wha-tah-hey

I'm new to Lipos and have an IMax B6 charger, with less-than-crystal-clear-to-me instructions.
In my application I'm using 1100mah 1S cells, I think 20C.
When charging @ C/1 and 1100mah max capacity, it times out @ 120mins (not settable, best I can tell) without reaching full charge.
I'd assumed that the Waste Time setting (default @ 5 mins) would auto-restart charging until full charge was reached, but Noooo - it just sets there blinking at me.
If I manually restart, the Charge Capacity reading resets to 0 and when it reaches full charge may read only 800-ish or whatever.
And, 'though late-state CV (or is it VC?) charging indicates 4.2v, full-charge VOM reading is only ~3.9V.
A 2-step charge (3rd for the cell) read 4.05v immediately after, 3.95v after ~20 mins rest.
Another 2-step charge on a different cell (4th for it) reached capacity limit and read 3.9v.
Any thoughts on what I'm doing (or thinking) wrong?

Thanks.

Terry

chuckk2

What should be happening with a "good" Lipo.
The 1C charge rate should be 1.1A It will eventually taper due to a charge mode change from CC to CV.
The time to charge should be less than an hour, since a good Lipo would have a residual charge at the start of 20% or more.
The 3.9v result makes me think that the charger may be malfunctioning, or not setup correctly.
Some chargers have to be set differently to charge 1S batteries, or those without balance taps, such as a 1S.
I'd expect to see about an 800-900mah charge reading from a 1100mah Lipo when things went as they should.
A possible problem with voltage readings has to do with the accuracy or lack of when it involves tenths or hundredths of a volt.
You mentioned a VOM. These usually have between 1 and 5 percent accuracy at full scale.

If I remember correctly the Imax B6 is a sort of clone of a Bantam DX6 charger. With the bantam, assuming the voltage readings are correct, I'd suspect
the battery type setting being incorrect as one possibility.

Besides the 4.2 fully charged voltage, there is another number that can cause the charge to terminate. This is a percentage of the set charge rate or battery capacity that is used to set the charge rate. The common values are usually stated such as C/10 or C/20. What this means is that with a charge rate of 1.1A, the low charge rate cutoff would be about 110ma or 55ma, when the charging voltage reaches about 4.2v plus a small amount. (Kirchoff's laws apply) Higher than normal battery impedance (IR) can fool the charger into terminating the charge prematurely. It can be sometimes useful to set a lower maximum charge rate, since this also lowers the charge termination current limit.

wha-tah-hey

Thanks Chuck - being a Lipo newbie (and "electronically challenged"!) much of what you say is over my head.
However, more searching indicates the problem to most likely be me: I bought a Chinese B6 knock-off (among other things, says SkyRC on start-up but can't access calibration menus) and generic Lipo cells.
To modify a phrase: "cheap in, cheap out".
My application isn't critical and they'll do for the time being.

Terry

wha-tah-hey

Just an addendum, in fairness to my knock-off B6:
I charged a brand new cell @ C/.5 and after ~1 hr it shut off; a DVM check read the proper 4.2v and checking a couple hours later it was still 4.2v.
Other clone issues aside, my problems were definitely of my own inexperienced doing.
It may be luck, but I'm content enough now with the purchase. YMMV.

Terry