Hi.

I have new 12v small battery charger,which designed to charge all the types of lead acid batteries(up to 70AH).
It has 4 stage:
1)recovery mode(desulfation mode)-uses pulse mode.
2)bulk mode.
3)absorption mode.
4)maintainance mode-uses pulse mode.
and i have two option of max charging current.
I measured the charging current and voltage on car battery and i try to figure out if what i observed in my DMM is charger fault or it should work this way.

I start charging 12V/55AH(12.4v,state of charge)car battery with the higher max charging current.
At first the voltage start to rise smoothly up to 14.5v(rise smoothly at the bulk stage)while the charging current was the max that the charger could give.
And when the voltage reached this 14.5v,the voltage started to fall and rise instantly and repeatedly from 14.5v to about ~12v or ~13v,again and again...
It is happened in the beginning of the absorption stage.
As far as i know,it should be stayed at a round 14.4v and stay fixed on that voltage until the current decrease to a minimum set current,rather than,repeatedly fall and rise,shouldn't it?(i familiar only with traditional old chargers)
Isn't it a fault?
By the way,also,the charging current was instantly and repeatedly fall and rise in that absorption stage,instead of decrease smoothly down forward the minimum set current.
I know that the charger provides pulses on the recovery and the maintenance stages,but could it be that the smart charger uses pulses also in the absorption stage,and that is the reason that i saw in the multimeter that phenomenon?
or it could indicate faulty charger?

For certain reasons,i didn't mention the brand of the charger and omit some characters that could reveal it.
But the main idea is to understand if todays new technology smart chargers
are using charging method that give that behavior in the multimeter so what i had been experienced is,actually,not a fault.
Or it does?

Thanks in advance.

 

Those four mode chargers pulse the power because they charge to a certain voltage, watch the voltage as it increases and then watch how fast and to what voltage it drops too. This lets the charger know what state the battery is in. If the voltage is kept continuously high the battery will overheat.

Each company uses different algorithms to set the charge/discharge rates and times.

 

Hi PJmax.

There is no problem(as i checked with the DMM)with the transfer between the charging stages and the time that passing between the stages.At the beginning the voltage increase up to 14.5V with the max allow current(bulk stage)when it gets the 14.5v the current start slowly to drop down to the minimum set current(absorption stage) and in that point,the voltage fall down to 13.5v(maintainance mode).
My question and the problem is:why when i measured the charging current and voltage with the DMM at the absorption stage,the DMM doesn't show me constant 14.5V(as it shows with old traditional chargers),it show me jumping in the charging voltage(up and down,up and down,(14.5v to 13v to 14.5v to 12v to14.5v...).The charging current,during the absorption stage,is decreasing in general,but the DMM show me also jumping in charging current all the way down to the minimum set current(opposed to steady decreasing charging current when checked with old traditional charger.
As i said the recovery and maintainance stage have the same behavior,but there i took into account that it is because the charger used pulse on that stages.
So does the behavior(constancy jumping) that i seen on the DMM in the absorption stage is a fault or this is normal?
And does the first sentence in your post meant that,maybe,all the 4 charging stages provides current and voltage pulses on smart chargers?

Thanks.

 

A standard charger charges with a set voltage. It has no idea the status of the battery.

These new chargers apply a charge rate to a battery and then reduce it. The status, or level, of the charge in the battery can be determined by how fast the battery voltage drops. When charging they use pulses so the battery doesn't heat up as much either.

 

I thought that only in the desulfation mode and in the maintainance mode the charger used the pulses,So, i understand that it uses pulses in all the stages.
Anyway,i didn't excpected to see on the DMM the pulsing action.
I was pretty sure that,even if the charger is used pulses,i should read on the DMM only the average(constant,increasing or decreasing) values and not instantly jumping and falling values.
Why doesn't the DMM show me average value at the same manner like when i measure a current or voltage in led flashlight that uses PWM to changed modes(high,medium,low)?while the flashlight,indeed,uses pulses,but the reading on the DMM are average values and not "jumping"values?

 

In the desulfation mode they use high frequency to desulfate the plates.

You seem to be focusing around the word pulse. Maybe I should change that to wave or cycle.
The charge voltage goes up to a set value and then is allowed to discharge...... like a wave.

 

When you said"The charge voltage goes up to a set value and then is allowed to discharge."Do you mean that the charger done it rapidly as in my case?
And is it normal that the charge voltage(which stay constant at the old chargers at absorption stage)goes up to a set value,but go down(allowed to discharge)not exactly to the same discharge value?
I mean,if the set value(when the voltage goes up)is 14.5v ,and the value when it fall down(allow to discharge) appears on the DMM as 10.4V,12.1V,13.3V.....
Is it normal?

 

Yes.... that is normal. They can tell by how long it takes to fall the state of charge.

 

Thanks,PJmax,for your help.

I see that those smart chargers does not have,actually,normal behavior of absorption stage.
After the bulk stage,it seems that the charger get,immediately,into pulsed charging and behave as you mentioned.what made me thought,at first, that it was a fault.

Thanks