Dummy Battery for Charger testing

Thread Starter

R!f@@

Joined Apr 2, 2009
9,839
Hello Guys.
How are you all.
I am in dire need to check these tricycle chargers.
I do not have the required capacity battery and is expensive to buy.
I was thinking if there is any of doing the idea that I have.

Is there any way to check the charger without battery. Sort of a simulator circuit.
Charger is rated at 60 to 70 VDC at around 5 Amps.
Batteries are SLA 12V 20AH x 5 nos so 60VDC.

I started to think but I still cannot figure out as the charger turns on when battery is connected.

If any one have any practical solution. Pls share if you do not mind.

Main Issue :
The real problem is these small vehicles used here have SLA but the supplied and the only available ones are li-on chargers. They give & sell these with the vehicle. I told the customer tht the batteries will fail and the charger is for different chemistry battery.
It seems they change the full battery pack every year when SLA is supposed to last for around 3 years.

Thanks
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,839
Tht is the problem.
I am asking around if it is possible.
I haven't made any thing yet.

How can one simulate a battery to test a charger
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,839
I was referring to the charger.
Oh...
Nothing on tht.
Chinese li-on chargers sold to charge SLA.
Rated at 60V45Ah.

Here is the fun part.
Heading says " Charger for lead acid battery"
Model says " 60V45Ah"
Output says "DC74V 5,5A"
Best part says "The charger is for lithium ion only".

So all is fine to charge the SLA until it overheats or dies prematurely. No worries. Seller can sell batteries every year costing around
USD 250.00.

I need a way to repair these for now. to do tht I need to find away to test them without a battery. A circuit to simulate without expensive batteries.

I will make a SLA charger later but even to test my charger, I need away to check without costly batteries around
 

AnalogKid

Joined Aug 1, 2013
10,170
As a load presented to a charger output, a battery appears as a slowly-increasing zener diode. It will sink a dangerous amount of current unless that current is externally limited, and the terminal voltage across the low impedance slowly increases. At the start, it is a dead short when the source voltage is greater than 2 V or so. After a while, it is a dead short when the source is greater than 6 V, and zero current below that.

Conceptually: A very long time constant voltage ramp driving a very high power emitter follower. Or something like that. Someone probably will suggest a TL431-type circuit.

For a manual-adjust circuit, consider the one-transistor "active zener" circuit used to separate the output transistor base voltages in an audio power amplifier.

Q7 in the first schematic, T12 in the second.

ak

1648560047772.png

1648560125917.png
 

Ya’akov

Joined Jan 27, 2019
6,852
What you want to build would end up costing more than a new charger. You would have to have an electronic load that also supplied voltage to the charger which diminished as the charge continued. You could try to use a power supply and a big resistor but with no idea what is in the charger, who knows?
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,839
What you want to build would end up costing more than a new charger. You would have to have an electronic load that also supplied voltage to the charger which diminished as the charge continued. You could try to use a power supply and a big resistor but with no idea what is in the charger, who knows?
I did search for appropriate SLA charger but could not find any tht suits 5 nos 12V SLA's.

What you said also was what I was thinking.
Some kind of electronic load and a voltage to initiate the charger, and then decrease load to simulate charging.
An SLA charger will charge at Voltage limited CC mode and then switch to CV when charge current drops to 0.01C value.
That is all I require to check a charger without actual batteries. Of course the load should be able to dissipate 100's of watts. Which is not a problem. If will last longer that a battery and use it all the time. But with actual batteries I would need to discharge them manually.
 

Thread Starter

R!f@@

Joined Apr 2, 2009
9,839
As a load presented to a charger output, a battery appears as a slowly-increasing zener diode. It will sink a dangerous amount of current unless that current is externally limited, and the terminal voltage across the low impedance slowly increases. At the start, it is a dead short when the source voltage is greater than 2 V or so. After a while, it is a dead short when the source is greater than 6 V, and zero current below that.

Conceptually: A very long time constant voltage ramp driving a very high power emitter follower. Or something like that. Someone probably will suggest a TL431-type circuit.

For a manual-adjust circuit, consider the one-transistor "active zener" circuit used to separate the output transistor base voltages in an audio power amplifier.

Q7 in the first schematic, T12 in the second.

ak

View attachment 263861

View attachment 263862
What is this??
 

AnalogKid

Joined Aug 1, 2013
10,170
In the center of each schematic is an example of an active zener circuit. The circuit uses a transistor and two resistors to emulate a zener diode. The advantage over an actual zener diode is that the "reverse voltage" can be varied by changing the value of one resistor. With this circuit, using a power darlington transistor (or 2-3 in parallel to spread out the heat) and a big heatsink, you can simulate a battery charging up by adjusting a pot.

Google variable zener schematic for lotsa examples.

ak
 

Ya’akov

Joined Jan 27, 2019
6,852
I did search for appropriate SLA charger but could not find any tht suits 5 nos 12V SLA's.

What you said also was what I was thinking.
Some kind of electronic load and a voltage to initiate the charger, and then decrease load to simulate charging.
An SLA charger will charge at Voltage limited CC mode and then switch to CV when charge current drops to 0.01C value.
That is all I require to check a charger without actual batteries. Of course the load should be able to dissipate 100's of watts. Which is not a problem. If will last longer that a battery and use it all the time. But with actual batteries I would need to discharge them manually.
Here’s one that claims to do it.
 
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