Looking for a decent battery discharger with logging. - Page 1
Forum section: electronics / general

author: Fflint
author_rank: Frequent Contributor
timestamp: January 22, 2024, 09:13:37 am
content: Hi,I'd like to be able to test various batteries I own by discharging them and logging the data at the same time. I thought I can't be the only one with this need so perhaps someone on the forum can help.The requirements for the discharger are:- Ideally up to 1000W, but even 250W is usable.- discharge voltage 2V~28V- ability to use an external load - otherwise this device will be way too expensive- balancing at the same time as discharging if possible,.- ability to do regenerative discharge a plus.- open source firmware a huge plus(yes, I know, one can dream, right?)So far I've not been able to find any "hobby priced" hardware that can do that. The closest one can get to this is to use something like the iCharger X8 battery charger as it has the ability to do both a regenerative discharge as well as balancing and use external loads for up to 1000W of discharge. But being such a capable device it has very little logging capability. It does show the total discharged energy which is really nice, but no voltage/time curve etc. Living in the real world it is probably going to be my choice unless I find something better.Then there is the SkyRC BD250, which almost fits the bill, but for some reason its minimum discharge voltage is 5.2V which means it si useless for 1S lipos/li-ion batteries.otherwise it is almost ok (lacking many other features, but I realise I'll probably not find anything that does all of it at my "hobby level" budget)

author: RoGeorge
author_rank: Super Contributor
timestamp: January 22, 2024, 11:18:33 am
content: In case you have a SCPI lab power supply already, there is a way to use it to discharge a battery and log the voltage/current while doing that. Did that a few times, but at much smaller powers and no balancing (mostly with AA, AAA and mobile phones single cell Li-on, but also with some 12V Pb-acid):https://www.eevblog.com/forum/projects/cc-cv-power-supply-as-a-contolled-load-for-batteries-(i-e-rigol-dp832)/Another method I've used was to simply log I and V through a load (auto light-bulbs). There are some DMMs that can measure (and log if necessary) DC current and voltage at the same time, for example the Metrix mtx3283.

author: Fflint
author_rank: Frequent Contributor
timestamp: January 22, 2024, 02:21:03 pm
content: This is a pretty cool method.I do have two PC controlled CC/CV bench PSUs, but they can only source up to 10A of current (well, one of them, the other is 5A and higher voltage). For small stuff this is a nice DIY solution.Of course, I'd prefer a purpose made device, if one like it exists.

author: thm_w
author_rank: Super Contributor
timestamp: January 23, 2024, 12:28:55 am
content: The BD250 looks like an Atorch in a plastic case, though maybe with properly rated FETs as well. Its probably using a LDO so requires the 5V input to power itself.You could potentially mod the BD250 to run from external power, or get some version of the Atorch, and maybe replace the FETs.There was also an Atorch energy meter that allows external load and relay, but I can't seem to find them selling it, and I think it was App only, no PC.https://www.eevblog.com/forum/testgear/atorch-dl24-electronic-load-software/https://www.eevblog.com/forum/testgear/cheezeball-dc-load-dl24p-pump-or-dump/Then the lower end "professional" electronic loads start around $200:https://www.eevblog.com/forum/testgear/et5410-or-dcl6104-or-a-third-programmable-electronic-dc-load-in-the-budget-cat/?topicseenCould you use an external active balancer while discharging maybe?

author: Fflint
author_rank: Frequent Contributor
timestamp: January 23, 2024, 11:29:34 am
content: Thanks, DCL6104 looks nice, for a bench instrument the price is pretty good, but it is still "only" 400W. If it was 1000W I'd already ordered it and considered this problem solved :-) (despite a lack of regenerative discharge or balancing)Regarding an external active belancer, did you have a specific device in mind? I own few battery chargers(a Q8 Max and a IMAX B6AC), but I don't think they have a feature to balance while I'm discharging through another load. However, balancing is not that essential.I doubt there is one device that will meet these requirements. I ordered a cheap DL24P for just testing small 1S batteries. I don't mind having to print a case for it, or hooking up external power considering the price.