Hi Myles,
Thanks for your thoughtful reply.
Re load corrected and 210FT Blue batteries. The page and PDF I used are from here:
http://www.northstarbattery.com/product/nsb-210ft-blue
which quotes a 10hr capacity at 200 and 8 at 198. If I use a Peukert exponent calculator I get 1.05 to 1.13, so I'm not certain what it should be. I assume the 20hr rate is 210Ah. I'm using the sheets at:
http://www.smartgauge.co.uk/peukert3.html
But which one to use, the 1st or 2nd sheet and what Peukert. If the 2nd at:
http://www.smartgauge.co.uk/calcs/peukert.xls
I'd get 182 Ah @ 21 Amps and 175Ah @ 28 Amps load for a Peukert of 1.13. I think I'll recalculate on that.
Cycle life at 2050 @ 50% is from the product page above.
I have no personal experience of these batteries, but I know James Lambden does. Maybe he'll comment?
Discharge tables and manual here:
http://www.northstarbattery.com/media.ashx/nsbbluebatterydischargetables.pdf
and
http://www.northstarbattery.com/media.ashx/nsbbluebatterymanual.pdf
Totally agree re more columns ref WH/m^3 and Cost/N-m columns and cycle life cost and indeed your own batteries. Fancy adding/modding sheet to v2 with yours? It's work in progress after all. I suppose all I'm trying to show are 4 possible options for a simple direct drive, like my own boat, with low power requirements but similar cycle life and range. The weights and volumes are striking aren't they.
Out of interest I also weighed my electric bicycle 500Wh 36V LiPo battery. 190 Wh/Kg and roughly the volume which is slightly less than NMC.
John
---In electricboats@yahoogroups.com, <matwete@...> wrote :
Hey John-
Some observations and comments regarding your table "Battery Comparison".
First, "Load Corrected AH" --- Just looking at the 210FT Blue batteries, you show 196 and 190ah "Load Corrected AH". The specs I found online for the battery shows 185ah (20hr rate, or 9.25amps). Thus, the two values you show (196 and 190) should each really be much smaller than 185ah since the currents are each 21 and 28amps, respective. A better number might be 150ah.
Second, the table's column "Cycle Life" shows 2000 cycles to 50%DOD for these batteries. Online info I've seen shows "500+" cycles to 50%DOD. That's a Yuge difference.
Third, more columns could be added for the THINK/Enerdel, TESLA, Volt, Leaf surplus battery options, e.g.:
THINK/Enerdel 70ah 42v(nom) 24.5amp 2500 cycles to 80%, 80%Cap left 2400wh(usable) 30kg 80wh/kg TBDvol TBDrange $500 cost
Finally, the battery comparison should use the Cycle Life, Usable Energy and Cost info to give a Cycle Life Cost. Also, WH/m^3 and Cost/N-m columns might be useful.
-Myles
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of 66b6dcd5b59507e7d751ea81382ea1f6
Sent: Tuesday, June 27, 2017 3:14 AMHiTo: electricboats@yahoogroups.com
Subject: RE: [Electric Boats] Battery specific energy and power in relation to volume and density [1 Attachment]
[Attachment(s) from 66b6dcd5b59507e7d751ea81382ea1f6 included below]
Hi Myles,
Indeed, this was the point of my post and in my asking Hannu's knowledge of 'non boat' batteries. I agree re heat as we deal at such low loads compared to cars. Taking your reply a bit further, I just put this attached spreadsheet together for a boat that cruises at 4 knots using 1,000 Watts of battery power in calm conditions, for 4 different battery scenarios, all with similar ranges and battery cycle and calendar lives. Wh/Kg and volume are for the packs.
For simplicity I've kept the sheet as a direct drive so all scenarios work. The results will surprise some I suspect, especially when you look at range vs price, not to mention weight and volume. Mine is actually the 3rd (albeit the non Bluetooth Smart version) scenario. But being LiFePO4 they are the safest lithium chemistry I think for boats, plus they can do high C rates and have superior cycle life. The 4th wasn't around when I converted my boat.
The results are one of the reasons (for a small sailing yacht) I advocate as few batteries as possible and a small Honda 900W or 1600W continuous rated generator as a back up. It's the least expensive way and as a sail auxiliary the range is sufficient I'd say under battery power - we're meant to be sailing after all. This setup gives me 2 or 3 nights away on the boat, sailing when possible and subject to the wind there is generally no need to start the generator. I have a separate AGM house bank (2 x 12V 130Ah) with an inverter for a small kettle, grill, toaster etc.
I do my best to explain that in the link below where you can also see just how restricted for room I am, especially as I can only just reach out over the batteries to get to the PSS shaft seal if there was ever a problem.
https://www.victronenergy.com/blog/2016/08/29/multiplus-magic-small-generator-big-power/
John R.
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