Any good experience with solar chargers?

[GavinBKK]

Not necessarily Mac-specific, so here is my question:

Any good experience with solar chargers, preferably with USB connectivity?

I am going on a camping holiday in England (OK, don't laugh!) and need to keep several iPads, one iPhone and a couple of Samsung devices charged to a basic level each day for 12 days.

TIA!

[DeltaMac]

I spent several years in England, so I have to ask:
Where in England would you expect to see the sun for 12 days in a row?

I searched around, and most solar chargers appear to be designed for one unit at a time.
But, this one looks promising: http://www.amazon.com/sCharger-5-Pow...ata/B003ZFQUWO

[GavinBKK]

Answer: I don't! :-).

Need to try though, as will need email access when there. Know anyone who has used one of these?
Tx!

[acme.mail.order]

Where in England will you expect to have internet but zero access to power?

Van camping? Problem solved with a 12v adapter.

[GavinBKK]

I am an exhibitor at the annual War and Peace show. Military vehicles are invariably 24 volt. This means disconnecting the batts to use such an adaptor and on an open vehicle, that may not be a desirable thing to do. I have an M151 A2, ex-USAF Security Police, this one, in fact:

http://www.flickr.com/photos/gbpmi/1...in/photostream

May have to be the way to go though.

[acme.mail.order]

Seems to be readily available:

http://www.google.com/search?q=24+vo...hl=en&tbm=shop

(and your picture is set to private view)

[GavinBKK]

Pic is public now. I remember locking it down after my pics got ripped off and used in adverts some years ago.

Thanks for the link - sharp knife and some croc clips and that will do then.

Thanks!

[acme.mail.order]

What, no M131 on the back? Shame.

Try these instead of croc clips - much safer. Available at auto parts shops anywhere - requires a pair of pliers and some electrical tape to install.

[GavinBKK]

A semi-trailer fuel bowser??? Need an M54 for one of those...

When I said croc clips, I meant the large ones to connect to the battery terminals. The batts are 45Ah each, so they won't break a sweat with iDevices attached. Just need to keep on the right side of the Weather Gods...

[acme.mail.order]

D'Oh! Must learn to proofread, esp. as the "edit" time here is about 2 minutes.

Meant M134.

Are the batteries 24v, or do they put 2 in series? if you are going straight to the battery terminals you will always get the battery label voltage.

[benwiggy]

Quote: Originally Posted by DeltaMac I spent several years in England, so I have to ask: Where in England would you expect to see the sun for 12 days in a row?

Hey! We do have summer, you know. Just not this year.

[acme.mail.order]

April, 2011 was very nice.

[GavinBKK]

2 in series.

An M134, or even an M2HB Browning would rip the floor out of a MUTT. They were kitted for an M60, sitting on an M4 pedestal. Mine had one in service. I do have a PRC-77 on it, as it would have had in its original role. The harness has no PTO, so I have to come off the batts, which means opening the battery compartment, with the aforementioned weather issues...

[GavinBKK]

Summer is on a Wednesday this year..

[acme.mail.order]

Quote: Originally Posted by GavinBKK ...would rip the floor out of a MUTT.

And it would bounce around so much you wouldn't hit the broad side of a Nissen hut. But that's not the point - it's sufficiently intimidating (at least outside a bona-fide war zone) that you'd never need to turn on the power.

Getting back to the battery - you're fine with a 12v adapter across one battery.

[GavinBKK]

But I would need to isolate the other battery, yes?

[acme.mail.order]

No. Hook up your leads to either battery and you will get 12 volts. It can even be running at the time.

You only get 24 volts if you go from ground on battery A to positive on battery B.

Small point: you should make quite sure the negative lead goes to the vehicle ground - in other words you are using the "lower 12 volts" of the system. Either that or make absolutely sure no part of your system touches any metal parts of the vehicle's system, as your iGround would then have a potential (and direct short) of 12 volts to the vehicle's ground.

Hasty ascii sketch:

(ground/frame) =|--0[battery A]+-0[battery B]+-->>vehicle
                  |             |             |
                  |     12v     |      12v    |
                   \-----------/ \-----------/
                       safe           risky (but will work)

FYI multi-tap transformers work on the same principle.

[GavinBKK]

Ok, that is crystal clear, many thanks. I keep sections of an old inner-tube for just such things, so that will be fine. Believe it, or not, when I did my engineering apprenticeship, agreements with the Unions actually forbade us from learning anything electrical, or learning to weld. Trades Descriptions, I think they called it. I had to pickup my vehicular electrical knowledge OTJ restoring old motorcycles and later military vehicles, although the Mvs are like Lego and are effectively plug-and-play. Some years ago, I successfully rigged up a system in a borrowed Ford Mondeo to power the PowerBook that I had at the time, using some bits and pieces I bought from Halfords, a UK car-accessory chain. That was in the days before in-car adapters were easily found.

[GavinBKK]

As a point of interest, why is the "second" battery risky?

[acme.mail.order]

If you use the 'upper' battery, the ground of any connected devices has a potential of 12v compared to the vehicle. So setting your iPad on the hood would create a direct short between the positive of the first battery and it's ground, via your iPad's metal case. Please video the resulting meltdown.

If both systems are fully isolated it doesn't matter.

This problem also occurs between buildings with copper network wires. If they aren't isolated and/or grounded properly you can have a rather dangerous potential on your computer's case due to ground-voltage differences.