By admin ~ December 12th, 2008. Filed under: New Electronics.
“Buzzing” Your Battery
Giving your battery a “pulse”
might extend its lifeBy Frank Lanier
One of the newest products of interest to dedicated cruisers is the PulseTech Xtreme Charge battery charger. Used by itself or in conjunction with a boat’s normal battery charger, the high frequency pulse charging waveform delivered by a PulseTech charger is designed to increase the life and performance of a lead-acid battery by reducing the loss of storage capacity caused by the accumulation of lead sulfate in the battery’s plates.
The conventional method for recharging a lead-acid battery is to apply direct current at a voltage somewhat above the normal full-charge voltage of the battery (about 13.2 volts for a 12-volt battery). The PulseTech battery charger does the job a bit differently. It intentionally adds very high frequency electrical pulses to the DC charging voltage to modify the physical nature of the lead sulfate created to a form that is more easily reconverted to spongy lead and lead peroxide.
Battery chargers have been with us since the invention of the lead-acid battery by Gaston Planté in 1859. It’s reasonable to assume that the process of recharging these batteries would have been thoroughly explored and understood long ago. However, continual developments in electronics during the past 40 years have created major changes in the way our battery chargers work and have led to better battery performance and, in some cases, substantially longer battery life.
The standard marine battery charger in the 1970s was a ferro-magnetic device which comprised a large, heavy transformer, a capacitor and rectifier diodes. Its most positive attributes were its ability to deliver a constant charging voltage to the battery even if the AC line voltage was varying and its extraordinary reliability. Units built in the early 1950s are still in use. However, the ferro-resonant charger had one serious flaw; it did not know when to stop charging the battery. If left unattended, it would eventually cause excessive loss of water from the electrolyte, drying out and ruining the battery. The addition voltage-sensing controls allowed the charger to cycle on and off, maintaining the battery charge without excessive loss of water.
Subsequent changes in battery charger design introduced the silicon-controlled rectifier. The same device used in your home light dimmer control, it made it possible for the charger to provide the stabilized voltage needed for safe charging without the need for the large, heavy transformer used in the ferro-resonant units.
The Physics of Charging
All battery chargers work toward a single objective; to reconvert the active lead peroxide and spongy lead material in the positive and negative plates of the battery that have been converted into lead sulfate during the delivery of energy back into their original state. The creation of lead sulfate, often cited as the cause of battery failure, is the normal and necessary process by which the battery converts its chemical energy into electrical energy. Almost all battery failures are the result of the gradual build-up of unconverted lead sulfate on the plates, which results in the loss of energy storage capacity.
PulseTech’s XtremeCharge battery chargers use two techniques claimed to be unique and beneficial for battery life. The algorithm that controls the charger’s microprocessor periodically assesses the condition of the battery, optimizing the charging process, and the charging current applied to the battery includes a high frequency AC pulse component intended to modify the structure of the lead sulfate crystals clinging to the battery plates. According to David Sykes, chief engineer of PulseTech, the 30-volt AC pulse is a trapezoidal waveform that peaks and decays in a total of 19 microseconds. The photographs on the PulseTech Web site (pulsetech.net) under the Technology tab provide an interesting view of the claimed result of using their charging technology.
I connected a 100X200 12-volt 2 channel XtremeCharge battery charger (MSRP $190) to two Group 27 batteries on my boat after first disconnecting the normal battery charger. The two sets of the XtremeCharge unit’s indicator lights cycled through the device’s software-controlled evaluation process, and finding the batteries in good condition, proceeded to charge them. The unit will not attempt to charge a defective battery.
Based on my time-limited evaluation, I believe this battery charger will be very useful on boats connected to shore power, especially those without costly multi-stage automatic battery chargers.
With a maximum charging current of 2.5 amperes, the XtremeCharge unit can’t quickly recharge a depleted battery. Since the XtremeCharge unit cannot substitute for my boat’s 40 amp shore powered charger when significant DC loads are operated, I considered if it could be used in parallel with the normal charger to obtain the high-frequency charging benefits claimed by PulseTech. Connecting the XtremeCharge unit to the boat’s batteries with the main charger connected as normal would defeat the unit’s microprocessor battery evaluation algorithm, however, the high frequency energy flow would still be present and should yield the desired positive effect. A discussion with Dave confirmed my conclusion that the benefits of pulse charging would be available to keep lead sulfate build-up in check, even when combined with a traditional charging system.
Solar Powered PulseTech
I evaluated PulseTech’s five-watt Solar-Pulse battery charger by connecting it to two parallel-connected Group 27 batteries in my boat’s main battery bus during the two weeks the boat was in the boatyard without an AC power connection. The solar power collected by the panel we placed on the deck just forward of the companionway was sufficient to keep the batteries at about 50 percent of full charge despite the small but continuous power drain created by the entertainment electronics memory circuits and the power consumed by the control for the Raritan Lectra/San waste treatment system in the aft head. The usefulness of a solar powered battery charger on a boat kept on a mooring is obvious; having one on an unattended boat connected to shore power that will keep the batteries charged even if the shore power is interrupted can have at least equal advantage.
Author’s note: Pulse charging of batteries is by no means a new idea. Our research of the technical literature disclosed a wide variety of techniques that claim to extend battery life. The chargers use modest amplitude pulses of substantial duration. Some accompany a positive pulse with a short duration negative pulse, claiming that the negative pulse improves the conversion of lead sulfate to useful reactive material. My literature search did not yield convincing substantiation for the claims made for pulse charging techniques other than those made by PulseTech.