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Charging from a 12v battery. Possible to increase current?

Mordeith

Jun 30, 2017
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Hi all,
New to the forums and new to electronics in general so apologies if the following is something straightforward.
I have two rechargeable 12v batteries (of differing mAh) which I can charge off a solar panel I was given. I connect either one these batteries to an adjustable voltage regulator which is turn connected to a USB cable which I cut the end of and exposed the positive and negative wires. I can charge my devices which have the micro USB connector but the charge time(s) is extremely slow. Is this because the 12v batteries don't have enough power (even though it's stepped down to 5v by the regulator) or is something to do with the current being delivered? If it's the latter how can this be increased in order to speed up charging time?
Thanks.
 

duke37

Jan 9, 2011
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If you have two 12V lead/acid batteries, they can be connected in parallel to increase the stored charge.
A lead/acid battery should be able to supply what is needed to run through a USB cable. If it will not, then I suspect that the batteries are not being charged sufficiently and will suffer from sulphation.

Check the voltage when they are being discharged, they should not go much below 12V and should be charged to 14V.
 

Mordeith

Jun 30, 2017
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Thanks for the reply. The batteries are being charged to 12v and above. The issues I suspect lies between the voltage regulator and the device being charged. As I understand it if more current is being supplied then a device will charge faster (I could be wrong on this of course).
 

Alec_t

Jul 7, 2015
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It's my understanding that many USB-charged devices use the USB data lines to signal to the charger how much current should be delivered. The default current (in the absence of such signalling) is lower than the negotiated one.
 

Mordeith

Jun 30, 2017
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It's my understanding that many USB-charged devices use the USB data lines to signal to the charger how much current should be delivered. The default current (in the absence of such signalling) is lower than the negotiated one.

Interesting. I wonder is it possible to connect the data lines along with the power lines or would they not be recognized by the charger (since there is no 'plug' to speak of).
 

duke37

Jan 9, 2011
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The batteries will not be charged at 12V, it is not enough.
Car batteries are charged up to 13.8 to 14.4V.
Measure the voltage under load.
 
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