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Frank Dinger wrote:
One thing to keep in mind is that battery voltage changes with temperature, and any float or trickle charger that doesn't take this into account can shorten a battery's life considerably. So if you want to get the longest life from your battery, you should make sure the charger is properly temperature compensated. ======================================= Roy , If the lead acid battery charging current is limited to 0.1C ,(example a 15Ah sealed battery is charged at max 13.8 V with a current not exceeding 1.5A) is temperature compensation then still a necessity to optimise the battery's (usable) life ? And if it is, in which temperature range ? I have not found this info through Web based tutorials. I am very interested in this topic since I charge a number of batteries (some non- sealed some sealed) by means of a (150 W max)wind generator and 2 pcs 64Wpeak solar panel. TIA for any advice Frank GM0CSZ / KN6WH I'm sorry, but I don't have an answer to your question. Actually, I'm not sure there is a simple answer. There are a number of quite different types of lead-acid battery, with different plate compositions, construction, and electrolyte form (e.g., liquid and "starved" -- as far as I can tell, gelled electrolyte is no longer used or is at least very rare, in spite of the fondness hams have for dubbing every sealed cell a "gel cell"). Each has its own characteristics, advantages, and shortcomings. I heartily recommend a careful reading of the manufacturer's recommendations for the particular battery you'll be using. In more general terms, I don't think any lead acid battery manufacturer recommends constant current charging at any level. Charging to maintain a cell at full charge (float charging) is, in my experience, invariably recommended to be constant voltage, not constant current, with the voltage being temprature compensated (lower voltage at higher temperature). The amount of current is then whatever the battery requires to maintain full charge. I did a quick google search of lead-acid battery float charging "temperature compensation" and came up with quite a few hits including some basic tutorials, a couple of which were http://www.powerstream.com/SLA.htm and http://www.emrg.ca/ideas&info/gel_cell/battery_care.htm. There are many more available. But again, batteries can differ quite a great deal, so you should really get information specific to the particular battery, or at the very least, to the general class of battery, that you'll be using. Roy Lewallen, W7EL |
On Tue, 24 Feb 2004 02:05:39 GMT, U wrote:
Solar panels and all that stuff is quite expensive, but old car batteries ("old" is when it doesn't get my Diesel started in subzero temps) are not. While a cold diesel is hard to start, the capacity of a car battery drops drastically at cold temperatures and assuming you are referring to temperatures below 0 F (not 0 C), the capacity of the "old" battery is well below nominal even in warm conditions. So even if you can get those cheaply, you may have to have two to get to the nominal capacity. The optimal float charging voltage may be different for different old batteries and this can be a problem when connecting multiple batteries in parallel. Batteries designed for car starter duty often expect some amount of vibration, which they do not get when in stationary use. Unless you get several batteries for free, it is not such a big bargain as it would look like. I don't know about the car battery final disposal costs, but if they are high, collecting a large number of reduced capacity old batteries might be quite expensive when they are finally disposed. Paul OH3LWR |
On Tue, 24 Feb 2004 02:05:39 GMT, U wrote:
Solar panels and all that stuff is quite expensive, but old car batteries ("old" is when it doesn't get my Diesel started in subzero temps) are not. While a cold diesel is hard to start, the capacity of a car battery drops drastically at cold temperatures and assuming you are referring to temperatures below 0 F (not 0 C), the capacity of the "old" battery is well below nominal even in warm conditions. So even if you can get those cheaply, you may have to have two to get to the nominal capacity. The optimal float charging voltage may be different for different old batteries and this can be a problem when connecting multiple batteries in parallel. Batteries designed for car starter duty often expect some amount of vibration, which they do not get when in stationary use. Unless you get several batteries for free, it is not such a big bargain as it would look like. I don't know about the car battery final disposal costs, but if they are high, collecting a large number of reduced capacity old batteries might be quite expensive when they are finally disposed. Paul OH3LWR |
the biggest brownout I experienced, I guess one could call that
already a black out, lastet 2 weeks and was unusual. These days they can last anywhere from 0.0001 minutes to 10 hours. The nice thing about the car battery approach is that if things take longer you can use the battery out of your car or truck, you could even drive around the block until a weak battery is recharged. ================================== Uwe , With a normal AC system and long duration outages you mentioned an appropriately sized UPS with external batteries would do the trick (depending on the power you need) For full domestic power requirements a 2-4 kWatt petrol or diesel engine ( portable) set would probably be the best. Many of these sets have both AC and nominal 12v DC (for charging batteries) Check the Honda range of petrol engine/generator sets ,often advertised and mentioned by RACES and ARES emergency communicators and by those involved in Amateur Radio Field Day operation. Frank GM0CSZ / KN6WH |
the biggest brownout I experienced, I guess one could call that
already a black out, lastet 2 weeks and was unusual. These days they can last anywhere from 0.0001 minutes to 10 hours. The nice thing about the car battery approach is that if things take longer you can use the battery out of your car or truck, you could even drive around the block until a weak battery is recharged. ================================== Uwe , With a normal AC system and long duration outages you mentioned an appropriately sized UPS with external batteries would do the trick (depending on the power you need) For full domestic power requirements a 2-4 kWatt petrol or diesel engine ( portable) set would probably be the best. Many of these sets have both AC and nominal 12v DC (for charging batteries) Check the Honda range of petrol engine/generator sets ,often advertised and mentioned by RACES and ARES emergency communicators and by those involved in Amateur Radio Field Day operation. Frank GM0CSZ / KN6WH |
In article , Paul Keinanen
writes: On Tue, 24 Feb 2004 02:05:39 GMT, U wrote: Solar panels and all that stuff is quite expensive, but old car batteries ("old" is when it doesn't get my Diesel started in subzero temps) are not. While a cold diesel is hard to start, the capacity of a car battery drops drastically at cold temperatures and assuming you are referring to temperatures below 0 F (not 0 C), the capacity of the "old" battery is well below nominal even in warm conditions. Yet they DO start. :-) I'm familiar with north country snow, ice, and freezing temperatures, learned to drive in such environments. Automobiles are OUTSIDE and have to take the entire change of temperatures. An emergency power backup system does NOT have to have its battery out in the cold...or hot. So even if you can get those cheaply, you may have to have two to get to the nominal capacity. The optimal float charging voltage may be different for different old batteries and this can be a problem when connecting multiple batteries in parallel. Not absolutely necessary. 12 Volt automobile batteries designed for LARGE vehicles have rather high ampere-hour ratings. Do NOT - absolutely - keep batteries in parallel without series diodes or other protections! One or more batteries in parallel can effectively "cook" one that is low in voltage. Batteries designed for car starter duty often expect some amount of vibration, which they do not get when in stationary use. Outside of bad design and poor quality control, the vehicle battery source of failure is almost always excessive vibration. When plate material is shaken off, it collects in the case bottom and can short out neighboring plates. Unless you get several batteries for free, it is not such a big bargain as it would look like. I don't know about the car battery final disposal costs, but if they are high, collecting a large number of reduced capacity old batteries might be quite expensive when they are finally disposed. At most auto parts stores in the USA, one can get a medium-size vehicle lead-acid battery for about $30 and trading in the old one. Prices vary slightly according to region and store. Factory-new batteries, such as Sears "Die-Hard" brand, are available for about twice that, no trade-in. Auto dealership-service centers will probably charge three times that (got stuck for that last year). There is a great variation in lead-acid vehicle battery cost over here so it is worth it to shop around. My eye doctors' office uses two 12 V lead-acid vehicle batteries for its servers (6 opthalmologists, 2 optometrists)...but only because they have an old UPS designed for 24 V battery back-up. Last year they moved that UPS and batteries to a concealed cabinet instead of being beside the receptionists' desk where all who could see saw it. Much better appearance. :-) By the way, a small 12 V lead-acid battery designed for motorcycles ought to be good for a heavy QRP rig. Len Anderson retired (from regular hours) electronic engineer person |
In article , Paul Keinanen
writes: On Tue, 24 Feb 2004 02:05:39 GMT, U wrote: Solar panels and all that stuff is quite expensive, but old car batteries ("old" is when it doesn't get my Diesel started in subzero temps) are not. While a cold diesel is hard to start, the capacity of a car battery drops drastically at cold temperatures and assuming you are referring to temperatures below 0 F (not 0 C), the capacity of the "old" battery is well below nominal even in warm conditions. Yet they DO start. :-) I'm familiar with north country snow, ice, and freezing temperatures, learned to drive in such environments. Automobiles are OUTSIDE and have to take the entire change of temperatures. An emergency power backup system does NOT have to have its battery out in the cold...or hot. So even if you can get those cheaply, you may have to have two to get to the nominal capacity. The optimal float charging voltage may be different for different old batteries and this can be a problem when connecting multiple batteries in parallel. Not absolutely necessary. 12 Volt automobile batteries designed for LARGE vehicles have rather high ampere-hour ratings. Do NOT - absolutely - keep batteries in parallel without series diodes or other protections! One or more batteries in parallel can effectively "cook" one that is low in voltage. Batteries designed for car starter duty often expect some amount of vibration, which they do not get when in stationary use. Outside of bad design and poor quality control, the vehicle battery source of failure is almost always excessive vibration. When plate material is shaken off, it collects in the case bottom and can short out neighboring plates. Unless you get several batteries for free, it is not such a big bargain as it would look like. I don't know about the car battery final disposal costs, but if they are high, collecting a large number of reduced capacity old batteries might be quite expensive when they are finally disposed. At most auto parts stores in the USA, one can get a medium-size vehicle lead-acid battery for about $30 and trading in the old one. Prices vary slightly according to region and store. Factory-new batteries, such as Sears "Die-Hard" brand, are available for about twice that, no trade-in. Auto dealership-service centers will probably charge three times that (got stuck for that last year). There is a great variation in lead-acid vehicle battery cost over here so it is worth it to shop around. My eye doctors' office uses two 12 V lead-acid vehicle batteries for its servers (6 opthalmologists, 2 optometrists)...but only because they have an old UPS designed for 24 V battery back-up. Last year they moved that UPS and batteries to a concealed cabinet instead of being beside the receptionists' desk where all who could see saw it. Much better appearance. :-) By the way, a small 12 V lead-acid battery designed for motorcycles ought to be good for a heavy QRP rig. Len Anderson retired (from regular hours) electronic engineer person |
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On Sat, 28 Feb 2004 18:26:26 GMT, Bruce in Alaska
wrote: In article , (Avery Fineman) wrote: While a cold diesel is hard to start Not if you understand the physics of the situation. Just take your XYL's Hair dryer out and blow hot air down the air intake. Your diesel will start on the first crank, first time , every time. The problem with diesels is the high compression ratio, so rotating the crank shaft is the hard part. Just monitor the signal lights in the dashboard when you try to start. Running the block heater for half an hour will help a lot, since the oil flows much more smoothly and the battery will deliver much more current (if in the engine compartment) due to the higher battery temperature. Paul OH3LWR |
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