say it aint so....

[superben]

the battery is a "deep cycle marine type"
12 volt

and it would be silly to charge a "charged battery"
nice try

[superben]

the circuit uses milliamperes to change the voltage...

think of it this way... it is easier to make volts than amps...
so your solar cells "in parallel" makes the amps... why not trade a few milliamperes to boost the voltage?

[Mike90250]

the circuit uses milliamperes to change the voltage...

think of it this way... it is easier to make volts than amps...
so your solar cells "in parallel" makes the amps... why not trade a few milliamperes to boost the voltage?

I think you are missing the boat.

.5V 6A PV cell = 3 watts
5 in parallel = 15 W (.5V @ 30A)

Converting that up to 14V (needed to charge 12V battery) you only have 1.07A, which is not much of a charge. (conversion losses will eat about 10% of the total wattage, leaving you with only 0.96A in real life)
So that's why panels are built with series cells, because it's very easy to get rid of wire losses, and keep them below 1%. Conversion losses of less than 10% are very rare/expensive.

[Uechi Kid]

So what would you need to make a trickle charger for say a camper that's not being used?

[crxvfr]

So what would you need to make a trickle charger for say a camper that's not being used?

That's a snap. Even the Harbor Freight 45 watt kit would work for that, which incidentally, at least in my area, will be on sale for $159.00 4th of July weekend. I have one on an automotive battery that gets used daily, albeit, not much, even still, the battery is always topped of. ( Its only been hooked up about a week and a half )

There are others much cheaper. I don't know how well they will work. I got my HF kit so I could get my feet wet with solar panels, charge controllers and inverters. The cheap ones hook straight to the battery. You can do that with panels sometimes too.

...now, back to the topic at hand >> Conversion losses

[Uechi Kid]

I also have a CPAP machine that when I'm camping I run from an emergence jump start pack with an inverter built in. I can get about a night and a half from that battery. I'd like to be able to charge it with a small solar panel if possible. What would I need to charge that battery every day?
Thanks

[Mike90250]

I also have a CPAP machine that when I'm camping I run from an emergence jump start pack with an inverter built in. I can get about a night and a half from that battery. I'd like to be able to charge it with a small solar panel if possible. What would I need to charge that battery every day?
Thanks

Somewhere, on the jump start pack, is a label that identifies what size battery is inside (30ah 12V) or something like that. You then need to determine if it is a GEL or AGM battery, they take different charge voltages. Is there a jack on it to recharge from a car cigarette lighter socket? What about the wall wart charger that came with it, what are the output numbers on it (18V dc 300mA) or something. Then we can figure what sort of PV panel you can safely use to recharge.

[Uechi Kid]

This power pack has no information that you said I need to know. Short of taking it apart I don't know where I'd find it. I even spent about a half hour searching the web and nothing.
Thanks

[Mike90250]

They range from 10AH to 50AH capacity. Nearly all are a lead based battery. But without more data, I can't safely say what you can charge with.

The AC powered wall wart HAS to have specs on it, of what it outputs. If you can cobble together solar panels that emulate that output, and get a plug that fits the unit, you should be all set.

[Uechi Kid]

Thanks for your help.

[russ]

Maybe they should have talked to you - pasted PV cells all over the space shuttle and saved all the problems with the hydrogen, oxygen etc!