Hi Lindsay, Thanks for letting us know what is available. I hope I didn't waste too much of your time. I'm not sure what you mean by "wide plate".
Don, Engine start up batteries have thin plates (high amps). The wide plates are the deep cycle type batteries. The T-105 have the heavy wide plates. Wal-Mart will never have an AGM due to high prices. All battery shops carry the AGM's. You can find them everyplace you go. Johnson Controls is here in Tampa and builds batteries under 20 or more names, Wal-Mart, Sears, K-mart, NAPA, Auto Parts, and you name it. They also recycle all the old batteries for hundreds of miles around as well. So buy the one you think it best but most are the same in different in battery labels. :lol:
Don, Batteries have been a pain in the butt for the hold 140 years. Look at GM and the new electric car. GM has worked on the battery not the car for years now. May be ready late next year, short range of 100 miles or less in hills and you are out of gas. GM had to add a gas engine back in, first pass was to drop the the engine to save weight and cost. First person to build a long life battery that will work for lots of years will have more money that they could ever spend. The write up covers all the correct information.
AGM batteries ranging in size from 50 Ah to 150 Ah are commonly used in UPS (Uninterruptable Power Supplies) in big IT departments like banks and big business operations. Due to the need for 100% reliability of millions of dollars worth of data they often replace their AGM's every 2-3 years even though they can give excellent service for up to 12 years if properly cared for. I found an "inside connection" through a friend who worked at such a IT firm and was able to purchase twelve three-year old 127 Ah AGM batteries for $7.00 each (recycle/scrap price) that had an original retail of $384.00 each. All were near perfect as load tested with a 500 amp carbon pile tester. The size of these batteries was closer to a group 29 - each weighs 102 lbs. Two have been in my fiver for over a year. Later I picked up twenty-four 50 amp hour AGM batteries that were three years young and had never been installed (they are now part of a solar power bank) They are easily parallel connected for whatever reserve power rating you want. I paid $4 each for these batteries. My reason for sharing this is not to brag about my find but to call attention to a source of perfectly good, cheap AGM batteries that is often overlooked. If you have or can make such connections for re-cycled AGM batteries it will pay you high rewards in the pocketbook. DO NOT call an IT firm and ask a stranger if they sell their used UPS batteries. You will get a flat NO due to disposal rules (environmental stuff). You really need to know someone on the inside who knows you are not going to dump them in your back yard. Most all AGM's are multi charge deep cycle type batteries. One real positive for RV use is their vibration damage resistance is virtually 100%. Regular flooded deep cycle batteries often fail in a RV from the 4.3 magnitude earthquake jolts they experience - not age. Second big plus is no gassing out -- so you can put them in an un-vented compartment or even a living space. Number 3 is position -- sideways, upside down, whichever way they fit best. The major downside to AGM's is that overcharging will ruin them very quickly. Therefore, ALWAYS use a minimum of a 3 stage regulated charger specifically made for AGM batteries. A conventional RV converter charger is NOT the best charger for AGM's and battery life will be shorter using a charger designed for flooded cells. I purchased a new Charge Wizard from Progressive Dynamics for my PD converter for AGM charging. It was something like $35.00. As for equalizing AGM's like conventional vented lead acid batteries -- don't worry about it (4-stage chargers are not needed or good for an AGM). They do not accumulate sulfate on the plates like conventional wet cells. In fact, equalization charging is potentially harmful to AGM batteries. BTW - I'm an EE and one of the courses I teach covers batteries extensively.
Professor, Very good write up on AGM's. Most people miss the earthquake jolts part we all have in RV travel plus no water in cells. The two items will kill flood cells off at a high rate. We use two AGM 8D type and find they work great with our three stage charger system. Only down side is high cost but no acid damage or water problems off set that item as well. Don, Yes, batteries are a little like a old dog. Good write up.
QUOTE(John Blue @ Nov 21 2009, 09:40 AM) [snapback]20065[/snapback] We use two AGM 8D type and find they work great with our three stage charger system. Two 8D's? My gosh, their combined weight must be close to 500 pounds! I carried 4 of the AGM group 29's in the front compartment of my fifth wheel as auxiliary batteries for my 150 watt solar array and 3,000 watt Vector MAXX inverter. This was in addition to the two identical AGM 127 Ah batteries for the house side and the 4,000 watt generator. At 102 pounds each I was adding about 700 pounds to the pin weight of my fifth wheel with my additional equipment. The cheap Lippert electric landing gear drive assembly crapped out with the additional load. So, I had to move the 4 AGM's and inverter on the aux side to the TV bed, which had excess load capacity. Anybody adding batteries needs to consider the added weight and the impact on the axle and tire loading. BTW - in response to a PM from pianotuna, I did not mean to imply in my last post that AGM's could not develop sulfation - only that the issue of a regular equalization charge is not part of the AGM maintenance routine. As with any lead-acid battery, which AGM's belong to, sulfation is inevitable if the battery is not properly maintained. This is a shot before I took the 4 AGM's out of the front compartment to reduce weight load on the landing gear drive. The protective cover was removed for this photo. And yes, the batteries in the photo were my $7 each AGM's cycled out from a IT company's UPS battery bank.
Hi professor95, It is interesting to see that the original installation uses aluminum buss bars. Do they obviate the need for balancing the wiring harness? correctly interconnecting multiple batteries Method #3 or #4 works for four twelve volt batteries.
pianotuna - My MH has three batteries, two for the coach and one for the engine. The coach batteries have a disconnect switch which I use when in storage. I assume that there is no disconnect for the engine battery. Would there be anything wrong with removing the battery while in storage and keeping it charged at home? Would I be able to exercise all other systems run by my two other batteries if the engine battery is removed (seems like a stupid question, but...)? My MH manual is not at home so I can't look up to see if the generator is connected to the house batteries or to the engine battery. Is it the same for all MHs? I have an Itasca Suncruiser gasser. Thanks.
QUOTE(pianotuna @ Nov 21 2009, 10:18 PM) [snapback]20079[/snapback] Hi professor95, It is interesting to see that the original installation uses aluminum buss bars. Do they obviate the need for balancing the wiring harness? correctly interconnecting multiple batteries Method #3 or #4 works for four twelve volt batteries. Don, If you look again I believe you will see that they are balanced. The Vector Maxx has four 12 volt inputs - two positive and two negative. These four are distributed along the aluminum buss bars so as to pull current at the center point of the two pairs. The balancing method shown in the link you provided above is for those 1% who want every last available amp and millivolt from a battery. It may be beneficial in extremely high amperage demand situations like one would experience with an electric vehicle or 5,000 watt inverter trying to start a roof-top A/C. But, the majority of RV'ers adding batteries want to extend time, not demand current. On an additional note, the writer's statement that balancing is needed when recharging does not apply to what we experience when recharging our RV batteries -- unless we are fast charging the bank at 200+ amps, which I would NEVER do. My on-board 120 volt powered charger for the auxiliary bank is (was) 75 amps. This gives 75/4 amps to each battery, or a little under 20 amps initial boost to a 10.5 volt battery. It, of course, tapers off as voltage in the battery rises. This charger is considered BIG for an RV battery bank. My preference for buss bars would have been copper. But, alas, solid copper buss bars of sufficient size are not too easy to obtain (or affordable!). While aluminum does have a higher resistance than copper, it is available and sufficient for my application as the total length of the buss bars is relatively short. I can't say that doing all of the balancing would never be needed in an RV, but I can say they are overkill for the average RV install and the peak current demand that will be experienced. IMHO there are too many other issues to worry about than the fractional added resistance of a "standard" parallel battery interconnection. Couple of more photos for show and tell: The one below is a vented wooden case with three group 29 Wal-Mart deep cycle batteries interconnected with a 3/4" copper pipe made into a buss bar. The lid on the case can be closed and sealed. Hydrogen is vented to the outside through a 1-1/2" flexible plastic tube in the top. Fresh air is drawn into the bottom in a similar manner. Proper venting of open lead-acid batteries kept in a closed environment is extremely important. The three photos that follow show the solar panels on the roof of our fiver. This was taken yesterday from a upstairs bedroom window in our home after we returned from a trip. On a clear sunny day I generate something like 10 amps at the output of the controller for the batteries. Nice, clean, free power. There is some loss due to the flat position of the panels, the inability to track the sun and shadows from the front A/C. But, we live with it and are happy for the power we get. The last photo is the control/monitor panel I built for my batteries/solar/generator/inverter operation and monitoring. It sits under the OEM switch panel (the meters are in the black rectangular shapes to the left). I can monitor voltage of both house and auxiliary battery banks, charge current from any source, discharge current from either bank, A/C voltage and frequency from the inverter or generator on the large display LED meters. I can auto-start the generator and select either genny or inverter power to the RV's ATS. The generator is wired so it will start automatically and run for two hours to charge either battery bank if the bank voltage drops to or below 11.8 VDC. I can, of course, over ride this function if generators are not allowed. This is the way we use batteries to augment our hunger for electrical power when dry camping. I have actually run my 6,000 BTU roof-top bedroom A/C for as long as six hours off of batteries/1200 watt inverter alone. Nice on a hot night when generators are not allowed.
Hi abbygolden, There would be nothing wrong with it--but if the starter battery is fully charged there may be no need to remove it. Just start your RV whenever you go to exercise the generator--or run a battery charger from the generator. I can't say with any certainty that all RV's are wired the same way--but I think most generators use the "house" battery bank for starting. QUOTE(abbygolden @ Nov 23 2009, 08:58 AM) [snapback]20103[/snapback] pianotuna - My MH has three batteries, two for the coach and one for the engine. The coach batteries have a disconnect switch which I use when in storage. I assume that there is no disconnect for the engine battery. Would there be anything wrong with removing the battery while in storage and keeping it charged at home? Would I be able to exercise all other systems run by my two other batteries if the engine battery is removed (seems like a stupid question, but...)? My MH manual is not at home so I can't look up to see if the generator is connected to the house batteries or to the engine battery. Is it the same for all MHs? I have an Itasca Suncruiser gasser. Thanks.
Professor, Weight on the 8D's are 162 lbs. each so you have 324 lbs. of lead in a box. Batteries are on a roll out rack and not hard to work on. Some Foretravel models use three 8D's as house batteries. We also have an 8000 watt diesel generator in front end. Weight is not a problem with our unit. Abbygolden, Need to keep power on the batteries or they will die. See Don's information. If you can power up the AC in MH that will help or as you said take them home and hook up a small charger to all. Batteries will lose around 3 to 5% charge per day. Before long you have scrap metal. The generator is connected to the house batteries and that starts the engine.
A fully (100%) charged battery will loose 3 to 5% per day. Once the battery reaches 50% (12.25 VDC) the discharge lessens to a negligible amount. A small 500 milliamp to 1 amp float charger will maintain the 50% level, a point where minimal sulfation and gas out will occur for long time storage. Disconnect your batteries from the MH engine side if you are storing over the winter without at least a 1 amp float or trickle charge. Better yet if you cannot plug in during storage - use at least a 15 watt solar panel as a battery maintainer. The MH ECM or PCM, possibly even the radio memory, will draw enough current to discharge the battery. Of course, your ECM will need to "relearn" certain functions upon reconnection and you may have to reprogram your radio presets and clock. You guys that own huge MH's on bus or JD type chassis don't have the same added weight problems those of us who have towables must live with. Not too many (if any) fifth wheels or TT's come with 3-8D batteries on a pull-out tray. We were lucky to get one group 24 battery with the new coach, which is not enough reserve power to get through a "normal" 24 hour dry camping day.
Hi Prof, I'm glad your install is balanced, there is no way to see that from the photograph as the cables are not identified. I was hoping buss bars were a "way around" balancing--but no joy there! I disagree with some of what you have suggested. Most RV folks are going for larger and larger inverters as the cost drops. Mine is probably in the middle at 2500 watts (5000 watts surge), so far more than 1% of us need correctly balanced wiring. Can you explain why balanced wiring is not important for charging? Resistance is still identical at even very low amperage, so the last battery in the chain may never fully charge, or if it does then the first one may over charge? It can't be both ways? If the balanced load points are already in place on the load side--there is no reason on earth to not use them for charging. It costs very little extra to wire in a balanced manner--sometimes even zero cost--if for example there are only two 12 volt batteries. I am fortunate enough have two banks of batteries--four with a copper buss bar system--and three with method #3 balanced load. Total capacity is 875 amp-hours. For a forum where I've documented what I've done you may wish to surf here: Technology and click on solar boondocking QUOTE(professor95 @ Nov 23 2009, 09:17 AM) [snapback]20104[/snapback] Don, If you look again I believe you will see that they are balanced. The Vector Maxx has four 12 volt inputs - two positive and two negative. These four are distributed along the aluminum buss bars so as to pull current at the center point of the two pairs. The balancing method shown in the link you provided above is for those 1% who want every last available amp and millivolt from a battery. It may be beneficial in extremely high amperage demand situations like one would experience with an electric vehicle or 5,000 watt inverter trying to start a roof-top A/C. But, the majority of RV'ers adding batteries want to extend time, not demand current. On an additional note, the writer's statement that balancing is needed when recharging does not apply to what we experience when recharging our RV batteries -- unless we are fast charging the bank at 200+ amps, which I would NEVER do. My on-board 120 volt powered charger for the auxiliary bank is (was) 75 amps. This gives 75/4 amps to each battery, or a little under 20 amps initial boost to a 10.5 volt battery. It, of course, tapers off as voltage in the battery rises. This charger is considered BIG for an RV battery bank. My preference for buss bars would have been copper. But, alas, solid copper buss bars of sufficient size are not too easy to obtain (or affordable!). While aluminum does have a higher resistance than copper, it is available and sufficient for my application as the total length of the buss bars is relatively short. snip
QUOTE(pianotuna @ Nov 23 2009, 09:52 AM) [snapback]20106[/snapback] Hi abbygolden, There would be nothing wrong with it--but if the starter battery is fully charged there may be no need to remove it. Just start your RV whenever you go to exercise the generator--or run a battery charger from the generator. I can't say with any certainty that all RV's are wired the same way--but I think most generators use the "house" battery bank for starting. If I were to charge my engine battery when running the generator for about an hour, would that make any difference? I normally also run the engine at about 2000 rpm for about 15 minutes or so at least once, normally twice, a month. I have no access to power where I store my MH.
Hi abbygolden, Yes it will make a nice difference. Depending on the battery chemistry and the charger. If the charger is one of the new "smart" chargers and the battery is down to 80% state of charge an hour may bring it back to say 90% (again depending on chemistry). If I were you, I'd: -start the generator, so the converter can work its magic on the "house" battery bank -start the engine for that 15 minute warm up -get the charger "ready to roll" on the chassis battery bank -turn off the engine -turn on the charger powering it from the generator. But then, if I were you, I'd already have a solar system in place to take good care of the "house" battery bank. QUOTE(abbygolden @ Nov 23 2009, 04:44 PM) [snapback]20113[/snapback] If I were to charge my engine battery when running the generator for about an hour, would that make any difference? I normally also run the engine at about 2000 rpm for about 15 minutes or so at least once, normally twice, a month. I have no access to power where I store my MH.
QUOTE(pianotuna @ Nov 23 2009, 02:59 PM) [snapback]20110[/snapback] Hi Prof, Can you explain why balanced wiring is not important for charging? Resistance is still identical at even very low amperage, so the last battery in the chain may never fully charge, or if it does then the first one may over charge? It can't be both ways? If the balanced load points are already in place on the load side--there is no reason on earth to not use them for charging. It costs very little extra to wire in a balanced manner--sometimes even zero cost--if for example there are only two 12 volt batteries. Don, Try this formula: Voltage drop = k x p x wire length in feet x current in amperes divided by the wire area in circular mills For Copper, K=11 For Aluminum, K=18 P is Phase Constant. In this case P=2 Let’s use #2 AWG copper as our interconnect cable. The area in circular mills will = 66,400 Our interconnect cables will be 1 foot long each Again, let’s make an assumption the amperage draw from the batteries is 120, typical for a 1,000 watt inverter load. Run the numbers: 11 x 2 x 1 x 120 = 2,640 divided by 66,400 = .039759 So the voltage drop on that 12” piece of #2 copper is less than 4/100th of a volt. Since my example assumes two batteries, the interconnect cable will only carry 50% of the current. Thus the voltage drop on the parallel cables will only be 2/100 of a volt – or better said 20 millivolts. A 20 millivolt loss is no big deal in a battery bank set-up for an RV – even if we have more than 1 one foot interconnect cable. Manufacturers of high power inverters often recomend two size “0” cables in parallel. (106,000 CM each, total 212,000 CM). Run the above numbers again for a lowered charging current. The voltage differential amounts to nothing significant! More specifically, if you have four batteries in a parallel string with no “balancing” and connect a charger, the maximum current will go to the lowest value battery first. Once it is equal to the next lowest they will “appear” as a single battery and combine with the remainder as they are charge equalized. Even 4 brand new batteries in parallel will not exhibit the same state of discharge. Manufacturing is far from being that perfect. I’ll say what I did previously again – for RV use all this “balancing” stuff is unnecessary unless you are totally battery anal. There are other uncontrollable variables in the system that will have a greater impact. As for intentionally wiring so that a bank is "balanced"; yes – sometimes it is just as easy and will not require an additional length of cable to configure it as such. But the question always remains when setting up batteries in an RV as to where they will be mounted. Often they will be some distance apart. Not every RV’er that wants to expand battery capacity has a big motor home with a huge pull-out battery tray (but it would be nice if we did ). As for the 1% - We’ll just have to agree to disagree. My thirty years of association with RV’ers gives me different numbers than you project. Besides, what difference does it make if one of us is off a few percent? The fact remains that the majority of Rv’ers are NOT high power inverter users (I am in the minority – I have a 3,000/6,000 watt inverter.). BTW - your solar set-up is extremely nice.
Hi Prof, You have not allowed for the internal resistance for the batteries, nor the resistance for each connection. These amount to more than the resistance in the wire. With only two batteries balanced wiring need not cost a dime extra. In my case it cost nothing extra for the buss bar system--and about $20.00 for the wiring the triple battery bank. I agree that no two cells are likely to have identical capacity--perhaps the same chance as two snowflakes being identical--which happens but is extremely rare. I do not have your expertize, nor do I have a spreadsheet to "crunch the numbers" so I can only quote from the smart gauge web site. "Now in all fairness, many people say 'but the difference is negligible, the resistances are so small, so the effect will also be small'. The problem is that in very low resistance circuits (as we have here) huge differences in current can be produced by tiny variations in battery voltage." I'm always interested in learning more. May I ask you to elaborate on "other uncontrollable variables in the system that will have a greater impact." Are there solutions to these variables? How can the charging current "go to the lowest charged battery first"? This seems counter intuitive to me. In an unbalanced wiring scheme the resistance will be highest to the last battery in the chain. It seems logical to me that this battery would receive the least amount of charge--and get it last as well. Folks here hate polls--but I think I'll do one now on inverter size, just to "put a finger in the wind" to see which way it is blowing. Thanks for the complement on my solar system. I got my first "solar cell" when I was 7 years old--and have wanted a working system since then. 56 years is a long time to wait! QUOTE(professor95 @ Nov 23 2009, 09:48 PM) [snapback]20115[/snapback] Don, Try this formula: Voltage drop = k x p x wire length in feet x current in amperes divided by the wire area in circular mills snip Run the above numbers again for a lowered charging current. The voltage differential amounts to nothing significant! More specifically, if you have four batteries in a parallel string with no “balancing” and connect a charger, the maximum current will go to the lowest value battery first. Once it is equal to the next lowest they will “appear” as a single battery and combine with the remainder as they are charge equalized. Even 4 brand new batteries in parallel will not exhibit the same state of discharge. Manufacturing is far from being that perfect. I’ll say what I did previously again – for RV use all this “balancing” stuff is unnecessary unless you are totally battery anal. There are other uncontrollable variables in the system that will have a greater impact. As for intentionally wiring so that a bank is "balanced"; yes – sometimes it is just as easy and will not require an additional length of cable to configure it as such. But the question always remains when setting up batteries in an RV as to where they will be mounted. Often they will be some distance apart. Not every RV’er that wants to expand battery capacity has a big motor home with a huge pull-out battery tray (but it would be nice if we did ). As for the 1% - We’ll just have to agree to disagree. My thirty years of association with RV’ers gives me different numbers than you project. Besides, what difference does it make if one of us is off a few percent? The fact remains that the majority of Rv’ers are NOT high power inverter users (I am in the minority – I have a 3,000/6,000 watt inverter.). BTW - your solar set-up is extremely nice.
