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....