# Charging battery with DC power supply



## jh333233 (Oct 7, 2010)

Dear all:
If i would like to charge LiIon/Lead acid batts.
by a DC power supply
Suppose v is the rated voltage of the single cell,
should i give a output slightly higher than v?
let say "DC output voltage" > v?
or as long as the DC output voltage is higher than the cell's rated v would be fine
(situation with safety constant current the cell can afford)

Also, the connection should be:
negative electrode of the DC unit connects to - side of cell
positive electrode of the unit connects to + side of cell?

neglect the overcharging problem (assume over-charge circuit exists)

i kindly request your assistance.
Jh


----------



## VidPro (Oct 7, 2010)

for a single li-ion you can feed it a voltage regulated (fully regulated) 4.20v (+-.05) and your going to want the 4.25 really for doing that. There still must be a limit on the quantity of amps that can ever exist in the curcuit.

for a 12V LA cell you can feed it a voltage regulated 13.1V -13.4v forever , and it will pretty much survive, but is not the best way to treat it, or you do a 13.9-14.1 that stops and doesnt restart again till it gets down to 13v.

then you check all that and modify as nessisary.
it is correct to assume that the + goes to the + and the - Goes to the - when charging most batteries.

when getting into various Series configurations it gets more complicated. like a series li-ion pack should really have a voltage regulation for each, and to complete a balanced charge with simple voltage regulation ONLY can take a good long time. it is unwise with li-ion to just multiply the ammount of cells and voltage for the single, because of the way the li-ion is designed and its safety stuff , that is no "overcharge" balance , like you can rudely get away with on other cell items.

again, with li-ion any spikes in the voltages from a dirty power curcuit would bring the voltage up still, the power must be fully cleanly regulated, not slopped out or pulsing with an average, unless there is a termination based on the battery voltage itself.


----------



## SilverFox (Oct 7, 2010)

Hello Jh333233,

Welcome to CPF.

Charging with a power supply is possible, but you don't have all of the safety checks that you have when using a charger. You are the safety check, and if you screw up, you pay the consequences.

Note that charging lead acid batteries can result in acid issues, and charging Li-Ion cells can result in rapid venting sometimes with flame. There is enough flame in a Li-Ion cell to burn your house down, so be careful.

Battery University is a good reference on basic charging. Here is an article on lead acid charging, and here is one on charging Li-Ion chemistry.

The key in both cases is to have accurate control over the voltage and current.

Tom


----------



## Aquanaut (Oct 8, 2010)

You can charge both lead acid and Li-Ion cells using a power supply as follows: first, short the outputs and set the maximum constant current. Then, without a load set the maximum constant voltage.

When the supply is hooked up to the battery, it supplies a rising voltage at the set current until the set voltage is reached. Then the supply automagically  switches over to constant voltage mode and the current reduces at the set voltage. Charging terminates at your discretion, usually with the current in the milli-amp range.

Caution, do not leave this charging technique unattended.

Walt


----------



## Illum (Oct 8, 2010)

lead acid? sure...just don't charge at 14.4v, hook a 13.8v power supply through an ammeter then onto the battery. When the current starts to drop you'll know the cells getting there, then the current reading on the ammeter drops below <1A, unplug it. The cells not packed to the rim, but it should have 80-90% of its capacity.

remember to check your ammeter AND your battery's temperature [especially for SLA] routinely. Do not estimate your hours left charging then wait that much hours before going back and checking on it. 

I sometimes shudder at those alligator clipped wall worts for lead acids....you just don't charge cells that way :duck:


----------



## Mr Happy (Oct 8, 2010)

Illum said:


> I sometimes shudder at those alligator clipped wall worts for lead acids....you just don't charge cells that way :duck:


Actually I think with the traditional flooded cell batteries like you find in cars this is OK. As long as you don't let the electrolyte level drop below the minimum they are completely tolerant of low current trickle charging.


----------



## Illum (Oct 8, 2010)

Mr Happy said:


> Actually I think with the traditional flooded cell batteries like you find in cars this is OK. As long as you don't let the electrolyte level drop below the minimum they are completely tolerant of low current trickle charging.



oh no, these aren't for flooded lead acids
they are more like this [only Cabelas changed the design alot, it used to be just a wall wort with no LEDs]: http://www.cabelas.com/product/Cabe...h=battery+charger&x=0&y=0&Ntt=battery+charger
with flooded lead acids, the electrolyte will boil off without an explosion or swelling


----------



## VegasF6 (Oct 8, 2010)

Aquanaut said:


> You can charge both lead acid and Li-Ion cells using a power supply as follows: first, short the outputs and set the maximum constant current. Then, without a load set the maximum constant voltage.
> 
> When the supply is hooked up to the battery, it supplies a rising voltage at the set current until the set voltage is reached. Then the supply automagically  switches over to constant voltage mode and the current reduces at the set voltage. Charging terminates at your discretion, usually with the current in the milli-amp range.
> 
> ...


 
This assumes a lab power supply with an adjustable current control however. It would not be safe to charge li-ion cells if using power supply that did not have adjustable current limits.


----------



## Aquanaut (Oct 8, 2010)

VegasF6 said:


> This assumes a lab power supply with an adjustable current control however. It would not be safe to charge li-ion cells if using power supply that did not have adjustable current limits.



That is correct.


----------



## dlhylton (Apr 17, 2012)

Yes, the most important factor when charging a battery with a DC power supply is get the precise current output. 

Voltage doesn't matter as much as current does. 

Each rechargeable battery normally comes with a current rating that tells how much current should charge the battery. This may be 270mA, for instance. 

If you have a DC power supply with adjustable current, change it to the current on the spec. 

For more info about this, check out:

http://www.learningaboutelectronics.com/Articles/How-to-recharge-batteries-with-a-DC-power-supply


----------



## Illum (Apr 18, 2012)

:lolsign:

I like how they depicted the charging setup:






The duracell battery's internal resistance will effectively turn it into a resistor, and what does resistors do? 


Mr Happy said:


> Resistance does two things:
> 
> 
> It steals volts
> It puts heat in places were you don't want it


----------



## czAtlantis (Apr 18, 2012)

Also be careful not to overDISCHARGE the battery - let me clarify.
I have a laboratory power supply. It can be configured to 0-35V, 0-60A. But there is unpleasant bug...well it is not a bug, it is more a feature as it is digitally controlled with buttons, LCD display etc :-D - If I configure voltage and current and then I switch mainswitch off, on, it loads default settings where voltage is 0V and it draws current from the battery sown to 0V. This same happens when blackout or some problem occur in your local power grid. So keep an eye on it while charging.


----------



## Lynx_Arc (Apr 18, 2012)

My advice is if you have to ask how to do this online, then don't even try it. Invest in charging equipment instead. I have manually charged lead acid batteries by setting a voltage and adjusting the current to the battery about once and hour or so for about a day. I made sure and chose a current of 1/10th the capacity of the battery and stopped when I reached the listed voltage range on the battery itself. As for lithium ion.... I wouldn't even try to manually charge them just really not something that a non expert should risk.


----------

