Ham radio reboots when I start the engine

#1
I have my TM-D710G wired directly to the battery like the manual says it should be, and I have a new battery in my 4Runner.

Still, I find that that the radio reboots if I start the engine. I'm pretty sure the voltage drops when the starter is engaged. An obvious solution would be to install a dual battery system, but I don't really want to spend that much coin on this particular problem.

Is this a common problem? Has anyone found a good solution?
 

FlipperFla

Active member
#2
How old is your battery? I would check that and clean all the terminals. If all that is good, check the specs on the battery see what the cold cranking amps spec is, you could probably find one with a higher CCA rating then you probably wouldnt get as big voltage drop. Also how long and what gauge run to the radio might be a factor
 
#3
That should be normal. With pretty much all the power from the battery directed to the starter, the voltage for the radio should drop below operating ranges and the radio shuts down temporarily.

I don't know about more modern vehicles, but our Land Cruisers shut everything off when the starter is engaged.
 
#4
I have my TM-D710G wired directly to the battery like the manual says it should be, and I have a new battery in my 4Runner.

Still, I find that that the radio reboots if I start the engine. I'm pretty sure the voltage drops when the starter is engaged. An obvious solution would be to install a dual battery system, but I don't really want to spend that much coin on this particular problem.

Is this a common problem? Has anyone found a good solution?
This is normal because of the voltage drop. I would consider turning the radio off when engaging the starter. Voltage fluctuations aren't good for circuitry. Low voltage followed by a quick surge before the alternator levels out can't be good for the radio.

Sent from my SM-G935P using Tapatalk
 
#6
As already pointed out, modern radios have no tolerance for low voltage so this behavior is expected. This, and the real potential of damage to the radio, prompted me to make a fundamental change in how I powered comm gear.

Having been a ham for a few years, I started out with the "wire directly to the battery, POS and NEG with fuses" plan. That plan originated back when radios were more tolerant.

My current method is using a local battery, but with a charging link to the truck system. By local I mean near the radio. In my case (in 3 vehicles) this means a power distribution strip with Anderson PowerPoles, with a 12v 10AH battery on a 6 inch lead (10 ga wire). All the radios plug into the power strip so are effectively isolated from the truck. To keep the 12v "local" battery charged, there is a fused small gauge wire to the truck system (14 ga or so). Shortening the radio leads is a good idea. I removed my heavy radio cables that did go to the truck battery and simply plug the charging wire into the truck's dash power socket (most good for 20 A). That socket needs to be one that powers off when the truck is off so as to prevent feedback into the truck when truck voltage is lower. Optionally, add a diode to prevent feedback, but that will reduce charging voltage by half a volt or so.

Peak charging voltage on the three trucks reaches 14.4 to 14.8 vdc for part of the charge cycle so the "local" battery gets topped up nicely.

Another option is a voltage stabilizing capacitor like sold by MFJ (model 4403) and others. The capacitor would need to be wired near the radio. This is a simple fix for the original problem but does not provide operation with radios disconnected from the truck.
 
#7
I have all my radios and accessories powered through a secondary fused buss.
Don't have any problem with anything dropping offline during engine start.
 
#8
This only happens to my radios when my truck battery voltage drops too low. Generally when the battery is bad or discharged.

Great idea by tennmogger above. If I ever buy another expensive radio I may consider doing the same. For now my radio is just hard wires to a bluesea fuse box, which is wired to the battery.
 
#9
As already pointed out, modern radios have no tolerance for low voltage so this behavior is expected. This, and the real potential of damage to the radio, prompted me to make a fundamental change in how I powered comm gear.

Having been a ham for a few years, I started out with the "wire directly to the battery, POS and NEG with fuses" plan. That plan originated back when radios were more tolerant.

My current method is using a local battery, but with a charging link to the truck system. By local I mean near the radio. In my case (in 3 vehicles) this means a power distribution strip with Anderson PowerPoles, with a 12v 10AH battery on a 6 inch lead (10 ga wire). All the radios plug into the power strip so are effectively isolated from the truck. To keep the 12v "local" battery charged, there is a fused small gauge wire to the truck system (14 ga or so). Shortening the radio leads is a good idea. I removed my heavy radio cables that did go to the truck battery and simply plug the charging wire into the truck's dash power socket (most good for 20 A). That socket needs to be one that powers off when the truck is off so as to prevent feedback into the truck when truck voltage is lower. Optionally, add a diode to prevent feedback, but that will reduce charging voltage by half a volt or so.

Peak charging voltage on the three trucks reaches 14.4 to 14.8 vdc for part of the charge cycle so the "local" battery gets topped up nicely.

Another option is a voltage stabilizing capacitor like sold by MFJ (model 4403) and others. The capacitor would need to be wired near the radio. This is a simple fix for the original problem but does not provide operation with radios disconnected from the truck.
What does your charging wire consist of? Is it just a lead from the batt terminals to the 12v outlet? Do you leave it plugged in all the time?
 
#11
As already pointed out, modern radios have no tolerance for low voltage so this behavior is expected. This, and the real potential of damage to the radio, prompted me to make a fundamental change in how I powered comm gear.

Having been a ham for a few years, I started out with the "wire directly to the battery, POS and NEG with fuses" plan. That plan originated back when radios were more tolerant.

My current method is using a local battery, but with a charging link to the truck system. By local I mean near the radio. In my case (in 3 vehicles) this means a power distribution strip with Anderson PowerPoles, with a 12v 10AH battery on a 6 inch lead (10 ga wire). All the radios plug into the power strip so are effectively isolated from the truck. To keep the 12v "local" battery charged, there is a fused small gauge wire to the truck system (14 ga or so). Shortening the radio leads is a good idea. I removed my heavy radio cables that did go to the truck battery and simply plug the charging wire into the truck's dash power socket (most good for 20 A). That socket needs to be one that powers off when the truck is off so as to prevent feedback into the truck when truck voltage is lower. Optionally, add a diode to prevent feedback, but that will reduce charging voltage by half a volt or so.

Peak charging voltage on the three trucks reaches 14.4 to 14.8 vdc for part of the charge cycle so the "local" battery gets topped up nicely.

Another option is a voltage stabilizing capacitor like sold by MFJ (model 4403) and others. The capacitor would need to be wired near the radio. This is a simple fix for the original problem but does not provide operation with radios disconnected from the truck.
I like the idea of adding a second battery, although I with your wiring you risk blowing a fuse if there's significant voltage difference between the local and starter batteries and you turn the key to the Accessory position.

Most of the smaller batteries I've found are AGM, and from what I've seen they want a higher charging voltage than lead acid batteries. This means your 10ah battery probably never gets fully charged and would get even less charged if you added a diode to protect against an almost depleted or worn out starter battery. How long have you been running this solution? I'm curious to see if you've established the longevity of the local battery yet.
 
#12
You are correct about AGM needing higher charge voltage, and that a fuse can blow if voltages are too different. This is a case where smaller wiring, and subsequent voltage loss, can be beneficial. If you are concerned just put a 1 Ohm resistor in series to limit current. Peak charge voltage will still be the same (just achieved a little more slowly).

If you want to try the local battery idea, why not use one of the cheapo SLA (sealed lead acid) batteries available anywhere. They can be charged under the same conditions as the vehicle battery. A 7 AH SLA battery can easily handle the peak current of a 100 Watt HF radio.

Almost every battery chemistry does require a little special attention. I use a Gates Cyclon 12v pack in my pickup and it has been running 3 years. It is lead based and charges at the same voltages as the truck battery, a good match.

The other two systems use homebrew 10AH packs of NiMh "D" cells. Those do require special handling but will operate for weeks on a typical truck charging cycle. Then I do a full charge on a charger with NiMh programming (Triton 2 Electrifly') to balance out the cells. This is a 12vdc input DC to DC charger so works fine in the trucks. These NiMh packs were built in 2014 and still work fine.

Good luck on your project.
 
#13
Last edited:
#14
Your radio SHOULD NOT reboot when your start your vehicle unless your battery is bad or going through a swtched circuit that is turned off when your starter is enguaged.
If your radio is wired directly to the batter (as it should be) then there is a battery issue.
 
#15
Gary, you give good advise on here, and thanks. However, my TM-281 Kenwood will not handle voltage drops to slightly below 11.5 volts before it drops out. A good battery under starter load can easily drop below 11.5 volts. Nothing wrong with the setup, just physics. Radios are not a tolerant as they used to be.
 
Top