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Adding A Second Battery For Audio System


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#1 minitman

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Posted 24 November 2019 - 02:41 PM

Hello all,

'The Min' has been put into a well earned retirement, for services rendered, and will now only be taken out of the vault for brisk weekend and fair weather runs. It deserves it.

It has been rebuilt right up from bare shell, and I am nearing completion. I have added a lovely 'stereo' system ( for us oldies :proud: ) and I am concerned that it will drain the battery whilst 'the Min' is garaged and resting between rain storms.

 

Question: I have an FIA rated battery cut off switch to isolate the car when garaged. I wish to add a small second battery (12 Volt x 6 Ampere Hour? Yuasa? motorcycle?), to keep the settings of the 'stereo' when the battery is isolated. It will be fed through a relay to avoid cross feeding and back leakage, when the main is isolated, but I am concerned that it will not have a regulated charging circuit to feed it.

SO: Can I simply connect it to the feed to the radio (13.7 Volts when car running) or do I need to add a regulator etc to stop it going bang due to overcharging etc?

Or is there an after market system you can tell me about?

Thanks in advance for any replies, you have always been a great source of information.



#2 Icey

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Posted 24 November 2019 - 03:06 PM

I think you might be over engineering this. What settings are so precious that you want to rig up all this extra gear to maintain?

 

If you really must keep the stereo powered up I'd just leave the main battery connected and buy an Optimate.


Edited by Icey, 24 November 2019 - 03:06 PM.


#3 minitman

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Posted 24 November 2019 - 03:44 PM

Hi Icey. every time I disconnect the battery, I lose all of the saved settings, and I have to scroll through re-setting them.

This includes everything from continent settings, to balance and bass levels. all stations and favorites. The Min is kept in a secure container with no power, and it can be weeks before I get to drive it again, hence the battery isolator.

Thank you for your thoughts though.



#4 gazza82

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Posted 24 November 2019 - 03:52 PM

isn't there an isolator with a small fused link that powers the stereo? If you try to start it, it blows the fuse ...

#5 Pete649

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Posted 24 November 2019 - 05:58 PM

The title of this post takes me back a few years. I remember when an additional battery (or batteries) was fitted to power the stereo system amplifiers.

 

Is it just the head unit you need to maintain power to?


Edited by Pete649, 24 November 2019 - 06:07 PM.


#6 Cooperman

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Posted 24 November 2019 - 08:22 PM

Why not run a lead from the input side of the master switch to a 3amp fuse and then to the stereo/audio unit.



#7 GraemeC

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Posted 24 November 2019 - 09:39 PM

You could run two batteries and then use a split charge relay (normally used on the 12S wiring for a caravan socket)

#8 Tremelune

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Posted 04 December 2019 - 03:26 AM

Check the real draw with a multimeter and do the math. If the stereo is wired correctly, it should draw less than 50mA, which would be less than 10Ah per week...Maybe it just won't be a problem.

 

If I couldn't plug this thing in, I would just buy a biggass deep-cycle marine battery and connect it to the battery of the car with jumper cables when it sits. Every once in a while...take it home and charge it. If you really never get to the car at all for a few weeks, maybe get two so you don't have to make a "charging" trip.

 

It seems like a small battery wouldn't buy you much more time...It doesn't really help you if the stereo loses the settings every time you get to drive the car.

 

My final suggestion is to replace the head unit with one that stores settings in solid state memory. I expect it would be cheaper than a battery of sufficient size.


Edited by Tremelune, 04 December 2019 - 03:26 AM.


#9 BaronVonchesto

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Posted 04 December 2019 - 06:05 AM

 

 

My final suggestion is to replace the head unit with one that stores settings in solid state memory. I expect it would be cheaper than a battery of sufficient size.

^ this.

I had done this on my mini for a while. Got a small  sealed 12 AH deep cycle battery and wired it in parallel to the main battery beyond the isolator. No need to bother with complicated charge circuitry. Since the main battery will pull the majority of the charge current. 

 

In the long run i think its not worth the extra effort. A HU that stores settings in non volatile memory is preferable. No need to fiddle about with figuring out a mounting for a 2nd battery and wiring with fuses neatly.



#10 Dusky

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Posted 04 December 2019 - 11:42 AM

Just add an inline blade fuse holder between the 2 posts of your battery cutoff switch, use the smallest blade fuse you can find. No need to complicate things.

#11 GraemeC

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Posted 04 December 2019 - 07:35 PM

Just add an inline blade fuse holder between the 2 posts of your battery cutoff switch, use the smallest blade fuse you can find. No need to complicate things.


How will that stop the stereo flattening the battery?

#12 Dusky

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Posted 04 December 2019 - 08:50 PM

Just add an inline blade fuse holder between the 2 posts of your battery cutoff switch, use the smallest blade fuse you can find. No need to complicate things.

How will that stop the stereo flattening the battery?

That isnt really a concern. A stereo draws about 0.01 amp/h for its memory.

#13 GraemeC

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Posted 04 December 2019 - 09:47 PM

Maybe not a concern, but it was the question.

#14 Rorf

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Posted Yesterday, 07:58 AM

Stick a solar panel on top of the container :D



#15 gazza82

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Posted Yesterday, 01:35 PM

https://www.amazon.c...omotive&sr=1-29






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