Important Battery Maintenance Information
We are using fundamental terminology in this information peace. The purpose hereof is to understand batteries and not be scientifically correct in all the wording. After reading this, you should understand batteries a lot better,
and you will be able to decide what to use.
The standard setup for Electrical vehicles is a battery pack of anything between 12v to 96v, in some cases, even higher. We are going to use a 60v system in all the explanations.
Lead Acid batteries
There are many types of lead-acid batteries we will be focusing on the standard car battery and deep cycle batteries for solar and Electric Vehicles.
Lead-acid batteries are very commonly available in 12v prefabricated units, and we will focus on them. 12v Batteries are constructed using six independent 2v cells. A battery cell is empty at 1.75 volts and full at
2.15 volt, and each cell operates independently. Some manufacturers have a minor variation on this, but the principles stay the same. The individual cells are connected in series to form the 12v battery. Below this paragraph,
there are some illustrations on the construction of a Lead-acid battery.
As illustrated, a 12-volt battery is more correctly six 2 volt battery cells connected in series.
Series connection - is when you connect the batteries by connecting the positive panel of one battery to the negative panel of the following battery. When you connect batteries in series, the volt increase, but the
amps stay the same. For example, if you connect five 12v 20A batteries in series you will have a 60v 20A battery.
Parallel connection – is when you connect the positive terminal of one battery to the positive terminal of the following battery and the negative terminal to the negative. When batteries are connected in parallel,
the volt stays the same and the Amps increase. If five batteries, 12v 20A, are connected in parallel, you will have a 12v 100A battery.
When you top up a battery, each cell has to be toped up individually because each sells functions on its own. The same applies to batteries in parallel or series; each cell is an individual unit. Here the term you
are as strong as your weakest link (cell) applies.
A 12v battery is not charged when you take the tester, and it shows 12v when you measure the battery. That only means the current volt on the battery is 12v; there can be 1Ap or 1000A in the battery. To determine how
much energy there is in a battery, you need more sophisticated equipment. In the chart below, you will see this manufacturers battery's voltage at 100% is 12.7v, and at 0%, it's 10,5v. When you test a battery, and it shows
under 11.8v, you are damaging the battery.
| State of Charge | 12 Volt Battery | Volts per Cell |
|---|---|---|
| 100% | 12.7 | 2.12 |
| 90% | 12.5 | 2.08 |
| 80% | 12.42 | 2.07 |
| 70% | 12.32 | 2.05 |
| 60% | 12.2 | 2.03 |
| 50% | 12.05 | 2.01 |
| 40% | 11.9 | 1.95 |
| 30% | 11.75 | 1.96 |
| 20% | 11.58 | 1.92 |
| 10% | 11.32 | 1.89 |
| 0% | 10.5 | 1.75 |
To understand how battery life works, you must keep this in mind. with every battery, you get e a manufacturer's specification sheet that indicates the battery's life expectancy.
In this table, you can see this manufacturers battery should last 1200 cycles at 30% discharge. Before you recharge it again at 50% discharge, you will get only 400 cycles, and a full discharge,
to 10,5v, you will have less than 200 Cycles.
That means the more often you charge the battery, the longer it lasts. And if you prevent it from over-discharging, it will last longer
You must understand what they mean when they say Volt, Amps, and Watt to understand batteries.
The explanation hereunder is not precisely correct, but you will receive a clearer understanding of what is said.
Volt is the battery type (fuel) you use for your electric car 40v, 60v, 144v, etc. In a fuel car, the kind of fuel type will be diesel or petrol or unleaded etc.
Amps show the electric capacity of your battery, similar to litres showing the capacity of your fuel tank.
Watt is how much energy you have or need for one hour. A 500w motor means you will need 500w of electricity to run the motor for 1 hour. And to calculate how many watts you have available, you multiply the Volt with
the Amps. Our sample battery 60v 20A battery, therefore, has 1200w of power when it is fully charged.
Watt is how much energy you have volt multiplied by amps = Watt Example 60V x 20A = 1200W
So if you have a motor that uses 500W at full capacity, your battery will last almost 2 .33 hours if you run it at max all the time. Petrol and electricity work the same the bigger the load, the more it uses.
Charging is how you refill your battery (Put the Amps back in the battery). To refill a battery with energy, we use a charger designed for the battery. The best way to refill the lead-acid battery is to do it slowly.
When you charge the battery too fast, you generate heat that causes damage to the battery. We will supply a charger that will recharge the battery in approximately 8 hours (between 6 to 10 hours is good practice)
The charger you get with your vehicle will stop charging when it reaches the set capacity, and it will stop charging the battery. Chargers show a red light when it is charging a green light when it is complete. Some
chargers have a float charge function indicated by an amber light
So as soon as the battery reaches a certain point, the battery charger cuts off, showing a green light. With most chargers, you have to switch the charger off and on again to get it to charge again. So the charger
will not overcharge the batteries. So if you have the time leave the charger till the battery is full. If you need to drive again before the battery is ultimately charged, it is not a problem; unplug the charger and use the
vehicle but remember it was not fully charged, and the range will be shorter.
Leaving the charger on will not damage the battery even when it is fully charged. But if you have a lot of Escom power failures, it will reset the charger, and it will charge until the next
check when it will switch off again. The high-quality chargers do this check every minute, but some do it once every 15 to 30 Min. That can cause damage. So if you have unstable power unplug the charger when you see it is complete.
Always unplug electrical equipment in heavy weather.
When you charge a lead-acid battery, you need to calculate the total voltage of all the batteries in your battery and charge till you get to that voltage.
In diagram one hereunder, we see that to get this battery full, you need to charge it to 12.9v, and that is correct. With a new battery, this does happen as the batteries will store the electricity at the same speed
to get the same amount of energy.
2.15 +
2.15 +
2.15 +
2.15 +
2.15 +
2.15 +
12.95 =
In the following diagram, you will see the exact same battery charged with the same charger, but some cells are full, some are overcharged, and some are only 40% charged. There are many reasons why this can happen. The charge rate of battery cells differs
when some are older than others. Some are warmer/colder than others. Some have more capacity, and some have less capacity.
An example of this was found with an Electric Quad bike with a double row of batteries. (10 batteries, five on each side connected in parallel and series to form a 60v pack) The batteries on the right side never lasted
as long as the ones on the left side. The first time I thought they must have had a problem from the start. But the second batch did the same. And this had me puzzled until one day when I got onto the bike and realized the
right side was baked by the sun every afternoon when the bike went on recharge, and the wall protected the left side.
This diagram clearly shows batteries at different levels after they were charged. The first sell and the 4th sell are in balance on the correct voltage. The rest of the cells are all out of balance, but the battery
is full 12.9v. It would be easy to predict whats is going to happen here
2.15 +
2.05 +
2.25 +
2.15 +
2.15 +
2.95 +
2.35 +
12.9 =
With a 60v battery, we have 5 batteries that form the 60v pack and one charger that charges all five batteries simultaneously. That means one charger that must keep 30 battery cells charged and in balance. The bigger the pact, the more chance there is
for a cell going out of balance; the good of a large pack is if one cell is out of balance, that other 29 is affected less than with 1 in five.
5 x 6 = 24 Cells
Now that you understand how batteries work, you should understand why you should never have old and new batteries in the same pack. The older the battery gets, the fewer amps you can charge into the battery. If you
have a 60v pack of three new batteries and two old batteries, the old batteries will overcharge, resulting in the new batteries undercharging. The charger will still charge up to peak voltage, but the smaller batteries will
be full faster and overcharge more. This will cause faster deterioration of the old batteries. Faster than expected, this will cause the new batteries to over-discharge, and you will lose all of them.
Lead-acid batteries are the cheapest battery pack. They work well if you look after them. We have clients that have used the vehicles every day for the past 4 years and still have no problem. Lead-acid needs a lot
of discipline and are more likely to get damaged if it is not monitored. And kids will be kids.
Why don't batteries last forever
Batteries accumulate lead sulphate crystals on the plates inside the battery. This cause a disruption in the normal functioning of the battery, and they will be able to store less and less energy and because the battery
store less energy, the discharge state is more every time you use it. So even if you look after the battery, it will get old. Eventually, you determine how soon that is.
When overcharged, or over-discharged or charged too fast, the lead plates heat up and deform, and thus reduce the capacity of the batteries as well
These factors will exhilarate the ageing of the battery:
- Storage for an extended period. Lead batteries discharge at a rate of 3 % per month. It would be best to charge lead-acid batteries every 2 to 4 months
- Storage in places with hot temperatures
- Fast charging generates heat, and this deform the lead plates
- Overcharging increase sulphate crystal forming and generate heat.
- Over discharging is the most significant cause of damage
- Sparks and short circuits - make sure terminals are checked regularly and that they are correctly secured.
- Storing the vehicle in a discharged state is very damaging. You should always charge immediately after using the vehicle. Never let them go to bed with an empty stomach."
- Gel lead-acid batteries are recommended for vehicles since the silicone gel electrolyte holds the paste in place.
