Just a few dumb questions... extra batteries

[Fishchris]

So after messing with car audio for 30 years... wait, did have 1 extra battery in a truck, but that was so long ago, I don't remember much about it ?
Anyway, I'm thinking it should be as easy as; Extending the 1/0 cable I have going from my battery under the cab of my truck, and back up inside the back of my super cab... to instead, coming up into the front of my bed and connected to (I think I'm going to start with 4 big, relatively strong, yet dirt cheap batteries) then dropping back down through the bed, and up into the cab, though the same original spot. Simple as this, right ? 1/0 should be enough to handle the juice from my stock 130 amp alternator, right ? Hope to upgrade that soon, but still not sure the brand. Surely there must be a better "value" than Mechman...

Oh ! What about a battery isolator ? I did use one in my old Chevy S-10 with the extra battery (my memory fades back and I think it worked great !

This alternator is looking really appealing....

https://www.phoenix-alternator.com/PartDetails.aspx?OS1=HO&IDNum=123659

[Dukk]

Yep, adding additional batteries is pretty much that easy. Heavy ground to frame and you are set.

Isolators are generally poo-poo'd on because there is a voltage drop through them. Finding one for that kind of amperage can be hard as well. A high amperage fuse or circuit breaker should be added to EACH end of the heavy cable from the underhood battery to the additional ones and also from the auxiliary bank out to the amp rack.

Ultimately, additional batteries are mostly useful for extending key-off play time. When running, the power comes from the alternator and when a bass note hits that requires more current than the alternator can produce, the alternator voltage will sag until it hits the resting voltage of the batteries. At that point they help but until then, they are a load on the alternator as well.

If you never play with the key off, IMPO the best course of action for high current draw is a healthy alternator followed by one or two high end batteries, and a couple farads of capacitance right at the amps.

[Fishchris]

I like the sound of all that, except how about 4 "low end batteries" ? 🙂 Lol

Seriously, I love these things.... Group 65's for $49 ! Four of these things will blow ANY single high end battery out of the water.... For less money.

https://www.walmart.com/ip/EverStart...ze-65/47308796

Oh btw, I almost never play the stereo without the truck running. On the rare occasion I do, I play it very low, and watch my voltage Gage, so I don't drop below 12 volts.



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[Serpentus]

Might want a high output alternator or even a second alternator.

[Fishchris]

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 ?

[Serpentus]

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.

[Fishchris]

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 🙂

[Serpentus]

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

[Millstonemike]

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.

[Fishchris]

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.
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[Psycoacoustics]

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

[devnull]

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.

[Millstonemike]

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.

[devnull]

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.

[Millstonemike]

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.