Baofeng DM1701 charger -> USB C option... (inspirational post)

[EI8IHB]

Spot the differences

usb C charger.JPG (38.06 KiB) Viewed 786 times

the charging status is visible (blue charged, red - in charge)

usb c charger 2.JPG (31.02 KiB) Viewed 786 times

In need to be able to charge my batteries with a battery pack or in my car, with this mod I'm able now to do it easily.
I'm aware that someone modified the battery pack with a similar option, but IMHO this option is not very practical, as it need to be applied on all BP's.

Hint: the "T" contact is not connected , so there's no working thermal management, despite the presence of this contact

Now let's work for the compact version

[VK3KYY]

See viewtopic.php?t=2887

[EI8IHB]

Yep, surely not invented hot water

but there's ONE big difference there, the solution above is backwards compatible.
What does it means?
Both power supplies are available (one at time...), so the cradle can be used as usual, or with the USB C when needed, as the circuit in use is protected by a diode for reverse current (make sure the board have it, to prevent problems)
But
WHY not only the USB C?

The problem with the USB C Li-ion charger is the noise.
When in use, it makes a lot of QRM, and this is noticeable also when the radio is on.
On DMR this doesn't creates big issues when you work with mmdvm's, but it can be a problem in different situations.

So, depending on the board, as the switching circuit works from few kHz up to MHz, this can affect then sensible devices on close proximity.
To prevent that, the pcb should be shielded appropriately, but there's not a lot of space inside the DM1701's cradle to do it properly unfortunately.

That solution then remains "an emergency" one, keeping the main wall wart supply the preferred source of power.

[VK3KYY]

I don't understand.

Is the 5V from the USB socket being boosted to 10V and then applied to the input of the existing charger circuit.

I didn't notice any specific QRM problem with using the USB or TP5100 charger modification to various charger bases, and I don't remember anyone posting that there were problems with these modifications.

However, often people have a lot of local QRM, and may not notice some small additional QRM being created by the charger electronics

Normally I find the AC mains 'adaptors' can themselves casue some QRM, and I threw away several 10V AC mains PSU / Adaptors because of the QRM

[EI8IHB]

The USB pcb is a 2s charge controller, placed in parallel on the existing 10V charger (there's a diode to separate and prevent back current on the added pcb), with independent led for charge status (on the side of the cradle)
So both are working (but obviously not to be used at the same time )
As the USB pcb is a switching controller, it's quite "normal" to have some noise then, and the original controller instead is linear, so here's why the heat generation and the need to cool it properly.

With the other mod for the cooling (viewtopic.php?f=25&t=5102 ), the charger is working ok on 10V. It seems also the charging time seems to be improved, possibly due to the fact the chip doesn't go in protection.
So this explain also why many are not satisfied with the charging times... chip not cooled correctly and then low current/protection mode, and biblical times to complete the task.
When in use the USB charger is just warming up a little bit, so no probs there, no need to cool it with an heat sink on the chip.



ps...regarding the noise
viewtopic.php?f=8&t=564&start=40

[VK3KYY]

OK

So you wired them in parallel.

Did you check whether there was an current flowing backwards into the existing charge circuit ?

I wouid be concerned that simply wiring in parallel may damage the existing circuit and also affect the operation of the USB -> 2S charger unit, even if you didn't measure any current flowing backwards.

I'm also not sure why you need to retain the existing charge circuit? Does it charge at a higher rate then your USB -> 2S. ?
What current does your USB->2S charger put into the batteries?

In my case, I was cautious and only used USB -> 2S which takes 1A from USB, because I still have some USB 'chargers' including in my car, which only support 1A.

Of course the newer USB chargers arer all 2A+ , but I didn't want to limit where I could use my USB version.

BTW.

I also found that some of the 10V PSU for my radios created a lot of QRM so I threw those PSU's away, as some PSUs were produced much less QRM than others.
The same applies to USB 'chargers'.

[EI8IHB]

Backcurrent?
not an issue, both supplies modules are protected against that.
On the USB 2S Li-ion there's a protection diode, and for the OEM charging controller, is protected too, as the battery can flow back current when placed on the cradle, when not powered up.(back contacts are "live")

Interesting to note the OEM is providing around 350mA when the radio is powered up and charging the battery, but if not properly cooled, it will overheat (and go in protection/reducing the current).

For the USB module, good to know that
2-Cell(2S) 8.4V version:
Input voltage: DC 3 min to 6V max (recommended DC 3.7V to 5V)
Input current: 1A (1A Version); 2A (2A Version); 4A (4A Version)
Charging voltage: 8.4V
Charging current: 0.55A(1A Version);1.1A(2A Version);2.2A(4A Version)

Considering that a Li-ion usually can be charged at 1C max, better then to stay below to prevent overheating issues and battery ageing.
BTW, to maximize compatibility between available chargers, battery packs and portable/trekking solar panel, the 1A version is the best one, as it will charge then at 0.25C approx.

Then WHY both chargers?
Simple, the first mod has been the OEM chip cooling improvement, then on one of the cradle I've installed the USB module.
Maximum compatibility, to be used indoors or outdoor (vehicle) without problems, doing a practical and functional mod without altering completely the device.
And if one fails...the other is there in backup (yep, have 220V in my vehicle, but more easy for such applications to use USB )