---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 03/20/23: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:24 PM - Re: What's all this Lithium Specific Battery Charger stuff anyhow? (skywagon185guy) ________________________________ Message 1 _____________________________________ Time: 12:24:19 PM PST US From: skywagon185guy Subject: Re: AeroElectric-List: What's all this Lithium Specific Battery Charger stuff anyhow? Hi Bob, One aspect of lithium that is easily overlooked is the characteristic of its super low internal resistance (IR). This gives it the ability to offer huge amounts of current if called for. That is a huge advantage however that presents a problem sometimes. If the battery is somewhat depleted, connected to a old style alternator system, when the engine is started it is usually operated at fairly low rpm's. However, the battery due to its super low IR sits there saying "feed me all 60 amps" (or whatever the alternator set is rated) but it is barely above idle rpm. Thus it is generating a ton of heat with not the normal cruise speed air blast available to cool it. This problem really shows up in boats, RV's and such that have converted to Lithium. The answer is using an active current limiter between the battery system and alternator to protect the alternator for overheating..... D On Tue, Mar 14, 2023 at 12:58=AFPM Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > At 12:24 PM 3/14/2023, you wrote: > > The NOCOs are way overpriced. Bob's example does a better job at 1/6th th e > price. > > Bob, have you found a similar charger for lithium batteries? > > > There are lithium and then there are LITHIUM batteries. > I've oft pondered the contradictions in performance > claims by the various purveyors of lithium products. > > There are dozens of batteries that are simple > assemblies of cells stacked 4-high proposed > for service in a 14v system. They claim > to be drop-in replacements for wet or SVLA > products. > > Okay, if the thing is claimed to live happily > in a lead-acid environment, then what's > this "special lithium charger" stuff all about? > > Then there are products that offer battery > management systems within the battery itself. > The term "BMS" does not offer an industry > wide description of form and function. > > Products that seek to assure consumers of > 100% compatibility with the lead-acid world > often include electronics adding substantially > to the cost of the battery! Yet, there are as > many (if not more) products offered with NO > built in electronics. Some do offer a > cell-balancing connector. Ebay and Amazon > are replete with cell-balancing modules > that cater to the DIY battery-array market. > > I'll call your attention to the figures here > on my website: > > https://tinyurl.com/mw4fz3pf > > One figure illustrates a family of capacity > vs. charge voltage plots for an A123 > LiFePO4 cell. Note the battery performance > when charged at various termination voltages > ranging from 3.3 to 3.7 volts. In a 4-stack > array intended for 14v systems, these voltages > correspond to system voltages of 13.2 to 14.8 > volts. > > Note that cell capacity is essentially maxed > out with a charge voltage of 3.4 Volts/Cell > (13.6V system) with no significant improvement > above that. > > The other image is a snapshot of specs for > a well known variety of LiFePO4 cells that > state a max charging voltage of 4.2 until the > current drops below 100mA. This would be a system > voltage of 16.8 Volts! > > Perhaps this offers a reason for the success > of the many bare-foot, 4-stack engine cranking > products out there. As long as system voltage > is greater than 13.6 (but less than 16.8), > the battery has a high order probability of > a useful life. > > So, what's all this lithium specific charger > stuff about? The charger we've been discussing > in this thread tops out at just under 15V. No > red flags there. > > In the BMS camp for lithium products, we're > told that the battery is a plug-n-play replacement > of the EXISTING wet or SVLA battery. Rest assured > that the BMS will protect your substantial investment > from alternator malfeasance . . . except that its > not clear to me that the legacy lead-acid system > set up to charge and 14.2 to 14.8 volts is something > to be worried about. > > So that's a long introduction to my response to > your question. Unless someone has DATA to suggest > otherwise, I'm of the not-so-humble opinion that > lithium specific chargers are in the same class > as battery desulfators. There are dozens of patents > on desulfation processes NONE of which are accompanied > by repeatable laboratory grade tests that demonstrate > efficacy of their claims. > > I've got a EarthX battery on the bench that's > be maintained by one of my venerable BatteryMinders > for about 10 years. That reminds me, I think I'll > run a new cap and load check on the little feller. > Don't have an airplane to run it in but it's jump > started a dozen or so vehicles over the years! > > The one thing I've not yet mentioned is the 'cell- > balancing' feature suggested in some battery > management philosophies. > > Cell balancing becomes a significant concern as > the cells age. If the internal impedance and/or voltage > vs. charge current one layer in the 4-stack array > rises significantly over the others, it's capacity has > been depressed. So while its brothers are still actively > taking on more Joules of energy, the 'weak sister' is > at risk for exacerbated damage due to over-charging. > A cell balancing system places a dummy-load resistor > across a compromised layer of cells to reduce the > risks to the cells. > > Given what we've observed of the lithium art and > science over the last decade, I'll suggest that cell > balancing is probably not applicable to aircraft > applications. Keep in mind that the majority market > for batteries is populated with customers who routinely > deep-discharge their batteries and flog 'em until they > don't get up and hunt any more. > > We airplane guys are intently interested in > CAPACITY of a battery compared against DESIGN > GOALS for Plan-B endurance in battery only > ops. The rule of thumb for battery replacement > is to take it out of service at 80% of new > or when battery-only endurance goals are not > satisfied. > > In both SVLA and Lithium worlds, a battery is > likely to still be cranking an engine when it's > time to replace and before cell balancing becomes > a significant issue. > > That's kind of a long winded answer to your > question but hopefully gives you understanding > that supports future decisions. > > > Bob . . . > > //// > (o o) > ===========o00o=(_)=o00o====== == > < Go ahead, make my day . . . > > < show me where I'm wrong. > > ======================= ========= > > In the interest of creative evolution > of the-best-we-know-how-to-do based > on physics and good practice. > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.