Lasting Lithium Battery Replacement - Page 1
Forum section: electronics / repair

author: SaabFAN
author_rank: Frequent Contributor
timestamp: July 11, 2016, 07:53:32 pm
content: As failing batteries in older test equipment are a constant annoyance, I was wondering why so many people are replacing the old battery with exactly the same battery-type or put a CR3202 socket in there instead of using a LiPo Battery and a small charging-module powere from the +5V Rail.If the chips that are being powered by the battery are 5V devices, I don't see any problems and 50mA more on the +5V rail drawn by the charger should the battery be really empty after a prolonged off-time should be manageable for almost every device.The only problem I can imagine right now is that LiPo batteries do self-discharge, so the device has to be turned on every few weeks to keep it full.The cost for something like this is about 7 to 8€ btw.

author: sync
author_rank: Frequent Contributor
timestamp: July 11, 2016, 09:49:58 pm
content: You are talking about memory backup batteries, right?They last a lot of years or even decades. A simple solution which works. No need for over-engineering. Also, the need of powering a device every few weeks is a no-go.

author: MosherIV
author_rank: Super Contributor
timestamp: July 12, 2016, 09:31:54 am
content: QuoteAs sync already said, the batteries for memory back up last a long time.The extra circuitry needed for rechargeable batteries outweigh the benefits. The whole Lithium battery field is relatively new (only been around for 5-8years) so there is little in field experience of how well they last over time (decades), we know how well existing technology batteries perform over time.

author: calmtron
author_rank: Regular Contributor
timestamp: July 12, 2016, 09:50:53 am
content: I've replaced several lithium memory backup batteries which have been in circuit for 30+ years and still measured good. Tadiran has models with a 40 year proven lifetime. I very much doubt that an ordinary LiPo will survive for such a long time.

author: Ian.M
author_rank: Super Contributor
timestamp: July 12, 2016, 10:10:14 am
content: I think you mean "The wholerechargable LiPObattery field is relatively new ...".Low drain rechargable Lithium cells have been around since the late 90's but they aren't cheap, nor are they an easy retrofit if the product didn't originally use them.Generally its best to replace like with like, for reliability reasons if nothing else, though sometimes cobbling in a battery holder or a higher capacity battery of the same technology makes sense.For high value test equipment or similar kit that will be a PITA to reconfigure/recalibrate (or worse), one buys the best quality freshest stock leading brand compatible battery available and fit it as originally installed then put a service sticker "Scheduled backup battery replacement" with a date 10 years ahead on the outside of the case. Odds are, it will be someone else's problem and they will be grateful you didn't do a hack job.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: July 12, 2016, 11:35:38 pm
content: Okay, thanks for clearing that up.Next time I have some T&M-Equipment here that needs a new battery I'll put a normal battery in there againBtw. On my Philips PM3320A I used normal AA-Batteries in the battery-holder on the back of the unit and discovered that they had been leaking for quite some time when I pulled it out of my "Philips-Tower".Measuring the connectors, I discovered that the instrument is putting a voltage across the battery-terminals. It seems to me that there is either something wrong with a diode inside the Scope, or the Philips-Engineers had the same idea I had: Use rechargeable batteries.

author: Kjelt
author_rank: Super Contributor
timestamp: July 13, 2016, 08:48:37 am
content: It would be nice if for there was an fram or eeprom pin equivalent for the battery backed up sram chips in the devices.

author: Kilrah
author_rank: Unknown
timestamp: July 13, 2016, 08:54:50 am
content: As mentioned - even unused shelf life of a li-po is shorter than the expected in-use lifetime of a typical backup battery.

author: CJay
author_rank: Super Contributor
timestamp: July 13, 2016, 02:09:08 pm
content: Quote from: SaabFAN on July 12, 2016, 11:35:38 pmOr just possibly a previous owner had similar ideas.