Battery Drain

Hi Scott & Jim:

I am with Jim on this. I am not a big fan of automatic isolators. They look for a voltage +/- to decide whether to connect or isolate. Then, this voltage drop becomes part of what the charger (converter) sees and will affect charge rate and full charge calculation by the charger. I am in the KISS camp. I will tell the battery charger which battery to charge :).

Rob
 
Whether or not I would personally endorse an automatic battery isolater is highly dependent on which type. The oldest kid on the block simply works off of the ignition switch and is basic and simple. The batteries stay isolated until the the ignition switch is energized and pulls in a solenoid that connects the aux battery to the charging circuit. Problem with these is if your aux battery is run down they add a lot of load to the charging circuit right after an engine start. Not only are you charging the start battery at a high current recovering from a start cycle you are adding the charge of the depleted aux battery to the load.

Second type uses blocking diodes that do have a voltage drop and will result in both batteries being undercharged by a half volt or more.

Third type I would endorse if you felt you needed to go this route. They have no voltage drop. It's circuits sense the voltage of both batteries and will not close the solenoid to connect the aux battery to the charging circuit until the start battery is sufficiently recovered. Some are simple with predetermined cut in and cut out voltages and others are programable and not only work as described above during the start sequence but can also be set up to where you can determine a set level of charge you want to maintain in the start battery and have it connected along with your aux battery to power your loads while the charging source is not present then cut out once you have reached your predetermined setting to reserve the remainder for starting. The only added current draw from these types is the very small amount for the monitoring circuit and what's being used to energize the solenoid.

For me a good old fashion rotary switch is all I need much like already mentioned. One, Two, Both or none for a total disconnect.
 
Finally got our 303 out of indoor storage today out of the sod hut after shoveling the snow drift and chasing off the buffalo and the battery was in the same 3/4 charge indicator level as when we put it in storage at the end of October 2014 (7 1/2 months ago!!!!!!!!) This was a wonderful find !....appeared to be no parasitic drain. The front landing gear powered up and down just fine, lights shone brightly like GDRV's cash flow statement, and my brakes seems to work well at 3.0 setting.

Dan
 
Hi Dan,

Sounds like a great start to your season !
I have stored my boat for years, with all 6 batteries fully charged and disconnected for 7 months . . . to find them all at 75% state of charge in the spring.
Brakes working well at "3" . . . don't think this will last once you wear off the rust :) . . . but probably indicates that you don't have the "greased brakes" problem.

Rob
 
Rob--yes with our boat our 2 batteries were the same as you share over the winter with a disconnect switch and the original interstates lasted 12 years !!! We rarely drained them fully only when cranking the tunes too long -- we had a Baja performance boat.

Dan
 
FWIW: I've had 3 RVs with solar charging panels and have left them stored outside in negative * F through multiple winters (in Elko, NV and Butte, MT), and 2 run of the mill deep cycle 12v batteries connected. Only the oldest unit has ever had the batteries replaced at 5+ years and we dry camp nearly always. I haven't done any measuring of state of charge but they've never let me down. I'm open to change if it makes sense. Whatcha think?

Again FWIW: the 2 original AC Delco batteries in my '05 Duramax are still going (until I said that). The truck is seldom driven with only 87k on the clock. Not my first good experience w/AC Delco batteries. I've tried Interstate, CAT, etc. with the Delco outliving them all. I've come to rely on Battery Minder units in the past couple years to de-sulfate/condition, etc. on 4-wheelers, mower, and the muscular car.
 
Dead Battery Mystery - Sulfation

Camped for 3 days a week ago.
We had pedestal power so we were plugged in with the shoreline the whole time.
This powered the converter and ensured the battery stayed at 100%.
But, two days after we came home I needed to check something in the rig and low and behold the battery was dead as dead can be.
8.5VDC and the disconnect in the basement was OFF too so there was very little if any parasitic current being used.
Since this Group 27 wet-cell battery was new only 4 months ago my oh crap sensor went off.
So I started doing some homework.
That led to this website: http://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html#3
I learned that all conditions are optimal for my battery to have sulfation build-up.
I took the battery out and brought it home and hooked it up to my Schumacher SSC-1000A battery charger and after 24 hours its fully charged again.
I have ordered a PulseTech PP-12-L battery maintainer (not a charger).
I will wire this in to my battery disconnect so that when my disconnect is OFF while in storage this maintainer will be off-line and not using battery power.
But, when I turn the disconnect on and use my rig then it will be online and pulsing to prevent sulfation build-up.
Will it work?
In reality I can't believe I have a sulfation problem after only 4 months, but I've checked everything and there is no logical explanation why my battery discharged in storage as fast as it did.
I may be in denial that my new battery has failed, but it charged and is holding OK and there is no indication of a shorted cell or something like that.
Time will tell, but if what they say about idle RV batteries becoming sulfated and reducing their capacity over time, then I am up to being proactive and get all I can out of of my battery.
I'm sure there is more to this story, but that is all for now.
Carry on.
 
Jamey & Peggy,
I'm not sure about the sulfated info, but what I have done on my last two units is put a knife switch type disconnect on the ground side of the battery and that really helps save my batteries. I will check out the site you listed for future reference. If I'm storing it for long periods of time (in the cold) I'll take it out and bring it inside and keep it charged.
 
Hi Jamey,

That is a very informative link ! Anyone wanting to know the facts about charging/discharging/maintaining batteries should read this carefully.

8.5V is a completely dead (well into the possible permanent damage zone) battery. Sulfation is a complex conclusion to what might be a much simpler cause. I would go back to the parasitic draw possibility. To draw a battery this low needs a continuous resistive load . . . like a light left on. I don't know about Solitudes, but on Reflections, there is a lot of stuff still powered up when the battery "disconnect" switch is turned off. Basically everything in the front compartment including landing gear and lighting is still powered. I would charge that battery to 100%, confirm by checking specific gravity of each cell and let it sit for two weeks completely disconnected from everything. Then, recheck specific gravity. If it is still at 99% state of charge (which it probably will be) go looking for that parasitic load.

Rob
 
As Rob ME stated that's a great read for battery maintenance but I'd highly doubt you are experiencing sulfate build up on a fairly new battery. I'd be looking at a parasitic draw or just a good old fashioned failed battery. A 5% infant mortality rate is the standard for the battery industry.

Rob EE
 
So, will a single 'full discharge' on a brand new battery significantly impact is lifespan?
And would it be a bad idea to add a second battery (bank of 2 6v in my case) to the bank that was discharged?

Don't know how it happened but the disconnect was left on without the RV plugged in. Either parasitic loads or the fridge if it works on DC.??

I'll look seriously at AGM when the time comes to replace these.
 
Depends on what you are calling a full discharge. A technical full discharge on a lead acid battery is 1.7V/cell or 10.2V on a 12v battery. Discharging below that does have a negative effect on the lifespan and ah rating. If it discharged to slap dead that battery will never recover. Adding new batteries to a bad string has been known to ruin the new batteries.

The fridge does draw battery power.
 
So, will a single 'full discharge' on a brand new battery significantly impact is lifespan?
And would it be a bad idea to add a second battery (bank of 2 6v in my case) to the bank that was discharged?

Don't know how it happened but the disconnect was left on without the RV plugged in. Either parasitic loads or the fridge if it works on DC.??

I'll look seriously at AGM when the time comes to replace these.


Hi Gary,

1) Will a single full discharge damage a battery ? . . . in theory yes . . . but worth trying a "save". Fully charge it, let it stabilize for a few days and measure the specific gravity of the water. This is the only way to know if the lead acid chemical reaction is working properly in every cell.

2) Adding a second battery . . . all batteries in a bank should be exactly the same brand/type/size/age. If you mix them up, the charger will get confused and overcharge the new batteries trying to bring the old ones up to full charge.

3) The fridge control circuits run on 12V, but the cooling comes from either shore power or propane.

4) AGM batteries are good for sailboats where they get laid on their sides on a regular basis. For applications where the batteries remain upright, it is difficult to justify the cost premium for AGM (in my opinion).

Rob
 
In the future you may want to look at using 2 6V batteries. The hold their charge better and have a higher amp hour rating than you deep cycle 12V batteries. They are more expansive but the last a lot longer than 12V Batteries. I had 6Volts batteries in my last trailer and they were still good after 6 years and possibly lasted longer if they hadn't frozen.
I could not get more than 2 or 3 years on the 12V batteries
 
Dumb question I'm sure but is there some issue keeping a trickle charger on the battery when stored? I kept one on my previous toy hauler for three years without any issues, never had any battery issues.
 
Most modern battery chargers (including the WFCO converters installed by Grand Design) have three stage charging which includes a Float (Trickle) charge mode. A fully charged battery will stay charged for many months if it is completely disconnected from all loads.

Rob
 
Maintenance Charging

I do not have the luxury of plugging my trailer into 120VAC when it is in storage between trips.
As a compromise I have two batteries.
One is installed in the trailer and the other is in my garage at home.
I flip flop them each trip.
The one in the garage is on a maintenance charger.
http://www.amazon.com/gp/product/B000O707IO?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00
I like the PulseTech XC100-P Xtreme Charge 12V Battery Maintenance Charger Desulfator because it does more than just keep the battery at 100%.
With the desulfating feature it also conditions my battery to extend its life.
Here is a link to a good resource about batteries.
http://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html
 
I also had a problem with the battery draining while parked and battery "isolated". I took it to a local auto-electrical shop and the told me the biggest draw - even while 'isolated' was the entertainment unit. He asked how important it was to retain all the items in memory, I responded "not at all" and he put a little toggle switch on the wall to the left of the component cabinet. Shuts off everything above the fireplace - problem solved. I also added another 12 V battery up front, and built a new 2-battery tray and got rid of that idiotic bin that requires that you be able to lift 50 - 60 lbs. straight up while on a 45 deg. angle. My 4 back surgeries say - nah!

Pat
 

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