----- Original Message ----- From: "Garry Whitfield > I use a 17ah sealed lead acid battery for fast charging on-field. > How do I re-charge properly. Is there a battery charger for this type of > battery? At this stage I charge off an ordinary overnight car charger on > a low setting. Is there an peak detect system for this type of battery? > Help appreciated. > GARRY It sounds like what you are doing is about as good as it needs to be. Lead Acid batteries don't "peak" so a peak detecting charger won't work. The preffered method for charging LA batteries is with a constant "float" voltage instead of the constant current chargers we use for NiCd and NiMH batteries. This type of charger provides current as needed (up to its capacity or selected setting) to hold the voltage constant at about 2.3 volts per cell. As the battery charges its voltage increases. The closer it gets to the float voltage the lower the current until the current tapers off to a trickle. The car charger you are using may be doing this already. If you can rig a way to put an ammeter in series you should be able to verify this. The only likely problem could be that LA batteries don't like sustained fast charges. (So using a low setting of about 2A is good for your battery size.) Unfortunately car chargers may consider this a trickle relative to a 100AH car battery and may not drop any lower. You can check for this with an ammeter as described above or with a voltmeter. Watch the voltage as your battery charges. If it flattens out somewhere around 14v, you're fine, use it without concern. If it continues charge beyond this, you will have to keep an eye on the charge to terminate before it overcharges. Other alternatives: Hobby stores do sell 12v trickle chargers for this type of battery. I'm not a fan of this approach, however, as they provide no protection against overcharge so you may as well use your car charger. Another solution is to go to Radio Shack and get a cigarette lighter plug and a 1/2 ohm 10 watt resistor and solder up an adapter to plug your battery into the car. The resistor will keep the current from getting too high if you plug in the battery nearly dead and the car regulator will prevent overcharging. Note: do this while driving, your 17AH battery could drain your car battery if the car is stopped. Rick, RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
