Marc_B Posted January 2 Report Posted January 2 https://batterymanagement.concordebattery.com/BatteryDocs/TB15.pdf Thread on BT about recommendations from Concorde changing regarding battery minders. I don't recall seeing anything about this and wonder what happened/changed? I have a Concorde RG24-15M that was installed in 2019 and still going strong. I typically use a BatteryMINDer for Concorde 24V system which has temp probe for temp compensation and haven't had any issues. Previously it was recommended to use the BatteryMINDer as it had a float/desulfation mode that would "condition" the battery and keep topped off for better battery longevity. Not sure what issue was identified by Concorde, so curious if this technical bulletin changes anyone's practices? I have a single SureFly and they report a very low parasitic draw ("less than 1mA" cited as around 0.001 mA). Concorde mentions that rate of self-discharge if there is no parasitic load on the battery is approx 4% per month at 25 deg C (rate doubles every 10 deg C rise in battery temp). So it seems that a Surefly would be FAR less (~0.005% per month) than the self discharge rate and so would still fall in the general recommendations for "Aircraft without parasitic load": (For non-SI simplicity, these temps correspond to < 60 F, 60-95 F, and >95 F) Does anyone have any idea what prompted the Technical Bulletin from Concorde and if this is applicable to the BatteryMINDer for Concorde systems? (I presume so given this wasn't called out in the bulletin). I always thought that AGM batteries really needed a specific charger to "top off" and avoid sulfation rather than just relying on the aircraft alternator which never really topped off the battery.
Marc_B Posted January 5 Author Report Posted January 5 Spoke with BatteryMinder Tech support. They are aware of the Concorde Technical Bulletin and said that the issue Concorde was seeing was loss of water from overcharging and was seen primarily with charging in temperatures over 90 deg F. In general they recommended against charging a battery when temps are over 90 deg F and in the summer in many locations would recommend charging at night only or avoiding all together. The issue with loss of water with a sealed battery is that there is no way to replace it. They said that the parasitic load with leaving the BatteryMinder connected to the battery but not plugged in was just an LED bulb and was probably much less than 10 mA, but didn't have a specific value. The Concorde Technical Bulletin had a formula for calculating parasitic load: i.e. 100 * 0.01A * 24 * 30 / 13.6 (capacity of RG24-15) = 52% per month! I suspect it's probably similar to the self-discharge rate rather than truly 10 mA. So my guess is that discharge is somewhere around 3-5% per month or less (connected but unplugged). So I think that in that case likely either continuous charging or completely disconnecting would be preferable. My suspicion is that a happy medium is to try to plug in at least once a month and just leave until the next flight (with cooler temps). In the summer the best bet is likely not leaving it charging and just using the cellular switch to charge at night, once a month to top it off. Of course given that the rate of self discharge is highest with increasing temps, I guess the general recommendation is if you live in a HOT area go fly frequently to get out of the heat!! ha ha 1
laytonl Posted January 6 Report Posted January 6 I charge mine overnight about once per month and I replace the batteries every 8-years. Lee 2
Schllc Posted January 7 Report Posted January 7 Desulphating the batter can take weeks, if not longer. I know at times my hangar probably gets as hot as 95deg during the day, but I have always plugged the charger in at the end of every flight when home and have never lost a battery, and the current ones in my Mooney and A are 7+ for the Mooney and 8 for the A… (knock on wood). I suspect the recommendation is likely referring to charging a depleted battery, not the trickle charge that is applied on a battery that had been “topped off” due to flight. I don’t believe the battery will get very hot on trickle, but haven’t ever really checked… 1
LANCECASPER Posted January 7 Report Posted January 7 Ever since that Technical Bulletin came out I bought a timer and I have my Battery Minders come on a couple times a week during the night for a few hours. https://www.amazon.com/dp/B07G9RK4VV?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1&th=1 1
M20F Posted January 7 Report Posted January 7 38yrs never used one, if your battery goes dead you really need to fly more. In the Mooney I am on battery #2 in 15yrs. 4
Jackk Posted January 7 Report Posted January 7 37 minutes ago, M20F said: 38yrs never used one, if your battery goes dead you really need to fly more. In the Mooney I am on battery #2 in 15yrs. Depends on where you live and how much you like your battery In the north the cold will zap a battery pretty quick Also if you have power in your hangar, with the price of a trickle charger vs a new battery, and with how little effort it takes to plug the pig tail in, why not?
Andy95W Posted January 7 Report Posted January 7 3 hours ago, M20F said: 38yrs never used one, if your battery goes dead you really need to fly more. In the Mooney I am on battery #2 in 15yrs. 33 years and the same experience, 20 of those years in Michigan. 1
M20F Posted Wednesday at 10:07 PM Report Posted Wednesday at 10:07 PM 9 hours ago, Jackk said: Depends on where you live and how much you like your battery In the north the cold will zap a battery pretty quick Also if you have power in your hangar, with the price of a trickle charger vs a new battery, and with how little effort it takes to plug the pig tail in, why not? I lived in Chicago for 8 of those years of ownership. I am from North Dakota, I am familiar with cold. You do you but I see no point to a trickle charger. 1
MikeOH Posted Wednesday at 10:08 PM Report Posted Wednesday at 10:08 PM Spent most of my career as a EE; conclusion: I don't trust electronics! I'm not about to leave something electric plugged in and hooked to my plane in a closed hangar for possibly a week, or more. Small risk, I suppose, but catastrophic if it catches on fire and burns down a hangar row. No reason to assume that risk when I've never had an issue with my battery running down from sitting. Edit: I actually think continuous use of a battery minder will 'mask' a battery that is beginning to fail....you pull your plane out of your hangar and it starts right up because it's been on the minder...then you go to start up for your return flight, possibly days later, and the battery is dead. Without the minder, a failing battery will start to show signs BEFORE you depart your home drome. In fact, that is exactly how I knew it was time to replace my battery; slow cranking at MY hangar, not out in the boonies! 3
Vance Harral Posted Thursday at 02:16 AM Report Posted Thursday at 02:16 AM 3 hours ago, MikeOH said: No reason to assume that risk when I've never had an issue with my battery running down from sitting. A respectful +1 on this from me. Data point: our airplane is hangared in the Denver area where temps occasionally reach 100 in the summer and below zero in the winter. We don't have a Battery Minder or any similar gizmo. We rarely hook up any kind of charger, not even when the airplane sits in the maintenance hangar for a week or two with the gear being cycled for an annual inspection. Throughout all this "abuse", we've been averaging 7 years of life on Concorde RG batteries over the last 20 years. And yes that includes actual capacity tests, not just "it was strong enough to start the engine". Air temperature inside our hangar is probably a bit more temperate than atmospheric OAT, and the airplane rarely sits more than a week or two between flights that charge the batter, so our use case is not particularly extreme. Still, based on our experience, I think a lot of owners running Battery Minders are taking on unnecessary trouble for not much benefit. 2
Justin Schmidt Posted Thursday at 02:35 AM Report Posted Thursday at 02:35 AM 4 hours ago, MikeOH said: Spent most of my career as a EE; conclusion: I don't trust electronics! You too...i shake my head at co workers 1
Jim Peace Posted Thursday at 03:38 AM Report Posted Thursday at 03:38 AM I just had that battery minder sent to my house. It has the temp sensor… I have not been home yet to read the instructions where does that temp sensor go? Just outside the charger or in the battery compartment?
dkkim73 Posted Friday at 02:54 AM Report Posted Friday at 02:54 AM On 1/6/2026 at 5:07 PM, Schllc said: Desulphating the batter can take weeks, if not longer. I know at times my hangar probably gets as hot as 95deg during the day, but I have always plugged the charger in at the end of every flight when home and have never lost a battery, and the current ones in my Mooney and A are 7+ for the Mooney and 8 for the A… (knock on wood). I suspect the recommendation is likely referring to charging a depleted battery, not the trickle charge that is applied on a battery that had been “topped off” due to flight. I don’t believe the battery will get very hot on trickle, but haven’t ever really checked… Yeah, how big an issue is this, really? Damned if I do, damned if I don't. In a cold hangar it would seem unlikely that it's boiling off the solvent. I don't think it should be electrolyzing hydrogen in this mode. 1
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