Charging AGM Battery

I travel in my truck a lot so I usually drive about 1-3 hours with my radio up (80%) Volume. This is my Equipment right now Lanzar OPTI500X2 http://www......com/item_42353_Lanzar-OPTI500X2.html?gclid=CPCP3K6W1K4CFY1R7AodPgsGdA I have this running @ 2ohms each channel 750Watts x 2. ( four internal 40amp fuses) HiFonics BXI2408D http://www......com/item_24052_Hifonics-Brutus-BXi-2408D-BXi2408D-R-B.html Running @ 0.5ohms, Bench tested at car shop to a solid read at about 2650 Watts so I say 2500Wrms. (one external 200amp fuse required) Rockford Fosgate T3002 http://www......com/item_7540_Rockford-Fosgate-Power-T3002.html Running @ 2.66 Ohms and its "Actual rating" from the rockford birthsheet @ 4 ohms 163watts x 2, and @ 2ohms 278watts x 2. (two internal 40amp fuse) So I have about 4500Wrms. 440AMPS worth of amplifier fuses My Voltage never drops below 13.3v, the alt charges to 14.2v. My RPS brand standby batteries are sitting as of LAST WEEK 13.1v, and my front battery that was going bad last year (the shuriken) is sitting at 12.7v. I haven't charged any of the batteries since I charged them last January iirc. SO I can say they are doing GREAT What do you think?I can't hear you!

Well it sounds like you don't need the batteries - they are barely being used. It seems that you have an alternator rated for at least 300A (or 2 x 250A or 2 x 160A etc) - somewhat more than your original 220A alternator. Is that correct? Pushing 2650 Watts or even 2500W RMS output with a 200A fuse is pushing fuse specs. Running at 80% (of power) should be ok provided it's at 14.2V, but not at 13.3V (80% of volume is even better.) But at full output, you're likely to replacing fuses relatively often. The shop test (if using a 200A fuse) was probably relatively short (15-30 minutes max) and maybe they used a higher voltage in their tests... Incidentally, 440A of fuses should be okay for ~5500W output @ 14.2V, or ~5150W @ 13.3V depending on the actual fuse specs. (That assumes a 110% overload won't blow them, though they will run very hot and fail quicker through thermal cycling. 120% overload is often a 1-hour fusing time.) Have you run the system without the extra batteries, or reduced the number and compared the effect? And did you ever find where that "100AH per 1kW" rule came from? (As I recall, it was essentially only floridaSPL that quoted such that rule, and without any battery type or size qualification etc.) As it stands, your system is not as originally proposed, hence the batteries are not being cycled etc etc.    But good to see that you alternator was upgraded - even to the 220A. I can't understand why people add batteries BEFORE upgrading the alternator.   (Then again, if they reckon put the batteries in the engine bay for extra capacity, they obviously have the money to spend on more batteries!)    Thanks! for responding. And may your ears last. Trust me, hearing grasshoppers 24/7 is a pain in the ears. Well, it's damned annoying anyhow.

yeah thats what I was explaining before, that I would not be draining the batteries by much. And no its the same alternator just added the 2 RPS batteries back in January. With the shuriken battery alone, I was dropping to 12.5v at 80% volume, and THAT was with only the rockford and Hifonics. Not with the 1500watt lanzar. And the 100ah per 1000 watts is only a rule of thumb. There's no cite for that. But thank you and If ANYTHING witht he batteries go wrong im coming to you first lol I can't hear you!

Yeah, and hence not using them anywhere near what was originally envisaged. If they were, my bet is they would not last long. (Under your original conditions, you would have had to recharge them externally after every use (else engined with audio down or off), not once a month.) But keep in mind that the 100AH rule is not a ROT - it is a rule that seems peculiar to floridaSPL only, though by now it will no doubt have spread. I could probably start an equivalent rule of 10AH per kW, or 1,000AH per kW, and double those for wet cells or gels. I still reckon it is a misquote or misunderstanding of the variously used 12V rule of "100A per kW" - ie, as a simple guestimate of current, or a design-safe estimate of load current, or an approximation for fuse (or cable) ratings and converting output power to input power currents (ie, assuming ~80% fuse or cable rating margin, or ~80% amp or equipment efficiency). But the 100AH per 1kW ROT has many more variable attached to it (eg, battery size, ESR, charge state, temperature, age). Just be careful if specifying standby batteries for audio and cyclic use. If they are truly needed and discharge regularly, they probably won't last long.    [ Getting back to your original "batteries are batteries" comment, they aren't. With some batteries being 1/10th the price of others, money hungry companies and misers like myself would be sure to use them. But trust me, cranking batteries used for solar (or vice versa) are unlikely to last long. And industrial UPS would be using ordinary batteries too (though some UPS batteries may only last 5-10 cycles, but they are more stable/reliable and smaller). A similar situation exists with ordinary domestic batteries - cheapies may last longer than alkaline, or as I found, those $5 Lithium 680+ AA & AAAs are far cheaper than using 20c-$2 substitutes in cameras. ] And as you are probably aware, if using low ESR AGMs with thumping hi-powered audio systems with higher than a few kW output, caps of 1F or more will probably extend the life of the AGMs considerably. (Wet cells do not suffet the same problem. As I oft write, AGMs may be capable of supplying high currents, but they don't like it.) That - apart from battery time lags (and ignoring surface charge) - is probably the only legitimate application for caps in quality audio systems.    FYI - I often refer people to Bill Darden's BatteryfFAQ - IMHO an excellent & well written reference - everyone should read at least 1. WHAT IS THE BOTTOM LINE AND TIPS?. It's a relative easy read considering the complexities with IMO the most useful section 9 being the only big section. I suggest downloading as per 9. HOW CAN I PRINT THIS FAQ?, and maybe checking every few months for the occasional update. But you should find that I write agrees with Bill, though that detail may not be so obvious. (And as I often lovingly write, he cleverly passes the paralleling of batteries to others, though again, BatteryFAQ does contain all the raw facts involved.)    Finally, thanks for your last comment. Though not quite the conclusive thread I was hoping for (I think you were lucky else fall short of the original design conditions - hence the importance of realistic normal operating conditions versus worst-case operating specs), I have noted your success as a future reference.    Besides, maybe those standby Shurikens are capable of much more - just as my 12 year old Yuasa 38AH UPS battery has survived years of cranking and auto use which - IMO - it shouldn't have. In fact based on a few experiences, my guess is that a Yuasa UXH100-12 or UXH110-12 (100AH or 110AH, 12V) is not only cheaper than the smaller ~70AH Optima equivalents, but will far outlast the Optimas. As to physical robustness, several months ago I dropped my current UXH38-12 about 1m (1 yard) onto concrete, hitting corner first - not edgewise of flatly. Even I was impressed - my first instinct was to run!! And I like dirt roads and speed up to "smooth out" holes, corrugations, and rebel against speed humps, so vibration & shock - at least for the UXH38 - seems not to be a problem. Anyhow, congrats and all the best. Let me know if the Shurikens fail "prematurely". And beware those grasshoppers, or occasional crickets or cicadas, or opera baritones and ringing that also get reported. (LOL - but as my serious tip.)    Oh well, yet another typical short reply... Cheers.

Nothing has happened to my amps or anything... but I finally understand what you're saying. Batteries are slow. People in car audio are being saved by batteries, we're just getting jipped for more money and its actually worse. Advertising is brain washing! LolI can't hear you!

What do you mean "Batteries are slow"? And how are you being jipped for more money? Have yours failed (I take it they haven't) or do you mean that they advertise that you need expensive batteries when your cheap ones work fine?

Well I'm basing that idea on a completely different topic. What are your thoughts on Capacitors, and do they have a place in car audio to you?I can't hear you!

It's better not mixing topics. The delay for a battery to change from charging to supplying is one thing, but it isn't meaningful without considering its surface charge and capacitance, nor comparing to the instantaneous amp output. As to wet cells being slower than AGM, or slower thru thinner cable... (That's supposed to be a joke.)     As a Rule of Thumb, capacitors for car audio belong in the bin along with brainwashing and money jips. If you want higher peak SPLs, do not use capacitors. (That's based on competitor's audio forum and elsewhere advice.) The only definite use for caps is in BIG audio systems where AGMs are used, and that's only to protect the AGM battery. That typically applies for systems of about 3kW (RMS!!) output with maybe only one adjacent battery - ie, it's not required if the AGM is remote or in the engine bay, or if there is more than one adjacent AGM (of sufficient capacity). (Scale that up for bigger systems.)

Well I just didn't want to start an entire thread on a question that is asked thousands of times a day. Do you just want me to start a new thread, because I have a debate/argument to kind of play devils advocate on this one. I can't hear you!

I am the devil. I am one of the few (or the only) on this site that advocates caps. But as a way of "holding up" voltage - FORGET IT (do the calcs!) - unless you cannot use an adjacent battery, or for headlights etc. Start a new thread, but search to see if you're repeating the same... And if you are getting your info from the guys that suggested batteries BEFORE the BIG-3 or upgrading the alt (to cover your amp output), then what can I say (I've already said... numerous times). If you don't believe me or this site, try Richard Clark's articles. But certainly, a new thread if you still have any doubts.