Stereo & Electronics - Battery Backup
It annoys me that in this day in age of cheap nonvolatile memory, a car radio still loses all settings if power is disconnected.
The storage unit where I store my Formula doesn't have a power outlet available so I can't use a battery tender. So I unplug the battery to make it live longer (the last time I let the car sit for a few months with the battery connected, I ended up having to buy a new battery).
Therefore, I'm looking into alternatives just to power the memory in the radio.
I did some quick searching and found this:
Seeing that diagram setup for 7.2V NiCad, I was thinking that maybe I would use a higher capacity R/C battery than the smaller battery in the diagram. However, even with a larger capacity R/C battery, I'm not confident it will last a month or more. Anyone know? The intended benefit of this would be that if the main battery is disconnected for work being done on the car, the radio still would maintain it's settings, but I'd like a longer run-time so-to-speak to maintain the radio's settings.
Has anyone run into this situation and have any suggestions?
What about running separate wires for the radio's memory directly to the main battery but still disconnect the main cables? It doesn't matter if it gets too low to start the car because I can still jump it.
Any suggestions / alternatives / etc?
08-02-2012, 08:11 AM
Personal Computers deal with keeping the clock alive on a button cell. I'm a bit skeptical that a larger battery is really needed for radios with built-in amplifiers. If the power is tapped in at the correct place, it shouldn't matter.
Are you looking to have a plug-in, plug-out solution or have something in the dash that will recharge when the car is on?
I think the diagram I found stays plugged in all the time, but I'm open to other options.
I forgot to mention in the first post (but many people know), the radio in question is not the stock radio. It is a Pioneer AVIC-D3. Its annoying to have to reset the colors, clock, and backgrounds. Its like they picked-and-chose which settings to keep in nonvolatile memory and which to skip. For example, my EQ preference was retained.
So I guess no one else has thought of this? I was hoping Whitebird00 would chime in.
08-07-2012, 04:53 PM
I've never really thought about it. I've used 9V batteries when needed for short term disconnect while working on the car but never anything that would last for a long time.
Some sort of 12V battery setup would be best because you don't have to do fancy wiring to keep it from exploding if exposed to the electrical system. Still, a switch or relay would be necessary so that you don't defeat the purpose by back-feeding the system with your HU backup connection.
I don't know how long one of those 12V barrel batteries used in garage door openers would last. They're pretty small - look like a half size AA battery - but they last quite a while in a door opener... often a year or more of intermittent use.
There's a couple of possibilities on autotoys.com. Do a search there for "battery backup" and you'll get some listings that are designed for auto alarms and security systems.
There's a 12V 7-amp battery for $43 there that might last a while. The trick would be to have the battery in the main electrical system for recharging but isolated to just the radio when in storage. You could use a standard Bosch style relay to accomplish this. Put your backup battery someplace convenient. Connect the negative to a good chassis ground or even to the negative of the car's battery. Connect the positive to the HU constant wire (disconnecting the HU from the factory constant supply). Connect both terminals 30 and 86 to power from the car's battery. Connect 85 to ground. Connect 87 to the positive terminal of the backup battery (along with the wire going to the HU). When the car's battery is connected, its power will keep the relay energized, keeping the backup battery in the electrical system for charging. When the car's battery is disconnected, the relay trips off, disconnecting the backup battery from the electrical system but leaving it powering the HU memory. The advantage is that there is not even a momentary interruption of power to the HU so there is no risk of losing settings during the switchover.
The big question is how long would a 12V 7AH battery last with just the HU drawing power?
Hope I made some sense... I was kind of thinking it through as I typed.
That does make sense and I did a quick search on Google for battery backups before I started this thread and found some alarm options like you mentioned.
I don't think the small 12V remote battery will last all that long in this scenario and I don't know if there are any rechargeable ones that can be wired in this way.
I've seen some 12V 7AH Sealed Lead Acid batteries for $23 (sometime even less). I bought a couple for my PC UPS a while back. Maybe I could get another one of those and use that for the car.
$5 --- Small Tool Box (to contain battery)
$23 -- 12V 7AH Battery
$5 --- Relay
$? --- Wire
My concern with these 12V 7AH SLA is that they aren't rated for automotive use. Would it be safe to have them on the same charging circuit as the main battery? Would it be safe to drive with it installed? Where could I tap for the charging circuit? Would I have to wire back to the alternator or could I use a junction at the driver-side fuse box?
08-07-2012, 06:30 PM
Random thought - Have you considered either using a deep cycle or marine battery in the car or hooking one up when you disconnect your normal battery?
I'd think that with some accessory battery posts and some jumper cables, you could keep the battery cables connected to power 100% when moving the cables between batteries.
08-07-2012, 06:52 PM
Maybe look into the kits for guys with shaved door handles, they are pretty paranoid about dead batteries. Like WB said, the trick is isolating the circuit for just the stereo HU. ...but if they isolate it down to just power locks, you should be able to put it inline with the fuses for the audio system.
I hadn't thought about setups with shaved door handles. Any ideas where to look?
08-08-2012, 08:22 AM
My concern with these 12V 7AH SLA is that they aren't rated for automotive use. Would it be safe to have them on the same charging circuit as the main battery? Would it be safe to drive with it installed? Where could I tap for the charging circuit? Would I have to wire back to the alternator or could I use a junction at the driver-side fuse box?The SLA batteries are sealed lead-acid just like an automotive battery so the charging circuit shouldn't be a problem but I suppose they may be less tolerant of vibration than an automotive battery. I was looking for a solution that didn't take up much room but certainly a full size deep cycle battery would do the trick. A somewhat smaller alternative would be a motorcycle/lawn tractor battery. They would be compatible with use in a vehicle and you could connect to the electrical system at any point that has full charging voltage (i.e. close to the factory battery would be ideal).
08-08-2012, 12:12 PM
I hadn't thought about setups with shaved door handles. Any ideas where to look?
A shaved handle setup:
Painless Performance has something called their "Digital Power Manager". It's makes dual-battery setups idiot proof with no manual switches. Basically, it only lets the batteries operate in parallel when the starter load is pulling, or the alternator is charging. A slow draw, like headlights left on, will keep the aux battery isolated until you try to turn the starter. They also make a 3 position manual switch dual battery kit (isolated, parallel with ignition on, parallel always) with a control solenoid. I'd put up some links, but painless's website doesn't seem to be up right now. Anyways, you could run a lead from the aux battery directly to the HU's constant power wire, and your HU would be only load on the aux battery when the main one was disconnected.
I've been meaning buy and set up the digital kit on my truck for a while, just never got around to it, just for a fun project, some insurance, and it already has a 2nd battery tray just sitting there.
Stinger makes a nice little aux battery enclosure.
And smaller batteries approaching "lawnmower" size to supplement big audio systems. I have thought about adding something like this to my WS6, in the back connected off my 0-gauge power cable by the amp rack, but installing a KG3 truck alternator pretty much fixed all my low power problems.
I've had to re-apply all the settings on my HU so many times, I have them memorized and can do it fairly fast.
I knew the smaller SLA batteries are basically the same as the car's SLA. I was more concerned with the smaller SLA's durability and whether having an another smaller SLA on the charging circuit was OK. Sounds like it will be fine.
Regarding dual battery & shaved lock kits, looks like I have some reading to do. Thanks for the lead.
I'm trying to keep cost and size down. I'm not averse to building something myself.
I was trying to avoid replacing the main battery with a more expensive deep cycle battery. My concern is that it may go dead the same amount of time anyway and get killed off in the process which makes the whole scenario that much more expensive.