What Is An Intelligent Battery Charger?
What is a smart charger?
a smart charger allows a user to charge and maintain their vehicle's battery using mains power. unlike traditional battery chargers, smart chargers are programmed to recondition, recharge and then maintain various battery types. suitable for a wide range of batteries, including stop-start vehicles, smart chargers can be connected and left for long periods of time, ideal for seasonal vehicles.
Regular charger and smart charger
- regular battery chargers
- regular battery chargers are only suitable for a limited range of battery types, typically lead acid and gel.
- smart chargers
- smart chargers on the other hand are capable of charging a much wider range of batteries, adapting to each type to deliver the most efficient charge cycle.
- maintenance mode
- reconditioning the battery, recharging it and the smart charger automatically switches to maintenance mode.
- maintenance mode allows the smart charger to be left permanently connected to the battery, unlike the traditional charger which must be removed following charging.
Battery charger functions
all chargers send electricity to your car's battery, but there are three main functions that they can perform. make sure that the charger you’re buying does what you need it to do.
- maintenance charging
- also referred to as 'trickle' charging, this sends a small amount of electricity to your battery to keep it healthy while it's being stored for long periods of time.
- conventional charging
- this sends power to your battery to charge it up from a low amount of power. this can take between 6-24 hours, but it typically takes about 10 hours to charge a battery to full.
- engine start function
- this is the same as jump starting your car. it takes a lot more power, so is normally seen on more heavy-duty chargers.
Battery types and voltage
- smart chargers differ in their voltage and amp output.
- although almost all cars use a 12v battery, the size of each battery will vary according to the size of the engine fitted.
- as smart chargers with higher amp outputs charge batteries faster, we recommend using these on larger batteries.
- certain models of smart chargers also feature additional voltages such as 6v for mowers and small motorcycles and 24v for commercial vehicles such as hgvs.
Battery type detector
the main types of rechargeable batteries are lithium, nicad, nickel and lead acid. their charging needs vary.
attempting to charge a lead acid battery, for example, at the same rate as a lithium battery might well result in damage to the battery in the best scenario and a fire or explosion in the worst.
on the other hand charging a lithium battery at the same rate as a lead acid battery makes the process far slower than it needs to be, wasting time and the opportunity to use the device.
- some smart chargers are now able to identify the battery type and voltage when they are connected through two steps.
- the first step is to read the voltage of the battery.
- the voltage of a battery reduces gradually as it is discharged so it is an indicator of how much charge the battery contains.
- the next step is to apply a small current that would be safe for all battery types and monitor how quickly the voltage rises.
- a slow rise indicates a lead acid battery that will require a gradual rate of recharge.
- a quick rise will indicate other battery types, such as lithium, which can be recharged more rapidly.
- the rate of voltage changes as the battery recharges then give more indications of whether the battery is lithium, nicad or nickel allowing the charger to then alter the charge current further.
Reverse polarity check
for a rechargeable battery to charge an electrical current needs to be passed through it via the positive and negative terminals.
a battery charger will have two connections, one for the positive terminal and one for the negative terminal of the battery.
however some batteries and chargers are open to human error, it is possible to connect the charger to the battery incorrectly.
- if the battery has very little charge left in it then the electrical current from the charger will start to push through the battery in a way it is not designed for.
- the resulting heat from this friction can result in an explosion or fire.
- if the battery is still partly charged when the charge is connected incorrectly the current will be pushed back and the charger will sustain damage.
- this may simply be a blown fuse but potentially the damage to the charger might be enough to destroy it completely.
- in order to avoid any of the above happening a smart charger with a reverse polarity check has the ability to sense if it has been incorrectly connected to a battery and, if so, break the connection via an internal circuit.
- this protects both the charger and battery from potential damage and avoids any risk of fire or explosion.
Battery health check
once a charger is correctly connected and, if the charger has the feature, the battery type is identified the next question is – can this battery be recharged?
reasons why a battery can be charged include that it is already fully charged, it is faulty or it has reached the end of its life.
a traditional battery charger will simply pass a small charge through a battery in order to recharge it even if the battery has reached the end of its life span and can no longer take a charge. a smart charger will look to see if the battery is chargeable using state of charge as a measurement
- as mentioned earlier the state of charge of a battery can be determined by measuring the voltage of the battery.
- however the one thing we know for sure is that as a battery recharges it’s voltage will increase and this increase will start as soon as a charger starts to pass a current through the battery.
- some smart chargers will look to see if it senses this increase and, if there is none, can signal to the user that the battery is no longer rechargeable.
- despite this feature it should be noted that smart chargers can get this wrong.
- if a battery has recently been heavily discharged it will probably be quite hot internally and in this situation it will not be able to take a charge before cooling.
Short circuit sensor
most batteries are actually made up of smaller batteries, known as ‘cells’.
a 6 volt lead acid battery contains three 2 volt cells connected together in such a way to provide 6 volts via the positive and negative terminals.
- if any of these individual cells have failed it may still be possible to apply a charge to the battery but there won’t be much point.
- a 6 volt battery with a failed 2 volt cell will give, even when fully charged, 4 volts.
- that’s not enough to power a device which needs 6 volts.
- a smart charger will be able to check this by taking a voltage reading.
- a fully discharged 12 volt lead acid battery will have around 11 volts.
- anything below that signals a failed cell.
Battery recovery operations
just because a battery cannot take a charge or it appears that one or more cells are faulty doesn’t mean a battery has reached the end of its life. it can be possible to recover the battery to a state where it can take a charge.
the most common situation is with lead acid batteries that have not been used for a long period. this type of battery often suffers from ‘sulfation’. this is where crystals build up on internal elements of the battery which stop the free movement of electrons needed for recharging.
- sulfation can sometimes be repaired by pulsing an electric current through the battery.
- the pulses gradually break down the crystals so the electrons can move again.
- a smart charger that senses a battery unable to charge or with what appears to be a faulty cell might try and operation like this to see if it resolves the issue.
Charging speed control
simple battery chargers pass a constant current through a battery but its a lost opportunity as batteries with a high state of discharge are able to take a much higher current to begin with. this can dramatically reduce the time it takes to recharge a battery.
- some smart chargers will sense the state of charge of a battery and apply a varying level of current.
- higher current when the battery is highly discharged and easing off as full charge approaches.
- when a compatible smart charger and smart battery are connected they can optimize this even further.
- a smart battery can report it’s internal temperature to the charger which will allow the charger to know what maximum current can be applied at any moment in time to give the highest level of charge without damaging the battery or risking explosion or fire.
Full charge cut off
only the most basic of battery chargers do this. even fairly simple ones know to switch off if the battery reaches full charge. but how do they know?
as we saw in the section above ‘battery health check’, as a battery charges its voltage increases. a fully discharged 12 volt battery may have a voltage of 11.5 volts. as it charges this increases gradually to around 12.6 volts.
- however the exact voltage at full charge will differ slightly, even for 12 volt batteries from the same manufacturer.
- so a simple cut off at x volts is not possible.
- a smart charger will simply stop once it senses the voltage is no longer increasing and so avoid over charging.
Maintenance mode
most battery chargers work through 4 stages – test, charge, absorption (abs) and maintain – as demonstrated in the graph below.
- once a battery is fully charged a traditional charger will continue to pass a very small current through the battery known as a ‘trickle charge’ to keep it fully charged.
- some smart chargers will switch off the current and then perform regular checks to see if the battery needs a further recharge which is better for the battery compared to the ‘trickle charge’.
- this feature is often used when a battery is going to be stored for a long period of time, such as batteries in vehicles that are not going to be used for several weeks.
Continuous connection mode
there are times when we need to, or it is practical to, keep a charger connected to a battery over a long period of time.
two common examples are batteries for garden machinery during the winter and batteries for mobile internet routers which are plugged in most of the time.
- but this is not always a case of keeping a battery ‘fully charged’.
- lead acid batteries will have the longest lifespan when they are kept at around 70% charge.
- lithium batteries, on the other hand, are best kept at 40 to 70% charged.
- a smart charger can take this into account.
- if it senses it has been connected to a battery for a long time it can top up, or even discharge, a battery as needed to achieve an optimized long term state of charge for a better battery lifespan.
- this feature is also often referred to as ‘battery charger protection mode‘.
BMS communication
many smart batteries contain a battery management system (bms). these vary in complexity but can include:
- the date the battery was manufactured
- how often the battery has been discharged and recharged (cycled)
- the expected lifespan of the battery
- the current internal temperature of the battery cells
- the exact state of charge of each cell (where the battery is made of more than one cell)
a compatible smart charger will be able to read all of this data in real time to provide optimized charging. a battery, for example, that is cool inside can be charged faster than one that is hot because of recent use.
Safety monitoring
- in its basic form a smart charger may be able to monitor issues with the batteries such as spikes in current which could indicate a faulty cell.
- if the charger is communicating with the battery’s management system it can also be aware of other changes such as a high internal temperature of the cells that, if not dealt with, could lead to fire or an explosion.
- some smart chargers can then apply measures such as fan cooling or disconnecting the battery from external devices until the situation has normalized.
How to use a smart charger
- with the engine not running, connect the battery clamps to the corresponding battery posts.
- red to the positive post and black to the negative post.
- connect the smart charger to the mains power
- select the corresponding voltage and mode
- leave the smart charger attached
- once charged the smart charger will automatically switch to maintenance mode
- disconnect the charger from the mains and remove once the vehicle is needed
