Running 10k watts. Question about batteries.

[Inetba]

First off, 1996 Honda accord station wagon.

329 amp hairpin alternator.

Big 3 is completed with 0 gauge wire from sky high.

3400 XS battery up front.

I am keeping the air conditioning. Could possibly consider cutting a hole in the hood to fit a 2nd alternator *in the future* but not now.

What i am trying to learn, is how to figure out how many batteries I need to sustain X voltage. I know about amp hours. I know my alternator came with paperwork saying it is rated at 4,890 watts. What I don't know, is how to figure out how many batteries I need once I go above that 4,890 watts.

How do I figure out how many batteries I need for 6k watts? 10k? 16k? 20k?

I know I could just throw 30 tractor batteries at it, I don't want a hand out. I want to learn the math behind figuring out how many batteries I will need.

Any help is greatly appreciated.

[ChevyBoy95]

Generally 100a of alt per 2000w and 1 battery (group 31) per 1000-1500w is a good rule of thumb.

With your single 325a alt, i would personally have like 8-10 group 31's, if you had dual alts (like 2 270s or bigger), 6-8 batteries.

If you had say 500a of alt (5 x 2000 = 10000), then you could go with 10000/1500 = 6-7 batteries.... since you have say 300a ( 3 x 2000= 6000), I would do the 6-7 + 2 batteries to cover the lower alt amperage.

This rule of thumb will hold ~13v (in my case 12.8-13.2)

[Quintine]

Work out the actual power draw you will need, how long you will need it to draw for.

So say u run a 10k amp and its at 80% efficiency.

And lets say u wanna run a sine wave for... 15 mins? (Imo a plenty brutal enough benchmark to work from)

Watts needed from batteries would be calculated something like (10000 / 0. 8 - 4000 = 8500
That would be Amp draw - alternater output (With a bit leftover for hte car)

Then take that 8500 watts and divide by 10.5 (Batteries being near flat) meaning u should need about 810 Amps of extra power available from your batteries.

Depending on the battery AH output and how long they are rated to do said output you can workout how many batteries you will need, and hopefully have some wiggle room.

Edit: To work out AH

AH = Amps/Time (So 810/.25 for a 15 minute draw)

Then just match up the AH rating for the batteries you want.

202AH Would be:

2xD3100's

3xD2700's

3xD4900's

14xD375's

Also note, I would put this as a minimum reasonable amount of batteries to run alongside a good battery up front.

[Inetba]

Awesome! Thank you guys so much!

Hopefully if someone has a similar question in the future, this post will help them.