Manually charging batteries

  • #1
Juanda
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TL;DR Summary
I'm thinking of buying a voltage source to charge batteries instead of a dedicated charger.
I want to buy a car/motorcycle battery charger because it's a very convenient thing to have.
1713299259679.png



Also, for a while, I have wanted to have a simple power source like shown.

1713297488992.png


How safe is it to use it to charge lead-acid batteries from cars or motorcycles? I know the simplest option is to buy the specific product for that task but a power supply seems so much more versatile as long as I dial in the right limits for the voltage and current in the power source.
According to this, it's not too dangerous.

I have a couple of main concerns.
  1. As the battery reaches the target voltage I assume the current will decrease. The system will not shut down completely but it will slow down. Do you think it is dangerous to take your eyes off it? The page I shared says to never leave it unattended but it feels like an overreaction as you would find in manuals so that the company cannot be considered liable. What's the risk of the charging process going wrong if the power supply is right?
  2. Batteries usually have cells in series or parallel depending on the purpose. Each cell is not always accessible. Should I worry about the charge not being balanced? Chargers in the market for lead batteries I've used don't seem to be concerned about this because they just have a connection to the two poles coming out of the batteries.
Lastly, could I use the power supply for other battery types? Being able to charge LiPo batteries would be convenient too. Such batteries do have a connector for balancing. I have been trying to find how to charge such batteries keeping them balanced with a power supply but I haven't found anything useful so far.

Thanks in advance.
 
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  • #2
Juanda said:
TL;DR Summary: I'm thinking of buying a voltage source to charge batteries instead of a dedicated charger.

Lastly, could I use the power supply for other battery types? Being able to charge LiPo batteries would be convenient too. Such batteries do have a connector for balancing. I have been trying to find how to charge such batteries keeping them balanced with a power supply but I haven't found anything useful so far.
https://www.google.com/search?q=pil...Q0NzAxajBqN6gCALACAA&sourceid=chrome&ie=UTF-8
 
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  • #3
I'm no expert on battery charging, but I suspect charging lead-acid batteries is among the simplest. You've probably seen this link posted before at PF for info on batteries and charging: https://batteryuniversity.com/articles

But having said that, I'm guessing that you would at least need to watch the power supply current pretty continuously and keep adjusting the charging voltage to make the charging go well. Better yet, you would use a power supply with a USB or Ethernet control connection to do the current monitoring and voltage adjustments continuously.

And even having said that, as careful as I am around batteries, I have at least once accidentally started a fire with a sealed lead-acid battery, and once almost had a car battery explode on me (because of somebody else's error that I really should have caught earlier).

If you do this, do it in a place where it does not matter whether the battery explodes and/or catches fire.
 
  • #4
I worked for a test equipment manufacture that charged lead acid batteries with lab type supplies set to an appropriate open circuit max voltage and appropriate max current. When hooked up the power supply would be in constant current and as the battery charged the voltage came up and the supply would switch to constant voltage. From here the current would ramp down and level out at some low value. This was done on a production scale prior to the sealed lead acid batteries being installed into the equipment we manufactured. Occasionally a battery would either fail to come out of constant current mode or appear open. Production has its advantages of having history of past battery behavior to determine a dud without having to do further testing.
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At any rate, be careful around batteries in general. I have seen automotive batteries explode. A fairly violent event that is over in less than an eye blink. I've also seen someone attempt to charge a battery with a large linear power supply with crowbar (over voltage) protection on the output. The SCR fired due to a transient effectively short circuiting the output. Naturally it also short circuited the battery. In about a second and a half, the thermoplastic insulation fell off of the wires connecting the battery. Turned to liquid very quickly.
 
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  • #5
Yes, you can use an adjustable power supply to charge batteries. You need to study up on the proper voltages and currents. I have done it successfully.

Battery chargers are normally protected against accidental reverse connections, while power supplies will be damaged. I have also had a failure: https://www.physicsforums.com/threads/fried-my-power-supply-by-doing-a-bad-thing.1049093/. I recommend that you learn from my experience and use the proper tool for the job.
 
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  • #6
Lithium batteries in the smaller sizes come with a charging protective circuit already wired-in within the shrink-tubing housing the battery. Be sure to follow the manufacturers detailed instructions regarding charging. If a Lithium battery fails they often burst into flame that is very difficult to extinguish.

Lead-Acid (car batteries) are often safe to recharge... however I have seen one being charged that released enough gas internally that the battery case was bulging! I notified the responsible party and they calmly walked over to it and removed the charging cables. He was VERY lucky! Lead-acid batteries release Hydrogen gas when overcharged, enough for a spark to create an explosion. (I would guess that the battery had a shorted cell which resulted in the other cells being grossly overcharged.)

Ni-Cd (Nickel Cadmium) batteries are somewhat safer but can go into thermal run-away under some conditions. Many years ago I was working a military contract and there was an intern (getting real-life experience in his last year of college) doing temperature testing of some very large Ni-Cd batteries. The batteries were in an enviromental chamber being charged over the weekend. Fortunately the Security dept. did periodic walks around the facility and noticed the smoke and terrible smell. No flames, but it took most of a week for the smell to go away. The battery manufacturer was notified and sent out a couple Engineers; they wanted to know the details because they couldn't get the batteries to fail!

So yes, batteries can be recharged, just expect the un-expected!

Cheers,
Tom
 
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  • #7
Lots of useful information here. Thank you all.
I think I will take two additional precautions if I proceed with this.
  1. I will take the battery away from the vehicle. It'd be less convenient than charging it on site but if something goes wrong the vehicle will not get on fire. Specific battery chargers even bring connectors to be left plugged on the vehicle but I guess they can afford that luxury because of the safety precautions built in the circuitry.
  2. I will get one of those safety bags for the charging process. I have seen them typically used for LiPo batteries. Do you think they will be OK for lead batteries too?
    1713337182808.png
 
  • #8
Juanda said:
Do you think they will be OK for lead batteries too?
Not really. When a lead-acid battery goes off it means hot acid spraying everywhere: when a Li-Po battery explodes, it's a completely different story, requiring different kind of protection.

Regarding the original question: in any regular circumstances, using the power supply can be made to be fine.

However: you don't even have the thing yet, but you are already tasting the bother what makes the difference between using the charger meant to be used in the garage, on a battery mounted in the car and using the power supply, meant to be used on a lab bench.

Won't avoiding all that hustle worth the money of having a dedicated charger?
 
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  • #9
It's clear to me that you are not really critically thinking this. Any gassing done by the battery will be trapped in the bag. Hydrogen gas. Doesn't matter what kind of charger you have if you are trapping hydrogen in a container that also has connections with a good potential for arcing.
 
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  • #10
Rive said:
Won't avoiding all that hustle worth the money of having a dedicated charger?
It's definitely tempting. It's just that they also tell you in the manual to not leave the batteries unattended anyway. I will reconsider though before making a final decision.
 
  • #11
Juanda said:
they also tell you in the manual to not leave the batteries unattended anyway.
They probably also tell you not to use it in the bathtub.

For Lead-Acid batteries fast charging needs to be done with care, slow (or trickle) charging is safe. Battery life can be improved with a mixture of fast to slow to float charging. But that would require you, or your SW, to monitor the process.

Get the data from the battery manufacturer, they should (somewhere) tell you. For example, my lawn mower uses these.
 
  • #12
It's probably just a coincidence that this showed up in my Facebook feed today...

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