Car Radio Backup Battery

[ajlelectronics]

I will need to test if the OP is interested, what the permanent line is used for. With my experience of the radio conversion kits that I make and sell, the 12V permanent line does EVERYTHING, power wise. The 12V IGN is merely a sense line for switching the permanent supply in.

 

[Ross365]

What I am thinking about doing is shown in the attached figure. Installing a small plastic box with 2 PP3 batteries, 2 diodes and a resistor on a small piece of Veroboard. I need to confirm there is space to squeeze it in.

The battery isolator is only used 3-4 months of the year. Considering how long a PP3 will run a smoke detector, I hope I could get at least 2 winters out of it. Nobody at all seems to have any idea of how much current in needs to retain the memory, but I guess <50uA. I think that R will be at least 100k or more.

 

[knighty]

just wire the radio to the other side of your disconnect switch

maybe get a little solar panel to stick in the window?

 

[m_c]

You may want to measure the current first, as I would guess the radio quiescent current is more likely to be measured in milliamps, rather than microamps, as given normal usage, the radio standby circuit isn't likely to be that optimised.

 

[Ross365]

just wire the radio to the other side of your disconnect switch

maybe get a little solar panel to stick in the window?

A direct wire would need to find its way through the bulkhead, which is probably do able, but it's low down, in terms of radio location and access is not great. I suspect that in terms of time taken, there would not be much in it.

I've had solar panels and waved goodbye to them with 2 fingers.

It's not the quiescent current of the radio which matters but only of the memory.

Think of it in terms of the small button battery in a PC, which last for a good few years.

 

[m_c]

A direct wire would need to find its way through the bulkhead, which is probably do able, but it's low down, in terms of radio location and access is not great. I suspect that in terms of time taken, there would not be much in it.

I've had solar panels and waved goodbye to them with 2 fingers.

It's not the quiescent current of the radio which matters but only of the memory.

Think of it in terms of the small button battery in a PC, which last for a good few years.

Er, unless you plan on bypassing lots of the built in radio circuitry, it is the complete radio quiescent current that matters.

A button cell in a PC is designed to only power a dedicated IC which will optimised to ensure the absolute minimum of current is needed to maintain BIOS settings and a semi-accurate time. Plus the cell is only used when no power is connected to the PC.
A car radio isn't likely to have that level of current optimisation, as they're normally connected to quite a large battery, where a few milliamps drain isn't a problem under normal circumstances. A lead acid battery is likely to have a higher internal discharge rate than a few milliamps from a radio.

 

[ajlelectronics]

30-50mA is typical for standby current.

 

[Ross365]

I was not aware of that! That's as much power as a modest portable transistor radio takes, typically using PP3/6/9 (in the old days). It must be doing stuff other than keeping the memory alive .

I think it's true that some cars now see a total drain of best part of 200mA on the battery ( I have a Totota that's greedy; it has a slave battery of NiCads for the alarm and they deteriorate over time and make the problem worse) and it's not so much that the battery gets flattened, but you end up with a polarised layer of acid against the plates and the terminal voltage falls.

The car normally lives under a car port, with limited door-opening space; I really need a dry day so I can back it out and look more closely at getting the radio out and seeing what's do able.

 

[Keithmac]

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.

I turned our works radio off for the same reason, 90% of the presenters were just self gratifying bell ends and just wound me up listening to them!.

 

[Keithmac]

Milwaulkee M12 battery, big diode (rated to max power draw of radio,) cut into B+ then M12 supply after that.

The Live After Ignition is just a sense wire, does not carry the brunt of power supply on a reasonably modern radio.

 

[barracuda816]

Milwaulkee M12 battery, big diode (rated to max power draw of radio,) cut into B+ then M12 supply after that.

The Live After Ignition is just a sense wire, does not carry the brunt of power supply on a reasonably modern radio.

I don’t think those battery’s have a low voltage cut off (I belive that’s in the tool) so that would be a good way to quickly kill an expensive battery.

You could get a boost converter and stick a couple of 18560 battery’s in it. But I would just be looking at installing a socket closer to sort the trailing sockets, and a decent battery maintainer. 0.6a cteks are cheap. And come with ring terminal hook ups so you don’t even need to pop the bonnet to connect and disconnect.

 

[Keithmac]

I've run an Optimate for 10 years on my GTO with no issues, you get what you pay for.

 

[ajlelectronics]

My Scorpio lives on a Lidl battery charger. The only issue with that "smart" charger type is that it will not resume charging after a power cut. I have three or four of those chargers and never had a problem, unlike the C-Tek.

 

[Ross365]

Problems with the CTEK - do tell. Everyone I know seems to think they are the dogs do-dahs. I was running a home-made charger for years (that cuts off at 14.8) , then it had a problem and I bought the ebay charger that lasted 3 months. Must repair the homebrew.

 

[GRW]

Problems with the CTEK - do tell. Everyone I know seems to think they are the dogs do-dahs. I was running a home-made charger for years (that cuts off at 14.8) , then it had a problem and I bought the ebay charger that lasted 3 months. Must repair the homebrew.

Deep Sea Electronics do some decent (panel mount / DIN Rail mount design SMPS 5A intelligent battery chargers that are used to maintain starter batteries on Standby Gens and the like.
I've bunged one inside a generic thermoplastic box before to serve as a portable/temp charger.

(They do an expensive 10A programmable one - a 9460 model or similar - that'll that'll do 12/24v, support different battery types/profiles, & that can also be configured to be a PSU).

 

[Ross365]

OK, I'm on the job and failing fairly miserably. I'm inserting the removal tools, but cannot feel any engagement with anything. Not the least sign that I'm releasing it. Any advice please - see pics

 

[Keithmac]

My Scorpio lives on a Lidl battery charger. The only issue with that "smart" charger type is that it will not resume charging after a power cut. I have three or four of those chargers and never had a problem, unlike the C-Tek.

Optimate will resume after a power cut, as long as it sees a battery is connected and there is power to the unit it will maintain the battery. No buttons to push to get it going.

 

[ajlelectronics]

You may not feel any engagement as sometimes it is just pushing the clips OUT of engagement. See if you can jer, jer, jiggle it a bit once the tools are in and so draw it forward. They really aren't a clever idea and give me the same problem often. Some judicious bending of the tools can help make it catch something.

Can you get your hand behind to help it?

Edit, I have just noticed that you have not removed the bezel. You need to be in the slots at the extremities which are under the bezel usually, down the sides of the radio.

 

[ajlelectronics]

Optimate will resume after a power cut, as long as it sees a battery is connected and there is power to the unit it will maintain the battery. No buttons to push to get it going.

Yes, an advantage for sure. However the Lidl chargers are under £15 each when they have them.

 

[Keithmac]

For 10 years use I have no problem paying a what I did for mine, (£60 iirc, £6 a year..).