Question for electrophiles...

[Trace26]

You could just put a small 12v rechargeable battery or capacitor at the radio.
I plan to swap the lead acid with a lithium battery. Either LTO or LFP.

 

[FlyHappy]

There are radios designed to not have a constant 12 volt. See my post from April.

Search for Car Radios with:
1. Car Radio with Non-volatile memory
2. Zero Memory Draw
3. Preserved Settings when powered off

For some reason, marine, RV, and heavy-duty radios often have this feature. Crutchfield does not list this in their features. The Sony DSX-M80 is an example, though the price is too high for me. Some of the $100-$150 Pioneer and Jensen's seem to have it (Maybe??). A person on Reddit said his preserved his stations, audio settings, and bluetooth, but not the clock. These radios are available if you look. Let me know what you find.
HootOwls 🦉

I own a Pioneer Android based head unit, aka "fm stereo", it has non-volitile RAM (or maybe even a little battery onboard, don't know, don't care). It works fine w/o any constant power, just accessory power. It preserves station presets (and BT pretty sure). Frankly, its all I care about, never checked anything else.

I am not that Reddit poster, fwiw.

This is installed in my 2001 Jetta, which some of you may recall as having ended up on a tow truck last week..... despite my deep exasperation, I pushed thru and replaced the alternator, so its back on the road. It is likely the alternator has been weakening over several years (without me realizing), and its one reason why I originally connected this stereo, intentionally, without constant power.

I also have another different Pioneer Android DMH series unit, still in the box. It is earmarked for my MX-5, with its tiny 12v battery, and phantom draw from prior owners *who knows what they did* (LED lights, radar detector, stereo, etc). I fully expect to also be able to install & power satisfactorily without constant power.

Point being - 12v power for accessories has always been easy to botch, ICE or EV. The Slate will be fine, extra batteries, on board generators, diesel heaters... all this craziness i read about... well, it just seems nuts for normal use cases.

 

[Rocks]

If the clock and station memory of a head unit is killing your battery, just how long is that car sitting for?

 

[FloppaEnjoyer8067]

Thanks for the good feedback. It's good to see what does and does not work. I will do more research in to resistors. I like the idea of being able to "disconnect"...will also do some studying on the "pigtailing".

I can build a barn. I can build a cabinet. I have shy 'ed away from understanding electronics. I might be getting old...but I can still learn. ;-)

Thanks again...good info.

Anyone else (I know from other threads that some of you want to do the same...rig a real CD (maybe AM/FM) with good speakers...and not rely on BT?

You can do what boats do and you buy a switch that either connects battery 1, battery 2, or both.

When normally driving (or boating) you have it on 1 and 2 to keep both charged. When you are running accessories, you turn one off. Thay way, one stays charged.

You could also have a relay trigger a second battery on and off based on the ignition on (or whatever it is) signal. Assuming there's a fusebox, this would be easy to pull in

 

[FlyHappy]

If the clock and station memory of a head unit is killing your battery, just how long is that car sitting for?

I assume you are talking to me?

I did not say head unit was killing the battery (also not sure which vehicle you are referring to).

I was just saying that I took possession (of both cars) with clear phantom electrical issues. The MX-5 much more severe.
Without knowing (at that time) that the alternator was probably steadily declining in the Jetta, I chose to use ACC power only when replacing the factory audio, simply to ensure that I would not muddy the diagnostic waters further, and that the stereo works to my complete satisfaction in this way.

Both cars have sat for various periods, and yes, I typically do things like disconnect batteries, use maintainers, etc.

 

[Kopsis]

If the clock and station memory of a head unit is killing your battery, just how long is that car sitting for?

Just because a backing up a small SRAM shouldn't take much power, that doesn't mean that the race-to-the-bottom Chinese electronics will implement it that way. I've seen at least one head unit that kept its UI processor powered 24/7 so they could avoid the boot-up delay when the car was started. Again, there are definitely smarter ways to do this, but vendors assuming they have a 60 Ah battery backing them up don't always resist the temptation to just brute-force it.

 

[Frozen North]

I ran across an older forum post (yes...Tesla) where the writer claimed to have installed a 2nd 12V battery (utilizing a product from West Mountain Radio called a "rig runner") in his frunk...that was able to get the 2nd battery to pony with the 1st to recharge from the main battery charge. They were then able to utilize the 2nd 12v to run excess...while keeping the primary 12v charged for "non-optional" use. Here's the thread:

https://teslamotorsclub.com/tmc/thr...cond-12-volt-battery-to-their-vehicle.234731/

I'd really like to (eventually) install a real cd/am/fm with good "wired" speakers (gah...i'm old...i can do bluetooth but do I want to?)...but? I don't think it's even close to smart to do that with just the 12V that needs to start/run things. I would really love to pop one of my stack of collected CD's in to my future Slate and feel the burn. ;-)

Do any of you that have electronic or car-wiring experience have a thought on this? Is it feasible...is it a pipe-dream? Does the set-up that the Tesla driver found sound like it would work? Will it even be possible to wire something like this up?

Thanks y'all!

Forgive me if this has been said, but I haven't seen it here.
There is a cheap quasi built-in option for FM radio with the Slate truck already. Cheaper Samsung and Motorola phones have a built-in FM receiver chipset and they can be purchased nearly anywhere for $50 or so. Plug a speaker or headphones in and Bob's your uncle. The phone uses the plug wire as an antenna. Sorry, the flagship phones ironically don't usually have this.

 

[KevinRS]

If the clock and station memory of a head unit is killing your battery, just how long is that car sitting for?

In design, Slate can't count on what you add having low draw. An EV 12v battery doesn't need to be a 30 lb lead acid battery. The little 4 lb battery they may use could be drawn down relatively quickly depending on what you installed. Even some factory radios have been found to be the source of a drain that was killing someone's battery, I'm assuming a problem with the radio. Some may want to install an alarm system: that takes constant power. Some might just connect stuff that doesn't need the constant power to constant power and kill it that way. Connect your radio to just the constant power and leave it on?
So Slate appears to be taking the "safe" route and just not providing constant power at the dash.

 

[FlyHappy]

Forgive me if this has been said, but I haven't seen it here.
There is a cheap quasi built-in option for FM radio with the Slate truck already. Cheaper Samsung and Motorola phones have a built-in FM receiver chipset and they can be purchased nearly anywhere for $50 or so. Plug a speaker or headphones in and Bob's your uncle. The phone uses the plug wire as an antenna. Sorry, the flagship phones ironically don't usually have this.

because its a janky solution. Terrible to change stations for starters, and so many more compromises.

 

[AZFox]

You could just put a small 12v rechargeable battery or capacitor at the radio.

How would this be done?

My 1962 VW Beetle was 6 Volt, so I added a second battery (under the other side of the back seat because the battery is under the back seat cushion in one of those) and ran my radio with that. Charged it with a battery charger. Worked great for years.

Could an AGM motorcycle battery run the radio? If so, could it be charged "intelligently" when the vehicle is on? By intelligently I mean when the radio's battery is fully charged the charger ceases to charge and goes into maintenance mode, similar to a Battery Tender.

I suppose a kluge-y way to do it might be
12V Accessory port -> inverter -> battery tender -> battery

 

[Johnologue]

So wait, could you just have a portable power bank with pass-through charging plugged into the Slate's accessory power (thus charging when the Slate is on) and use that to power things that would need constant power? I think someone was saying that, but I can't quite tell. I can imagine it not working well(/at all) with things designed for automotive wiring.

 

[E90400K]

How would this be done?

My 1962 VW Beetle was 6 Volt, so I added a second battery (under the other side of the back seat because the battery is under the back seat cushion in one of those) and ran my radio with that. Charged it with a battery charger. Worked great for years.

Could an AGM motorcycle battery run the radio? If so, could it be charged "intelligently" when the vehicle is on? By intelligently I mean when the radio's battery is fully charged the charger ceases to charge and goes into maintenance mode, similar to a Battery Tender.

I suppose a kluge-y way to do it might be
12V Accessory port -> inverter -> battery tender -> battery

Or a solar battery maintainer. DC-to-DC.

 

[Cubicle23]

Sounds like a Split Charge Relay, possibly with some extra protection to completely isolate it. Only issue might be the vehicles "smart" system noticing that the charge current is larger than expected and having a hissy fit. Unlikely, but possible.

 

[Trace26]

How would this be done?

My 1962 VW Beetle was 6 Volt, so I added a second battery (under the other side of the back seat because the battery is under the back seat cushion in one of those) and ran my radio with that. Charged it with a battery charger. Worked great for years.

Could an AGM motorcycle battery run the radio? If so, could it be charged "intelligently" when the vehicle is on? By intelligently I mean when the radio's battery is fully charged the charger ceases to charge and goes into maintenance mode, similar to a Battery Tender.

I suppose a kluge-y way to do it might be
12V Accessory port -> inverter -> battery tender -> battery

2 ways
1. A dc-dc converter, can be set to only charge by voltage level or from a switched 12v signal. Good for if you want to charge a lithium battery.
https://www.victronenergy.com/dc-dc-converters
This is the one I have, it's a 12to24v for my 24v system (inverter, fridge, ac).

2. Dual battery relay. https://www.vevor.com/battery-isola...-6-mtr-12v-140amp-professional-p_010110666961

 

[KevinRS]

So wait, could you just have a portable power bank with pass-through charging plugged into the Slate's accessory power (thus charging when the Slate is on) and use that to power things that would need constant power? I think someone was saying that, but I can't quite tell. I can imagine it not working well(/at all) with things designed for automotive wiring.

Most portable power banks aren't made for pass through charging.