Menu
Battery Emulator Tests Charger and Cell-Balance
Mobile phones need considerable testing during their designstage to make sure that their batteries and charger circuits operate in theright way. A battery emulator or sometimes called simulator has the capacity tosupply these kinds of tests which are not easily provided by the use of theactual batteries.
In order to operate appropriately, battery-powered portablesystems depend on their batteries themselves and the chargers. However, makinguse of actual batteries isn't going to allow design engineers to easily do acomplete check of the operation of the system with its battery as well as itscharger. A device that can help remedy this matter for designers is the emulatorthat can replace the actual battery throughout testing. This simulator helpssave time and is also crucial to test performance throughout production andthroughout system development.
The types of batteries which are commonly seen in today'smobile systems are lithium-ion (lithium-ion), lithium-polymer, lithium-ironphosphate, nickel cadmium (NiCd), nickel metal hydride, and lead-acid. The mostpopular kind of battery at the moment is the rechargeable lithium-ion type.This is because it creates more power for its weight (high energy density).
Building Your Own Battery Simulator RushilKK ABSTRACT Use a power amplifier circuit with TI™ single-cell Li-ion battery chargers to quickly characterize their charge profile. With an RIN × CIN time constant at its input, the output of the power amplifier simulates a battery charging. The power amplifier both sources and sinks current.
A battery emulator/simulator provides required power,current, and voltage to the system being tested with no visible distinctionfrom the real battery. A full-function simulator is able to easily source andsink current. Even at high speeds, the switching from sink to source is handledwith no trouble.
A full-feature battery emulator is able to:
- Alter its output to source the needed current and voltageprovided to the mobile system load.
- Set its output within seconds unlike a real battery whichmay demand much longer to arrive at its fully-charged voltage (under theassumption that it was discharged).
- Sink current, which makes it possible for the functioningof the battery charger to be verified.
- Emulate the internal (series) resistance of the battery tomeasure the response of the system.
- Replicate battery noise to take a look at the system'sreaction.
A full-feature battery emulator is really a power supplythat is able to sink and source current. It utilizes a kind of power supplycalled 2-quadrant or, if the voltage is negative, four-quadrant. Alternatively,a regular power supply can source current but lacks the ability to sinkcurrent. The typical source-only power supply employs output transistor that isdesigned to source current (Figure 1). The simulator (Figure 2) contains twopower transistors at the output: one that sources and the other that sinkscurrent. Additionally, it can quickly switch from sink to source currentwithout creating any issues.
Figure 1. A simplified version of the traditional power supplycircuit. It uses a singular output transistor meaning it can only sourcingcurrent. |
Figure 2. Simplified emulator power supply circuit. It can source/sinkcurrent by employing two output power transistors. |
Figure 3 represents the equivalent circuit of the TS250Waveform Amplifier displayed in Figure 4. The TS250 possesses the qualitiesrequired for a battery emulator. It can source and sink current the same way arealistic battery does. Its DC Offset control modifies the output voltage whichmimics modifications in the battery voltage. Input impedance is typicallyeither 1kO or 50O, which achieves the minimum amount of noise. TS250 features aselectable gain is either 20dB or 0dB. Several fault protections are included: over-heating(thermal), output over-current, input under-voltage, and input over-voltage.The TS250 is a high current amplifier so it can additionally be utilized tocreate battery noise like voltage ripple as well as transient voltage spikes.The TS250 accepts universal AC input power input from 105VAC to 230VAC and 50/60Hz.
Figure 3. Simplified high-Current amplifier circuit use for batterysimulation. |
Figure 4. TS250 Current Amplifier put to use as an emulator. Itfeatures dual LCD displays: One for current and one for voltage. |
Use Emulator to Test Battery Chargers
The battery emulator or simulator can evaluate theperformance of chargers to make certain they are dependable and are able tocorrectly recharge batteries. A battery could require a sizable period of timeto discharge to permit its associated charger to be analyzed; conversely, anemulator can imitate a drained battery voltage in just a few seconds. A full functionsimulator does not need a long wait to test if a charger functions the way itis supposed to and meets its specs. A battery simulator can replicate anovercharged battery and can also replicate a wrong battery model type. In theevent of a system not working correctly, an emulator can easily create “batteryvoltage” from high-to-low and low-to-high so that the circumstances under whichthe failure took place can be found.
A battery simulator is normally used for testing theoperation of the charger within the entire battery voltage (which is from 0volts to 4.2 volts for li-ion batteries). For instance, the typical operatingvoltage for a li-ion battery is 3.0 volts to 4.2 volts, but the voltage can befrom 0V to 3.0 volts if it is mostly depleted. The charger has to be tested tobe certain that it is able to charge a battery which is at any voltage inside acertain limit. By using a battery emulator, you can imitate the battery at anyvoltage by just adjusting the output voltage. Designer can measure the chargercurrent at the low battery voltage (under 3 volts for a li-ion), normal voltage(3 volts to ~4.2 volts), and high voltage (over 4.2 volts) to investigate itsfull-charged output. For instance, a lithium-ion battery usually utilizes aconstant-current-constant-voltage (CC/CV) charging method. Starting at lowvoltage (below 3.0 volts), the battery is trickle charged with a low current(which is one-tenth of the usual charge current). Between 3.0 volts and ~4.2volts is the regular fast charge current. When the battery voltage reaches 4.2volts, it enters a constant-voltage mode in which the voltage is held constant,at the same time the charger current is slowly reduced. Figure 5 shows adetailed CC/CV lithium battery charging profile.
Figure 5. Current/voltage profile for a Constant Current/ ConstantVoltage (CC/CV) charger. |
Figure 6. TS250 battery simulator is used to confirm the cell-balanceand charger's specs and functions. |
Like Figure 6 shows, the output of the TS250 batteryemulator is linked to the mobile system's battery connectors. The emulatortakes the spot of the battery pack. To test the charger, change the DC-OFFSETcontrol to change the simulated battery voltage while taking note of thecharging current. Move the output voltage of the emulator from low to high andhigh-to- low to show how the charger is reacting to changes.
Emulate ESR
A simulator can simulate battery’s internal resistance orequivalent series resistance (ESR). Battery ESR is non-static (dynamic) anddepended on frequency. As demonstrated in Figure 7, ESR is modeled as aresistor in series with a battery. Additionally, Electric Static Resistancechanges with changes in battery capacity, chemistry, state-of-charge, age,temperature, and more. An emulator is able to alter these characteristicswithout difficulty in order to replicate different types of batteries andcapacities and battery temperatures. The simulator's settings have thecapability to artificially transform the health of a battery with regards totemperature, size, and various other factors.
Figure 7. Battery Electric Static Resistance is emulated with aresistor in series. |
Test Cell-Balance Using Battery Simulator
Another fundamental use of battery emulator/simulator is toemulate a series-connected battery inside a cell pack. Various medium-powermobile systems utilize several batteries connected in series inside a pack.These batteries are primarily lithium-ion or lithium-iron-phosphate. Popularconfigurations are two-, three-, four-, and six-battery cells in series. Attachingbatteries in series boosts the input voltage of the system and makes itpossible to supply electrical power more efficiently. As a result of variationsin voltage output from one cell to the next, it is possible that most of thecells within a pack may not be at the exact same voltages. In addition, thereare cases in which one or more of the batteries are damaged or broken. When chargingcells connected in series, it is possible that some of the cells areundercharged and some battery cells are over-charged. Without the use of cellbalancing, the designer might deliberately under-charge the battery pack toprevent over-charging any of the batteries. Therefore, cell balancing isrequired to achieve the peak battery capacity as well as retaining battery packsafety.
As displayed in Figure 8, at the time one of the batteriesnears being fully charged, the active cell balance circuit diverts a part ofthe charging current away from that specific battery while sustaining a largecurrent for the two under-charged batteries. As the battery is getting close tofull, the charging current continues to scale back. This method is carried onuntil all three batteries are completely charged.
Figure 8. When one of the batteries is near being fully charged,the charging current is adverted through the active cell balance circuit. |
Figure 9. Three simulators are being used to test the charger andthe cell balancing circuitry. |
The charger, along with the balance circuitry, need to becarefully evaluated during the entire design stage. To evaluate the cellbalancing circuit needs at least one battery simulator. Design engineers canreplicate a number of cases where that battery is out-of-balance to monitor themanner in which the cell balancing circuits respond. As depicted by Fig. 9, allemulator can change its voltage on their own. In this way, it is pretty easy tochange each emulated battery voltage to imitate a cell as either undercharged, depleted,full, over-charged, or damaged. System engineers are able to very easilysimulate many combinations of these above mentioned battery scenarios (fullycharged, over-charged, under-charged, or defective) to stress test the chargerand also the cell balance circuit.
The TS250 emulator also includes a built-in current monitor.In case where the simulated cell is over charged (more than 4.2V which usuallyshouldn't occur), there should not be any kind of charging current to that specificcell. Other battery cells should still be charging like normal. If one of theemulated batteries falls under the safe voltage limit (for example, fewer than3v), the balance-circuit should either block the charger from commencing rapidcharging (by remaining in trickle charge), or it could stop high chargingcurrent to that battery. The charger and cell-balance circuit behavior isdepended on the charging system design, both hardware and software. There couldbe many charging behaviors and outcomes. Every one of the possible behaviorshas to be evaluated.
In conclusion, simulator offers huge efficient ways ofverify portable systems. To help save a lot of time, test engineers can controlthe 'battery' to any voltage at the changing the control knob. Itwill sink and source current much like a real battery would. A number of batteryemulators are often necessary emulate multiple cells for verifying balancing-circuitalong with charger circuit.
Is there a way to fool windows desktop to think that it is running off a battery (like in a laptop) ?
I need to do this to do some testing in battery mode, but I don't have a laptop on hand to do this.
I tried to find utilities on the net that could do this but I had no luck. What do you think guys?
Indrek20.9k1111 gold badges7575 silver badges8484 bronze badges
7wp7wp1,01522 gold badges1515 silver badges2424 bronze badges
2 Answers
I actually discovered that I can use my UPS to do it. So my machine is connected to a 'smart' UPS which has a communication port (not sure what the cord type is) which then you connect to your computer using USB. This then tells the computer to use the UPS as the power source instead of the power outlet, which is treated just like running from a battery on a laptop. You can also use this to determine how long the UPS will last for when you lose power so you have enough time to close down and save all your work before the UPS runs out of power as well.
Brian T HannanBrian T Hannan47633 gold badges1111 silver badges2626 bronze badges
This is tricky to pull off. The on-battery/on-power flag is provided by ACPI in the BIOS, and the flags are handled in the kernel as part of the ACPI driver. Near as I can figure, lying to this driver layer is not exposed in any way. However, it does look like Microsoft has a discrete device for the battery and AC adapters themselves, so a special AC Adapter driver may allow you manually select your power state. I don't know of one, but it is a place to look. Alternately, a special 'power development' ACPI layer may be lurking somewhere.
SysAdmin1138SysAdmin1138