Hello everyone. I hope maybe one of you can help me with a little project I've started to make my SHARP GXM10H boombox a little more economical.
I'd like to figure out a way to hook up a small 12v car battery to my boombox via the DC 12v port that it has. Currently I have to put in 10 D cell batteries which have to be high-drain ones as otherwise the boombox won't pull enough juice to operate without turning itself off, this is as you can imagine quite expensive and for some reason the manual says NOT to use rechargable batteries which is odd and I still don't know why they'd be a problem.

I looked into rechargeable batteries but 10 of those from a decent brand with decent reviews cost a lot. So I looked into hooking up a car battery to it which the manual says is possible through the DC port at the back.

The car(cigarette) adapter which you have to buy separate plugs into a 12v 4.5a (cigarette)socket, I don't own a car nor am I very car knowledgable but that's what it says in the manual. So going from that I've gathered the following items, but before I buy the lot I want to know from one or more of you, whether I'm on the right track that this setup will work?

Charger: http://www.amazon.co.uk/gp/pro...;smid=A3P5ROKL5A1OLE

Battery: http://www.amazon.co.uk/gp/pro...;smid=A2F7JHI085LIYE

DC Jack adapter (connect to the battery terminals with 16 gauge wire): http://www.amazon.co.uk/gp/pro...;smid=A3HPPA3QGG4O6D

DC power extension cable: http://www.amazon.co.uk/gp/pro...;smid=A15TW43BF9Y9WW

Here is a simple diagram of the project:


Couple of questions I have are:

1. Is the battery fit for purpose?
2. Will the connections/wiring get too hot at all?
3. What kind of solder should I use to solder the 16g wire to the battery terminals?
4. Will the charger I found work considering it only outputs 4a and the battery is 4.5a? As far as I know it only means it'll charger slower right?
5. Do you see any other problems with the current project?

Many thanks for any help or advice you can give. As you might have noticed I am new to the forum so please, If I've violated a rule or policy please let me know and I'll try to rectify it.
Cheers

Quil

Do you have this SHARP GXM10H yet?

Can you post a picture of the battery compartment?

Here is a Idea of putting a Gel Cel into the battery

compartment instead of the the D batteries  

Yeah I've already got it.
So you're thinking of using a Gel Cell Battery instead of a car battery?
I never thought i'd be able to fit a battery in the compartment itself. I knew I'd have to carry it separate if I got a car battery but if the battery is decently small then that wouldn't bother me.

Here are some pictures with measurements:
The battery bay is Approx 2.8 inches deep to the edge of the battery bay, which is 12 inches wide and the bay is 4 inches deep to the battery cover.

Cheers
Quil

Here's a Idea for a Rechargeable battery to use in there

http://www.batteriesinc.net/ps1220.html

http://ep.yimg.com/ca/I/yhst-2...181659_2260_92222920

GC1215 12 volt 1.5 amp hr Rechargable Gel Cell D Battery comparison

The Links above give this specification's

12 Volt 2.5 AH Powersonic PS1220, F1 Terminals, Rechargeable Sealed Lead Acid Battery
Absorbent Glass Mat (AGM) technology for superior performance
Valve regulated spill proof construction allows safe operation in any position

Ah I see. So do I have to get a battery that supplies the same amperage as the car cigarette socket which in the manual is 4.5 amperage?
I understand if I get a lower amperage battery I will not be able to fully utilise the boombox as in, I'll have to keep the volume lower than it can go because it can't pull the amperage it needs. But if I got a battery with a higher amperage than what is required from the car socket (4.5), say a 12v 5a battery, the boombox should(?) only pull what amperage it needs correct? (without blowing the fuse or anything)

I'm slightly new at electronics, I've done a bit of the odd soldering job with RC cars but nothing a newbie couldn't do
Thanks for all the input so far.

Cheers
Quil

What amperage is available from 8 D batteries?

What is the Voltage drop at a given rate of discharge?

What is the voltage required to allow this box? to operate, Minimum to maximum?

How much amperage is needed to operate this box for a given volume of sound?

What is the voltage drop at a given amperage rate need to operate this box fo a given volume?

This is beyond my mathmatical skills.

Get the battery and measure how long it will play Loudly and for how long, then you will know

I wrote to Sharp UK for a lead, and they finally sent me a diagram showing how to build your own.  I have attached it.

It works, bought the plug on ebay for under £2, soldered the wires on to plug, attached battery clips, works fine

you can have as many amps as you like so long as its more than the required amount stated on the unit, in this case 4.5ah, i think? 

nimh are lighter and better suited than lead acid. you can buy 12v packs, 

this site is pretty darn cool

http://www.batteryspace.com/12...imhbatterypacks.aspx

lithium ion and lithium polymer (li-ion and li-po) are lighter again and more energy dense again, been a few years since i read into the subject but when i last looked li-po had the potential to catch fire. i actually bought one off ebay, looked at it, got freaked out and ended up chucking it in the bin. lol.

your laptop uses li-ion. the new sony tablet z uses li-po i think, so maybe its getting safer.

as i say that was a few years back. fascinating subject actually, batteries.

one of those Nihm packs in the link above is your best bet i would say. the more Ah the longer runtime you will get out of them.

your stereo will pull 4.5 amps continuously if you jack up the volume. so the battery needs to be able to supply that, as in, it needs beefy wires for the current to flow through.

notice the following text in the link below

• Standard rate: 5 Amp ( Recommended and warranted)
• Highest rate for continuous running:  10 Amp   

http://www.batteryspace.com/ni...ceswalkingrobot.aspx

if i were you i would look for a 9 or 10 ah pack. a 9ah pack will supply your stereo with juice for 2 hours at full volume. at least thats the way i understand it. so a 20ah batter = 4 hours +, and still not that heavy if its nimh. li-ion and li-po would be lighter again at those specs.

1 more thing. the unit can deal with avoltage or two, this way or that way. probably it could handle up to 14.4 volts and down to 10 volts.

nice radio, i want!!!

NED, great info and good to see you here and posting again