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Fixing Broken Door Handle on Toyota Corolla
Battery powered usb 2.0 hub
Lithium upgrade to 18v Black and Decker Single Source battery pack
Aftermarket van roof vent
The cheap cells I bought don't do well on a weed wacker, but they aren't soldered in, so they can be swapped out for better if I wanted. I still have a couple of cheap nicad packs and between all 5 I can do what needs to be done. The cheap cells were like $1 each so I didn't expect miracles. I have bought completed packs from HobbyKing and they are careful to grade their packs/cells and charge accordingly. I built 2 packs from 3.2v lithium iron phosphate cells for a cordless drill at work and those work well. Very fast recharge times.But even those had issues with the spring loaded battery holders softening from heat when improperly recharged. The lithium iron phosphate cells got hot enough to melt off the plastic label when overcharged. I was using the wrong charger. They also quit working, but at least didn't catch fire.
I just made one of these. Used good, high quality battery holders and ensured the wire gauge was more than adequate. I bought batteries similar to what you described (over voltage/current protection) With no load, voltage is right at 24VDC. When I tested on the trimmer, as soon as the load increased (like when trimming heavy grass), the power dropped considerably, to where it was inadequate for trimming. I could pull the battery out and see the voltage coming back up (from around 22VDC by the time I got it out). The batteries were warm, but not hot. Anybody had any issues using this with your trimmer? I did try replacing 4 of the cells with standard (no protection) 18650 batteries, but same result. Unfortunately, I don't have 6 to try. Could this be an issue with current protection kicking in on the batteries?Thanks!!!
Thanks for the info. I have the UltraFire BRC 18650 4500mAh, looks like the same you linked to. From what I can find on the net, they are definitely a lower current battery. I am having trouble finding "C" ratings for specific batteries, but can back it our based on the formula (C = mAh*MaxCurrent). I am seeing some higher end LG and Sony 18650 batteries with ~30A max draw. Would these be adequate? What do you use for your trimmer, and how does it compare with original nicd? Thanks!!!
For high current draw you need cells rated with 25C. A weed wacker is pretty much a dead short when trimming grass. That's one of the reasons the original nicads don't last long. A cordless drill doesn't pull anywhere near the current and therefore is much gentler on the battery pack.http://www.tested.com/tech/502351-rc-battery-guide-basics-lithium-polymer-batteries/
So, the red wire is soldered between the 3-packs. What happens to the black wire from the same pack? Is it soldered along with the red?"The cells are held in two spring-loaded plastic 3-packs that are connected in series with one wire soldered between them [the red wire visible in the second picture]."
Just to be sure I've got this right, I've attached a diagram of what I thought I've heard, and the wiring diagram of my CDV-700. Is this right?
Thanks again David. This was great information and will enable me to complete the task.
Thanks so much. This is a great help. Have you any experience with the Russian SI-8B probe? I just ordered one and understand it also uses 400V, so I'll need 5 diodes. It has 4 pins on the back, so I'm unsure of the needed connections.
dang... I guess I need to buy 4 more plastic holders then... Looks like the seller on the posted amazon link is out of them for now. Thanks,Bob-one more thing... I'm having a difficult time with the factory solder on the 2 metal blades (plus/minus)... why won't it melt? I even tried a blow torch... :)
Cool did that and it charged up to 24v in about an hour or soft on 21. That being said the pack was plenty cool as far as i could tell but on the other hand my power supply was a tad warm haha. Maybe I'll add a cooling fan to it LOL!
Ok. My last question, I hope. HahSo I got a stronger 24v power supply. (2Amp out). It meters out at 24.2 or so, which I'm good with, But so.... I need to bypass the circuit board in the original charger right? And solder the power leads to the battery connectors directly? I just thought I'd try using the board and fried a resistor on it. Doh.
My battery holders with the "coil spring" type negative cooked too. I found the holders where the cells "snap" in more robust (link in my comment below)
This was due to the amount of current, not a short or anything
OK... I just got everything wired and as soon as I put the first 3 batteries in... it started smoking! I immediately got them out and noticed that it was the 2 wires(red and black) that created a series...? They look like tiny 22g or 18g at best..?
yes, I did have to remove both center screw posts to make it fit.thanks! - Bob Barnes
just ran the pack in my blower, it works. LOL. ran it until shut off and now going to fully charge the pack, however, with 210mA output of the charger, i suspect this will take quite some time, as the total capacity of all the cells is 2600x6______________________on my charger, there is a Green LED, i seen yours has a red. well, after about 2 hours now my voltage has not changed, it was 21.8-9 on my voltmeter after running till it stopped on the blower when i put it on, and still sits there now. am i missing something? or is this 210mA power supply just to much a sally for it? the charger still says its puttin out 24.5v when i test it without the pack on. - xbeerd
just wanted to add, the battery holders i mentioned below in my comment are smaller in width than the plastic holders noted in the instructable. the plastic is a little thinner, but the contacts are larger, the wire coils on my other holders fried when i tried to use this in my weed whacker.http://www.amazon.com/Frame-Black-Plastic-Battery-...here are some pics, i also drilled a couple small holes in my charger to insert my DMM probes in to check voltage. and you can see my ghetto fabulous diode boards, once i get this all firmed up i'll be 3d printing a small addition tot he top of the charger to conceal.
if your packs are like mine, you'll need to remove both. or maybe one you could shave down with a knife, but honestly. i just used a side cutter/wire cutter and snipped it off in the span of a few mins, i dont see much reason to try to save one of them.
i needed 12 of the diodes i got to drop the voltage down to 25v, actually its 24.7v when charging, however, seems as the battery holder isnt robust enough to hand the current output, coils on the grounds cooked and barely makes good contact because of how tight the cells fit, my pack voltage reads 0v after being on the charger for an hour, but each cell reads 3.7v so im leaning at the battery holders as being the issue here.i went and ordered this style of cell holder... http://www.amazon.com/Frame-Black-Plastic-Battery-Holder/dp/B00S4YLG34/ref=sr_1_16?ie=UTF8&qid=1465170875&sr=8-16&keywords=18650+uxcell+3
thanks...that's what I thought I would do as well. I'm thinking just removing one of the center screw posts will make it fit. - Bob Barnes
im curious, what is the amp output on your charging power supply (wall wart)mines 210mA@24VDC. - xbeerd
to get my packs to fit, i just had to snip off the center screw holes in the original battery casing. - xbeerd
so, i was looking at my single source charger, the 'wall wart' says its 24v output. and with just a few resistors inside and a diode or 2., in theory, cant i just bypass those resistors and connect the wart directly to the battery pack without modification? (i wanna put a meter on the output to verifiy voltage yet, but theres nothing i see in there thats going to UP the voltage)im going to run the charger off a timer to make it turn off after an hour so i dont forget to unplug and burn down my shed, LOL. - xbeerd
Great write up... I just got all of the parts you listed and notice that the plastic battery holder is a little too wide for the original shell? I 'm hoping that I can make it fit even if I have to remove some plastic somewhere..?thanks!
Passive CDV-700 speaker
Great instructions for this awesome upgrade. I found the diodes and battery holders on Amazon. I made the first battery pack without the holders but will change it over later. I just finished adding the diodes to my second charger. Everything is working as described. Thanks again.
i was looking at 50v 1A Rectifier diodes, are those sufficient?
Homemade SBM-20 gamma detector array
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