Hello all,

I am building a portable battery powered boom box. The boom box will be a pair of bookshelf speakers with a small amplifier and battery between them. I am using the lepai 2020A+ as the amplifier and a 7AH sealed lead acid battery. The original power supply for the amplifier is rated at 2 amps. Since the box will be battery powered I will need a 12v battery charger. I was thinking about getting a 3 step battery charger, something like the Schumacher SP3. https://www.amazon.com/Schumacher-SP3-Automatic-Extender-Maintainer/dp/B00752TRP0 In addition to being able to play from battery power I need the box to be able to run while being plugged in on 120V AC. So I would connect the charger to the battery which is then connected to the amplifier. This will undoubted work. My question is does anyone know if this will cause any issues with the battery charger since its a 3 step type charger? I read that one of the steps to charging a 12v battery involves constant current. Will this cause the battery charger to go crazy when the amplifier is drawing a variable amounts of current? I have tried to research the topic but was unable to find a definitive answer with respect to lead acid batteries and 3 step chargers.

Thank you for the help

 

Ask the manufacturer. Apparently they are very good at answering such questions.
https://www.amazon.com/forum/-/TxAMN02NAYPSM0/ref=ask_ql_ql_al_hza?asin=B00752TRP0

 

Any smart charger needs to monitor the Battery Current for proper functioning. This means that you cannot have any Direct load across the battery.
A charger cum supply will have a separate terminal for connecting the Load and Battery with the Battery current being monitored independently.

 

Be sure that charger will work with a small 7Ah SLA battery. I use this one:

https://www.amazon.com/gp/product/B0051D3MP6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

and it works great with wet cell batteries (small motorcycle battery, and larger boat deep cycle battery), but it will not fully charge a SLA (sealed lead acid) such as the small 7Ah battery you're talking about. It thinks the battery is full before it's actually full. Be sure whatever charger you choose will work properly with SLA batteries.