Swapping out a NiMh for a LiPo?

[eccerr0r]

Re: Swapping out a NiMh for a LiPo?

Not sure if I myself is actually using it in public is a problem, unless someone thinks I might be a target, but wouldn't it have already done what it was going to do?

Now, leaving it out for someone else to use, however, ...

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

Paper clips, shoe string, and of course, duct tape!
(though a 3d printer might be involved...)

Now THAT would be interesting to see!

I'm currently in 3D printer hell ... I decided to try using ABS and after doing a lot of reading up on how to print with ABS, It seems that keeping the print warm while it's printing is the big deal with ABS. I don't have a heated print bed on this printer, so I decided to make a little modification...

I had already modified the printer with a 12 vold regulator that I placed inline with the extruder fans power source, because the fan was way too loud and I discovered it was being fed 19 volts, so I cut it down to 12 and have been running it like that for the last almost two years without any issue.

Well ... in order to keep the ABS print warm while printing and since I don't have a heated bed, I decided to step up my fan mod a notch. I implemented an LM317 with a POT for R2 so that I could turn the fan way down so that it doesn't cool the print while it's printing. Well, I turned the fan off completely and started a small 45 minute print with a new spool of ABS... and I watched the first couple of layers go down and they were fine so I walked away until the job was done and when I came back, the first few layers were still there ... but nothing else.

The ABS had snapped above the extruder feed hole and I couldn't clear it out ... so I had to take the whole assembly apart and what I discovered wasn't pretty...

I THOUGHT that what I was looking at was the melting of the housing assembly itself with the abs feed stuck in the middle of the melted plastic ... but looking closer, I realized that I was looking at the ABS itself. It had pooled up just above the heat blocks heat sync in a perfect circle. With some pliers, I was able to break it loose ...



What I thought was really weird about this, is that the fan blows air just under the extruder nozzle which is nowhere near the heat sync for the heater block ... but somehow, obviously, it keeps that heat sync cool enough so that it won't melt material above it ... lol

I also noticed that the wires coming from the thermocouple had somehow broken off mid-way to the circuit board. So I ordered a new one. I also tested the heater element with a power supply and it's heating just fine, so I think once I get the new thermocouple I'll be back in business with this printer.

However, I ordered a new printer that has a larger build plate - heated of course and I'll just use it to do my ABS printing. This Flashforge Finder is a great printer, but its build surface has been too small for many projects and I don't think it's very good for ABS.

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

BTW I charged it with the original charger meant for NiCd up to about 4V and stopped, it charged!

Now THAT's interesting ... Though I guess that makes sense since the charger is only going to feed it current until the voltage reaches the level it expects. possibly with some heat detection as well as is common with NiMh battery chargers. I always thought it was kinda funny that a charger would be configured to give enough current to a battery that it became common practice to include a heat sensor to cut back on the current feed if the battery gets too warm ... but I guess it's fine since that's how it seems to be done in almost all NiMh chargers.

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

The duty cycle for an emergency light is way different from a cordless phone. Typically there are three discharges these batteries experience; self discharge, testing and loss of mains power.

How often you discharge/test the emergency lights, should be set by assessing the consequences of a fixture failure between the tests (risk management), not to optimize battery life. Typically somewhere between quarterly and monthly is normal.

The code here is that emergency lights shall be connected to the local general light circuit, so a loss of power to general lighting, the emergency lights switches to battery power. As you said, if connected directly to the same general light circuit, it would be somewhat cumbersome to test them. Some type of fixtures are easy to unhook from the socket so one can just unhook and lay them to the side and time them. As stj says, if planned before install, it is better to branch of a separate cable from the general lighting where one could install a test switch (not generally available), and perhaps use a relay for a little more elegant design. Otherwise, as you says, you would be relegated to trip the fuse. Some types of fixtures are self testing; they run down their batteries once a month, and flashes a diode if there is a failure.

The three last complete building emergency light refits I've managed, we installed automatic central monitoring and testing. The local building technician will get a warning with a fixture address after each test if a fixture fail, without running around in the building. His job besides this, would be to check the fixtures for if anybody has physically damaged them.

I already designed a little project using an ATTiny 85 (since I have 10 of them), a 5 volt activated solid-state relay, and an RTC with an I2C interface. I'll have it discharge the batteries by cutting the main AC power to the circuit at 12:00 noon either once a month or once a quarter, I'm not sure yet... but in order to not cut power to the Arduino circuit itself, I'm going to use this 120V ac to 5 volt DC buck converter so that the Arduino doesn't kill itself when it cuts power to the main circuit.

And instead of hassling the part of trying to figure out if the battery has fully drained or not, I'm just going to leave it disconnected for 4 or 5 hours because at least I know they will be drained by that time. And by choosing to cut power at 12 noon, I know I won't be killing the battery when it's dark outside.

[ChaosLegionnaire]

Re: Swapping out a NiMh for a LiPo?

And instead of hassling the part of trying to figure out if the battery has fully drained or not, I'm just going to leave it disconnected for 4 or 5 hours because at least I know they will be drained by that time. And by choosing to cut power at 12 noon, I know I won't be killing the battery when it's dark outside.

just one issue with that... if u cut power at noon, by the time u leave it aside and disconnected for 4-5 hours like u said, its going to be 4-5pm already then. in winter, its already dark by that time. how are u going to charge the battery fully then before it gets dark? the math and practicality of that doesnt seem to sound right or work out right to me...

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

just one issue with that... if u cut power at noon, by the time u leave it aside and disconnected for 4-5 hours like u said, its going to be 4-5pm already then. in winter, its already dark by that time. how are u going to charge the battery fully then before it gets dark? the math and practicality of that doesnt seem to sound right or work out right to me...

I could change the time to 8 am... I mean ... it's not like this is an industrial application. I've got the light installed in the hallway next to the smoke alarm. Sure came in handy twice this week so far ... for some reason, Edison can't seem to keep the power on in this neck of the woods ... guess we're the red-headed stepchildren of the grid out here.

[stj]

Re: Swapping out a NiMh for a LiPo?

have you seen the conversion kits?
20w DC invertors
https://www.tlc-direct.co.uk/Main_In...its/index.html

[sam_sam_sam]

Re: Swapping out a NiMh for a LiPo?

Why put a photo diode and write the program that while the sun is out playing you are charging the battery and then while the sun is not out playing it stops charging this does two things one you do not have to set a time clock and when the season change you do not have to rest the time clock

I use to have this setup on my pool pump timer and it worked very well

[stj]

Re: Swapping out a NiMh for a LiPo?

why do you need a photodiode when you can just monitor the solar cell output?

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

have you seen the conversion kits?
20w DC invertors
https://www.tlc-direct.co.uk/Main_In...its/index.html

OK, that's pretty awesome! It looks like a beefy battery too ... one thing though, it says that it will not work on units that have resistive drivers. How do I find out if mine has that? And what is it?

[stj]

Re: Swapping out a NiMh for a LiPo?

go watch big clive.
switching psu will run off dc because it starts with a rectifier,
capacitive dropper needs ac.

[eccerr0r]

Re: Swapping out a NiMh for a LiPo?

Damn. Was hoping to be pleasantly surprised, but a diode dropper shunt amplifier was insufficient to prevent overcharge.

Guess I'll need to locate custom zeners, or tune a TL431...

[sam_sam_sam]

Re: Swapping out a NiMh for a LiPo?

Guess I'll need to locate custom zeners, or tune a TL431...

If you tune TL431 please post your results

Thanks

[eccerr0r]

Re: Swapping out a NiMh for a LiPo?

I'll need to see if I have one somewhere...ugh...

... and nope, dont think this open loop common emitter shunt regulator is accurate enough... need to have full control loop

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

An update on this thread ...

One of the circuit boards I ordered recently was the one to do this project... Though I screwed up on the schematic and cross-connected the input to the relay so I had to cut traces and jumper across to make it right.

Also, R5 ended up not being needed at all ... it was choking the voltage at the relay input and I learned a very important lesson in this venture ... SURFACE MOUNT COMPONENTS CAN REALLY SUCK SOMETIMES!

C1 is so friggin tiny, that I can't even pick it up with my fingers ... I must have lost 10 of them just trying to get one on the board ... I ended up just using the oven with some solder paste which actually worked out well.

Here are some pics ...








And this is the re-design ... got rid of that damn microcap and put a real cap in there ... fixed the leads to the relay, fattened up the traces a bit ... dumped R5 and its cap and bigger resistors cause they're easier to work with also added the ability to connect to serial on the ATTINY ...



OH, and those connector blocks ... are REALLY REALLY NICE ... they have some kind of mechanism in them so that when you pull on the wire, it somehow gets tighter ... I tried with all my might to rip the wire out once it was latched in there and it wasn't budging AT ALL. I have so many of them because of the required minimums but I think I had to purchase 50 of them at like 2 cents each or something ridiculous like that .... if anyone is interested in trying them, PM me your mailing address, and I'll send you a few ... they're pretty slick.

[stj]

Re: Swapping out a NiMh for a LiPo?

you used an smd electrolytic - you terrorist!!!!

[sam_sam_sam]

Re: Swapping out a NiMh for a LiPo?

One comment I have is that what I have read about doing circuit traces is that should have rounded curves and not square edges that come to a point

For the life of I can not remember the exact reason for this is

[Agent24]

Re: Swapping out a NiMh for a LiPo?

One comment I have is that what I have read about doing circuit traces is that should have rounded curves and not square edges that come to a point

For the life of I can not remember the exact reason for this is

Sharp inner corners (45 degrees and below) can create an "acid trap" that could cause undercutting of the trace during etching.

Also, sharp angles are no good for high frequency signals, so traces that must carry them are usually curved around corners instead of angled.

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

you used an smd electrolytic - you terrorist!!!!

Not in version 2.0!

[EasyGoing1]

Re: Swapping out a NiMh for a LiPo?

One comment I have is that what I have read about doing circuit traces is that should have rounded curves and not square edges that come to a point

For the life of I can not remember the exact reason for this is

Yes, I've seen that stated before too ... but until someone can tell me WHY this should be the case ... then I call bullshit on it.

Certainly, in high-frequency circuits, trace layout could mean the difference between success and failure... but in raw DC switching applications? BAH!