Simulating lead-acid battery array (up to 48V nominal) - Page 1
Forum section: electronics / testgear

author: forrestc
author_rank: Unknown
timestamp: May 09, 2022, 09:39:39 pm
content: In my "day job" (work for myself) I make various products that monitor things like UPS and solar charges which expect to be able to connect to a battery array to work properly. Note that these items both charge and discharge the battery.Traditionally, we've maintained a set of 12V 9AH batteries that we used for this type of thing. The problem is that the need for this is relatively intermittent - we may go months without this need, and then need them for a short (or long) period before they go back on the shelf. Trying to keep these maintained and ready to go when needed can be a challenge - float charging relies on the chargers not failing or being unplugged. Regular maintenance charging requires one to remember to do so. Then there's the set of issues related to the inconsistent remaining life of each individual battery when one wants to put them together into a 48V array, especially if maintenance has failed in some way.It would be a lot easier to just have a device which electronically simulates a battery. Basically a DC load combined with a power supply so that charging currents are burned off during charging cycles, and DC power is provided during charge. The other advantage is that we could simulated a failed/low battery, and so on.I've looked at the commercially available all-in-one products designed specifically for this. Either they are not suited for the higher voltage (often topping out at 20V), or they're prohibitively expensive ($10KUSD or often way more)So, I'm looking for either something purpose-built for this, or some alternative to use existing products I may have (Such as the DC load and programmable power supplies).

author: tautech
author_rank: Super Contributor
timestamp: May 09, 2022, 10:22:46 pm
content: What are your current requirements ?A couple of ideas for PSU's come to mind.....both programmable.SPD3303X-E using 2 channels in a series configuration for 60V @ 3A or double that if you series 2 units together in series output mode.SPD5000X models for more grunt and even higher voltages.https://siglentna.com/power-supplies/sps5000x/

author: thm_w
author_rank: Super Contributor
timestamp: May 09, 2022, 11:07:11 pm
content: Looking at the Keithley 2302 spec sheet:"ISOLATION (low–earth): 22V DC max. Do not exceed 60V DC between any two terminals of either connector."I wonder if with any of these simulators can simply be placed in series. It looks like most don't allow it with similar output to earth limitations.Quote from: tautech on May 09, 2022, 10:22:46 pmTake a second before peddling your wares and read OPs post."It would be a lot easier to just have a device which electronically simulates a battery.Basically a DC load combined with a power supplyso that charging currents are burned off during charging cycles, and DC power is provided during charge. The other advantage is that we could simulated a failed/low battery, and so on."Whats the load capability of the SPS5000X, a few watts?

author: tautech
author_rank: Super Contributor
timestamp: May 09, 2022, 11:34:37 pm
content: Quote from: thm_w on May 09, 2022, 11:07:11 pmPull your head in yourself and read the whole post:Quote150V programmable loads are everywhere but start pushing PSU's above the industry standard safe 30VDCand available options are much less.

author: thm_w
author_rank: Super Contributor
timestamp: May 10, 2022, 12:04:52 am
content: "existing products I may have"So OP, what power supplies, electronic loads, etc, do you have already?

author: forrestc
author_rank: Unknown
timestamp: May 10, 2022, 07:13:45 am
content: Quote from: tautech on May 09, 2022, 11:34:37 pmIf it was just that easy.For example, my bench "modern" supply is a MX180TP. Providing 48VDC or 60VDC or even 120VDC isn't a problem. I also have a Sorenson LHP 60-18 on the bench which will do 60V @ 18A. There are probably a half-dozen others floating around which will do at least 50V, and usually up to 60V. I generally don't even consider the purchase of a power supply anymore unless it will do the higher voltages. So that isn't an issue here.And yes, there are a few DC loads floating around, although I think the only SCPI programmable one are the HP6063B's which we use (and spare) on the automatic tester. Most of the others are lower-end units which aren't programmable with any standard interface. But procuring another one isn't a big issue.If it was as simple as hooking a DC load and a power supply in parallel I would have already done it. Electrically this isn't difficult - about the main gotcha is that you'd want to provide a diode in the output of the power supply as most power supplies are NOT happy when they see a higher voltage on their output than they are putting out.The real problem is the control software which needs to adjust both the load and power supply behavior based on the simulated condition of the battery in its charge cycle.

author: forrestc
author_rank: Unknown
timestamp: May 10, 2022, 07:27:39 am
content: Quote from: thm_w on May 10, 2022, 12:04:52 amI have a collection. The easiest to lay my hands on are the MX180TP and the Sorensen LHP 60-18 on my bench. If I raid the supply room, there are a few others, typically older HP "System Power Supplies" which are what we use on the automatic test system, and spare in-house. I've got a few others floating around here and there.The DC load side is a bit less easy to come by. The "universally programmable" one is probably limited to the HP6063B's which are also on the automatic test system and spared. On my bench I have a couple of array 3711A's which really need to be replaced, but I haven't found one which I really felt was enough better than the 3711A's to justify the cost. (Generally I'm just running them in CC mode).I really should have probably added "or might be willing to purchase". Although buying a $10K (or $100K) purpose-built battery simulator is out of the cards, adding additional general-purpose test equipment which is likely to have other uses is definitely in the range of possibility.Note that generally the load on this simulator will be close to zero - I'm largely looking at the unloaded case. The only gotcha there is in the case of a UPS, they'll occasionally switch into test mode or similar which means that your load goes up to some higher amount than a typical trickle charge, or couple watt draw of a solar charge controller. I wouldn't be using this with a load attached to the UPS so there isn't any need for an extremely high current.