looking for battery simulator - Page 1
Forum section: electronics / testgear

author: mightyohm
author_rank: Regular Contributor
timestamp: September 03, 2014, 01:43:08 am
content: I'm looking for a piece of test equipment that will simulate the discharge characteristics of various AA cells, including Alkaline, Ni-MH, Ni-Cd, etc. in my circuit.Has anyone used such a thing? I know that Agilent, Keithley, etc offer supplies with battery simulation capability, but they are mostly targeted at lithium chemistry for mobile phones.

author: sacherjj
author_rank: Frequent Contributor
timestamp: September 03, 2014, 01:56:37 am
content: Quote from: mightyohm on September 03, 2014, 01:43:08 amI'm working on that with my lithium discharging and cycling programs. I'll be using an electronic load to generate the power used vs voltage. Then I'm using my DP832 and controlling voltage based on how much power has been served to set the output voltage.This should be programmable for any chemistry if you get discharge data at various current levels and interpolate between captured data to fit real draw.

author: Stray Electron
author_rank: Super Contributor
timestamp: September 03, 2014, 02:10:53 am
content: Can you program tables of characteristics for each type battery into a computer and then use it to control a HP-IB programmable power supply? Besides voltage and current limits, you'd have to take run time into consideration but a computer could easily track that and make the necessary changes to the PS output.

author: alex.forencich
author_rank: Frequent Contributor
timestamp: September 03, 2014, 02:59:43 am
content: That's an interesting idea. Perhaps what you would need to do is read the current out of the power supply periodically so you can keep track of the charge level of your pseudo battery and then adjust the voltage according to the curve. Not sure what changing the current limit would do for you. The only other parameter I can think of that might be interesting is source resistance, but I don't think many power supplies have an adjustment for that. I'm also not sure if that changes significantly with the charge level, so a fixed external power resistor may suffice.

author: sacherjj
author_rank: Frequent Contributor
timestamp: September 03, 2014, 03:11:14 am
content: I think the model would be accurate enough to get a voltage curve versus watt hours of discharge, at various discharge currents. Then interpolate to the closest current. You would also need to model the battery resistance. This resistance model would show itself as a voltage rebound in a shift from heavy current to light current. You might have to add a factor to use up the watt hours a little faster as the discharge rate goes up.To get a good feel for battery resistance, I would have the load shift from the large fixed current draw to a very light current draw, while doing the battery discharge measurement with the electronic load. Then the change in battery voltage will allow you to calculate battery internal resistance at that part of the curve.

author: mightyohm
author_rank: Regular Contributor
timestamp: September 03, 2014, 03:26:11 am
content: A programmable power supply would not work, as the internal resistance of the battery is a function of state of discharge and load. The resistance needs to vary to suit the instantaneous load current with enough bandwidth to fool the load into thinking there's a real battery supplying it.I'm looking to buy vs. build. This is the closest thing I have found today:http://www.graellc.net/Battery%20Simulators.htm

author: sacherjj
author_rank: Frequent Contributor
timestamp: September 03, 2014, 03:28:15 am
content: Quote from: mightyohm on September 03, 2014, 03:26:11 amIt depends on the fidelity of responses you need to large current changes. We are wanting to tune discharge and battery level software, where I'm not needing high fidelity and high bandwidth response.

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2014, 10:30:12 am
content: I have seen pure analog designs in various application notes which simulated voltage level and internal resistance of different battery chemistries and solar cells although not the negative delta V charge characteristic if NiCd or NiMH cells.

author: mightyohm
author_rank: Regular Contributor
timestamp: September 03, 2014, 10:54:22 pm
content: David, do you have a link?

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2014, 11:42:35 pm
content: Quote from: mightyohm on September 03, 2014, 10:54:22 pmUnfortunately I do not have a link to the one I was thinking of which simulated discharge and charge characteristics over variable time. Linear Technology has a couple of application notes which discuss simpler ones. Page 121 of application note 84 has one and page 35 of application note 68 has one but I do not think that is exactly what you are looking for.These are a little more complex although not the one I remember:http://www.ti.com/lit/an/slva618/slva618.pdfhttp://www.maximintegrated.com/en/app-notes/index.mvp/id/4322

author: rfbroadband
author_rank: Unknown
timestamp: September 03, 2014, 11:53:52 pm
content: the R&S NGM02 Power Supply has the ability to adjust the output resistance for battery emulation.....

author: SArepairman
author_rank: Frequent Contributor
timestamp: September 04, 2014, 09:32:41 pm
content: i wonder if you can use one of those arduino constant programable resistance devices and a power supply together for cheap