How do you Charge an EV

how do you charge an ev

Different kinds of EVs come with different kinds of charging methods to charge an EV.

Our concern is primarily with affordable electric cars, so here we will not concern ourselves with the more expensive mainstream vehicles.

The “mainstream” vehicles usually require a heavy-duty charger for one reason. Their batteries are much higher power than the batteries fitted to our affordable electric cars and to charge an EV of that kind therefore requires a much heavier-duty system than that fitted to the normal house. It’s quite possible to fit that in the home, but of course, it’s an extra expense.

Our affordable electric cars don’t need that. Ours are of more modest means and a normal extension cable from the house to the car is adequate to charge. an EV of the type in which we are interested. Most of our cars are charged overnight and take about 6 – 8 hours for a full charge. Mine are never allowed to get that low, and my charges usually take no more than an hour or two.

Be sure NEVER to plug a street charger into one of our cars. Something disastrous may happen.

charging ev batteries

Most of the cars we are interested in here do not have monster batteries. The reason is that big batteries are very expensive and that takes our vehicles out of the realm of “affordable” in the context we are interested in. The less expensive batteries are generally those which look like ordinary car starting batteries, though not with the same internals.

Cost of electric car batteries

We do have to mention cars from the big international manufacturers, however, to distinguish between the mainstream batteries and ours. Big batteries are generally all of the lithium-ion type and of several kilowatts in the 40s, 50s and up. These batteries cost between $4,000 and $20,000 for which money we can buy several of the more affordable ones. The batteries for affordable electric cars fall into the previously mentioned category of “standard” looking batteries. The replacement cost is more in the line of $500 to $1500 and Wattages of usually less than 10 kilowatts.

ev batteries of the gel variety

These smaller battery packs have different requirements for charging. The big lithium-ion beasts tend to put out voltages in the 400 to 800 volt range, whereas ours, are generally 60 volts to 72 volts with a few exceptions.

why do electric cars use a high voltage?

The answer to this question comes back to Wattage. The energy consumed by the electric motor is measured in Wattage. Let’s look at some examples.

Battery TypeVoltageCurrentWattage
Large Lithium-Ion Battery500 Volts100 Amps50 KiloWatts
Lead / Acid variants72 Volts100 Amps7.2 KiloWatts
Lead / Acid variants60 Volts100 Amps6 KiloWatts
Lead / Acid variants12 Volts100 Amps1.2 Kilowatts
You can see from the chart that for a high-power vehicle, a high voltage is required for the same 100 Amps current to the motor.
Watts = Volts x Amps

Our batteries are generally of the Lead / Acid variants, though some affordable electric cars use Lithium-Ion batteries of lower voltage and therefore lower cost. Here we will concentrate on charging the lead/acid variants with a mention later of the smaller lithium-ion batteries as their charging requirements are different.

Most of the affordable electric cars use a low voltage motor – low compared to mainstream cars – in the region of 60 to 72 volts. The reason is simple.

To manufacture an affordable electric car, we need to keep the most expensive component at a low cost. That’s the batteries. What can we get in batteries at a reasonable cost? Only Lead/Acid variants.

Lead / Acid Battery TypeVoltageAmpere Hour Battery Life YearsCharge cyclesWeight per BatteryCost
Flooded12 Volt100 Ah> 2 years> 60023 kg$150
Gel12 Volt100Ah> 2- 3 years> 60036 kg$380
AGM12 Volt100 Ah> 4-6 years> 60026 kg$249
Li-FePO412 Volt100 Ah> 8 – 10 years> 5,00012.8 kg$589

It can be seen from the chart above that the most economical battery has to be the Li-FE PO4 as the number of charging cycles 6 times that of the others. The problem is that if the car is to be run on a budget, to fit 5 of the Li-FE PO4 batteries comes out at $3,000. Over ten years that’s not so bad but the outlay is expensive. AGM batteries are will give at least 600 charges at $300 each or an outlay of $1500.

The cars are usually fitted with gel batteries. the all up weight of the batteries is 180kg for Gel batteries whilst giving about the same results, are

Comparison of weight of batteries fitted to an affordable electric carCostweightWeight Saving
Original Gel batteries 5 units = 60 voltsAs supplied180 kg 
Original Gel batteries 6 units = 72 voltsAs supplied216 kg 
AGM replacement batteries 5 units =60 volts 130 kg5 units = 50 kg
AGM replacement batteries 6 units =72 volts 156 kg6 units = 60 kg
Li-FE PO4 replacement batteries 5 units = 60 volts 64 kg5 units = 116 kg
Li-FE PO4 replacement batteries 6 units = 72 volts 76.8 kg6 units = 139.2 kg

charging electric car batteries

charging old batteries

Gel batteries require a charge of 2.3 to 2.35 per cell. As the batteries contain 6 cells

Charge settings for various batteriesvolts per cell12volt battery
Gel2.3 to 2.35 volts13.8 – 14.1
AGM charging is rated as current. 0.1 to 0.15A at 20 hour rate. 100Ah battery = 10 to 15 Amps charge
Li-FE PO414.2 to 14.4 volts 

how do you set an electric car charger?

Automatic chargers differ between makes of car so it’s not possible to go into every combination. A general description will need to be given here.

universal intelligent battery charger

This is the charger I recommend from my own practical tests and results. It will charge all lead/acid batteries, gel batteries and AGM batteries. Gel and AGM are the most critical and demanding for correct charging procedures as they require a heavier charge initially, which reduces as the charge completes. The battery voltage from the charger is held constant during the charge which is not the case with lead/acid batteries. I use this charger and periodically, charge my batteries individually which helps to maintain balance between them.

There is no need to take the batteries from the vehicle or even to disconnect the power cables from each battery. For safety, I switch off the vehicle master switch then I connect the positive and negative charger leads directly to the battery I wish to charge, without disturbing any connections at all. The charger is only in parallel with the one battery you are charging and everything works as normal. When the battery has finished charging, I unplug the main electricity supply and move the charger leads directly onto the next battery in line and plug in the main power again. I do this to each battery in turn with the vehicle’s power switch off. When all is finished, remove the charger, turn on the vehicle’s main power switch and you are ready to go.

The point to remember here is that this is best done when you don’t need the car for a while, as with six batteries, this can take several days if the state of each individual battery requires it. Just remember that although this may be a drag, it can potentially save you lots of cash replacing batteries before they would otherwise need to be replaced.

intelligent battery charger in use

The charger has lead/acid setting, gel/agm setting and battery repair setting all controlled by a computer processor chip. The screen shows temperature, input voltage, battery voltage and charging current as it cycles through the settings automatically reducing the charging current as the battery nears full.

Interestingly, with my own setup, I found that two of my six batteries were charging at around one amp. On connecting the charger to the next battery in series, it immediately began charging at 5.26 amps which shows that the batteries were certainly not balanced. The problem is that unless all batteries are balanced, the charging voltage from the main 72-volt series charger will reduce and eventually stop charging before the lower-charge batteries get anywhere near their full charge. This will prevent the 72-volt system from ever getting fully charged, thereby reducing the EV range and eventually causing possible damage to the batteries. This is the same no matter what type of battery is fitted to the vehicle.

After the replacement batteries have been balanced (equalised), the batteries should be installed in the car. After locating the adjustments in the charger, we need to switch the charger on. No harm will be caused to the batteries whilst the setup procedure goes ahead.

Setting the Built in charger for AGM batteries

The charger will already be set for the Gel batteries, so let’s begin with AGM adjustments. Connect a voltmeter first across the total battery pack to check that the voltage present at the time is in the region of that required by the batteries. If it’s a 60-volt pack, the voltage will probably be around 72 volts fully charged. If it’s a 72-volt pack it may be around 83 volts or so.

The following instructions are for a battery pack which is in need of charging. Fully charged batteries will not take current from the charger. If you were to set the charger for a high current, the batteries could be overcharged and ruined.

First, switch off the charger. Now turn off the car’s master switch. Disconnect one end of the battery pack terminals. It makes no difference which one is disconnected as you are measuring the flow through the complete set of batteries. Connect an ammeter capable of reading around 20 amps, one end to the terminal from where you disconnected the cable, and the other end to the cable itself so that the circuit is completed by running the power through the meter as in the diagram. Switch on the master switch and then the charger. Set the internal control to read a current of 10 to 15 amps. Switch off the charger, and the master switch. Remove the ammeter and return the cable to the terminal as originally connected. The AGM charge rate is set.

A question which is often asked is if you have an affordable electric car with 5 or 6 gel batteries as usually supplied with these vehicles, can you simply use a different kind of battery without problem? The answer is yes providing the correct charging procedures are setup and adhered to.

A Gel charger puts out a voltage of about 82 -84 volts. The charging voltage of a lead-acid battery is usually 13.7~13.8V, 72V batteries have 6 of these batteries in series, and the charging voltage is 82.2~83.8V. A gel charger puts out a voltage of 14.1 to 14.4 volts for a single battery. This is also quite a satisfactory voltage for all lead/acid varieties. The problem is the reverse situation. If a charger for a normal lead/acid battery is used for a gel battery, its output may well exceed that needed by a gel battery and damage can occur.

Now we will turn to setting the voltage for a LiFE-PO4 battery pack.

For these batteries, it is the voltage that we set, rather than the current. Connect the voltmeter across the complete battery pack. Turn on the charger and note the voltage. For a 60-volt pack, it should be as in the chart – about 72 volts or so. Now set it to read 72 volts (not critical) but as near as possible. For a 72-volt pack set it to read 86.4 volts as near as possible. That’s all there is to it.

 

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