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Model Forum / Radio Controlled / Air Models / April 2004Charging a 12V gel cell
Just setting up my field box (newbie who scored some bargains) and was wondering what is the best way to charge the 12V gel cell? Not sure I'd want to try the old car charger but I don't want to buy some special trickle charger if it's nothing more than a standard 12V 300+ mA unit. Any ideas from the experts? While we're at it, any suggestions for charging duration and/or other life extending advice? How often do you top it up, or decide when to charge it?  SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. >what is the best way to charge the 12V gel cell? C/10 for 14 hours has always worked for mine. > How often do you top it up, or decide when to charge it? When the starter starts getting weak, I charge the battery. A standard hobby/garden 12v 7aH gel cell will hold a charge a long time, given our use. Dr.1 Driver "There's a Hun in the sun!" > >what is the best way to charge the 12V gel cell? > > C/10 for 14 hours has always worked for mine. Haven't been able to find much in the way of useful markings on mine. It's a SLA by Panasonic and quotes a number of voltage ranges but nothing on charging. > > How often do you top it up, or decide when to charge it? > > When the starter starts getting weak, I charge the battery. A pretty obvious and common sense answer I suspect. > A standard > hobby/garden 12v 7aH gel cell will hold a charge a long time, given our use. Is a 12V 700mA plug pack OK? It's what the local electronics store suggested, after dismissing their recommendation of a standard car charger........... (I'm not that stupid). SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. >Haven't been able to find much in the way of useful markings on mine. It should list a voltage and amperage. Of not, and it has a model number, check Panasonic online. Dr.1 Driver "There's a Hun in the sun!" > >Haven't been able to find much in the way of useful markings on mine. > > It should list a voltage and amperage. Of not, and it has a model number, > check Panasonic online. Will do. From memory, it's in the field box at the moment, it makes mention of 2.5Amps. Surely that can't be the charge rate. SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. > it makes mention of >2.5Amps. Surely that can't be the charge rate. Most probably not. It sounds like a small hobby-type battery. 2.5 a isn't going to power a starter through extended use. You might consider biting the bullet and buying a 12v, 7 aH gel cell. You might be happier in the long run. Dr.1 Driver "There's a Hun in the sun!" > > it makes mention of > >2.5Amps. Surely that can't be the charge rate. [quoted text clipped - 4 lines] > Dr.1 Driver > "There's a Hun in the sun!" After sealing it away in the field box I rechecked, which I should have done in the first place. SLA 12V 7Ah as it should be. Tried this 12V 750mA charger today, been over 12 hours and there is no hint of a warm battery (or anything disastorous). The panel battery check shows, if anything, a lesser charge than when I started (no idea what the gauge is attempting to show but I presume voltage). Tried to get a reading with my multi-meter (VOM) but it's a piece of rubbish and doesn't tell me anything beyond the voltage may be 12V. This reminds me to spend those Xmas gift vouchers on a new meter. Think I'll take this charger back and get the right one. Stupid store has the proper charger listed in the catalogue (for the same price) but the sales guy obviously didn't know that and probably knows less than I do about electronics. SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. >Stupid store has >the proper charger listed in the catalogue (for the same price) but the >sales guy obviously didn't know that and probably knows less than I do about >electronics. LOL! Sounds like our local electronics stores. A fully charged 12v battery should read around 13.5 on the meter. The charger has to put out more than that to properly charge the battery. For a 7aH battery, a 750 MaH charger sounds right. Dr.1 Driver "There's a Hun in the sun!" Check the charger!!! Some are AC output and need a bridge rectifier. -- Paul McIntosh http://www.rc-bearings.com > > > it makes mention of > > >2.5Amps. Surely that can't be the charge rate. [quoted text clipped - 30 lines] > ** President of the ozemail.* and uunet.* NG's > ** since August 15th 2000. How big is it? A 12V 7ah will be about 8" X 3" X 4". If it is 2.5a, then it will be considerably smaller than that. -- Paul McIntosh http://www.rc-bearings.com > > >Haven't been able to find much in the way of useful markings on mine. > > [quoted text clipped - 11 lines] > ** President of the ozemail.* and uunet.* NG's > ** since August 15th 2000. > How big is it? A 12V 7ah will be about 8" X 3" X 4". If it is 2.5a, then > it will be considerably smaller than that. Standard 12V 7Ah SLA. SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. > >what is the best way to charge the 12V gel cell? >> C/10 for 14 hours has always worked for mine. >Haven't been able to find much in the way of useful markings on mine. It's a >SLA by Panasonic and quotes a number of voltage ranges but nothing on >charging. > > How often do you top it up, or decide when to charge it? >> When the starter starts getting weak, I charge the battery. >A pretty obvious and common sense answer I suspect. >> A standard hobby/garden 12v 7aH gel cell will hold a charge a long >>time, given our use. > Is a 12V 700mA plug pack OK? It's what the local electronics store >suggested, after dismissing their recommendation of a standard car >charger........... (I'm not that stupid). This is exactly what Dr 1 Driver was referring to as a C10 charging device. 700 ma is 1/10th the capacity of the 7 Amp battery, Use it to charge overnight, or around 14 hours as noted. >Is a 12V 700mA plug pack OK? It's what the local electronics store >suggested, after dismissing their recommendation of a standard car >charger....... Hmmm, I have on hand wall charger that is rated 12V 500mA. Will this one be safe for charging 7A gell cell ? What happens once that full charge is reached ? GC will not accept charge anymore or it is neccessary to pull the plug after some 12-14 hours to prevent damage ? Indy --------------------------------------------- Power offline, EMP armed and ready http://www.flightmadness.com That will work great. What you can do is measure the charge rate after the battery is fully charged. Gell cells like to have a constant trickle charge on them or they go bad. Run the battery down until the starter has problems turning the engine over. Then charge it for about 5 hours and measure the current. Measure the current every hour after that until it reaches its lowest rate. That means the battery is fully charged. If the current is less than 100ma, you should be OK for quite a long standby. -- Paul McIntosh http://www.rc-bearings.com > >Is a 12V 700mA plug pack OK? It's what the local electronics store > >suggested, after dismissing their recommendation of a standard car [quoted text clipped - 12 lines] > Power offline, EMP armed and ready > http://www.flightmadness.com With ALL the variations mentioned here, would anyone be interested in reading the section on "The care and feeding of 12v Lead Acid Batteries" at the clinic? http://www.rcbatteryclinic.com/ Cheers -- \__________Lyman Slack_________/ \______AMA6430 IMAA1564___/ \____Flying Gators R/C______/ \__Gainesville FL _________/ Visit my Web Site at: http://www.LymanSlack.com > > Will this one be safe for charging 7A gell cell ? > > What happens once that full charge is reached ? > > GC will not accept charge anymore or it is neccessary to pull the plug > > after some 12-14 hours to prevent damage ? >Will this one be safe for charging 7A gell cell ? Yes. Just increase the charge time by 7/5. >What happens once that full charge is reached ? Help me out here, Red...as the voltages reach equalization, the charging amps drop. Right? You can't leave it on charge constantly, but a couple of hours overcharge shouldn't hurt it. Dr.1 Driver "There's a Hun in the sun!" Gell cells, like all other lead-acid batteries, like a trickle charge to stay topped up. They will go flat on their own and destroy themselves. Yuasa batteries have the charging currents and voltages listed on them for recharging and trickle (standby). -- Paul McIntosh http://www.rc-bearings.com > >Will this one be safe for charging 7A gell cell ? > [quoted text clipped - 7 lines] > Dr.1 Driver > "There's a Hun in the sun!" Guys, don't let those lil' wallwart chargers fool you... That 12V 500mAh charger is most likely pumping around 15.5-16 volts at around 500 mAH constantly... That's why the el cheapo wallwarts are referred to as "Constant Current chargers... without a regulator, they charge at their full amperage rate whenever they're on... And they can kill a good battery in short order... 500mA can "boil off" the electrolyte. The charger to use is a CONSTANT VOLTAGE charger, such as the old Ace "CVC"... This will charge at a preset voltage of say, 13.8VDC and the amperage tapers off as the surface voltage approaches 13.8V... My CVC maintains at 15mAh once the battery is charged... Cheers, Bill > >Will this one be safe for charging 7A gell cell ? > [quoted text clipped - 7 lines] > Dr.1 Driver > "There's a Hun in the sun!" Their open circuit voltage may be that high but under load it falls significantly. And, they also don't pump out 500ma continuously. The current output is dependent on the load. -- Paul McIntosh http://www.rc-bearings.com > Guys, don't let those lil' wallwart chargers fool you... > [quoted text clipped - 28 lines] > > Dr.1 Driver > > "There's a Hun in the sun!" > Their open circuit voltage may be that high but under load it falls > significantly. And, they also don't pump out 500ma continuously. The > current output is dependent on the load. > > -- Sure, it may drop to 14VDC and put 300mA into the battery, but in the end the correct answer is DON'T use one it will ruin the battery in the end. An unregulated wall wart is not a proper charger. Jim A fully charged battery being supplied with 14v will draw very little current. A battery is like a capacitor. As it charges, if the voltage remains the same, the current drops. No matter what the supply is capable of, Ohm's law still applies. These type wall warts are supplied for, and have been used for charging and sustaining gell cells for over 25 years that I am aware of. -- Paul McIntosh http://www.rc-bearings.com > > Their open circuit voltage may be that high but under load it falls > > significantly. And, they also don't pump out 500ma continuously. The [quoted text clipped - 7 lines] > > Jim > A fully charged battery being supplied with 14v will draw very little > current. A battery is like a capacitor. As it charges, if the voltage [quoted text clipped - 5 lines] > > -- Yep, and they have been drying them out for 25yrs too. Ohms law might have something to do with it were you shoving 100's of amps into the battery, after all that is going to be the only way that the internal resistance of the cells are going to offer any appreciable voltage drop due to ohms law. What is happening with a charger has more to do with the difference in potentials. You can shove more than 10mA into a 12VDC (nominal) battery by applying 14VDC to it. Jim I can see that your mind is made up on this. I guess I won't let my 10 year old gell cell read these posts because it may find out that it shouldn't have been charged like that and give up on me! ;^) -- Paul McIntosh http://www.rc-bearings.com > > A fully charged battery being supplied with 14v will draw very little > > current. A battery is like a capacitor. As it charges, if the voltage [quoted text clipped - 14 lines] > > Jim > I can see that your mind is made up on this. I guess I won't let my 10 year > old gell cell read these posts because it may find out that it shouldn't > have been charged like that and give up on me! ;^) It has nothing to do with an opinion or anything like that. Just in the last 6 months I have been the engineer on 4 products that have on board Lead Acid charge circuits. How many lead acid chargers have you designed? Do you actually know what occurs when an electrolyte cell is charged and discharged? The only real way to treat a "gel- cell" or lead acid battery is to apply the proper temperature compensated CC to CV charge. PERIOD. Anything has just been luck on your part not science. Jim > -- > Paul McIntosh [quoted text clipped - 19 lines] > > > > Jim I did some reading and gel cells like a constant voltage charge. I recently worked on an old Ace CVC charger that needed a new transformer. It charges at a constant 14.2 volts and 400 ma. As the battery becomes charged, the current drops to about 10ma. It can be left on indefinitely at that rate. John VB @flightmadness.com> wrote in message news:kbba80d5pd9jdb934p0lrjhh4umnclg57n@4ax.com... > >Is a 12V 700mA plug pack OK? It's what the local electronics store > >suggested, after dismissing their recommendation of a standard car [quoted text clipped - 12 lines] > Power offline, EMP armed and ready > http://www.flightmadness.com I charge mine with a 14.5v, 500mah wall wart transformer. Overnight charge after a weekend of flying is just about enough to keep it fully charged. -- Paul McIntosh http://www.rc-bearings.com > Just setting up my field box (newbie who scored some bargains) and was > wondering what is the best way to charge the 12V gel cell? Not sure I'd want [quoted text clipped - 11 lines] > ** President of the ozemail.* and uunet.* NG's > ** since August 15th 2000. Look for a "float" charger that's used for keeping batteries charged in lawn mowers, snowmobiles, and other things that are put away for a season. They can usually be found in the auto supply section of discount stores. I bought mine at Wal-Mart. Morris > Just setting up my field box (newbie who scored some bargains) and was > wondering what is the best way to charge the 12V gel cell? Not sure I'd want [quoted text clipped - 5 lines] > While we're at it, any suggestions for charging duration and/or other life > extending advice? How often do you top it up, or decide when to charge it? > Look for a "float" charger that's used for keeping batteries charged in lawn > mowers, snowmobiles, and other things that are put away for a season. I know the type you mean but they aren't common here in Australia as we don't tend to run that sort of equipment or see those climate changes. > They > can usually be found in the auto supply section of discount stores. I > bought mine at Wal-Mart. No Wal-Marts here but I'll hunt up the local Tandy equivalent. SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. > > Look for a "float" charger that's used for keeping batteries charged in > lawn > > mowers, snowmobiles, and other things that are put away for a season. > > I know the type you mean but they aren't common here in Australia as we > don't tend to run that sort of equipment or see those climate changes. Look at this: http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=42292 I used one of these for several years before I dropped it and it died. Morris Those are usually designed for RV batteries and other high capacity things. Their float charge may be higher than a small gell cell can tolerate. -- Paul McIntosh http://www.rc-bearings.com > > > Look for a "float" charger that's used for keeping batteries charged in > > lawn [quoted text clipped - 8 lines] > > Morris refer to = http://homepages.ihug.co.nz/~atong/ sub section = Battery care, Chargers & Power Supply. Chargers Hitec CG335 Pro 4 - 24 cell or multiple packs + Glowdriver. Hitec CG-340 1-16 cell NiCad & NiMh Robbe Power Peak Infinity 2 (Review) = Sunji 3000 ex Kr. Super Brain 969 Pro - MRC *** Gell Cell Battery Charger Lithium Ion Charger - DIY - SHDesigns - Chargers - How to recycle all those old plugins. 12 Volt SLA Charger - simple circuit PC Power Supply Conversion - Pat Harvey PC Power Supply - convert to power a 12VDC Battery Charger PC Power Supply Conversion (110/230 Vac to 12V ) Gell Cells require a Constant Voltage Charge (CVC) regulated at 13.6V a simple DIY is available at = http://web.archive.org/web/20030214221550/http://www.modelwarshipcombat.com/memb ers/rthibault/GellCell_Battery_Charger.htm or for best IMO CVC charger = http://www.acehobby.com/acehobby/products/electronics/chargers/superCVC/index.html regards Alan T. Alan's Hobby, Model & RC Web Links http://homepages.ihug.co.nz/~atong > Just setting up my field box (newbie who scored some bargains) and was > wondering what is the best way to charge the 12V gel cell? Not sure I'd want [quoted text clipped - 5 lines] > While we're at it, any suggestions for charging duration and/or other life > extending advice? How often do you top it up, or decide when to charge it? > refer to = http://homepages.ihug.co.nz/~atong/ > [quoted text clipped - 17 lines] > Gell Cells require a Constant Voltage Charge (CVC) regulated at 13.6V a > simple DIY is available at = http://web.archive.org/web/20030214221550/http://www.modelwarshipcombat.com/memb ers/rthibault/GellCell_Battery_Charger.htm > or for best IMO CVC charger = http://www.acehobby.com/acehobby/products/electronics/chargers/superCVC/index.html Thanks for the info, I had already run across most of that. Unfortunately, at my electronics skill level the amount of effort would hardly justify the result. It would probably work but look like a dangerous mess of solder. :-) SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. |
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