BCD436HP/BCD536HP: Trickle Charger Mod

[Flywheel17]

Jon - with this mod - its it ONLY charging with the scanner powered on and plugged in or is it charging powered off as well (and NOT in charge mode?

Is it ok with the batteries under charge all the time?

Thanks!

 

[jonwienke]

It charges when the scanner is plugged in, regardless of whether the scanner is turned on or off. At a full charge, the charging rate is low enough that the batteries are not damaged even though they are being constantly charged. The same charging principle is used as in cordless phones and other devices; keep the trickle charge current under .05C and the battery will not be damaged even if charged continuously. The idea is to keep the batteries fully charged while the scanner is on USB power, without damaging them.

 

[I_am_Alpha1]

WOW! That simple, yet Uniden didn't include it.

I've ordered the 22 ohm 1/4 watt resistors...I found some switching diodes in a junk drawer...radio shack # 276-1122 (1N914/1N4148). Do you think they will work for this? Thanx...

 

[garys]

They included it in non US spec units, but not US spec units. Thank CA for that.

WOW! That simple, yet Uniden didn't include it.

I've ordered the 22 ohm 1/4 watt resistors...I found some switching diodes in a junk drawer...radio shack # 276-1122 (1N914/1N4148). Do you think they will work for this? Thanx...

 

[jonwienke]

.I found some switching diodes in a junk drawer...radio shack # 276-1122 (1N914/1N4148). Do you think they will work for this?

Sort of. They have a higher forward voltage drop than the diodes I'm using, which means the batteries may not fully charge, and will charge significantly slower.

 

[Rred]

Flywheel-
The general rule of thumb, as stated by a number of battery makers, is that you can charge commercial NiCd or NiMh cells at 1/10th "C" forever without harming them. With the oldest cheapest cells being NiCd AA cells rated at 600mA, that means a 60mA charging current would be safe "forever" in pretty much anything. With higher power cells (2000mA being easy to find in consumer cells retail) you're at more like 1/30th "C" so what Jon is doing is not only safe, but it would actually take something like three days to fully recharge a set of cells!
There's no easy compromise between 'safe' and "fast" unless you get into "smart" chargers and way more complications. That's why so many consumer products still are designed around an "overnight" charge, charging at about 1/10th "C" plus a couple of hours for inefficiences, with whatever they are designed around.
Better chargers, faster chargers, lithium batteries, all that adds costs.

 

[jonwienke]

My mod charges at approximately 1/20C, depending on battery capacity.

 

[I_am_Alpha1]

I have 2300 NiMH in my 436...should I change the resistor so they charge in under a week? I ordered the same diode...just read about the forward voltage loss on switching. Thanx again...amazing stuff you're doing.

 

[jonwienke]

That's what I run in mine, and with the diode and resistor I specified, they charge fully in about 36 hours.

 

[I_am_Alpha1]

Reverend Jon has spoken and Ye shall follow his wisdom. Thanx again Jon.

 

[jonwienke]

https://www.ebay.com/itm/USB-Lithiu...4-2V-Boost-Step-Up-5V-9V-12V-24V/322562445571

This board has a USB Li-ion battery charger, but it also has a regulated boost converter for the output, which you can adjust from 4.3-27V. Part of the reason using Li-ion batteries didn't extend battery life much in my previous test was because the scanner shuts down at 3.1V, which is before the battery is completely discharged. This board will allow the Li-ion battery to discharge completely before the output drops below 3.1V, which should extend runtime significantly. Stay tuned...

 

[ur20v]

I wonder, is this difference (charging while operating) between US and ROW versions hardware or firmware based?

 

[tumegpc]

I'm going to order the parts and mod my 436 and see what happens. If all goes well, I will offer it as a $5 add-on option when I do a GPS mod.

Jonwienke , you are killin it with these mods ! What about doing a LED mod for the display on the 436/536?
Something like mancow did with his 536HP. https://forums.radioreference.com/uniden-tavern/334103-got-tired-dim-pale-blue-bcd536hp-display.html

 

[jonwienke]

I wonder, is this difference (charging while operating) between US and ROW versions hardware or firmware based?

Possibly just firmware, given that the firmware seems to control when charging starts and stops. The only possible hardware difference is that the non-US hardware may support charging at a slower rate than US hardware when battery voltage rises enough to indicate the batteries are mostly charged.

 

[jonwienke]

Jonwienke , you are killin it with these mods ! What about doing a LED mod for the display on the 436/536?
Something like mancow did with his 536HP. https://forums.radioreference.com/uniden-tavern/334103-got-tired-dim-pale-blue-bcd536hp-display.html

My first thought would be that if the display LEDs are failing, send the scanner to Uniden to get the board replaced. That will fix RTC issues, and probablt the C1 thing as well.

If that's been done,I'd have to go back and look at how the LCD is attached to the board. It would need to be removed to access the backlight LEDs for replacement. The next step would be to figure out the current output by the driver circuit, and find some compatible SMDs.

 

[Rred]

Jon-
When you said that board allowed a lithium battery to discharge completely, that sounded odd, since discharging one of those "completely" or simply to ~2V can permanently damage it and eventually lead to the pyrotechnic department. Hopefully it will cut off before the battery can get into that range?

 

[jonwienke]

Complete as in delivering the complete rated capacity of the battery, not discharging it until it fries.

 

[jonwienke]

So I did some tests with some 800mAH 14500 Li-ion batteries. 3 of them in parallel is roughly equivalent to 3 NiMH cells in series. I did a comparison of battery life, and the NiMH cells lasted about 8.5 hours, and the Li-ion cells lasted about 9.75 hours. The performance benefit is there, but probably not worth the hassle of coverting the scanner to use them.

I've changed my mind about this. Either I didn't have the Li-ion cells fully charged in the previous test, or else they needed a few charge/discharge cycles to reach full capacity. Also, the charger board was also generating a little RFI that was making the 436 low voltage cutoff trip multiple times, starting at about 3.5V.

For this test, I put a 0.1μF capacitor across the output terminals of the charger board, and had the battery plugged in to the charger board overnight before starting the test. With the display backlight off, volume set to 8, the same favorite list as the previous tests, battery saver turned on, and GPS turned off, I got a run time of 13:35:34 from the time I unplugged USB to getting the low battery warning. I was able to plug in to USB power before the scanner shut down.

3100mV is a decent setting for low voltage. The cells are over 99% depleted at that point.

I made a cutout in the case so that the USB jack on the charger board can be used. This has the advantage of allowing the charge status lights on the board to be visible, and also allows you to plug in to USB power without any annoying menu prompts.

https://1drv.ms/u/s!ApJIS-l4xqPtguo5H7IjxIZbZ-eZng

To get the board to fit properly, I created a template and milled out pockets for the chips and other components on the board, as well as the USB jack. Here's a photo of the board snugly fit into a piece of scrap plexiglas I used as a test before hacking the scanner case.

https://1drv.ms/u/s!ApJIS-l4xqPtguofCT5ANZPFQBmHug

The pockets for the board and components had to be milled from the inside, but the cutout for the USB plug had to be milled from the outside. So I had to use the middle-left case screw hole as a zero reference so I cut in the same place from both sides.

The cells I'm using are 800mAH Tenergy Li-ion 14500s with solder tabs:
https://www.amazon.com/gp/product/B003EWA5Z6/

I removed the battery terminals on the scanner front circuit board. I used 3-pin 1.25mm JST connectors to connect the battery to the charger board, and the charger board to the front circuit board.

 

[Rred]

JON-
FWIW, I haven't used Tenergy LiOn cells, but have found their NiMh cells just didn't hold up over time. Not in the competition against Eneloop or Panasonic industrial at all.
Given that some of the prime names make 3000 mA NiMh AA cells...it would take more than an extra 100 mA to make me want a flammable replacement.
FWIW.

 

[jonwienke]

Using the same testing methodology, the most life I've gotten out of any NiMh batteries was about 9 hours. Li-ion and NiMh are sufficiently different that they are probably made in different plants, even with the same brand name. There are other cells with similar specs, but most have no recognizable brand name.

Lithium batteries have become the most common battery type for several reasons. They are easier to charge intelligently, have less self-discharge, are lighter, and have greater energy density than any other battery type. The safety issues have been mostly resolved.

I'm not familiar with any 3000mAH rated NiMH batteries that perform anywhere near their specs. Link?