Battery Equivalents and Replacements

How Long Does It Take to Charge a Car Battery?

Regardless of the car battery type or brand, from time to time it may become necessary to recharge the car battery using the battery charger. Was the battery discharged due to the parasite load, multimedia devices, or for some other reason, is not the topic of this article - however, if that happens several times over a short period of time, check the alternator and the rest of the electric system of your car.

When the battery is taken out of the car, the car should not, and most modern cars cannot be used - in that situation, many people wonder how long does it take to recharge the car battery ...

car engine w300px

Short Car Batteries Intro

Car batteries are mostly lead-acid batteries using as starting/cranking batteries and for powering other electric loads while the engine is turned off.

Most lead-acid batteries are either wet/flooded or AGM (Absorbent Glass Mat) batteries, although some brands offer Gel-Cell SLA batteries as well.

Lithium-ion starting batteries are much lighter, but lithium batteries are not often used as starting batteries, but as deep cycle batteries in hybrid cars or electric-only cars, where their higher price is less important when compared with total weight savings.

Cars with internal combustion engines automatically recharge the battery and keep it (almost) fully charged all the time.

However, a car battery can become discharged for many reasons:

car audio amplifier- car wasn't used for a longer period (a few months, for example) of time and parasite loads (security system, for example) eventually discharged the battery,

- multimedia and other devices were used for a too long time while the engine was off,

- alternator or some other component of the onboard battery charging system failed, etc.

When something like this happens, perhaps the best course of action is to take the battery out of the car and recharge it using a dedicated smart lead-acid battery charger:

Note: some cars don't support battery removal except in the authorized mechanic shops (safety reasons) - before removing the car battery, check the Owner's Guide of your car to avoid any additional issues. Also, some battery chargers that feature desulphation and similar charging modes should NOT be used to recharge the car battery while the battery is still connected to the car electric system - spikes of high voltages used to break/remove deposits of lead-sulfate can damage the car's electronics.

Charging Current vs. Battery Capacity

Car batteries usually can accept charge very well, especially modern lead-acid batteries used for stop&go eco-driving.

However, when the battery is charged at home, in order to keep things as safe as possible, don't recharge the battery with the currents that can recharge a fully discharged battery in less than 4 hours.

For example, if the battery features a nominal capacity of 60 Ah, a smart multi-mode, multi-type lead-acid battery charger with the maximum charging current of 15 Amps is recommended.

15 Amps lead-acid battery charger can fully recharge 60 Ah battery discharged down to 80% DoD (not recommended situation, but it may happen) in under 4 hours easily:

60 Ah * 0.8 = 48 Ah → 48 Ah / 15 Amps = 3.2 hours

However, smart battery chargers analyze the battery and adjust charging according to the battery condition and in the end, they can even perform cells' equalization - that is why such battery chargers may require 4 hours, or maybe even slightly more in order to charge the battery with 48 Ah of current/charge required.

Similarly, smaller car starting batteries in the 45-50 Ah range can be quickly recharged using smaller battery chargers.

For example, if the Optima 8020-164 35 RedTop 12V 44Ah battery is discharged down to 80% DoD, 10 Amps smart battery charger can recharge it in under 4 hours, too:

44 Ah * 0.8 = 35.2 Ah → 35.2 Ah / 10 Amps = 3.52 hours

On the other hand, if You have a large 12V 100Ah battery that is discharged down to 80% DoD and You have 'only' 10 Amps battery charger, such battery charger can easily recharge such battery in under 9 (nine) hours:

100 Ah * 0.8 = 80 Ah → 80Ah / 10 Ah = 8 hours

Again, smart battery chargers don't recharge the battery the whole time with the same current - they are not 'Constant Current' chargers. That is why 10 Amps battery charger requires somewhat more than 8 hours to recharge the battery with the 80Ah of charge.

Note: if the battery has issues and the battery charger must go through desulfation mode and in the end, it also goes through equalization mode, the charging cycle itself can be even longer than 9 hours. If that happens, the best thing to do is to check the battery charger status and let it do its task - most probably smart battery charger just saved You the battery and prolonged its operating life ...

For charging smaller AGM, Gel-Cell, wet/flooded lead-acid batteries that are used in motorcycles, ATVs, snowmobiles, power generators, and similar, battery chargers in 1-5 Amps (sometimes even more) are used, depending on the actual battery size.


car in the wood w300pxLong Story Short: Car battery charging times depend on the battery capacity, depth of discharge (DoD), battery charger charging current, battery charger type, etc.

When looking for a suitable battery charger for your car battery, go for a smart AGM battery charger that also supports the charging of other lead-acid battery types (wet/flooded, Gel-Cell, Enhanced wet/flooded), but also if possible, that supports the charging of lithium-ion batteries as well.

Since most cars come with 50-100 Ah lead-acid batteries, battery chargers in the 10-15 Amps range are perhaps the best choice for 'quick charging' and avoiding additional load on the batteries.