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The Care & Feeding of Batteries
Capt. Mike Soehnlein
5/8/00 (7:21 AM)
There are so many rumors, stories, old tales & misconceptions about batteries, I thought I would try to consolidate the many resources I have into some semblance of order. First, there is no perfect, right answer for every battery condition & usage. This is a very general discussion. I’m not going to get into deep-cycle and gel-cell on this page.
First, an explanation of how a battery works. It doesn’t STORE electricity -- it makes it on demand. There are positive lead peroxide plates and negative spongy lead plates. An electrolyte (sulfuric acid) diluted with water attacks the metal lead peroxide plates, turning them into lead sulphate. Electrons flow – current. As it does so, the proportion of acid drops in the electrolyte, getting it closer to water (low SG), and the battery loses its ability to convert more into electric current. It’s “discharged.”
Reversing the current causes the lead sulphate to give up its sulphates back to the electrolyte, turning it from water back to acid and converting the plates back to lead peroxide and spongy lead, allowing the process to start over. It “recharges.” The specific gravity (SG) increases again and is thus the indicator of percent of charge. Full charge is 1.285, dead 1.120. This wasn’t meant to get that technical, but it’s important later to the care and use of batteries.
Let’s throw in two other misconceptions. There are no maintenance free batteries. There are sealed (vent recovery system, glued cap and enough electrolyte to not need adding over average life), and old-fashioned with caps. Cute multiple cap covers that require special tools or pry bars to open doesn’t make it maintenance free! They both need checking, testing and cycling.
One of the controversies around maintenance free batteries is charge rate. Most modern chargers have a higher amp rate for “maintenance free” based on the ability to charge faster without boil over due to vent & cap design. But true maintenance free sealed batteries have to charge at a LOWER rate due to limited venting and not wanting to lose excess electrolyte due to gassing. Use the low rate -- it will have less gassing & chance of boilover, thus is safer.
Lead-acid batteries do not have a memory, like NiCads, but should be discharged and recharged on a regular basis. Daily use is actually easier on them then any storage. Continuous trickle chargers may do more harm than good in the long run. If you use your Westy regular – weekly, there’s not much more you can do besides keep the terminals clean & tight, and check the electrolyte during your 3,000-mile oil changes. Top off only with distilled water; DO NOT OVERFILL. Different batteries have different fill marks, but if in doubt, fill to ¼” above the plates. Too full and you will have the dreaded “leaker” or boil-over during charging. No need to remind you what a leaking battery does to your battery box!
Different manufacturers recommend different storage techniques, but most have you remove the battery and recharge every so often. Porsche = 3-4 months; VW = 6-8 weeks; New Castle (biggest manufacturer of antique car batteries) = 2 months. Many also recommend you discharge the battery some before recharging, while others say ‘not necessary.’ Back up to the chemical reaction and you can see it doesn’t hurt, and probably helps. Continuous high state of charge (trickle chargers) may not allow the charge/discharge cycle to complete and the plates may build up lead sulphate too much to recover. They can warp or short out the plates. Only discharging batteries can complete that desired duty cycle. That’s not a problem with batteries in daily use.
Although everybody cautions against complete discharge, I’m going out on a limb and recommending you discharge the battery down to around 10 volts (5 on 6v systems) by running a MODERATE load such as the headlights. Then do a slow recharge at 4-6 amps, preferable with a charger that shuts off when fully charged. Repeat this every 4-6 weeks, checking electrolyte levels each time. Try to avoid fast charging if you let it get down too low. On 12v systems, the normal recharge is about 13.5 – 14.5v, 7 - 8v on 6v systems. Once recharged, remove the charger until next cycle. When a quicker recharge is necessary, start on low amperage to get the process started and electrolyte back to a more normal SG, then after 10-15 minutes, boost to the higher rate. Return to the slow or trickle charge as you approach full charge.
Other tricks to extend battery life include disconnect switches or removing them to controlled climates (avoid storing in extreme heat or cold). If storing out of the vehicle, store on wood or plastic strips. Do not allow moisture or dirt to collect on the case or terminals. Cap the plus terminal to avoid accidental shorts. There are acid-neutralizing pads available to set the battery on (in & out of the car), and I recommend both the felt treated terminal washers and the special non-conductive protective sprays for the terminals. Go to your auto parts store and get a good terminal cleaning brush and a pair of those inexpensive battery pliers that will spread the cable end clamps back open. Finally, use the right size wrench, but don’t over tighten. Battery carriers are the safe and smart way to carry a battery, whether the ice-tong style clamp or the straps that fit on the terminals. Keep a can of the battery spill neutralizing spray around in case of a spill.
There are truly automatic battery tenders that supposedly draw the battery down and then recharge. But that complexity means they won’t be cheap. Most, despite their advertising claims, are not much more than an automatic trickle charger that shuts of at full voltage and then restarts when voltage drops below a certain point. The ones I’ve seen, including my own, do so in such a tight range, they approach full-time charge and do not have enough drawdown to cycle the system at anything approaching the ideal daily use.
Auto or trickle charges are fine on systems that drain a battery quickly, such as those with high draw accessories that remain on with ignition off (clocks, alarms, modern car sensors & computers) AND will get normal use shortly. But for your Westy, sitting up over the winter, remove or at least disconnect and do the monthly draw down/recharge. You won’t hurt it and will probably help extend life. We’re all look for the easy way out, but these trickle chargers and auto-charge systems have a price. At the cost of today’s good batteries, especially the premium we often have to pay for the Westy’s off sizes, even an extra season should be worth the effort of doing the old-fashioned storage method. But it’s your money & takes your choice! (Editorial note: What a waste of automotive resources! Westies are great winter cars.)
A final word about battery testing: Get a SG tester; the cheap floating ball one at the discount store is fine. A battery load tester is more expensive -- $US 40-60bucks – but the only way to truly test a battery. By testing with a large load, you can observe draw-down and recovery. Even a dead battery can be charged up to read its surface charge of 12v with a voltmeter, but that doesn’t tell you its condition. Since you are usually dealing with a questionable battery or have it out of the car when test time rolls around, it’s a wise investment for your tool chest. Oh, and whenever you're working on a battery, charging or just checking electrolyte, Use Safety Goggles!!
More later!
Capt. Mike
6/21/05: Prices for a battery load tester describe above have dropped; I've seen them on sale at the discounters below $20. There is no excuse not to have one.
Capt. Mike Soehnlein
5/8/00 (7:21 AM)
There are so many rumors, stories, old tales & misconceptions about batteries, I thought I would try to consolidate the many resources I have into some semblance of order. First, there is no perfect, right answer for every battery condition & usage. This is a very general discussion. I’m not going to get into deep-cycle and gel-cell on this page.
First, an explanation of how a battery works. It doesn’t STORE electricity -- it makes it on demand. There are positive lead peroxide plates and negative spongy lead plates. An electrolyte (sulfuric acid) diluted with water attacks the metal lead peroxide plates, turning them into lead sulphate. Electrons flow – current. As it does so, the proportion of acid drops in the electrolyte, getting it closer to water (low SG), and the battery loses its ability to convert more into electric current. It’s “discharged.”
Reversing the current causes the lead sulphate to give up its sulphates back to the electrolyte, turning it from water back to acid and converting the plates back to lead peroxide and spongy lead, allowing the process to start over. It “recharges.” The specific gravity (SG) increases again and is thus the indicator of percent of charge. Full charge is 1.285, dead 1.120. This wasn’t meant to get that technical, but it’s important later to the care and use of batteries.
Let’s throw in two other misconceptions. There are no maintenance free batteries. There are sealed (vent recovery system, glued cap and enough electrolyte to not need adding over average life), and old-fashioned with caps. Cute multiple cap covers that require special tools or pry bars to open doesn’t make it maintenance free! They both need checking, testing and cycling.
One of the controversies around maintenance free batteries is charge rate. Most modern chargers have a higher amp rate for “maintenance free” based on the ability to charge faster without boil over due to vent & cap design. But true maintenance free sealed batteries have to charge at a LOWER rate due to limited venting and not wanting to lose excess electrolyte due to gassing. Use the low rate -- it will have less gassing & chance of boilover, thus is safer.
Lead-acid batteries do not have a memory, like NiCads, but should be discharged and recharged on a regular basis. Daily use is actually easier on them then any storage. Continuous trickle chargers may do more harm than good in the long run. If you use your Westy regular – weekly, there’s not much more you can do besides keep the terminals clean & tight, and check the electrolyte during your 3,000-mile oil changes. Top off only with distilled water; DO NOT OVERFILL. Different batteries have different fill marks, but if in doubt, fill to ¼” above the plates. Too full and you will have the dreaded “leaker” or boil-over during charging. No need to remind you what a leaking battery does to your battery box!
Different manufacturers recommend different storage techniques, but most have you remove the battery and recharge every so often. Porsche = 3-4 months; VW = 6-8 weeks; New Castle (biggest manufacturer of antique car batteries) = 2 months. Many also recommend you discharge the battery some before recharging, while others say ‘not necessary.’ Back up to the chemical reaction and you can see it doesn’t hurt, and probably helps. Continuous high state of charge (trickle chargers) may not allow the charge/discharge cycle to complete and the plates may build up lead sulphate too much to recover. They can warp or short out the plates. Only discharging batteries can complete that desired duty cycle. That’s not a problem with batteries in daily use.
Although everybody cautions against complete discharge, I’m going out on a limb and recommending you discharge the battery down to around 10 volts (5 on 6v systems) by running a MODERATE load such as the headlights. Then do a slow recharge at 4-6 amps, preferable with a charger that shuts off when fully charged. Repeat this every 4-6 weeks, checking electrolyte levels each time. Try to avoid fast charging if you let it get down too low. On 12v systems, the normal recharge is about 13.5 – 14.5v, 7 - 8v on 6v systems. Once recharged, remove the charger until next cycle. When a quicker recharge is necessary, start on low amperage to get the process started and electrolyte back to a more normal SG, then after 10-15 minutes, boost to the higher rate. Return to the slow or trickle charge as you approach full charge.
Other tricks to extend battery life include disconnect switches or removing them to controlled climates (avoid storing in extreme heat or cold). If storing out of the vehicle, store on wood or plastic strips. Do not allow moisture or dirt to collect on the case or terminals. Cap the plus terminal to avoid accidental shorts. There are acid-neutralizing pads available to set the battery on (in & out of the car), and I recommend both the felt treated terminal washers and the special non-conductive protective sprays for the terminals. Go to your auto parts store and get a good terminal cleaning brush and a pair of those inexpensive battery pliers that will spread the cable end clamps back open. Finally, use the right size wrench, but don’t over tighten. Battery carriers are the safe and smart way to carry a battery, whether the ice-tong style clamp or the straps that fit on the terminals. Keep a can of the battery spill neutralizing spray around in case of a spill.
There are truly automatic battery tenders that supposedly draw the battery down and then recharge. But that complexity means they won’t be cheap. Most, despite their advertising claims, are not much more than an automatic trickle charger that shuts of at full voltage and then restarts when voltage drops below a certain point. The ones I’ve seen, including my own, do so in such a tight range, they approach full-time charge and do not have enough drawdown to cycle the system at anything approaching the ideal daily use.
Auto or trickle charges are fine on systems that drain a battery quickly, such as those with high draw accessories that remain on with ignition off (clocks, alarms, modern car sensors & computers) AND will get normal use shortly. But for your Westy, sitting up over the winter, remove or at least disconnect and do the monthly draw down/recharge. You won’t hurt it and will probably help extend life. We’re all look for the easy way out, but these trickle chargers and auto-charge systems have a price. At the cost of today’s good batteries, especially the premium we often have to pay for the Westy’s off sizes, even an extra season should be worth the effort of doing the old-fashioned storage method. But it’s your money & takes your choice! (Editorial note: What a waste of automotive resources! Westies are great winter cars.)
A final word about battery testing: Get a SG tester; the cheap floating ball one at the discount store is fine. A battery load tester is more expensive -- $US 40-60bucks – but the only way to truly test a battery. By testing with a large load, you can observe draw-down and recovery. Even a dead battery can be charged up to read its surface charge of 12v with a voltmeter, but that doesn’t tell you its condition. Since you are usually dealing with a questionable battery or have it out of the car when test time rolls around, it’s a wise investment for your tool chest. Oh, and whenever you're working on a battery, charging or just checking electrolyte, Use Safety Goggles!!
More later!
Capt. Mike
6/21/05: Prices for a battery load tester describe above have dropped; I've seen them on sale at the discounters below $20. There is no excuse not to have one.
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