How To

How to Charge a AGM Battery?

AGM batteries charged right? AGM (Absorbed Glass Mat) batteries are currently being used by well-known home builders as a standard battery, in addition to the hugely expensive LiFePo4 battery.

Also, I can advise these batteries, if you are about to plan his campers, or if the old batteries are through. Keeping a few points in mind, AGM batteries last a while.

Here I want to tell you what you should consider, what size should have your AGM battery for your Campervan and what is there for little helpers.

Understand how to charge AGM battery

To tackle the topic properly, we first have to look at a few small issues. We want to do that, so that not only does your AGM battery charge also but adequately extends its lifespan through proper handling.

I already wrote something in my contribution to batteries. To understand everything, you should look at the post.

Capacity – how much you can take with AGM batteries

A lead-acid battery, including the AGM technology, falls, you should max. 20 – 40% of the total amount to achieve the highest possible number of cycles. That means, with a total capacity of 100 Ah, you should not take more than 20 Ah to 40 Ah before you recharge your battery.

If your solar system charges every day, the whole bill looks different, of course.

On the subject of solar systems, I have already put together some information for you.

Installation of an AGM battery – not upside down

The installation of an AGM battery is probably limited only by their dimensions. Otherwise, you can install them in any situation. The only thing to keep in mind is that you do not stack the batteries.

Load temperatures for the AGM battery

If you store and run the camper battery at around 20 degrees, you will never have problems. Also, most chargers now have temperature sensors that adjust the charges to the ambient temperature.

Cold is of course not optimal, but the AGM batteries can handle the cold best, which is also reflected in the cold-start current characteristics.

At temperatures above 50 degrees, you should be careful. The batteries do not handle well and you should see that you get them out of the heat.

Charging procedure for the AGM battery

Fortunately, today we are in state of the art, which forgives us very much. So most chargers have the right charging characteristics for the different battery types stored.

An IU characteristic is standard when using an AGM battery.
If there is an IUoU characteristic, this is better.

Also, the end-of-charge voltage at which the batteries begin to outgas is important. With an AGM battery, you should make sure that the charging voltage never exceeds 14.8V. Check this with your voltmeter directly at the poles of the battery. So you can quickly find out if the purchased charger is working properly.

Load the IU characteristic for AGM battery

The IU lead or the CCCV (constant current-constant voltage) method charges during the charging phase of the battery with a constant current and a slowly increasing voltage.

The charger will now constantly measure the current and voltage values during charging. When reaching the end-of-charge voltage, the current drops. The charge is continued with a low current and a constant voltage.

An IU characteristic loads during the main phase with a constant current and a slowly rising voltage, which remains constant after a certain charging time. After reaching the charging voltage, the power drops and it is recharged with a small current.

Load the IUoU characteristic for AGM battery

The IUoU characteristic works in the first steps as well as the previously described IU characteristic. Here, however, is switched on reaching the rated charging voltage to a trickle charge, which should counteract the self-discharge of the battery.

The trickle charge is 13.8 V with a lower current. Since the self-discharge of a battery depends strongly on the temperature, chargers with a temperature sensor are recommended.

If the voltage deviates from the nominal charging voltage, the chargers normally start from the beginning.

Charge your AGM RV battery over the solar system

Most solar charge controllers have also stored all the necessary characteristics. But since the characteristics are also implemented sensibly, you need a certain amount of current or sufficient voltage.

As it depends very much on the weather, which can be done by your controller, you can only recommend one MPPT charge controller here. This ensures even in low sunlight for sufficient voltage and ensures that the battery is fully charged. Here I can advise you of cheap equipment only.

Charge your AGM battery with the alternator

That too is possible and even meaningful. While driving, the alternator is running and electricity is being generated. Often more than the starter battery of the vehicle needed. Here you will find cheap cut-off relays on the market – the starters – and also your AGM supply battery will be charging while driving.

If you disconnect the relay disconnects and you only take power from the AGM supply battery.

Sounds reasonable. Unfortunately, this solution is not exactly optimal – the alternator usually has the task to charge your starter battery and it is designed for that.

Thus, this provides a certain voltage and a certain current. An AGM, for example, requires a very different charging voltage than a lead-acid battery.

Also, we can assume that you get the power supply battery more power every day than the starter battery – but this is while driving fully fall voltage and power.

The result is clear – the second battery is not full. Your AGM battery would starve.

To properly charge a body battery with the alternator, you need a 12V charger or a so-called B2B charger. Here you can connect several batteries and also select the right battery types.

So right charging curves are used and all your batteries are properly and, above all, fully charged.

Get four tips for AGM batteries

1. Set your charger to the correct battery type and observe the installation instructions.

2. Do not take more than 20% to 40% of the total capacity of your batteries. She will thank you.

3. Check with your voltmeter to see if the end-of-charge voltage is not exceeded, thus preventing outgassing.

4. Use an IU characteristic, even better an IUoU characteristic.

If you stick to these four rules, you will be happy for a long time with your AGM RV batteries. And even if they lose capacity after a few years, that’s no reason to replace the battery immediately. Keep using it until it stops. So you have the optimal use of the battery and also protect the environment.

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