COACH BATTERIES
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08-09-2008, 09:11
Post: #11
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COACH BATTERIES
> "The extra connections in a six volt system negatively impact
> reliability and efficiency," > > On my two six volt Trojan T-105's, I have a "00" wire six inches long > connecting the negative and positive to make it 12 volts. > > Please explain the "negative reliability and efficiency impact" of > this "extra connection." Two 6 volt batteries have: two connections from terminals to plate frame two connections from "00" wire to cable connector two cable connector to terminal connections more than one 12 volt battery. All subject to ohmic loss, corrosion and vibration. A universal premise in reliability is, the more elements the lower the reliability. Regards, GPSGary |
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08-09-2008, 09:24
Post: #12
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COACH BATTERIES
> If you deep discharge your lead acid batteries like you suggest you
> will destroy them. That type of cycling is for Nicad and other types, > not lead/acid. As lead/acid batteries discharge below their "natural" cell potential their operating characteristics enter a zone of increased internal resistance. At some point (before damage) the current they will supply to a resistive (incandescent) load drops to NEAR zero. The lower the current through the incandescent load the higher its resistance will also be. I admit, I should have clarified that you don't leave the incandescent load on forever. A few hours after the bulbs dimmed would be ideal. Under no circumstances should really low resistance loads (like cables) be used to help with the discharge. Regards, GPSGary |
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08-09-2008, 10:08
Post: #13
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COACH BATTERIES
> As others have pointed out, there are some technical issues with
your comments. I think if you research the topic you will find a steady stream of "Lead-acid is not subject to memory' on technical sites. Rule-of-thumb is to avoid discharge below 50% whenever possible. I wouldn't personally go so far as to say a 100% discharge will destroy a battery, but it will definitely shorten life. I misused the term memory for simplicity but you guys are sticklers for details. Please read: http://www.udel.edu/igert/pvcdrom/BATTERY/charlead.htm > One other issue is this part: > >Price vs. performance vs. reliability. > >Two $75 55ah 12 volt batteries will be more reliable than one $150 > >100ah battery but take up twice the space > > As you noted correctly "sheer lead volume determines capacity" so it is not possible to have a 100AH battery that is the same size as a 55AH battery unless the latter has an extreme amount of wasted space. Yes atomic physics makes "sheer lead volume determines capacity" true but characteristics like charge and discharge rates determine "useful capacity". A good example is that a well designed and built battery with EXACTLY the same lead weight may have double the "cranking capacity" as a poorer designed and built battery. Charge and discharge rates and efficiency are also effected by design and workmanship. After looking up the prices of the super premium DEEP CYCLE (don't buy ANY that aren't deep cycle) and doing a cost benefit analysis, I would recomment the following; Buy enough good quality, (not necessarily the highest quality or price) 12 volt deep cycle batteries that you can start the coach if one battery shorts a cell (99% of all failures) and replace your batteries on a periodic rotation basis WHETHER THEY FAIL OR NOT. EX: If you buy 48 month warrantee batteries and you have 4 replace the oldest one every year. If you can start the coach on three batteries, you have a 100% redundant system. Reliability exceeds 99.99% by mathematical proof. The cost benefit method would be to figure the cost per ampere hour (a pretty good indicator of overall $ to performance) and then buy the lowest total cost batteries that have sufficient cranking power capacity to start the coach with a 10% margin, WITH one battery out of the system. I'm guessing that this would result in a system of $100-175 12 volt batteries, maybe adding one additional spare somewhere. Regards, GPSGary |
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08-09-2008, 11:18
Post: #14
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COACH BATTERIES
On 8/9/2008 at 10:08 PM hippieforever3 wrote:
>I misused the term memory for simplicity but you guys are sticklers >for details. >Please read: >http://www.udel.edu/igert/pvcdrom/BATTERY/charlead.htm OK, I read it. I only see confirmation that 100% discharge is a bad thing. What are you thinking it says? >Yes atomic physics makes "sheer lead volume determines capacity" true >but characteristics like charge and discharge rates determine "useful >capacity". A good example is that a well designed and built battery >with EXACTLY the same lead weight may have double the "cranking >capacity" as a poorer designed and built battery. True, but that's equating "useful" with cranking, when our most-common concern is total capacity, for house use. You used AH in your 55/100 example, and that is not cranking capacity. You will not be able to design 100AH in the same amount of space that you would use for 55AH, no matter how good the design. Don Bradner 90 PT40 "Blue Thunder" My location: http://www.bbirdmaps.com/user2.cfm?user=1 |
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08-09-2008, 12:37
Post: #15
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COACH BATTERIES
GB:
While u r an "Engineer with a certificate"............a better answer would have been as follows: "The OHMS in a seven inch "00" cable is such a small RESISTANCE that the CURRENT LOSS is probably negligible." Instead u had to DEFEND YOUR RIDICULOUS STATEMENT WITH GOBBLY GOOK. Regards, Hank 90SP36 --- In WanderlodgeForum@yahoogroups.com, "hippieforever3" wrote: > > > "The extra connections in a six volt system negatively impact > > reliability and efficiency," > > > > On my two six volt Trojan T-105's, I have a "00" wire six inches long > > connecting the negative and positive to make it 12 volts. > > > > Please explain the "negative reliability and efficiency impact" of > > this "extra connection." > > Two 6 volt batteries have: > two connections from terminals to plate frame > two connections from "00" wire to cable connector > two cable connector to terminal connections > > more than one 12 volt battery. All subject to ohmic loss, corrosion and > vibration. > > A universal premise in reliability is, the more elements the lower the > reliability. > > Regards, > GPSGary > |
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08-09-2008, 12:55
Post: #16
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COACH BATTERIES
I am not an engineer ( nor did I play one on TV) but what you are
suggesting goes against avery article I have ever read. Some were written by battery mfr. engineers. You are never supposed to mix old and new battreies in a battery bank! 6 volt golf cart batteries will give you longer life than any common wet cell deep cycle 12 volt. They are sturdy and made to handle frequent discharge. There is a reason why most coach mfrs. use the 6 volt batteries. It would be cheaper to install the 12 volts. Every solar seller also recommends the 6 volts. I think you are way off on this one, Notwithstanding any engineering degrees! Bruce 1988 FC35 ( 6 -6volts) 2008 Monaco ( 8 -6 volts) |
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08-09-2008, 14:48
Post: #17
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COACH BATTERIES
> While u r an "Engineer with a certificate
Forget the certificate ... 30 years experience tells me (and Mil Specs too) that the more connections there are the more there are to fail. EVERY ADDITIONAL CONNECTION HAVE A FINITE PROBABILITY OF FAILURE. > "The OHMS in a seven inch "00" cable is such a small RESISTANCE that > the CURRENT LOSS is probably negligible." > The resistance in the wire is negligable, the resistance in the multiple added connections that can loosen or corrode is not. > Instead u had to DEFEND YOUR RIDICULOUS STATEMENT WITH GOBBLY GOOK. But thanks for your input anyway. Regards, GPSGary |
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08-09-2008, 14:54
Post: #18
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COACH BATTERIES
CAN WE BEAT AN ISSUE TO DEATH OR WHAT!
hippieforever3
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08-09-2008, 15:03
Post: #19
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COACH BATTERIES
> OK, I read it. I only see confirmation that 100% discharge is a bad
thing. What are you thinking it says? > I admitted I was unclear. 100% discharge is unhealthy but some deep cycle batteries are designed for up to 80% discharge. As a general rule, batteries will last the longest and provide the best service if they are used close to the limits of their design. It's a little like atheletes, If they never strain a little they get weaker. If you over stress them they get damaged. > True, but that's equating "useful" with cranking, when our most- common concern is total capacity, for house use. You used AH in your 55/100 example, and that is not cranking capacity. You will not be able to design 100AH in the same amount of space that you would use for 55AH, no matter how good the design. > That would be true if batteries weren't made in standard sizes. However to offer choices to the marketplace, manufacturers will stuff the guts of a 100ah battery into EXACTLY the same case as a 55ah battery. The reason that the 55ah batteries exist at all is that when you buy a new car it comes with a battery and most car manufacturers will do almost anything to save as little as $0.50 in their costs. They aren't equipping your new car with one ounce more lead than they have to. Regards, GPSGary |
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08-09-2008, 15:06
Post: #20
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COACH BATTERIES
GPSGary,
What you may be unaware of is that we Bird owners know that part of the regular maintenance routine is to clean and inspect the battery terminals. We have been round and round with the battery situation and found, through practical experience, what works best for us. If I were designing a space craft it would be very high on the list to minimise the points of failure, but that is a different situation. Using deep cycle six volt batteries cabeled up in a series/paralell configuration has proven over time to be the right way to go in an RV. Theory aside, practical experience has proven the concept to be correct. Gardner 83FC35 --- In WanderlodgeForum@yahoogroups.com, "hippieforever3" > > > While u r an "Engineer with a certificate > > Forget the certificate ... 30 years experience tells me (and Mil > Specs too) that the more connections there are the more there are to > fail. EVERY ADDITIONAL CONNECTION HAVE A FINITE PROBABILITY OF > FAILURE. > > > "The OHMS in a seven inch "00" cable is such a small RESISTANCE > that > > the CURRENT LOSS is probably negligible." > > > > The resistance in the wire is negligable, the resistance in the > multiple added connections that can loosen or corrode is not. > > > > Instead u had to DEFEND YOUR RIDICULOUS STATEMENT WITH GOBBLY GOOK. > > But thanks for your input anyway. > > Regards, > GPSGary > |
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