Electronics > Beginners
Switching from Nicad battery to Lipo: Am I doing this right?
Nohippychicks:
BLUF: I don't know how to troubleshoot a generic setup of Lipo cell ->charge controller-> boost converter->12v load and I'd like some help.
Long version:
I recently got 'hold of an old Yaesu UHF transceiver. The battery is labeled as 12V, 500mAH and hasn't been charged in probably 30 years.
Thinking this would be a pretty fun little project to get working again, I tried to do a little homework online but didn't come up with exactly what I needed, so I went off past experience of a few other project where I simply powered a Raspberry Pi with a lithium cell and a charge controller; I figured I had all the know-how I needed and ordered up some parts.
I got a (All generic) 3.7V, 4K mAH cell and a 5 pack of cheap TP4056 based charge controllers, as well as found a boost converter that I had left over from another project.
Everything arrived and I set about pulling out the old nicad cells and fitting the new bits into the battery housing. After charging up the battery and loosely fitting everything in place, I adjusted the boost converter to 12.8v and the radio came to life. Project done! Only not so much.
Seemingly randomly, the radio would shut down. A voltage check across the battery terminals shows 1.1v. Following back, I get 1.1v at the output of the boost converter, 1.1 at the input of the boost converter, 1.1V at the output of the charge circuit and 4.x volts at the input of the charge circuit...4.xx volts at the output of the Lipo.
This 1.1V output is intermittent enough that I can't figure out what the problem is. Some times, I can remove and replace lipo cell and it's fixed for a while but some times I can measure 12v at the battery terminals but when I turn on the radio, I get a flash of life then nothing...and I'm back to measuring 1.1v at the terminals.
Sometimes I can get the radio to turn on, where I just leave it for a few hours and everything is great, 'till I turn it off, then back on and back to 1.1v. Sometimes turning off and on works as it should. Sometimes, if I hook the charge circuit up to USB, as if I were charging it, it pops back up to 12V and may stay there for a while or it may not.
Thinking it was the charge circuit because I got the cheapest ones I could, I swapped it with a new one from the same order (The only ones I have)...same deal...and a 3rd one, all with the same result.
Since I get the 1.1v at the output of the charge circuits, I'm pretty sure that's the problem, but where is the solution?
Do I just buy a more expensive, and presumably better quality, one from a place like Adafruit? Is there more troubleshooting that needs to be done? As cheap as the chargers I've bought are, I'd hate to think that 3 (so far) out of 5 could be bad out of the box. Maybe there's something more obvious that I'm missing. I can post pictures of it all, but with the intermittent 12V I'm reasonably certain that everything is soldered up properly.
TERRA Operative:
How much current is the radio pulling from the battery?
Maybe the overrcurrent protection is kicking in in either the boost converter or the battery BMS.
Is the boost converter getting hot? They tend to use fake silicon, so replacing the boost chip with a genuine item and sticking a small heatsink on can go a long way.
borghese:
What kind of battery do you have? If these are Chinese, they are likely to have only fractions of nominal capacity. A better way would be to use high capacity NiCd batteries; these are much easier to recharge, better tolerate charging abuses.
Nohippychicks:
--- Quote from: TERRA Operative on July 25, 2018, 06:35:18 am ---How much current is the radio pulling from the battery?
Maybe the overrcurrent protection is kicking ...
Is the boost converter getting hot? They tend to use fake silicon...
--- End quote ---
I just took a reading of .065 amps when I could finally get the radio to turn on for a few seconds. I tried to hit the transmit button to see what it would pull then, but it shut down again and I haven't gotten it back up and going, but I'll update if I'm able to.
Does that fake silicone also go for the little charge controllers? Maybe it's worth it to just buy a decent quality one instead of fooling with the cheapest ones I could have gotten...which is what I suspect. Even more so after this.
The boost converter isn't getting hot at any point that I've found, but when I FIRST charged the new battery, the charge controller got uncomfortably hot. I figured that it was because it was rated to charge at up to 1A and with a partly charged battery/cell. I put a little heat sink on the chip, but eventually swapped that unit for a new one...then another new one.
I couldnt find a datasheet for the exact charge controller or battery protection that I have because of how generic I went, but at such a little draw, it doesn't seem like it should be tripping any sort of protection...but again, "Generic," so maybe?
--- Quote from: borghese on July 25, 2018, 08:20:41 am ---What kind of battery do you have? If these are Chinese...
--- End quote ---
I do have a generic battery, but even if it's half of the rated capacity, it's still 4X what was there (500mAH). Do you still think it's better to go back in with Nicads? I don't have what it takes to string together my own pack of cells. I've found a service that would rebuild them for about $75, which is not really worth it to me, so I was trying to stay cheap. Even if I go with a name brand lithium cell to try to avoid poorly labeled products, it seems like it'd be better, but I'm not sure. If the consensus here is "Go back Nicad," I'll keep looking into them and get it done "Some day."
Thanks for the suggestions! I'll wait to hear back about the lipo/nicad and go ahead and order some non-generic parts tomorrow.
thm_w:
The capacity of the lithium cell is probably 1500-2000mAh at 3.8V, so ~8Wh. If you originally had 10 NiCd cells that were 500mAh, at 12V, that would be 6Wh. So the difference is not so large. But you could always parallel a few 18650's if you want greater capacity.
Is the circuit something like this:
https://www.aliexpress.com/item/5PCS-Micro-USB-5V-1A-18650-Lithium-Battery-Charger-Board-With-Protection-Module/32647794396.html
DW01A: http://cxem.net/master/files/97_DW01A-DS-11_EN.pdf with overcurrent 150mV
If the FET is 8205A: https://www.maritex.com.pl/product/attachment/91261/8205A.pdf
rds on about 25mOhm*2
So overcurrent trip point is roughly 3A. There is a chance the boost converter is pulling a lot for a short time, meaning the charge board shuts off (could be why you see 1V).
Its normal for the TP4056 to get hot as it is linear charge, so its dropping 5V - Vbat across.
Do you have a bench PSU you can test at 12V to check if that voltage is high enough, and what peak draw is?
Navigation
[0] Message Index
[#] Next page
Go to full version