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| Thread ID: 46337 | 2004-06-20 10:42:00 | sorta OT: SLA battery chargers | tweak'e (174) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 246310 | 2004-06-20 10:42:00 | i'm trying to find a sealed lead acid battery charger that can handle all sorts of size batteries (12volt, 7Ah-20Ah). nearest thing so far is this (www.tesa.co.nz) which is a variable 60 to 1300mA CHARGER. anyone know where i could buy one? (tho prefer a 300-2000mA charger) or who to mod a standard 2amp sla charger and add adjustable current limiting ?? |
tweak'e (174) | ||
| 246311 | 2004-06-20 11:47:00 | > > or who to mod a standard 2amp sla charger and add > adjustable current limiting ?? Well, if all else fails and you have to "roll your own" the LM 317 Application Note (www.national.com) may prove helpful. I've used them a few times and no complaints so far. R2 |
R2x1 (4628) | ||
| 246312 | 2004-06-20 23:36:00 | Additionally, there are some useful circuits on Bowdens Hobby Circuits (ourworld.compuserve.com) site, including a constant current charger circuit that I modified a bit to suit my needs. | Terry Porritt (14) | ||
| 246313 | 2004-06-21 04:55:00 | Basically, you need a constant voltage charger. I have had a lot of success with a regulated 13.8V 7A supply, adjusted up to 14.5V. Ideally, there should be current limit until the battery reaches about 13.8 V, (when the battery has about 80% charge) then a voltage limit at 14.5 for another couple of hours to get the rest. After that, a trickle charge at no more than 13.8 won't do any harm. Keeping the voltage at 14+ on a charged battery will boil out the electrolyte. A battery used on float should just have a trickle charger voltage limited at 13.8V. If you don't need fast charging, that would be fine too. Have a look at the appropriate sections of the Battery University (http://www.batteryuniversity.com/). Jaycar data/information section on their CD has an article about SLA charging. (It's probably on their web site too). |
Graham L (2) | ||
| 246314 | 2004-06-21 05:48:00 | What I have used for years, is a Dick Smith Kit K3127, fitted to an Arlec 4amp standard charger. Use it on a 32ampere/hour 12v for an electric golf trundler. Bye |
Peter H (220) | ||
| 246315 | 2004-06-21 06:28:00 | I built and use the same kit, which reduces the current to a maintenance trickle at a preset full charge voltage (typically around 14v) However it will deliver the full current until then (up to 4A, depending on the charger). This would be way too high for a 7AH SLA and would produce excessive gassing, risking rupture. I use it with a 15v plugpack for small SLAs, larger charger for the car. It would pay to research max charging currents for small SLAs to be safe and avoid damage. Cheers |
neddy (2192) | ||
| 246316 | 2004-06-21 06:38:00 | thx all :) i have a 4A automatic charger (switches to trickle when bat is full) for the car batteries but i was kinda hopeful to get/make one that is current adjustable so you can limit the charging current for all the different batteries. thus saving the need to have 4 different size chargers. the lm317 notes look interesting :) i will have a look at the DS battery charger circuts and see if it can be modded to suit. |
tweak'e (174) | ||
| 246317 | 2004-06-21 09:04:00 | Sounds like your charger has a similar circuit already (DS one is from Electronics Australia) - based on an SCR to switch the current on/off, pulsed by a 555 chip. Not true current limiting. Suppose a cheap/crude/inefficient (who cares) solution for current limiting would be to use monster resistors (calculate resistance and wattage ratings first) - just a thought. cheers |
neddy (2192) | ||
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