Hello folks,

I'm building an automated charger that will charge up to 8 (inspire batteries or remotes).
It is based on an arduino that controls relays and monitors the voltage, current and power taken by the battery been charged.
Note this is a sequential charger and uses the standard 100W brick charger. The idea is that the arduino can detect when the battery is fully charged (and switchs off by  itlself) and move to next battery untill they are all charged.
So I wanted to check what voltage, current and power changes are detected when the battery being charged turn itself off.  I added an SD card module so I can log V,A and W for the whole charging time and here are the results:

With the regular 100W brick PSU:
The TB48 is charging at constant current ~4.3A for about 48min (I guess it depends on the starting charge\battery health). My PSU puts out up to 110W apparently.
The remaining time the current decreases gradually for anoter 50min or so and then the battery reaching full charge (by its internal logic) and it turns itself off.
At turn off the PSU voltage jumps up by 40mV (no more load), the current drops to 0 from ~250mA, and the power drops from ~6.5W to zero. So it is extremely easy to detect when the battery turning off just from the current.

Anyway I'm attaching the graphs, and maybe I'll let you guys know when the whole thing is finished.
Just to give some idea on cost, the arduino nano is about $2.50, the 1.4 TFT display is ~$4.00, the SD card module is ~$1.00. An 8 relays board is ~$7.50 and a parallel charger Inspire 1 PCB (That I modify to make each battery independent) is ~$6.00, the TI INA226 current monitor (got it as free sample but it costs a couple of bucks). BTW, I think I'll keep the SD logging in the final design as it is nice to see how different batteries charge. The way I have it now can log ~8.5 measures per second (Way overkill :-)  I know). The csv file I generate is about 2MB per battery onto a 1GB SD card :-).

PaulKerry Posted at 2015-11-26 21:22
These are very useful data, Vincenzo. Would you be so kind as to repost these graphs in my "battery  ...

Hi, Vincenzomiceli
Thank you for your sharing . I've learnt a lot from the thread !

PaulKerry Posted at 2015-11-26 05:22
These are very useful data, Vincenzo. Would you be so kind as to repost these graphs in my "battery  ...

Sure Paul, I'll post the graphs on the other thread. If you need one built let me know. I am ready for a simple one that only charges one battery and logs the data. Haven't finished the code for sequentially charging multiple batteries...

Enzo

Here is the same curve for a TB47. Having current and time allows me to calculate the mAh being pushed to the battery and compare to the capacity.

For example, for the TB48 took in 4675mAh 20% less than nominal capacity.
For the TB47, it took in 3848mAh 15% less than full capacity.

Unfortunately I didn't record the capacity left in them before charge so I can't tell how efficient is the charging process. I will next time.

Vincenzo

Hello Vince,

Thank you for sharing and taking the time to chart the batteries. I wonder if the simple Kill-O-watt meter that allows you to check the current and voltage draw from devices would tell us anything?  plugs into any wall outlet and then you plug the device into the meter.

I have been using the Smart Power System for awhile now and have not used the stock battery power supply.

Keep up the good work
Rich

i built the very same thing for the P3 3 months ago,  worked well, i also added storage charge option as well

Was discussed on RCGroups,

RichJ53 Posted at 2015-12-7 03:48
Hello Vince,

Thank you for sharing and taking the time to chart the batteries. I wonder if the simp ...

Thanks Rich, the plug power meter may possibly give a current and a power value but those are obviously totals that include the switching power supply inefficiency. Also for my purpose, anything that doesn't log the readings is not useful as I'm not going to stare at the display manually tracking it :-)

Vincenzo

Mad_Angler1 Posted at 2015-12-7 07:56
i built the very same thing for the P3 3 months ago,  worked well, i also added storage charge optio ...

Do you have a link?

vincenzomiceli Posted at 2016-1-12 13:13
Thanks Rich, the plug power meter may possibly give a current and a power value but those are obvi ...

yah I was thinking it would be some useful information but you are correct .. no one wants to watch the screen forever

Rich