ECJ EUROPEAN Cleaning Journal

Cleaning machines all require high quality batteries to ensure performance and long autonomy. However cleaning is also one of the most challenging markets for manufacturers, as batteries often have to withstand to less than optimal charging conditions, deep discharging and intermediate charging. Micha Denys, export sales manager for Battery Supplies tell us more.

Sweepers, scrubber dryers and municipal cleaning equipment… they all require a set of high quality batteries for good performance and long autonomy. This makes the cleaning market a very interesting one for battery manufacturers and distributors. But it is also one of the most challenging markets where batteries often have to withstand less than optimal charging conditions, deep discharging and intermediate charging. It is highly recommended that sales of batteries in this market are accompanied by good advice as to how to treat the batteries, ensuring a long lifetime and good performance.

As most cleaning machines are intensively used, it is necessary to equip them with deep-cycle batteries that are fit for deep discharging. In open lead-acid battery technology, both PZS monoblocs (or cells) and US deep-cycle batteries are the best fit. Throughout the cyclic processes of discharging and charging the battery whilst using the equipment, the lead will start crumbling off the positive plates, eventually leading to the end-of-life of the battery.

In order to delay this as long as possible, battery manufacturers will try to add as much lead as possible into the positive plates. PZS monoblocs are mainly produced in Europe and contain tubular positive plates. This design allows the manufacturer to add more lead into the battery and this robust construction shows its advantage immediately in the lifetime of the battery: at a depth of discharge of 80 per cent, PZS monobloc batteries will from 1,200 to 1,500 cycles.

Alternatively, US deep-cycle batteries, mainly produced in the USA, are made of flat positive plates. However, compared to European flat plate batteries, the US deep-cycle’s positive plates are much thicker and better fit for cleaning machines than European semi-traction batteries. US deep-cycle batteries tend to perform from 700 to 1,000 cycles.

Open lead-acid batteries will give you a very long lifetime at the cheapest price. However, open batteries do require careful maintenance in terms of watering. A maintenance-free deep-cycle battery would definitely be an interesting option for users who want a plug-and-play and hassle-free battery system. In addition, not all product environments allow the usage of open lead-acid batteries and a maintenance-free solution would be then the only option.

The most commonly used maintenance-free lead batteries in this market are gel deep-cycle batteries. Gel batteries are perfectly fit for deep discharging and offer a lifetime of 550 to 600 cycles. An upgraded solution might be lead carbon deep-cycle batteries. Lead carbon batteries are maintenance-free, where carbon is added into the negative plates.

Carbon is one of the best conductors of energy and offers better energy uptake, throughput and release throughout  The advantage is their lifetime is almost double that of a gel battery. They also withstand intermediate and opportunity charging better, and have considerably higher performance in cold temperatures.

The disadvantage of sealed batteries is it is difficult to determine what could have caused an early fall-out of the battery: there is no acid density to measure and they are completely sealed. Very often a voltage unbalance in the battery set can explain an early end-of-life. The batteries in the set could be of a different batch. Or one battery can be somewhat weaker for whatever reason: after all, batteries are chemical products.

The weaker batteries will bring down the whole battery set if they are not identified at an early stage. A very good recommendation is to charge each battery individually before connecting them together into a set. Open batteries will equalise themselves during charging and correct any imbalance.

It is very important to consider the right charger. The performance of the energy pack does not only depend on the performance of the battery set, but also on the charger and the way the battery is charged! Many battery issues are caused by a poor battery/charger combination. First of all, as a general rule we advise that 12A charging output is minimally required to charge a 100Ah (C20) battery. If the charger is too light, or if not enough charging time is given, the battery will start to sulphate. And if the charger is too heavy, it might dry out the battery set.

Correct charging essential

Secondly, the charger needs to be set at the correct charging curve. Throughout the last 10 years conventional chargers have been replaced by high frequency chargers, and not only in the market of the cleaning machines. In terms of size, noise and most importantly charging efficiency, this has been a very good development. But this development didn’t come without risk: high frequency chargers charge batteries through a charge profile or charge algorithm. Each battery technology has its own charging profile.

And within the same battery technology, different battery brands might also have a different charging algorithm and charging a particular brand of battery with the charging curve of another might lead to a quick loss of battery runtime and early fall-out. Charging a battery set with a wrong charging curve may easily lead to battery issues within less than five months.

Most chargers have several charging curves that can be selected through a switch or have a user-friendly option to upload the required charging curve onto the charger (eg, via a USB stick). Information on how to charge the battery and which charging profile is recommended can usually be found on the technical datasheet. We strongly advise you to turn to your battery supplier for questions as to which charging curve on a particular charger model is preferred, especially if you decide to equip your cleaning machine with a fresh set of batteries of another battery technology.
Another interesting technology slowly finding its way into the cleaning sector is LiFePO4.

These ensure the longest possible battery lifetime available in the market, fully withstand intermediate charging and ensure an unmatched performance. They are controlled by a battery management system (BMS) that keeps the battery balanced at all times, monitors the battery parameters (voltage, state of charge, current, temperature), protects the battery and communicates with the external and internal output. In terms of return on investment there is no better solution than a LiFePO4 battery, but the initial cost is considerably higher than sealed lead-acid batteries and definitely open lead-acid batteries. And do opt for batteries with a (waterproof) IP66 certified housing.

PZS monoblocs , US deep-cycle batteries, gel deep-cycle batteries, lead carbon deep-cycle batteries and LiFePO4 battery solutions all have their specific advantages and disadvantages. And they are all available in the same sizes. It is the job of companies like ours to listen to your needs and to offer you the technology that will meet specific requirements.

But choosing the right battery for specific needs is one thing, it is also important to point out the many challenges batteries in a cleaning machine application are confronted with and to offer advice on how to maintain their batteries properly, how to check for unbalanced battery sets, to choose the correct charger setting if the cleaning machines is equipped with another battery technology - to ensure the charger is not too light, to avoid intermediate charging, etc.

Batteries are an expensive but critical part of your equipment. Out of all battery problems less than five per cent would technically be considered as a ‘production fault’. The rest would be due to poor battery maintenance (under watering or over watering) or less than optimal charging conditions (too much intermediate charging, undercharging, overcharging or bad charger/battery-combination). A well-informed customer will definitely benefit from a longer battery lifetime, longer equipment autonomy and higher performance overall.

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