Guess the Battery ! - Page 1
Forum section: electronics / repair

author: djococaud
author_rank: Regular Contributor
timestamp: June 23, 2015, 01:10:32 pm
content: Hi boys and girls !I have a solar garden light to repair (similar to thosehttp://www.amazon.fr/d%C3%A9tecteur-mouvement-production-Projecteur-rechargeable/dp/B00MBDAKLI/ref=sr_1_7?ie=UTF8&qid=1435064391&sr=8-7&keywords=spot+solaire)This LED projector was just great and worked fairly good...until now !The culprit is the battery, which is completely dead ! (0V accross the cell, without the protection circuit)I can't find anything on the battery markings, just It's a 3.7V 2000mAh...I would bet It's Li-ion, but not sure (could olso be NIMH...). The charging circuit doesn't help as it's only the solar panel through a simple diode.Do you have an idea of the chemistry of this battery ?Thanks guys !

author: EEVblog
author_rank: Unknown
timestamp: June 23, 2015, 01:12:07 pm
content: Based on the size and shape that looks very much like a standard 18650 cell with a protection circuit.

author: djococaud
author_rank: Regular Contributor
timestamp: June 23, 2015, 01:17:23 pm
content: WOW, 2 min answer delay !!! awesome !Thanks, i will check the batteries prices/availability in my electronics local store...

author: djQUAN
author_rank: Frequent Contributor
timestamp: June 23, 2015, 01:30:13 pm
content: Yes, definitely 18650 Li-ion. But I guess the replacement batt will end up the same as it appears the charging "circuit" is relying on the over charge cutoff of the protection PCB (cuts off at 4.5V or higher) rather than terminate at 4.2V as proper chargers do.I would add a shunt regulator IC / circuit to burn off the excess voltage. A TL431 and a transistor could work.

author: amyk
author_rank: Super Contributor
timestamp: June 23, 2015, 01:47:06 pm
content: Batteries marked "ASO" brand is made by a Chinese company with no English name other than "Shenzhen Zhuoneng New Energy":http://www.szznp.com/They seem quite honest with their capacity,according to this test I foundYou can replace it with any other 18650 of same or greater capacity.

author: djococaud
author_rank: Regular Contributor
timestamp: June 23, 2015, 01:53:38 pm
content: I think I found the actual product I bought a few years ago...http://www.amazon.fr/Projecteur-solaire-led-lumens-panneau/dp/B00GNAUPW4/ref=sr_1_24?ie=UTF8&qid=1435066663&sr=8-24&keywords=projecteur+solaireSurprisingly they wrote: 3.6V/2000mA NIMH, for 6 to 8 hours of light (I olso checked on solairepratique.com who sales this projector...)Since the charging circuit is crap (I should say inexistant), I could test a cheaper NIMH and see if I get 6 hours of light... (no big deal if the price is low)

author: djococaud
author_rank: Regular Contributor
timestamp: June 23, 2015, 01:56:25 pm
content: Thanks Amyk,So Li-ion It is...Let's see if my local store has some...

author: mikerj
author_rank: Super Contributor
timestamp: June 24, 2015, 03:31:13 pm
content: Quote from: djococaud on June 23, 2015, 01:56:25 pmIf you aren't going to fix the basic overcharging charging problem then it's very important vital that you use a protected cell or move the protection circuit onto a new cell.

author: djococaud
author_rank: Regular Contributor
timestamp: June 25, 2015, 06:53:30 am
content: No worries, I used a (not cheap !) camelion ICR18650 Battery with an integrated discharge/overcharge protection.Since I didn't find a battery with wires I just reused the wires of the old battery (with the connector) And I soldered them on a battery holder...Just good as new ! (I must still wait a few charge/discharge cycles to be sure...)just for info :http://www.camelionbattery.com/attachments/article/133/ICR18650%20Announcement.indd.pdf

author: amyk
author_rank: Super Contributor
timestamp: June 25, 2015, 12:09:15 pm
content: Amusing that the datasheet for that cell says in huge type "up to 500 cycles" and then in the small text says "more than 500"...You may want to check the open-circuit voltage of the solar cell with bright light - if it's constantly hitting the protection cutoff the cell will be (slightly) overcharged every time and fail much earlier. Adding a shunt regulator would be a good idea.For this sort of "accumulator"-type application, limiting charge voltage to a bit less than 4.2V will result in longer life.

author: djococaud
author_rank: Regular Contributor
timestamp: June 25, 2015, 12:55:28 pm
content: Indeed...well I will see...if it lasts 2 more years, then I will just replace the battery in two years and don't bother modify the circuit!And if it fails earlier...I will upgrade to a better system (with citizen LEDs and Buck driver...or anything more efficient than the current linear driver in this thing...)