Car Radio Backup Battery

[Alan Reynolds]

The older radios have a separate 12volt lead to keep a permanent live 12volt to the memory. If you pull the radio out and locate the permanent 12v live, you can disconnect it from the car battery and link in a small 12v lead acid battery to it.
From memory it’s usually the yellow wire on the harness plug that is the permanent feed.
A small lead acid battery will last for ages and you can remove it and recharge it when the car battery is connected.
You could fit a single pole double throw switch so that you can switch the battery in and out for when you use the car.
That’s what I did on an old Simca that didn’t get used much.
If you want the part number of a small 12v lead acid battery, post up.
These on Ebay are small enough to tuck away. Item number 275574066702

 

[bricol]

I just press auto-seek/tune when I get back in after re-connecting the battery . . . find the station, press and hold the relevant button to store it.

And the cost of a couple of decent battery charger/conditioners for my fleet has more than saved the cost of new batteries.

 

[Mick Annick]

The car is a 24 year old Rover (not many left on the road) and the JVC radio is about 10 years old. Of course the original radio was of the ye olde worlde electro-mechanical types which didn't have memories.

It goes back to the days when removable radios were easy to steal, having no battery meant they were useless to the thieving so and so’s that pinched them without the code.

 

[Ross365]

I was tempted to suggest you get one of those.

Jack

Jack, I do still have the original radio! The JVC one was a gift; it has DAB, which I could live without, but it also has a USB socket and that's what I use mainly, playing MP3 from a stick and that does work without re-setting the memory.

@Migmac yes, i think button cells would probably do it, but my recollection is that there is one connector on the back of that radio, perhaps 10 or 12 pins in to a harness, and I'll need to cut in to that and do some splicing on the +12V line. It's really the sort of job I'd refer to do on a warm sunny day, which certainly is not now, but I'll dig out the installation guide and see if I can find the insertion tools.

 

[Alan Reynolds]

Jack, I do still have the original radio! The JVC one was a gift; it has DAB, which I could live without, but it also has a USB socket and that's what I use mainly, playing MP3 from a stick and that does work without re-setting the memory.

@Migmac yes, i think button cells would probably do it, but my recollection is that there is one connector on the back of that radio, perhaps 10 or 12 pins in to a harness, and I'll need to cut in to that and do some splicing on the +12V line. It's really the sort of job I'd refer to do on a warm sunny day, which certainly is not now, but I'll dig out the installation guide and see if I can find the insertion tools.

If it’s an after market stereo, you may find the permanent live is on a bullet connector, so you won’t need to cut any wires.

 

[Ross365]

I found the installation guide. It uses an 16 pin ISO connector and B+ is on that. However, there is then a short (150mm) adapter section of cable which mates up with the original connectors use by Rover. As shown in the diagram, that adapter section is not wrapped; the individual wires are loose so splicing should be easy.

 

[Morrisman]

We dont use the Radio in our car as we got fed up with people talking crap when we just wanted to hear some decent Music. Then when you got some music its either Rap Crap or females seeing how loud they could scream or music that made you wanna slit your neck, There used to be a decent radio station in Stratford on Avon but they changed ownership about 4 years ago and went on to talk crap and play stupid Music. So I phoned the Station up and asked them in a reasonable manner ! Why they can not play anything decent ? There reply was how old are you I said in my 60s , Well we dont cater for your age group only up to 35 to 40 !!!!!!!!!!! I explained my feelings to the manager and left.

That's why I use Alexa at home, I can't stand the drivel that comes out of the radio, on any channel. I just tell it to play whatever genre of music I fancy. Surprisingly I've been listening to classical music lately. Never thought I'd see that day.

I keep meaning to get one for my workshop too.

In the car it's usually radio one or Signal, just flip back and forth to avoid adverts and idiots waffling.

 

[Alan Reynolds]

We dont use the Radio in our car as we got fed up with people talking crap when we just wanted to hear some decent Music. Then when you got some music its either Rap Crap or females seeing how loud they could scream or music that made you wanna slit your neck, There used to be a decent radio station in Stratford on Avon but they changed ownership about 4 years ago and went on to talk crap and play stupid Music. So I phoned the Station up and asked them in a reasonable manner ! Why they can not play anything decent ? There reply was how old are you I said in my 60s , Well we dont cater for your age group only up to 35 to 40 !!!!!!!!!!! I explained my feelings to the manager and left.

Glad I’m not alone. I had a customer who made music and he brought his Apple in to be repaired for a fault on the audio side. We placed some of his music to test the output after repair. We both felt like killing someone after listening to his music. Little wonder young people suffer with depression and feel the need to be violent when they have to listen to this carp.

 

[minimutly]

My main reason for not wanting to use a trickle charger is just not wanting cables around the place. I'm also a bit grumpy at the moment, I bought a "smart charger" on ebay a while ago, charged to 14.8 then goes on trickle and that was fine for 3 months...then it failed and cooked a battery. A decent quality charger that you can trust and leave like the CTEK (?) are a tad more expensive.

Like I say, the button batteries used to maintain the CMOS memory in PC's last for years, so the current must be minute, but almost certainly I'll have to take the radio out to set it up, which is do-able, but could be fiddly. The fusebox that feeds the radio is in the drivers footwell so you're on your hands and knees to get at it.

That rotary switch with clock feed is something I've never seen before; perhaps that's the answer to the problem so thanks for that idea, which I'll look in to.

I think it's plain daft making a radio (JVC, normally good?) in which every setting is in the memory which is lost the instant the battery is disconnected. Is that a common thing or not ?

You need one of those old Radiomobile ones with the mechanical set buttons.....

You could try a small supply plugged into the cigaret lighter, but you’d need to pull its supply fuse or you will be supplying the whole car, back to square one.
As for getting into the guts of the radio and”splicing in” a remote battery - good luck...

 

[Ross365]

You need one of those old Radiomobile ones with the mechanical set buttons.....

You could try a small supply plugged into the cigaret lighter, but you’d need to pull its supply fuse or you will be supplying the whole car, back to square one.
As for getting into the guts of the radio and”splicing in” a remote battery - good luck...

Started the Holiday celebrations early have you

 

[James1979]

My main reason for not wanting to use a trickle charger is just not wanting cables around the place. I'm also a bit grumpy at the moment, I bought a "smart charger" on ebay a while ago, charged to 14.8 then goes on trickle and that was fine for 3 months...then it failed and cooked a battery. A decent quality charger that you can trust and leave like the CTEK (?) are a tad more expensive.

Like I say, the button batteries used to maintain the CMOS memory in PC's last for years, so the current must be minute, but almost certainly I'll have to take the radio out to set it up, which is do-able, but could be fiddly. The fusebox that feeds the radio is in the drivers footwell so you're on your hands and knees to get at it.

That rotary switch with clock feed is something I've never seen before; perhaps that's the answer to the problem so thanks for that idea, which I'll look in to.

I think it's plain daft making a radio (JVC, normally good?) in which every setting is in the memory which is lost the instant the battery is disconnected. Is that a common thing or not ?

Couldn’t you take a feed off the input to the existing cutout, via and inline fuse holder with a 1a fuse, to the positive of the radio?

I’m assuming that’s all the clock one is?

I’ve done it in the past with a fuse holder over the terminals of the cutout to protect memories etc, but it’ll blow if you put the ignition on. That was for security rather than a drain though.

I can’t see how either of my ideas or the clock switch thing would prevent a parasitic drain?

 

[Ross365]

Couldn’t you take a feed off the input to the existing cutout, via and inline fuse holder with a 1a fuse, to the positive of the radio?

I’m assuming that’s all the clock one is?I’ve done it in the past with a fuse holder over the terminals of the cutout to protect memories etc, but it’ll blow if you put the ignition on. That was for security rather than a drain though. I can’t see how either of my ideas or the clock switch thing would prevent a parasitic drain?

Yes, after further thought, the clock switch thing won't do what I need. The lesser of the many evils appears to be to remove the radio and cut in to the adapter cable described in post post#26. Install a small box containing 2 PP3 batteries, two diodes to manage current flow and a zener shunt circuit to limit the voltage to 12V.

This only has to work 4 months a year and given the long life a quality PP3 will give in something like a fire alarm, I reckon I could get two or more winters out of them. As the JVC radio is only 10 years old, people seem surprised that the memory is volatile. It is actually a good radio and the cost of buying a comparable replacement not too attractive.

 

[James1979]

Like you, I cannot fathom why in this day and age they do not have a battery backup built in?

It would cost pence to do the same as a PC with a button battery on the board?

I bet the memory that stores the presents isn’t 12v anyway. It’ll be stepped down somewhere

 

[Jack Ryan]

Like you, I cannot fathom why in this day and age they do not have a battery backup built in?

It would cost pence to do the same as a PC with a button battery on the board?

I bet the memory that stores the presents isn’t 12v anyway. It’ll be stepped down somewhere

You'd think someone would invent a small (say) I2C EEPROM and get rid of the battery altogether.

Jack

 

[Ross365]

I've been told that non-volatile memory in car radios is now standard. This one is about 10 years old; I didn't think memory had progressed so much in that time that this JVC didn't have it?

 

[mtt.tr]

Can't you just put a solar panel in the windscreen

 

[Jack Ryan]

Can't you just put a solar panel in the windscreen

I believe that would require taking the roof off the shed.

 

[mtt.tr]

I believe that would require taking the roof off the shed.

Put it on the shed roof then

 

[ajlelectronics]

I've been told that non-volatile memory in car radios is now standard.

Then you have been told wrong. All aftermarket single DIN kit that I have tested are the same volatile design.

 

[GRW]

I lost 12v supply on the old 12-plate works knock-around Transit a few weeks back. Bad +-ive terminal connection.
After refitting the radio required the acess code, and once code was inputted the radio went straight onto the station it was on before supply loss - so I can only take from that, that some radio's must have a non-volatile memory.

For the OP how about just splicing a parallel 12v feed to the radio as discussed, and tucking a small sealed 12v rechargeable Fire Alarm type battery in the glove box or similar?
Then when you reconnect the main battery, you can just switch out or unplug the rechargeable Fire Alarm unit?