Rick's Free Auto Repair Advice

Battery maintainer

What is a battery maintainer?

Many DiYers confuse the function of a battery maintainer with a trickle charger. A trickle charger provides a constant low charge rate to a battery, but it’s not smart enough to shut off when the battery is fully charged. So it continues charging a fully charged battery, causing permanent damage. A battery maintainer, on the other hand, checks battery charge and shuts off when the battery is fully charged. As the battery discharges, it kicks in again to keep it fully charged.

A maintainer won’t overcharge your battery like a trickle charger

A maintainer will check the condition of your battery periodically and charge only when it needs topping off. It can be left on all the time without harming your battery.

When to use a battery maintainer

Use a battery maintainer when you don’t plan on using your vehicle for periods of two weeks or more. All lead-acid batteries self-discharge at the rate of 1-2% per day, depending on ambient temperatures. In addition to self-discharging, vehicle batteries also have a constant drain from the vehicle’s computers. The self-discharge and current drain can cause an unused battery to be almost 50% discharged in a few weeks and dead within a month. Non-use from Covid-19 lockdowns has proven that vehicles must either be driven or placed on a battery maintainer.

How to buy a battery maintainer

Lots of companies have entered the battery maintainer marketplace and some of them have absolutely no experience, so it pays to avoid the newcomers. Solar, Battery Tender and CTEK are well known companies that have been making battery chargers and battery maintainers for a long time. Their products are well made and are worth the money.

Must-have features for a battery maintainer

Not all car batteries are standard lighting ignition (SLI) flooded lead acid style. Many newer cars and trucks with start/stop technology use absorbant glass mat (AGM) batteries which require a special charging routine. Plus, if you plan to use your battery maintainer on your gasoline-powered outdoor power equipment equipped with a gel style lead-acid battery, you’ll need a charger equipped with a GEL recharging cycle.

How many amps do you need in a battery maintainer?

For more car and light truck applications, all you need is a 2 or 4-amp battery maintainer.

Charging cycles

Battery maintainers can be used to maintain a battery, but some can also be used to recharge a discharged battery. When a battery is discharged, it requires a multi-phase charging routine to recondition the cells without causing damage.

Clore Manufacturing Solar brand Pro-Logix PL2140 Battery maintainer

I’ve been using Clore Manufacturing Solar battery maintainer products for years. The solar prologixClore Manufacturing Solar battery maintainer Pro-Logix PL2140 Battery maintainer is one of the best on the market. It’s a 4-amp charger that can charge 6 and 12-volt batteries. It can handle SLI flooded, AGM, Spiral wound AGM, Marine, Deep Cycle, and Lithium (LiFeP04).

The Clore Manufacturing Solar battery maintainer PL2140 uses a “soft start” mode to recover severely depleted batteries to avoid overheating the plates. Then it uses a “recondition mode” to bring the battery back to operational condition. In addition, it has temperature compensation so you can charge in all temperature conditions. Plus, it has polarity protection to prevent battery damage due to the cross-connection of cables.

It connects to the battery with standard clamps, ring terminals for marine and deep cycle batteries, and a 12-volt plug for use in a power port. Selling price around $46 at amazon.

Battery Tender brand battery maintainers

Battery Tender makes many different models starting battery tenderwith a 750mA model and up to large commercial units. The Battery Tender® 6V/12V, 4A Selectable Lead Acid & Lithium Battery Charger (022-0209-BT-WH) is comparable to the Solar Pro-Logix unit. Use it to maintain an SLI, AGM, Gel or Lithium (LiFEP04) battery. It uses a fully automatic 4-step charging process that’s microprocessor controlled.

The Battery Tender unit is spark-proof and reverse polarity protected. It includes clamps and ring terminals for marine batteries. Selling price is around $70 at amazon

CTEK Battery Maintainer

CTEK also makes a variety of battery chargers ctekand maintainers. The CTEK Battery Maintainer

CTEK MXS 5.0 is a 4.3-amp model and is comparable to the Solar Pro-Logix. It works with SLI, AGM, Gel, and even the newer Enhanced Flooded Batteries (EFB). It’s spark-proof, has temperature compensation, a reconditioning phase, and reverse polarity and short-circuit protection. The CTEK Battery Maintainer Selling price is around $80 on amazon.

The unit comes with clamps and ring terminals
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