Modelling an Alkaline Battery in LTspice - Page 1
Forum section: electronics / projects

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 14, 2015, 05:38:29 pm
content: Hi,Recently on the Forum there has been a lot of interest in the discharge characteristics of Alkaline batteries. This thread is dedicated to building a reasonably accurate LTspice model of an Alkaline battery.This is not new, it is based on a model explained in this document:http://www.del.ufms.br/appnts.pdfThe battery modelling starts on page 260.The model presented in this document has been translated into LTspice.I will compare the performance of the model to actual test results found in this report:http://www.amstat.org/publications/jse/v21n1/dunn/RE11_021_ALDI_Stores_Primary_battery_testing.pdfThere are test for a electronic game, an electronic flash and a digital camera.Once the model has been developed it can be used to evaluate battery life extenders.I will show the development of the model in stages.Open Circuit Voltage versus State of ChargeThe TABLE function is used to generate a voltage as a function of the SOC.The SOC charge was inverted to give a DoD Depth of discharge to match the tabulated data provided in the reference.The result is:The Horizontal axis represents fresh to fully depleted.Modelling the Battery CapacityC1 was added to model the battery capacity. The capacitor is discharged at a rate proportional to the load current.In this test circuit a 0.1Ahr battery is discharged in 3600K seconds or 1 hr.Stepping the load currentThe load was modified to step the load current:The resulting curves show the battery life is inversely proportional to load current:ESR modelingSo far the ESR of the battery has been ignored. The ESR is not constant. The model has been set to use constant ESR from 100% to 20% SoC, then increase in linear fashion to 2x at 0% SOC.The results:To be continued...Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 14, 2015, 05:38:50 pm
content: Calculating Discharge Rate 'C'The discharge rate C = Capacity / output current is need to make an adjustment to the capacity of the battery at high discharge currents.The RATE signal shows:Adjusting the Capacity for High Discharge RatesThe model has been modified to reduce the capacity of the battery for high discharge rates. The values were obtained from the reference in the first post.I have also added an integrator to measure the mAh that can be extracted from the battery.These are the results:I have attached a zipfile containing the LTspice model.To be continued...Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 14, 2015, 05:39:09 pm
content: Testing the modelStandardized test are defined in an IEC publication:(No Monkeying around here !!)Electronic GameThe official test for an electronic game is 250mA for 1 hour (3600 seconds) in a 24 hour (86400 second period):And the test results show:About 8 days, 8 hours of playing time.Electronic FlashThe official test is 1A 10 seconds per minute, 1 hour per day:The results show:That about 6 days worth or 360 flashes before the end point of 0.9V is reached.The results in the test report are:The model is showing reasonably good results and can be used to explore battery life extenders.Enjoy !!Jay_Diddy_B

author: LabSpokane
author_rank: Super Contributor
timestamp: August 14, 2015, 05:57:51 pm
content: Beautiful.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 14, 2015, 09:48:43 pm
content: Hi group,I am going to introduce the concept of the 'Battery_Booster'. This is a power supply that will attempt to keep the output at 1.4V, providing the input voltage is greater than 0.7V. I have assigned an efficiency of 95% to my 'Battery_Booster'.Here is the 'Battery_Booster' model:The properties of the 'Battery_Boost' are:The output voltage is constant at 1.4VThe output power is constant, if the load is constant.The input current increases as the input voltage falls.The input power is 105.5% of the output power.The 'Battery_Booster' shields the ESR of the battery from the load.Electronic Game test with the 'Battery_Booster'I have placed the 'Battery_Booster' between the battery model and the load.The results show that the electronic game will run for 5 hours and 20 minutes:This is significantly less playing time than without the 'Battery_Booster'The reason is the nature of the IEC 60086-2 test program, it calls for aconstant currentload of 250mA.With the 'Battery_Booster' in place thepowerconsumption is constant throughout the test. If the battery voltage is allowed to fall, thepowerconsumption falls during the test.I have attached a zipfile with my LTspice model.Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 14, 2015, 10:16:06 pm
content: Hi group,The behaviour that is predicted by my model is included in the Batter... Patent application.https://www.google.com/patents/US20120121943Here is the picture:They have chosen for some unknown reason to boost the battery voltage to1.8VNote: they show a shorter running time with the Battery_Booster connected.Regards,Jay_Diddy_B

author: pickle9000
author_rank: Super Contributor
timestamp: August 14, 2015, 10:31:58 pm
content: Can you do that with the boost set to 1.6, for a comparison?Edit (sorry I see you already have sufficient info in an earlier post)

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 14, 2015, 10:46:29 pm
content: Quote from: pickle9000 on August 14, 2015, 10:31:58 pmI have arrange the 'Battery_Booster' to work at different output voltages:Here are the results showing a 1.3V and 1.6V boost voltage:The electronic game test is 1 hour per day. At 1.6V the playing time is about 4.5 hours.If the electronic game uses:1) An LDO, it will present a constant current load.2) A smps it will present a constant power load. In this case the play time should be independent, (1st order) of the Boost voltage.Regards,Jay_Diddy_B

author: ElectricGuy
author_rank: Regular Contributor
timestamp: August 14, 2015, 11:03:29 pm
content: Great Job!!

author: dcac
author_rank: Frequent Contributor
timestamp: August 14, 2015, 11:40:05 pm
content: Quote from: Jay_Diddy_B on August 14, 2015, 10:16:06 pmHere's the patent text 'explaining' fig 7:QuoteI've no idea what the horizontal line at 1.8V is supposed represent, but I believe the vertical lines shows where *their* 'Regulator' stops functioning. The 1.39V which they claim "is where a lot of electronic equipment stop operating" isn't shown, and probably the cause of much confusion. Also 1.35V is mentioned in the table underneath but isn't drawn in fig 7 either.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 15, 2015, 12:54:56 am
content: Hi,The 1.8V is the voltage that they have chosen to boost the battery voltage to.If I modify my model so I can do tests with and without the 'Battery_Booster'If the product that is being powered has an undervoltage detector set at 1.35V the product will run for 13.3 ks (kilo seconds) 3.7 hours.If the 'Battery Booster' is used it will run for 84 ks (23 hours). This why they are claiming a 6x improvement.The issue here is that the 1.35V undervoltage threshold is really high. The IEC 60086-2 test use thresholds of 1.05 or even 0.9V for some devices.A device with a 1.35V (per cell) under voltage threshold is poorly designed in my opinion.If I look at an undervoltage threshold of 1.1V:There is no improvement from the 'Battery_Booster', below 1.1V the devices will last longer without the 'Battery_Booster'.Regards,Jay_Diddy_B

author: pickle9000
author_rank: Super Contributor
timestamp: August 15, 2015, 01:05:58 am
content: Is Fig7 in the patent the batterizer or what they claim to be a typical use curve?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 15, 2015, 01:32:22 am
content: Quote from: pickle9000 on August 15, 2015, 01:05:58 amI believe it is a typical use case, to support their claim that the batteries last 4-7 times longer.They test three name brand batteries with a 50mA constant current load, with and without the Boost circuit.They choose a very high 1.35V cut off voltage to support their claims.It is a Patent Application. I am not sure if the patent has been granted.Jay_Diddy_B

author: edavid
author_rank: Super Contributor
timestamp: August 15, 2015, 03:04:07 pm
content: Jay, amazing work!Have you looked at adding a bypass mode to your booster?(Does anyone know if the Batteriser has a bypass FET?)

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 15, 2015, 03:55:34 pm
content: Quote from: edavid on August 15, 2015, 03:04:07 pmTo keep it simple I have not added a bypass mode. It would be fairly easy to do I would just change the efficiency of the 'Battery_Booster' as function of input to output voltage.In fact, in practice, you get the bypass mode for free in a synchronous boost converter. If the input is equal to the desired output voltage the boost regulator will stop switching and keep the top FET on 100% of the time.You have the opposite problem that you have a path that is only limited by the ESR of the battery and the voltage drop of the body diode if you short the output.Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 15, 2015, 04:28:03 pm
content: Hi group,Here the model for a 'Battery_Booster' with a bypass:And the results show:Horizontal axis is input voltage.The rules are:Vout = Vin if Vin > Vboost (Bypass Mode)else Vout = Vboost if Vin >0.7Velse if Vin < 0.7V then Vout = 0andif Vin > Vboost then efficiency = 99% (Bypasss mode)elseefficiency = 95%The change in efficiency will have very little impact on the battery life.I have attached a zipfile with the Battery Booster model for those playing along at home.Regards,Jay_Diddy_B

author: Stephan_T
author_rank: Contributor
timestamp: August 19, 2015, 11:06:21 pm
content: Hi Jay,great thread!Hi dcac,Quote from: dcac on August 14, 2015, 11:40:05 pmI have added some colored annotations to the graphic that make things a bit more obvious. The original patent image only shows the dropout values of the 'regulated batteries'(B). What they don't present is the ridiculous dropout value(A)"where a lot of electronic equipment stop operating" which they use for comparison.I have also added a column(C)to the table for a dropout voltage of 1V, a conservative interpretation of the IEC 60086-2 test threshold.This demonstrates how much less performance the regulator will provide, than (IEC-) standard test procedure expects.Just compare(A)to(C)and everyone can see how stupid the claim of the 800% really is.53.4 / 6.3: Standard IEC tests of thePanasonic batterygets almost 8.5 times the runtime than what they compare their product with.49.4 / 4.5: And for theSony battery, the IEC test gets even 11 times of their benchmark.PS. Has anyone any idea, what the pink area on the right side of the diagram represents? Constant 50mA at 0.1V for as long as I want? My bullshit detector smells a potential free energy source of 5mW of power.

author: timofonic
author_rank: Frequent Contributor
timestamp: August 20, 2015, 01:42:37 am
content: Hello.I'm a total n00b to simulators.Anyone knows if I can import your model to QUCS?Call me an Open Source zealot, but I prefer to use FOSS whenever possible.I'll try it this week, but I'm totally dumb with simulators and I even need to improve a lot at electronics theory.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 20, 2015, 03:11:18 am
content: Quote from: Circuiteromalaguito on August 20, 2015, 01:42:37 amIt may be possible to translate the model to QUCS. I am not familiar with QUCS and did not find a reference manual.I translated the model from PSPICE.You would need to check if QUCS supports behavioral Current & voltage sources and the table function.LTspice is not open source, but it is free and very widely used.I would try downloading LTspice from here:http://www.linear.com/designtools/software/Regards,Jay_Diddy_B

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: November 17, 2015, 05:28:29 am
content: we agree with you thatvoltagerun time under load would be different from no load condition, which was the whole point of the Monkey video to demonstrate that batteries are different thanpower suppliesLTspices. The use of abench power supplyLTspice (with no current limit setting) to determine devicecut off voltagerun times is inaccurate. Prior to our video release, the most important battery parameter, its Internal Resistance , was being ignored, because no one discovered Internal Resistance until our Engineerers came along.Pls stay tuned for our next video explaining our complete lack of understanding of technical details.

author: timofonic
author_rank: Frequent Contributor
timestamp: November 17, 2015, 01:46:28 pm
content: Quote from: CustomEngineerer on November 17, 2015, 05:28:29 amWho are you?