I use two Tadiran SL-2790 battery in 2G mode with R412 Rev 3 Sara SFF.
In my first probe I use the old resoldered lipo connector and connect the two serial soldered battery to te JST connector. But When start the modem, during the AT+CSQ write “timed out” and after some message the module rebooted.
The code is work perfectly with Li-Ion battery on same JST connector.
So My first thought: the pulse is none enought for a 2G mode.
My first question : The first thought is appropriate?
My secound q.: Wich is the best connector for the TADIRAN battery? I see some other Battery port and 3.3 Volt on the board. Can I us another for a better solution or all other bettery port same as the JST, and the 3.3 cant usable for TADIRAN BATTERY?
The Battery parameters. (But The pulse is high…)
SL-2790 Size: DD
Available Terminations Catalogue No.
SL-2790/S Standard 11 2 17901 00
SL-2790/T Tags 11 2 17902 00
System Lithium Thionyl Chloride
Nominal voltage 3.6 V
Nominal capacity 35 Ah
Nominal current 10 mA
Max. continuous discharge current 450 mA
Pulse current capability 1000 mA
Anode surface area 90 cm2
Lithium content 10 g
Weight 190 g
Volume 105 cm3
Temperature range −55°C … +85°
A quick glance at the datasheet tell me they’re very poor at maintaining their supply voltage under higher loads. Take a look at the third graph and at 300mA, I expect things to be much worse when it’s a short spike. The batteries having a nominal voltage of 3.6V also doesn’t leave much leeway to drop before hitting critical levels.
Neither really. The 3V3 line is not designed to support 3.6V and the BATTERY line is not intended to be used with batteries that typically operate at 3.6V. Chargeable or not is unimportant as long as you don’t try to charge them.
A quick glance at the schematics also tells me that not connecting anything to the BATTERY line will result in an unpowered R412M (see schematics).
You have a couple options, but none are great. One would be to add a large cap to the battery, but this will cost you in self-discharge and BOM. I’d say look for a more… proper battery for this application. Or don’t use 2G…
To make sure of this I recommend you monitor the voltage supplied to the R412M and look for the dip with an oscilloscope (or other tools if they’re precise enough).
Peak current for 2G is around 2A, you will need a battery that will handle this peak current or use a super capacitor like CAPXX.
You’re definitely right, but 2A is very rare and >1A is typically very short. The worst spikes are caught by the internal energy-holding components (Cap/Ind). If the battery looks “good enough” in the datasheet you’ll just need to test it. Theory and practice don’t often align.
But yes, getting devices that are rated to deliver that peak current are likely to do the job.
Remember, the higher the nominal voltage (but no higher than 4.5V) the more leeway they have to drop voltage. 3.6 to 3 is only 0.6V, 4.2 to 3 is 1.2V.
Small note, my replies assume this is a hobby project or a pilot to test for feasibility. If you want something more serious you may want to contact us directly. Primarily hardware.
Thank you for your reply.
For the time being we are using the 2G network out of necessity.
I hope the NB IoT network will be available soon.
Until then I’ll keep trying.