High Capacity Units By Ron Geier The questions that I’ve posed about the high capacity unit sales ads has become my own Pandora’s Box. I found the area more complicated and dangerous than I suspected. The large OE unit manufacturers seem to ignore these problems, and the unit solutions are provided by small companies whose experts are more likely “field” engineers than degreed engineers. In spite of this, the units seem to perform as advertised. The subject is so varied and complicated that I find that I can only provide an overview in this article. The high end charging systems industry is divided into roughly four dif- ferent areas. All of them contain traps and challenges that might not be appar- ent to the average rebuilder. These areas as I have identified them are: industrial; recreational/emergency vehicles; snow- plow/tractor; and passenger cars/light trucks with high end stereo systems, lights or other electronic gadgetry. The industrial area’s needs seem to be mainly focused on special environ- mental problems and/or customized charging curves rather than extremely high output. I don’t plan on dealing with this area in this article. The snowplow/tractor area is the only one that still is relatively straight- forward. Both areas have modest increases in electrical loads and they tend to operate at high rpm. These vehicles can be serviced with 10SI 100 amp, 12SI 94 amp, Niehoff 100 amp and/or 90 amp Motorola units. Very little rewiring or battery modification is normally required. Therefore, most rebuilders can sell these units to an unskilled installer and have little addi- tional warranty problems. The need for charging systems for the high end stereo market has been around for several years, but only with the advent of computer controlled emissions systems did it become com- plicated. The alternator is linked with the emissions system through the computer and when tampered with can void the vehicle’s warranty. It seems the alternator is under the emissions 50,000 mile warranty when modified, but not under warranty when it wears out. If a customer decides that he wants a “killer” stereo in his new Honda then he’s left stranded by his dealer. The aftermarket has addressed this problem in different ways. The first and oldest way of solving this problem is to replace the original alternator with a modified domestic unit of the correct output. Adapt or modify the unit so that it mounts and make the electrical interface as simple as possible (preferably one wire). This worked very well in the days of carburetors before computers, but in most newer vehicles can cause drivability problems. The computer doesn’t know what to do and can’t totally adjust to the increased loads of the higher amp units. Another problem with this type of modification is with normal electrical system service. Many service garages will not service a modi- fied electrical system. The second and more recent way of dealing with this problem is to locate or manufacture a unit that “looks” like the original but is ultra high amp; then add the highest capacity battery that will fit without major modifications. For regu- lation, an original type regulator is used. The combination of correct appearance and original regulator minimizes the drivability problems and keeps the charging system close enough to OE to allow normal charging system service. This will normally work in stereo systems of up to 500 watts (RMS). An emerging mini-industry is form- ing around the 500 watt and up car stereo systems. Multiple batteries, mul- tiple alternators, battery isolators and custom redesign of the charging sys- tems are common. You must have the capacity to do full vehicle electrical service before entering this segment of the market. Good practical knowledge of auto electric service and a good understanding of direct current electri- cal theory are required. Another mini-industry is forming around the recreational/emergency vehi- cle area. This area needs ultra high out- put compact units with a high resistance to heat. These vehicles also involve multiple batteries, multiple units, isola- tors, custom system design as well as inverters for delicate AC powered test equipment. The same rules listed above for the 500 watt and up stereo systems apply to this area as well. There are additional warranty com- plications when working in these areas. A typical warranty on an all original car involves the replacement of the unit, only. When these extensive system type modifications are made the customer can believe that anything that fails in his electrical system from that point on is somehow the fault of your work. The value of the equipment is such that it is worth the costs to take you to court if they don’t like the way the warranty was resolved. For this reason, all garages need to have insurance to cover damage relating to their service work. Emergency vehicle work involves the potential of a warranty causing loss of life. In cases like this, everyon