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Effects of amplifier voltage fluctuations?

338_MtRushmore

Sr. Member
Jun 17, 2012
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The Dakotas
Is there any measurable negative effect of voltage fluctuations that are common in a mobile environment? I can swing 1200 watts with steady modulation and the amp and radio stay pretty steady at 14.1-14.2. When I talk, the charging system can't react fast enough and it will bounce around from 13 to 14.3. The IC-7100 is also seeing this voltage fluctuation. It doesn't seem to make a difference if I'm idling or reved up.

I'm thinking about trying a large power capacitor to see if that will smooth things out a bit. I have maybe 15' of 1/0 cable, 2 factory batteries, and the alternator does 200A@idle, and 370A@cruise.
 

Almost a 1.5vdc drop, not good. You have an issue with your wiring, batteries, and or alternator. You shouldn't have more than about a 1/2 volt drop. Less voltage = more current draw, more voltage = less current draw. Go through your system
 
Almost a 1.5vdc drop, not good. You have an issue with your wiring, batteries, and or alternator. You shouldn't have more than about a 1/2 volt drop. Less voltage = more current draw, more voltage = less current draw. Go through your system
So the ecm controlled voltage regulator should be able to instantly adjust output during speech peaks, but only within half a volt? Is the half a volt due to a technical reason, or is the half a volt just a typical variance? It just confused me because at full output I don't even have half a volt drop even with a fuse in line.

I bought some stainless bolts that I was going to weld on my exhaust for bonding, and planned to weld one on the frame to ground the alternator. Groundwire, I forgot a ground wire... I'm an idiot sometimes... and now I can't even find the bolts.

Thank you
 
Bonding the exhaust system does nothing from mine and MANY others experience, seriously, save yourself the headache. And for the alt ground, just drill a hole in the frame, waaay faster and easier. Hole, bolt, done! Tip: make sure you use the same cable for all your runs, its very important. You said you are using 1/0 (good for 350a max), so your battery neg to frame, alternator power to battery and alternator to frame ground, all need to be 1/0. Fyi: if your mobile has that voltage control thing you need to bypass that or you may be shit outa luck. Those things do not work with high current/voltage draw systems like cb, stereo etc.... oh yeah, this whole capacitor thing is ridiculous, it simply does nothing for cb radio applications, the discharge rate is just to quick among other things. Save your money and get another alternator and more batteries. Caps are fools gold.
 
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Bonding the exhaust system does nothing from mine and MANY others experience, seriously, save yourself the headache. And for the alt ground, just drill a hole in the frame, waaay faster and easier. Hole, bolt, done! Tip: make sure you use the same cable for all your runs, its very important. You said you are using 1/0 (good for 350a max), so your battery neg to frame, alternator power to battery and alternator to frame ground, all need to be 1/0. Fyi: if your mobile has that voltage control thing you need to bypass that or you may be shit outa luck. Those things do not work with high current/voltage draw systems like cb, stereo etc....
There aren't that many places I can drill and have access to install a nut and seal the connection. It's just easier for me to tack a bolt than fuss with drilling, and it will also allow for a shorter cable.

As far as I know all vehicles have a voltage regulator, but I would be very unhappy with mechman if they sold me a high dollar alternator that doesn't work for It's intended use.
 
Im talking about that voltage regulation computer crap that alot of new cars have now. Rubbish. Also if you dont have at least half a belt wrap on that small alt pully, you could be having belt slip which will show up as voltage issues as well, especially under load
 
Im talking about that voltage regulation computer crap that alot of new cars have now. Rubbish. Also if you dont have at least half a belt wrap on that small alt pully, you could be having belt slip which will show up as voltage issues as well, especially under load
It's a 2005 dodge ram diesel, so it can't be too new and fancy I wouldn't think. I would think that a slipping belt would be pretty apparent under a long full load, but maybe the instantaneous demand could be causing slippage?

My amp clamp doesn't show much over 100 amp draw, so it isn't even that big of a load considering the factory alternator is 160 amp.

I will add my missing ground wire and do some more testing tomorrow.
 
.... oh yeah, this whole capacitor thing is ridiculous, it simply does nothing for cb radio applications, the discharge rate is just to quick among other things. Save your money and get another alternator and more batteries. Caps are fools gold.
This appears to be an edit that I missed.

You don't think a 374 amp alternator is enough for an 8 pill? How would more batteries help? I've always been under the impression that typical auto batteries don't do anything above 13 volts.

After adding the alternator to frame ground my voltage was reading 14.18 at the alternator and 14.16 at the amp. I tried a few different meters and the lowest numbers I saw were 13.6, but often only dropped to 13.8X. When I turned the speech compression on I'd rarely see anything below 14, except maybe on the first word or 2. All of this testing was at idle. Could get slightly better with some rpm, but even then, would there be any improvement in output other than just swinging a meter?

I'd imagine results would be better on AM because there would be a constant draw to keep the alternator working harder. This could be wrong, but I may have to get a driver and find out.
 
Yes, 374a is big enough for an 8 if you dont have alot of other stuff pushing the alt to its limit (very bad) you just gotta do the math. More batteries more reserve capacity. On a single alt i wouldnt go with more than two batteries. And cheap typical auto batteries suck. You gotta buy the most expensive you can afford. Nothing less than agm batteries, thats for sure. For beginners, Get odyssey, great bang for the buck. also the fact that you say your only getting 14vdc from the alt tells me you have an issue. Again probably dc wiring. Mechman's all charge at 15vdc cold, then drop down to 14.8 - 14.6, no less. All 4 of mine stay at 14.8 with 1/2 volt drop on tx. (6.5kw).
 
Yes, 374a is big enough for an 8 if you dont have alot of other stuff pushing the alt to its limit (very bad) you just gotta do the math. More batteries more reserve capacity. On a single alt i wouldnt go with more than two batteries. And cheap typical auto batteries suck. You gotta buy the most expensive you can afford. Nothing less than agm batteries, thats for sure. For beginners, Get odyssey, great bang for the buck. also the fact that you say your only getting 14vdc from the alt tells me you have an issue. Again probably dc wiring. Mechman's all charge at 15vdc cold, then drop down to 14.8 - 14.6, no less. All 4 of mine stay at 14.8 with 1/2 volt drop on tx. (6.5kw).
I could probably send mine back and get one with an external regulator, but I'm not certain that it's worth a few hundred dollars to get an extra half a volt. I could try replacing the entire harness from the ecm to the alternator, but again, is it worth the hassle to maybe get half a volt?

I wouldn't know what else to even try to get the factory voltage up. Maybe a ground to the ecm?
 
For you, i would say just do the wiring upgrades i spoke about, make sure your two batteries are exactly the same (age, brand, type etc) and just run it. Side note: you will always need to put your batteries on a charger to top them off once in awhile. Alternators are not battery chargers and dont like to be. You can actually burn them up that way.
 
The only thing I didn't add is another ground from batteries to block. The batteries each read .003 volts from terminal to valve cover with the factory cables. Since my amp is grounded to the frame, I don't think another battery ground would do anything since the amp never sees battery voltage anyways.

I may do that in the future, but the rest of my 1/0 is going on my welder.
 

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