batteries, how many, what kind?

As long as there is a fuse at each battery on the positive wire, how will the vehicle burn down? Of course, the fuse has to be of acceptabe rating for the particular wire size. *EDIT* I think your getting just a little deep into it all LoL Anyways, when you're running that kind of power, it tends to drain the battery pretty quickly. Since he'll have a large enough alternator (and if it's rated correctly), the reserve of 2 batteries will help him. Versus 1. I also don't understand why you oppose parallel wiring. Do you suggest he get 2x 6volt batteries and series wire them (which would require modification to the wiring of the charging system)? What are you recommending? -is what I'm getting at.2013 Kia Rio -90a alternator

DDX470HD GTO14001 GTO1014D (x3)

Big3 in 1/0G

1/0G to GTO14001

That's a bit like saying that fuses stop houses burning down. Unfortunately most arcs are well under 16A & 8A - infact usually only a few amps.... Fuses protect against shorts etc. Batteries - especially AGMs - can experience thermal runaway.    I read of a "too hot to touch" single 3-month old Optima battery powered by a 45A and later a 75A alternator. The standard fuselinks were under 35A but I am unsure if they were upgraded. In his case, 2 cells had collapsed so that can mean (in simple terms) over 35Ax4V = 140W of heat. Now when you have a low resistance fully charged AGM pumping power into another battery of lower voltage..... Then there are nice things like sparks and hydrogen gas (faulty internal connections leading to arcs that ignite the already gassing "overcharged" monoblock. These don't happen with non-defect new batteries. It happens later....

That's for you to decide... There are those that say paralleling is okay. There was a recent statement on another forum by the (newish) eCare Manager of a well known AGM brand stating their batteries could be paralleled. However he supplied no data or anything in support. (I consider his statement as valid as "paralleling 2 identical batteries does not double their failure rate" - where failure rate is as I've mentioned earlier.) Then there are the so-called learned bodies and battery experts that are against paralleling and state why. (And if it must be done, two identical batteries co-housed side by side with diagonal matched connections etc because that reduces it merely to parallel MTBFs - ie, double the unreliabilty.) And sorry JM, I missed the later part of your reply. Why am I so against paralleling. Let's see - experience, recommendations of standards and other bodies, other readings... But isn't that like asking why are you so in favour of it? I just read of someone that has more than two batteries in parallel and they have lasted years. Mind you, that is within statistical norms (it just the other 98% that fail), but his were not in the engine bay, were discharged not eve to 50% (was it 20%?) and were immediately recharged. Series connections are a different issue and are known to be far more reliable and not as catastrophic. That's why telcos etc use 2V cells instead of parallel 6V, 12V etc. But that's obvious anyhow - what is more matched than the cells within a monoblock? A cell that is twice as big is very different to 2 identical half-sized cells in parallel. Keep in mind, all I'm saying is use a simple isolator. That not only allows paralleling of mismatched batteries (as long as they are equal voltage lead acids) plus the added benefit of independence - ie, you can flatten your audio battery yet still crank your engine to get home and recharge etc. And if you do want to parallel for a heavy load (like cranking) - that's usually just two contactors rated for starter currents that bridge the "normal" end fuses and isolation relay (assuming suitable interconnecting cable and that the fuses/breakers and isolation relay are not sized nor intended for cranking - though a 400A load is cranking!)

As long as the OP has -however many- matching batteries (of the same age), with wire of appropriate size connecting them -properly fused of course- with little ground return resistance, then he will be completely fine. He's got a HO alternator on the way, for crying out loud! Not only is it done all of the time, with mismatched batteries alot of the time, but you have not yet stated 1 source. All you keep writing is how you 'read something' or 'heard something'. I've never heard of someones car, that was properly fused ;), catching on fire.2013 Kia Rio -90a alternator

DDX470HD GTO14001 GTO1014D (x3)

Big3 in 1/0G

1/0G to GTO14001

Oh dear - I'm giving errored generalisations & opinions like everyone else! I'll attempt to match jmelton86's experience and cited sources later. As I said to OP metaljoey, it's for him to decide. Sorry Joey, I didn't realise I was basing so much on readings and hearings. Albeit that most readings are probably from this or related forums, though hearing is rare since I don't have that sort of involvement....     If paralleling is done all the time with mismatched batteries as jmelton86 states, then it is obviously fine.... You need not read on - I usually only respond as below to OP questions, but it's been a while so I'll address the other issues jmelton86 brought up. If paralleling & matching is not an issue, why so many bother about matching batteries? Income? BTW jmelton86 - I presume your "done all the time" means "without detrimental effect". Could you clarify that? Not that I infer any motive, but I'm thinking of a classic case where someone proposed a control method to not only simplify - but also overcome major flaws with a common traditional method of engine control (mistakenly thought to protect the engine). Despite respondents agreeing with the failures - as well as contributing additional damaging scenarios - with the traditional method, they asked the proposer "so why do <all those> use <the traditional system>...?" as if somehow the proposer could account for their practices or lack of understanding! The proposer was so diplomatic (and far more tolerant than I). He emphasised how tricky the concept could be to grasp and that even he had taken over a year to do so. (He had tried to combine the two methods until he saw the light - from which he could convey the same to others...). I digress, but I sense certain similarities in this thread. I guess my opinion is based merely experience. Unlike you, I have seen cars burn to the ground, though - despite being standard - they were not suitable protected (by definition) eg, VW-Beetle under-seat batteries & front collisions (Bosch fuses!); Jaguar XJ6 (starter cables - unfused, but insufficiently protected); even my Aunt's Fiat 124 which (unfortunately) I was driving at the time - but that's Italian and they rarely electrify properly. Alas I never saw the Pinto and similar. I have also read a few - a recent one of a restored car just 2 weeks on the road (but that's a restorer fault) etc. Except for batteries that fail within 8 months (if they haven't exploded beforehand - viz Victorian Taxis some decade ago), I admit most recent failures (recalls) are simply failures and not fires. At least for standard vehicles. But fires and melted batteries - oh yes, I have seen a few, though many are often non-vehicular systems (eg UPS, telco, remote, etc) else non-standard automotive installations by DIYers that get their info from the web (fools!) or their own common sense.      As to citing references, I forget that providence no longer exists - sources cannot be confirmed. And that assumes people actually research and Google before posting opinions - many obviously don't before asking questions (yahoo!). But some of my sources/references are difficult to cite because they are protected (IEEE or other reports), and I can't always find the recent source, whereas others are from long ago or basic texts... I don't expect to cite basics like statistical/reliability or other math? (Yes, I know that 2 parallel devices normally increases reliability, but that's where our battery knowledge modifies the math to "2 failures in series".) F.ex - whist trying to find my last post's reading, I found instead "Ray Prowse, who used to inspect failed systems for the Solar Energy Industries Association of Australia, commented that in every case of system failure, there were batteries in parallel. While this may not be the core reason for the failure, it is an indication of poor practice. Noel from Solar Tasmania subsequently commented, ‘Our experience with parallel batteries, even when wired correctly, is don’t try … even when they are identical type, age and capacity …’." [(from rpc.com.au/products/batteries/deepcycle_faq. The same later says "Australian Standard 4509.2 stipulates that ‘… the number of parallel strings be minimized …’. The standards also stipulate that each parallel string must be fused and ... ". Not that that was the Report that I was looking for, but it will do for now. Besides - it has a familiar parallel battery wiring diagram on it.... You'll see similar at allaboutcircuits.com/vol_1/chpt_11/5 (4th diagram). (FYI - It may be that AS 4509.2 deals with series strings of monoblocks (batteries) connected in parallel - eg, for hi-power AC UPS systems - and that is less of a problem than 1 or 2 series batteries in parallel! And I realise the specific nature of all the above, but I am just showing similarities in the limited time I'm going to spend on this.) Other things I have replied are generally supported publicly - eg smartgauge.co.uk/batt_con as linked from jgdarden.com/batteryfaq/carfaq7.    If you can find something that contradicts me in references like JG Darden's BatteryFUQ (a source I highly recommend) or other reasonable sources like bcae1.com (eg bcae1.com/chargin2.htm), rpc.com.au/products/batteries/deepcycle_faq, please let me know. (I have discussed some issues/differences elsewhere.) There are a few interesting publics like btechinc.com's The_Complete_Guide_v2, but they are probably too specific with nil background - eg, excepts from p17:    "Background: These two parallel 40 battery strings are only 2 years old, yet the impedance shows they have “Failed” with a 50 to 100% rise overall.

The Service Provider was adamant that the strings were “OK” on this mission critical system - the voltages measured were within acceptable limits.

....elevated operating temperatures severely affect battery service life.....

This is also another example where voltage does not relate to battery health - all voltages are within “norm”." (Note - 40 series batteries - often less of a problem than single batteries in parallel.) But a lot of my info has come from my work experience - eg, telcos, defence projects, safety groups etc. Unfortunately a lot of that info is restricted else not available (in electronic form). As I read your replies, you imply that different temperatures of matched batteries have no effect on charge & discharge rate & lifecyle - hence they remain matched(?).     Not that it matters anyhow, because you can simply parallel any mismatched battery with no isolation etc - it is "done all of the time, with mismatched batteries alot of the time.... And an HO alternator overcomes all the problems above that could be cause by a standard alternator...? Oh well, time for me to apologise to all concerned. I may correct my writings where possible and make this the new reference source.    I won't bother about the sources and bodies I cited above - let other fools follow their recommendations (now that I know better LOL!). Thanks for simplifying the whole procedure! I was rapt that I had negated all these expensive diode and other isolators to a mere relay. Now I find even that relay can be bypassed too!    BTW - Can you link some of your references? The people I deal with get pretty narky on that....

Oh you had a question about batteries did you not? Get 3 Kinetic HC1800's wired parallel. At least you wont regret it. One under the hood, 2 by the amps. Call or email XSPower direct. Tell them your rms and your alt info, they will square you away.This is what I do for FUN!