TheSamba.com :: View topic - Power to a new stereo in glove box. How to avoid any battery

Tue Apr 08, 2014 1:38 pm

Drain when off and or running.

1966 beetle converted to a 12v. Stereo has two power feeds one battery and one labeled ignition.

Any tips on how to best wire safely and to avoid battery drain?

Thanks.

Tue Apr 08, 2014 2:15 pm

Battery wire = radio memory circuit. (usually Yellow)
Ignition Wire = radio power supply circuit. (usually Red)
Ground = Ground (usually Black)

Connect power at the fuse box.
Far driver fuse is Ignition on (Key On)
Far passenger fuse is Battery (constant power)

Use the lower or forward terminals as these are the protected side.

As for battery drain while off...

Disconnect battery or add a battery cut out swicth..
You will loose all memory stored though..

Battery Tender/maintainer.

VOLKSWAGNUT wrote:
A battery tender does more than just keep your radio presets.. It also keeps the battery charged and fresh.
Worth the investment IMO.

Harbor Freight sells an elcheapo "Float Charger" for around 10 bucks.
Really cant get more simple than that.

It can be attached to the Voltage Regulator MAIN or the MAIN BATT at the ignition switch or fuse pane under the front hood as well. No need to access the battery directly.
(and ground)..

http://www.harborfreight.com/catalogsearch/result?q=float+charger

If you want to use a stand alone battery, such as a dry cells just to keep presets alive, it would require radio isolation from the cars electrical during non use.
More cost in batteries and waste than worth IMO and will drain those to non use.

Solar maintainer is a good option.. if the car is kept out doors.

Using an old cell phone charger or other transformer based supply is another route. It would require radio isolation as well, at least the memory supply. Just need to closely match a transformer output to desired input.

I keep every small transformer that I can find , as I never know what I may need one for.

.

Tue Apr 08, 2014 2:28 pm

The voltage draw on the radio would be so little, myself I wouldn't be concerned. If it sat for 6 months it may drain the battery.

Tue Apr 08, 2014 3:15 pm

Battery was dead a weak after I installed my Retrosound radio (just from the memory feature); never had a problem before. Bought a nice Black & Decker battery tender online from Wal-Mart and have not had a problem since.

Wed Apr 09, 2014 6:20 am

Does that radio have an automatic antenna feature?

Wed Apr 09, 2014 6:27 am

My Retro Sound in A Beetle kills a fresh battery in about 3 weeks.
My Kenwood in a Buggy kills the battery in a month..

It all depends on the radio parasitic drain and the battery reserve capacity. Not all are created equal.

Wed Apr 09, 2014 5:20 pm

Really? we have one in her 61 and never had an issue -even when sitting for a couple months over the winter.....That doesnt sound right.....

Wed Apr 09, 2014 5:24 pm

If the ignition line is always hot, battery drain in a week wouldn't be uncommon.

Wed Apr 09, 2014 6:50 pm

If that brand of stereo has that high of a drain, then it's defective or engineered wrong.

That yellow wire only needs to energize to remember the time and the saved stations/pre-sets. I have a truck up north with an aftermarket CD stereo that easily can hold a charge for 2 months (haven't tried longer).

Wed Apr 09, 2014 8:21 pm

I hate molesting my wiring to add stuff (gauges, fuel pump, and radio) to my bug so I added a separate fuse block to handle it. I used a heavy duty relay mounted under the seat next to the battery. When my ignition is hot, the coil wire trips the relay and it powers my fuse block. I fished the power wire though the channel along the roof where the factory harness goes, I think I used #10 wire, and the relay is a 40 amp unit. My gauges have a fuse, the radio, and the fuel pump (when I decide to go electric). The "constant" hot for the radio is just supposed to let it store the settings and stations, it should draw very little. I have mine tapped into the OE fuse panel, it's the only non original connection. Doing it this way lets me troubleshoot without having to weed through the aftermarket stuff, I could also return it to stock with little trouble. The relay, relay plug, and fuse block were cheap on amazon.

Oh, the mentioned retrosound radios have a poor reputation, concerning quality. You have the right idea, leave the stock radio in the dash and put the real tunes in the glove box..

Wed Apr 09, 2014 8:24 pm

Very weird. A dirty battery will cause drains as well.

Thu Apr 10, 2014 5:46 am

Boom wrote: Very weird. A dirty battery will cause drains as well.

Yes sir... a slight film of acid/moisture on the top cover or case of a battery will drain a one in a short period.
The battery current creeps across .....

Basic parasitic drain guidlines for single battery systems.

VOLKSWAGNUT wrote:
Average new car suggests 30mA or less is acceptable.
Your old tin beater.. with no frills... and no memory devices.. It should be very low.. less than 5mA or most likely 0.

Here are some guidlines...
Drain -- Days
25 mA -- 30.5
50 mA -- 16.5
75 mA -- 11
100 mA -- 8.25
250 mA -- 3.3
500 mA -- 1.65
750 mA -- 1
1 A -- 0.8
2 A -- 0.4

Of course... your battery reserve capacity has alot to do with how much drain it can sustain for how long.
Note the battery reserve capacity, amp hour rating
Divide the reserve capacity by 4, or amp hour rating by 2.4.
Compare this to the multimeter milliampere reading during testing.
The parasitic current drain should not exceed this number. Example: If a battery has a reserve capacity of 100 minutes, (60 A/H) the current drain should not exceed 25 mA.

Thu Apr 10, 2014 7:32 am

Get a small rechargeable 12v SLA battery to use just for the stereo memory.

Just charge it from time to time.

That way you won't be left with a non starting vehicle, just for the sake of stereo memory...