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Battery charger
I want to add a couple of deep discharge type batteries to my truck
for camping but how do I intermix them with the normal auto battery and charging system. I was thinking about getting a charger meant for charging batteries from solar panels and connecting the solar panel input to the generator. A 20A charger cost about $50USD .This would be very reasonable if I knew it would work as expected. Jimmie |
Battery charger
Why not use a traditional split charge relay.
Alternator output then becomes the limiting factor |
Battery charger
Hello Jimmie, I've used a relay to disconnect the auxilliary battery when either the ignition is off or the auxilliary battery voltage is low ~11.5V. There is a series diode and resistor in parallel with the relay contacts to bring the auxilliary battery back up slowly when the engine is running so the undervoltage lockout can reclose the relay and not dump the discharged battery on the alternator. The automotive "ice cube" relays are good for this I've seen some rated as high as 80A. Another refinement I did not try is a switch to override the undervoltage lockout so I could jump the vehicle off the auxillary battery. Perhaps the switch should be across the diode so the auxillary battery slowly charges the main battery? 73, Grumpy JIMMIE wrote in news:b5cabbfd-f220-4c7e-9cef- : I want to add a couple of deep discharge type batteries to my truck for camping but how do I intermix them with the normal auto battery and charging system. I was thinking about getting a charger meant for charging batteries from solar panels and connecting the solar panel input to the generator. A 20A charger cost about $50USD .This would be very reasonable if I knew it would work as expected. Jimmie |
Battery charger
Grumpy The Mule wrote in
: A correction... Another refinement I did not try is a switch to override the _ignition_ lockout so I could jump the vehicle off the auxillary battery. Perhaps the switch should be across the diode so the auxillary battery slowly charges the main battery? |
Battery charger
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Battery charger
On Nov 16, 4:42*pm, wrote:
Why not use a traditional split charge relay. Alternator *output then becomes the limiting factor I didnt think you could charge a deep cycle battery in an automotive system without damaging the battery. Its my understanding that car batteries are designed for a quick charge at realativly high current while deep cycle batteries require a long low current charge. To make it work thought you had to have a special charge regulator for the deep cycle battery. Jimmie |
Battery charger
Howdy,
What type of deep discharge battery do you mean? Gell vs AGM vs VRLA vs Flooded battery generally require different care. I use low maintenance flooded deep disharge batteries and charge them at 20% of their AHr capacity rating. I'd have no worries about mounting one of these remotely from the alternator (like in the trunk) and letting the vehicle system charge it. Gell or AGM I'd charge at 10% capacity or less. These would require some current limiting circuit. The volts per cell for full charge and float charge will be different too. Though if you keep the battery between 80% and 20% of full charge it's not an issue. 73, Grumpy JIMMIE wrote in news:8795bf5a-715c-4a24-8290- : On Nov 16, 4:42*pm, wrote: Why not use a traditional split charge relay. Alternator *output then becomes the limiting factor I didnt think you could charge a deep cycle battery in an automotive system without damaging the battery. Its my understanding that car batteries are designed for a quick charge at realativly high current while deep cycle batteries require a long low current charge. To make it work thought you had to have a special charge regulator for the deep cycle battery. Jimmie |
Battery charger
"JIMMIE" wrote in message ... I want to add a couple of deep discharge type batteries to my truck for camping but how do I intermix them with the normal auto battery and charging system. I was thinking about getting a charger meant for charging batteries from solar panels and connecting the solar panel input to the generator. A 20A charger cost about $50USD .This would be very reasonable if I knew it would work as expected. Jimmie If the RV isn't being used all the time the Battery chemistry is less of an issue. Deep cycles should be charged at roughly no more than 10 amps. and floated at 13.2 v. But if it is being cycled, the float value is less of an issue. You will need the long trip to insure it is up for the next stop. If you are mounting the second battery under the hood, close to the charger, then it is best to use NR 10 or 12 wire for the charge line to limit the current and be able to disable the RV relay rather than leave it charging every day on long commutes. You will need to check the water more often. I didn't see my earlier post, again DON'T use a solar charge controller as most regulate by shorting down the solar panel. If the system voltage is normal, nothing happens. If it should go high for any reason then it would simply burn out things. |
Battery charger
On Nov 17, 1:58*pm, Grumpy The Mule wrote:
Howdy, What type of deep discharge battery do you mean? Gell vs AGM vs VRLA vs Flooded battery generally require different care. * I use low maintenance flooded deep disharge batteries and charge them at 20% of their AHr capacity rating. I'd have no worries about mounting one of these remotely from the alternator (like in the trunk) and letting the vehicle system charge it. Gell or AGM I'd charge at 10% capacity or less. *These would require some current limiting circuit. The volts per cell for full charge and float charge will be different too. *Though if you keep the battery between 80% and 20% of full charge it's not an issue. 73, Grumpy JIMMIE wrote in news:8795bf5a-715c-4a24-8290- : On Nov 16, 4:42*pm, wrote: Why not use a traditional split charge relay. Alternator *output then becomes the limiting factor I didnt think you could charge a deep cycle battery in an automotive system without damaging the battery. Its my understanding that car batteries are designed for a quick charge at realativly high current while deep cycle batteries require a long low current charge. To make it work thought you had to have a special charge regulator for the deep cycle battery. Jimmie- Hide quoted text - - Show quoted text - Im not sure but they are sealed 100Ahr batteries and the max recharge rate is 10amps so definitly not FLOOD. I have recharged them from my aux power connector in my truck bed but this took a lot more care and effort than I wanted to give. Wife and kid thought I was paying more attention to the batteries than them.. I thought about feeding them from a constant current source. In this case it would act more like a current limiter. Jimmie |
Battery charger
Howdy,
Ok, the minimum you'd need to charge these is a voltage and current regulated supply limited to less than 10A and 13.62 for AGM or 13.50 for gell (check the manufacturer's stated the float voltage). No more than 14.1V in any case. The vehicle voltage is not much higer than this with the engine is running. It's possible to build a low drop linear regulator to serve this function. Linear Technology or Micrel should have an app note you can work from. This is the one device solution. You'll get a couple of hundred milliamps to an amp at 13.6V from as low as 14V maybe a bit less. Good for keeping the auxilliary battery topped off but not so good for recharging. If you want faster recharge (which still won't be very fast since 120%-140% of 100Ahr is is going to take 12H-14Hr at 10A) I suggest a SMPS running off the vehicle battery it can charge the gell cell even when the engine isn't running. Try National Semiconductor's Web Bench power design tool and roll your own with their parts. http://www.national.com/appinfo/power/webench.html For minimum recharge time a bigger SMPS (maybe a nice push-pull) is required. I might try a simple switcher boost converter or switched capacitor converter and raise the vehicle supplied voltage to about 24V at a few milliamps to bias a series pass MOSFET linear regulator. The output current and drop-out voltage are then only limited by the mosfet pass device(s) .... virtually unlimited! Though not as efficient as the switcher. Maybe a good idea to throttle back the current limit from 10A when the engine is running to a few hundred milliamps when it is not. Though even that's too much if the vehicle sits unused for too long. Which causes me to ponder... you'll drain the vehicle battery unless the engine is running. Even at 10A charge current a full recharge requires a fair amout of driving! Perhaps it's better to plan on recharging the battery from "dock side" power and only trickle charge the battery from the vehicle to keep it topped off. One of the low drop regulator IC's set to 13.6V or a simple switcher(tm) would be all you need for that. 73, Grumpy JIMMIE wrote in news:0309608e-8c61-4bac-a667- : Im not sure but they are sealed 100Ahr batteries and the max recharge rate is 10amps so definitly not FLOOD. I have recharged them from my aux power connector in my truck bed but this took a lot more care and effort than I wanted to give. Wife and kid thought I was paying more attention to the batteries than them.. I thought about feeding them from a constant current source. In this case it would act more like a current limiter. Jimmie |
Battery charger
On Nov 16, 4:21*pm, JIMMIE wrote:
I want to add a couple of deep discharge type batteries to my truck for camping but how do I intermix them with the normal auto battery and charging system. I was thinking about getting a charger meant for charging batteries from solar panels and connecting the solar panel input to the generator. A 20A charger cost about $50USD .This would be very reasonable if I knew it would work as expected. Jimmie Hey jimmie: TI makes a really sweet ic for charging batteries the UC3906. Is the greatest IC since sliced bread for charging batteries. It took forever to charge my deep cycle marine battery like a110AHr. A straight charger it would take a week to charge 100% it's that last 15% that's the toughest. The UC3906 charged my deep cycle marine battery to full charge from dead in 10 hours. It's one of the greatest homebrew jobs I've done. I used it to charge a 110AHr deep cycle marine battery for my electric bike. I could ride 2 days on a single charge like $0.25 worth of electricty back and forth to work. 45 miles on a single charge. 73 OM n8zu |
Battery charger
On Nov 17, 7:41*pm, Grumpy The Mule wrote:
Agreed! *I designed a DC UPS power supply for Harris using the UC3906 to charge a 4Ahr gell cell for wireless pbx. *The only down side is it requires some head voltage for the regulator, so it won't work well off a 12V vehicle system unless the engine is running and then not so great. I still have two of those Harris power supplies one runs an HT monitoring a repeater and the other runs a scanner and a small transmitter. *The batteries are ten years old and show little loss of capacity. raypsi wrote in news:355e6bae-ab52-4d0e-8fde- : TI makes a really sweet ic for charging batteries the UC3906. Is the greatest IC since sliced bread for charging batteries. It took forever to charge my deep cycle marine battery like a110AHr. A straight charger it would take a week to charge 100% it's that last 15% that's the toughest. The UC3906 charged my deep cycle marine battery to full charge from dead in 10 hours. It's one of the greatest homebrew jobs I've done. I used it to charge a 110AHr deep cycle marine battery for my electric bike. I could ride 2 days on a single charge like $0.25 worth of electricty back and forth to work. 45 miles on a single charge. 73 OM n8zu- Hide quoted text - - Show quoted text - I think I am going to try charging it through a 10 amp constant current source. If it works the way I am thinking as the battery nears full charge the pass transistor should saturate applying nearly full generator voltage across the battery topping off the battery. Im thinking(hoping) that when this occours the voltage drop across the transistor may be just enough to yield nearly the ideal float voltage for the batteries. The batteries normally power my heater and lights for my popup camper and a couple of radios that are mostly used for rx. With only an initial charge from the battey charger before leaving home I can camp about 4 days. With some additioal charging I am hoping to extend it another 2 oor 3 days. Since our trips usually include a few hours a day of driving I thought I would use this oppurtunity to top off the batteries. I have leaned against the idea of just running the engine for that purpose. The incandescent bulbs I am using in the camper are the main draw on the batteries perhaps going to LEDs would help. |
Battery charger
Howdy,
The saturation voltage will probably be less than a volt, likely only a few tenths of a volt. When the vehicle is running the output voltage could be too high. A transistor that comfortably handles the ten amps is going to be something like a 2N2955 or 2N3055 there are curves on the data sheets that tell the story. As the current souce runs out of compliance and the current drops, the output voltage rises because the saturation voltage decreases. There is an easy fix if you use a PNP pass transistor. Clamp the base at 13.6V plus a base emitter drop, say 0.8V, the output can't rise higher than the float voltage. Better yet, use a TL431 to sense the battery voltage to end the constant current charge by reducing the bias and enter float mode. (The TL431 is a very handy device and cheap. Check the app notes and I'm sure you'll find many other uses for it.) Then either NPN or PNP will work, choose your poison. I modified a junky old eight amp Kmart charger like this with a PNP device for charging the six volt battery in my tractor. You'll need some sort of short circuit protection. During a short the ten amps times the supply voltage will be dissipated in the pass device. Could be a fuse or breaker or active protection. I left this out of my first attempt and the pass device didn't like being shorted for even a moment. Luckily I tested this before putting it all back together rather than finding out later on in a snow storm. The existing thermal breaker was much too slow. LEDs would be a huge improvement. 73, Grumpy JIMMIE wrote in news:1fa6ec49-6eab-4cb6-8eeb- : I think I am going to try charging it through a 10 amp constant current source. If it works the way I am thinking as the battery nears full charge the pass transistor should saturate applying nearly full generator voltage across the battery topping off the battery. Im thinking(hoping) that when this occours the voltage drop across the transistor may be just enough to yield nearly the ideal float voltage for the batteries. The batteries normally power my heater and lights for my popup camper and a couple of radios that are mostly used for rx. With only an initial charge from the battey charger before leaving home I can camp about 4 days. With some additioal charging I am hoping to extend it another 2 oor 3 days. Since our trips usually include a few hours a day of driving I thought I would use this oppurtunity to top off the batteries. I have leaned against the idea of just running the engine for that purpose. The incandescent bulbs I am using in the camper are the main draw on the batteries perhaps going to LEDs would help. |
Battery charger
On Nov 18, 2:46*am, Grumpy The Mule wrote:
Howdy, The saturation voltage will probably be less than a volt, likely only a few tenths of a volt. *When the vehicle is running the output voltage could be too high. *A transistor that comfortably handles the ten amps is going to be something like a 2N2955 or 2N3055 there are curves on the data sheets that tell the story. As the current souce runs out of compliance and the current drops, the output voltage rises because the saturation voltage decreases. There is an easy fix if you use a PNP pass transistor. *Clamp the base at 13.6V plus a base emitter drop, say 0.8V, the output can't rise higher than the float voltage. Better yet, use a TL431 to sense the battery voltage to end the constant current charge by reducing the bias and enter float mode. (The TL431 is a very handy device and cheap. *Check the app notes and I'm sure you'll find many other uses for it.) *Then either NPN or PNP will work, choose your poison. I modified a junky old eight amp Kmart charger like this with a PNP device for charging the six volt battery in my tractor. You'll need some sort of short circuit protection. *During a short the ten amps times the supply voltage will be dissipated in the pass device. *Could be a fuse or breaker or active protection. *I left this out of my first attempt and the pass device didn't like being shorted for even a moment. *Luckily I tested this before putting it all back together rather than finding out later on in a snow storm. The existing thermal breaker was much too slow. LEDs would be a huge improvement. 73, Grumpy JIMMIE wrote in news:1fa6ec49-6eab-4cb6-8eeb- : I think I am going to try charging it through a 10 amp constant current source. If it works the way I am thinking as the battery nears full charge the pass transistor should saturate applying nearly full generator voltage across the battery topping off the battery. Im thinking(hoping) that when this occours the voltage drop across the transistor may be just enough to yield nearly the ideal float voltage for the batteries. The batteries normally power my heater and lights for my popup camper and a couple of radios that are mostly *used for rx. With only an initial charge from the battey charger before leaving home I can camp about 4 days. With some additioal charging I am hoping to extend it another 2 oor 3 days. Since our trips usually include a few hours a day of driving I thought I would use this oppurtunity to top off the batteries. I have leaned against the idea of just running the engine for that purpose. The incandescent bulbs I am using in the camper are the main draw on the batteries perhaps going to LEDs would help.- Hide quoted text - - Show quoted text - Saturation voltage my oh my. A simple DC to DC convertor on the gate of a FET of like 4 milli ohm so no more Vsat. I've done it with the UC3906 which is designed to charge lead acid. All you need is a source that'll will handle all that current. All the tricks I've seen done with lead acid charging constant current will fawk up ur battery unless you know when to shut it off like the UC3906 does. Maybe 3 TL431's as sensors and you can do it. But the UC3906 can sense a shorted cell and will not charge the battery if there is a shorted cell. 73 OM n8zu |
Battery charger
Howdy,
Geez... I read this and it confused me. I haven't been sleeping much and shouldn't post late at night. The easy fix is to use an emitter follower circuit where the the constant current load is connected to the emitter. If you put the regulator in the Positive side lead use an NPN. In my instance the current regulator's pass transistor is in the negative lead so the heatsink is at the same potential as the vehicle chassis. No insulating hardware is required. 73, Grumpy Grumpy The Mule wrote in : There is an easy fix if you use a PNP pass transistor. Clamp the base at 13.6V plus a base emitter drop, say 0.8V, the output can't rise higher than the float voltage. |
Battery charger
On Mon, 17 Nov 2008 09:06:28 -0800 (PST), JIMMIE wrote:
I didnt think you could charge a deep cycle battery in an automotive system without damaging the battery. Hmmm mine is 7yrs old |
Battery charger
Howdy I didn't describe this fully. Dissipation protection... Put the diode of an optocoupler with a resistor in series across the pass device's emitter and collector. Then connect the opto's transistor to the reference feeding the base of the pass device. Adjust the resistor in series with the LED so that when there's too much voltage across the pass device the led lights and decreases the reference voltage which reduces the current in the pass device. Another way to do this requires a zener, two transistors and three resistors. Optos are cheap enough and it's less parts to wire up. I fused the output in case something breaks, to keep the circuit from being slagged. In a short the thermal breaker on the transformer took about 45 seconds to trip. I've no idea what the fault current was but the needle of the lazy ten amp full scale meter that's built into the charger was slammed forcefully against the stop. 73, Grumpy Grumpy The Mule wrote in : You'll need some sort of short circuit protection. During a short the ten amps times the supply voltage will be dissipated in the pass device. Could be a fuse or breaker or active protection. I left this out of my first attempt and the pass device didn't like being shorted for even a moment. Luckily I tested this before putting it all back together rather than finding out later on in a snow storm. The existing thermal breaker was much too slow. |
Battery charger
JIMMIE wrote:
On Nov 16, 4:42 pm, wrote: Why not use a traditional split charge relay. Alternator output then becomes the limiting factor I didnt think you could charge a deep cycle battery in an automotive system without damaging the battery. Its my understanding that car batteries are designed for a quick charge at realativly high current while deep cycle batteries require a long low current charge. To make it work thought you had to have a special charge regulator for the deep cycle battery. ========================== 'Deep Cycle' batteries should be charged with a current not exceeding 0.1C , meaning that a 80Ah battery should be charged with a current not exceeding 8 Amperes. Frank KN6WH |
Battery charger
The UC3906 is temp compensated unlike zeners which go up with temp
rise and down with temp decrease. Believe me 1/10 of a volt change will fawk up the charge rate. Been there done that. I've quick charged deep cycle marine batteries at work when I forgot to put my battery on charge on my electric bike. 55 amp in one hour no problem. Now I was using this my electric bike every day to gits to work. I got 2 years out of that deep cycle marine battery before my brushes on my motor were no longer available from Grainger. I didn't count the times I quick charged the battery at 55 amp rate but it was quite a few. If this isn't any everyday thing make it simple, no frilles But a automotive in car charging system is the worst thing anybody to do to a battery. I'd let my battery sit on cold concrete before I'd charge it with an automotive charging system in a car. 73 OM n8zu I didnt think you could charge a deep cycle battery in an automotive system without damaging the battery. Its my understanding that car batteries are designed for a quick charge at realativly high current while deep cycle batteries require a long low current charge. To make it work thought you had to have a special charge regulator for the deep cycle battery. ========================== 'Deep Cycle' batteries should be charged with a current not exceeding 0.1C , *meaning that a 80Ah battery should be charged with a current not exceeding 8 Amperes. Frank * KN6WH |
Battery charger
Howdy,
There are a of couple newer devices that you might like even more than the UC3906. Check out the UC3909 and BQ2031. All zeners are not created equal! The 1N825 is a common temperature compensated diode and it's uncommonly good. Transfer standards built in the 1960's and 70's often used zeners... and they were good enough by golly. The venerated Fluke 335D used an ion implanted or burried zener diode and it's still one of the most stable units available. Here's the deal, the battery voltage varies with temperature. About minus 3 to minus 5 milivolts per degree C. Not very stable! (However for temperatures between 5C to 35C it can be safely ignored.) Now if the circuit is exposed to the same ambient temperature as the battery and your reference drifts about the same amount and in the same direction as the battery, it can be only a good thing. A true zener has a negative temperature coefficient. An avalanche diode has a positive temperature coefficient. The cross over point between the two effects is around 5.6V A common silicon rectifier diode has a negative 2 milivolts per degree C coefficient. It's not difficult to select a couple of parts that when combined in series will produce the minus 5 milivolts per degree C desired. A 6.8V zener in series with three 1N4001 running 1 milliamp of bias current is in the ball park. Honest to god temperature compensated charging requires a temperature sensor in the battery (thermistor usually) but it's only needed where you're charging at a rate that heats the battery or when charging over a very wide range of ambient. The above is just my opinion and all that jazz... 73, Grumpy |
Battery charger
On Nov 19, 1:09*pm, Grumpy The Mule wrote:
Howdy, There are a of couple newer devices that you might like even more than the UC3906. *Check out the UC3909 and BQ2031. All zeners are not created equal! *The 1N825 is a common temperature compensated diode and it's uncommonly good. Transfer standards built in the 1960's and 70's often used zeners... and they were good enough by golly. *The venerated Fluke 335D used an ion implanted or burried zener diode and it's still one of the most stable units available. Here's the deal, the battery voltage varies with temperature. About minus 3 to minus 5 milivolts per degree C. *Not very stable! *(However for temperatures between 5C to 35C it can be safely ignored.) * Now if the circuit is exposed to the same ambient temperature as the battery and your reference drifts about the same amount and in the same direction as the battery, it can be only a good thing. A true zener *has a negative temperature coefficient. An avalanche diode has a positive temperature coefficient. * The cross over point between the two effects is around 5.6V A common silicon rectifier diode has a negative 2 milivolts per degree C coefficient. It's not difficult to select a couple of parts that when combined in series will produce the minus 5 milivolts per degree C desired. *A 6.8V zener in series with three 1N4001 running 1 milliamp of bias current is in the ball park. Honest to god temperature compensated charging requires a temperature sensor in the battery (thermistor usually) but it's only needed where you're charging at a rate that heats the battery or when charging over a very wide range of ambient. The above is just my opinion and all that jazz... 73, Grumpy I hacked together a 10amp contant current source, actually it tuned out to be a little les than 9 amps and hooked it up between one of my 100ahr batteries and my shop type battery charger. So far it behaves as expected. I just hope it does the job as expected. Jimmie |
Battery charger
On Nov 19, 1:09*pm, Grumpy The Mule wrote:
Howdy, There are a of couple newer devices that you might like even more than the UC3906. *Check out the UC3909 and BQ2031. 73, Grumpy Yes indeed the 3909 is a switch mode version of the 3906 and the BQ2031 is a pulsed version. The 3906 uses a constant current source and I used 10 amp and mine turned out to be like 9 amps in real life, I forgot how many feet of 14AWG wire I used for the 10 map sense. Some say pulsed or pwm is the way to go. Maximizing the PWM to fast charge a battery would be advantageous. I think that's what they are using in the hybrid cars. 73 OM n8zu |
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