Home-made battery tester - Page 1
Forum section: electronics / projects

author: GadgetBoy
author_rank: Regular Contributor
timestamp: March 10, 2019, 12:38:25 am
content: I'm thinking of building a battery tester (for household cells, AAAs, AAs, Cs, Ds, 9V) from scratch, using an analog volt meter and load resistor, while also making it look kinda retro and steampunky.What are your opinions of what size of load resistor(s) I should use to get an accurate reading of battery strength?

author: jeroen79
author_rank: Frequent Contributor
timestamp: March 10, 2019, 01:10:46 am
content: That will depend on what kind of battery you want to test.Which chemistry? What capacity? What current? Single cell or battery?

author: Sceadwian
author_rank: Unknown
timestamp: March 10, 2019, 01:26:37 am
content: Use a Mosfet and opamp driven from a sense resistor fed from a DAC so you can program a constant current load instead of a fixed resistance. Then you can sweep the current draw and monitor the voltage curve to fully characterize the cell.Quote from: GadgetBoy on March 10, 2019, 12:38:25 am

author: GadgetBoy
author_rank: Regular Contributor
timestamp: March 10, 2019, 01:52:51 am
content: Quote from: jeroen79 on March 10, 2019, 01:10:46 amExcellent question, I should have been more specific (and have edited my original question). I was thinking for general house-hold cells, AAAs, AAs, Cs, Ds, 9V, etc. Nothing fancy like LiPo's or what have you.

author: GadgetBoy
author_rank: Regular Contributor
timestamp: March 10, 2019, 01:55:09 am
content: Quote from: Sceadwian on March 10, 2019, 01:26:37 amThat's quite a bit more complicated than what I was planning for (although, couldn't I pretty much accomplish the same thing with a pot?).Also, OpAmps and DACs are something I have basically no experience with, so I'm interested in the idea, just wouldn't even know where to start.

author: Sceadwian
author_rank: Unknown
timestamp: March 10, 2019, 02:39:36 am
content: But what fun is that?Quote from: GadgetBoy on March 10, 2019, 01:55:09 am

author: DTJ
author_rank: Super Contributor
timestamp: March 10, 2019, 04:11:08 am
content: As you are starting out, why not use a rotary switch to select different load resistors for the different battery types.Have a look at the data sheets for the batteries to get an idea of some load resistor values to try.All the 1.5V cells can use the same meter range. You will have to add a voltage divider for testing the 9V batteries. Perhaps use low value R's for the divider and they can also form the load.Alternatively have a battery holder to suit each cell type with a load resistor connected across the back. Use a rotary switch to connect the meter to each battery holder/load resistor combination when selected.

author: JagV12
author_rank: Contributor
timestamp: March 10, 2019, 05:59:30 am
content: The cheap China made BT-168 that I bought has these specs :1.5V : 4 ohm load, 1.0V = low 0.9V = replace9V : 215 ohm load, 6.5V = low, 5.3V = replace

author: GadgetBoy
author_rank: Regular Contributor
timestamp: March 10, 2019, 09:28:00 am
content: Quote from: Sceadwian on March 10, 2019, 02:39:36 amI'm interested in trying if you can give me some advice on where to start.

author: jeroen79
author_rank: Frequent Contributor
timestamp: March 10, 2019, 12:30:48 pm
content: Since you mentioned retro and steampunky, how about a rheostat?You can add a scale with different celltypes marked to set the test resistance/current.

author: GadgetBoy
author_rank: Regular Contributor
timestamp: March 10, 2019, 11:49:38 pm
content: Quote from: jeroen79 on March 10, 2019, 12:30:48 pmI was thinking something along those lines, with a nice big clunky switch and some big chunky retro carbon resistors.