 100W while charging pB-A battery.

I think it depends on the battery (style & capacity). I've been running my 80w panel with no problems wired directly to the series pair of 6v 225ah floodies in the car. But when I ran it to a parallel pair of 12v 7ah SLA's, the voltage rose very quickly and they started gassing. If I'd left them hooked up, they would have fried in no time!

[blackjackel]

so has your panel been enough to keep your battery charged or do you still need to plug it in sometimes?

[cfg83]

MetroMPG -

Originally Posted by MetroMPG

I think it depends on the battery (style & capacity). I've been running my 80w panel with no problems wired directly to the series pair of 6v 225ah floodies in the car. But when I ran it to a parallel pair of 12v 7ah SLA's, the voltage rose very quickly and they started gassing. If I'd left them hooked up, they would have fried in no time!

I went to my parent's house and it was sitting in the garage. Here are the specs :

Make        Model     Pmax   Vpmax   Ipmax   Isc   Voc   Length   Width  
Uni-Solar   MBC-262   11     15.60   0.70    0.9   21    28"      16"

I don't think it would hurt the battery, it even said so in the instructions. But I don't want to take any chances because battery's are expensive and the charger/protector is only $20, so it's a safe bet. Assuming interior car temperatures do not upset it, the solar panel can fit on my dashboard. Maybe it could even be an interior window shade when parked.

Hrmmmm, this might be a good sign (depending on what they mean by higher temperatures) :

(Page 100)
http://www.collectionscanada.gc.ca/o...01/MQ31541.pdf

5. The performance of the Uni-Solar MBC-262 PV module that utilized arnorphous
silicon solar cells improved at high ternperatures.

It's over ten years old, so it might just die on me. I am thinking that the best thing to do would be to :

1 - With the engine off, take a battery voltage reading (I can do this using the cigarette lighter).
2 - Park it at work all day with the dashboard window facing south.
3 - With the engine off, take a battery voltage reading.

If it works, it should always be better than when I park the car. If nothing else, it should keep my battery topped off (it's not a deep-cycle battery).

CarloSW2

[larryrose11]

MetroMPG,
your right, I should have been more clear. I was under the assumption that we were talking about deep cycle battery of significant capacity, like your 6V, 225 AH (Trojan T-105's?) Something small like the 12v 7ah SLA's would gas in no time. Sla's can be sensitive too.

CarloSW2, deep cycling a normal starter battery will kill it fast. because they can handle being discharged for very long. Put in 1 or 2 big deep cycle batteries, you do better.

[MetroMPG]

Originally Posted by blackjackel

so has your panel been enough to keep your battery charged or do you still need to plug it in sometimes?

So far I've only done two charge cycles, and it's been enough to refill the batteries - if only because I don't use the car daily - it pretty much takes 2 sunny days to bring the charge back up to full. I've only gone a couple hundred km without the alternator.

Originally Posted by larryrose11

I was under the assumption that we were talking about deep cycle battery of significant capacity, like your 6V, 225 AH (Trojan T-105's?)

They're actually old Exides - but with the same specs as the T-105s.

[MetroMPG]

CarloSW2 - I'm sure you can leave that panel directly connected to the battery. I have a similar slightly larger panel - 15 watt, 1 amp - and it's been supporting my near dead starting battery for more than a year, directly connected.

Why is it near death? Because I ruined it in 2006 with multiple deep discharges when I first started experimenting with a charge-depleting 12v approach! It has very little capacity now, and the panel is just delaying the inevitable.

[Noel]

MetroMPG,,,, have you ever done a test to see the difference an extra 100lbs does to mpg?

That's one I would be really interested in. (I don't have a scanguage)

[MetroMPG]

I haven't. EPA says up to 2% decrease for an extra 100 lbs. (http://www.fueleconomy.gov/feg/driveHabits.shtml )

But there's no question that the weight penalty of carrying 130 lbs of golf cart batteries is far outweighed (pardon the pun) by the efficiency benefit of removing the alternator load from the engine.