Modern batteries and modern smart chargers: From basic charging to reconditioning, stratification and sulphation
During the Covid pandemic car battery chargers became far more important. And they continue to be for many people who aren’t using their car anywhere near as much as they used to. However, with the proliferation of different battery technologies, start/stop and hybrid battery systems that we now have, do you know the correct way to charge your car to maximise the life of the battery and prevent damage?
I have posted a number of questions to CTEK customer support over the last couple of years in regards to using my the MXS 5.0* on different battery types. Partly, this is because info on the web is lacking, or sometimes incorrect (many car forums carry inaccurate info), but the user guide is also light on info. So I compiled this guide from their responses (and some extra advice from other sources) as a personal reference and to help others. Whilst it is written primarily for the CTEK MXS range of car battery chargers, much of the information will still be relevant for most other types of charger.
*Most of the modern smart chargers, including the Noco range, are broadly similar in functionality and use)
In this article:
- In-car charging with the CTEK MXS 5.0
- Flooded and Enhanced Flooded Batteries
- RECOND programme mode
- Desulphation (charging stage one)
- Stratification (using the RECOND programme)
- AGM batteries and the AGM Mode
- Calcium batteries
In car charging
So – from what CTEK support tell me – you can connect your CTEK MXS charger to the battery while it is installed in the car. Even the RECOND programme mode, where the max voltage peak is 15.7v (+0.3v higher than non-RECOND programmes), SHOULD be perfectly safe for MOST cars. Typically, anything under 16 volts shouldn’t cause any problems for a modern car. Having said all that, there are bound to be exceptions. It is definitely worth taking the time to check this with your car manual or manufacturer – as getting it wrong could be costly). A short safety guide is also available here.
The CTEK MXS 5.0 charger is robust and suits a number of different use-cases; charging large and small batteries, and many different types. They are well rated and CTEK offer lots of different models.
But what about other brands of car charger?
Read: Guide to charging with a Noco Genius5
Flooded (Wet) and Enhanced Flooded Batteries (EFB)
Typically for Flooded and Enhanced Flooded Batteries you would just use the mode button to select the car icon and charge with this mode. Standard flooded or “wet” batteries, which are more prone to stratification and sulphation, may require use of the RECOND programme periodically.
EFB batteries contain technologies and designs to destratify the battery acid (electrolyte), as well as being able to be cycled more deeply without detrimental health impacts like sulphation occurring (Read: What is an EFB battery?). This means you are less likely to need to use the RECOND mode, or see the charger attempt desulphation – read on about that below…
RECOND Programme mode
First off, only use RECOND mode with a standard Lead Acid Battery or Enhanced Flooded Battery (EFB) (this includes calcium EFB batteries). RECOND will not help an Advanced Glass Matt (AGM) battery. It could even harm a Gel battery. Find out more about what RECOND mode does in the Stratification section below. RECOND + AGM programme can be safely used on Ca-Ca (Calcium or Silver Calcium) type batteries, see more below.
Desulphation (Charging stage one)
Desulphation happens automatically, if required – not just in RECOND mode. Every CTEK charger mode starts with a desulphation step at the beginning. If the charger diagnoses a sulphated battery, it will attempt desulphation. If not, it will move on to step two.
Sulphation is where sulphuric acid crystals build up inside the battery on the electrodes. This typically happens when a battery spends periods of time in a partially charged or uncharged state. During desulphation the charger will pulse voltage peaks to help break down and remove these crystals.
CTEK chargers will spend as long as is required, or until a prefixed period of time has lapsed, on desulphation. To give you an idea, this is usually a number of hours, not minutes. If the charger is unable to complete this step within the time period it will show an error and the charger will not move on to the next step. You may need to attempt this process several times if sulphation is extreme. I have had success with small 7Ah AGM UPS batteries in the past, but never with a dead car battery. If after several attempts you still receive an error then you may need to replace the battery.
Stratification
What the RECOND programme includes is a process called destratification, which creates a controlled gassing that remixes the acid and equalises the acid balance. This process helps to reclaim battery capacity and restore battery efficiency. The success of the reconditioning process depends on how severe the problem is.
What Stratification physically is is a situation where the electrolyte, which is denser, sinks towards the bottom of the battery cells and thereby ‘starves’ the top of each cell, thereby reducing the voltage potential of the battery and its cold cranking power.
Stratification can happen if the alternator charging voltage is too low or the charging time is insufficient (due to short drives, or heavy use of accessories that reduce charging current), or where a battery is deeply discharged and unused for a period. Different batteries suffer more or less from stratification, depending of the battery type and design.
Because AGM or Gel batteries do not suffer with stratification, RECOND mode won’t help revive these types of battery. It may even damage the health of Gel batteries – more on this here in my Guide to car battery technologies.
AGM battery charging with the AGM mode
The AGM programme uses a slightly higher voltage (+0.3v) at it’s peak. That’s all. It will still attempt a desulphation stage at the start of the programme if deemed necessary by the charger. The higher voltage is just better suited to these types of batteries. (Read: What is a AGM battery?)
Calcium battery charging
The reason for the CTEK charger AGM+RECOND mode:
So if destratification doesn’t benefit an AGM battery, why does a CTEK charger provide an AGM + RECOND mode? The answer is that Calcium batteries can benefit from this programme. Calcium (Ca-Ca) batteries (More info here) can suffer from stratification, so using RECOND to create a gentle gassing in the battery can help restore power (See: Destratification, above). As calcium batteries typically charge at higher voltages, they are better suited to the AGM programme mode and its higher voltage (+0.3v). Hence it being possible to use the AGM and RECOND programmes together.
Check out the CTEK charger on amazon >
Thanks to CTEK customer support for answering my many questions!
Also read:
- Find out more about different car battery technologies in my guide, here >
- Which to buy: CTEK MXS 5.0 OR Noco Genius5 battery charger?
