Using 48 Volt Battery String To Get 12 Volt For Starting

[WStayton]

Okay, hold my hand her foir a minute, and tell me it this is a good, bad, or indifferant idea!  <grin>

  I'm envisioning using for my "house" batteries, three "strings" of eight each 6 Volt, cheapo Sam's Club supposedly golf cart batteries, supposedly made by Excide and equivalent to their E-3600 model 6 volt (awaiting verification by Sam's Club - don't hold your breath! <grin>) with the three strings in parallell to supply 48 Volts DC for the  Xantrex XW6048 inverter charger.

  Note, the engine will be hooked up via cooling circuit to hot water and won't EVER be really frigid.  Room temperature, during winter when it would see most service, will be at least 40 F on -30 F nights, so, its room ambient temperature should normally be higher than that.  Also, a wood burning furnace will be supplying "extra" heat as needed, so as soon as the engine turns over it will have hot, or at least warm coolant, so engine warm-up/starting SHOULD be a non issue.

  My area of concern is that, with three strings of eight batteries each, in parrallel, I REALLY want to keep them all in about the same state of charge so I'm concerned that if I start the engine  60 times a year, and always do it off of the same two batteries, am I building in a problem?

  The engine comes with its own European alternator that says its an 80 amp/12 volt unit, but looks like it ought to be about 200 amps.  The alternator is made by Bosch but I'm not sure if it was supplied with the engine by Mercedes or was something provided by the marinizer, Nanni, a French (yecch!) company.

  I am, again, trying to cheap out - thinking that if I didn't need the engine driven alternator to charge a couple of start batteries, I could just eliminate that load from the engine.

  Engine calls for 110 amp-hour 12 Volt  battery for its statrting circuit.  The Exide's are 186 amp-hr, 6 volt, and so, supposedly, so are the Sam's Club units.

  So, okay to start off of a couple of the house batteries, or should I spring for another two 6 volters for engine start?

  So am I being penny wise and dollar foolish here?  We're only talking about $130 bux here, so its not a real deal breaker!  <grin>

[Tom Reed]

That setup will unbalance your strings. They can be put back in balance with an equalizing charge. But in general it is bad juju to do that. Just get a in expensive car bat for starting.

[Ronmar]

+1, don't unbalance your 48v strings if at all possible...  If you want to ditch the altermator, get a 48v to 13.2v dc-dc converter to float charge a separate 12v starting battery.

[LowGear]

Why not just put a trickle charger on your starter battery?  What are they $30?

Casey

[mobile_bob]

if you have ever knocked a string out of balance  you will never allow a friend to do so,,, ever!

don't do it!

its just too simple to provide a separate starting battery and not have to deal with a very real problem
that likely will not show up till it is damn near impossible to correct.

once a string is knocked out of balance very far, even equalization will never put it back to 100%

bob g

[WStayton]

Gee, something must be wrong in the firmament - EVERYBODY agreed - so far!  <grin>

Okay, so a separate string for the starter it is - I do like the idea of using a simple minded float charger for the starter battery string - then I can get rid of the 75 lb behemoth 80 lb Bosch alternator - probably worth enough for copper scrap to pay for the starter battery string! (Ok, THAT was wishful thinking!  <smile>) AND I can get rid of the two v-belts whose sole purpose in life was/is to run the alternator.  Don't think whoever designed the belt set up on a Nanni-Mercedes ever heard of using one belt to run more than 1 device, because there are FIVE v-belts to drive the normal water pump, the raw water pump and the alternator, but I guess if some is good, more is better, no?  But I'd bet heavily on them all wadding up in a nice mess in the middle of a snowstorm in the middle of the night in the middle of January!!!  Oh, but did I mention that Nanni is a French Company?  <grin>  As you might of guessed, I'm not a big fan of French mechanical design - cheese and wine and art, YES - mechanical design, NO! <smile>

Thanks for the input guys - as usual you have probably saved me from doing something stupid!

Regardz,

Wayne Stayton

[mbryner]

Okay, so a separate string for the starter it is

No, just a single regular off-the-shelf starter battery.   Like Casey said, use a trickle charger to keep it hot.   Do not attach anything to your battery strings except inverter system.

Marcus

[LowGear]

Gee, something must be wrong in the firmament - EVERYBODY agreed - so far!

Obviously we didn't understand the question.   

Casey

[WStayton]

mbryner:

  Actually I misused the word "string", what I really meant was "pair", as in "two each, 6 volt wired in series for 12 volts total".

  What I was really thinking to do, is, when I get the 24 6-volters for the 48 bank, just get two more and use them for the engine start batter(ies).  Of course, that probably is a bad idea, because I am sure that I will be tempted to switch them out with a couple in the 48Volt string, if I have them around!  Probably better to get a legitimate heavy equipment battery that is better suited to the large short-duration of the glow-plug-start cycle.

  Sorry about the mis-speak/type, I didn't set out to decieve you, REALLY!  <grin>

LowGear:

  "Obviously we didn't understand the question"

   I just knew there was one in the crowd, here, somewhere!  <grin>


  Thanx for holding my hand, guys - though I do notice that either I am getting less radical with my proposals, or you guys are getting more enured to them!!!  Much less sparks and smoke when I post!  <grin>

As alwas, thanx for the feedback,

Regardz,

Wayne Stayton

[Jedon]

Starter batteries and golf cart ( deep storage ) batteries have different design parameters, starting batteries have thin plates and are designed to provide a lot of power for a short time, deep cycles have thick plates designed to give less power over a longer time span.
Like people said just get a nice starter battery and a cheap charger, that's what I do and it works fine.

[mobile_bob]

i would just use a pair of group 31S (top screw post) batteries for the starter, they are universally available, sold in large enough numbers to be
cost effective and at 12volts each much more reliable than putting two 6volts in series to get the 12volts.

you might even consider leaving the bosch alternator in place, it will draw very little power maintaining the starter batteries and be much better for the starting battery than a cheap charger anyway.

btw i doubt seriously the bosch alternator weighs much over 30lbs anyway, that is if it is even a large frame alternator. 

also you might find later you have a need for 12vdc to power something else while the engine is running, far better to have the bosch available
than having to rely on the batteries to supply the power for the load and then worry about some cheap ass charger getting the batteries back up to
snuff for the next startup cycle.

bob g

[WStayton]

mobile_bob:

  I NEVER throw ANYTHING away - a syndrome with which I'm pretty sure you are intimately familiar - so the Mercedes/Nanni/Bosch alternator will always be around, somewhere, to be straped into use as needed - but . . . I am also kinda suspect of Nanni execution of the accessory setup on the front of the engine - Having FIVE belts whirling around to keep three things turning is not confidence inspiring, at least not to me!!! <grin>

  What I may do, is remove the belts, so they CAN'T be a part of a problem in the making and leave everything else sitting there so, if I ever need it, I can grab the belts (Now, let me see, where did I put those DAMN things???  <grin>) throw them on and be off and running, as required!

  The Bosh alternator looks like some sort of special marine part - its about half as long as the starter which would make it about 14" + / - from front to back.  It is still strapped to the engine, so I have no real idea of how much it weighs, but it IS lots bigger than a standard truck alternator.  At first thought it might be a generator instead of an alternator, due to its rough form factor, but upon reading the (German, ugh!) data plate it is, APPARENTLY, an alternator.  Probably special ordered for the french installation so that it can be lubricated with olive oil or something!  <grin>

  Suggestion's for battery type duly noted and almost certain to be followed - upon reflection, it wouldn't make a lot of sense to use  deep cycle batteries to do something that they weren't ever designed to do just so that I could have them there, standing by for a job that they would become, also, unsuited for, due to dissimilarities to the rest of the string!

  Thanx for the input!

Regardz,

Wayne Stayton

[squarebob]

Wayne, do you have any pictures of your setup/components you could share with us? A picture is worth a thousand words, something you don't have a shortage of <grin>. No offense intended.

Bob

[mobile_bob]

i would hesitate to simply remove the belts, reason being the normal engine vibration will play havoc
on the motionless alternator brgs while they sit in one place.

personally i have not problems with the number of accessory drive belts,  the fact they are using two on the alternator
tells me that it is probably engineered properly rather than simply hanging on any old alternator and throwing on a cheap
single belt because it would have been more expedient.

if the belts are in good condition, and the mounting systems are reasonably good and rigid, i see no reason that they should be
suspect or give you any reason to worry.

i have seen many Cat engines in older trucks running 3 fan belts, two alternator belts and another belt to run an AC compressor
and all of them running for what is for all practical purposes... forever without issues.

usually a V belt will give you lots of advanced warning that it needs replacement before it completely fails.

as opposed to the cam drive belt, which can fail for no other apparent reason catastrophically and still look like it was a good
and serviceable belt.

another option might be to remove the bosch alternator, and replace it with a very common delco on wire car alternator, driven with
a single belt if you like.  in the not so long run even this option is likely to be less costly than a good battery charger.

in any case, V belt driven alternators are quite reliable from a power transmission viewpoint, given the relatively slow speeds you are likely to
be running at.   1800rpm direct or what maybe 2800 if you belt drive the st24?  

i can think of many things i would worry about long before i would get too concerned with the alternator and its two V belts.

just something to consider if i were you, why reinvent the wheel if you don't have to?



seriously just use good quality automotive rated belts to do the drives, such as from Gates, Goodyear, or from Browning (industrial) and make sure the pulleys are not worn or glazed, and my bet is they will last as long as any other part of the machine.

bob g

ps. you would probably really freak out if you saw my drive system on my trigen unit, i am using dual AA belts (hexagonal section) to drive
twin 110-555jho alternator and a sanden refrigeration compressor in a serpentine drive

[WStayton]

mobile_bob:

   I AM (very) familiar with the problem of little hinges/brackets/fittings breaking off of cast structures when subjected to vibration.

  At Ford, it seemed like everybody had their own little gadget/gizmo that HAD to have a mounting lug cast into the engine structure for its mounting - the theory being, we're going to cast the stupid part any way and cast iron is only $0.05 per lb (1975), so it only costs $.005 to put my desired mounting thingy on the block.  Never mind that the castings started to look like porcupines after 1,188 different engineers ALL added their own NEEDED mounting point and the orginally 300 cast iron block now weighed 425 and need a change in the front springs just to carry it around!

  And then, all of these oh so carefully engineered brackets would, due to stress risers and metal fatigue, start breaking off, leaving a trail of "junk" dragging/hanging off, behind.

  Eventually, Ford senior management said "Enough!" and after 1976 castings were sacroscant and it took a majority vote of a panel of 15 Sr. Engine design engineers to add ANYTHING on to one of them.  Hey, Charlie, was there ever a lot of carping and bitching for the first six months after that went into effect!  And, it was good for employment - resulted in a new department called "Casting Quality Control", amounting to probably 40 people, including support staff, who did absolutely nothing but say "No way, no how!"  Of course they all bit the dust in the next major auto sales die-off in the late '70's, but it was impressive, in a "Holy spit, what will they think of next!" sort of way, while it lasted.

  Ford was a funny place to work in that the then president, Henry Ford II did just exactly what he wanted to do, period, full stop!  In as much  as the family stock, plus the voting rights of the Ford Foundation stock was about 45% of the votes, nobody could do anything that the family (Read: Henry II) didn't want to do - must be nice to have your very own little half a billion dollar multi-national hobby shop, huh?

  Anyhow, back to my hanging alternator-behemoth.  Yes, if it is just left hanging there, it will, undoubtably be the THING that breaks off and falls into the rest of the belts and leaves it dark and cold in the middle . . . yada, yada - So, I guess if I ain't gonna use it, it should come off - so now the question: Why are you sorta opposed to a stupid-simple trickle charger to keep the start battery(ies) charged?  Since my run time is going to be 6 hr/start, and depth of discharge is going to be about 0.001%, I would think anything more complicated than a rock is overkill - think a comb stroked across a neighboring cat for sufficient for the charging circuit!  No?  Or have I missed the boat her, yet again still more already?  <grin>

  About cogged tooth belts:

   I think that the highest and best use for cogged tooth belts, with regard to anything that needs some degree of fail safe is to use them as fuel in a fire!  I always wondered how vw got away with driving their interferance cam-shaft-valve-train with a cogged tooth belt along wiht the little sticker that says change every 50,000 or as required! Mercedes, on the other hand, who I think knows a little bit about the internals of diesel engines, having been making them for 100 + / - years, uses a double roller chain in an oil bath to do the same job - costs 10 to 20 times as much and has a failure rate of 0.00001%!!! Enough said about that!  <grin>

Quote:  " you would probably really freak out if you saw my drive system on my trigen unit, i am using dual AA belts (hexagonal section) to drive twin 110-555jho alternator and a sanden refrigeration compressor in a serpentine drive"

  You do have a camera around somewhere so that when it self distructs you can record the aftermath for posterity, don't you?  <grin>  Just couldn't resist - but, really, we are building these things for personal amusement as much as for any other reason, so if what you're doing doesn't bring a smile to your face, you probably need to chage hobbies!!!  There is something to be said for individuality, too - not sure exactly what, but it IS there somewhere! <smile>

  Objections to non-funtional hanging generator duly noted and, reluctantly, agreed to!  <grin>

  Thanx for the input!

Regardz,

Wayne Stayton