B.CV phase taking forever

[wbefield]

I'm running a 308Duo with a pair of DPS-1200FB power supplies and charging single 1200mah 6s packs @2.4A charge rate. The lipo cells get up to about 4.19v in 20 minutes, but once it hits the B.CV phase it continues to run for another 40 minutes. Wondering if it is my charger or my lipos.

Everything seems fine when I'm charging my 5000mah 6s packs. I can charge a pair of these at 3c charge rate in about 25 minutes..

Anyone have any advice on how to troubleshoot this?

[RedOctobyr]

That's strange. Does the smaller pack charge OK on a different charger? It's possible the small pack is just in really bad shape, giving the balancer a LOT of work to do.

During that phase, you can see which cells are high, they'll be the ones with several little bars next to their voltages (going like yellow->red). Those are the ones the balancer is holding back. The cell(s) without those bars are the low ones.

You can charge it most of the way, and do a Balance on it (not Balance Charge), which should just work on bringing the cells together. Perhaps balancing them better once could help going forward?

What are the internal resistances of the different cells? If they are all, say, 6 mOhms, but one cell is 20 mOhms, that cell is in bad shape, and may cause trouble (it will behave differently than the rest).

There are some options related to when to end the charge. About whether to end it based on just charge current, or charge current & balance condition, etc. What's that set to? I think mine is still the default, I think it's the first option.

With 1.2A of balance current, balancing a single 1200mAh pack ought not to be a big problem. What are the cell voltages before you start the charge?

These are the results of some intentional-imbalance testing I did with my 308Duo, if it's of interest:
https://www.helifreak.com/showpost.p...&postcount=191

[Gregor99]

As Red says, note the balance state of the pack at the point the CV phase starts. If all cells are 4.2v then balancing is not your issue. Most likely the CV termination current setting is too low for the set charge rate. Raising the CV termination setting or raising the charge current would help.

By chance have you modified the CV termination current setting? In the 308 its called Chg. End Current. Default is 10%. Check your setting and report back.

[wbefield]

Thanks for the replies guys and Red, appreciate the link to your test. very informative. I need to get my duo setup with my logview.

I actually have 3 of the gens ace 1200mah 6s packs and they are all brand new with just a few cycles on each. This is happening with all 3 packs. Would be unlikely that all 3 packs are bad, but who knows, I've seen stranger things.

Internal resistance was in the 4-6 range on all cells, they all are balanced or very close when I first connect them and are at storage 3.85V per cell. All the settings on the 308 should be stock. If I changed anything it was not intentional. Will take a look when I get home from work and maybe throw one of them on my 206B to see what happens.

[Slyster]

well if they are new that could explain it. cycle them 5 times before flying them... alone.. not in parallel. New packs always take a lot longer to balance. If you want, use one pack to power the charger for another.. makes breaking in fast.

Just make sure your charger handles 6s input and you start with the power source lipo full.

[wbefield]

And the plot thickens.... I put the packs on the channel 1, and they charge and balance fine.

[RedOctobyr]

If you can reproduce it behaving normally on Ch1, but really slow on Ch2, using the same charging profile, it may be time for a call to your vendor, unfortunately.

[wbefield]

Unfortunately, my vendor was Readyheli.

[Slyster]

Call Dave at progressive RC and he can tell you what to do or who else to call.

[wbefield]

Thanks Sly
Will do

[wbefield]

Originally Posted by Slyster

Call Dave at progressive RC and he can tell you what to do or who else to call.

Yarden @Progressive RC would only handle this as an "out of Warranty" service since I didn't purchase it from them. They wanted me to pay them $45 to repair or replace it which is pretty disappointing since I've only had it a few months and it's barely been used.

So I checked with Helidirect, explained my situation with Readyheli being out of business and they are replacing it under warranty and they even cross shipped me one so I can get back to flying as quickly as possible. They definitely went above and beyond on this one.