Charging AGM Battery

alright I've been doing TONS and TONS of research looking at different batteries, opinions, isolators, wiring, how much space in my vehicle. I've had this page up for the past 4 days now just comparing and contrasting taking this info into my decisions and plans. And what I want to do is get the charger and 4 RPS Batteries, they are 140ah and the shop selling them for 65$ each. I Say getting these is better than 4000 watts rms on one battery. I Also want to get an isolator between The Shuriken battery (in the engine bay) and those 4 in the back. I'm being told a rule of thumb is 100ah per 1000 watts rms. I'm going to only get 2 at first for 130$ and see how my alternator handles it with an isolator. My only problems is i've been hearing quite a bit about the reliability of isolators. are there isolators that never allows the front battery to be used with the rear batteries even when the car is turned on? Also about the voltage drop they may cause up to 0.6volts with only car turned on & alternator charging. so it would be 14.4 in front, 13.8 in back. do you know of any isolators that can prove that wrong with tis high current type of system?I can't hear you!

Forget the isolators with ~0.6V voltage drops. They are diode isolators and are generally pretty stupid and wasteful. Do you have a charge light? If so, you just need a relay. That relay can drive other inter-battery isolators.    The 100A per 1000W is simply P=VI or Watts - Volts x Amps where V is rounded down to 10V - often used for input current for output power (the drop to 10V allows for ~20%-30% inefficiency from input to output in amps and PSUs). What are RPS batteries? Remote Power System? I can't advise on batteries because you have not provided any reserve time info, but I presume you will get the 500A alternator(s) first? But 4 batteries (paralleled) is a lot... I presume you will isolate them when not being used? And $65 for a 140AH (12V) battery seems very cheap... Are they AGM? Deep cycle?

He says quote "They are around 140ah IIRC" im guessing the RC at the end is Reserve Capacity. And no I'm only going to run the 220amp alternator I already have. Thats why I want to only get 2 of the 140ah battery, to see how the single alternator handles it. These are the type im talking about, just got this pic off of google images. I can't hear you!

Why did you chose 2 140AH batteries, and not 1 or 4? PS - based on the only data I can find which is the HRS12-270FR battery (RPS no longer exist) which look the same as your pic... It is a 75AH battery. It is a UPS battery with a 10 year design life. That means that in your situation, it may last a few weeks. (UPS batteries are not subject to daily discharges. Many may only see 6 monthly discharges during testing. Some survive only 10 cycles.) Based on HRS12-270FR data, if all your 220A alternator goes to your amp, 2 batteries will last about 20 minutes (if that - I do not trust their specs; I'd estimate ~10-15 minutes). You then need to charge them ASAP - the longer you wait, the more they deteriorate. And I have no idea what you mean by "...to see how the single alternator handles it". A 220A alternator handling a 500A load? It doesn't. End of story. Its voltage drops to the battery voltage and the batteries discharge at a rate of ~300A (which increases as the voltage drops since amp are "constant power" loads - eg, 1680W input is 120A@14V or 140A@12V).

These kinds of batteries are being used daily in the car audio industry because they are MUCH cheaper. Brands like C&D technologies (Liberty 1000's) http://www.cdstandbypower.com/product/battery/vrla/lib1000_12_373.html That specific one I've actually heard A LOT about, many people are looking for these to use but its just hard to get your hands on them. And they are taking these over kinetik, shuriken, yellow tops, mostly i think because of price and you can get a lot of them for the same cost. If I wanted to get That size of battery in the name brands, im looking at $1000+ which makes 80% of people say ill take my chances with he $65 batteries first. I'm not saying they'll work perfectly. I'm actually not saying they'll work at all but $1000 just isn't going to be in the books for a while. I'm going with 2 because (around 280ah) 1 battery is not big enough for my setup since im trying to completely isolate the front battery from the back so it does not die sooner, or should I take advantage of that battery as well and hook them parallel no iso? And with the 100ah rule of thumb that would mean I need about 400ah in all. there's a $3000 way to put dual alternators in my truck but as I said before it's just not happening at this moment. Trust me i've looked at all the better ways or feeding my system with power and needing the least amount of batteries as possible. Thats why I only bought 1 last year and not 4 at once. Thank goodness i didnt though because i'd rather try it with these cheap 40-65$ batteries before dropping $1000 on 2 XS powermaster 3100's. But also that is the point of the many batteries is to basically allow your batteries to take MOST of the load. At the car shows like the world finals in Daytona Beach, You see their volt-meter sitting around 12.5-12.9v while their music is playing, because the 4-12 batteries they have in the back are handling most of the load(right?). instead of 1 like my truck is. Many of them still have STOCK alternators which surprises me too. But Do you really think the car audio batteries are THAT MUCH better though? Thank these cellphone tower batteries (basically). Here's a manual to the Liberty-1000's (Model# LS 12-100) http://www.cdstandbypower.com/product/battery/vrla/pdf/rs_990.pdf I can't hear you!

Now we are getting somewhere... You are misinterpreting what I am writing, and I suspect lots more.... Firstly:

rfhvhtoo wrote: And with the 100ah rule of thumb that would mean I need about 400ah in all.

What 100AH ROT? Do you mean the "100A per 1000W"? How longer will those 2 batteries last at full output with the alternator charging at full output - or, how long with & without the alternator? The rest of what you just wrote is totally consistent with what I have been writing etc. It is nothing new. BTW - I won't touch Optima either. Not that I'd use an AGM as a cranker (says me with my $650 replacement list price 40AH AGM cranker LOL!).

I wasn't gonna comment, but with afterthought...

rfhvhtoo wrote: But Do you really think the car audio batteries are THAT MUCH better though? Thank these cellphone tower batteries (basically)...

LOL! YOU will once you and the others see how long they last! They are Stand-By batteries...! Maybe they will last, but I doubt it. I'm 98% confident that by the end of one year, you'll find it would have been A LOT cheaper buying those other batteries. Not that this changes my last reply's question(s) to you (especially what 100AH rule?), but this is firstly a warning.     Secondly, if other audio buffs are buying those batteries because they "are the same but cheaper", I think I'll be laughing almost as hard as at the cap brigade - but that will take time to show. (I bet these guys use caps top eh?) I dislike prevention when it prevents a good laugh (and stops money transference).    (Not!) PS - Not even Liberty's warranty applies in your case. Don't be suckered into buying one - when it fails, it will NOT be replaced etc.

lol yes see it's that MAYBE thats getting me! And honestly im glad (and lucky lol) we're on the same track, even if i didn't fully understand you at first. Thats just a ROT of a car audio forum in Florida to have 100 Amp hours per 1000watts (not dealing with number of batteries or actually any other specs about the battery at all). And since i dont know how deep into car audio you are, i mean i know you can tell me everything about it looking at specifications and everything and easily crush many arguments i have..lol but when talking about batteries everything is about the amp-hours. and I have 2500 watts rms at the moment. so about 250 amp-hours are needed in my situation I've heard many of their cars and they sound amazing and voltage drops are too good to be true so im gonna go with that ROT until i myself can prove it wrong. he is sayinf 130$ for Basically 270 Amp Hours.. I mean thats .50 cents an amp hour! lol I should atleast try it. I'm a big believer in experienced opinions (or that's just a great excuse to try it lol). I've also noticed that you write 100A, while im saying 100AH. That could be in our misinterpretations as well. OR just how you write it im not sure. Now for some questions... Do I need fuses between each battery? I'll have 3 in all with an isolator up front. Should I do a light charge on them before using? I'm also going to check the voltage before I purchase them. what should it be around? Thanks again! I can't hear you!

The rule is 100A per 1000W, it is NOT 100AH per 1000W!!! If the Florida Forum is getting that confused, they need to get their servers out of the sun! The Amp rule has NOTHING to do with Amp-Hours. The 100A for 1000W rule is from P=VI where V=10V as I explained earlier. THAT has NOTHING to do with 100AH for 1000W etc. If you get a 250AH battery on your load, it will last a few minutes as I explained above. Hence why I keep asking you how long you think it will last, or how long you want (reserve time) etc. Using your logic, you don't want two batteries - you want one HUNDRED batteries. A 100AH battery will supply 5A for 20 hours. It will supply 100A for up to 30 minutes (and if taken to ~10V, will last maybe one year if recharged immediately; though your standby battery probably won't last a month). You need TWENTY of those 100AH batteries to last 20 hours at 100A. You need ONE HUNDRED of them to supply your 500A for 20 hours. (Then you'll want a 1,000 Amp charger quicksmart!) That assumes a C20 rate, but since you haven't mentioned what "time" you require.... You were getting 500A of alternator to handle your load. Now you are not getting that alternator. Hence you will be relying on batteries to provide the shortfall. The question(s) then becomes how will you recharge them? And how long you you want them to last wrt reserve time. As to how long the batteries last life-wise (as in weeks or years) depends on how you cycle them (how often, to what depth at what rate, and how quick you recharge them) and what battery(s) you buy. Don't think that people haven't though of cheaper batteries before. If a Yuasa NP38-12 could be used in place of my UXH38-12, it would cost under $200 per battery instead of over $600. But the NP might last a few months if that. The UXH is 10 years old and I have already been using for over a year. If you do want to try it because you believe in "experienced options" provided they are your own, go ahead and report back how it goes compared to my prediction. If you believe in others experience, let me know. It seems the Florida Forum is using you as their guinea pig. (I was going to write "sucker for their experience".) Or are they suggesting these standby-batteries from their experience? LOL! Like I said, not even the warranty will apply in your case. But I guess it is a cheap experiment (depending on what happens when they fail). And yes - all battery-to-battery interconnects are fused at EACH end. (Except where physically secure or short.) Are you using one relay/isolator per battery? And what sized isolators/relays and fuses are you using?

Okayim going to reply to the rest of that but I'm on my cellphone and I kind of need that "what should the float voltage be around" question pretty lol like hours, basically I'm wondering where should I be scared?I can't hear you!