You are better off to add more batteries in parallel than caps. Sent from my iPhone
> On Mar 1, 2019, at 3:33 AM, Steve Heath via EV <[email protected]> wrote: > > Adding supercapacitors in parallel with the approproate balancing circuits > (Aliexpress is your friend) is more about making the battery life easier and > for recoving more of the available regen current. Proper balancing circuits > and not simple resistors is a must in my experience as you need to prevent > the voltage across the capacitor from exceeding its spec = typically around > 2.7 v. This is why you need a lot in series to cope with high voltages. I > have 22 in series which means that They stack is ok upto 59.4 which gives a > nice safety margin over the 54.2V the pack can provide when fully charged. > > This kinder environment does extend the range as more of the battery capacity > can be extracted. On some of the studies shown indicate an improvement of > about 15-18% on the range. Yes adding additional packs inparallel is always a > big help, but the batteries are still exposed to the high peaks albeit at a > lower level and it is these peaks that the supercaps prevent/mitagate/remove > (select as appropriate). > > The energy that is available from the caps is not the complete energy stored > as the voltage will go from 4.2 to 2.8v on each lithium cell. So on my 48v > system this means from 54.2 to around 36v which is still an appreciable > amount. The leads and battery internal resistance effectively act as > resistors so when the motor wants big power, the path of least resistance > comes into play and it is the supercapacitor that provides the main power for > the peak.As the peak goes down and the supercapacitor voltage drops, the main > batteries take over and some current is diverted to the caps to bring them up > to voltage. This happens very quickly so in most cases, it is not seen with > simple instrumentation. > > When I disconnected the super caps, I did see a significant reduction in the > regen currents I could achieve: 40-50A instead of the 120-130A . I also saw > a far higher voltage drop on the battery packs after hard acceleration. I > also saw a slower voltage recovery time as well. > > So they are very beneficial. Yes adding more packs will show some similar > benefits, but the issue of peak currents is not totally addressed. Yes they > are reduced because of the greater load sharing but they are still present. > In summary: Supercaps can harvest more regen current, provide a kinder > environment for the batteries and give some improved range. Adding more > batteries places less stress on the batteries, will harvest more regen > current but nowhere near the level that a supercapcitor will and will give > significantly more range. The environment is still not very nice as the peaks > will still be there. > > Which way to choose depends on the problems that are being addressed and the > relative costs of the solutions. > > You pays your money and you takes your choice. > > > Steve > >> On 28/02/2019 05:55, Cor van de Water via EV wrote: >> His use of Supercaps was a bandaid: due to the excessive internal resistance >> of the LiIon batteries that he found, he had to make up a solution to give >> him the ability for a short power burst (to merge on freeway for example). >> Supercaps happened to be on sale, so it worked out for him, but they do not >> add range, just a temporary boost. >> If you add a parallel pack of batteries, you add both range and double the >> current (or half the voltage sag) of your pack, so that is typically >> preferred. >> I have a similar situation: well-used Nissan Leaf 1st gen batteries that >> tend to sag quite a bit due to increasing internal resistance, but with 2 >> packs in parallel, each only sees half the current so the sag is reduced and >> my range more than doubled. >> Cor. >> >> Sent from Mail for Windows 10 >> >> From: brucedp5 via EV >> Sent: Wednesday, February 27, 2019 8:55 PM >> To: [email protected] >> Cc: brucedp5 >> Subject: [EVDL] (metricmind.com links): Supercaps reduce li-ion pack sagging >> >> jay sez >Victor Tikhonov (of MetricMind) used a string of 2.7kF Maxwell >> supercaps< >> >> Advanced electric vehicle conversion project - Battery ... - Metric Mind >> www.metricmind.com/ac_honda/ultracaps.htm >> The power boost ultracapacitor stack. Manufacturer: Maxwell technologies. >> Cost: $4,800 (liquidation sale). Ultracaps The LiIon battery I use proved to >> be a good ... >> >> Advanced electric vehicle conversion project - Metric Mind >> www.metricmind.com/ac_honda/main2.htm >> ... 10 LEad acid batteries will be replaced with 28 ones, later - with 96 >> LiIon ones (later supplemented with ultracapacitor bank) and then - with 24 >> NiMH ones?? >> >> FAQ | Metric Mind Corporation >> www.metricmind.com/education/ >> ... AC drives available for amateur conversions since 2003, first use of >> supercapacitors, first lithium ion batteries (Honda ACRX), first >> informational LED lighting, ... >> >> High End No Compromise Electric Vehicle Conversion ... - Metric Mind >> www.metricmind.com/audi/1-initial.htm >> Apr 6, 2008 - I installed AC drive system, tried several battery types (Lead >> Acid, Lithium Ion and Nickel Metal Hydride), ultracapacitors and few other >> novel at ... >> >> https://www.google.com/search?q=Metric+Mind+ultracapacitors >> >> >> >> >> For EVLN EV-newswire posts use: >> http://evdl.org/archive/ >> >> >> {brucedp.neocities.org} >> >> -- >> Sent from: http://electric-vehicle-discussion-list.413529.n4.nabble.com/ >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) >> >> >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: >> <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20190227/352bc590/attachment.html> >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) >> >> > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
