Battery Science - Shocked
Battery Science For The Rest Of Us
By Marcus DI Sabella
Photography by Marcus DI Sabella, E. John Thawley III
When an exhaust, coilovers, front lip, JDM interior trim or even power provided via ITBs or boost become standard fare, where do we go next? When all's been done and there's seemingly nothing more to do, might we suggest less as the new more? We speak, of course, of introducing weight reduction to your car's repertoire. Such a concept is not new since there's scarcely an aspect of vehicle performance that can't be improved upon by mass reduction. Indeed, a major reason why Hondas are such great cars is its favorable power-to-weight ratios. Removing interior bits and swapping items for lighter equivalents has become standard procedure, but only recently have we seen the compact, lightweight battery go mainstream.
The car battery: A necessary evil for enthusiasts of all walks. Every car needs one and, given their size, they're inevitably heavy. Lead is the main ingredient here, which the periodic table tells us is rather heavy. Smaller batteries contain less lead and are therefore lighter but are less capable of discharging electricity. So it becomes important, before choosing a lightweight battery as a means of performance gains, to better understand them and their implications. Are you interested in the pros and cons of lightweight batteries and your Honda? Read on.
Batteries are simply energy-storing power units called upon for operating electrical devices. They're made with lead plates that directly contact an electrolytic sulfuric acid solution. Lead-acid batteries use a liquid solution while dry cell, gel cell or absorbed glass mat (AGM) batteries use a liquid suspended within a solid medium. When a battery is connected to a circuit, electrons transfer between the plates, flowing electricity through the circuit to perform work.
Electricity flows based on two properties: voltage and current. Resistance is a property of the circuit, which impedes electrical flow and drops voltage. Voltage, resistance and current can all be mathematically related to one other. If high school physics left any impression you may be familiar with Ohm's law, where current (I) is equal to the amount of voltage (V) divided by the resistance (R) or I=V/R. The relationship makes sense. Relate volts to your engine's torque output and current to the car's speed. If resistance is high (a strong headwind or traveling uphill) a given amount of torque will result in a lower speed. This relationship is the basis for nearly all things electrical.
Resistance And Extreme Temperatures
The starter is the car's main electrical device in terms of power draw. The amount of power the starter requires to initially turn the engine over is related to the engine's size, compression ratio, number of accessories being driven, internal weights and friction. Each factor emits a greater mechanical resistance and that translates into electrical resistance within the starter system. To overcome it, a battery of adequate power potential must be selected. Likewise, in a car that has been modified in such a way that resistance has been reduced a smaller battery can be used.
It's also significant to understand that the chemical reaction that's taking place inside the battery is temperature sensitive. The energy discharge within creates heat. When subjected to cold temperatures, the battery becomes cold-soaked, inhibiting electron flow inside the electrolytic solution. It also promotes a sulfate barrier forming on the lead plates, which translates to higher internal resistance within the battery. Choosing a battery with low internal resistance is advantageous but a good rule of thumb is to use a battery warmer when you know it's going to get cold. This not only works for OEM batteries but lightweight ones too.
Conversely, high temperatures can cause the reverse to occur. When exposed to heat, batteries experience a lower internal resistance than normal. This might sound like a good thing but the result is a self-overcharging battery. A certain amount of internal resistance is needed in order to keep the chemical reaction in check. Otherwise, the lead plates will corrode and cause the battery to swell or expand. It can literally charge itself to death.
Cold Cranking Amps
Cold cranking amps (CCA) is an important figure to refer to when seeking a new battery. The general rule: Batteries should be replaced with ones with similar CCAs. Of course, this doesn't apply when choosing a lightweight battery since, in order to see a weight advantage, the battery will have just a fraction of a stock battery's CCA rating.
Look no further than the definition of CCAs to make sense of this. The rating was developed for colder climates. Like we said, batteries and cold weather don't get along so the rating represents the extreme. A battery's capacity is reduced roughly 35 percent when subjected to a temperature of 32 degrees F, for example. At 0 degrees F, capacity drops another 60 percent. It's for this reason the CCA rating was developed-to define a battery's ability to start an engine during cold temperatures.
The CCA rating is the amount of amperage a brand-new, fully charged battery can output at 0 degrees F for a full 30 seconds while maintaining at least 7.2 volts. It goes without saying that the strain a battery undergoes during this test is much worse than what it would otherwise normally be subjected to. In other words, a car may need a certain number of cranking amps to start at 0 degrees F, yet this number is only 60 percent of what the battery's actual rating is at normal temps. As such, when choosing a car battery, consider not just the CCA rating but also the intended climate. Even those living in cold climates tend to store their vehicles during the winter. A lightweight, low CCA battery can be used the rest of the year in cases like these and hooked up to a battery-conditioning device the remainder of the time, but don't always take the CCA rating at face value. Swapping a battery is just as reasonable a winterizing effort as changing to snow tires.
OEM battery-load testing is conducted at 50 percent CCA, indicating CCA ratings nearly twice that necessary to function properly. This means the standard issue '95 Civic 410 CCA batteries may be safely replaced with 205 CCA versions and start just fine. Practically speaking, any battery rated over 130 CCA will start such examples perfectly well in daily driving situations.
It's almost comical how battery companies manipulate ratings and figures to indicate the type of levels that make people feel safer purchasing them. The reality is, most Hondas exhibit fairly low starting requirements. Properly maintained and/or daily driven performance-oriented Civics, CRXs and Integras can get away with minimal battery power.
Sitting batteries drain over time, dropping the voltage available for starting. This capacity is defined by the amount of amperage a battery can dole out over time-its amp/hour (Ah) rating. For example, a 50Ah battery can power a 1-amp device for 50 hours, continuously, without being disconnected or recharged. So, the time it takes for a battery to drain depends on whether or not there's an excessive parasitic draw.
For reference, a '92 Civic's expected parasitic draw is roughly 10 mA, or .01 amps. A stock Civic battery is rated at about 40 Ah. This resting Civic would run completely dry in 4,000 hours, or about five and a half months. Compare that with an Odyssey PC545 that is rated at 13 Ah and will die in about 1,300 hours, or almost two months. Keep in mind though that you can forget about starting that Civic once below 10 volts and 12-14 days is just about the maximum any lightweight race battery should remain connected to a non-operating vehicle. The true compromise when opting for the lightweight racing battery is exposed. Sure, the 15 to 20 pound weight savings are nice but allowing lightweight batteries to sit for long periods of time just isn't possible. Notice though that the sitting time is still rather reasonable for a daily driver. In fact, daily drivers can expect lightweight batteries to last anywhere from three to five years, even longer when properly maintained.
The Death Of A Battery
Two factors can contribute to a battery's demise: overcharging and deep discharging. Overcharging occurs when batteries are subjected to excessive heat. Likewise, charging a battery too much or too often will result in similar consequences, only manually. Over-activating a battery's cells can cause its plates to corrode, severely shortening its service life. Generally speaking, temperatures above 100 degrees F should be avoided and compact, sealed batteries should never be charged above 2 amps.
Deep discharging is also bad because with each charge and discharge, material is removed from the inner lead plates. Once the plates shed material holes can develop, reducing the plates' surface area and diminishing electrical production. When left uncharged for long periods of time, the shed lead goes into solution, forming a lead sulfate buildup that collects on the surface of the plate and further inhibits electrical production. The lead sulfate crystals are difficult to break up during charging and can permanently impact a battery's well being. If a battery dies, it should be charged right away.
Recharging And MaintenanceGenerally speaking, once a battery discharges permanent damage may have occurred. If conditions permit, a battery may be recharged back to its full capacity or at least within a reasonable range of it. The process must be done slowly though. Lightweight racing batteries must be charged at a rate of 2 amps or less. Caution must be taken since most of these are sealed types, which means they cannot easily vent their hydrogen gases, resulting in overheating or explosion if charged at high rates. Bulging cases are evidence of overcharging or charging at too high a rate.
There are a few methods for charging and maintaining batteries. Most manufacturers offer idiot-proof, reverse-polarity protection in compact packages that are easy to store and use. Braille units, which maintain 12 volts at 2 amps and claim to extend battery life, are just one example. NRGCELL offers a battery conditioner that also doubles as a 1-amp float charger. Battery conditioners cycle the battery in a way that helps break up lead sulfate crystals, helping recover life from a previously dead battery, in addition to adding to and maintaining its charge. When searching for a tender/charger, look for units featuring overcharge protection. Some charger manufacturers offer the convenience of quick-connect terminals making charger/conditioner hookup fast and easy. Also, keep that battery between temperatures of 56 and 100 degrees F whenever possible. The best car battery maintenance is to simply not allow it discharge...so just drive more. No more excuses for that dead battery.
Follow these tips and you can enjoy the benefits of lightweight and compact size to enhance your automotive enjoyment in ways you never thought possible. Or, at the very least, shift some weight around, shed a few pounds and make room for something else underhood.
Battery Relocation The Right Way
Drastically reducing weight is not always practical when it comes to performance gains. Such is the case with batteries; simply tossing them altogether just can't be done. Sure, there're lighter ones but, even better, we can take a lighter one and move it to a more suitable location.
A front engine, front-wheel-drive Honda has a distinct handicap when it comes to performance. FWD is bad enough but its front-heavy awkwardness is the icing on the cake. Removing heavy items like batteries from the engine bay and placing them out back can provide greater balance and handling. As always there are considerations to take into account before taking wrench to hand. Two main considerations must be given credence before battery relocation can be planned: first, how to route the power cables and second, addressing hydrogen fumes.
Opt for heavy gauge wire (two-gauge is most common) when running cables to minimize resistance between the battery and starter. This will make the smaller/less CCA battery more feasible without causing excess resistance or prevent starting. Route the positive cable from the battery to the starter/fuse box, being careful to avoid other wiring so as to reduce electromagnetic interference. The ground should be short and mounted directly to the chassis.
Batteries emit hydrogen gas as part of their electrolytic process. Recall the Hindenburg and that hydrogen is an extremely combustible gas. We want to avoid that. Without a proper, sealed battery box, relocating the battery inside the car can be a hazardous modification. Luckily, typical batteries that enthusiasts opt for are sealed units, meaning acid and gas can't escape. NRGCELL, Odyssey and Braille batteries are all sealed units providing worry-free performance without the box.
Proper mounting is just as important. Inadequacy here is a leading cause for tech inspection failures. When factory-mounting hardware won't work, look to Password:JDM for battery brackets. Such brackets are designed specifically for use with Odyssey PC680 and NRGCELL slim batteries, providing a direct bolt-in solution for the DA, EF, even the BB6 Prelude. Braille also offers specific battery brackets for its most popular models.
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The Hows And Whys Of Battery Relocation - Garage Tech
Shed Pounds While Improving Weight Distribution
By Mike Kojima
In setting up a car for handling it's preferable to attempt to attain a 50/50 weight distribution so that all of the wheels share the load of getting a car around a corner as equally as possible. For drag racing, one strives to get as much weight as possible over the drive wheels to help traction. A car's heaviest end is often the opposite of what is ideal, such as a front-engine rear-drive car or a front-wheel drive car.
To try to improve the weight distribution, race car builders have resorted to things like setting the engine back to get more weight where it can do good. This is fine for the serious racer but out of the question for the average enthusiast. But what if you found out about a mod where you could get the same change in weight distribution as setting the engine back 5-10 inches that took very little time and money to do? You'd probably jump all over this, right?
You can get all of the benefits of setting the engine back by simply relocating the battery from the front of the engine compartment to the trunk. This simple mod can change the weight distribution of a car from 1 to 2 percent. This is a big difference that can easily be felt by the driver in terms of less understeer and/ or better traction.
To show the remarkable effects of a simple battery relocation project, with the assistance of Steve Mitchell of M-Works we took a driftmodified AE86 Corolla and put it on corner scales with 200 pounds of weight to simulate a driver in the passenger seat. We moved the battery around the inside cabin to showcase the differences in weight distribution by simply altering the battery mounting position.
Corner scales are electronic scales used to set up the chassis of a race car with adjustable coilovers. The spring heights of each corner are adjusted to get a 50 percent crossweight percentage with the driver's weight in the seat. When the crossweight percentage is 50 percent the car will have an equal balance in left and right turns, regardless of the driver's offset weight in the car. The more balanced the better the weight distribution.
Here is how our experimental stock Hachiroku weighed at each corner.
Battery location: Stock left front of engine compartment
Driver side Front: 725
Driver side rear: 606
Passenger Front: 642
Passenger Rear: 552
Front-to-Rear Weight Percentage: 54/46
Crossweight Percentage: 49.4%
As you can see there is quite a bit of difference between the left and right weight of the car. The crossweight isn't bad considering that the car hasn't been corner balanced.
Now we moved the battery to the right side of the trunk.
Battery location: Right rear of trunk
Driver side Front: 668
Driver side rear: 638
Passenger Front: 646
Passenger Rear: 575
Front-to-Rear Weight Percentage: 52/48
Crossweight Percentage: 50.8%
Now you can see that the weight from the right side of the car to the left side is much more equal. Best of all, the front-to-rear weight percentage has improved by 2 percent, which puts the car pretty close to the ideal 50/50 weight distribution. This has the same effect as setting the engine back around 10 inches. A 2 percent difference in weight distribution is easy for a driver to feel.
Next, we moved the battery to the left side of the trunk to see what would happen.
Battery location: Left rear of trunk
Driver side Front: 686
Driver side rear: 646
Passenger Front: 627
Passenger Rear: 567
Front-to-Rear Weight Percentage: 52/48
Crossweight Percentage: 50.4%
Although the weight bias is more to the heavier left side of the car, it's still much better than stock. The crossweight percentage is even better but this can be deceiving, as it could easily be zeroed out with some slight adjustments of the coilovers. The right rear of the trunk is the best place for the battery.
Sometimes you can't fit the battery in the trunk or you want to keep the car's polar moment of inertia low for quicker transitional handling. To visualize polar moment of inertia, imagine trying to twist a set of dumbbells back and forth from the handle. Sort of tough, right? Now imagine trying to twist the same weight in your hand if it was a compact sphere. This is much easier. A car, with its mass located closer to its center, will respond to steering input faster. So if you want to reduce your polar moment of inertia more than improving your overall weight distribution, you'll want to place the battery within the car's wheelbase.
Let's see what happens when the battery is placed behind the passenger seat.
Battery location: Behind front passenger seat
Driver side Front: 687
Driver side rear: 622
Passenger Front: 651
Passenger Rear: 567
Front-to-Rear Weight Percentage: 53/47
Crossweight Percentage: 50.4%
The left-to-right wheel weights are considerably improved and the front-to-rear weight distribution is still improved by an impressive 1 percent-equivalent to about a 5-inch engine setback. Most drivers can feel a 1 percent change in weight distribution.
Placing the battery behind the driver seat resulted in these weights.
Battery location: Behind driver seat
Driver side Front: 703
Driver side rear: 625
Passenger Front: 631
Passenger Rear: 568
Front-to-Rear Weight Percentage: 53/47
Crossweight Percentage: 49.7%
This method wasn't as good but it's still definitely way better than in the stock position. Now you can see that relocating the battery is as good as most expensive fabrication procedures. What's stopping you from doing it?
How It's Done
Many companies make and sell battery relocation kits. You can simply purchase and use one of these. There is a caveat though. Many kits, even those offered by famous and reputable companies, use flimsy stamped steel or thick-formed wire battery mounts and brittle plastic boxes for their kits. In an accident, the heavy battery can easily deform or break these mounts and bust out of a fragile battery box becoming a 40- to 50-pound missile filled with acid hurtling around the inside of the car. This sort of thinking can kill you instantly if it hits you in the wrong spot. A loose battery can strike you with melon-crushing force. We've seen this happen several times in racing accidents.
For this reason, we recommend heavy-duty billet-type mounts and the use of gel cell-type batteries or full metal enclosures bolted to the solid parts of the chassis with grade five bolts and large fender washers if the battery is anywhere near the driver's compartment. This precaution also goes for trucks if there isn't a solid welded-in bulkhead between the trunk and the driver's compartment. Remember a battery can generate a sledgehammer-like blow of hundreds of pounds of force in a crash and you have to keep this in mind when you choose or build mounts.
Also, check the rules of whatever racing sanctioning body you might run under before starting a battery relocation project. The NHRA requires metal battery boxes vented to the outside of the car unless a dry cell-type battery is being used. The NHRA also requires an external accessible rear-mounted remote battery shutoff switch for trunk-mounted batteries. Most road racing associations require metal boxes unless the battery is a sealed dry cell type and has externally mounted cutoff switches marked with a triangular-standardized label.
Because of the hazard issues with normal lead-acid batteries-how they tend to emit flammable hydrogen gas and spew sulfuric acid-it's a good idea to go with a sealed racing dry cell battery. This also makes it easier to comply with a racing sanctioning body's rules for venting. Dry cell batteries have a dry paste instead of liquid sulfuric acid electrolyte, which is less likely to splash, spill around and burn you up like the blood of the beast in Alien. Dry cells don't emit Hindenburg burning hydrogen gas either. Hawker Energy, Braille and Odyssey make lightweight compact dry cell batteries and Optima makes full-size dry cell batteries. Most of these companies make sturdy billet or sheetmetal-type mounts suitable for proper mounting.
Lead-acid batteries are also very heavy. A typical stock battery for a four-cylinder compact weighs about 40 pounds and a battery that cranks over a large V-8 easily weighs about 50 pounds. A dry cell battery that can power your street car like an Odyssey 680 or a Braille B14115 weights only 11-15 pounds. Using one of these batteries is an easy way to instantly shave 30-40 pounds from your car as well as improve weight distribution. Smaller batteries like these aren't advisable if you're running a lot of lights, such as rally or night enduro racing or if you're into having large amounts of I.C.E. in your car. In this case the companies that sell dry cell racing batteries have units weighing about 20-25 pounds- half the weight of the stock batteries with superior power capability.
For cable, we recommend a copper conductor heavy-gauge wire since starter motors have the highest amperage draw of any electrical part in a car. We prefer welding cable as it has very low resistance. We use 0-gauge for truck-mounted batteries due to its low resistance. If you have a tough-to-spin, big high-compression V-8 motor, you might opt for the thicker even lower resistance 00- gauge wire. You can look at aircraft supply or marine supply houses for terminal ends and crimpers to terminate your cables properly. Dry cell battery makers also usually sell these items as accessories.
It is important to route the wire correctly. Remember that if the wire's insulation wears or chafes, you'll have a major short circuit and the potential for a really nasty electrical fire. In most cases we prefer to route the main power wire through the interior of the car so it's less likely to be damaged. It's important to secure the wire in many places using captive zip ties and/or rubber-lined adel clamps so that it can't rub and flop around. Also, use a circuit breaker like the type found in car audio, marine and aircraft supply stores or heavy-duty marine slow-blowing fuses to reduce the damage if something does cause the wire to short.
Relocating the battery is a good way to spend an afternoon that will give you a big gain in handling and can reduce overall weight for very little money.