Can you charge battery with lower voltage than the battery?

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Can you charge battery with lower voltage than the battery?

Postby Sethioz » Sun Dec 15, 2019 4:52 pm

Can you charge 12v battery with 6v charger?
Can you charge 12v battery with lower voltage?
Can you charge a battery with lower voltage than what the battery itself?
Can you charge car battery with lower voltage charger?

All those questions are answered and explained below and why people always get it wrong...


I recently decided to put a solar panel charger on my car to keep battery charged and that raised a question, is it possible to charge 12v battery with 6v solar panel? So I talked to couple of my friends who had some electrical experience (Ofcourse I have experience myself, I can connect pretty much anything, such as house electrics, computers, car electrics ..etc), but this question just started bugging me, because one friend said that you MUST have higher voltage to charge a battery. So if battery is 12v, then you need at least 12.1v to charge it.

Next obvious step was GOOGLE IT! I didn't want to google it, because I know how full of shit internet is nowdays .. and boy I wasn't wrong! There's lot of conflicting information on google, some are just pure morons who have absolutely no idea what they are saying, while others just try to bluff their way through by making somewhat "logical" assumptions, none of the posts I found by googling, had actually tried and see what happens.

This is why i'm making this post, because I tested it myself and I can ASSURE YOU 100%, that you CAN charge a battery with lower voltage!
My car battery was not enough charged to start the car, but still had 11 volts in it. I took out my voltmeter to test.
So first step, disconnect car battery or take it off completely.
Measure the voltage in car battery, which was 11v
Next step. I connected voltmeter to my battery charger and measured that.
My battery charger has two modes - low / high (10v / 11.5v)
So from that point on, it was clear to me that battery chargers are LOWER voltage than battery itself.
Final test, connect the charger to battery and also connect voltmeter to battery, voltage was still 11v, then I turned the charger onto LOW (10v) and battery voltage already popped to 12.2v!
Obviously you need to charge the car battery for at least 10 hours with a small car battery charger to have it fully charged, which should be over 13.5v when tested.

Reason why people get it wrong, is because they think of electricity like water pressure and think that pressure always goes from high to low, that's not the case.
Some posts I found were made by complete retards, they went as far as saying that battery will DISCHARGE if you use lower voltage to try and charge it ... I laughed my ass off over those moronic retards.
WHY are people talking trash about things they clearly have NEVER tested??

A battery charger has a thing called "one way diode", which means electricity flows only ONE WAY, it can't go from battery into charger .. only a moron would think that's possible. If you connect 2 batteries to eachother, like 24v truck battery and 12v car battery, then YES the 24v battery will discharge as it free flows into the 12v battery, but a BATTERY CHARGER has one way diodes that prevent reverse charging!

Some people also said that using lower voltage charger will cause the battery to blow up the charger .. yet another retard who has clearly never tested it. I read so many idiotic posts by idiotic people...

In fact, I've kind of known it since I was a kid (like 5-6 years old), I used to mess around with RC cars and other basic light systems, like converting x-mas tree lights from 3xAA batteries to USB .. etc, so I've known electrics since I was a child and I remember someone saying that the higher the voltage that you use to charge the battery, the shorter the battery will last.

So charging battery at higher voltages, will greatly shorten battery's life. Even tho charging at higher voltage will charge the battery a lot faster, it will shorten battery life greatly (depending on how often you do this), so charging battery at lower voltages is always recommended.

It's like the Qualcomm quick-charge that phones nowdays have, using that will decrease your phone battery's life. Unfortunetely I don't have enough phones to test with, but it's kind of interesting to know, what would be the difference?

For example this is how car jump starter kits work, I used one myself just to get car started when it had dead battery, it outputs higher voltage for short period of time, just enough to start the car and keep battery at 12v while starting. Even tho the jump starter is only a small 3000mA power bank, it's about how it forces higher voltage into car battery to give it enough juice to start the car.


Anyway I hope this helps those who have same question. You can't believe any of those "tech" forums nowdays, they're full of moronic idiots and apes who have no idea what they saying. I would not post this, unless I tested it myself. As I explained, I tested this myself and it's 100% confirmed! But keep in mind, your charger MUST have one way diode that prevents power going back into charger. I'm quite sure that all chargers have the diode, even laptop and phone chargers must have it, otherwise it would not work.
Another important thing is to know if your charger has auto shut-off when battery is fully charged, if you overcharge the battery with charger that doesn't detect if battery is full or not, then it will damage the battery or might even cause it to burst or leak, which means it's a throw away.

... and remember, don't believe those "tech" forums or "smart" forums where people just blabber nonsense based on their assumptions and idiotic logic, only trust those who have actually made the test and talk out of experience :-)
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