---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 03/21/19: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:05 AM - Re: Battery BMS failures? (Robert L. Nuckolls, III) 2. 08:37 AM - Re: Re: Battery BMS failures? (Robert L. Nuckolls, III) 3. 09:52 AM - Re: Re: Battery BMS failures? (Eric Page) 4. 10:30 AM - Re: Re: Battery BMS failures? (C&K) 5. 04:58 PM - Re: Re: Battery BMS failures? (Eric Page) 6. 11:13 PM - Re: Re: Battery BMS failures? (James kale) ________________________________ Message 1 _____________________________________ Time: 06:05:23 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Battery BMS failures? > So the agile BMS watches temperatures > and strives to limit those effects > on the cells irrespective of system > demands from the outside. Oh yeah, forgot to include charge balancing. Unlike most battery chemistries, individual cells in a series string of lithium may become 'unbalanced'. This simply means that one or more cells may 'top off' sooner than the rest. If the charging continues until all cells are topped off, there is risk for over-charging the fast learners thus insulting their sensibilities. This is generally accomplished by placing a load resistor across the faster cells thus forcing more charge energy into the slow cells until everyone is in lock-step . . . consider a cell balancer to be the ISO9000 of the lithium battery community. Here's an article from Battery University on the topic . . . https://tinyurl.com/y3egekew . . . yesterday's missive was intended to illustrate that the term "BMS" is un-defined in the consumer world and maybe not well defined in the engineering world either. Unless you have access to the designer's product performance specification, it's wise to investigate before you plunk down your beer money for a battery upgrade. The full constellation of products offered are NOT interchangeable nor are they necessarily plug-n-play into our legacy electrical systems. In light of this fact, the phrase "BMS failure" in any dark-n-stormy-night story is not very informative unless the narrator offers specific failure analysis data . . . almost NEVER a component of such stories. Bob . . . ________________________________ Message 2 _____________________________________ Time: 08:37:44 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Battery BMS failures? > >Indeed, the deHavilland DHC-8-202 that I flew in >a previous life was fitted with battery >temperature gauges on the overhead panel (just >below the left fire t-handle in the linked image). > >https://bitly.com/2uj9V9F+ > >The airline I worked for operated them in the >desert southwest, where ambient temps routinely >exceed 100=C2=B0F. Given the short-hop, quick-turn >nature of the flying we did, and the >eye-watering current required to start >a >2,000shp engine, we kept a close eye on those gauges. > >Eric Did you ever have occasion to take a hot battery off line? Bob . . . ________________________________ Message 3 _____________________________________ Time: 09:52:26 AM PST US From: Eric Page Subject: Re: AeroElectric-List: Re: Battery BMS failures? > On Mar 21, 2019, at 08:36, Robert L. Nuckolls, III wrote: > > Did you ever have occasion to take a hot battery off line? Just once, but not in flight. After flying three Phoenix-Yuma-Phoenix round trips on an especially brutal July day, we exceeded limits and couldnt start up for the fourth scheduled Yuma turn. I cant say that either of us was particularly bothered by the forced break! Eric ________________________________ Message 4 _____________________________________ Time: 10:30:17 AM PST US Subject: Re: AeroElectric-List: Re: Battery BMS failures? From: C&K On 21/03/2019 11:36 AM, Robert L. Nuckolls, III wrote: >> >> Indeed, the deHavilland DHC-8-202 that I flew in a previous life was >> fitted with battery temperature gauges on the overhead panel (just >> below the left fire t-handle in the linked image). >> >> https://bitly.com/2uj9V9F + >> >> The airline I worked for operated them in the desert southwest, where >> ambient temps routinely exceed 100F. Given the short-hop, >> quick-turn nature of the flying we did, and the eye-watering current >> required to start a >2,000shp engine, we kept a close eye on those >> gauges. >> >> Eric > > Did you ever have occasion to take > a hot battery off line? > > > Bob . . . > An aircraft of that size and vintage may have had a battery charger that monitored temperature and could limit charging current?? It seems like the Lithium "BMS" strategies are moving in that direction. Limiting the alternator size as per Earth-X recommendations is a small step in that direction which I applaud. Even with VRLA batteries I tossed my 100+ amp alternator in favor of a 40 amp unit. Ken ________________________________ Message 5 _____________________________________ Time: 04:58:19 PM PST US From: Eric Page Subject: Re: AeroElectric-List: Re: Battery BMS failures? > On Mar 21, 2019, at 10:28, C&K wrote: > An aircraft of that size and vintage may have had a battery charger that monitored temperature and could limit charging current?? Dont quote me on this (its been awhile...) but as I recall, the temperature monitoring was separate from the charger. I think the chargers only data inputs were weight-on-wheels and where its AC Power was coming from (external or engine-driven generator). Eric ________________________________ Message 6 _____________________________________ Time: 11:13:54 PM PST US From: "James kale" Subject: RE: AeroElectric-List: Re: Battery BMS failures? I was a 28 year Army Active Duty helicopter pilot. In the mid 70's I had a Nicad helicopter battery completely melt down. Just molton liquid in the steel box container. Fortunately the hydrogen did not ignite. We smelled it and then noticed a terrifically high charge rate. We landed the CH-47 helicopter and we opened the battery box to find the mess. A few years later the Army put a warning in the manual to land if you smelled the rotten egg smell and get out of the helicopter get away from it and not to touch the battery. Finally in the 90s the manufacturer put a battery charger in the circuit which limited the charge current to about 10 amps. It prevented thermal runaway charging which could happen with the battery just tied to the main bus and a 200 amp generator attached to the bus. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com On Behalf Of C&K Sent: Thursday, March 21, 2019 12:28 PM Subject: Re: AeroElectric-List: Re: Battery BMS failures? On 21/03/2019 11:36 AM, Robert L. Nuckolls, III wrote: >> >> Indeed, the deHavilland DHC-8-202 that I flew in a previous life was >> fitted with battery temperature gauges on the overhead panel (just >> below the left fire t-handle in the linked image). >> >> https://bitly.com/2uj9V9F + >> >> The airline I worked for operated them in the desert southwest, where >> ambient temps routinely exceed 100F. Given the short-hop, >> quick-turn nature of the flying we did, and the eye-watering current >> required to start a >2,000shp engine, we kept a close eye on those >> gauges. >> >> Eric > > Did you ever have occasion to take > a hot battery off line? > > > Bob . . . > An aircraft of that size and vintage may have had a battery charger that monitored temperature and could limit charging current?? It seems like the Lithium "BMS" strategies are moving in that direction. Limiting the alternator size as per Earth-X recommendations is a small step in that direction which I applaud. Even with VRLA batteries I tossed my 100+ amp alternator in favor of a 40 amp unit. 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