Safe Level of Repeated Discharge of Deep Cell Battery?

[ToyoGuy]

Just finished a surprising discussion with an Interstate battery rep while chasing a charging problem. He seemed to have issue with deeply discharging (below 12v ?!)  deep-cell batteries on a regular basis. I thought this is what deep cell batteries were all about ! 

I am wondering how far down (in volts) boondocking folks with no solar or generators regularly discharge their coach battery with no problems?  When I'm out for 2 days and nights, with a non-Dometic 12v fridge, (rated 5.4amps @12v) it seems to me, I recall getting down to the 9-10 volt level. Yeah, the fridge quits at 10.4 vdc  but starts back up at 11.8, but by then on a 2 day trip,  I got no freezables anyway. Also seems to me that I used to just fire up the truck and head out, or let it charge for a while, but..... since some work at a different garage, I'm getting charging surges with brief Charge and Brake warning lights at the same time. Someone else mentioned suspicions of a battery-type failure within a single cell called "flashing". Never heard of this before.

Thanks for any input.

TG

Edited May 25, 2016 by ToyoGuy

[ToyoGuy]

OK,.. got it. 10.5 VDC = fully discharged at 77 degrees. Amazing what you can learn online !   Apparently, at 11.9 volts, I am down to a 40% state of charge. Lower than that, I'm just looking to buy replacement batteries sooner. Guess I'll have to reform and shape up my energy consumption habits. On to Operation Surge.

TG

[payaso del mar]

no wonder my house batteries in the Payasoroamer are chingado.  they sat at about 10 volts for several months one winter at our cabin (yes, PV panels can fail altho it's rare....and i got 2 bad ones) and now won't get over about 12.6 volts no matter what.

sounds like what you need is a lot more capacity.  given the weight issue we all face, i think Totem is onto something brilliant with his lithium battery-bank idea.....wish he'd post more info on that (hint, hint....). 

[zero]

2 hours ago, ToyoGuy said:

OK,.. got it. 10.5 VDC = fully discharged at 77 degrees. Amazing what you can learn online !   Apparently, at 11.9 volts, I am down to a 40% state of charge. Lower than that, I'm just looking to buy replacement batteries sooner. Guess I'll have to reform and shape up my energy consumption habits. On to Operation Surge.

TG

I have never seen that voltage posted by any battery maker.   The standard that all the companies agree on that I know of for a flooded lead acid battery @ 77 degrees F is:  

0% charge = 11.5 volts
20% charge = 11.7 volts
50% charge = 12.1 volts
80% charge = 12.5 volts
100% charge = 12.7 volts

That includes the specs from Johnson Controls who make Interstate batteries.    The tech department at Johnson Controls told me their type 27 deep-cycle battery that Interstate and Walmart sells - is rated to last through 250 complete, 100% discharges.  I would take the word of the place that makes the batteries over someone selling rebranded batteries like Interstate.

[DanAatTheCape]

I saw a video once on deep cycle batteries.  what did I get out of it?

1) A battery discharged 75% will get a lot fewer cycles than one discharged to 50%;

2) don't leave a battery discharged - keep them topped off.

[Totem]

this is why i am a fan of nicer charge controllers that have 12 volt service lines; tap from there they will shut down the service at 11.5.

Most if not all 12 v to 110 inverters today will also; which makes running 110 conversion chest freezers a nice option if the old 3 way is taking a dump.

Personally I will run my dometic until it no longer works on propane before i swap fridge tech; but that's me.

 

[ToyoGuy]

Yeah, on the reliability of those charging stats, I checked further and unfortunately, those stats and others ( I collected 5 different charts w/slightly different data) are simply taken from other websites and reproduced elsewhere. Thanks for your more-informed data jdemaris.. I did notice some of the charts mentioned measuring the state of charge with no loads being applied for 6 hours and some had no notes on such.  Here are a couple of the rest for any observations TG

 

 

Edited May 27, 2016 by ToyoGuy
Wrong chart

[Derek up North]

13 minutes ago, ToyoGuy said:

Here are a couple of the rest for any observations TG

My observation? I'm guessing the 5 charts you collected did not provide a source? Just like you didn't with yours.

[zero]

Depends on the make of battery and type of battery.   Yuasa says lower then 11.8 volts is dead for a FLA.  Trojan says 11.5 volts for their HD FLA, and 11.6 for their AGM. Here is some stuff with source-citations evident.

[ToyoGuy]

9 hours ago, Derek up North said:

My observation? I'm guessing the 5 charts you collected did not provide a source? Just like you didn't with yours.

Yeah, I copied the charts for my own use without bookmarking them and my weekly computer purge includes history so I couldn't quote (secondary) sources. But you're correct Derek, most of them were copied from elsewhere and not credited for primary source. I'll try to be more responsible about sourcing / reporting info in the future.   Ahhh,... torque wrench, crescent wrench, what's the difference !?  (Insert clown emoticon here)      TG

[Derek up North]

Don't feel you have to break the internet tradition for me.

Another of my favorite 'mystery' charts are the ones for ATF fluid temps/transmission life. None seem to be published by ATF manufacturers or transmission suppliers. Just by people with transmission coolers they're trying to sell. And of course no test procedures, just pretty charts with lots of colours.

[linda s]

I'm not much for measuring stuff. I just use it until it doesn't work anymore. I can't count the times I've forgotten and left my fridge on 12 volt and didn't have enough power left to even light one of those itty bitty 12 volt lights in the camper. Never killed a battery that way yet. They always have charged up and always last about 5 years with a lot of use. 100 bucks at Walmart makes the cost about 5 cents a day. Not something I can get myself all worked up about.

Linda S

[zero]

7 hours ago, Derek up North said:

 

Another of my favorite 'mystery' charts are the ones for ATF fluid temps/transmission life. None seem to be published by ATF manufacturers or transmission suppliers. Just by people with transmission coolers they're trying to sell. And of course no test procedures, just pretty charts with lots of colours.

Don't you realize that the validity of anything claimed on the Net is proven by how many times it is repeated and not by any source-citation?  If someone tells me one more time that "Google is my friend", I am going to puke.   Heck, even Google can't spell Googol right.  It's company name is based on the Net typo.

I was reading a Aisin/Toyota tech manual for an early automatic truck trans. A40 maybe?   Funny thing is it states there is no need to ever change the filter - ever, unless there is a catastrophy.   I don't see tran s makers saying that anymore.

I have a 2001 Chevy (Canadian Cami) Tracker with an Aisin A43DE.  The electronic lock-up version of the trans in my 1988 Toyota. As far as I know, it has 240,000 miles and the transmission fluid has never been changed.  I am going by the word of the original owner, so cannot prove that - but I DO believe it.

Big truck auto transmissions don't get routine trans fluid changes.  Oil gets checked and if OK, does not get touched.  Sometimes just gets an additive supplement with no change. 

I have gone by this simple, unscientific rule for all of my driving wrench-turning life. If a trans works good, and the oil looks good and does not smell burnt, I do not touch it.

On the subject of battery life . .  companys that sell to a more technical demanding crowd then the average consumer - HAVE to post reliable battery life projections or they would be out of business.  Like this from Trojan battery. Note the projected 750 life cycles of 100% discharges.  THAT is a lot.

[Totem]

Here's one for jde... Pulled the backseat of my Mercedes diesel 1998 e300td out to check its battery today , something I've never done before. Battery was a gigantic Benz oem battery born on date code of 11/27/1996... Voltage reading is 12.5 at rest... Holy crap!  It drops to 11.7 while lighting up the glow plugs... Jde should I keep this thing or replace? Also.. It appears to be a maintenance battery; one water should be checked in... Was amazed not only that it was in the back seat with 0 gauge copper wire runs but also that it's a 1996 battery! 

Edited May 28, 2016 by Totem