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jmowrey

Best Coach Battery?

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I know little or nothing about batteries and am very challenged in the area of electrical knowledge. What is the best, most powerful and long-lasting 12v coach battery I can buy? I am looking at this one. 125 AH deep cycle sealed. I will have to modify my battery compartment/box to fit this (basically I'll just be cutting the back out of the plastic box because this battery is too long), but since it's sealed I will no longer be concerned with fumes. I use a 100watt solar panel w/controller and a 1100 watt inverter (inverter is wired directly to the battery). I assume this battery will be fine for those elements. But will the electrical/charging system in my 1985 Dolphin be able to charge this and use it as a power source for the 12v stuff in the coach?

Thanks for any and all input and suggestions.

http://www.ebay.com/itm/SLR125-VMAX-Sealed-Solar-AGM-Battery-12-Volt-Deep-Cycle-Mobile-home-RV-125AH-/281872564966?hash=item41a0ea02e6:g:iHsAAOxyBjBTQqTF&_trksid=p2349526.m3874.l7936

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I'm not trying to be a wise-a*s, but "best" and "longest lasting" can mean very different things.  To me, it's all about the best bang for the buck.  I figure I will be using batteries for as long as I live.  Thus, I figure any battery has a cost per year.   There is no battery I know of that is more cost-efficient then a Walmart Marine-type deep-cycle type 24, 27, or 29.  There are other batteries that will last 2,3, and even four times longer and they are priced sometimes 10 times more.    RVs do not have any special needs that requires special batteries.  Like ultra lightweight lithiums, or leak-proof AGMs and they all cost a lot more then standard flooded-lead-acid batteries like the ones I mentioned from Walmart.  Some AGMs do not last any longer then standard batteries but you never have to add water to them and the terminals stay cleaner.  Not something I'm going to pay twice the price for.  The other nice thing about the Walmart batteries is they are 12 volt.  That means they can be popped out and used  in something else if wanted.  One of my "house" batteries goes into a diesel tractor every winter that I keep a 6 foot snowblower on.

The AGM battery you linked to cost more then 2 1/2 times what a Walmart battery costs with the same reserve power.  Chances are - that AGM won't last any longer.  Also if you have any warranty issues - I bet it is difficult to pursue them. I see no advantage other then it makes your wallet lighter.  Now - if the seller gave you an unconditional 12 year warranty - I might feel otherwise.

I did not mention golf-cart type 6 volt batteries that also give a lot of "bang for the buck."  One reason being you must have two. One will not work.

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"The AGM battery you linked to cost more then 2 1/2 times what a Walmart battery costs with the same reserve power."

Thanks jd. Like I said, I'm pretty challenged on this subject. So when you say the same "reserve power," what measure are you referring to? I was assuming a 125ah battery would give me a lot more hours of usage before needing a charge than say a 35ah battery. I'm not seeing any 125 ah batteries at WalMart's site. They have one 110ah battery but it's in the $250 range. But I could be all wrong about this and am looking at the wrong number to measure the actual power in the battery available between charges. What I want is a battery that will get me through the a few days of sunless boon docking when I can't get a solar boost. I run lights, water pump and a couple of small fans on occasion. Also a toaster via my inverter (big draw, but for a very short period).  

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In theory, a "125 amp-hour" battery can steadily supply one amp for 125 hours before it is dead (about 5 days).  The Walmart type 27 battery is rated at 115 amp-hours (4.8 days). Note those numbers are often fudged a little but it gives you something to compare with.   It looks like the Walmart battery gives near the same power over the same amount of time as the AGM you posted the link to.

To be truly accurate - the amp-hour rate is supposed to expressed along with the hour-rate.   There is a 20 hour, 30 hour, 40 hour rate, etc.  Usually when a battery maker says a battery is - let's say a 125 amp-hour battery it means it is tested at the 20 hour rate.  But since that seller does not give those specs - it is hard to know for sure what it really does.

I find the actual weight of the battery is pretty good indicator of reserve power.   That one you linked to is 79 lbs. and the Walmart battery is around 62 lbs.  So it sounds like that AGM is a little bit more battery. Not 2 1/2 times more though.  I use a pair of Walmart batteries in my rig and I have never come close to running them down.  If I was running an AC refrigerator, I'd want two to be safe.  It all depends on how much camping/parking you plan on doing when no shore-power is available.   My family never camps where there is shore-power but we only camp at night and drive during the day.   I had another RV that I had an AC refrigerator in along with dual batteries.  Never had any issues.  One might of been OK, but it depends on how you use your RV.  Some RV refrigerators called "12 volt" are actually just AC refrigerators with a small inverter built into the back and came in many RVs OEM.

One added comment. Deep-cycle batteries tend to have their reserve-power expressed in "amp-hours."   Cranking batteries express reserve power in RC "reserve capacity."  You can use math to convert one number into the other.

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Yeah I use Walmart batteries too. Last a very long time. all of mine lasted 5 years or more.

Linda S

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if you do not have a newer modern converter charger. the flooded batterys are more able withstand crude battery chargers. and can be opened to replace water loss.

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I went with 2 6v in series for 480 ah storage. I had to make a new battery box out of storage bins but now I have lots of reserve power. Also an inverter for my CPAP. In a pinch I can use 12v to run my fridge if need be for the night and it will run my TV and charge my laptop and then recharge when driving or charge with the generator and my 50 amp power max  converter. 

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7 hours ago, zulandio said:

I went with 2 6v in series for 480 ah storage. I had to make a new battery box out of storage bins but now I have lots of reserve power. Also an inverter for my CPAP. In a pinch I can use 12v to run my fridge if need be for the night and it will run my TV and charge my laptop and then recharge when driving or charge with the generator and my 50 amp power max  converter. 

WHAT??  What model 6 volt battery has 480 amp-hours?  Each one must weigh around 130 lbs.   Or are you adding the two together?  THAT does not work.  One 6 volt battery like a Trojan T-105 is rated at 225 amp-hours.  When you put two of them together in series to make 12 volts - it is still only 225 amp-hours.  NOT 450 amp-hours.

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1 hour ago, jdemaris said:

WHAT??  What model 6 volt battery has 480 amp-hours?  Each one must weigh around 130 lbs.   Or are you adding the two together?  THAT does not work.  One 6 volt battery like a Trojan T-105 is rated at 225 amp-hours.  When you put two of them together in series to make 12 volts - it is still only 225 amp-hours.  NOT 450 amp-hours.

:blink: oh crap your right how did I miss that... Okay so I only have 235 AH..  Kind feeling stupid now.. 

At least 6v were cheaper for the AH I got. I paid $260 total for both. Online it's about that for Trojan 12v with 225ah but then you have to pay shipping and warranty claims get expensive so I guess I still went with the best setup for my wanted system.. 

 

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Yes, I wanted some Trojan T-105 equivalents a while back. BCI group GC2.   Sams Club had them for $83 each.  If that place was closer, I would of gotten them.  But since it would of been a 240 mile trip, I went to a local Walmart and got their 12 volt batteries instead.

sams_club.jpg

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I have two 7 year old 225 AH AGM batteries in my RV, they are awesome. They do every thing they are supposed to. They are mounted inside in a heated space so they will deliver full rated power in the winter. I have an AGM rated charger.

The OSHA nannies now say that they must be vented in case of an overcharge. when I bought them unvented mounting was OK so that's how they are. No problems with the proper charger.

I bought them for a screaming good deal and when they die, I will probably replace them the T-105 subs that JDE posted simply because of $$$. I'll need to find a new mounting space so I can do the water thing every so often. Sure gonna miss the AGM when that comes around

 

 

 

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1 hour ago, WME said:

."I have an AGM rated charger."

Is this something you upgraded in your system? Should I assume my stock charging system in my 1985 Dolphin will not be adequate for AGM batteries?

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Just now, jmowrey said:

Is this something you upgraded in your system? Should I assume my stock charging system in my 1985 Dolphin will not be adequate for AGM batteries?

Stock chargers from that era are rough on batteries from what I understand. They only charge at one voltage modern converters have 3 or 4 levels of charge. The final being trickle which is easier on batteries once fully charged.

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46 minutes ago, jmowrey said:

Is this something you upgraded in your system? Should I assume my stock charging system in my 1985 Dolphin will not be adequate for AGM batteries?

Your stock Toyota charging system is fine.  It makes no difference if a conventional flooded-lead-acid battery or an AGM.  Auto alternators do NOT just charge at one setting.  They try to maintain 14.2 volts and the charge-rate varies by the demand.  Those 3 or 4 stage battery maintainers do the same except once the battery reaches 14.2 volts, they switch to a  low "trickle-charge" voltage of around 13.8 volts.  Since most RVs spend more time parked then driving - the alternator is fine when doing the driving part.  When parked - a maintenance charger is what you need if you want your battery to last.  All batteries "self-discharge."  That means they go dead on their own, even if not hooked to anything.  Thus the reason why a maintenance charger is needed for best battery life.

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Let me clarify. I am talking about the Denso alternator charging both your batteries when driving. Not what your on-board charger does that runs on shore-power IF you even have one.

My own opinion is a dual-output 10 amp marine-charger is the way to go.  Mine is hardwired in.  It charges all three of batteries whenever my Toyota RV is in storage. One cranking battery and two "house" batteries.   When I got mine a few years ago, "Guest" was the brand-name.  Since then, it has changed to Marinco.  Here's what it looks like mounted under the couch in my 1988 Minicruiser.

Marino dual bank.jpg

annotated.JPG

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43 minutes ago, jdemaris said:

Your stock Toyota charging system is fine.  It makes no difference if a conventional flooded-lead-acid battery or an AGM.  Auto alternators do NOT just charge at one setting.  They try to maintain 14.2 volts and the charge-rate varies by the demand.  Those 3 or 4 stage battery maintainers do the same except once the battery reaches 14.2 volts, they switch to a  low "trickle-charge" voltage of around 13.8 volts.  Since most RVs spend more time parked then driving - the alternator is fine when doing the driving part.  When parked - a maintenance charger is what you need if you want your battery to last.  All batteries "self-discharge."  That means they go dead on their own, even if not hooked to anything.  Thus the reason why a maintenance charger is needed for best battery life.

I used a dual controller when I set up my solar system which I wired to both my coach and cab batteries. It allows for adjustment as to how much juice is going to each battery. When I'm using the RV it is set to charge the coach battery only. During non-use times I set it to 50-50. My solar panel is not mounted. I can move it around on a cable which comes out of the shore-power access door. I prop the panel up outside the carport wall so it receives plenty of morning sun. Both my coach battery and my cab battery receive a maintenance charge every day. Especially useful during the winter months here in Santa Fe.

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I like KISS.  I go with walmart lead acid deep cycle batteries - a 24 or 27 fits in my battery box. 

 

As for powering your cab, not sure why you would want to do that , but if you put a jumper on your isolator solenoid (mine is on the passenger side fender well under the hood) you could backfeed 12vdc to the start battery,  If I turn the ignition switch to the on (run) position, the jumper would be redundant.

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11 hours ago, DanAatTheCape said:

I like KISS.  I go with walmart lead acid deep cycle batteries - a 24 or 27 fits in my battery box. 

 

As for powering your cab, not sure why you would want to do that , but if you put a jumper on your isolator solenoid (mine is on the passenger side fender well under the hood) you could backfeed 12vdc to the start battery,  If I turn the ignition switch to the on (run) position, the jumper would be redundant.

I use the dual controller to provide a trickle charge to the both the cab battery and the coach battery when the vehicle is idle for lengths of time. Otherwise, when we are using the Dolphin, the controller can be switched to provide 100% of the solar charge to the coach battery. This setup maintains both batteries throughout the winter when the Dolphin is in storage at my home.

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35 minutes ago, jmowrey said:

I use the dual controller to provide a trickle charge to the both the cab battery and the coach battery when the vehicle is idle for lengths of time. Otherwise, when we are using the Dolphin, the controller can be switched to provide 100% of the solar charge to the coach battery. This setup maintains both batteries throughout the winter when the Dolphin is in storage at my home.

Solar is good - I just have not gone that deep yet.  I use a honda 2000 if not plugged into shore power.  

On the subject of non fossil fuel power, has anyone seen a wind turbine configured with a Toy?

 

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If you replace the converter/charger you kill two birds they are efficient well regulated, have a disulfide and float charge no need for any other type of charger they can be left on indefinitely. If you add a combiner to the mix (easy replacement of the relay type isolator) it will charge the truck battery also and still work as an isolator.

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On 9/23/2016 at 1:30 PM, WME said:

I have two 7 year old 225 AH AGM batteries in my RV, they are awesome. They do every thing they are supposed to. They are mounted inside in a heated space so they will deliver full rated power in the winter. I have an AGM rated charger.

The OSHA nannies now say that they must be vented in case of an overcharge. when I bought them unvented mounting was OK so that's how they are. No problems with the proper charger.

I bought them for a screaming good deal and when they die, I will probably replace them the T-105 subs that JDE posted simply because of $$$. I'll need to find a new mounting space so I can do the water thing every so often. Sure gonna miss the AGM when that comes around

 

 

 

The AMG batteries are valve regulated and usually do not "vent" unless over charged. Venting batteries is not a bad ideal they do produce hydrogen gas (remember the Hindenburg) during charging all though the AMG's do mostly trap it. We were using 225 AH AMG's in the cop cars worked great not cheap but worth it.

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Does anyone have a current recommendation for a coach battery replacement?

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Basically there are only 3 major battery makers there are quite a few rebranded ones but it boils down to just 3 manufactures. If you know what you want for size etc. the next trick is pick them up, buy the heaviest one of the same size. Walmart actually does a good job with their batteries pretty good about returns etc.

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Ok great thank you Linda and Maineah. 

I have used interstate DC in my previous rigs.  That WalMart battery looks like a similar piece.   

 

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