Car battery
A powerful car battery is the heart of your vehicle's electrical system. It starts the engine, supplies lights and on-board electronics and buffers peak loads. Whether you are replacing a weak starter battery or looking for a new one for your vehicle with start-stop system – this guide from Electronicx GmbH explains all the important technical values, types and buying tips. Benefit from our experience and let us guide you competently through the variety on the market.
We compare AGM, EFB, gel and lithium technologies, explain important parameters such as Ah, CCA and cycle resistance, and give practical advice on care and accessories. So that you can reliably find the right car battery, Electronicx provides all information clearly, honestly and with real figures.
Which car battery is the right one? – The types at a glance
Not every vehicle can handle every battery. Modern cars with start-stop automatic generally require cycle-resistant AGM or EFB batteries. Older models manage with a low-maintenance flooded battery. The following table shows the differences at a glance.
| Technology | Typical Ah range | CCA (cold cranking amps) | Cycle resistance | Maintenance | For start-stop? |
|---|---|---|---|---|---|
| Standard lead-acid (low-maintenance) | 36–110 Ah | 300–750 A | 200–400 cycles | low (may need topping up with water) | only without start-stop |
| EFB (Enhanced Flooded Battery) | 45–95 Ah | 400–950 A | 400–700 cycles | maintenance-free | for simple start-stop systems |
| AGM (Absorbent Glass Mat) | 50–105 Ah | 600–900 A | 600–1200 cycles | maintenance-free, vibration-resistant | for demanding start-stop systems |
| Gel (VRLA) | 50–90 Ah | 450–850 A | 500–800 cycles | maintenance-free, leak-proof | partly compatible, partly not recommended |
| Lithium (LiFePO₄) | 12–40 Ah | 400–1200 A | over 2000 cycles | maintenance-free, extremely light | only with manufacturer approval |
The decisive factor is your vehicle manufacturer's approval. If in doubt, we recommend consulting the owner's manual or a brief consultation on +49 7135 7194106.
Ah, CCA, voltage – the most important parameters
When buying a car battery you will come across technical figures that are often confusing for laypeople. Here are the most important ones in detail.
Nominal capacity in Ah
The ampere-hour rating (Ah) indicates how much electrical charge the battery can store. A 70 Ah battery theoretically delivers 70 amperes for one hour; in reality, capacity is usually measured over a 20-hour discharge period (C₂₀). Typical values for cars: 36 Ah (small cars) to 105 Ah (upper class, SUV). Too small a capacity leads to starting problems in the cold and a shortened service life, while too large a capacity can place unnecessary strain on the electrical system – so stick to the manufacturer's specification.
Cold cranking current (CCA)
The CCA value (Cold Cranking Amperes) describes the current that the battery can deliver at −18 °C for 30 seconds without dropping below 7.2 volts. This is the decisive value for reliable starting in winter. Typical values range from 300 A (small cars) to 900 A (large diesels). An AGM battery with 760 A CCA starts reliably even at sub-zero temperatures. Diesel drivers in particular should look for a high CCA.
Nominal voltage and resting voltage
All common car starter batteries operate at a nominal voltage of 12 volts. When fully charged, the resting voltage is around 12.7–12.8 volts. If it falls below 12.4 volts, the battery is already partially discharged. If it remains below 12 volts for a prolonged period, deep discharge threatens, which permanently damages any starter battery. That is why you should have the voltage checked before winter.
How to find the right car battery
The ideal car battery depends on your vehicle model, the season and your driving profile. Bear the following selection criteria in mind:
- Vehicle registration document and manual: These state the capacity (Ah) and cold cranking current (A). Be sure to follow them.
- Case size and terminal arrangement: Batteries come in standardised case sizes (e.g. H5, H6, H7). The polarity (positive on the right or left) must match the wiring harness. Mismatches can often be corrected with terminal adapters – more on this in our guide to battery terminal adapters.
- Start-stop system: Models with recuperation absolutely require an AGM or EFB battery. A conventional flooded battery would fail within a few months.
- Additional consumers: Many electrical aids (seat heating, multimedia, auxiliary air conditioning) place a load on the battery. AGM technology with a high reserve capacity offers reserves here.
We will gladly help you with your selection by phone or email ([email protected]). All batteries are dispatched from our base in Cleebronn (Baden-Württemberg) – with free DHL shipping within Germany.
Extend service life – 10 professional tips for your car battery
With careful treatment, the service life of a car battery depends on use, charging, temperature and care. EFB and AGM batteries often last longer, and lithium types even longer. The most common causes of death: deep discharge, cold and incorrect charging. In our detailed article Extend battery service life – 10 professional tips you will find all the details. Here is a summary:
- Drive regularly: short journeys under 10 km are not enough to fully recharge the starting drain.
- Check the resting voltage: measure the voltage every three months. If it is below 12.4 V, charge immediately.
- Avoid the cold: store the vehicle in a garage or protect the battery with an insulating mat.
- Clean terminals: corrosion increases contact resistance – clean the terminals with a wire brush.
- No unnecessary consumers when stationary: avoid the radio, interior lighting or seat heating with the engine switched off.
- Use a smart charger: even in summer, a trickle charger can prevent sulphation.
- Disconnect during longer periods of non-use: otherwise the quiescent current will discharge the battery within 3–8 weeks.
- Never fully discharge the battery: a lead-acid battery that falls below 10.5 V is usually irreparably damaged.
- Observe the charging voltage: AGM batteries tolerate a maximum of 14.8 V, gel a maximum of 14.1 V. The wrong chargers destroy the structure.
- Charge immediately after every deep discharge: even one day in an empty state can lead to irreversible sulphation.
Heed these rules and your new battery will serve you faithfully for many years.
Charging and chargers – what you need to know
Even an optimal alternator rarely fully charges a starter battery in everyday use. That is why the correct handling of external chargers is crucial. You can read all the essentials in the Battery charger FAQ. Here are the key points:
What charging current is sensible?
As a rule of thumb: charging current in amperes = about 1/10 of the capacity in Ah. A 70 Ah battery is therefore charged at 7 A. Modern IUoU chargers adjust the current automatically and are gentle on the battery. For trickle charging, 1–2 A is often sufficient.
AGM vs. flooded battery – end-of-charge voltage
AGM batteries require a charging end voltage of 14.7–14.8 V, while flooded batteries manage with 14.4 V. The wrong programme can lead to drying out or overcharging. Look for a charger with specific charging characteristics.
Charging in the vehicle or removed?
You can charge the battery while it is installed, provided the charger is suitable for in-vehicle use and has an overvoltage protection function. With lithium starter batteries, a separate charger is often required because of the BMS. If in doubt, ask us – or take a look at the FAQ.
TPMS sensors after a battery change – don't forget!
In vehicles with a tyre pressure monitoring system (TPMS), you should check after every battery change whether the sensors need to be relearned. A voltage drop caused by disconnecting the vehicle battery can erase the stored sensor IDs. The warning light then comes on and the sensors report no pressure. Relearning is often possible with a diagnostic tool, but depending on the model a short drive may be enough. If the sensors themselves have a flat button cell, we can help you with the right sensor – check in our TPMS sensors section whether your vehicle model is listed.
Buying a car battery online – safely at Electronicx
As a specialist retailer based in Cleebronn, Electronicx GmbH supplies high-quality starter batteries to private and commercial customers every day. Why buy from us?
- Tested quality: we stock only branded batteries with clear technical documentation.
- Free DHL shipping: within Germany we ship free of charge by DHL. That way your new car battery reaches you after just 1–2 working days.
- We also deliver to Stuttgart, Cologne or Frankfurt, as a rule within 1–2 working days.
- Genuine advice: call us on +49 7135 7194106 or write to [email protected]. We advise you honestly and on a sound technical basis.
Shipping is from our warehouse in Cleebronn (Hindenburgstr. 37A, 74389 Cleebronn). Deliveries to Austria and other countries are also possible, but then subject to a charge. Please contact us for an individual quote.
Managing Director: Andreas Emschanow · VAT ID: DE300176428 · HRB 752730 Stuttgart District Court
Frequently asked questions about car batteries
How do I recognise that my car battery is weak?
The engine turns over only sluggishly when starting, the interior light dims when starting or the radio loses its stations. A voltage drop below 12.2 volts at rest is also a warning sign. In modern vehicles a warning message often appears in the on-board computer.
Can I fit a more powerful battery, i.e. more Ah?
Yes, as long as the physical size and polarity match and the alternator is not overwhelmed by the higher charging current. As a rule, a margin of 10–20 % more capacity is unproblematic. However, the engine control unit may need to be told about the new battery – especially in start-stop vehicles.
My car has start-stop – do I absolutely need an AGM or EFB battery?
Yes, absolutely. A conventional flooded battery will not withstand the many charge/discharge cycles and can fail within a few weeks. EFB is suitable for simpler systems, AGM for demanding ones with recuperation. Follow the manufacturer's approval.
How do I dispose of my old car battery properly?
Starter batteries are hazardous waste and must not go in household rubbish. Take the old battery to a recycling centre or return it to the retailer when buying a new one. The law obliges sellers to take them back free of charge. We will of course also accept your old battery.
Can I fit my car battery myself?
In most vehicles fitting it yourself is straightforward, provided you observe the polarity and secure the battery firmly. Make sure you disconnect the negative terminal first and reconnect it last. In vehicles with start-stop or on-board power management, the new battery often has to be registered with a diagnostic tool – this may require a specialist workshop.
How long does delivery of a car battery from Electronicx take?
With our free DHL shipping within Germany, the battery usually reaches you within 1–2 working days. Special deliveries to Austria or Switzerland are subject to a charge.
Is a lithium starter battery suitable for my car?
Lithium iron phosphate batteries (LiFePO₄) are extremely light and cycle-resistant. They are suitable for special requirements, such as in motorsport or in motorhomes. For standard operation, however, the vehicle manufacturer must approve their use, as the electrical system and charge management must be designed for them. If approval is unclear, it is better to stick with proven AGM or EFB batteries.