2 batteries in a prius

sry i typed this up in notepad and just copied and pasted you siad:Whilst your friend translates for you, ask him how ESR effects whether you need a relay or not (to isolate parallel batteries). Then ask at what stage of discharge does a low ESR battery need the relay? EG - as an AGM becomes discharged, its ESR increases and is eventually bigger than that of a fully charged wet cell (of similar capacity) which - apparently - required a relay. And for what sizes? EG - a wet cell 150AH has a lower ESR than a 35AH-75AH AGM - so do they require relays? My final point of batteryconfusion is, if you don't need relays for paralleled low-ESR batteries, why is it recommended to isolated them to prevent thermal runaway which is something exhibited by AGM batteries (low ESR) and not wet cells (which typically have twice the ESR or same capacity AGMs)?     My final confusion is how can someone that knows how to connect an isolating relay to an alternator NOT KNOW how to connect it to an on-off switch - eg, an amp or HU? I can understand the reverse situation! my response: i talked to my friend and he told me that he was taught that relays/isolaters arent needed unless your runnning like competition level audio. he said he asked a fellow installer and he had a different opinion, so he aint sure. he has been insalling for 10 years and i have only been installing since 5 years. but i was taught to use relays/isolators and only knew to hook up form the alternator to the relay/isolator so thats where i was lost. i asked him to take a look at what you wrote but he said that he honestly dont as much about isolators as u because he wasnt taught that much about them. he is who got me installing so i always go to him with things but for once he dont kno something. he said if it was him he would just parallel the batteries, he said he wouldnt kno how to hook up a isolator in the prius as there isnt an alternator, thats the only way he knows how to hook up one. i told him you said it can be hooked up by tapping into the on button and he didnt really respond to that. so im not sure if he is one to be asking abou this obviously your knowledge is much greater about this stuff. you said:   And what starts the engine - a push start - you can't start it is the 240V bank is flat? my response: its my understanding that the battery starts the prius eletric motor and once the battery gets low the gas engine kicks in and recharges the battery. from what i have read you can let the car run for 2 days or until u run out of gas. because the car will keep switching from electric to gas and will never drain the battery. the amp is 1000 watts rms. but i will be buying a 1200watt rms amp as soon as it comes out to power my 1500w rms sub. i installed it in the prius and minus the headlights and all the interior lights flickering it was fine. but i cant have the flickering and thats one of the reasons im installing the aux battery honestly not sure how to set up a total loss system plus i just paid 350 for new batteries. i cant afford to buy another one. i have the kinetik hc1400 as my main battery and im still waiting on the kinetik hc1800 for my aux battery. i dont plan on adding a cap with the aux battery as i dont see the point in doing that the amp should get the power just fine from the battery (atleast from what i know about batteries and caps.) i had a battery and cap in my old set up but mainly just for the voltage meter (i got the cap for free frmo the shop i worked at) my friend said that all this deff made him realize he has alot more to learn lol i already kno i have alot to learn. he mecp certified and still installs for a shop. i have never taken the mecp cert test and after the old shop shut down i just do installs for myself and fam and a few here and there on the side. once i get the hc1800 i would like to get this all installed. i just finshed the amp rack and just waiting to figure this out so i can get it hooked up. so where im at now is..... clueless lol. seriously though im lost as to what i should do. i want the best possible set up for what i have and what im doing with it. deff need your guidence as you seem to be a 12v god lol i appreciate all your help, once again. please let me know what u think. thanks

Cool! Tell your friend I admire him - not because he reckons I know more (hey - I can be wrong! But that's why I ask....), but because he stated the scenario or limitations of his info. Also that someone else has a different opinion.... (Isn't there always? ) He & you have done as we all have - or I have anyhow: Accept something until that extra bit of info or contradiction comes along. He/you may have some "high current demand" reason for using relays. I come at it from a totally different perspective - thou shalt not parallel batteries... based on the reasons I gave (eg, doubling (self) failure rate; one goes & they both/all go; etc).    But that paralleling when charging is fine - otherwise they should be identical batteries with symmetrical charge & discharge (ie, diagonal power exits; equal +ve & -ve interconnects). The ESR and capacity has NOTHING to do with it - it is simply reliability and a max-life consideration. [ I don't think anyone denies that when paralleling TWO identical batteries, the batteries will fail at DOUBLE the rate of a single battery (wrt to "self-fail rate" ie, manufacturing defects or (statistical?) sudden collapse). And if unmatched, well the failure rate is equal to double the worst failure rate. EG - 2 Optima batteries with MTBF (Mean Time Between Failures) of 3 years. Two individually still have 3 years MTBF which means on average, 1 will fail every 1.5 years. BUT, 2 in parallel with 3 year MTBF likewise means one fails every 1.5 years, but when it does, it kills the other battery. Hence you lose TWO batteries in 1.5 years, not in 3 years. (I know that is confusing. And I don't think MTBF is the correct "failure" figure to use - I am merely trying to illustrate the principle. Keep in mind with batteries, if one goes, the others in parallel also go. (In series, if one goes, the others suffer. Not too bad for 432V UPS series strings, but not good for 24V series strings etc.) ] Reliability - yech! The only reliable thing here is my guaranteed rambling! And not that I understand the "requirement for relays" for BIG installations - unless it is simply that BIG batteries are too dangerous to allow to fail in parallel. Alas I have seen thermal runaways in 12V 35AH bands and heard of almost red hot smaller Optima AGMs (way below 75AH). [Ok red-hot is exaggeration, but the dude figured out he had 2 collapsed cells in his "NEW" Optima battery (as I had suggested from thread reply #1) when he felt the heat in his boot (trunk). It was sinking the output of his new 75A alternator (formerly a 45A alternator)!] I would have thought BIG current demand meant avoidance of relays - ie, every terminal, contact, joint, fuse means added resistance (and unreliability). But audio forums puzzle the pss out of me. Audio amps are bad enough - ytf do they use 12V transmission when amps internally boost to much higher voltages? (Yes - I know - save that Product Release for the neXtGen when caps are dead and people get wise.) And use 1 OHM speakers? (I even saw one forum that said the lower the Ohmage, the "better" the speaker & response.) Why not use what the big boys use (PAs, Marshall, Fender etc) - 4, 8, 16 Ohm whatever. The higher the speaker impedance the better from a power transmission POV - ie, lower currents for the same Wattage output.    IE - would you rather send 400A@12V for 4.1kW@1R, or 75A@64V for 4.1kW@1R, or 38A@128V for 4.1kW into 4 Ohm? The last requires 10% of the copper than at 12V for the same power losses. But such simple annoyances aside, why do audio forums write things like "batteries under the hood" because increased temperature means increased capacity? (Do they also increase the charge voltage to suit? And isn't it cheaper lifecycle-wise adding 20% to the battery capacity instead of replacing the "hot' batteries 4x to 8x more often?) And why do they constantly say "get bigger batteries" rather than a suitably sized alternator for street use? [ And don't think I haven't missed the SPL competition contradiction - many claim higher SPLs without caps, yet they still insist on BIG batteries, and low-ESR batteries at that. Don't they mean high-ESR batteries so they do NOT swamp the (reflected) voltage peaks? ] And whilst I don't expect audio forumers to be smart enough for dynamic cap & battery analysis (even that was too much for some on the12volt.com!), they seem too dumb to even mention that caps are used to help prevent the earky failure of AGM batteries! (Yes I know - AGMs supply BIG currents. And yet AGM manufacturers do NOT generally provide CCA & CA figures... how strange - isn't that their strength?)    Sorry ogjlbh21 & admired friend - this is not YOU - I am venting a few small (not!) frustrations. Or maybe you didn't notice? Hmmmm - or ? You two have already shown that you are ahead of THEM - you seek, and you are open minded. (Besides, did I say I can be wrong? Nah - I'm too arrogant amn't I) Break time - gotta hand up my washing. Maybe myself too if your are lucky. Back (all too) soon...

Rats! I'm back. 22:40 and I just hung the washing. Alas my neck was too slippery for the rope, and those wooden pegs just won't grip my Dumbo lobes. And I confess - though I may have been whining constantly, tonite is my first alcohol (wine) for probably 4 weeks. I wonder if - in MY case - alcohol releases inhibitions or exposes violence. Without reviewing the Prius "dimensioning" details (50A converter?)... As I see it, TWO issues: What is your "averaged" audio demand? - EG - 1200W RMS amp means ~120A input at full blast. Hence you need a "120A alternator" or charge capability to cover that. BUT - you won't be full blasting all the time, or much. (I presume?) Hence what is your average?    If HALF of full-blast volume, isn't that 300W RMS - ie 30A input? (0.5 volume means 0.5 x 0.5 power - 0.25 x 1200W = 300W? Now the audio guys should answer that one - it is fundumental. Alas all I remember is it's logarithmic, but I forget whether the deci-Bel means not exponential but 10log(dB) times my social security number times the speed of the next stock market crash.... ) Anyhow, do you start to see my point or madness? If under (say) 30A and the 400V-whatever to 12V converter handles 50A, then you can probably comfortably handle the audio load. Maybe even a 40A average (depending on headlights etc). If you average 45A or 50A etc or more, then you MAY have problems if the 12V battery reserve is NOT enough. Let's say your average is ok (eg, maybe 30A or 40A or less). That leaves TWO problems: (1) - when you boost the volume and exceed that average (eg, 100A for 1kW output), and... (2) - short bass thumps resulting in short high-current (peak) demand. Actually - both are the same; they vary only in duration. The first determines the battery size. How long do you want what over-current to last without excessively discharging the battery?    Hence you end up with a desired AH capacity. The second may be solved with the appropriate (large) battery size (and its ESR), but it's a combination of ESRs (resistances) between battery(s); alternators (dc-dc converter); and loads - ie, the amp, and lights etc. This has many solutions from caps (at lights; else maybe amps) to low ESR batteries (ditto - at lights, or amps or both!) and low or high impedance interconnections.... Normally I recommend batteries over caps - mainly because a $20 1.2AH or $35 7AH 12V AGM is cheaper than most 1F or 10F or 100F caps - and you might start a car off either battery, but rarely a cap! (IE - batts have far more stored energy.) But in otherwise single battery installations, caps are attractive because they are NOT a 2nd battery, hence no need (IMHO!) for the isolation of a "parallel battery". Granted - should the cap fail, it'll kill the battery, but how often do caps fail? And there is not the same magnitude of "parasitic" interaction of a battery-battery connection. Plus the old reason - caps can prevent or limit damage to AGM batteries. [ Author's note: Dear ogjlbh21 & admired friend, please remind me later to abuse or kill you. You have caused me to divulge some reasons for using caps. I am generally anti-cap and have prompted others to provide reasons for using them. And now YOU force me to provide this info to the enemy? Mark my words, you WILL pay! (Hopefully in kind to the next deserving wisdom seeker.) Sorry - I'm just venting again. Those morons will never read this anyhow! ] But I think I'll leave it here for now. Does what I write make sense? [ Oi! Read a few times. Discuss & brainstorm with your friend else the little person that answers me back. Re-read again. It is an iterative process (or it was for me!). To paraphrase certain musicians (Gillan et al) - you have to understand everything before understanding anything else. If unclear, ask. If ambiguous (who, me?), clarify. If considered wrong - fight, discuss, argue. (But don't flame - except in obvious(?) jest!) ] So - does the Prius converter handle audio average current demand plus normal control & lighting demands? (And recharging of the 12V batteries)) We know the Prius 12V battery is small (20AH - aka motorcycle battery). And it "merely" handles the car booting (controls etc). IE - it is "critical" to have, but being only only 20AH means a "small load". A 20AH should not be charged at more than (say)4A - yet the converter may handle 50A. (No doubt for say 200W = 20A of lights etc?)    So why not replace the standard battery with a bigger one? And/Or add another for the amp surges? (And provide amp reserve time?) Then it's just the normal question of "do we isolate the parallel batteries when not in use or being charged?". I vote yes - a mere relay of maybe 150A -200A capacity (for 1200W RMS amp "peak" plus recharge current) between the two batteries (plus fuses?), triggered by the amp's ON switch OR by a "converter is converting" signal (the equivalent of a charge-lamp in an alternator). This sounds way too easy. Where have I stuffed up? ogjlbh21 & admired friend - please help!

i read my friend your messages and he lauhed at some points and said your a character lol but you seem to know what your talking about. he told me he dont even understand some of the stuff you have said, so just to ask you. he also told me that if i dont want my lights to dim i can buy a relay for my headlights and fogs. he said its like $20-30 and would run from the lights directly to the battery. so i have been looking into these and the cheapest i can find them is $40 so i think i might do this. but i still have these 2 batteries now. im waiting for a decent day to atleast put the khc1400 in. i started to one day but then it started raining and yeah long story short i didnt finsh and ended up just reconnecting the original battery. the headlights are factory hids and run and the ballast are 35w i have factory fogs, oh wait sry i installed hids in the fogs so the ballast for them is 35w like i said before i have the 1000w amp(1000W RMS @ 1.5 ohm - 4 ohm (11V-14.5V)) but will have a 1200w amp as soon as it comes out. plus w.e other draw there is from the other things. i have factory door speakers and dont plan on changing them anytime soon as i already sold my door speakers from my old car because i didnt want to mess with the prius factory amp. and didnt want to hook up those speakers to the factory amp. because the amp has idiotic levels(plus would be way under powering those speakers) and didnt want to ruin/ not get full potental out of them expensive speakers. sothe only thing i need to power is my amp 1000w soon to be 1200w so i have a khc1800 just incase i do decide to put more in the car.the khc1800 is more then enough for anything i would put in that car by 100-200 watts atleast.     i cant fit any bigger of a battery then the khc1400 in the stock battery holder (in the trunk).the khc1800 is goign somewhere in the truck but not quite sure where yet. there isnt a alternator so i cant upgrade to a bigger one. there is that computer (which im not going to mess with) which u stated is pretty much a alternator. but there is no way for me to upgrade it that i know of. i wont be full blasting at all, maybe once in awhile but i have a baby so the sub will b very low most of the time. i would say just barly noticeble just to give some proper sound imagining. lol i deff agree with your view on caps. and personally would rather put the second battery in then a cap. but if in your opinion that is my best option then thats what i will do. i will just sell one of the batteries i just bought and buy a cap. i would try and fit the khc1800 in somewhere (wont fit in stock battery holder) then put the cap on my amp rack. my buddy thinks he has a 1.5 farad cap that he will sell me for $25 so that is no problem its a raptor but raptor is decent. like u said the cap would only make a difference if the cars electrical can handle the audio system. but i dont think it can. i hooked up the amp and sub like 2 weeks ago and my lights were flickering, but my one headlight has been flickering (accordin to my fiance) she just told me today so that means my one hid is about to fail so maybe the cars electical can handle the audio system. i will have to test it again. but if it cant the cap wont do any good as then my battery is drained anf the cap will be useless. but if i had the khc19800 plus the cap would that make a differece? not sure on that one. lights flickering is usually voltage problem, over powering the alternator which cant recharge the battery fast enough. so if my system is too much im back to putting in the 2 batteries i take it. which i would preffer anyways. ben said he could help with the install once i get your advice. he asked another installer at the shop he works at and they said to bring the car in but the owner will try and charge me $75/hr and i aint paying that. plus i would have to drive 4 hours to get to bens place, deff not worth it. he is willign to come to me if i need help( with tappign into the "On" button for the isolator. what you said makes sense for the most part. but now im stuck as to what i should deff do. im going to test the amp and sub again and let you know what happens. then i can test voltage to see what i will mostly be running at and calculate average wattage used. the battery in my prius is bigger then the normal prius battery, because i have a 07 prius touring with smart key system so the battery is a lil bit bigger. i have read too several places that the converter does indeed handle up to 50a i have to options for upgrading the battery(khc 1400, khc1800) as stated before the 1400 fits in stock battery holder while the other one is too big and would have to be placed somewhere else as stated i would liek to add another one but not sure what to do about the isolator situation. not sure which isolator to use. (i think u told me but i dont remember and read through what you said but cant find it) the isolator i found ,i think u said scared you. i have 3 circuit breakers 200a load capacity for which i bought instead of fuses between batteries and amp. do u suggest a isolator for my situation? i will look for some with 200a capacity online tomoro. i think to be safe id rather just skip the cap as i feel the same way about them as u do and would rather avoid them. so now to just find a isolator for my situation. my friend said to be careful getting a isolator but didnt say y. i think he means because buying online but i will have to clarify. again i typed this up on notepad and also have spent a few hours drinkin this evening so sry if this post dont make much sense lol.

also my old isolator was a pac but i forget if it was 200a or not. i think i have it here somewhere i just need to find it. again my friend told me that isolator wasnt good but im not sure y.

Just any suitable CONTINUOUSLY rated relay (assuming manual control - ie, via a switch or amp on-off signal or other signal (like alternaor charge lights (not that you have one)). PACs seem expensive. I have seen 200A-400A relays for ~$20-$30. (Not that I recall where other than it was on the12volt.....)

i was just showed this and wanted to see what you thought. i think i t will work good but i dont have a price on it yet though. Battery Integrator Charging multiple battery banks without use of diode isolators dictates that the batteries be connected or “integrated” only whenever a charge voltage is present so that they may be charged simultaneously, then disconnected or “isolated” when in use to allow for selective discharge and avoid having the secondary or standby battery drain into the primary battery. Battery Integrators perform this function automatically, acting as a “smart” switch to connect independent battery banks only when a charging voltage is present. Otherwise, they are isolated, and discharge between banks is prevented. The traditional rugged and reliable diode isolator can also be used for this function (see Battery Isolators above), as it also maintains isolation between banks and allows charging from multiple sources. However, one drawback is inefficiency when voltage is lost as current passes through the diodes, resulting in undercharge if the charging source does not compensate for the voltage drop. The Battery Integrator causes no voltage drop in the charging system, while the multiple batteries are charged as a single bank whenever a charging source of approximately 13.2 VDC or 26.4 VDC or greater is present (depending on model). When the alternator or charger is off or a large load causes the voltage to drop below the disconnect point the unit breaks the common tie between the banks. This allows selective battery discharge and prevents “dumping” of a higher-charged bank into a lower-charged bank. The unit may also be activated to connect other batteries through the key starter or a manual switch to provide an added “boost” from the secondary battery whenever the starter is engaged and the unit senses there is sufficient voltage in that battery to provide an assist. For systems with more than two banks, an isolator must be installed for each additional bank to provide the same isolation and integration as described above. Features • Enables charging of two separate banks without voltage drop, yet maintains     100% isolation at all other times. For systems of three banks or more, an additional unit must be installed for each additional bank •     Heavy duty silver-plated contactor, continuous duty rated to 100 amps • Voltage sense circuit, epoxy encapsu-      lated and heavy duty continuous rated solenoid are all designed for use in marine environments • 12 volt model has ignition protection rating • Easy three-wire hook up for two bank systems (BATT +, BATT +, GROUND) • Terminal for optional wiring of remote light indicating when battery banks are integrated • Optional internal connection can be wired though key starter or manual over ride switch, tying battery banks together for extra boost during engine start Specifications Models: BI-100; BI-200; BI-24-100 Battery Integration Connect Point: 13.2 VDC (approx.) / 26.4 VDC (approx.) Battery Disconnect Point: 12.8 VDC (approx.) / 25.6 VDC (approx.) Maximum Continuous Current: 100 amps (100 amp models) / 200 amps (200 amp model) Peak Maximum Current: 400 amps (100 amp models) / 600 amps (200 amp model) Operating Temperature: Control: -40 to +85˚ C / Solenoid: -28 to +48˚ C Terminals: Battery Connections: 5/16" copper alloy stud Dimensions: (H x W x D): 3" x 3.25" x 2.5" Weight: 1 lb. Approvals: CE Marked The Battery Integrator is ideal for expanding the single charging output of an inverter-charger to maintain both the house bank and an engine start bank, then to isolate them during inverter function, so current is drawn from the house bank only. actually just found the price.... for a 200amp its $230 so nevermind that. what about this : http://www.newegg.com/ Product/Product.aspx? Item=N82E16882260035& nm_mc=OTC-Froogle& cm_mmc=OTC-Froogle-_- Eco+Gadgets-_-Sunforce +Products+Inc.-_- 82260035 the pac200 is $40 and some change

Yeah - I think that's a great idea. It's probably makes better cents spending $70 or $230 instead of $20 for the same functionality. That keeps economies alive and people in business - and that's a benefit we all want. So whenever the Prius dc-dc converter is not converting, your batteries will be isolated. And I presume the Prius dc-dc converter/charger operates when the system is on (ie, IGN on), so those systems save you the trouble of tapping into the IGN key (or "system on" on key) or the amplifier's on signal etc. Then you can add ordinary relays for other batteries. Ooops - sorry - I meant buy more of the same as they suggested (I forgot the extra common-cents over using ordinary relays!).     Personally I'd use plain relays instead - but that's because I know of the added unreliability due to extra circuity (through component failures etc) as well as the complications of voltage-sensing systems (thresholds & delays). Then there is the cost saving as well.... PS - Sunforce 60113 150 Amp Battery Isolator - I just noted their "A built-in electronic MCU chip can intelligently monitor and charge both batteries, and connects or disconnects the auxiliary battery to the main battery as appropriate." Yeah, right - it MONITORS the charge state of both batteries etc etc. Funny - I thought it switched based on voltage only.... (If only it were for sale in Australia.... Projecta no longer have their "priority charging" crap on our packaging.)