Car Radio Backup Battery

[Ross365]

One of my cars doesn't get much use esp in winter; the battery was often low due the current taken by the security/locking system. I've got round this by installing one of the battery disconnect devices. This is good; the battery is always near full charge and the car starts first time (and the battery should last longer), but bad because the radio loses all the stations settings .

I think I'm right that the radio memory needs only the tiniest current (<1mA) to keep it alive (like the CMOS battery in a PC?) so I'm wondering how to put a battery in there that just supplies that memory.

I notice that the radio shares it fuse with the cigar lighter and nothing else. I wonder if I could sort out something connecting a small battery (2x PP3 with a 12V zener?) in to the socket? That would probably allow leakage back through the rest of the electrics. Probably needs a direct connection the radio and a diode isolator. B*gger!

Any ideas appreciated.

 

[brightspark]

just buy a trickle charger and leave it plugged in

 

[Ross365]

No.

 

[Barking Mat]

just buy a trickle charger and leave it plugged in

That's what I'd do, or 24 hours every fortnight.

All my dozen odd work boats, are all sat on charge over winter, when not used.

No better way to kill a battery then flattening it.

Don't over complicate the issue.

 

[Mick Annick]

That's what I'd do, or 24 hours every fortnight.

All my dozen odd work boats, are all sat on charge over winter, when not used.

No better way to kill a battery then flattening it.

Don't over complicate the issue.

Maybe Ross hasn’t got anywhere to plug one in? I didn’t at my last house - garage was in a block in a nearby street, no power, under trees so no light for a solar panel.

 

[Barking Mat]

Maybe Ross hasn’t got anywhere to plug one in? I didn’t at my last house - garage was in a block in a nearby street, no power, under trees so no light for a solar panel.

Yes, there is that.

Extension cables ?

 

[Mick Annick]

Yes, there is that.

Extension cables ?

Mine would have needed to be about 400 metres long and cross two busy roads…

 

[Barking Mat]

If the OP, cares to elaborate.

 

[ajlelectronics]

Yes you could use an external backup battery. I am not sure what standby current is but I can measure it tomorrow evening.

 

[Robotstar5]

If it shares a fuse with the cigar lighter, remove the fuse so you don't backfeed anything else then knock up a lead to plug into it and connect your battery, you may get away with just one 9V battery.

 

[Beanwood]

How about something like a disconnect switch but with a permanent live feed on a low current fuse you could take straight to the radio like this https://www.carbuilder.com/uk/rotary-battery-cut-off-switch-with-clock-feed

 

[Ross365]

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 ?

 

[Jack Ryan]

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.

Things have probably improved over the years but car makers have never seems to care about conservation - everything uses 10s of amps. One would hope that the radio backup would be mA but best check or the backup might not last as long as leaving the car battery connected.

How modern is the car? Disconnecting the battery sometimes requires the EMS to retrain.

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 ?

Yes, that is common - disconnect the battery and you need the PIN for the radio and then you need to reprogram the memories. Car radios don't need backup batteries - they use the car battery!

Mechanics and auto electricians often use "power bank" starting batteries to keep the radio and EMS powered while changing the battery. Won't help you though as it will go flat faster than the car battery.

Jack

 

[Ross365]

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.

 

[Jack Ryan]

Of course the original radio was of the ye olde worlde electro-mechanical types which didn't have memories.

I was tempted to suggest you get one of those.

Jack

 

[maroon]

Scooter battery (they used to be about a tenner probably about 20 now, I have a few dotted around). Set of test leads. (small jumper cables)

Take off and charge one or the other.

 

[fixedfixer]

Scooter battery (they used to be about a tenner probably about 20 now, I have a few dotted around). Set of test leads. (small jumper cables)

Take off and charge one or the other.

I use one of the 12v 3amp ones to power the fish finder on my kayak. Can run the unit for four days before it requires charging. Imagine it would keep the radio settings for weeks if not months.

 

[Hog-Rider]

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.

 

[addjunkie]

Just run the car more regularly, moving wheels, tyres and brakes is a good thing. I use optimates on my bike and generator.

 

[Migmac]

Not a problem I have ever thought about, I don’t play the radio in cars anymore.
You can get button cell holders on eBay. Could you put a cigarette lighter plug on to it and feed power back to the radio from the cigarette lighter socket?