Flat Batteries & Car Battery Chargers Explained

Disclosure: I received a free review sample from Ring Automotive for the purpose of this review. I purchased my own charger from CTEK. I received no payment from either company and was not required to write positive reviews. Links marked with (eBay⇒) or (Amazon⇒) are affiliate links. This means I get paid a small commission if you buy something after clicking on the links. This money helps to pay for the running of the website.

A flat car battery makes a bad start to the day, especially if it is early on a cold, winter morning – probably the most likely time to find that your car’s battery has mysteriously gone flat since you last used the car. It’s a depressingly common problem, too – the AA attended more than 500,000 call outs for battery problems in 2008 alone.

Of course, car batteries do not go flat for no reason – if your car’s battery goes flat after being left for just one or two nights, then there are three likely reasons:

  1. Too many short journeys from cold with lights, windscreen wipers and heated windscreen on have prevented the battery recharging fully after being used to start your engine. This is a common problem for urban commuters in winter.
  2. Your battery is getting old and is starting to fail – don’t expect more than five years of reliable service from a typical car battery.
  3. Modern cars have lots of electronics, some of which will drain the battery even when the car’s not in use. Typical culprits include alarms and stereos. To minimise the risk of accessories draining your car’s battery, make sure you switch off the radio, windscreen wipers, heater fan, lights, heated windscreens and all other electrical accessories before you switch the engine off. Obviously you won’t want to disable your alarm – but a correctly functioning alarm shouldn’t drain the battery too fast unless something keeps setting it off.

If your battery is getting old and failing, the best plan is to replace it before it stops working completely. Most tyre/exhaust centres will fit batteries (as will Halfords) in just a few minutes, and will test your current battery first to make sure it does actually need replacing. Unfortunately, a battery test is not something you can easily do for yourself.

If your battery is healthy but it just isn’t getting charged enough, then the solution might be to hookup a battery charger overnight, or perhaps just at the weekends.

Introducing Multi-Stage Battery Chargers

The best types of battery chargers are multi-stage chargers. These adapt their charging routine to match the state of your battery – when it’s very flat, it gets a big boost, and when it is nearly charged, the charger will reduce it’s charge to just a trickle. This kind of treatment helps to keep your battery in good shape, preventing overcharging and giving a new lease of life to really flat batteries (assuming they are not faulty).

Let’s look at a couple of mid-range car battery chargers that have three important functions:

  1. Desulphation – a technical word that describes the process needed to start charging a really flat battery.
  2. Bulk charge – regular charging, to you and me. The type of charging that would be needed to charge your car’s battery if it had gone flat over a long winter weekend.
  3. Float or trickle charging – once a battery is charged, continued bulk charging can damage it. Modern multi-stage chargers will recognise this and automatically switch to trickle or float charging mode, where the battery is monitored and just given a little topup occasionally to prevent it discharging. This type of charger can be left connected permanently if necessary without doing any damage to the battery.

Ring Automotive SmartCharge+ 8

Ring Automotive SmartCharge+ 8 battery charger in use
The SmartCharge+ 8 has a fold out hook, allowing you to hang it wherever necessary

Ring is a well-known maker of car accessories, especially light bulbs. They also make a number of other products, including battery chargers. The SmartCharge+ range is a range of automatic, multi-stage battery chargers, most of which have the ability to recondition flat batteries and can be left connected permanently to keep batteries trickle charged.

The model I tested was the SmartCharge+ 8. The 8 refers to its maximum charging current – 8A. Battery chargers are often specified by their maximum charging current, as this is a crude measure of how fast they can charge a really flat battery.

The Ring is attractively designed and simple to use. It even has an LED light on the end that you can use to see what you are doing if you need to connect up the charger in the dark. It is fully automatic – you just connect it to your battery and switch it on (in that order). The SmartCharge+8 provides a lot of information on its LED screen – you can see charging voltage, charging current and percentage charged (this is probably the most useful, unless you are interested in the technical details).

The manual that comes with the Ring is well written by a native English speaker and is easy to understand. It explains clearly how the charger works and how to use it.

In use, the charger seemed to work well and topped up my van’s battery without problems, despite the sub-freezing temperatures.

Price: At the time of writing, retail price for the SmartCharge+ 8 seems to be around £55-£65.

CTEK Multi-XS 3600 Battery Charger

CTEK is a Swedish company that specialises in automotive and marine battery chargers – they make nothing else. Like the Ring SmartCharge+ 8, the Multi-XS 3600 is a fully automatic, multi-stage charger than can revive flat batteries, charge healthy ones and be left permanently connected as a maintenance charger.

CTEK Multi-XS3600 multi stage battery charger

The maximum charging current of the 3600 is 3.6A – a lot lower than the SmartCharge+ 8 but enough for most purposes. One feature of CTEK chargers is that they are often smaller than competing devices – this holds true with the 3600, which is about half the width and length of the SmartCharge+ 8.

The CTEK does not provide as much information as the SmartCharge+ 8; it has three lights to indicate charging status (fault, charging and maintenance mode) and three settings that you can choose, depending on your charging requirements:

  • 0.8A mode (used for very small batteries)
  • Car mode – normal charging mode for most batteries
  • Cold charging mode – used instead of car mode when the temperature is below 5°C (winter temperatures in Sweden are pretty low!)

The manual is well written and explains clearly how to use the charger – but in reality, it’s really simple. Connect the battery, then plugin the charger and press the mode switch until it goes to car mode (usually). That’s it.

Price: At the time of writing, the CTEK 3600 can be purchased online for around £45-£55.

Charging Time

I have not mentioned charging time so far in this review. The reason for this is that it can vary hugely, depending on the state of your battery and the capacity of your battery – a small, petrol-engined hatchback will have a much smaller battery than a large, diesel-engined 4×4 (diesel engines require more powerful starter batteries).

However, as a guide, a flat battery will take anything from a few hours up to a day to charge fully. These aren’t instant fixes for a flat battery – for that, you need a power pack, such as those used by mechanics and breakdown services. These will enable you to start your car more or less instantly, but won’t charge your battery – you will have to give the car a decent drive to do that. If your commute to work is a 20 minute urban crawl, then a power pack is not really the solution because, in winter, you will probably still have a flattish battery when you get to work.

Final Thoughts

Both the CTEK and Ring Automotive chargers are powerful enough for the vast majority of car batteries and would also make good chargers for batteries which need to be kept charged when not in use for extended periods, such as classic car batteries in winter or caravan and motorhome leisure batteries.

Although they are a little more expensive than more basic chargers, their sophistication makes them worth it, in my opinion – although you could certainly manage with a cheap charger if all you want to do is boost your car’s battery for a few hours occassionally.

Battery chargers are designed to help prevent flat batteries as well as cure them. By keeping your car’s battery topped up when it is not in use, you can be sure it will start when you need it. If this is not practical for you – if you have on-street parking only, for instance – then a power pack might be better, as these do not need to be plugged in when in use. Just remember that your car’s battery will still need to be charged by driving once you’ve got the engine started.

Buy a car battery charger on Amazon (Amazon⇒)

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