Battery Equivalents and Replacements

How To Keep Generator Battery Charged

Power generators with remote and electric start feature built-in lead-acid or lithium starting batteries, which are required for cranking the internal combustion engine and for powering remote start electronics while the unit is in standby mode.

For a generator to be as reliable as possible, it is very important that its battery is fully charged and ready to be used at the moment's notice. However, some people wonder how to charge the generator's battery.

Updated: July 11, 2024.

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Generator Battery Charger

First of all, power generators come with detailed Owner's Guide/Manuals and explanations on how to maintain the power generator and how to store it over a longer period of time - if You have a power generator, but You never read the Owner's Guide, do yourself a favor and read it.

Does a power generator charge its own battery?

Every power generator featuring electric and remote start also features an onboard cranking battery - these batteries are mostly lead-acid batteries, but some newer power generators feature lithium starting batteries.

As soon as the engine has started, the onboard battery charger (part of the generator's electric/electronic system) starts to recharge the battery and keeps it fully charged.

So, if You use your power generator regularly, on a daily or at least weekly basis, your battery will practically always be fully recharged.

Power generator battery types

Most power generators feature 12V rechargeable batteries with a nominal capacity in the 5-20Ah range.

As said before, most power generators feature lead-acid onboard batteries, which are relatively heavy, but they tolerate vibrations very well, can be easily charged, and are rather cheap.

Lead-acid batteries can be flooded/wet, AGM (Absorbent Glass Mat), and Gel-Cell batteries.

When used regularly, lead-acid batteries can last for a long time. But, when the unit is not used for a longer period of time, the battery must be recharged at least every 1-3 months, depending on the temperature and the exact battery model.

When being recharged using external battery chargers, lead-acid batteries should be charged using 0.1C-0.15C charging currents.

Lithium batteries are mostly Lithium Iron Phosphate (LiFePO4) starting batteries, which are not cheap when compared with similar lead-acid batteries, but they tolerate vibrations and mechanical impacts rather well, they are rather lightweight and must be charged using dedicated lithium battery chargers.

Lithium starting batteries feature a relatively low self-discharge rate and should be recharged every 2-6 months, depending on the model, using dedicated lithium battery chargers or charging modes.

When being recharged using external battery chargers, lithium batteries can be recharged using 0.1C-1.0C charging current, with 0.25-0.5C charging currents being often recommended.

Note: some power generators come with a dedicated battery charger/maintainer.

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How to Charge Generator Battery?

If you, for any reason, end up with a discharged generator battery, the most obvious solution is to crank the generator manually and let it recharge the battery on its own.

This is a recommended solution if you are going to use a power generator for hours to come.

If you don't intend to use the power generator for hours or not at all, then the best solution is to get a dedicated battery charger and connect it to the battery.

The battery charger will recharge the battery in a few hours; just be sure that the charger is chosen/dimensioned properly in terms of charging current, voltage, and battery type.

How to Keep Generator Battery Charged?

When the power generators are stored for a longer period of time, their batteries are disconnected in order to prevent any parasite load from discharging the batteries.

However, all batteries feature a certain self-discharge rate; lead-acid batteries usually have a faster self-discharge rate than lithium batteries.

Thus, when being stored, generator batteries should be recharged fully and then connected to the automatic battery maintainers, which will keep the batteries fully charged during storage.

The good thing is that modern, microprocessor-controlled automatic battery chargers are often designed as battery maintainers, allowing the users to store the power generator, disconnect the battery from the power generator, and connect it to the automatic battery charger/maintainer, which will first recharge the battery completely and then keep the battery fully recharged during storage.

One of the most popular battery chargers is the NOCO Genius2 2A Smart Battery Charger.

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NOCO Genius2 2A Smart Battery Charger is intended for charging 6V and 12V lead-acid batteries (wet/flooded, AGM, Gel, etc.) and 12V lithium batteries.

The charger is able to detect and recover deeply discharged batteries (down to +1V), and for fully discharged batteries (below +1V), it features so-called "Force Mode."

The unit is designed not only to charge the batteries but also to desulfate them (if detected) and, after charging, to maintain them fully charged.

To help with charging at high and low temperatures, the charger features a thermal sensor.

Thanks to all these features and acceptable price, the unit is one of the most popular chargers on the market, used not only for power generators batteries, but for both starting and deep-cycle batteries in the 10-20Ah (lead-acid) and 2-20Ah (lithium) ranges.

For more reviews and recommendations, feel free to check the NOCO Genius2 2A Smart Battery Charger Amazon link (the link opens in the new window).


Long Story Short: In order to keep the generator battery fully charged, crank the power generator regularly and let it recharge the battery. If the power generator is stored, using a dedicated battery charger/maintainer will keep the battery fully charged and ready for the next use.

Again, power generators come with Owner's Guides/Manuals describing maintenance procedures, including how to keep the batteries fully charged even when the generators are not going to be used for a longer time.