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Grip Tools 38020 12V Automatic Battery Float Charger
Having trouble charging my 12v SLA battery. The green light comes on and then fades away quickly. Its not charging my battery at all. What gives?
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Date published: 2014-07-15
How to charge battery without removing from speaker box?
I want to make a portable speaker using a sealed lead acid battery and a tripath amp. I want to be able to charge the battery without having to open a latch to connect the alligator clips. Additionally, I don't want the wall socket cord hanging out the side of the boom box. How would I do this?
It sounds like a nice little project, Simon. The Tripath amp generates very little heat so you will probably be ok even with the amp in a sealed box (I'm inferring from your brief question & description that you're installing the amp in the speaker box). You indicate that you are an amateur so I'm going to assume that you have some basic soldering skills. The Grip tools Charger will work well for your application and since it's an analog design and does not use a switching power supply it should not generate any noise that would get into the amplifier. I have not looked at the charger output with a scope but in the unlikely event that it does generate any noise that causes you grief let us know and I'll show you how to quiet things down.I have drawn a schematic diagram showing you how to connect charger, battery, amplifier and a very basic protection circuit. All of the parts are available from PE and I've indicated the PE part numbers on the diagram. You'll want to cut off the charger alligator clips so you can solder a plug onto the wires. The DC charger jack can be installed wherever it works best for you.The fuse and zener diode are there to protect the Tripath amplifier should a problem with the charger or battery cause the battery terminal voltage to exceed 15 Volts. If this should happen, the zener will conduct and blow the fast acting fuse disconnecting both the battery and charger. Be aware that if this happens and after you correct the cause of the problem you will most likely need to replace the zener diode along with the blown fuse. If you use a 5 Watt 15 Volt Zener the larger Zener will probably survive the short circuit current surge. PE does not offer a 5 Watt Zener but these are readily available from companies like Digikey.The circuit will work fine without the Zener diode and fuse but it's worth the extra effort to save the amp in the event of a fault condition.Let us know how things turn out.
Date published: 2013-09-19
Is this charger safe for the following battery? 12v 4.5 ah? Or does the ah have to be at least 5? Thanks
You didn't mention the type of battery, such as sealed lead acid, gel cell, etc. No matter, this charger will work well for your 12.5 V battery. It doesn't matter what the amp hour rating is.If your battery is well discharged the green charge light will stay on for quite a while when you initially connect but will eventually go off. Then the red LED will stay on indicating the battery is fully charged and at the correct terminal voltage - ready for use. If you leave the charger connected all the time you will see the green charge LED go on and off periodically which indicates that the charger is maintaining a full charge automatically.There is no problem that I have found with leaving the charger connected all the time even during periods of connected equipment use. It will not damage the charger.It's a nice charger and very quiet from an RF point of view.
Date published: 2013-07-10
power supply for lepai 20 20.
I want to build a portable stereo using the lepai 20 20 amp that uses a 9 amp hour 12v sealed lead acid battery for power. I want to know if this charger is safe to use on a sealed battery and if it will work as a power supply for the amp when the battery is on charge. THANKS.
Yes, you can safely use this charger for your 12 V sealed lead acid battery. It's an excellent float charger for this type of battery.No, you can not use this charger as a power supply for the Lepai 20-20 amplifier. Just leave the charger connected to the battery all the time. The amplifier will draw from both the charger and the battery when the battery is discharged however under this condition you will not get the best sound quality from the amp. The float charger does not have the current capability to drive the Lepai directly. This amplifier does require a good solid 2 to 4 Amp 12 to 13.8 V regulated supply to deliver its rated power output.
Date published: 2013-06-29