Question about charging concept of different battries.

[Qaisar Azeemi]

Hi friends!

Whenever we want to charge a battery..... all we have to do is to in-feed it a specific amount of current. This charging current starts a Reverse reaction in the chemicals of the battery and the number of electrons changed in both plates and thus the battery gets charged.....

Now my Question is that why we use different chargers for different types of batteries? that is according to my knowledge the charger of a 6v lead acid battery can not charge the battries of other chemistries (Li-ion, NiMH etc)
what is the reason behind this? why the charger of one battery type do not charge the the other battery type of same rating?

thank you

 

[kubeek]

For starters, different types have different voltages, so you can't charge a 4.2V li-ion with a 6v lead acid battery charger. Also different battery chemistries have different limits, like maximum current and voltage allowed, and different current-voltage profiles to get charged the best way.

 

[Qaisar Azeemi]

thank you kubeek. what about Pb-acid battery. what happend to it on overcharging? will it brust in flames or silently damaged? and what should be the maximum current to charge a Pb-acid battery?

 

[kubeek]

Sealed ones will burst or vent beacause the current produces hydrogen and oxygen after the charging is finished. Try reading here **broken link removed**

 

[MrAl]

Hi,

To add a little to this thread...

As kubeek pointed out, the first thing to think about is the different voltages. If you try to charge an Li-ion with a lead acid battery charger you could actually cause the cell to burst into flames. The problem there is that the Li-ion needs a limit on voltage that is less than the lead acid battery (6v type) so it will attempt to overcharge it by a huge amount.

It's interesting though that the charge regimes of both lead acid and Li-ion are very similar, starting with current limiting and ending with voltage limiting (for the most basic charger). If there was some way to change the voltage setting it could work, as long as the lead acid battery charger was designed to limit the voltage to within the tolerance needed for Li-ion without going over that limit. Since lead acid battery chargers dont really have to be that accurate, there's still a chance it wont work. So the best bet is to either buy or build a charger that will work for each battery type and use each one only for the intended battery type. This of course means having several chargers laying around if you use several different types of batteries.
You could however build a combination charger that does both lead acid and Li-ion because of how similar they charge. You'd have to have a switch to switch between types. The current limit is often different too so you'd have to have that change with battery type as well. To make the switch fail safe you'd design it so that when the switch is 'open' it charges the Li-ion (lower voltage, lower current limit) and when it was 'closed' it charges the lead acid (higher voltage, higher current limit).

 

[kubeek]

You could however build a combination charger that does both lead acid and Li-ion because of how similar they charge. You'd have to have a switch to switch between types. The current limit is often different too so you'd have to have that change with battery type as well. To make the switch fail safe you'd design it so that when the switch is 'open' it charges the Li-ion (lower voltage, lower current limit) and when it was 'closed' it charges the lead acid (higher voltage, higher current limit).

I don´t think that is a good idea. Lithium batteries are quite dangerous, and if you by mistake charge it on the wrong setting, the battery WILL EXPLODE or at least burst into violent and inextinguishable flames. Google li-ion battery fire video to see what it´s like.
I wouldn´t rely on a simple switch setting to decide if I set my house on fire or not, and it doesn´t even have to be you who puts the battery into the charger, could be wife or kid who doesn´t realize what can the wrong setting do..

 

[crutschow]

thank you kubeek. what about Pb-acid battery. what happend to it on overcharging? will it brust in flames or silently damaged? and what should be the maximum current to charge a Pb-acid battery?

Unsealed ones will boil the water away. Sealed ones may explode or break open as kubeeck noted.

The maximum charge current is determined by the size of the battery. The manufacturer will usually speciify this current.

 

[kubeek]

This is a nice video of overcharged li-ion with disabled protections https://www.youtube.com/watch?v=SMy2_qNO2Y0&feature=related

 

[bountyhunter]

Hi,


You could however build a combination charger that does both lead acid and Li-ion because of how similar they charge.

Best way is to have a smart charger that has a communication line to the battery and the battery contains a memory chip that tells the charger who it is and what it needs.

 

[bountyhunter]

This is a nice video of overcharged li-ion with disabled protections https://www.youtube.com/watch?v=SMy2_qNO2Y0&feature=related

I remember many years back, I went out to lunch with Bob Pease and his buddy Bob Milne, the editor at Electronic Design magazine. After a few beers, I pitched an article to Milne about battery charging and one of the terms I had used was "Rapid Spontaneous Disassembly" describing such an event........ Milne said he wasn't interested in the article. Next month ED ran an article about batteries and he had swiped my catch phrase. Oh, well....

BTW, this was early 90's before Li-Ion was around. The new (at the time) NI-MH batteries were seen as dangerous because they vented hydrogen when overcharge. Hydrogen is the gas that cooked the Hindenberg.

 

[MrAl]

I don´t think that is a good idea. Lithium batteries are quite dangerous, and if you by mistake charge it on the wrong setting, the battery WILL EXPLODE or at least burst into violent and inextinguishable flames. Google li-ion battery fire video to see what it´s like.
I wouldn´t rely on a simple switch setting to decide if I set my house on fire or not, and it doesn´t even have to be you who puts the battery into the charger, could be wife or kid who doesn´t realize what can the wrong setting do..

Hi,

Ha ha, i was assuming that an idiot wasnt operating the charger, maybe a mistake?

This was supposed to be a simpler charger, but then again it's not that hard to implement ACTIVE cell detection. Would require a uC though so the complexity goes up a little, and of course with that a secondary monitoring system.

And point of fact is that i have a charger that has a switch to select between high current and low current for different size cells. Knowing the dangers of charging these cells beforehand i never had a problem with the switch.

Just to recap a little too, for any of these systems there should always be a secondary monitor system anyway.

 

[Qaisar Azeemi]

I am really very thankfull to all who have replied.

now a days i am tring to develop chargers to charge Lead acid battries and i think the maximum charging current should be 30% of its AH rating. i.e; for a 6v 4.5ah sla battery the charging current must not be more than (4.5*30)/100 = 1.35A ....

and minimum current must not be less than 10% of its AH rating 0.45A for above example.

am i right in my concept????

if yes then is it applicable to both Flooded type pb-acid and SLA battries?