agm compared

[SMS 10+ year member]

i have a kinetik hc1800 and a beefy 220a alt- big 3 under the hood. in the back i have a shuriken 45ah that really does nothing.

my question; would i notice a difference if i added another hc1800 81ah vs a 80ah XS battery. why is XS so much better? i can get the 1800 for $180.

thanks for any advice

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[Silverado SS 10+ year member]

What amp?

 

[SMS 10+ year member]

right know im running a IA 20.1 but in the fall i plan to get another and strap them 1ohm each- so around 4k before rise- really 2.5-maybe 3k

 

[CRXBMPN 5,000+ posts]

i'd think the ideal way to do this is to run the exact same batteries so the resistance and other battery important things are kept the same throughout, if you can.

 

[mylows10 5,000+ posts]

As long as all the batts are all agm you should be fine usually the rule if thumb is whatever fits under the wood and as big as you can by the amps

 

[Side Show 10+ year member]

get the same batterys = less issues

 

[smoka 10+ year member]

i have a kinetik hc1800 and a beefy 220a alt- big 3 under the hood. in the back i have a shuriken 45ah that really does nothing. my question; would i notice a difference if i added another hc1800 81ah vs a 80ah XS battery. why is XS so much better? i can get the 1800 for $180.

thanks for any advice

1. You should get the same type batts when they are both the same age. Since you have a used one it will be not be the same as a new one. Batts slowly lose capacity over its life. Best case sell your old batt since there are tons of suckers on this forum that buy old used batts. Then you can buy 2 of the same size and age, this will give you the best results to try to get 100% life of your new batts. Or keep the old one and just get the 2nd new one, just know that you will probably only get 50-75% of life out of it by mixing batts.

2. Its hard to compare batts in general. The AH measurement is not great for car audio. A 100ah batt means that it discharges 5a over 20hrs. 5a is nothing compared to what an audio system is pulling. Worst part is that the output is not linear depending on the batt design. Easier to copy/paste then to try to explain it

However, it's very important to know that the total time of discharge and load applied is not a linear relationship. As your load increases, your realized capacity decreases. This means if you discharged that same 100 AH battery by a 100 amp load, it will not give you one hour of runtime. On the contrary, the perceived capacity of the battery will be that of 64 Amp Hours.

So your audio system can pull 300a+ from your batt but we are using 5a draw to measure how good the batt is? IMHO I always thought that RC is a better measurement for a car audio batt. RC is a 25a load over the time it takes for the batt to get to 10.5v.

If it comes down to two similar batts, go by total weight. Lead is heavy and generally the more lead the higher capacity (and more expensive).