This is what I use.
Redarc Electronics have fielded many inquiries from customers over recent months relating to the problems experienced by them with the charging of dual or auxiliary batteries in late model vehicles. Simply the vehicle alternator was never designed to fully (100%) charge the main vehicle battery. It was however designed to maintain the charge of the main vehicle battery and run the electrical loads (i.e. lights, air-conditioner etc.) once the vehicle is running.
By introducing extra batteries into the vehicle charging system with the expectation that the alternator will recharge them from a partially or fully discharged state is not realistic. These problems have been exacerbated with the introduction of ECU controlled and temperature compensating alternators. These alternators can be found in late model vehicles such as the Toyota Prado with the D4D engine. They reduce the alternator output voltage to approximately 13.5 volts when the temperature under the bonnet reaches its predetermined level. So the charging of dual or auxiliary batteries regardless of where they are located has now become more difficult. New battery types (i.e. gel, AGM and calcium) also play their part in the ever-increasing challenge for the vehicle’s alternator to fully charge the dual or auxiliary batteries.
Redarc Electronics have successfully provided a solution to this problem with the release of the BCDC1220 - a Smart Start microprocessor controlled, in-vehicle, DC/DC 20 amp 12 volt, charging system. The BCDC1220, with its in-built smart battery isolator, will recharge and maintain the dual/auxiliary batteries to 100% by using one of its 3 charging algorithms (selectable on installation). The BCDC1220 includes special charging programs for Gel/AGM, standard (flooded) lead acid and popular Calcium type batteries and will step up the voltages to the required levels (from as little as a 9 volt DC input).
The BCDC1220 simply waits for the vehicle to start, sensing the charge from the alternator, and will then commence the charging of the dual/auxiliary battery. The first smart charging process is the ‘Boost’ stage. The BCDC1220 will then seamlessly switch to its second stage ‘Absorption’. Once the battery has reached a fully charged state the BCDC1220 will maintain the dual or auxiliary battery at 100% with its third stage ‘Float’.
The BCDC1220 was fully designed and manufactured in Australia by Redarc to overcome all the problems associated with the charging of dual or auxiliary battery systems, this includes:
• Alternator charging systemsBCDC1220
• Paralleled dissimilar battery types
• Voltage drop over long cable runs
• Over-current battery intake
• 24 volt DC vehicles charging 12 volt DC batteries