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Battery charger/minder/tender - redux

 
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Mauledriver(at)nc.rr.com
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PostPosted: Wed Dec 20, 2017 12:10 pm    Post subject: Battery charger/minder/tender - redux Reply with quote

* warning - slightly off topic*
I left several cars idle for a month and was rather upset when my wife's new Miata's battery was 'dead'.  Clearly a parasitic load was involved and that would seem to be a defect.  Then after considering all the electrical tricks this particular car plays (e.g. the electric windows are slightly nudged each time a door is opened or closed in order to get a good seal with the retractable roof) I thought, "of course there are parasitic loads, and they may be a bit more than the electric clock in my Dad's old DeSoto".

I'm thinking that just about any modern car has some parasitic loads.  I have a mid-90s Caravan for occasional junk hauling that has weathered a few parasitic load problems like a trailer brake.  Even with all those cleared I know  that the transmission can be reset by disconnecting the battery, so there must be some very small loads designed in.

So while I know I don't need a minder for my 680s, I think I'm getting one for the Miata since there is a tendency to not put many miles on it in the winter.

And I guess it's okay to use my Schumacher SC3 for an occasional charge of my 680s.  Even though the charger doesn't have settings for AGM versus Lead Acid, versus Gel, it does specifically state it is good for AGMs.


On 12/14/2017 9:53 AM, Bill Watson wrote:

Quote:
Having ruined a number of 680s during my 10 year odyssey, I've come to the same conclusions as Kelly has below.  I'm a bit late to this discussion but here one thing I have empirical evidence for; undercharging these batteries will slowly kill them, slowly but inevitably. 

Three things I KNOW will do this is
  1.  Inadequate voltage in aircraft charging circuit (read the spec sheet and obey it).  This seems straight forward but do check that the voltage you are displaying is the voltage the battery sees.  I was measuring the voltage for my two charging circuits in two different places (EIS and EFIS).  Turned out one was accurate and one was not.
  2.  Old battery tenders/minders not intended for AGM batteries.  During my build, I had a few left over from my gel cell days in gliders.  They will not adequately charge a discharged 680 but it takes about 1.2 years to discover that.   I'm not sure, but using an old one to just maintain is worse than throwing the old thing away.  If there are  tenders/minders on the market now that are unsuitable for AGM batteries, I wouldn't know, but see Kelly's points below - you just don't need one, you need an AGM capable charger.
  3. Parasitic loads when not in use.  My load was fully documented; the clocks in my (3) GRT EFISs (this has since been eliminated thru an enlightened SW upgrade).  It was a very small load but it was 3X a small load. I have 2 batteries but the load was connected to only one, which made diagnosis easier but more expensive.  Why is such a small load in a frequently flown plane such a problem?  Didn't grandpa drive cars with electric clocks?  That didn't seem to be a problem.  Well it was occasionally a problem.  And with AGMs, a parasitic load seems to be equivalent to undercharging it; the battery is sits in a slowly declining state then is undercharged the next time it gets hit with the starter load.  I don't know whether that is actually the mechnism but I KNOW a parasitic load will slowly, inevitably, kill a 680 or 2.  I guess you could keep it on an AGM certified minder/tender but I'd suggest hunting down the load and killing it.
Things will work just fine with any 3 of these conditions for 1-2 years then they won't.  It's a slow death that may mystify you for $awhile$.  I have a boat but 680s make lousy anchors.

Speaking of boats, my little jon boat is parked next to my '10.  The Walmart/Schumacher charger with settings for AGM, Lead and Gel Cell(?) batteries worked fine until I apparently wore it out charging the lead acid trolling motor battery every other day.  I'm going to separate chargers as a result.

Regarding 'empirical evidence'; label, log and track your batteries, especially if you have 2 of the same installed like I do in my Z-14 scheme.  That data is the key to figuring out whether you have slow death problems or not and what might be causing them.  Problems are easily mitigated with a dual batt/alt/bus Z-14 which is good and bad.  It can delay diagnosis of electrical system problems because they aren't so critical.  Which means that you can kill 2 batteries with one problem before you decide to act.

Bill "I KNOW is shorthand for 'ask me how I know and how much it cost me to figure it out' " Watson
On 12/6/2017 10:45 PM, Kelly McMullen wrote:

Quote:
--> RV10-List message posted by: Kelly McMullen <kellym(at)aviating.com> (kellym(at)aviating.com)

The Odyssey is a variant of the AGM technology. I suggest that you do not need a "tender". You need something that can recharge the battery whenever it has been run down. Most any automatic charger with an AGM switch will do...as long as you only charge things when you are present.
AGM batteries have a very low self discharge rate, and if there was no leakage of current, would be very fresh after 3 months of sitting.
If you want a genuine Odyssey charger, you can go with
https://www.batterymart.com/p-obc-12a-odyssey-portable-charger.html
or
https://www.batterymart.com/p-obc-6a-odyssey-portable-charger.html
Both a lot less than the overpriced Battery minder models.
Again, I would NOT leave a charger of any kind on a battery unattended.
There are several unnecessary risks.



On 12/6/2017 8:24 PM, Ed Godfrey wrote:
Quote:
--> RV10-List message posted by: Ed Godfrey <egodfrey(at)ameritech.net> (egodfrey(at)ameritech.net)

I am looking to get a battery charger/tender and was looking for the Walmart one that Tim had suggested a number of years ago, to charge my Odyssey PC-925 battery. It seems that they no longer carry the WM-2500A model any longer. Does anyone have any suggestions as to what would be a suitable replacement? Thanks.

Ed Godfrey



































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Tim Olson



Joined: 25 Jan 2007
Posts: 2747

PostPosted: Wed Dec 20, 2017 12:53 pm    Post subject: Battery charger/minder/tender - redux Reply with quote

If you're ok with having parasitic loads, I did find a device that I
bought for my truck, that can at least let you monitor your battery.

https://www.batterymart.com/p-081-0172-wireless-battery-monitor.html?gclid=CjwKCAiAsejRBRB3EiwAZft7sAXMPY8TZL8cCg4x-nF9y54EYPvNo9rtg2E94_p_apCDfMq6SUP9JBoCnzgQAvD_BwE

It's the Battery Tender wireless battery monitor.

I put a lighter pigtail on it, and plug it into my trucks always-on
accessory socket.

Warning: It was THE BIGGEST PAIN I've ever experienced, ever, in
configuring a wireless device, but, it does work. For my truck
that I don't drive much in the winter, I left the Ctek charger on it,
with this plugged into the truck, so any time I want I can check
the voltage of my battery. If the charger turns off, in theory
I will get an alert if the battery drains too low.
Better than not knowing, I guess. But questionable if you need it
if you're going to leave a charger on it anyway.

It turns itself off and every 10 minutes turns on, uploads the
battery voltage, and then sleeps again.

Tim
On 12/20/2017 02:09 PM, Bill Watson wrote:
Quote:
* warning - slightly off topic*
I left several cars idle for a month and was rather upset when my wife's
new Miata's battery was 'dead'.  Clearly a parasitic load was involved
and that would seem to be a defect.  Then after considering all the
electrical tricks this particular car plays (e.g. the electric windows
are slightly nudged each time a door is opened or closed in order to get
a good seal with the retractable roof) I thought, "of course there are
parasitic loads, and they may be a bit more than the electric clock in
my Dad's old DeSoto".

I'm thinking that just about any modern car has some parasitic loads.  I
have a mid-90s Caravan for occasional junk hauling that has weathered a
few parasitic load problems like a trailer brake. Even with all those
cleared I know  that the transmission can be reset by disconnecting the
battery, so there must be some very small loads designed in.

So while I know I don't need a minder for my 680s, I think I'm getting
one for the Miata since there is a tendency to not put many miles on it
in the winter.

And I guess it's okay to use my Schumacher SC3 for an occasional charge
of my 680s.  Even though the charger doesn't have settings for AGM
versus Lead Acid, versus Gel, it does specifically state it is good for
AGMs.




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