Most batteries are eventually wrecked by active material being progressively shed from the positive plates and shrinking on the negative plates; and also/especially by an effect, called sulphation, that affects both positive and negative plates. Because of the unusual usage, it is this latter effect that mostly concerns campervan/ motorhome owners. As a battery discharges, sulphur combines with the lead in the plates, forming lead sulphate in the form of fine crystals. These crystals are normally re-absorbed during charging. The effect is inherent and is harmless in batteries that are regularly and adequately charged and not overly discharged. But if the battery remains uncharged, even for a few hours, or is consistently under-charged, the sulphate hardens into larger crystals.

Hard sulphate crystallisation reduces the plate's effective area (i.e. the acid can't get to it), and hence the battery's effective capacity. In some circumstances sulphation causes the battery to lose its 'damping' effect, allowing high voltage spikes from the alternator to be imposed on connected electronic equipment. Hard crystallisation is a major problem with batteries used in equipment that is used intermittently, such as snow ploughs, aircraft ground equipment, military hardware, and clearly (from CMCA member correspondence) in many (most?) campervans and motorhomes.

It has been known for some time that imposing a low level alternating current and/or pulsing on the charging voltage reduces sulphation, and this is now being introduced into battery chargers for electric vehicles. It was also a feature of the TWC smart voltage regulator (that I have in my OKA) but it regrettably is no longer available. Another technique is to impose short high voltage pulses (of less than a millionth of a second) at a rate of up to 10,000 pulses a second. These pulses excite the atoms responsible for sulphation, and cause them to return to solution. This technology is now used by the military. Battery pulse generators have also been available commercially for some time. They are variously claimed to: enable more charge to be stored in a battery, to enhance starting ability, and to increase battery life. They are also claimed to resuscitate sulphated batteries.

German Testing

There seems ample evidence that these claims are generally provable. Germany's Institut fur Industrielle Elektronik und Materialwissenschaften (sic, - I really did not make up that name!) conducted tests over 10,000 hours with about 80 sulphated batteries. Half had measured amp/hour capacities averaging 61.6% (i.e. of new), the other half 36%. A MegaPulse unit was connected to each battery for 15 days (and supplied with energy from an external source). The batteries were fully charged at the end of the 15-day pulsing test and then tested for electrical and chemical changes. Tests were also conducted during the test period. Results showed that 97% of the batteries that initially had about 61.6% remaining capacity improved to an average of 87.5%.

The increase in amp/hour capacity of those that had 36% remaining capacity increased to over 82.8%. Cranking capacity was also measured and showed roughly comparable increases. The increases were almost linear over time - there was no fall off at the end of the test periods. It is highly probable, if unproved, that battery capacity would increase yet further over time. The results show averages with individual results being closely related to initial battery condition. Fourteen per cent of the batteries tested were not recoverable. The report concludes: '...86% of the tested scrap batteries regained their function ...[they] could be used again without limitations in automotive applications.'

CSIRO

A different form of test by Australia's CSIRO is less conclusive. This involved four (assumed) identical and new batteries that were subject to a slightly modified form of the American Society of Automotive Engineers SAE J537 cycling test. This test simulates taxi usage. It counts the number of charge/discharge cycles before the battery fails to maintain cranking at 470 amps for 30 seconds whilst remaining above 7.2 volts, (i.e. it's brutal: batteries are useless afterwards). One battery was left un-Megapulsed to act as a reference. Two batteries were fitted with MegaPulse units operating at 12.8 volts input. One was fitted with a MegaPulse unit working at 10.6 volts input. The CSIRO report notes that, '[at the end of the test] all test batteries were in very poor condition. They had suffered different degrees of sulphation, loss of mechanical strength, severe corrosion, material softening and extensive shedding.' Curiously the reference battery (that was not pulsed) returned exactly the same number of charge/discharge cycles (1233) as another one that was Megapulsed. A further battery, tested at 10.6 volts input, returned 1644 cycles and the remaining one, pulsed at 12.8 volts input, returned 2055 cycles.

The CSIRO summary cautiously notes that, 'the cycling performance and studies of plate morphology suggest that the use of MegaPulse technology can increase the service life of batteries through suppressing the size of lead sulphate crystals. Obviously, more experimental trials are required to establish this preliminary finding at an acceptable level of confidence.' My own research background leads me to feel the sample is far too small to be conclusive, and that it is unclear whether the results reflect the performance of MegaPulse units, or individual differences between the batteries when new (their standard deviation being fairly high for some parameters). Further, whilst valid for the purposes for which the test was commissioned, the SAE test does not reflect campervan/motorhome usage.

So where does this leave the campervan/motorhome owner? Firstly and importantly, a MegaPulse unit is not a substitute for regular or (preferably) float charging. It draws energy (about 80 milliamps, i.e. 0.8 watt) from the battery that it protects. It must also be used in conjunction with a suitable charger - but a continuously charged battery does not sulphate anyway. The technology appears to come into its own with batteries that are less than optimally maintained - which is probably most! There's a strong argument for its use with systems that routinely run low on power and, from the German tests, there's a good chance of restoring lost battery capacity if sulphation is not beyond the point of no return.

Australian reseller, Solar Express says that, 'most buyers are satisfied with the results, and some owners have bought several units. A few buyers have found that the units did not do what they had expected' [perhaps because batteries were beyond redemption - Ed] 'in these cases we returned the purchase price.' From the German results and anecdotal evidence, the unit seems worth a go in many applications. But it is not a substitute for charging. It is best used in conjunction with a small solar module permanently float-charging the battery, a small preferably 'smart' charger, or a 'trickle charger' that absolutely stays within 13.2-13.6 volts. Such charging will make a huge difference to battery longevity anyway! If lead-acid batteries in good condition are maintained correctly (i.e. kept close to fully charged at all times) then sulphation is unlikely to be a problem, and there's little point in using a pulsing device. But for vehicles such as campervans and motorhomes that are used only occasionally, a pulse generator, such as the MegaPulse unit tested, may well extend battery life for a worthwhile period, but it absolutely does not remove the need to keep batteries properly charged!