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6 VOLT BATTERIES, MINIMUM VOLTAGE

LVJJJ
Explorer
Explorer
I used to know this but don't remember much anymore.

I'm using two 6 volt golf cart type batteries in my 2005 Trail Cruiser. How low can I let the batteries run down? Right now I'm testing how long they will run the furnace in anticipation of several days boondocking. I run the furnace all the time adjusting it for day and night.

After 4 days the voltage is 11.3 while the furnace is running but jumps back up to 11.8 when it stops. Am I ruining the batteries at 11.3?
1994 GMC Suburban K1500
2005 Trail Cruiser TC26QBC
1965 CHEVY VAN, 292 "Big Block 6" (will still tow)
2008 HHR
L(Larry)V(Vicki)J(Jennifer)J(Jesse)J(Jason)
20 REPLIES 20

dodge_guy
Explorer II
Explorer II
From my research AGM batteries can go to 11V But FLA batteries should never drop below 11.5V.
Wife Kim
Son Brandon 17yrs
Daughter Marissa 16yrs
Dog Bailey

12 Forest River Georgetown 350TS Hellwig sway bars, BlueOx TrueCenter stabilizer

13 Ford Explorer Roadmaster Stowmaster 5000, VIP Tow>
A bad day camping is
better than a good day at work!

time2roll
Nomad
Nomad
TBammer wrote:
What type of test is needed to check if the battery might have been abused in the past? Asking for friend.
I would start with a hydrometer.

ktmrfs
Explorer
Explorer
Boon Docker wrote:
ktmrfs wrote:
Boon Docker wrote:
This info will help your friend.
TBammer wrote:
What type of test is needed to check if the battery might have been abused in the past? Asking for friend.


good info for 12V starting batteries and maybe marine/rv but not really valid for a GC2 battery. One, GC2 seldom if every have a CCA rating to use as a benchmark, Next They have a few very thick plates to much more internal resistance than a starting or marine battery. End result is if you try to load them to the typical load test, results in almost all cases will be "fail" even on brand new GC2. Unless the GC2 mfg gives a recomended load test current.

My experience is that loading a GC2 to between 1/2 and rated rated AH (60-100A on a typical GC2) gives some valid info,


I don't see anywhere that he mentioned a GC2.


nope he doesn't mention ANY info on battery type, so may as well give him info relevant enough to the two common battery types, 6V GC or 12V marine.

and the OP started the discussion stating he is using GC2 batteries.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!

Boon_Docker
Explorer II
Explorer II
ktmrfs wrote:
Boon Docker wrote:
This info will help your friend.
TBammer wrote:
What type of test is needed to check if the battery might have been abused in the past? Asking for friend.


good info for 12V starting batteries and maybe marine/rv but not really valid for a GC2 battery. One, GC2 seldom if every have a CCA rating to use as a benchmark, Next They have a few very thick plates to much more internal resistance than a starting or marine battery. End result is if you try to load them to the typical load test, results in almost all cases will be "fail" even on brand new GC2. Unless the GC2 mfg gives a recomended load test current.

My experience is that loading a GC2 to between 1/2 and rated rated AH (60-100A on a typical GC2) gives some valid info,


I don't see anywhere that he mentioned a GC2.

ktmrfs
Explorer
Explorer
Boon Docker wrote:
This info will help your friend.
TBammer wrote:
What type of test is needed to check if the battery might have been abused in the past? Asking for friend.


good info for 12V starting batteries and maybe marine/rv but not really valid for a GC2 battery. One, GC2 seldom if every have a CCA rating to use as a benchmark, Next They have a few very thick plates to much more internal resistance than a starting or marine battery. End result is if you try to load them to the typical load test, results in almost all cases will be "fail" even on brand new GC2. Unless the GC2 mfg gives a recomended load test current.

My experience is that loading a GC2 to between 1/2 and rated rated AH (60-100A on a typical GC2) gives some valid info,
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!

Boon_Docker
Explorer II
Explorer II
This info will help your friend.
TBammer wrote:
What type of test is needed to check if the battery might have been abused in the past? Asking for friend.

ktmrfs
Explorer
Explorer
TBammer wrote:
What type of test is needed to check if the battery might have been abused in the past? Asking for friend.


My battery testing method I use at the start of each year is to use a GOOD charger to equalize the batteries making sure they are fully charged and each cell equalized. Note.... The typical WFCO charger commonly used in trailers will NOT fully charge, let alone equalize the battery. A Progressive dyanamics or Iota can.

Then for the specific battery, go to the mfg web site and see what they indicate for battery specific gravity (SG) and at what temperture.

Then with a calibrated hygrometer that has a temp compensation chart (not the cheapie at the local parts store) Friese (sp?) makes an excellent one. measure EACH cells SG and write it down. Then compare that to what the mfg says the NEW SG should be. If each cell is about the same reading and close to the spec'd SG, your good to go with a battery near tip top shape.

If one or more cells is much lower than the others try another equalizing charge, if it doesn't change, you've got weak cells and the battery is on it's way out.

if all cells are low, again your nearing battery end of life.

Note: I didn't mention doing a load test. On GC2 batteries load test is of very marginal use. GC2 are NOT designed for high loads like a starting battery so (1) if load testing a GC2 you don't want to use the common X times AH as the load, you'll be WAY over a valid test and (2) If the mfg does give a current load for a load test you can try it if you can find a adjustable load tester.

I've never tried to load test a 12V marine/rv/starting battery so I have no clue as to how valid a load test is on such a battery.

And as a check with the battery AH rating for 20 or 24hours, and if you have a load that would match that AH rating (AH/20) you could run a load on it and check resting voltage at 6hours and 12 hours to see how close you are to 75% and 50% SOC. If at 6 hours your below the 75% SOC, don't go a full 12 hours, go say 8 measure again, if not at 50% continue. in the end you should have an idea of battery AH capacity vs. rated and an idea of battery condition.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!

TBammer
Explorer
Explorer
What type of test is needed to check if the battery might have been abused in the past? Asking for friend.
2016 Chevy 2500 HD, 6.0 gasser, 4.10 dif
2019 Arctic Fox 25W
Reese Pro-Series WD Hitch

Lwiddis
Explorer II
Explorer II
"Right now I'm testing how long they will run the furnace in anticipation of several days boondocking."

Experiment away but if you are not refilling your wet batteries daily their life will be shortened. 11.75 volts resting is about 30%...another battery life shortening event.
Winnebago 2101DS TT & 2022 Chevy Silverado 1500 LTZ Z71, WindyNation 300 watt solar-Lossigy 200 AH Lithium battery. Prefer boondocking, USFS, COE, BLM, NPS, TVA, state camps. Bicyclist. 14 yr. Army -11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad

jdc1
Explorer II
Explorer II
BarneyS wrote:
This might be helpful to somebody.
It was taken from The 12 volt side of life.



This should be printed on every deep cycle battery.

ajriding
Explorer
Explorer
My batteries will usually be below 12 by morning. I used to camp / boondock a lot when I used it for work, but use much less now. Batteries are maybe 8 years old, and still going strong. They are GC batts.
The answer is not absolute. There is a balance between using the batteries for your needs, conserving voltage to "save" the batteries, and the fact that you likely will not use them enough to cycle through the life supply of what they can do in a reasonable amount of years.
Most RVers will need 20 years to cycle through half of the available cycles a battery can do. I think 20 years the battery will die of other causes than life cycles first. You have to know what your needs are. A full-time RVer who uses a lot of battery power will need to be judicious with his power use, where a weekender can ignore largely what he does.

BarneyS
Explorer III
Explorer III
This might be helpful to somebody.
It was taken from The 12 volt side of life.

2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine

StirCrazy
Navigator
Navigator
ktmrfs wrote:
Boon Docker wrote:
Yes, you are killing your batteries.
11.8 is 30% SOC
Should never let the batteries get below 12.1 (50% SOC)


big misconception on never going below 50%SOC. A good rule of thumb for 12V RV/marine but not for a GC2 true deep discharge battery.

Many many many GC2 batteries are speced for hundreds of charge discharge cycles down to 25% SOC. IIRC the common garden variety Trojan T105 is spec'd for 500 charge discharge cycles down to 25% SOC, and they define end of life at something near 75% of spec'd new capacity.

I have two trailers, one a 2004 the other a 2010, both have had GC2's in them they both get 25+ cycles/year down to near 25% SOC and the 2004 I replaced the batteries and passed them to a friend at 10 years, he got a few more year out of them. the 2010 trailer still has the original batteries. So far I have run 3 sets of GC2's each with 250+ charge discharge cycles to 25%SOC plus many to around 50% and still were meeting my needs. The important thing is do NOT leave them discharged for more than a few days, get them FULLY charged (and that means do NOT rely on the common WFCO charger in trailers it will NEVER get them fully charged)

Not to the OP, get a good battery monitor that will measure actual discharge/charge amp hours, don't rely on battery voltage to determine an accurate state of charge.


it is and it isn't yes there spected down there and that draw is what there life is based on, but by keeping it above 50% when using them you can extend there life. thats where this is comining from, to get the most ife out of them. for example I had four 240Ah GC batteries in my 5th wheel that I justy replaced after 13 years. going down to 20 or 24 or 30% I would have never got that life out of them, maybe 5 years if I was luckey.

Steve
2014 F350 6.7 Platinum
2016 Cougar 330RBK
1991 Slumberqueen WS100

Skibane
Explorer II
Explorer II
ktmrfs wrote:
even the venerable std t105 gives 700 ish cycles at 75% DOD


Yep.

House batteries are a consumable item - You use them for a while, and then you get new ones.

They aren't designed to last forever.

If I was able to get 75% of a battery's rated capacity out of it 700+ times, I'd be perfectly happy.