v-balance unit issue

[jpeter]

I charge T-rex 450 se batteries with an Electrifly 4 polycharge charger and a v-balancer in link mode.

After the charge is complete the charger, as expected, drops out, however, the v-balancer stays active with all the lit leds discharging the pack. I've yet to spoil a pack but I've discharged one to the red zone on the fuel gage.

I know unattended charging is foolish. (please don't flame me) Never-the-less, a little carelessness shouldn't be cause to ruin a $75 battery pack.

I'll bet you can simulate the same scenario, just unplug the charger during a charge. Most likely the v-balancer will stay active. If not, I want to know. What would happen if your charger inadvertently disconnected shortly after you started charging a close to dead pack? Would your v-balancer discharge it into the dead zone? Anybody know?

Anyone have the same experience. Is my v-balancer working properly.

Jim

[Greg Alderman]

Yes your v-balancer most likely is working properly...the charger is just sensing a full charge and shutting down prior to the v-balancer sensing a full charge and dropping out of link mode...when the charger finishes you need to manually drop out of the link mode...

I have used chargers with my v-balancers that secure before the v-balancer can drop out of link mode (TP1010) and I have used balancers that the v-balancer seems to drop out of link mode before the charger secures (Shulze 6-330).

[WillJames]

We have tested this by hooking the V-Balancer to the balancing taps of a pack, putting it in link mode and leaving it for 24 hours and it did not discharge the pack. The link LED stayed on the entire time.

I too would agree with Greg that our V-Balance module is working properly.

[Tomas Ahl]

According to the V Balancer manual (http://www.flighttechdistribution.co.uk/Products/Manuals/FPVBALCOMPLETE.pdf):
Immediately after connecting the battery, the V-Balance unit will turn on and commence counting through the number of cells in the pack in preparation for automatic balancing. If the pack is already balanced the V-Balance will flash all LEDs corresponding to cells in the pack 8 times slowly and go into sleep mode unless the Link Mode is activated first. If the pack is not fully balanced, one or more LEDs will flash indicating that balancing action is taking place and this will continue until the battery is balanced (unless in extreme cases a low voltage limit is detected first). (Extra emphasis added by me.)

So a pack should never be overly discharged unless this is the case already from the beginning.

The same is expected to happen if the balancer is connected stand alone to a pack (i.e. no charger connected to the balancer).

[jpeter]

Regarding Thomas' response: If it's in link mode it won't drop out.

Regarding WillJames response: What happens if the charger drops out when the pack is already close to dead, or perhaps you don't get check it for more than 24 hours or maybe its a small 300 ma hr pack from a cox plane. Then does it have 24 hours of power in it?

The v-balance unit has lots of good features but its got a quirk that need addressing.

I put a pack on charge last night. I forgot to disconnect it before I went to bed. When I got home from work today the fuel gauge reported next to the red. I couldn't fly that pack until I recharged it.

[Tomas Ahl]

OK, sorry for the confusion.

All I can say is that my V Balance unit is not dropping out of link mode when the charging is ready either. But I have yet to forget a pack connected long enough to be able to observe whether it will be discharged in that situation. (If it matters I feed my balancer from an Orbit Microlader 6.3.)

[Tomas Ahl]

Come to think of it, maybe it is the type of charger we use in combination with the V-Balance that determines whether the packs are "automatically" discharged if left connected for relatively extended periods after the charging phase is finished? Maybe there are chargers that doesn't isolate its output connectors after having ended a charge phase?

The V-Balance expressly supports running discharge cycles from the charger to check packs so maybe the following section of the manual comes into play here:
The V-Balance can also be used in Link Mode as part of a discharge process using a charger with this feature or another load, although it is not generally recommended to cycle Lithium Polymer batteries in this way it can be useful to measure total battery capacity. The V-Balance will make sure the cells in the pack are discharged evenly and that the load is disconnected before any cell is overdischarged, it is important however to make sure you do not exceed the 10 Amp rating of the balancer.

Just a thought!

[Greg Alderman]

Tomas...my thoughts exactly...but since I had not tested this I was not going to mention it as I AM NOT one to open my mouth and say something I am not sure about...but some chargers will drain what ever is connected to it if the charger is not powered up...one for sure is the charger that comes with the 14MZ...if you leave a battery in the charger and unplug the charger from the wall the battery will discharge if left in the unit...so what you are saying is for sure a possibility...