Charging solution idea but help needed

[Pignut]

When camping (Often with the scouts) we do a kit drop with the car and then have to remove the vehicles.

For Health and safety reasons we need to have charged mobile phones at all times, so as a group charging facility I have come up with a solution.

I have a car battery (110mAhrs) and a solar charger (This is not a cheap charger, it is designed for the job)

My idea is to keep the battery in a coolbox and wire up the charger with a long wire so it can be placed outside of the tent etc

I will then vent the box to allow gasses from charging to disperse

And wire a couple of cigarette lighter sockets (Fused) directly to the battery along with a USB socket

Will this work? do you forsee any problem

Regards

 

[g4ghb]

I don't see why not. I wouldn't have thought you would necessarily need to recharge the car battery while in use, unless you are on camp for weeks, but if you have a charger then why not!

I have a car battery that is set up in a toolbox that I can use for jump starting etc and it works a treat!

 

[Ogri the trog]

It certainly sound like its a working solution Pignut, but why keep the battery in a cool box? Something to keep the rain off etc. sure, but why allocate a cool box to the task and have to go through venting it and so on? An open sided box placed where it wont be in the way with the solar panel fixed in place should be amply sufficient.

Ogri the trog

 

[Shewie]

I can't see why it wouldn't work either, maybe try it with an old cig lighter phone charger which you don't use any more.

I've probably got an old phone and charger somewhere if you want a sacrificial unit to test with.

There are some clever portable power units available but they can be pricey. Maplins might have a cheapy one?

 

[Pignut]

The point of a cool box........ the battery fit in it snugly, it was free and to hand LOL also easy to handle

Shewie Thanks for the offer we have a load of old phones and chargers kicking about also.

I am also going to mount a strip of LED on the front of the box (Switched) as a tent/emergency light

I am sure I will not need to charge the battery for a weekend but I can see it getting almost continual use on week long camps, besides I have the charger to hand.

I will post pictures when done if anyone is interested

Cheers

 

[Mr Finch]

We use a massive (physically) 900 Ah battery that one of the other leaders procured. This kept 16 mobile phones charged for 8 days at summer camp last year. We simply had a 4 port accessory adapter (cigarette lighter) which the person would then plug their standard car phone charger into.

Worked a treat!

 

[ged]

... I have a car battery (110mAhrs) ...

You can get 110mAh out of a button cell. If it's a car battery I think that's 110 Ah not 110mAh. That's a fairly big capacity for a car battery anyhow, like the one on my Jeep.

How much charge do you think you'll be needing? A typical mobile 'phone battery is about 1Ah (1000mAh). I'd have thought a fully charged car battery would charge the entire troupe's mobile phones for a month if they never stopped talking on them.

My idea is to keep the battery in a coolbox ...

Very bad idea. If the battery starts to warm up for some reason the cool box will prevent the heat from escaping. That could be dangerous. Think boiling sulphuric acid spraying all over your sleeping bag.

Will this work? do you forsee any problem

It can work. I've done something very similar with the battery pack for my Clulite. But I'm a Chartered Electrical Engineer and I ask myself lots of questions when I do something like that and while I'm using it. in your scenario the whole idea sounds a bit dodgy to me, and might pose more risk than those you're trying to avoid.

Car batteries

(a) are heavy
(b) are relatively fragile
(b) store of a large amount of energy which can be liberated very rapidly (I've seen thick copper cables vapourize explosively)
(c) are full of nasty chemicals like lead and sulphuric acid which escape when you least want them to
(d) are prone to generating an explosive mixture of gases as you know
(e) need more maintenance than they deserve

My professional opinion: Don't do it. There has to be a better way.

 

[mountainm]

I think you'd be better off with summut like this:
http://www.thinkgeek.com/interests/dads/962e/

 

[ged]

Or something like this:

http://ikonglobal.com/

 

[Zingmo]

Yep it will work fine. I'm sure you won't be disolved by acid in your sleep if you've got half a brain! A leisure battery (as used in c***vans) will work better.

Z

 

[spandit]

USB runs on 5V, not 12V (although a 12V battery is closer to 14V)

I think the chance of overheating the battery is fairly remote unless you short it with a thick bar. I've got a leisure battery in a box.

Bear in mind that a normal car battery is different to a leisure battery. The latter doesn't mind being drained of charge whereas that will pretty much wreck a car battery. On the flipside, a car battery can handle much higher loads (like starting a car!) that would damage a leisure battery.

My battery was about £45 off eBay and is 110Ah

 

[blacktimberwolf]

What's wrong with this sort of thing ?...http://www.amazon.co.uk/Wind-Up-Mobile-Phone-Charger/dp/B00062UXIG

or this...http://www.paramountzone.com/rphone.htm

 

[Damascus]

Hi,
Try and find some old fire panel 12v 7 A/H batteries, it will keep a mobile charged all weekend if needed. The best thing is you can put it in your pack, they are about 6x4x3 inches in size and doesn't weigh as much as a car battery
D

 

[Pignut]

Weight is not an issue...

I am quite concerned about being dissolved in my sleep,

This idea simply stemmed from having the bits lying about. It was my intention not to have the lid on whilst in use

 

[Teepee]

I've been using the same battery for general charging for 4 years now, came out of an old invalid carriage. Its a 50 amp leisure type battery.

It will run a small tv and xbox for over 2 hours with a 240 V Inverter in the cold. Recently been using it to pump up my inflatable boat, charge camera and phone.

Your plan is fine and well tested. Don't worry about keeping the rain off it though, lead acid batteries sit quite happily in fields powering electric fences with no protection. 12v dc will not pass through water unless it is salted. Just make sure its fused.


As Spandit says; Car batteries are permanently damaged when they discharge below 80% of full capacity, keep it charged and it will last well.

The coolbox isn't a good idea though, easy to forget the lid is on and Hydrogen is very explosive. I've seen a small lead acid battery explode, it made a proper mess of the workshop!

 

[rik_uk3]

http://www.dealextreme.com/p/aa-battery-usb-emergency-backup-power-and-charger-pack-15048

Less than three quid each, I get about 2.5 charges from flat off 4 AA'a with my G1, does a week for me. Buy 5 and tell them to get their own AA's.

 

[Pignut]

The idea behind this is that it will charge laptop, iPad iPod phones etc etc, run a light... If I use the toolbox but permanently vent the side will this negate heat and gas build up?

 

[spandit]

Probably but try it at home first to see if it heats up at all. In a tent porch the hydrogen gas would probably disperse fairly quickly anyway but don't start playing with sparks too close

 

[ged]

The idea behind this is that it will charge laptop, iPad iPod phones etc etc, run a light...

Ah, quite a bit more than a couple of 'phones then.

If I use the toolbox but permanently vent the side will this negate heat and gas build up?

I'd think that would be a lot better although I'd be a bit nervous about somebody thoughtlessly throwing a spanner in the box thinking it was really a tool box and shorting the battery terminals. My preference would be for a wooden box rather than a metal one to minimize the risk of a short circuit, which is VERY dangerous on a high capacity lead-acid battery. You need to think about fault conditions all the time with these things as a fault can be so dangerous.

Even apart from accidental short circuits, lead-acid batteries can and often do unexpectedly produce a lot of heat. The most usual case is when a fault develops in the battery and either it discharges one of its own cells quite quickly, or else when you try to charge it with a non-intelligent or faulty charger, and one of the cells is down (probably short-circuited by fragments of plate material which inevitably fall off the plates with use) and as a result the charging current is too high. It's also possible if the battery is overcharged, again that will usually be if the charging circuit isn't intelligent or is faulty. I've seen batteries wired in parallel to get more capacity, which seems fine until one of them develops a fault and the others suddenly pumps all their charge into it. In addition to a lot of heat, all these cases may also produce a lot of gassing. The casing of the battery usually buckles and sometimes cracks, which will usually release the acid if it's a wet battery and not a gel type. A tray at the bottom of the case to catch acid in case of a leak is a wise precaution.

Others have pointed out that vehicle starting batteries are not designed for deep discharge and will have a very short life if used in that way. Even 80% discharge is a lot for a starting battery and I'd say limit it to 5% if you want a long battery life. The battery doesn't normally just die, you will usually see a gradual reduction in the charge capacity. A "deep-cycle" battery would probably suit your application much better, but they tend to be more expensive and a little more difficult to find. Still, all things considered, if you can find an alternative to lead-acid I for one would feel much happier.

Edit: Oh, and since you're camping, if the battery is very cold it needs more care. If the electrolyte is frozen don't even try to use it.

 

[Pignut]

Hmmmm lot to think about