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Battery over discharge protection & charging module for 12 volt SLA battery

ElectricalGuy

Oct 31, 2022
3
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Oct 31, 2022
Messages
3
Hi, I am rather new to power electronics, and have been working on a portable radio/bluetooth speaker that requires 12 volts to run. I have found a 12v Sealed Lead Acid battery that I believe will work but am unsure of what module I need to properly charge and discharge it. I wish to be able to charge it from a DC dynamo hand crank made from a dc motor I have. Do you know if this is possible and if so what board/boards I need to do this? Thanks.
 

danadak

Feb 19, 2021
187
Joined
Feb 19, 2021
Messages
187
Yes this is doable.

You might look into charging systems for e-bikes. They surely
solved this as a problem.


The boards for charging not really an issue, lots of offerings.

Its the power generation and possible transient protection for the
boards that should be carefully addressed.


Regards, Dana.
 

ChosunOne

Jun 20, 2010
462
Joined
Jun 20, 2010
Messages
462
How big is the 12VDC SLA battery you found, that you want to charge? What is the power (or Amperage) draw when in use?

Ebikes tend to run at much higher voltages (Typically anything from 24V to 72V?), so you wouldn't be able to use one of those out of the box.

I have several scrap PCBs that provide slow charging for SLA batteries from 4Ah to ~15Ah (or anything smaller), and provide a steady 500-600 mA output without draining the battery; if that's any use to you. They're scrap because they've lost some other critical function, but their power supply still works and will still keep an SLA charged and ready. They do require a 16.5VAC 40VA transformer (wall wart) to work in an outlet; assuming you're in North America.
But if you're set on making your own board, or want something that you can hand-crank out in the wilderness, wait for others to weigh in. This is a pretty simple problem.

EDIT: I should mention that my scrap PCBs shut down output when the battery falls below 11.5VDC, preventing deep discharge.
 
Last edited:

ElectricalGuy

Oct 31, 2022
3
Joined
Oct 31, 2022
Messages
3
How big is the 12VDC SLA battery you found, that you want to charge? What is the power (or Amperage) draw when in use?

Ebikes tend to run at much higher voltages (Typically anything from 24V to 72V?), so you wouldn't be able to use one of those out of the box.

I have several scrap PCBs that provide slow charging for SLA batteries from 4Ah to ~15Ah (or anything smaller), and provide a steady 500-600 mA output without draining the battery; if that's any use to you. They're scrap because they've lost some other critical function, but their power supply still works and will still keep an SLA charged and ready. They do require a 16.5VAC 40VA transformer (wall wart) to work in an outlet; assuming you're in North America.
But if you're set on making your own board, or want something that you can hand-crank out in the wilderness, wait for others to weigh in. This is a pretty simple problem.

EDIT: I should mention that my scrap PCBs shut down output when the battery falls below 11.5VDC, preventing deep discharge.
Hi, here is a link to the battery I was going to get, I f you think there is a different one that would work better, let me know: https://www.amazon.com/dp/B00K8V2DF...olid=1PS28R9COOCYQ&psc=1&ref_=lv_ov_lig_dp_it

I believe I will be pulling about 600ma when my device is powered on. I am in North America, yes.
I would like a circuit that disconnects the battery from the load when it drops below the proper voltage, and charges the battery at the correct amperage and voltage when possible, from a variable voltage supply (DC hand generator).
I would be fine buying a pre-built board if it had these functions but am also open to DIY circuit diagrams.

Thanks.
 

ChosunOne

Jun 20, 2010
462
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Jun 20, 2010
Messages
462
ElectricalGuy, If you're still following this thread: Sounds like one of my scrap PCBs won't work for you.

If your device pulls around 600 mA, then your power supply should be able to supply more than that continuously. It also sounds--just guessing here, since you haven't mentioned how you want to use this--but sounds like you want something you can take off-grid where there aren't any mains outlets; and I've never experimented with different inputs, other than I know it doesn't strictly need the prescribed 16.5VAC 40VA transformer. Also these PCBs I have are about 12" X 4", considerably larger than most comparable 12VDC, 1A power supplies.

One of the other guys might be able to put you onto something better, or help you with designing your own PCB.
 

ElectricalGuy

Oct 31, 2022
3
Joined
Oct 31, 2022
Messages
3
ElectricalGuy, If you're still following this thread: Sounds like one of my scrap PCBs won't work for you.

If your device pulls around 600 mA, then your power supply should be able to supply more than that continuously. It also sounds--just guessing here, since you haven't mentioned how you want to use this--but sounds like you want something you can take off-grid where there aren't any mains outlets; and I've never experimented with different inputs, other than I know it doesn't strictly need the prescribed 16.5VAC 40VA transformer. Also these PCBs I have are about 12" X 4", considerably larger than most comparable 12VDC, 1A power supplies.

One of the other guys might be able to put you onto something better, or help you with designing your own PCB.
Thanks for the help!
 
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