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/
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