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  • Millstonemike
    replied
    Originally posted by devnull View Post

    .... As long the voltage at the battery is above the float voltage, about 13.25V it's not discharging and it's most certainly charging if it's at 13.8 to 14V albeit at a slower rate than if it was seeing 14.4V.
    I agree with your assessment of battery voltages. But I'm talking about the alternator. The low voltage is an indicator the alternator is being overworked.

    The alternator is regulated with the windings putting out higher voltages that can be regulated to the desired output: 14 Volts whatever That's how it outputs a constant voltage over a wide range of rpms. When a load causes the voltage to drop below the regulated voltage, it's windings can't produce enough voltage - at that rpm. That can happen on idle and with lights and heater fan running at higher rpms.

    The OP should just run with the stock alternator and super-caps at the amp. If his "battery" light comes on - not charging - he needs a beefier alternator.


    Leave a comment:


  • devnull
    replied
    Originally posted by Millstonemike View Post

    From Nissan's dealer service manual for my Maxima. There is a drop from the generator output to the battery under load (headlights, heater fan, etc.) through the (140 A) fuseable link. Nissan spec.'s that drop to be 0.2 V or less.

    Measured at my battery moments ago: High idle 14.35, low idle 14.2. With headlights and heater fan on high at 1500 rpms, 14.28. There's always tolerances in any car. But the nominal auto voltage is spec.'ed at 14.4 V.

    Though, I should have asked the OP were he tapped to measure the voltage.

    Fro the Nissan dealer service manual for my Maxima; measured at the "generator" on normal idle.

    Click image for larger version

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    This helps illustrate the point I was trying to make, the output voltage and current ratings for an alternator are arbitrary values chosen by the manufacturer based on the conditions they believe the car will see and how fast they want to recharge the battery after starting. I had an 85 Maxima and the service manual for it shows 14.4 to 15V for the alternator with a nominal rating of 12V-70A. Just because the voltage under load is under the rated output voltage doesn't mean there's a problem or the car won't run. Look at how low the voltage is during starting. Fuel pump and engine management computer still work at well under 11V. Less than the rated alternator voltage means that it will take longer to recharge the battery as long as the voltage is above the float level.

    The nominal voltage for both vehicles is 12V, per the charts, not 14.4V. In the case of your maxima the midpoint or we can call it "nominal" alternator output voltage is 14.4V. In the case of my first gen maxima the midpoint for the alternator voltage was 14.7V. Could you swap alternators between the vehicles, yes. Could you swap batteries between them, yup. Would they both still run, yup. So why is there a difference in the alternator voltage spec for two cars that both have the same nominal operating voltage?

    The only thing magical about the 14.4V number and lead acid batteries is that it is the voltage that a lead acid battery will start outgassing. This wasn't a problem with batteries that you could do maintenance on. Obviously Nissan came to the conclusion that they were cooking their batteries with voltage regulators that would allow up to 15V. They could have just as easily chosen 13.8 or 14 as the maximum voltage the alternator would produce which would have caused longer recharge times.

    I think what's bugging me is the fact that you stated the OP had a problem with his voltages because when he cranked up the system it was 13.8 to 14V not 14.4V and wasn't keeping up with his system. As long the voltage at the battery is above the float voltage, about 13.25V it's not discharging and it's most certainly charging if it's at 13.8 to 14V albeit at a slower rate than if it was seeing 14.4V.


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  • Fishchris
    replied
    Originally posted by Millstonemike View Post

    From Nissan's dealer service manual for my Maxima. There is a drop from the generator output to the battery under load (headlights, heater fan, etc.) through the (140 A) fuseable link. Nissan spec.'s that drop to be 0.2 V or less.

    Measured at my battery moments ago: High idle 14.35, low idle 14.2. With headlights and heater fan on high at 1500 rpms, 14.28. There's always tolerances in any car. But the nominal auto voltage is spec.'ed at 14.4 V.

    Though, I should have asked the OP were he tapped to measure the voltage.

    Fro the Nissan dealer service manual for my Maxima; measured at the "generator" on normal idle.

    Click image for larger version

Name:	Volts.png
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    I don't remember where my mechanic (friend) tapped into for the voltage gage, but I remember him saying it was a good place for reference.

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by devnull View Post

    You've made the assumption that the OP's vehicles alternator is designed for 14.4V steady state There are a lot of vehicles on the road that 14.4V is considered out of spec, too high. I had a car that would start around 14.2 and after idling for a while would drop to 13.8 or so.
    From Nissan's dealer service manual for my Maxima. There is a drop from the generator output to the battery under load (headlights, heater fan, etc.) through the (140 A) fuseable link. Nissan spec.'s that drop to be 0.2 V or less.

    Measured at my battery moments ago: High idle 14.35, low idle 14.2. With headlights and heater fan on high at 1500 rpms, 14.28. There's always tolerances in any car. But the nominal auto voltage is spec.'ed at 14.4 V.

    Though, I should have asked the OP were he tapped to measure the voltage.

    Fro the Nissan dealer service manual for my Maxima; measured at the "generator" on normal idle.

    Click image for larger version

Name:	Volts.png
Views:	52
Size:	50.7 KB
ID:	1431898



    Leave a comment:


  • devnull
    replied
    Originally posted by Millstonemike View Post

    Standby batteries and Auto batteries are two very different situations. I agree with your take on the VLRA batteries in a float capacity. But car systems are designed to be 14.4 V. The higher voltage helps remove irregularities due to the high current bursts. And modern ""maintenance free" batteries are designed to recover the gas, there vents being a safety valve. Years ago, adding water was somewhat routine maintenance for plain old lead acid batteries..

    And the fact remains, the OP's alternator capacity cannot meet the load at it's designed output of 14.4 V. Hence it is overtaxed.

    BTW: AGM (Absorbed Glass Mat) lead acid batteries (those sealed cells you see in standby lighting, etc.) have calcium added to their chemistry. All their "spec" voltages are ~5% higher than plain lead acid batteries. For example, 13.3 V is 100% charged rested (measured some hours after charging is complete). My 3-stage AGM chargers' initial stage brings an AGM battery to ~15 V. Once attained, that drops down for final charging and then float. The initial charge helps remove deposits formed dung the discharge cycle.
    You've made the assumption that the OP's vehicles alternator is designed for 14.4V steady state There are a lot of vehicles on the road that 14.4V is considered out of spec, too high. I had a car that would start around 14.2 and after idling for a while would drop to 13.8 or so. What the voltage sags to under full load is doesn't matter as long as it's above the minimum input on his amplifiers. This is just like your house, everything keeps working if the AC is on or not, the input voltage is just a little lower to everything while the AC is running. As long as the voltage stays above 13.2 or so, under load, the batteries are not discharging. Even if the voltage does occasionally sag under load as long as the vehicle is idled a little bit after the load the batteries will be recharged.

    FLA and VRLA have the same chemistry, doesn't matter if they are stationary or moving. Car alternators are designed for a fast recharge rate at well above the optimum charging voltage because automakers have no control over the start/run/stop times of their vehicles. They need to be conservative with the minimum run times to recharge the batteries, They could have just as easily chosen 13.5V but then it would have taken longer to recharge the battery after starting. The upside to vehicle batteries is that the movement and vibrations of the vehicle reduces the stratification of the electrolyte and knocks the bubbles off the plates leading to more even and consistent plate regrowth.

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  • Millstonemike
    replied
    Originally posted by devnull View Post

    Actually 14.4 volts is the point where the battery will start off gassing, which is what causes problems when recharging, The bubble formation is what contributes to the degradation of the battery capacity and the inconsistent reformation of the plates. 13.8V is perfectly acceptable and will actually help prolong battery life. A cars alternator is designed for a very rapid recharge rate, no where near the optimized charging voltage for prolonged battery life. Also, an alternator is always over charging a car battery. When the battery is fully charged the alternator does not reduce it's output voltage down to the float level. Nor does a car alternator take into account the temperature of the battery which also has an impact on the charge and float voltage.

    Maintenance free, VRLA, batteries are much more sensitive than flooded batteries to charging voltage because you can't top them off with distilled water and/or acid to bring the electrolyte levels back to "factory" specific gravity and volume levels.

    The rule of thumb for the VRLA stationary battery plants I've worked with were 13.75 for charging and 13.2 for float. Plant alarms were set to go off about .1V higher.
    Standby batteries and Auto batteries are two very different situations. I agree with your take on the VLRA batteries in a float capacity. But car systems are designed to be 14.4 V. The higher voltage helps remove irregularities due to the high current bursts. And modern ""maintenance free" batteries are designed to recover the gas, there vents being a safety valve. Years ago, adding water was somewhat routine maintenance for plain old lead acid batteries..

    And the fact remains, the OP's alternator capacity cannot meet the load at it's designed output of 14.4 V. Hence it is overtaxed.

    BTW: AGM (Absorbed Glass Mat) lead acid batteries (those sealed cells you see in standby lighting, etc.) have calcium added to their chemistry. All their "spec" voltages are ~5% higher than plain lead acid batteries. For example, 13.3 V is 100% charged rested (measured some hours after charging is complete). My 3-stage AGM chargers' initial stage brings an AGM battery to ~15 V. Once attained, that drops down for final charging and then float. The initial charge helps remove deposits formed dung the discharge cycle.

    Leave a comment:


  • devnull
    replied
    Originally posted by Millstonemike View Post

    I assume your "aftermarket voltage gauge" has a digital readout. If so, I'd compare it's readout against a reasonable accurate digital meter to ensure it's accurate.

    Assuming it is, your stated voltages are an issue. A car's alternator, running above idle, is set to deliver 14.4 V to the electrical system , and, most importantly, the battery. The 14.4 V output has been standardized in the automotive industry for decades. And your battery needs to see 14.4 V often or it will diminish it's longevity.

    Your indicated 13.8 V to 14 V while driving is an indication that your stock alternator cannot meet the full demand of your system at it's designed regulated output of 14.4 V. The alternator is working above it's rated amp capacity whenever you "crank it up". Hence the voltage drop below 14.4.

    Try another test. While driving at a moderate speed, crank it up, turn on your headlights and your heater fan on high. Then read the voltage. That's virtually the worst case demand on the alternator.

    I'd go with a heavier alternator and super caps right at the amp's power inputs to handle music demand peaks. More auto batteries do nothing to correct your fundamental issues and become just another load on an already over taxed alternator.

    Lastly, never use the system when the car is off for any extended period of time, even at low levels. Car batteries are made to deliver high current for short periods of time (e.g., power the starter). Moderate drains for longer times (like 30 mins) will cause them to fail prematurely - diminished lifetime. That's because a car's starter battery has many, thin internal lead plates. The surface area of all those thin plates enables the battery to generate the current needed by the starter motor.

    To generate current, the lead plates begin to dissolve in the acid. When recharging, the dissolved lead is restored to the plates. But prolonged periods of low drain will eat away at the thin plates leaving less area for the dissolved lead to reattach. Compare that with a deep cycle marine battery. They have significantly fewer, albeit much thicker plates. They can't supply huge currents due to less plate surface area, but the plates maintain their integrity over longer, lower drain cycles.

    My good bud was replacing his battery every two years, even after buying top rated, "Platinum" batteries. That's because he liked to sit in his car everyday at lunchtime and listen to his (stock) car radio.
    Actually 14.4 volts is the point where the battery will start off gassing, which is what causes problems when recharging, The bubble formation is what contributes to the degradation of the battery capacity and the inconsistent reformation of the plates. 13.8V is perfectly acceptable and will actually help prolong battery life. A cars alternator is designed for a very rapid recharge rate, no where near the optimized charging voltage for prolonged battery life. Also, an alternator is always over charging a car battery. When the battery is fully charged the alternator does not reduce it's output voltage down to the float level. Nor does a car alternator take into account the temperature of the battery which also has an impact on the charge and float voltage.

    Maintenance free, VRLA, batteries are much more sensitive than flooded batteries to charging voltage because you can't top them off with distilled water and/or acid to bring the electrolyte levels back to "factory" specific gravity and volume levels.

    The rule of thumb for the VRLA stationary battery plants I've worked with were 13.75 for charging and 13.2 for float. Plant alarms were set to go off about .1V higher.

    Leave a comment:


  • Psycoacoustics
    replied
    Originally posted by Millstonemike View Post

    I assume your "aftermarket voltage gauge" has a digital readout. If so, I'd compare it's readout against a reasonable accurate digital meter to ensure it's accurate.

    Assuming it is, your stated voltages are an issue. A car's alternator, running above idle, is set to deliver 14.4 V to the electrical system , and, most importantly, the battery. The 14.4 V output has been standardized in the automotive industry for decades. And your battery needs to see 14.4 V often or it will diminish it's longevity.

    Your indicated 13.8 V to 14 V while driving is an indication that your stock alternator cannot meet the full demand of your system at it's designed regulated output of 14.4 V. The alternator is working above it's rated amp capacity whenever you "crank it up". Hence the voltage drop below 14.4.

    Try another test. While driving at a moderate speed, crank it up, turn on your headlights and your heater fan on high. Then read the voltage. That's virtually the worst case demand on the alternator.

    I'd go with a heavier alternator and super caps right at the amp's power inputs to handle music demand peaks. More auto batteries do nothing to correct your fundamental issues and become just another load on an already over taxed alternator.

    Lastly, never use the system when the car is off for any extended period of time, even at low levels. Car batteries are made to deliver high current for short periods of time (e.g., power the starter). Moderate drains for longer times (like 30 mins) will cause them to fail prematurely - diminished lifetime. That's because a car's starter battery has many, thin internal lead plates. The surface area of all those thin plates enables the battery to generate the current needed by the starter motor.

    To generate current, the lead plates begin to dissolve in the acid. When recharging, the dissolved lead is restored to the plates. But prolonged periods of low drain will eat away at the thin plates leaving less area for the dissolved lead to reattach. Compare that with a deep cycle marine battery. They have significantly fewer, albeit much thicker plates. They can't supply huge currents due to less plate surface area, but the plates maintain their integrity over longer, lower drain cycles.

    My good bud was replacing his battery every two years, even after buying top rated, "Platinum" batteries. That's because he liked to sit in his car everyday at lunchtime and listen to his (stock) car radio.
    Nicely said! A very good explanation!

    Have Fun, Mark

    Leave a comment:


  • Fishchris
    replied
    Even being 12 yo, my alternator does do a lot of charging in the 14.4 to 14.7 range, just not when I'm beating on the stereo. To be honest though, with pretty much every other setup I've had in the past, it didn't do this well, often dropping to the mid 12's, and yet I never damaged anything.

    Honestly, impo, I don't think I have any major power issues right now. I'm just thinking about future expansion.
    ​​​

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by Fishchris View Post

    I added and aftermarket voltage Gage, and with my latest system, it holds 13.4 volts parked and beating on it, and 13.8 to 14 driving with it cranked up.
    ...
    I assume your "aftermarket voltage gauge" has a digital readout. If so, I'd compare it's readout against a reasonable accurate digital meter to ensure it's accurate.

    Assuming it is, your stated voltages are an issue. A car's alternator, running above idle, is set to deliver 14.4 V to the electrical system , and, most importantly, the battery. The 14.4 V output has been standardized in the automotive industry for decades. And your battery needs to see 14.4 V often or it will diminish it's longevity.

    Your indicated 13.8 V to 14 V while driving is an indication that your stock alternator cannot meet the full demand of your system at it's designed regulated output of 14.4 V. The alternator is working above it's rated amp capacity whenever you "crank it up". Hence the voltage drop below 14.4.

    Try another test. While driving at a moderate speed, crank it up, turn on your headlights and your heater fan on high. Then read the voltage. That's virtually the worst case demand on the alternator.

    I'd go with a heavier alternator and super caps right at the amp's power inputs to handle music demand peaks. More auto batteries do nothing to correct your fundamental issues and become just another load on an already over taxed alternator.

    Lastly, never use the system when the car is off for any extended period of time, even at low levels. Car batteries are made to deliver high current for short periods of time (e.g., power the starter). Moderate drains for longer times (like 30 mins) will cause them to fail prematurely - diminished lifetime. That's because a car's starter battery has many, thin internal lead plates. The surface area of all those thin plates enables the battery to generate the current needed by the starter motor.

    To generate current, the lead plates begin to dissolve in the acid. When recharging, the dissolved lead is restored to the plates. But prolonged periods of low drain will eat away at the thin plates leaving less area for the dissolved lead to reattach. Compare that with a deep cycle marine battery. They have significantly fewer, albeit much thicker plates. They can't supply huge currents due to less plate surface area, but the plates maintain their integrity over longer, lower drain cycles.

    My good bud was replacing his battery every two years, even after buying top rated, "Platinum" batteries. That's because he liked to sit in his car everyday at lunchtime and listen to his (stock) car radio.

    Leave a comment:


  • Serpentus
    replied
    So i think the answer is the most amperes your wallet can afford lol.

    Leave a comment:


  • Fishchris
    replied
    Originally posted by Serpentus View Post
    First you need to know how many watts your system is going to consume. Then you know you're on a 14v system, so it becomes a simple math problem limited only by cost. Don't forget the vehicle needs some power to run things like blower motor, lights, wipers and whatever else. I figure the first 300 watts or so are free, after that you probably start stressing the electrical system.

    I've never needed gobs of power because I generally used a more efficient acoustic loading system in my vehicles - horn woofers and high fs/high sensitivity mids.
    I hear you on that. Only thing is, it's hard to say how much "watts my system will need" down the road. Right now, less than 2000, and surprisingly, my stock alternator seems to handle it quite well. I added and aftermarket voltage Gage, and with my latest system, it holds 13.4 volts parked and beating on it, and 13.8 to 14 driving with it cranked up.
    But I'm really into SPL + SQ too. I could see myself eventually building a 5Kwt to 10Kwt system.

    And of course I I don't "need" that much... Or really anywhere near that much. No more than cars need to go 300 mph. They just build stuff like this because it's crazy, and they can 🙂

    Leave a comment:


  • Serpentus
    replied
    First you need to know how many watts your system is going to consume. Then you know you're on a 14v system, so it becomes a simple math problem limited only by cost. Don't forget the vehicle needs some power to run things like blower motor, lights, wipers and whatever else. I figure the first 300 watts or so are free, after that you probably start stressing the electrical system.

    I've never needed gobs of power because I generally used a more efficient acoustic loading system in my vehicles - horn woofers and high fs/high sensitivity mids.

    Leave a comment:


  • Fishchris
    replied
    Originally posted by Serpentus View Post
    Might want a high output alternator or even a second alternator.
    No, "I DO" want a HO alternator. The only question is, which one, and how strong ?

    Leave a comment:


  • Serpentus
    replied
    Might want a high output alternator or even a second alternator.

    Leave a comment:

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