[NSRCA-dist8] Battery checkers

[Patrick Harris]

OMG...Jim...don't say "parallel charging' around Gordon....he'll have a
fit! 😀



On Fri, Jul 31, 2015 at 3:59 PM, James Hiller <jnhiller at earthlink.net>
wrote:

> Tried to fly today 17 MPH 101 degrees, this is getting old.
>
> I use a free volt meter from HARBOR freight to check before flying to
> insure I'm not installing a used pack.
>
> Before charging I check the voltage of each twin 5S pack to select packs
> with nearly the same voltage - usually within 2/10 V before parallel
> charging. I always charge at 1C. Takes about two beers to recharge a
> day's usage.
>
> I monitor charge Mah, which is a total when parallel charging, that I
> average to a single battery to get a feel for per flight consumption.
>
> Occasionally I'll charge individual batteries to try to negate the affects
> of parallel charging.
>
> I've also noticed it takes longer to balance when the batteries are
> getting tired and I'll check the IR for weak cells ( IR Spread ).
>
> I'm also not working the batteries very hard only gaining maybe 20 degrees
> over ambient.
>
> Jim
>
>
>
>
>
> *From:* NSRCA-dist8 [mailto:nsrca-dist8-bounces at lists.nsrca.org] *On
> Behalf Of *Patrick Harris via NSRCA-dist8
> *Sent:* Friday, July 31, 2015 3:32 PM
> *To:* Gordon Anderson
> *Cc:* AK, ID, MT, OR, WA, WY
> *Subject:* Re: [NSRCA-dist8] Battery checkers
>
>
>
> All very true. I pick up on average about 5 percent after my packs set
> awhile. I find the checker I use to be pretty close, but always about 5 to
> 10 percent off what the true level based on what I actually put back into
> them.
>
>
>
> On Fri, Jul 31, 2015 at 3:25 PM, Gordon Anderson <gaa at owt.com> wrote:
>
> Karl,
>
>
>
> Here is my 2 cents worth....
>
> Predicting battery capacity from the open terminal voltage is not very
> accurate, I believe that is where this capacity prediction is coming from.
> I will bet if you let the batteries "rest" a few minutes after your flight
> and then check them again the capacity values will change. Battery
> chemistry is very non linear. I think the best predictor of battery health
> is the internal resistance, a lot of chargers will calculate and display
> this value. Keep an eye on trends, as the batteries age the internal
> resistance will increase and they will also get hotter during the flight
> and eventually start to puff up. The nice thing about monitoring IR is you
> can see if a cell is getting significantly different than the rest of the
> cells in the pack.
>
> The best way to know the capacity you have taken from the pack is to use a
> data logger that is measuring voltage and current and then calculating the
> maHr usage. Even in this case you will have to put more back in than you
> took out, this is because of the IR that burns some up in heat and the fact
> that the process is not linear.
>
>
>
> --Gordon
>
>
>
>
>
>
>
>
>
> On Jul 31, 2015, at 12:11 PM, Karl Watts <karlwatt at sarmc.org> wrote:
>
>
>
>
>
> Do any of you guys or gals use battery checkers?  Are they reliable?  I
> have one that I use to check my batteries before and after I fly.  For my
> flight packs – 2 5000 mAh packs it consistently reads 97-99% and after
> flying 14-33%.  My confusion is when I take a pack that say reads 14% after
> flying and charge it I am only putting in about 3000 mAh.  Seems to me the
> battery checker should show 40% not 14%, I used 3000 mAh which is 60% of
> the pack.  Should I discard the battery checker?
>
>
>
> Karl
>
>
> Confidentiality Notice:
> This e-mail, including any attachments is the property of Trinity Health
> and is intended for the sole use of the intended recipient(s). It may
> contain information that is privileged and confidential.  Any unauthorized
> review, use, disclosure, or distribution is prohibited. If you are not the
> intended recipient, please delete this message, and reply to the sender
> regarding the error in a separate email.
>
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.nsrca.org/pipermail/nsrca-dist8/attachments/20150801/82db8406/attachment.html>