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Post Info TOPIC: How long should your house batteries last?


RV-Dreams Family Member

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How long should your house batteries last?


We have 4 marine/RV 12V house batteries that are about 3 years old.  After some extensive load testing they seem to have reduced capacity by about 15% or so.  The have been well cared for, not discharged below 55%, and kept charged when not in use.  How long should they last?  What is your experience?  We want to move to some golf cart batteries for some truly deep cycle capability but we don't throw anything away until it is truly worn out.  Must be a bit of Scottish blood.

Larry and Jacki

-- Edited by blijil at 08:37, 2007-09-13

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Larry and Jacki-belle Linley with Taiga our minature dachsund - 2011 34 ft Montana towed by a 2014 Silverado Durmax Allison 4x4.



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Larry and Jacki,

It's really hard to tell. I had one set last almost 6 years, and my friend, (who also maintains his batteries very well), had one of his batteries die just after 2 years.

I don't think you'll be sorry for switching over to Golf Cart batteries. They are soooo much better, and they do seem to last a lot longer.

Jim

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First it depends a lot on usage and care. That's a whole 'nuther discussion - www.BatteryFAQ.org.


In broad general terms, "commercial" brand names like Trojan, Lifeline, etc. often last upwards of 4-5 years. "Retail" brand names like you get at Wal-Mart/Sears/etc. frequently last under 3 years. You pay more for those commercial brands but many folks play the warranty credit game on the retail brands. Hence, over the course of many rigs, the total cost invested in batteries is probably the same overall. Golf cart batteries are a "type" of battery like a Group 27 or Group 31 while Trojan vs. Maxx are "brands" like I mentioned above. Hence golf cart batteries are subject to the commercial vs retail "brand" issues.


Some folks believe in commercial brands and replace twice a decade. Some folks opt for the retail brands and replace bi-annually getting some warranty credit each time. Overall, the total cost is probably the same! Either case I would suggest going with AGM "category" of batteries (not the same as the often called "low maintenance" or "no maintenance" batteries which are still flooded cell) to eliminate the white powder corrosion problem. Cost a bunch more but to stop that destruction in your battery tray might just be worth it.



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RVDude said things well. We really like our Lifeline AGM golf cart batteries.

It might still be worth doing an equalize cycle if your charger has such a setting. That sometimes brings batteries back to life a bit. If equalizing helps then you are not off the hook, you have to make some changes to keep them going well or you will be equalizing again. I will talk about that below.

Now I have to ask how you are charging the batteries. It sounds like you have some kind of monitor to know you haven't been below 55%. If you have that you are probably using a good three stage charger and not a simple converter or the alternator. You are best off if the charger can be programmed to provide the best charging characteristics.

If your charger is not programmable you will have to weigh the price difference of getting one that is against your batteries lasting a bit less time.

Changes to make sure you are treating your batteries as well as possible (learned mostly from Greg Holder of AMSolar, but also some other sources)
1) Find out the real charging numbers for your batteries. Some Trojans are happiest with a top off charge of 14.8 volts instead of 14.3, for instance. Program your charger to use the numbers the battery manufacturer recommends along with temparature compensation.
2) Make sure you really are getting those voltages at the battery terminals. Some people have inadequate wiring, which is very common in solar chargers, and they are not topping the batteries off.
3) Let your batteries discharge a bit every so often, weekly is best. Batteries that are discharged about 5 to 10% and topped off every week should last the longest and not need to be equalized because they are stirred up by the weekly charge.

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Bill Joyce,
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Well maybe our batteries have done pretty well considering the use.  The first year or so they were passively stored for a month or so without use but the charge was maintained.  We have added Solar (from AM Solar) during the last year and have found the system to do the job at least 90% of the time.  The other 10% of the time with a less than perfect charger but monitored pretty carefully.  But we have not been diligent about Bill's #3 point and the batteries seem to use a couple more ounces of water a month than they did originally.

We don't have the room or more important the weight capacity to go with equivalent amp hours of AGMs not to mention the cost but I guess we could get over the cost if the performance was significantly improved.

Sounds like some new golf cart batteries are in our future.

Thanks for the feed back,
Larry and Jacki

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Larry and Jacki-belle Linley with Taiga our minature dachsund - 2011 34 ft Montana towed by a 2014 Silverado Durmax Allison 4x4.



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Larry and Jacki: If you can please equalize first if you can. You might have to borrow/rent a better charger to do it. If it brings your batteries back some it will delay when you need new ones.

The idea of needing to discharge and top the batteries somewhat often is fairly new on the street. It comes from the people with well designed solar charging systems finding their batteries lasting longer than normal. A well designed solar system will discharge and top the batteries daily or close to it. Some of the newest inverter/chargers are "four stage" adding "refloat" which does exactly what I said, letting the batteries drain to 90% or so periodically. It is easy for us to do the weekly discharge when stopped since our Prosine 2.0 inverter/charger has a "charger" switch and we have some solar. While hooked up I turn off the charger and let the batteries drain a bit overnight and the solar will bring them back the next day. If the weather goes cloudy I just turn the charger switch back on.

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We will try to make that happen and see how things go.  Probably at least once a week for a while and see how that goes.  Thanks for the feedback.
Larry and Jacki

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Well after a few weeks of use we have decided the capacity is degraded but the symptom has been quite a surprise to us.  We need to water the batteries every 7 or 8 days or some cells will go dry within two weeks.  Not so convenient but functional.  Expect them to die soon and will replace in any case early next spring or maybe sooner if necessary.

Larry and Jacki

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jcw


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RVDude wrote:

First it depends a lot on usage and care. That's a whole 'nuther discussion - www.BatteryFAQ.org.


In broad general terms, "commercial" brand names like Trojan, Lifeline, etc. often last upwards of 4-5 years. "Retail" brand names like you get at Wal-Mart/Sears/etc. frequently last under 3 years. You pay more for those commercial brands but many folks play the warranty credit game on the retail brands. Hence, over the course of many rigs, the total cost invested in batteries is probably the same overall. Golf cart batteries are a "type" of battery like a Group 27 or Group 31 while Trojan vs. Maxx are "brands" like I mentioned above. Hence golf cart batteries are subject to the commercial vs retail "brand" issues.


...




What is the defining characteristic of a Golf cart "type" of battery? How do you know if you have them or not if you bought a used rig? I do know that my MH has 4 6 volt batteries, each pair connected in series to provide the desired 12 volts. Does being 6 volt make them, by definition, Golf cart batteries? Or is there some additional characteristic needed before they qualify as Golf cart type?

thx...
-- jcw

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Most 6 volt batteries that are about the size of a group 27 car battery are golf cart batteries.  The real ones are just a bit taller than a group 27 battery since that is how big the place you put them in a golf cart is.   At that size the plates can be really thick for a 6 volt battery which is better for deep cycling so that is why they are prefered to 12 volt batteries.   If you have room for the really big batteries, the kind that take two people to lift, they make great deep cycle 12 volt batteries.

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Bill Joyce,
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Our previous coach had 4 Trojan T-105, 6 volt batteries. They lasted for 6 years before the capacity diminished sufficiently to warrant replacement. I replaced them at a cost of $75.00 each. Pretty expensive but if you divide the cost by the 6 years of life things change a bit. Trojan T-105's are commercial golf cart batteries. A good multistage charger is a must. One that is temperature compensated would be better as charging rates vary with temperature. Complicated ain't it!!!!

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Standard sizing is the most general defining characteristic. Measure the space you have for batteries, pay particular attention to height, and get the biggest battery you can fit. If you have the height, floor polisher batteries would be super sweet as they are about the width/length of a grp 27 but twice the height and at 6v have more amp-hr capacity than Texas.

It is better to minimize parallel connections (they cause batteries to feed on each other) and maximize series. Hence, 2 x 6v in series is far far better than 2 x 12v in parallel. Therefore, 2 sets of (2 x 6v in series) in parellel is better than 4 x 12v in parralel. And so on.

Further, wire size in 12v is far more critical than at 120v. Wire losses (aka line losses) are far greater at lower voltages so in every connection on batteries and for longer runs (yes, just 3' is a long battery or primary charging wire run) always opt for the larger wire size.

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After more than 100 days of dry camping since our last post, we still need to water the batteries every 7 or 8 days or some cells will go dry within two weeks.  Not so convenient but still functional.  Expect to replace them soon but amazing that regular maintenance has allowed us to use about 100 amp hours a day without any real problems with the solar making up the difference every day but 2 of the 100.

Thanks for the advice Bill and others.

Soon to be fulltimers (June 2008) but can't sell the house yet.  Child wants to use the house as a dorm. We will need some luck with that.  But we won't be going to the house much if at all except to visit.

Larry and Jacki

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Roy


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I have 4 6 volt Trojan 105 batteries in my MH. We have been dry camping for 8 days now and I have to run my generator twice per day for 1 to 1 1/2 hours to keep it at 12 volts. I have a Xantrex inverter and a converter that charges in three stages--I presume.
Our MH is only 16months old and I feel like the batteries should last longer. We can run our flat screen TV, satellite and one or 2 12 volt lights for about 3 hours before we drop to 12 volts.
How do you program your charger to charge to a higher voltage? Mine seems to reach 14.3 briefly, but drops to 12.8 and then starts downhill when we turn on the TV and light.
Thanks for any help

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Roy,
The first step is to get a handle on your usage in terms of amp hours taken from your battery bank.  Using the power rating on each device you use and calculating the equivalent DC amps used will give you a high estimate of usage assuming there aren't devices using power that you don't know about.  We are very conservative using LCD TV, flourescent lighting when dry camping, and relatively small inverters when we are able for special uses like my CPAP machine.  We use about 60-80 amp hours a day which are easily replaced with the solar panels on a sunny day.

The second step is to get a handle on charge efficiency by measuring the current output to the batteries.  A DC clamp on current meter is the easiest tool but requires a special tool.  We found that our small generater with the house converter would take about 4 hours a day to charge our batteries from 65% to 85-90% of full charge.  It would take another 4 hours to get to 95% and I think our normal house loads would prevent us from ever getting to 100% with this charge configuration.  This is because the charger becomes less efficient as the battery voltage increases.  At 65% we get around 20 amps going into the batteries but by the time we get to 85% the charge current has dropped to less than 7 amps.  We could improve our charger configuration but we opted for Solar for other reasons.

Many RVers use a power moniter tracking current in and current out of the batteries.

Notice that I haven't mentioned voltage readings.  Accurate indications of battery status with votage readings is tricky and time consuming.  Many bloggers including some contributing on this forum have detailed discussions on all the ins and outs of battery monitoring.  Check out RVDUDE's BLOG for one.

Hope this gets you started.  Others will undoubtedly have more to say.

Larry and Jacki

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Every inverter/charger has a manual but they don't all let you change charging characteristics.   I can change about anything on the charging for my Prosine 2.0 but have seen big inverter/chargers that are fixed to 25AMP charging and standard wet cells without buying an upgraded control panel.  If you have a Xantrex RG6 control panel you need to get an RG7 to change the charger.  You also probably need a temparature sensor because your charging voltages should change by temparature, called "temparature compensation". 
Once you can change your charging characteristics then you go to Trojan's website and get their recommendations for settings.  Then you get out your multi-meter or add a battery monitor (I think this is essential if you dry camp a lot).  The multi-meter or battery monitor is to make sure when you set 14.6 on the charger you get 14.6 at the battery, you might be loosing some voltage due to wiring.  If you get 14.5 instead of 14.6 then set the charger to 14.7 to compensate.
Now 4 golf cart batteries, which is what a T105 is, are adequate for a motorhome but not really enough power at about 450 amp-hours.  When you are fully charged run the microwave on the inverter and see what drawing 150AMPs does to your voltage, it will likely drop under 12 volts.  Realize you can only pull 225 or less amp-hours out of the batteries before you have to charge them or you will be replacing them often.  225 amp-hours is not really a lot of power.  Most motorhomes have between 3 and 7 amps of phantom loads from the fridge (they still use 12 volt when running on LP), sensors, etc.  3 amps times 24 hours is 72 amp-hours and 7 amps of phantom load is 168 amp-hours.  Now turn on the inverter, you get more phantom load and the inverter is not 100% efficient.  It does not take long to use up 200 or more amp-hours.

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The first 12V Marine RV battery finally died after 4 years of fairly heavy use.  It's time to replace the bank with Golf Cart Batteries.  We should get some improved performance with our Solar and definitely require less frequent maintenance.

Larry and Jacki



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Well we finally installed four new Interstate GC2 6VDC deep cycle batteries before heading out to Heron Lake for several weeks of dry camping.  We did get tired of watering the 12VDC Marine batteries every week but they held up for several months of heavy use even though they were old and degraded.  We are looking forward to a much longer life and better performance out of batteries designed to do the job.

Happy camping.
Larry and Jacki

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