Overheard at PFE

“We replace 50 percent of our car batteries every year. They go dead so often, eventually they won’t hold a charge.” Comments like that make most of us want to take that new fleet manager under our wing and do some good old-fashioned mentoring.
A number of tips immediately come to mind. Every single one has to do with upfitting. Today’s sedans, SUVs, and pickup trucks protect themselves from battery drain. You simply cannot make the battery on today’s factory-fresh vehicles go dead. The vehicle automatically shut-off drains on the battery, either by timer or by voltage sensing. So if a police vehicle battery goes dead over the weekend, or every few months, it’s because of the stuff we add to the vehicle.
With electronic devices, we cause two very different problems. One problem is a slow, low and steady amp draw even when devices are shut off or asleep. This is called a parasitic drain. A tiny 100-milliamp draw will cause a battery to go dead in eight days. A 1-amp draw will do it in 19 hours.
The easiest, least expensive solution is one of the battery-saving devices. There is at least a dozen different makes available. Battery-saving devices can be timer-based, voltage sensor-based, or both. Simply route the power for all the upfitted electronics through the battery saver and the vehicle will always have enough power to crank and start. No more battery replacements due to multiple deep cycling. 
Poor upfitting can also play a role. The number one rule of creating is, “Never cut or splice into an OE wire.” If the upfitter violates this rule, a battery draw could be an unintentional consequence. The clear trend is to run an entire wiring harness from bumper to bumper for all the aftermarket devices. Connect it directly to the OE battery, and use a battery-saving device on that circuit. Watch for the next trend: a plug-and-play device that connects to the OBD-II port for inputs you once had to tap an OE wire to get.
Another solution is an AGM battery like North Star, Odyssey or Optima. Clever fleet managers remove the OE battery during the upfit. The vehicle begins its service life with an AGM battery. More cranking power and longer battery life aside, the AGM battery is much more tolerant of deep cycling than an OE battery.
That means it can go dead, and then fully recover many times more than an OE battery. Deep cycle an OE battery as few as a dozen or so times, and it will not hold a charge. A thin-plate AGM battery will tolerate eight times that number of deep cycles.

The AGM battery costs two to three times what an OE battery costs. However, it will last the life of the patrol vehicle. In the very worst case, you will simply break even on the actual battery costs, not counting tows, jumps, installations, inability to respond, and downtime.
The other problem we cause is an amp draw that exceeds what is produced by the alternator. The battery is drained even with the vehicle running because current not produced by the alternator must come from the battery. 
The solution is to do some kind of amp-load counting and balancing. Total up the amp draw from electronic devices that you add: lightbar, laptop, spotlight, police radio, wigwags, in-car video, radar, in-car printer. That information is available for every device. 
This total amp draw should not exceed be available amps generated by the vehicle. Don’t be lulled into a false sense of security by today’s 200- or 220-amp alternators. The vehicle itself uses nearly all that the alternator produces. After that, any police device amp draw comes from the battery.

An auxiliary, electronically isolated battery is another option. Regardless, with a properly upfitted vehicle, you should never have to replace an emergency vehicle battery.

Published in Police Fleet Manager, Sep/Oct 2016

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