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Getting the most out of your motive batteries

Published:  22 April, 2020

The tips apply to lead-acid motive batteries, which dominate in today’s electric industrial vehicles. Most are ‘traditional’ flooded lead-acid units that need topping up with water. Others, known as valve-regulated lead-acid (VRLA) batteries, require no top-ups. These sealed packs divide into gel and absorbent glass mat (AGM) categories. Included under AGM are thin plate pure lead (TPPL) products, with lower charging-related maintenance needs.

1. Read the instructions

Along with general maintenance advice, the battery’s instruction sheet or manual will contain detailed product-specific information and action points. Failure to follow specified procedures may invalidate warranties. If you are unsure or for any questions seek guidance from battery professionals.

2. Don’t overfill or underfill

In flooded batteries, lead plate electrodes are suspended in a sulphuric acid electrolyte whose level falls over time and must be topped up with water. Note, however, that there should be no watering within the first ten charge/discharge cycles. If the level drops too low, plates can be permanently damaged by exposure to air – reducing their capacity and lifespan. The battery may also overheat.

Overfilling may cause acid leakage during the next charge, as the electrolyte expands. Acid loss reduces runtime and can result in overheating – a major cause of poor performance, damage and premature failure in batteries.

Use only deionised or distilled water. Top up to the indicated maximum level. Do this immediately after charging, or 20 minutes before charging ends – by which time the overflow risk has passed. Don’t fill before charging. However, if plate surfaces are exposed, top up just enough to cover them before charging. Automatic watering systems are worth considering as a time-saving option and, of course, with VRLA batteries there is no need at all for filling or leak avoidance.

3. Check the electrolyte

Electrolyte level checks apply only to flooded batteries and tend to be scheduled after every ten or so charges. As the battery ages, increased water consumption may require topping up more often. Check a few cells more frequently to see if this is becoming necessary.

In conventional servicing, the specific gravity of each cell’s electrolyte is measured monthly. Strong variation between cells indicates a need for equalisation. Variation in open cell voltage is an alternative indicator, measurable most easily via an automatic monitoring device.

4. Watch charge levels

Avoid discharging any battery to below 20% of its charge capacity. Excessively deep discharge damages the battery, shortens its life and can make electrical components overheat. On the other hand, recharging long before the charge falls to 20% wastes battery life if you are using the more traditional battery technologies. Advanced lead-acid technologies such as TPPL exhibits better performance when they are frequently opportunity charged and kept at high State of Charge (SoC).

Both sealed and flooded batteries should be recharged immediately after falling to 20% SoC, as continued lack of charge encourages sulphation. This process, in which sulphate crystals form on the plates and reduce their capacity, is a major cause of battery damage. For the same reason, charge batteries fully before storage.

5. Watch the temperature

Extreme heat or cold during storage, charging or use will limit a battery’s performance and shorten its life. Refer to the product’s specific instructions for a clear definition of its acceptable and optimum ranges.

As a rough guide, never charge a battery whose temperature is below 10 °C or above 45 °C. If it emits excessive heat or a strong sulphur smell while working or recharging, stop and seek advice. After a full charge, let it cool for several hours before use. Keep stored batteries cool to minimise self-discharge.

Some battery technologies, both flooded and VRLA, with special charging profiles, have been adapted for operating in specific cold environments such as refrigerated food stores. Ask your local supplier to advise on the best battery and charger for these applications.

6. Keep it clean and tidy

Deal with small acid spills from flooded batteries using an approved cleaning liquid. Spilt acid not only corrodes terminals and other structures but may create conductive circuits that drain charge. Wetness can have similar effects on both flooded and sealed packs, so keep the battery, its tray and its surroundings clean and dry.

Check all battery and charger plugs, connectors and cables regularly for corrosion, wear and damage, including exposed wires and loose fittings. Checks by an electrical specialist, at least annually, must include measurement of the truck and battery’s insulation resistance.

7. Control recharging times

A battery’s capacity declines with age. Its service or cycle life is the number of charge and discharge cycles it can deliver before its capacity becomes non-viable. Each recharge uses up one of those cycles and brings the battery’s end of life closer. In standard lead-acid batteries, it therefore makes sense to delay recharging until the vital 20% charge level is reached.

For most batteries, ‘opportunity charging’ between post-shift charges wastes some of the potential lifespan. If the battery is also fast-charged, extra heat generation can reduce its life even further. These options should be used only for emergencies. The exception is with TPPL batteries. TPPL technology enables fast opportunity charging without damage or cycle life reduction, provided the battery is regularly brought back to its full state of charge.

Once charging of a traditional lead-acid battery has begun, don’t interrupt it. Allow a full charge every time. Before disconnection, switch off the charger and ideally leave it for five minutes. Overcharging – except for equalisation – is wasteful and damaging.

8. Equalise, desulphate and refresh

Variation in voltage and capacity between a battery’s cells may develop. They can be rebalanced using an equalisation charge: a deliberate and calculated overcharge, to a higher-than-normal voltage, typically once every five to ten charge cycles.

In flooded batteries, the same process helps ‘stir’ the acid, to restore a more consistent and effective distribution, and removes some of the sulphate crystals from plates. Batteries fitted with an electrolyte circulation system benefit from the mixing action of air pumped into cells.

Equalising charges are often applied at weekends, as they add extra time to the charging process and require a longer cool-down. See individual battery instructions on this and watch out for excessive temperatures during equalisation. Note that some chargers will equalise automatically.

Some chargers offer a desulphation charge function, which you apply before normal charging – but only when needed. There are also special machines that deliver high-frequency electronic pulses to remove sulphate crystals, although high levels of sulphation cannot be reversed. Batteries in storage, or discharging while parked, need a regular refreshing charge to maintain their condition.

9. Choose the right charger

For maximum battery health and performance, batteries and chargers must be fully compatible in terms of cables and connectors, voltage and current ratings, charging profiles and settings. The easiest way to assure this is by using combinations recommended by the manufacturer and supplier – which are sometimes a condition of the battery’s warranty.

Improve your battery and operational efficiency by moving beyond conventional, low-frequency, taper chargers. High-frequency (HF) chargers are more efficient and ‘kinder’ to the battery, with current supply tuned to its needs at each moment. The modular power design of some HF chargers adds further efficiency. To gain full benefit from advanced TPPL batteries, your charger also needs a fast-charge facility.

Consider HF chargers with intelligent functionality to reduce the scope for human error. These devices automatically recognise the battery type and measure parameters like its voltage, capacity, state of charge and temperature. They apply the ideal charging profile and switch themselves on and off at the perfect time.

10. Automate battery management

Automated aids to battery management and protection include the Wi-iQ battery monitoring device from EnerSys. This reports in real time on factors such as temperature, voltage balance and electrolyte level. It also gives warnings and provides a useful battery history log for analysis. In larger fleets, the Xinx battery operations management system, also from EnerSys, provides for optimised battery healthcare and efficient use.

For further information please visit: www.enersys.com