Battery voltage question
Thread Starter
Racer
Joined: Mar 2014
Posts: 461
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From: Central New York
Battery voltage question
I recently installed a set of George's ACA Bi-Xenon headlights and his Hi-4 harness, his DRL corner lights with LED switchback strips and bulbs, JWM's modded rear Halo's and his HID Fog lights. When the engine is off, there seems to be some intermittent firing of the various lights. Specifically, when the fogs fire, the headlights may not pop open, but do turn on. If the headlights pop open, one of the fogs may not fire. I queried George and we troubled shot the situation. When the ballasts take the voltage hit to spark the gas, they need a good jolt of electricity. So other circuits may not get what they need to function properly. Example, the ballasts take the initial voltage hit so the headlight motors cannot get the proper charge to lift the covers or vice versa. Everything works perfectly when the engine is running if turned on after the engine is running.
We narrowed it down to a voltage problem. I have a new 750 CCA battery but puts out only between 11.9 and 12.1 volts from WalMart. If I switch to an Optima yellow top will I have a better voltage output and more consistently? Other thoughts?
We narrowed it down to a voltage problem. I have a new 750 CCA battery but puts out only between 11.9 and 12.1 volts from WalMart. If I switch to an Optima yellow top will I have a better voltage output and more consistently? Other thoughts?
Thread Starter
Racer
Joined: Mar 2014
Posts: 461
Likes: 0
From: Central New York
How are you measuring the voltage of the battery? Hopefully not with the gauges on the dash. Those tell you the state of health of the charging system and NOT the state of health of the battery. With engine running they show the output voltage from the alternator. With engine off and key on there are many circuits on the C5 that are powered and loading the battery so unless you can quantify what is drawing power and how much, that value has little meaning.
11.9 to 12.1 volts if measured across the battery posts using a digital multi meter with the engine and key off is too low. Needs to be greater than 12.5 to keep electronics in the C5 happy. Have you had the battery load tested? Have you checked the electrical system for a parasitic loss?? C5 are infamous for parasitic drains. Engine will start with voltage of 12.2 volts (across the posts) or less but the electronics in the car will NOT be happy....
Before you invest in another battery i would certainly do some trouble shooting of the electrical system..... At a minimum put the battery on a charger and get it fully charged. A good battery at full charge will measute 12.7 to 12.9 volts across the posts as described above. JMHO
11.9 to 12.1 volts if measured across the battery posts using a digital multi meter with the engine and key off is too low. Needs to be greater than 12.5 to keep electronics in the C5 happy. Have you had the battery load tested? Have you checked the electrical system for a parasitic loss?? C5 are infamous for parasitic drains. Engine will start with voltage of 12.2 volts (across the posts) or less but the electronics in the car will NOT be happy....
Before you invest in another battery i would certainly do some trouble shooting of the electrical system..... At a minimum put the battery on a charger and get it fully charged. A good battery at full charge will measute 12.7 to 12.9 volts across the posts as described above. JMHO
Everything operated as designed before mods. Each mod tested before moving to the next one. Each new mod works perfectly independent of any other one. The issue is when you try them all at once which you can do when the car is factory with no issues. As you state, the battery should have a higher voltage when full.......I also knew that fact. My question is will one of the Optima batteries be better for a higher voltage output that is consistent and allows for many up and down drains and charges?
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
It sounds like your battery is simply bad. A yellow top won't gain you anything that a good fully charged battery will give you.
Be careful running it on a tender. A weak battery can cause a battery tender to over-charge it and boil it.
Be careful running it on a tender. A weak battery can cause a battery tender to over-charge it and boil it.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Where are you taking the input voltage for the module from??? You may have selected a point supplied by the ignition switch and it is NOT providing you the necessary current and Voltage that you need.
Our C5 Ignition switches are well known for having burnt contacts and providing less than adequate output voltages and less than optimum current. Actually read with a meter the voltage on the modules that you are trying to operate.
The optimum method of supplying power to the lighting modules would be to use a relay. Use the C5 switch voltage to control the relay and the relay output can be from a B+ fused source. That will provide you ample current and voltage,
Our C5 Ignition switches are well known for having burnt contacts and providing less than adequate output voltages and less than optimum current. Actually read with a meter the voltage on the modules that you are trying to operate.
The optimum method of supplying power to the lighting modules would be to use a relay. Use the C5 switch voltage to control the relay and the relay output can be from a B+ fused source. That will provide you ample current and voltage,
Last edited by Bill Curlee; Aug 9, 2014 at 11:06 PM.
