Batteries not getting to 16.8v (according to multimeter)

[whoelseisbored (LiamHowe89)]

Hi guys,

I'm balance charging my Turnigy 1400mAh 4S batteries (at 1.0C) and after one of them finished I thought I'd check the voltage with my multimeter. It shows 16.5v.

So I check each cell and they show as 4.13v / 4.14v / 4.14v / 4.14v - so no dead cells from what I can tell.
I've hooked it back up to the charger (IMAX B6) and set it off again which goes for a couple of minutes and they says it's finished. Charger says 16.8v... checked it with the multimeter and same again, 16.5v.
So what's going on? Is my charger just pants?

Any pointers would be greatly appreciated

[badger1]

I wouldn't worry about it.  because of how the discharge curve on LiPo's works there's very little energy in the 0.3v between 16.8 & 16.5V compared to, say, between 15.0 & 14.7V.

what happens if you measure a part-charged or discharged battery on your charger vs. your multimeter?  it might just be inaccuracy/calibration error between the two.

[Bad Raven]

Talking std, not HV, the nominal voltage when new and fully charged is 4.20v per cell and the pack should reach to or very close to that.

This max will slowly lower over time as discharge/charge cycles are put through the pack, especially if you run down the pack excessively low or if your installation heats the pack up in use to more than chill off, but not hot.

If the pack is genuinely only charging to 4.13v, its an indication that the cells are below par, either aged, abused, or just poor. A pack only charging 4.13 DOES matter. My three to five plus year old packs are still always charging 4.17 plus, and the lower voltage matters if it links (as so often it does) with reduced duration. 4.13v if genuine is LOW on a less than two year old pack and is generally indicative of an issue.

Cheapo chargers are usually very bad at balancing, and then starts the issues as one cell is regularly "over charged" beyond its capability (4.20 new, less as it ages). Since your figures are even, this can be discounted this time, but is common.

As far as voltage charged to, a low voltage if even (balanced) is generally the pack and not the charger.

What MATTERS is that the pack can hold the 3.7v plus voltage per cell under the load of use for a decent time, one that is depending on capacity.

We'd need to know a lot more to say more.

What ARE the packs? Capacity?, Age? Discharge Rating?  What current are you pulling from them (Have you calibrated Betaflight fully, is it displayed?), What voltage are you stopping at? (has this been calibrated in Betaflight too?)  Do you have average V per cell up in OSD?  Do you check max current and mAh used after flight in OSD? What is actually determining when you land? When do you charge?, on return?, before flight? Do you use storage charge?  (I do not!!) Are these packs in any way swollen, and if so by how much?

Do you have a wattmeter to measure current and voltage? If not how do you calibrate Betaflight or your FC firmware?  Have you a decent balancer other than the charger?  (I can recommend the ISDT BATTGO) .

Well you DID ask!!   

[ched]

There is an another possibility. The IMAX B6 might need calibrating!!! Do a google search for 'calibrate IMAX B6' then follow the procedure BUT you need to be sure you have a multimeter that is accurate. If your multimeter is under reading you could calibrate the charger to over charge the lipos!!!!!! So calibrate against a multimeter with caution!!!!!!