Starting vehicle with radio on

[mmckenna]

Thank you for telling me that. I didn’t know it would draw when the radio was off.

There's a couple of solutions to this that will make life much easier.

Depending on the age of your car, many newer ones have "retained accessory power" (GM term) where when you shut the ignition off, accessory power will stay on until you open a door or a set time elapses. I've used those circuits for driving relays and timers to shut things down to keep them from draining the battery. On a few vehicles, I found that the unused sun roof circuit was available. On several of our work trucks, I was able to find the taped off wire in the A pillar. Using that to drive the relay/timer worked well. Required adding a fuse to the "sun roof" circuit.

Other option is to get one of these:
https://lindelectronics.com/product-category/shutdown-timers/
Yeah, they are expensive, but you can often find them really cheap on e-Bay. You provide battery power to the input, an ignition (or retained accessory power) to the timer and it'll automatically turn your equipment on/off with the vehicle. The timer lets you have things stay on for a set period of time after you shut down your car.

This is what is often used on professional installs to prevent batteries from getting drained. Well worth it if you are going to be installing radios in your car.

 

[StaticDischarge]

Or if you are handy here is a cheaper possible solution.
Up to 999 minute countdown timer with 10 amp contacts.
Multi Function Time Relay SPDT-MPJA.COM

 

[K5mow]

I believe the MFJ-4416 will do what you need.

The new version is MFJ4416C. It works great. I use it to keep voltage up to 13.8 when transmitting with car not running.

Roger



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[K5mow]

wire direct to battery

This will likely not work for most.




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[krokus]

I try to make a good effort to not start my truck with the radio on but it does happen. It reduces the power just enough to restart my radio when it happens. Is there any type of capacitor that can go inline with the power cord that won’t drop voltage when engine gets started?

A capacitor would not go inline, it would be parallel to the radio. You could try one meant for car stereo subwoofer amplifiers, but not sure it would take care of your problem. (Plus, I read that you have a solution enroute.)

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[RFI-EMI-GUY]

There's a couple of solutions to this that will make life much easier.

Depending on the age of your car, many newer ones have "retained accessory power" (GM term) where when you shut the ignition off, accessory power will stay on until you open a door or a set time elapses. I've used those circuits for driving relays and timers to shut things down to keep them from draining the battery. On a few vehicles, I found that the unused sun roof circuit was available. On several of our work trucks, I was able to find the taped off wire in the A pillar. Using that to drive the relay/timer worked well. Required adding a fuse to the "sun roof" circuit.

Other option is to get one of these:
https://lindelectronics.com/product-category/shutdown-timers/
Yeah, they are expensive, but you can often find them really cheap on e-Bay. You provide battery power to the input, an ignition (or retained accessory power) to the timer and it'll automatically turn your equipment on/off with the vehicle. The timer lets you have things stay on for a set period of time after you shut down your car.

This is what is often used on professional installs to prevent batteries from getting drained. Well worth it if you are going to be installing radios in your car.

My Ford Expedition has such a timed circuit. It makes tracing phantom current drain a hassle because you have to wait 20 minutes or so for the computers to go to sleep. But it also controls lighting and so can run an accessory relay for radios and such.

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[R8000]

I use this relay on my D710 in my Toyota. My D710 get power direct from the battery with this relay inline. The power to the relay coil comes from a ignition controlled cig lighter outlet.

When I press my start button in the car, the car starts then the 10 second countdown starts, then (click) the Kenwood turns on High current amp draw from transmit comes from the battery, low current draw to power the relay comes from ignition switch.

Without, my Kenwood would blip on and off then back on. I didn't want to damage it, and this relay did the trick. Simple,

 

[N4GIX]

I use this in my Toyota Camry:

Essentially what this unit does (optionally) is automatically turn off whatever is controlled by this unit when the battery discharges to a set voltage, thus allowing sufficient power to restart the car. When starter is engaged, it will not supply power to connected devices until the engine starts. The main reason for me using this unit? I bought it new at my local ham club's auction for only $5.00!!!

NB: I see them on eBay for around $30 or thereabouts.

Sure Power SP130512 Low Voltage Switch, 12V, 20A

Low battery switch disconnects predetermined loads from the starting battery bank to ensure sufficient power for starting

• Automatically reconnects loads if vehicle is started or battery is recharged
• Start signal input override to prevent the loads from disconnecting during starting
• Manual override for connecting or disconnecting during emergencies
• Audible or visual alarm output activates 1 minute before disconnect
• 1/4" studs and 1/4" male tab contacts, connect with female quick disconnects

 

[WB9YBM]

I try to make a good effort to not start my truck with the radio on but it does happen. It reduces the power just enough to restart my radio when it happens. Is there any type of capacitor that can go inline with the power cord that won’t drop voltage when engine gets started?

I'm assuming that whoever designs mobile radios has taken that situation into consideration--assuming that's correct, I doubt you need to worry about damage to the radio....

 

[KD2FIQ]

I honestly never thought about damage to the radios. I have noticed all my radios will drop out on car start. Of course there is a voltage drop which would cause the radios to blip off. They come back on right away, I have the positive wired direct to the battery. Negative is to body / sheet metal ground per the RAM factory recommendations. Vehicle is a 2017 RAM 1500. Radios are ICOM IC-7100 and Kenwood TM-V71A.

 

[WB9YBM]

I honestly never thought about damage to the radios. I have noticed all my radios will drop out on car start. Of course there is a voltage drop which would cause the radios to blip off. They come back on right away, I have the positive wired direct to the battery. Negative is to body / sheet metal ground per the RAM factory recommendations. Vehicle is a 2017 RAM 1500. Radios are ICOM IC-7100 and Kenwood TM-V71A.

I've heard that on certain (maybe all?) modern cars with their computer controls have power management systems in place, part of which limit the charge current to the battery (on my car, for example, limits the charge current to 5 amperes). So, if we hook up directly to the battery (instead of someplace else) and it happens to be a radio (like in ham or commercial applications) and the transmit time & current draw might be such that the re-charge of the battery (especially shortly after the huge current draw of the starter) might not be able to keep up, especially on shorter trips. Maybe someone out there like a mechanic might be able to offer additional details & insights...?

 

[mmckenna]

Normal engine starting is not going to damage a radio.
The big name companies have been doing this for a long time and there are hundreds of thousands of radios out there. If a wide spread issue was going to occur, we'd know about it.
I've seen a lot of crappy radio installs in my days, but I've never seen one that damaged the radio (short of some knucklehead hooking it up bassackwards)
The issues with the scanners screwing up when they can't dump to the SD card is just a bad design of the radio.

Some of this is people overthinking the issue. Take a deep breath, step back...

There are well established and documented procedures for -professionally- installing a two way radio in a vehicle. Doing a professional level install will resolve a lot of issues.

Usually what causes the radios to power cycle on starting is voltage drop in the power source. When you start the engine, the starter puts a lot of drain on the battery instantaneously. The "coup de fouet" effect in the battery will cause a short drop in voltage but that will rebound pretty quickly in a good battery. Just the sheer current draw of a starter will cause the voltage to drop anyway. You can spend a lot of money trying to prevent it, or you can just accept it.

I've got about 60 or 70 mobile radios at work that go through this all the time. Everything from sedans to police cruisers up to garbage trucks and buses. No radio failures.

 

[mmckenna]

So, if we hook up directly to the battery (instead of someplace else) and it happens to be a radio (like in ham or commercial applications) and the transmit time & current draw might be such that the re-charge of the battery (especially shortly after the huge current draw of the starter) might not be able to keep up, especially on shorter trips. Maybe someone out there like a mechanic might be able to offer additional details & insights...?

Unless you are transmitting all the time with a high power radio, I doubt it'll be an issue.
I've never heard of a vehicle limiting recharging of the starting battery. Usually the alternator is bussed right in with the battery. The battery takes as much current as it needs until the voltage recovers then the charge current drops off.
A starter pulls a lot of current, but only for a very short time, so overall, it shouldn't discharge the battery that much. Even if recharge current was limited to 5 amps, it wouldn't take long to bring the battery back up.

I think one issue a lot of people are having is cheap batteries or batteries that are in need of replacement.
I've got a 1 ton pickup at work and one at home. Both have two way radios in it.
The truck at work is a gas engine with one battery. The radios will often restart after engine cranking. Not a big deal.
My personal truck is a Diesel and has two batteries. Rarely does that radio restart after charging.

I've had other trucks that did this. Sometimes the restarts wouldn't happen, but as the battery aged it would. Lower temperatures can impact battery performance, too.

More often, improper installation is an issue.
Making sure all battery connections are clean is important. Periodic maintenance should include removing battery cables and cleaning the connections well.
Wire size needs to be appropriate for the radio.
Properly installed connectors are necessary. Cheap crimp on connectors installed with the cheap "smash-n-pray" style crimpers leads to a lot of problems.
Corrosion is an issue, too, especially under the hood.
Poor grounding is a big deal.

I've fixed a lot of radios over the years by just fixing all the poorly done wiring jobs done by "installers".

 

[WB9YBM]

Unless you are transmitting all the time with a high power radio, I doubt it'll be an issue.
I've never heard of a vehicle limiting recharging of the starting battery. Usually the alternator is bussed right in with the battery. The battery takes as much current as it needs until the voltage recovers then the charge current drops off.
A starter pulls a lot of current, but only for a very short time, so overall, it shouldn't discharge the battery that much. Even if recharge current was limited to 5 amps, it wouldn't take long to bring the battery back up.

I think one issue a lot of people are having is cheap batteries or batteries that are in need of replacement.
I've got a 1 ton pickup at work and one at home. Both have two way radios in it.
The truck at work is a gas engine with one battery. The radios will often restart after engine cranking. Not a big deal.
My personal truck is a Diesel and has two batteries. Rarely does that radio restart after charging.

I've had other trucks that did this. Sometimes the restarts wouldn't happen, but as the battery aged it would. Lower temperatures can impact battery performance, too.

More often, improper installation is an issue.
Making sure all battery connections are clean is important. Periodic maintenance should include removing battery cables and cleaning the connections well.
Wire size needs to be appropriate for the radio.
Properly installed connectors are necessary. Cheap crimp on connectors installed with the cheap "smash-n-pray" style crimpers leads to a lot of problems.
Corrosion is an issue, too, especially under the hood.
Poor grounding is a big deal.

I've fixed a lot of radios over the years by just fixing all the poorly done wiring jobs done by "installers".

I've heard people mention having had bad luck with crimp connections when dealing with higher current--have you noticed problems with that? Also one thing I'd like to add is to suggest fusing the wiring right at the battery--that way if insulation gets damaged on its' way into the vehicle (like where it passes through the firewall and the installer didn't use a protective grommet), the wiring between the battery and inside the vehicle won't start smoldering and/or shorting out the battery.

 

[mmckenna]

I've heard people mention having had bad luck with crimp connections when dealing with higher current--have you noticed problems with that?

That's often the issue I see. It's usually an issue with the tool and/or the tool operator. The cheap crimpers sold at most auto parts or hardware stores are pretty awful for making good crimps. Might be good enough for a stereo install, but not anything high current. Using a proper full cycle crimp tool makes a difference.
The thin metal crimpers don't usually crimp enough of the terminal to do a good job. They also don't provide any feedback to the user when the connection has been fully crimped.
I've read posts where people will slam crimp connections as "inferior", but it's almost always the installer thats at fault. Amateur radio operators being notorious cheapskates doesn't help the issue.

Part of my job includes maintaining about 20 high current -48vDC power plants for our phone system and data network. These systems will support anywhere from 1200 up to several thousand amps, including 2000ah battery systems. We use conductors in the 350 - 750MCM range and those are all crimped. Difference is that the barrels on the crimps are long and the tools are specifically designed to crimp to manufacturer standards. The crimp tools alone run in the $5000 range. Even with inverter plants that will pull 1200 amps off the -48vdc systems, I've never had one fail. I can check them with a IR thermometer and they are running cool.

Unfortunately most installers are in way too much of a rush and will slap together whatever it takes to make things work. Over time corrosion and vibration take their toll.

Also one thing I'd like to add is to suggest fusing the wiring right at the battery--that way if insulation gets damaged on its' way into the vehicle (like where it passes through the firewall and the installer didn't use a protective grommet), the wiring between the battery and inside the vehicle won't start smoldering and/or shorting out the battery.

Yes, often overlooked. Some installers don't comprehend the way this works and think a fuse will magically protect the entire run.
For my work and personal vehicles, I usually run a #6 or larger wire from the battery to a fuse or breaker within about a foot. From there the #6 runs to where ever the RF decks are located. That connects to a local fused distribution block to feed the individual radios and other components. All crimped connectors are done with the right tools and followed up with marine grade heat shrink. Split loom or some other wiring protector gets used where appropriate and all pass throughs get grommets. Proper wiring support is important too.

Some scary *$#! I've seen. Unfortunately I lost a lot of my photos a few years ago, but I used to keep photos of the stuff. Wire nuts in mobile applications, wads of electrical tape, undersized wire, wires just twisted together and taped. I could go on. Some of these from "reputable install shops".

 

[mmckenna]

I've heard people mention having had bad luck with crimp connections when dealing with higher current

There are some really good photos and videos on line from some of the larger companies that make cable lugs. Done properly they create a "gas tight" connection and the individual strands will fuse under enough crimping pressure. There are some good photos where they've taken crimped connectors and sawed them off to show the cross section. Makes it easy to see what a properly installed connectors looks like from the inside.

 

[N4KVE]

I never crimp wires. I always solder them myself. That way, I know the connection is 100%.

 

[RFI-EMI-GUY]

There are some really good photos and videos on line from some of the larger companies that make cable lugs. Done properly they create a "gas tight" connection and the individual strands will fuse under enough crimping pressure. There are some good photos where they've taken crimped connectors and sawed them off to show the cross section. Makes it easy to see what a properly installed connectors looks like from the inside.

The problem is that most consumer crimp tools don't apply sufficient pressure in the correct location.

The commercial tools will set you back a bunch of money.



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[prcguy]

Properly crimped connections are more reliable than soldered. Look at any wiring in aircraft, crimp only and soldered connections are prohibited. This is from someone who was Mil 454 and Weapon Spec qualified in soldering and a certified inspector for the same.

I never crimp wires. I always solder them myself. That way, I know the connection is 100%.

 

[AK9R]

When it comes to various electrical connectors, whether to crimp or solder often seems to be based on past negative personal experiences. Those negative experiences seem to be driven by failed crimp jobs that used poor tools, connectors, or techniques. And, once experiencing that negative outcome, the anti-crimp opinion seems to last forever. Kinda like being bitten by a dog as a child.