Automobile Battery As A Current Source To Test Electronic Load Design? - Page 1
Forum section: electronics / beginners

author: t1d
author_rank: Super Contributor
timestamp: November 16, 2018, 08:57:17 pm
content: I have built a 30v/2a/60w e-load and I have done some testing, with a single 30/3a CC PSU. Here's that thread:https://www.eevblog.com/forum/projects/electronic-load-project-ltv171-irfp250-with-kicad-files/I need more wattage, for testing, so I posted a thread on paralleling my two PSUs (Schottky diodes on order.) But, even the two supplies may not have sufficient wattage, for the Single-MOSFET test rig and certainly not for the Two-MOSFET 30v/4a/120w final design.I asked my brother for suggestions and he had what I think to be a simple, inspired idea... Just use an automobile battery.We discussed the safety concerns that we could think of...- The DUT input is already fused.- Add a diode, to prevent back-flow, to the battery, should things get weird.- Be v-e-r-y careful, when advancing the load and monitor everything carefully.But, more advice might keep me out of some unforeseen trouble. So, is there anything else that I should consider?I am aware of car battery safety protocols and the avoidance of explosions...Thanks, for your help.

author: Benta
author_rank: Super Contributor
timestamp: November 16, 2018, 09:10:43 pm
content: 4 A is peanuts for a car battery. Put two in series for ~27 V and do the testing. Just be careful not to short the battery poles somehow.

author: Monkeh
author_rank: Super Contributor
timestamp: November 16, 2018, 09:11:48 pm
content: Quote from: Benta on November 16, 2018, 09:10:43 pmOr, y'know, use afuse.

author: t1d
author_rank: Super Contributor
timestamp: November 16, 2018, 09:46:54 pm
content: Good ideas, guys... Thanks!Quote from: Benta on November 16, 2018, 09:10:43 pmGood suggestion.

author: schmitt trigger
author_rank: Super Contributor
timestamp: November 16, 2018, 09:51:38 pm
content: Don't wear a metal band wristwatch when working with a car battery.

author: IanB
author_rank: Super Contributor
timestamp: November 16, 2018, 09:51:45 pm
content: Just be aware that an accidental short of a car battery will make any wire red hot, white hot and then molten in short order. Skin contact is absolutely to be avoided unless you wish to deal with nasty burns.

author: Benta
author_rank: Super Contributor
timestamp: November 16, 2018, 10:09:23 pm
content: Quote from: Monkeh on November 16, 2018, 09:11:48 pmRight, Mister Bleeding Obvious. It should have read "battery posts", my mistake.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 17, 2018, 12:34:57 am
content: Quote from: t1d on November 16, 2018, 08:57:17 pmdo not introduce sparks or fire near it esp when its being overcharged. hydrogen gas produce from it may introduce military grade explosion. in anyway make sure the battery's terminal will not get shorted. cover the terminals with something to avoid this accidentally such as dropping something metallic on it etc. if its shorted with small wire, it will create nice firework, but if its shorted with big and thick metal, it may introduce military grade explosion. anyway, no need extra taboo with SLA battery its a nice power source. just treat it with respect.Quote from: t1d on November 16, 2018, 08:57:17 pmi dont see any real advantage to this since SLA may take some charge (current backflow) to some extend, a properly rated fuse may be enough to avoid high current charging, and i dont think your circuit is high powered capable charger. but well, its not wrong to put the diode its just few voltage drop. ymmv.

author: t1d
author_rank: Super Contributor
timestamp: November 17, 2018, 02:35:35 am
content: Quote from: Mechatrommer on November 17, 2018, 12:34:57 amI had learned of this possibility, when I was a teenager. In my late thirties, I was at work, one day, and I heard a great boom. Moments later, the boss stumbled in; it was the boss that had blown himself up.His eyes were rolling around, in his head, but he was not seriously hurt, thankfully. However, it did ring his bell.He got off, light... It could have been really tragic.So, I always have that in mind, when working with batteries...

author: spec
author_rank: Frequent Contributor
timestamp: November 17, 2018, 08:11:27 am
content: BTW Don't drink the acid or drop the battery on your foot