3 build projects, plus harvesting 16580 cells  - Page 1
Forum section: electronics / beginners

author: TheBossUT
author_rank: Newbie
timestamp: May 07, 2016, 02:01:33 am
content: Hi All,I have a few projects lined up that I want to do, trying to figure out if it is cost effective. looking for input and suggestions.Project 1: Battery pack for x2 16ft Cool White LED lights running at 12v 2.40 amps = 57.6watts hours, I am looking to run the lights for 3 hours for SUP.Project 2: Same as above but for a kayak.Project 3: Cpap battery backup for 16 hours for camping. its 24v @ 3.75amp hour or 90w, I am figuring the amp hour will at least be half since this is for a heated humidifier and heated hose I won't be using these while camping. so maybe 1.875 amp hour ?Tools for the job = Limited.* I will need to get a new 60w solder iron* different gauge wires, I most likely have this.* 16850 salvaged unprotected cells, recharging and discharging to calculate mah from salvaged laptop batteries. Was looking at this for the charging system and maybe discharge test as wellhttp://goo.gl/AqEX3spaired with thishttp://goo.gl/q49ITRto calculate the discharge rate using a 1amp load. to build the charging system is cheap as I have spare PC PSU I can use, the discharge test a bit more expensive looking to do a few batteries at a time.* Pretty sure I am going to need to get a SKYRC iMAX B6 and watch out for the knock off clones as well.* better solder* pretty much unlimited supply of used laptop batteries, talked to a E waste recycling center, they collect a few 100 pounds a month, I have 40 packs now to dismantle.* some way to balance the batteries, BMS, individual charging* buck or boost converter, I will need to either step up / down to 12v 2.4 amp for the LED project and step up or down 24v roughly 2amp for the CPAP project.* lipo firebag, I know the risks of lipos even more so with unprotected cells. most of the work is done outside, or next to the front door for a quick toss.* could I salvage a BMS from one of the dismantled laptop batteries ?I am going to be spending about $40 as it is just to get the charger and most likely another $20 - 30 for remaining supplies. Is it even worth it ? do I just by RC packs and be done with it ? I know I will still need a charger. Once I invest in the initial setup building my own packs might be worth it. figuring I can get at least 1500mah out of used cells taking them down to the 2.7v area.I know soldering the batteries is a risk as well since I won't be tack welding. 60w iron is recommended ? when pulling packs out of laptops maybe it is best to try and keep the tabs on the cells.salvaging the cells from laptops packs, I have sparked a few nothing happened other then the spark, the pack was tossed outside after, is there a major risk from a quick spark ? I know shorts are a issue. I am guessing if anything is going to happen the battery is going to get hot before thermal runaway happens.on to the project specs.Project 1 & 2 are pretty much the same, just one is a SUP the other a Kayak. I know there are already pre done kits for $200+*building the battery or buying it ? if building I was thinking of just a simple 16850 battery holder and load them in like you do the do AA batteries, depending on mah I can get from the cells I will need between 10-14, then when I am done I individually charge each cell, I am hoping this eliminates the need for balancing.Step up or step down ? to keep things simple it would be nice if I can just do 3.7 high mah pack and step it up to 12v using a protected boost converter, really looking for input here,I know I could just run the LED strip off a straight pack, but now I am pushing 16.8 volts to the strip, and they really did not like it when I was pushing 20vwires and strip started to get to hot. then everything will have to go into a waterproof box with a waterproof DC barrel connector.Project 3 CPAP battery backup, ResMed S10 elite 24v @ 90w or 3.75amp max, looking for 16 hours run time 2 8hr nights. I am figuring it will run at 1.8ap to 2amp, have not tested yet, this would be with the heated hose and humidifier off .build or buy a pack ? if can salvage cells that are at 1500mah I will need about 22, or 32 if at 1000mah, again I would like to do the style of a battery holder, but this might add to the weight and build and may not be feasible, so if I build a pack it would need a balance system or BMS. again is it best to Step up or step down, I will need to have some sort of discharge protection, think of taking the cells down to 2.7vlooking for suggestions, thanks for the comments and help.

author: sokoloff
author_rank: Super Contributor
timestamp: May 07, 2016, 09:35:28 am
content: I've tried many times to solder to batteries and finally gave up and bought a tack welder. That makes things wildly easier. You could do the battery holder design or a tack weld pack design, but I'd plan around not being able to solder them.

author: TheBossUT
author_rank: Newbie
timestamp: May 07, 2016, 10:15:30 am
content: Quote from: sokoloff on May 07, 2016, 09:35:28 amYes that could be an issue as well, along with shorts, Tack welder is not worth the investment to build my own pack, if I was always building pack it would be, but I see this as maybe being a 1 or 2 time. if the pack goes bad then I would have to rebuild. I have seen a few youtube videos of them soldering to the batteries, sandpapering might be best before hand.If I could find battery holders in the configs I need and not singles it might work better. maybe 5 or 10 cell holders then stacked on each other. The more I think about it, the more I think it might be worth just buying even if packs are not cheap.... i have already has some cells short that I was trying to salvage.... Tossed outside they went, nothing happened other then they got a bit warm.

author: sokoloff
author_rank: Super Contributor
timestamp: May 07, 2016, 11:09:12 am
content: I suspect you might be able to find an RC club nearby and someone is bound to have a battery spot welder. A well equipped hackerspace also might.Lastly, if you by chance happen to be in/near Cambridge MA, I can do it for you for just a handful of spare, used cells. It's not worth the hassle of mailing the batteries back and forth, of course.

author: TheBossUT
author_rank: Newbie
timestamp: May 07, 2016, 05:51:32 pm
content: Quote from: sokoloff on May 07, 2016, 11:09:12 amNever thought to look for RC groups. Thanks. And I live in Tampa FL.

author: TheBossUT
author_rank: Newbie
timestamp: May 08, 2016, 05:39:03 am
content: wow at a181 views and only 2 replies ? do I have this post in the wrong section ?

author: CJay
author_rank: Super Contributor
timestamp: May 08, 2016, 06:46:22 am
content: Quote from: TheBossUT on May 07, 2016, 05:51:32 pmIf you're harvesting cells from laptop batteries you'll find the interconnects are spot welded onto them and can be soldered to very easily.Cut them carefully and you have a tagged cell.

author: TheBossUT
author_rank: Newbie
timestamp: May 08, 2016, 07:54:43 am
content: Yea, currently I have been ripping them off carefully while trying not to short the cell, the tack marks are left behind and i am sure they can still be solder to, the other thing I have been thinking about is I most likely don't need a driver buck /boost converter for the LED strip lights. or under voltage for that matter, since I am shooting for a total run time of about 3 hours for the LEDs I think once the voltage starts getting low, I will be able to tell by the dimming of the Led, tho a boost buck converter would keep the Leds bright all the time, but I need to get the BMS system worked out. unfortunately I am not getting alot of help on forums or crawling the web.

author: CJay
author_rank: Super Contributor
timestamp: May 09, 2016, 03:39:58 pm
content: Quote from: TheBossUT on May 08, 2016, 07:54:43 amWell you may be able to solder to the tack marks but what I meant was cut the thin sheet material that's used to interconnect them so you have a length of that still spotwelded to the cells. Then you can solder to that.I'd not rely on an LED getting dim as a reliable indicator of state of charge, depending what current you want to draw from the LiIon cell I would definitely consider adding a protection bord that will safely disconnect the cell when it's discharged.As for charging, I recycle cells from 'dead' laptop battery packs and use the cheap TP4056 boards to charge them.

author: TheBossUT
author_rank: Newbie
timestamp: May 11, 2016, 12:53:04 pm
content: looks like I might be soldering the 16850's I cant seem to find anyone one with a spot welder near me, there is a local shop that does batteries but they wont touch them, I understand why.