Asked OReilly's about testing the 6V batteries and I might as well had two heads. I'm assuming 6 volt batteries can be tested similar to 12 volts? I haven't tried Napa yet and maybe that's the best route.. Has anyone had their 6V's tested? I'm noticing flickering in all the lights in our RV. Started around when the water got a little low in the batteries, the level was still above the plates. Just testing with a meter the voltages are still within spec and voltage drops are similar what it has been. Was planning on changing to lithium ion batteries, solar panels and upgrade the inverter this fall. Might not make it till then.
Testing 6V golf cart batteries
- Thread starter wander2039
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Get a hydrometer and do it yourself. Takes 2 min
They have a Midtronics tester that may not be able to test a 6V battery. I know my battery tester that is a $80 version of the Midtronics will not test a 6V battery. Certainly a carbon pile load tester can still put a load on the battery. As suggested a hydrometer is always a good way to test the batteries.
I used to have a bank of 6v golf cart batteries to run my sump pumps and tested them with a hydrometer, and frankly the SG measurements didn't provide much useful information that simple OCV didn't provide. unless I just don't understand how to interpret SG.
after a couple years service my GC batts tested perfectly fine via SG and OCV, but they totally failed to run the pumps. I got a load tester and sure enough they couldn't hold voltage with a 100A load.
I have since switched to Marine dual purpose batteries and they have worked flawlessly for 8+ years.
get a load tester. and swtich to marine batteries. The FVP M31-8DP at Menards is an absolute beast for $100 (with their 11% rebate). I have no idea who makes them, but they are tanks. and right now is the time to buy Menards has fresh stock for the upcoming boating season.
after a couple years service my GC batts tested perfectly fine via SG and OCV, but they totally failed to run the pumps. I got a load tester and sure enough they couldn't hold voltage with a 100A load.
I have since switched to Marine dual purpose batteries and they have worked flawlessly for 8+ years.
get a load tester. and swtich to marine batteries. The FVP M31-8DP at Menards is an absolute beast for $100 (with their 11% rebate). I have no idea who makes them, but they are tanks. and right now is the time to buy Menards has fresh stock for the upcoming boating season.
Unless the OP is planning to put a 100A load on his batteries, this may not be good advice for his situation. Marine batteries tend to be a compromise between ability to deep cycle and to start a motor. True deep cycle batteries (assuming they aren't broken and load test well) are going to be better for typical RV usage. I do get why a marine battery made sense for your sump pump scenario.
Of course, if the current 6V fail a load test, it's a good excuse to do the lithium upgrade.
yeah that was my thought process too when I first installed the GC2s. I got 4 of them --- 2 gangs of two in parallel for 12V @ 450Ahr. The pump draws 6A at 120Vac, so 60A at 12V, or 30A per battery, or 38 if you factor in efficiency. surely a GC2 can deliver 38A no problem right? they run golf carts all day... but not so in my case. and the pump was running at about 5% duty cycle, which is nothing compared to the constant draw of an RV with TV, fridge, AC, lights, etc which surely add up to more than 6A of 120V current. But if the GC2s couldn't reliably deliver 38A intermittently then how can they be expected to deliver even more power in perpetuity? I mean, without ganging many more of them in parallel.
in contrast the marine batteries have been rock solid. cycled down to 10.5V mutiple times. still as strong as when new. granted they are not discharged daily, but neither were the GC2s.
My inverter was a Triplite APS2012 (POS) and I suspect its charger didn't do the GC2s any favors, so that may have been part of the problem.
here's the current set up. they transfer swtiches are my own design.
A hydrometer will indicate state of charge, not state of health, or percentage of original capacity remaining.
I've had large batteries read 1.275+ on all cells and maintain 12.75 days off the charger, but would fall to 11 volts charging a cell phone.
GC-2s are not known for their ability to provide high amperages for high durations. They do not have a CCA figure, just like engine startig batteries rarely have am amp hour capacity figure
GC-2 batteries are all about deep cycle duty, and accumulating lots of deep cycles before failure, assuming they are returned to a true full charge regularly.
The Hydrometer is a great and irreplaceable tool in determining if one's charging source is capable of meeting this ideal.
Most would find their charging source lacking, if they bothered.
The thicker denser plates of GC-2 batteries, makes them more tolerant of forced overcharging.
Look into an Equalization charge. After a normal 'full charge' Apply ~5 amps per 100Ah of battery capacity until terminal voltage rises as high as 16.2 volts for as long as it takes specific gravity to stop rising. The electrolyte will warm up, and can appear to no longer be rising, until one accounts for the warmer electrolyte.
OTC4619
had a built in thermometer which says how much to add or subtract to the float's reading.
Give it a few seconds to absorb the heat of the electrolyte. Make sure no bubbles stick to the float.
I use a Meanwell rsp-500-15 for all charging. Manual charging, as automatic stops short of ideal.
It is a 40 amp adjustable voltage power supply capable of outputting 40 amps to maintain any chosen voltage, from 13.12 to 19.23 volts.
I've a digital ammeter on the output, and a 10 turn voltage dial
For a pair of GC-2's @ ~220 amp hours, you'd want a power supply capable of no less than 12 amps in order to bring them upto 16.2 v and perform the capacity restoring equalization charge.
Flooded group 31 batteries are a bit starved in the electrolyte department.
Marine 27/29 and 31's often need ridiculous times held at high absorption voltages in order for specific gravity to max out, and if perfectly recharged will daccumulate about 5 to 600 deep cycles to 50% SOC before capacity loss becomes too obvious to continue in deep cycle duty, and they take forever to reach full charge.
GC-2s , a true deep cycle battery will do 1200 to 1500 deep cycles if perfectly and promptly recharged to full. They often need less time to get from 95% to 100%, compared to flooded marine 24/27/29/31
Batteries designed for engine starting will last about 50 to 100 deep cycles, if promptly and fully recharged, after an unintentional deep cycle.
But there are tons of influencing variables such as age and manufacturer and depth of discharge and temperature and.......
Here are the guts of a 12v group 24 marine battery, compared to a 6v GC-2 battery:
source:
Recovering capacity on sulfated GC-2's is likely, with an EQ charge, as long as they have not sat 100% discharged for months on end.
The tools required to perform a proper 15.5v to 16.2v EQ charge, will allow one to get better lifespans from subsequent Lead acid battery banks, and perhaps also be able to charge Lifepo4's, depending on the BMS.
I've had large batteries read 1.275+ on all cells and maintain 12.75 days off the charger, but would fall to 11 volts charging a cell phone.
GC-2s are not known for their ability to provide high amperages for high durations. They do not have a CCA figure, just like engine startig batteries rarely have am amp hour capacity figure
GC-2 batteries are all about deep cycle duty, and accumulating lots of deep cycles before failure, assuming they are returned to a true full charge regularly.
The Hydrometer is a great and irreplaceable tool in determining if one's charging source is capable of meeting this ideal.
Most would find their charging source lacking, if they bothered.
The thicker denser plates of GC-2 batteries, makes them more tolerant of forced overcharging.
Look into an Equalization charge. After a normal 'full charge' Apply ~5 amps per 100Ah of battery capacity until terminal voltage rises as high as 16.2 volts for as long as it takes specific gravity to stop rising. The electrolyte will warm up, and can appear to no longer be rising, until one accounts for the warmer electrolyte.
OTC4619
had a built in thermometer which says how much to add or subtract to the float's reading.
Give it a few seconds to absorb the heat of the electrolyte. Make sure no bubbles stick to the float.
I use a Meanwell rsp-500-15 for all charging. Manual charging, as automatic stops short of ideal.
It is a 40 amp adjustable voltage power supply capable of outputting 40 amps to maintain any chosen voltage, from 13.12 to 19.23 volts.
I've a digital ammeter on the output, and a 10 turn voltage dial
For a pair of GC-2's @ ~220 amp hours, you'd want a power supply capable of no less than 12 amps in order to bring them upto 16.2 v and perform the capacity restoring equalization charge.
Flooded group 31 batteries are a bit starved in the electrolyte department.
Marine 27/29 and 31's often need ridiculous times held at high absorption voltages in order for specific gravity to max out, and if perfectly recharged will daccumulate about 5 to 600 deep cycles to 50% SOC before capacity loss becomes too obvious to continue in deep cycle duty, and they take forever to reach full charge.
GC-2s , a true deep cycle battery will do 1200 to 1500 deep cycles if perfectly and promptly recharged to full. They often need less time to get from 95% to 100%, compared to flooded marine 24/27/29/31
Batteries designed for engine starting will last about 50 to 100 deep cycles, if promptly and fully recharged, after an unintentional deep cycle.
But there are tons of influencing variables such as age and manufacturer and depth of discharge and temperature and.......
Here are the guts of a 12v group 24 marine battery, compared to a 6v GC-2 battery:
source:
What is a Deep Cycle Battery? - Marine How To
Light Cycle vs. Deeper Cycle NOTE: This article deals with FLOODED marine batteries, not AGM or GEL batteries. The Problem: The problem, as I see it, is one of dishonest marketing where multiple battery types wear the same clothes (sticker) and will perform differently when
marinehowto.com
Recovering capacity on sulfated GC-2's is likely, with an EQ charge, as long as they have not sat 100% discharged for months on end.
The tools required to perform a proper 15.5v to 16.2v EQ charge, will allow one to get better lifespans from subsequent Lead acid battery banks, and perhaps also be able to charge Lifepo4's, depending on the BMS.
ahh. so is that to say one should continue absorption or equalization charge until the SG stops rising? I always considered the 1.275 line on my hydrometer to be fully charged and there was no point in continuing to charge it once it reached that level --- which most of my batteries reach really quickly, even before absorption current tapers off. that always had me confused... what's the point of SG measurements if the battery is still sucking in absorption current when the SG reads fully charged??
its possible (likely) my GC2s were chronically undercharged by the Tripplite leading to their early death. for whatever reason the marine batts did not suffer the same fate. I no longer use the Tripplite and instead use separate stanley 3 stage chargers in the photo, they have worked very well for this.
Lot of good info in here. I'll see if any other places can load test 6vs. Don't have a hydrometer up here. The batteries are 6 years old have been charged by a 4 stage the entire 6 years. Never have been discharged too far.
to further expand on my experience using hyrdrometers... for grins I did a test this afternoon with my primary sump pump system --- the bottom one in the photo with the 3 group 29 marine batteries dated 1/2014. unplugged the transfer switch, removed the charger, and let it run on battery inverter power for 2 hours. with the snow melt here the pump is currently running every 2mins 50sec. while cycling it runs for 18sec drawing 75A from the triple battery bank. by my math:
18s/3600s * 75A = 0.375Ahr every cycle * 20 cycles per hour * 2hrs = 15Ahr consumed during test. The grp 29 batts are rated at 122Ahr, but at 75A draw its certainly more like 90Ahr each ==> 270Ahr for the bank ==> (270-15)/270= about 95% SOC after 2 hours.
SG measured with hydrometer after 2 hour test = 1.275 maybe just a smidge below == FULL CHARGE.
OCV at end of 2 hour test == 12.7V exactly.
So, batteries still *fully charged* after 2 hours of use... BUT WAIT...
I reconnect the Stanley BC25BS charger and it immediately pegs at 25A charge current @14V and holds there for 10mins or so, then gradually tapers off over the next 2 hours to 1.7A and then finally goes into Float mode at 13.6V.
So... 1.275 SG and 12.7V and the batteries still took 2 hours to charge with a 25A charger.
This is why I stopped using my hydrometer.
18s/3600s * 75A = 0.375Ahr every cycle * 20 cycles per hour * 2hrs = 15Ahr consumed during test. The grp 29 batts are rated at 122Ahr, but at 75A draw its certainly more like 90Ahr each ==> 270Ahr for the bank ==> (270-15)/270= about 95% SOC after 2 hours.
SG measured with hydrometer after 2 hour test = 1.275 maybe just a smidge below == FULL CHARGE.
OCV at end of 2 hour test == 12.7V exactly.
So, batteries still *fully charged* after 2 hours of use... BUT WAIT...
I reconnect the Stanley BC25BS charger and it immediately pegs at 25A charge current @14V and holds there for 10mins or so, then gradually tapers off over the next 2 hours to 1.7A and then finally goes into Float mode at 13.6V.
So... 1.275 SG and 12.7V and the batteries still took 2 hours to charge with a 25A charger.
This is why I stopped using my hydrometer.
The actual maximum specific gravity will depend on the electrolyte level. As if offgasses in deepcycle usage with long times on a charger, the water is driven out, the electrolyte gets denser, and can read well into the green, 1.260+ when there is just enough electrolyte to lift the float but the battery is still not fully charged
Once filled to a mm or 2 below the little hanging arms, Even physically squirting the electrolyte through the plates within the cell and agitating it,, One will be lucky to see that 1.240 specific gravity and then one can spend several more hours at 14.4 to 14.8v, trying to get specific gravity back up towards 1.275ish.
Batteries intended for cold climates might have 1.300 specific gravity, hotter climate batteries might max out 0.040 below this.
Its really best to know what the max SG reading is when the specific batteries are new and fully charged, AND take note of the level of electrolyte in the cells, as if they are low, just above the plates, the density can read high, and when freshly watered it will take a significant amount of time for specific gravity to stop rising again as the water mixes in.
If SG is still well below expected after an extended absorption phase, then the EQ voltages as high as 16.2v could be initiated to recover more capacity.
16.2v eq charges will have the batteries fizzing. Lots of gas exits the batteries, with a sulfuric acid mist. The batteries can warm up rapidly.
This intentional overcharge is abusive, it should be performed not as natural periodic maintenance, but only when one can't get the specific gravity up where it should be, with extended absorption charges in the mid to high 14's. They are not a set it to 16.2v and come check on them in 5 hours type of thing. Hands on attention is required to prevent overtemp and to stop the charging once specific gravity no longer responds.
The closer the battery reaches to full true charge on ceach consecutive cycle , the easier it is to get specific gravity as high as it should be. Takes much less time.
WQhen a cycling battery goes time and again only reaching 98 to 99% charged, that last one percent can then take many many more hours at ~14.8v then 45 minutes to 4 hours at 16.2 before Specific gravity stops rising.
Sometimes just continuously trying to top off a lead acid battery simply does not work to restore capcity/performance. Try loading it with 15 to 20 amps per 100Ah of capacity until voltage falls to 12.05v or so, then immediately recharge with upto 30 amps per 100Ah of capacity, but 12 to 18 would be a safer sweet spot.
Maximizing lead acid battery life in deep cycle duty, can be taken to extremes, with time and effort and special equipment more costly, than simply replacing batteries more often. Short life of a lot of Lead, gets expensive though, so one needs to find their own acceptable balance.
The EQ charge, performed properly, and only when required, can greatly extend flooded lead acid battery longevity and performance, but it can also lead to abusive overcharging, which can be dangerous, or detrimental to the battery, or both.
Use Eye protection and plenty of ventilation, and keep the batteries from exceeding 110f. The center cells heat up faster than the ends, and don't forget to check the bottoms of the cells for excessive heating too. The IR temp gun moved around the battery case can help see a problem cell heating excessively.
The Hydrometer on such a cell, will likely read far different than the other 2, or 5 cells
The weirdo cell can often be the only one worth checking as the other 2 ,or 5 , can often all be behaving similarly.
If one nurses the last cycle out of some abused batteries, then taking care of new ones properly from deep cycle number one, seems like a cakewalk in comparison
Once filled to a mm or 2 below the little hanging arms, Even physically squirting the electrolyte through the plates within the cell and agitating it,, One will be lucky to see that 1.240 specific gravity and then one can spend several more hours at 14.4 to 14.8v, trying to get specific gravity back up towards 1.275ish.
Batteries intended for cold climates might have 1.300 specific gravity, hotter climate batteries might max out 0.040 below this.
Its really best to know what the max SG reading is when the specific batteries are new and fully charged, AND take note of the level of electrolyte in the cells, as if they are low, just above the plates, the density can read high, and when freshly watered it will take a significant amount of time for specific gravity to stop rising again as the water mixes in.
If SG is still well below expected after an extended absorption phase, then the EQ voltages as high as 16.2v could be initiated to recover more capacity.
16.2v eq charges will have the batteries fizzing. Lots of gas exits the batteries, with a sulfuric acid mist. The batteries can warm up rapidly.
This intentional overcharge is abusive, it should be performed not as natural periodic maintenance, but only when one can't get the specific gravity up where it should be, with extended absorption charges in the mid to high 14's. They are not a set it to 16.2v and come check on them in 5 hours type of thing. Hands on attention is required to prevent overtemp and to stop the charging once specific gravity no longer responds.
The closer the battery reaches to full true charge on ceach consecutive cycle , the easier it is to get specific gravity as high as it should be. Takes much less time.
WQhen a cycling battery goes time and again only reaching 98 to 99% charged, that last one percent can then take many many more hours at ~14.8v then 45 minutes to 4 hours at 16.2 before Specific gravity stops rising.
Sometimes just continuously trying to top off a lead acid battery simply does not work to restore capcity/performance. Try loading it with 15 to 20 amps per 100Ah of capacity until voltage falls to 12.05v or so, then immediately recharge with upto 30 amps per 100Ah of capacity, but 12 to 18 would be a safer sweet spot.
Maximizing lead acid battery life in deep cycle duty, can be taken to extremes, with time and effort and special equipment more costly, than simply replacing batteries more often. Short life of a lot of Lead, gets expensive though, so one needs to find their own acceptable balance.
The EQ charge, performed properly, and only when required, can greatly extend flooded lead acid battery longevity and performance, but it can also lead to abusive overcharging, which can be dangerous, or detrimental to the battery, or both.
Use Eye protection and plenty of ventilation, and keep the batteries from exceeding 110f. The center cells heat up faster than the ends, and don't forget to check the bottoms of the cells for excessive heating too. The IR temp gun moved around the battery case can help see a problem cell heating excessively.
The Hydrometer on such a cell, will likely read far different than the other 2, or 5 cells
The weirdo cell can often be the only one worth checking as the other 2 ,or 5 , can often all be behaving similarly.
If one nurses the last cycle out of some abused batteries, then taking care of new ones properly from deep cycle number one, seems like a cakewalk in comparison
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