momentary low volt problem @ start-up

All two way radios that are hooked to the battery or ignition wire will shut down for a short time while cranking the engine. One way to get around this would be to install a second battery dedicated to the radio and being charged through an isolator. Another way is to delay the radio from turining on until the vehicle has started. This can be accomplished with a timed relay setup or with a sence circuit off the alternator.

I hope this helps in your decision,

Tom

I actually run 2 batteries and my stereo plays right through startup. even with the system cranked...however, I have my deck directly powered, bypassing the ignition wire, and running everything off constant 12v...

some people think its a pain in the ass to have to shut your stereo off manually everytime you get out of the car, but I prefer it that way...

I think that the actual ignition signal cuts everything out so that it gets as much of the batteries power as possible...you could try wiring the 2ways directly to the battery and using a toggle to turn them on and off...I am kind of grasping at straws here, but not coming up with anything too fancy...maybe try the direct wire and see if the radios turn off or not...it may just be that the battery cant produce enough juice through startup to maintain the radios...

I just thought of this, re-reading all the posts here...would it be possible to run the radios off of a cap and wire in an isolator that could be used to isolate the cap itself only during startup?

do the radios have to be on 24/7?

I like that thinking along the lines of the isolator. I wonder what the lowest amperage is that isolators are available. The radio probably only draws .5amp max while idle.

To answer your question the radios are on anytime the vehicle is on duty and when the officer starts up the car the low voltage de-activates one of the radios critical functions that the officer then has to manually re-enable. If he does not hten the radio does not operate properly and creates a real safety issue in emergencies.

Let me know about the cap. isolator. I spoke to Monster earlier today and their tech dept is hopeful that a 1 farrad cap may help the problem. I am going to try to do some footwork to a local high end audio shop and bend their installation depts. ear on the subject. Since around 100 cars are affected they could make a few bucks off of supplying me with the equipment so maybe they will be willing to help.

I appreciate your help I know this is a little off the beaten path for this forum but anything is worth a try.

that sounds good to me personally, but I am no pro...mebbe some of the longstanding 12v gurus could field that one and shed some light on this shady situation...

anyone?

I think since the radio is fused at 20 amps if I install 3- 10amp diodes in parallel then I can achieve my goal as long as the 1 farrad cap will provide the needed power to the radio alone for the instant @ start up. I also seek enlightenment from the gurus!

Speak o great ones!!!

Just jumped onto this bandwagon ( thought you guys had something fugured out already. ) I have one question for you about the radio wiring hookup. Is the radio hooked up to IGNITION power through the ignition switch or the back of the radio ? Or are both the IGN & the CONSTANT hooked up to the battery ? I ask this because if the radio was hooked up to a second IGN wire, then it would temporarily loose power in the crank position. If the installer used the IGN 1 wire, then it would have power throughout the crank positions and the ON position but 0 in the OFF & ACC positions.

What I would try first is to hook up the IGN wire to constant ( as long as the Kenwood has a power OFF button ) otherwise it will drain the battery. If this does not work what you can do is set up a relay to engage from the IGN 1 and have 87 to the battery and 30 to the IGN wire on the Kenwood. This would get 12 volts straight from the battery as opposed to getting 12 volts from the IGN wier in the harness making the relay act as an isolator from the ignition switch.

I would also check to see the vehicles batteries & if they need replacing. I live in Canada and the batteries that we have normally last 3-4 years with the extreme cold & they loose their electrolyte characteristics. I do not suggest another battery ( if the capacitor idea doesn't pan out ) , but rather a larger CC amp battery will more than likely remedy the problem.

Cold reduces the battery's starting capacity therefore it will seem to draw more amperage to start the car during a cold morning. If you replace the battery with a larger CC battery, you will alleviate the strain on the smaller CC amp battery.

copcarguy wrote:

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Has anyone had a problem with a vehicles voltage falling below the threshold tolerance of some electronics when cranking the engine? If so were you able to find a solution that provides constant 12 volts during the short period of engine cranking. I have a problem in this regard with a Kenwood two-way radio in one of our customers cars and their idea was dual batteries ( seems like massive overkill!!! ) Any help would be greatly appreciated.

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