Gel Battery Charging: Ultimate Guide

Introducing the Gel Battery Charger

If we’re to understand how to charge them, firstly, we need to know what are gel batteries and how do they work?

Gel Batteries

Let’s talk about Gel batteries. They’re lead-acid batteries, but different from the normal kind.

The “normal” kind, that is the most common and the traditional type of lead-acid battery, is called Flooded (or Wet). These batteries have a lead (and lead oxide) plates within the battery casing, and surrounding the plates is a liquid solution. The liquid solution is called the electrolyte. It’s a mixture of distilled water and sulphuric acid (H2SO4).

The chemical reaction between the plates and the electrolyte results in an electric charge, which can then be used to provide power.

How are Gel batteries different?

Gel batteries also have lead and lead oxide plates.

But the electrolyte is not liquid. It’s still a mixture of sulphuric acid and distilled water. But it has something called silica (silicon dioxide) added, and this turns it into a gel.

Why are Gel batteries better than Flooded (Wet) batteries / normal lead-acid batteries?

Because the electrolyte being a gel makes several important improvements to how the battery works.

• It prevents extremely dangerous spillages and leakages ie. it’s much safer
• It completely solves the acid stratification problem – that’s something that kills normal lead-acid batteries. It’s when the liquid electrolyte separates into layers and lowers the battery’s power.
• It lessens sulfation. Sulfation is the number 1 killer of all lead-acid batteries – making most of them die long before they should. So Gel batteries can last much longer than other kinds.
• The internal makeup of Gel batteries is much more resistant to vibration. Flooded batteries have components that can break apart over time.
• Gel batteries cope much better with deep discharge, and variations in charging cycle.

FYI, there is one battery type that has these same advantages but can last at least 5 times longer, and you can discharge it up to 90%, that’s the Lithium leisure battery, the best for motorhomes, campervans and caravans.

Charging Gel Batteries

So how does the unique nature of Gel batteries change how we charge them?

Use the right charging voltage

Gel batteries don’t like too high a voltage. The ideal charging voltage for a Gel battery is around 14.1 – 14.4V.

Some battery chargers can go up to 14.7V and beyond.

AGM Charging As A Comparison

AGM and Gel batteries have been, to some extent, grouped together. They were developed at a similar time, they’re both classified as VRLA batteries and they both have alternative solution to the problems caused by having electrolyte as a free-flowing liquid, in Flooded batteries.

But they have very different charging needs.

AGM batteries need a higher charge than normal Flooded batteries. Around 14.7V is ideal. If they don’t get such a high charging voltage, they’ll suffer. They won’t be fully charged and they’ll become more easily sulfated. Which leads to less power and eventually, battery death.

But Gel batteries can be seriously damaged beyond repair, by such a high charging voltage as 14.7V. 

Be careful with old chargers

If you’ve got quite an old battery charger, be careful when using it to charge Gel batteries. They may have bulk, absorption, float and equalization modes.

Some of these modes may have too high a voltage, particularly equalization. Equalization mode is to fix acid stratification, and involves putting a high voltage across the battery to cause electrolysis. This is a type of controlled gassing, which causes the electrolyte to mix better again.

As we discussed, acid stratification isn’t even possible with Gel batteries, so it wouldn’t be needed anyway.

Don’t charge too quickly

Gel batteries don’t like being stuffed with charge. It can damage the internal components, even cause the gel to burn.

So make sure your charger is not too high an amperage.

Don’t discharge too quickly

Gel batteries are ideal for deep cycle applications. Long, slow, steady discharge is what they like and are best suited for.

Sudden, very high discharge can damage Gel batteries.

Slow charging cycles, then, is the name of the game with Gel batteries.

Very long discharge rates are possible, as a result of the large electrolyte reserve. This makes them ideal for solar applications, for example.

Best Charger for Gel Batteries?

Some of the advice on Gel battery charging elsewhere on the web is very old. They say it’s risky to use a lead-acid battery charger. You must use a fixed voltage charger, because a lead-acid charger will have a tapered voltage charge, which can be dangerous to a Gel battery.

And that used to be the case. That’s why we say to be careful if you have an older charger – it may have a mode which will provide too high a voltage. 

But the modern chargers have been modified to recognise Gel batteries and reliably provide the correct charging voltage.

We’d still recommend being careful with some chargers on the market, they may not have changed their technology for some years, to take account of Gel batteries. They say “Suitable for all lead-acid batteries”, but they haven’t actually changed their technology or updated their microprocessers to provide the right voltage for Gel batteries.

So we recommend either CTEK or NOCO battery chargers. These companies have the most advanced technology, there’s no chance of overcharging your Gel battery.

CTEK Battery Chargers

CTEK chargers have the most advanced charging process in the world. Their 8-step process not only charges your battery, it heals it from any maladies it may be suffering from. 

Gel batteries don’t suffer from acid stratification, but can suffer from sulfation, which is the leading cause of death for lead-acid batteries. CTEK’s first step is always to remove sulfation from the battery plates. This can lengthen your battery life considerably, even by 2 or 3 times more.

The CTEK MXS 5.0 is their 5 Amp charger. It has the 8-step process mentioned, and proven ability to revive batteries and make them last longer.

The CTEK MXS 10, as you may have guessed, has the same qualities as the MXS 5.0, but with 10 Amp charging. For larger vehicles, this more powerful charging is needed. And it’s faster.

NOCO Battery Chargers

NOCO chargers are of similar high quality. 

Their advanced charging system means there’s no chance of overcharge. And their system is set up to recognise Gel batteries, they’ll always deliver the right voltage at the right time.

Like CTEK’s chargers, they have an excellent desulfation mode, which reconditions the battery. This is called 12V Repair Mode. It will also repair sulfated batteries and as long as you use this mode occasionally, it will make your battery last much longer.

The NOCO Genius 5 UK is their 5 Amp model, it’s ideal for smaller to mid-sized vehicles of all kinds.

Those with larger vehicles should go for the NOCO Genius 10 UK. The 10 Amp charging will ensure the battery gets enough power when charging.

If you want to charge your gel battery using your vehicle alternator, you can! You’ll need a DC to DC charger, we’ve done a review of the CTEK D250SE, it’s the best one on the market.

We’ve also done a deep dive on the top leisure battery chargers in the UK.

Summary of Gel Battery Charging

Gel batteries have some fantastic advantages over normal Flooded lead-acid batteries that make them more suited for leisure applications.

We’ve shown you how Gel battery charging is simple and easy as long as you follow some basic rules and use the right type of charger.

Theis is particularly true for Solar or Outdoor/Leisure applications. Gel batteries have better ability to cope with deep discharge, periods of being unused, and the variations in charging regimes.

Take care, though. Make sure you don’t overcharge them. Treat them kindly with your charging process and they’ll look after you very well for many years.

Here’s where to check out the CTEK and NOCO chargers:

CTEK MXS 5.0 is here.

CTEK MXS 10 is here.

NOCO Genius 5 UK is here.

NOCO Genius 10 UK is here.