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There have been a lot of threads about flat 12v aux batteries and a bit of mythical knowledge coming from the dealers and most definitely from who ever wrote the 12v maintenance software .... clueless comes to mind .....
A bit of preamble from another thread here Replacement 12v auxiliary battery for MGS5 .... so if you have already suffered through that, you can skip through to the next bit ... or look for something that won't bore you to tears or send you to sleep.
A lead acid battery needs to remain at charging voltage, above 13.6v min, to actually recharge. 13 .6v will maintain the charge at 100% if it is already at 100%, it will bring a battery up to about 50% SOC if it stays at that voltage for 24 hrs or more, but that is no enough voltage to over come the inherent internal resistance of any type of lead acid battery.
Now, if the battery was not saturation charged when built, it will already begin sulphating ..... within 12 hrs actually .....
If the terminal voltage is held at 14v for 12 hrs or more, you can get closer to fully charged, as long as the plates are not sulphated. Once the sulphation starts on lead acid plates, no chemical reaction can occur in that part of the active plate, so capacity is lost.
The only way to remove sulphation is with a pulse charge, higher than 16.5v but very short bursts. This forms very small bubbles within the lead plate that gradually push the sulphur out of the lead ..... As long as it hasn't been there for too long, it will return to the electrolyte and increase the specific gravity of the sulphuric acid ..... if it has been there long enough to bind with the surface of the lead plate, it will flake off and drop to the bottom of the cell electrolyte reservoir ... harmless until it build up enough to reach the bottom of the plates, then it shorts the plates out and you get that sudden dead cell ......
Naturally, this reconditioning pulse charging can't happen when the terminals are connected to any appliance, this includes the vehicle's 12v system, so the battery at minimum must have the negative terminal disconnected. ... I'll explain in another post why the negative terminal should be the first off and the last connected at the end ... If I remember
There are a few quality chargers that can have a reconditioning or de-sulphation cycle engaged, it takes quite a while, the longer it has been sulphated, the longer it will take to de-sulphate .......
C-Tek is a well known brand that has a de-sulphating cycle, you can buy or even build your own, this came up on Google search How to Restore Sulfated Batteries | Battery Chargers but I am not in anyway endorsing them, I've never used any of their products, but there are heaps out there .....
T1 Terry
A bit of preamble from another thread here Replacement 12v auxiliary battery for MGS5 .... so if you have already suffered through that, you can skip through to the next bit ... or look for something that won't bore you to tears or send you to sleep.
A lead acid battery needs to remain at charging voltage, above 13.6v min, to actually recharge. 13 .6v will maintain the charge at 100% if it is already at 100%, it will bring a battery up to about 50% SOC if it stays at that voltage for 24 hrs or more, but that is no enough voltage to over come the inherent internal resistance of any type of lead acid battery.
Now, if the battery was not saturation charged when built, it will already begin sulphating ..... within 12 hrs actually .....
If the terminal voltage is held at 14v for 12 hrs or more, you can get closer to fully charged, as long as the plates are not sulphated. Once the sulphation starts on lead acid plates, no chemical reaction can occur in that part of the active plate, so capacity is lost.
The only way to remove sulphation is with a pulse charge, higher than 16.5v but very short bursts. This forms very small bubbles within the lead plate that gradually push the sulphur out of the lead ..... As long as it hasn't been there for too long, it will return to the electrolyte and increase the specific gravity of the sulphuric acid ..... if it has been there long enough to bind with the surface of the lead plate, it will flake off and drop to the bottom of the cell electrolyte reservoir ... harmless until it build up enough to reach the bottom of the plates, then it shorts the plates out and you get that sudden dead cell ......
Naturally, this reconditioning pulse charging can't happen when the terminals are connected to any appliance, this includes the vehicle's 12v system, so the battery at minimum must have the negative terminal disconnected. ... I'll explain in another post why the negative terminal should be the first off and the last connected at the end ... If I remember
There are a few quality chargers that can have a reconditioning or de-sulphation cycle engaged, it takes quite a while, the longer it has been sulphated, the longer it will take to de-sulphate .......
C-Tek is a well known brand that has a de-sulphating cycle, you can buy or even build your own, this came up on Google search How to Restore Sulfated Batteries | Battery Chargers but I am not in anyway endorsing them, I've never used any of their products, but there are heaps out there .....
T1 Terry
