Charging AGM Battery

What's the reasoning behind that?I can't hear you!

No self discharge. The more you charge, the quicker the battery dies. And you have standby batteries - not cyclic. Keeping on float is different - that is ok.

http://www.batterystuff.com/tutorial_battery_gel_agm.html This site is saying that AGM Batteries are good for Bursts of amps. That sounds awfully close to high amp bursts of a subwoofer amplifier...?I can't hear you!

Yeah - and it says you can use standby AGMs as opposed to cyclic AGMs? I don't think so....! And it says "AGMs can supply bursts of power therefore they are designed for that"?   (The point being that for cranking, apart from a rare few, AGM manufacturers do NOT specify CA or CCA. Why is that?) Your link is a quick and general overview. It barely discusses charging. The link I gave you includes the points I made above and in your other thread, plus most else I have told you. Unfortunately your "theory" is entirely arse about - even starting from the "100AH per 1000W" which is an misquoted alternator/load rule - an telling people to use batteries when the alternator is the solution! (You need 100A of alternator per kW of load, NOR 100AH per kW of load!) If I am wrong, show me the source or reasoning of the "100AH" rule. Nobody has yet even stated reserve time!! PS:

rfhvhtoo wrote: AGM Batteries are good for Bursts of amps...

And YOU know why AGM batteries are good for delivering HIGH currents don't you?

Wow, is really all I have to say so far. I've had the Batteries for about 4 months now. Allow me to describe them, The first 3 months I sold my system to start a rebuild so they sat in(side) my truck, with weather down to 20 Degrees throughout the winter nights for 2 of the 3 months. With florida having unpredictable weather there has been many days of it being +90 Degrees and they sat at 13v the entire time (they are stand by batteries so we kind of expect that right?). I charged the Batteries once in December as I posted before. I put in a experimental system about a month ago that I wanted to practice my box building with (some old 10 inch speakers i had). The box is great I might add for my first bandpass enclosure. I have the same Hifonics running @ 2ohms suppose to have approx. 1600wrms and my Volt meter (and DMM) RARELY drops below 13.5v during play. The only times I've seen it drop that low is when there is a High(er) Frequency bass note plays SUDDENLY (at high volume) while the alternator is at idle (parked) and not charging as High at the moment, but it quickly recovers DURING the play of the 50-100hz frequency and will sustain back to 14.0v. This is with 2 of the ($65) 140AH Batteries and the 100AH Battery in the Engine bay, 1 300amp $18 Relay and 220amp HO Alternator . My theory on it so far is, The Batteries will not go bad, or discharge, as fast as you think simply because the goal is to NOT Discharge the batteries as much as possible. But instead to have more batteries So the current draw will be less taken from each battery instead of all from one battery. And with the alternator charging the batteries up to 14.0-14.2 are they being Discharged at all? especially if the current draw is below the rating of the alt? I can't hear you!

I love your theory. It sounds on par with floridaspl's level of expertise. And their logic. My theory is that your goal to "... NOT Discharge the batteries as much as possible" is irrelevant. It is the implementation and reality that counts. Besides, floridaspl say you MUST have those batteries, therefore they are being used and discharged. Right?     Another theory is that you are not loading them (hence not cycled) as evidenced by your voltage readings.     I hypothesise that you are also not loading anywhere near the 4kW we were discussing and designing based on your criterion. The storage and the temperatures you describe should have no effect on them. Their voltage should only drop by (say) 0.1V after a few months. Your reasoning for more batteries to de-stress the batteries is sound (pun intended), but what choice do you have...?! You did as many "audio" forums advise and got more batteries instead of a copious alternator. What can I say? (See NOTE.) But all this battery stuff is total crap anyway. To quote a floridaspl 8,000 poster (with that count I assume they have knowledge?), they "lost maybe 2 tenths from 13.8 to 11.9 v"... - ie, they only lost ~20% of power from 13.8V to 11.9V. (It's over 1/4 or 25% in reality, but who cares?) And another reckons "... a drop in voltage means no difference in output..." which is true if amps were constant power loads like most SMPS equipment. However, from the specs for your and others amps, they are resistive devices - their power output is proportional to the input voltage (squared). [ BTW - I love how the latter later wrote "A drop in voltage would only create a larger draw of amps. The problem is you can't supply the larger draw of amps and this is why you have a loss in output...". Oh my dear Poos & LOLs - that cracked me up! But they were a mere sub-400 poster after all. And that stuff is very confusing to the inexperienced, and still difficult to explain... ]    NOTE - the above is what I can say. Have your theories, but maybe keep them off-site - maybe on floridaspl where they belong for now. Come back when you have solid experience to report - there is no use arguing beliefs against reality unless you want retorts like "I wrote you so..... MANY times!" (Like others I usually refrain. Certainly in my case it's hard enough controlling the fits of laughter. Or - alternatoratively - the tears.) Meanwhile I wonder if floridaspl figured out whether a cap stores current or voltage? And whether a cap's voltage is ever higher than the wiring & equipment it is connected too - they certainly make it sound like it is - but it is a sound forum!). (I was surprised to read that only big caps hold their "zap"!)     But I suppose audio forums like floridaspl will continue to not only counter the experience and logic of others, but also contradict their own writings and logic. (Here we have differing opinions and priorities/tacks but technical contradiction are rare.) Who sponsors them? Meanwhile floridaspl post counts mount up by people that repeat what managers or experts from elsewhere claim - except that what was said is misquoted or twisted out of context (if it ever was said LOL). It's like sharks being afraid of dolphins and AGMs being ok to supply big current. But lots of medicos, battery suppliers, and other support people make money off those that can't know any better. Being into Quality (more so Demming than Darwin) doesn't mean I should risk livlihoods.    I guess you still don't know where the 100AH per kW comes from? If floridaspl had the experience to back it up, they'd be using caps instead. Or are they referring to battery reserve time? I wonder what BigBoi would say? But maybe others haven't been exposed to REALLY big systems and thence know why a cap is needed... I still reckon the 100AH/kW is some twit's misunderstanding of the 100A for 1kW rule. Honestly, if they meant 100AH per 1kW, they would be specifying Farads! (Or did I kill that one too by asking up-time?) And you don't know the difference between a stand-by battery and a cyclic battery??? With luck I'll see you about one month after you start using your system when mobile with at least 1kW output; and after recharging your extra batteries once a month at home. Thanks for the monthly update, but until you complete the system, a simple "still progressing" might be shorter.

rfhvhtoo wrote: ...13v the entire time (they are stand by batteries so we kind of expect that right?)

WRONG! (ie - wrong reason.)

rfhvhtoo wrote: And with the alternator charging the batteries up to 14.0-14.2 are they being Discharged at all? especially if the current draw is below the rating of the alt?

LOL! Should I even bother answering? Or can you explain why an alternator would be up around 14V if it can't supply the current?

rfhvhtoo - still progressing? Or have the batteries been subject to the 4kW RMS amp(s) for reasonable bursts and runs?

oldspark wrote: rfhvhtoo - still progressing? Or have the batteries been subject to the 4kW RMS amp(s) for reasonable bursts and runs?

The two are doing really good actually, with the 220amp alt, 2-140ah & 1-100ah in the engine bay the voltage does not drop below 13.3v at idle on the stinger voltmeter. My DMM reads 13.5v but I like to under estimate, even if it is with the worse device (stinger). The 2 in the back are still sitting at 13.1v as usual, but my front battery has been going bad since before I had the new batteries. so Its still sitting at 12.7v. I was thinking about just getting a new acid lead battery for the engine bay since I have the Relay between the engine and the 2 in the back. For one it's cheaper, and all I need it to do is really start the truck, and be a good battery. no bad reports at all. if there's some testing you want me to do let me know! :) and the voltage tests were on Music and Bass tones to set gains on the Hifonics BXI2408D. I have it at 0.5ohms. efficiency of MAYBE 50-60%? From the bench tests I've seen the efficiency is less than 65% at 1ohm on these amps. So it should be pushing around 2800-3000watts at that efficiency. which is About a 400Amp current draw.I can't hear you!

Still below the 4kW.... How much running on just the batteries alone? Yep - stick to wet for cranking, much longer life and better suited. And when charging, parallel AGMs with wet etc won't matter. And with the voltage drop you mentioned (if accurate), a low ESR front battery is wasted.

rfhvhtoo - How now? Still progressing? Have the batteries been subject to your original 4kW RMS load for reasonable bursts and runs, and how have they fared? Do you top the batteries up once a months, or do you need to after every use? If you haven't got the 4kW RMS load installed and use it on a regular basis, there is not much point responding. Although if your standby batteries failed (or not) - especially if in cyclic use (with say 20% discharge or more) - I'm interested an your reply.