I need a new daily battery...sort of

[528hz 10+ year member]

I'm getting everything situation for the "big power" install and I need to get a new battery to replace my stock battery, which is too big and I need some of the space.

To, get to the point, here is my problem:

My car is Mercedes and they don't like to put CCA on the label, rather Ah (amp-hour). The stock battery is 100-amp-hour; I have 3 Batcap 2000s for the audio.

Now, can I get a battery that is less amp-hour than my stock 100 Ah? Does the fact that I have the 3 Batcaps compensate for any of the miniscule loss; say, if I get a 50 or 80 amp hour battery?

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[KyleBechtold 5,000+ posts]

is that a mercedes battery? im thinking they put the size they did for a reason and thats the cars stock demand.. i think you should try to keep the same if not bigger.. the batcaps should do the trick though because you have three and if you link em all together it should do fine

 

[528hz 10+ year member]

is that a mercedes battery? im thinking they put the size they did for a reason and thats the cars stock demand.. i think you should try to keep the same if not bigger.. the batcaps should do the trick though because you have three and if you link em all together it should do fine

Yes, it's a Mercedes battery. I know the factory put that on there for a reason, but my electrical is not factory now.

Each Batcap 2000 is 50 amp-hour. So if I have 3, does that equal 150 amp-hour in total?

This is basically just for a starter, but the main questions are can I get a slightly smaller one and be OK, and does the fact that the Batcaps are there compensate at all?

 

[loopkiller 10+ year member]

Your stock battery being rated at 100aH is an indicator that it is a pretty strong battery. Most Group 31 AGM batteries are around 125aH, so that is a pretty hefty battery. I would not take that battery out if I were you. The stock battery = 2 of your 2000!

 

[528hz 10+ year member]

Your stock battery being rated at 100aH is an indicator that it is a pretty strong battery. Most Group 31 AGM batteries are around 125aH, so that is a pretty hefty battery. I would not take that battery out if I were you. The stock battery = 2 of your 2000!

Wrong. 2 Batcaps are not 1 of my batteries. Yeah the Batcaps have a lesser Ah rating, but the CCA on one Batcap 2000 is 3 times that of my stock battery (600 CCA). CCA is what really is important in the grand scheme of things. Not Ah.

After further reading up a few things last night, amp-hour is defined as the maximum sustained amperage drawn from a fully charged battery over a certain time period to a point where the battery is at 100% DOD (depth of discharge), for or dead.

All this tells you is the how long the battery will run "by itself" before it's dead and how many amps it will put out in that given period of time. This is with NO alternator on it, just the battery.

 

[audiolife 5,000+ posts]

Depth of discharge on a 100 ah battery would less than it would be on a smaller battery. 1500 cycles @30% discharge would be somewhere around 13-20% discharge on the larger battery. CCA is also a spec that is 30 seconds long ran down to 7.2 volts (often not staying above 10 volts for even 1 second).

 

[528hz 10+ year member]

There you are audiolife. I was hoping you would chime in.

So, say I get a battery to replace my stocker that is between 475-600 CCA, and 80 plus Ah rating. I would be OK with that, right?

 

[Rashaddd 5,000+ posts]

Wrong. 2 Batcaps are not 1 of my batteries. Yeah the Batcaps have a lesser Ah rating, but the CCA on one Batcap 2000 is 3 times that of my stock battery (600 CCA). CCA is what really is important in the grand scheme of things. Not Ah.
After further reading up a few things last night, amp-hour is defined as the maximum sustained amperage drawn from a fully charged battery over a certain time period to a point where the battery is at 100% DOD (depth of discharge), for or dead.

All this tells you is the how long the battery will run "by itself" before it's dead and how many amps it will put on in that given period of time. This is with NO alternator on it, just the battery.

This depends on whether you have a big enough alt or not...

If you are trying to pull 500 amps of power with a 100amp charging system, you better have a lot of reserve capacity. If you are trying to pull 100 amps of power with a 300 amp charging system, you pretty much just need enough cranking amps to start the car and maybe a little extra capacity, just to be safe.

 

[infamous_e46 5,000+ posts]

Your battery is probably like my huge bmw battery.....d*mn near the size of a group 31 and has 2 indentations where the power and ground go ???

I wouldn't go smaller and autozone has a gold version that is strong as hell

 

[528hz 10+ year member]

This depends on whether you have a big enough alt or not...
If you are trying to pull 500 amps of power with a 100amp charging system, you better have a lot of reserve capacity. If you are trying to pull 100 amps of power with a 300 amp charging system, you pretty much just need enough cranking amps to start the car and maybe a little extra capacity, just to be safe.

That was my raionale on this too. I think my reserve is more than sufficient, and luckily I think I can get by with my 150a alt, 3 Batcap 2000s, and let's say a DieHard Gold that's 80 Ah or higher, and 575 CCA.

 

[goodguy8705 10+ year member]

Just curious, how many watts RMS are you running?

 

[528hz 10+ year member]

Your battery is probably like my huge bmw battery.....d*mn near the size of a group 31 and has 2 indentations where the power and ground go ???

I wouldn't go smaller and autozone has a gold version that is strong as hell

Yep!

Goddamm Germans! They need to at least put the CCA rating on 'em.

Have you switched yours out?

 

[528hz 10+ year member]

Just curious, how many watts RMS are you running?

Total, about 4500.

 

[loopkiller 10+ year member]

Wrong. 2 Batcaps are not 1 of my batteries. Yeah the Batcaps have a lesser Ah rating, but the CCA on one Batcap 2000 is 3 times that of my stock battery (600 CCA). CCA is what really is important in the grand scheme of things. Not Ah.
After further reading up a few things last night, amp-hour is defined as the maximum sustained amperage drawn from a fully charged battery over a certain time period to a point where the battery is at 100% DOD (depth of discharge), for or dead.

All this tells you is the how long the battery will run "by itself" before it's dead and how many amps it will put out in that given period of time. This is with NO alternator on it, just the battery.

I would love to know how the CA and CCA numbers you give equate to car audio power. Please enlighten us.

Let me give you a little hint... NOTHING!

CA and CCA are measurements of how much amperage a battery can provide for 30 seconds with the battery staying above 7.2v. Do your amps run at 7.2v? I have never seen any that do.

Now let's look at the aH rating. That would give you some indication as to how long you could run your audio system. It is not easy to do an exact measurement of time, but it is a good apples to apples comparison.

So when your stock battery has an 100 aH rating and the Batcap 2000 has a 50 aH rating, the stock battery could play your music for twice as long as one 2000, or the same as two 2000.

Now the aH test is conducted without any charging system (alternator) but the aH rating still applies even when you have a charging system present. If your audio load is a constant 200a draw and your charging system can only provide 160a, then the remaining 40a of current will be provided by your battery.

Now that 40a load will drain one 2000 much faster than the stock battery and we know this because of the aH rating.

 

[audiolife 5,000+ posts]

There you are audiolife. I was hoping you would chime in.
So, say I get a battery to replace my stocker that is between 475-600 CCA, and 80 plus Ah rating. I would be OK with that, right?

Depends on what you are doing. If its just starting the car and helping with the car or doing audio..both are totally different. If the back batteries are isolated from the front then it wouldn't matter too much as long as the battery up front starts the car and provides the back up the alt needs to run the car and that it can be efficiently charged by the car. There is a whole wide range to go by but rather than burst numbers and specs that are derived from situations you can't or won't use for your application its a good idea to go off what your system MAY need. Are your amps ever going to draw 600 amps from each battery? What is the potential current differences between what your alt puts out and what your system and car would actually ask for? No battery can charge as fast as it can discharge, a capacitor can't even do that, if it could it would be the most efficient super cap ever lol. By that time though we would be talking super conductors which really wouldn't apply to what is out there in cars or car audio.