ISDT FD100 Smart Discharger

[Scott Page]

I received my Smart Discharger today and I'm pretty excited about it. I've found over the years that my batteries life is MUCH improved if I religiously discharge all LIPO batteries after returning from the field. Of course - this is a bit of a hassle - but for the cost of batteries... it's worth it. I'm currently wondering about putting a parallel board on the discharger - but that's a topic for another day.

While discharging the first battery today I started wondering -- how many mAh does this battery have between charged and nominal voltage? What it the current of discharge REALLY. Then... how could I monitor this remotely. When I had an epiphany (sort of).

All I needed to do was to set up a Rx with an SP-FLVS and a SP-40A and I could use the transmitters telemetry display to remotely monitor the progress -- find out the capacity of the Battery, and even log the progress over time if I wanted.
One thing I noticed on the first run was the current draw is ramped down as the battery get's closer to nominal voltage. The other thing I notice was the old 2200mAh I used for the test didn't have even half the capacity on the label. (but that battery is several years old .. but it's nice to know).

 

[Skye]

Great little device, and I do use my two with parallel isdt boards.

 

[RCdiy]

Cool The rampaging down makes sense to account for internal resistance voltage drop.

When connecting batteries in parallel remember to connect the discharge plugs first and then the balance. This way if there is a large voltage difference the thicker wires carry the current.

 

[RCdiy]

Does it balance?

 

[RCdiy]

Storage voltage 3.8v is a bit above the 50% voltage 3.7v so the mAh discharged is not 50%.

 

[Skye]

Does it balance?

Nope.

 

[Skye]

Storage voltage 3.8v is a bit above the 50% voltage 3.7v so the mAh discharged is not 50%.

It can be adjusted.

 

[Skye]

Cool The rampaging down makes sense to account for internal resistance voltage drop.

When connecting batteries in parallel remember to connect the discharge plugs first and then the balance. This way if there is a large voltage difference the thicker wires carry the current.

No need, it does NOT balance.

 

[Scott Page]

Does it balance?

It does not balance, however you could use a passive balancer such as SDT BattGo BG-8S Smart Battery Checker connected to the balance lead for this.

When I first saw this and noticed it did not balance I was put off. Turns out that at the low current load (<=6A) for discharging differences in cells internal resistance doesn't come into play -- and then I balance them when I charge them.

 

[Skye]

Same for me. Great device.

 

[Wayne]

Good idea on the monitoring with the radio.

Glad she is working out well for you. To be fully honest here, Scott's first unit had an issue, it would stop working after a little bit of time so we swapped it out for him. We opened it up, but not sure what the issue is with it. Possibly a underperforming part. Will be going back to ISDT to play with. We have almost no issues with ISDT products, they do a very good job of QC and proper design to start with.

 

[RCdiy]

Scott
What is the max discharge watts?
Do you recommend buying it now that you’ve used it for a while?

 

[Scott Page]

80 watts - 6 amps.
It's not the perfect solution because it doesn't balance. If it balanced the cells while discharging them I would be so all about this.

For the person with a charger that does not discharge to storage capacity I'd highly recommend this.

Finally, I've not tested parallel discharging yet. This is what I need, for those days when I return home with a dozen or more still charged batteries.

 

[RCdiy]

Maybe their next iteration will have balancing.

Given the low power parallel discharging N lipos will take N times longer but saves you the repeated connection cycles.

Its no worse that running the battery down inflight and then just leaving them discharged till we fly again in a few days.

Better than leaving them charged?

One could set up a stationary thrust station, voltage sensor and a lua script to discharge batteries Actually no need for Lua, logical switches could do the trick. Batteries could be discharged in 5 to 10 minutes. Now to deal with the noise

Another approach is to use a 12V battery protection module with low voltage cut off with a 12V water immersion heater or a 12V kettle

 

[RCdiy]

Found this.... it balances as well
http://www.myrcmart.com/rcx-3in1-ba...oltage-indicator-150w-discharging-p-4767.html

Wayne,
Maybe you could put something like this together that is a bit more refined... $25-$35 price point?

 

[Wayne]

LOL - We did sell that one, but they raised the prices so darn high our distributor will no longer buy from them. I think some other issues popped up. We ran out of them a month or so ago. One of the guys here was designing a housing for the lights, etc.

 

[Rick]

I too put my unused batteries to discharge storage when returning home. But doing so one-by-one wasn't cutting it. So I made up my own discharging board utilizing 4-50 watt incandescent 12V bulbs screwed into sockets. I use this for 2S thru 4S and each bulb presents ~ 4 amps of load when brought into line. Since I commonly use parallel charge boards I reasoned why not discharge them that way? I then place one of those voltage readout alarms on the balance lead connected to the boards. I set the alarm for 3.8V and as the packs come down and I get the first alarm I then unscrew one bulb at a time until they are under about a 3-4 amp load from the final bulb. I also connect my wattmeter between the parallel board and board I have the bulbs mounted to. Doesn't take long, I busy myself with other things, use the extra light on my bench while I'm at it and I get alarms along the way. I've found little need to balance individual cells as the many packs in parallel balance the whole.

 

[Scott Page]

I've also been very pleased using a 6 battery parallel board with the ISDT FD100 Smart Discharger.