Floodie / Lithium hybrid battery experiment

Have you considered using a PIC or other microcontroller with multiple A/D channels to do the monitoring? It could interface to an LCD display and/or it could connect to a Windows program vis serial port or USB to display the data and log everything to a data file for later analysis. Here is what I have done:
http://www.mytractorforum.com/showthread.php?t=239700

It uses quad op-amps as differential amplifiers so it can read voltages and currents without worrying about the ground reference. I don't have the circuit in good form but I'm willing to share details and source code. The PIC code is written in C and the Windows GUI uses Borland Delphi, but you can also use Hyperterm or any other serial port terminal application. However, for a nice display, you will want something a bit better.

I wasn't sure what the JLD was but I found this:
http://evtvshop.projectooc.com/proddetail.php?prod=JLD404AH

That is a nice meter but for $175 it's a bit much. If you don't mind a few hours of breadboarding you can build something like I made for less than $50 or so.

I may very well do something similar if and when I build a road-going EV. But I plan to use SLAs instead of FLAs, and I intend to make a 250-320V battery pack with a three-phase 230VAC motor and VFD. I can get 12V 12Ah SLAs for about $20 each, including delivery, so that is about $0.14/Wh (although probably closer to $0.25/Wh including Peukert). They are 12 lb each (1 lb/Ah), compared to 0.6 lb/Ah for FLA:
http://www.tractorsupply.com/en/store/stowaway-battery-st27dc180

The cost for these FLAs is $85 or $0.067/Wh. For my purposes, I would need at least 20 of these for 240 VDC, which would be 26.4 kWh and about $1600. The weight would be 1300 lb which is a bit much but probably manageable especially if installed in a truck. If I can run at 350 wH/m at 40 MPH I would be pulling 14kW (18.6 HP) or 58A from the 240V pack, so with Peukert I would have a true 58 Ah or 1 hour of driving at 40 MPH or 40 miles (but probably 30 miles to be safe).

To get about the same performance with LiFePO4 I would need 80 x 60Ah cells which I might be able to get for $100 each including delivery, so $8000. They are about 7lb each for 560lb total. They would also need three times as many high-current interconnects, as well as a more sophisticated BMS, which adds maybe another 50 lb and $800. So 600 lb and $8600.

If I made a combination with 50 Ah FLAs and 30Ah LiFePO4, I would probably spend $4300+$800 or $5100, and weight would be about 650+300 = 950 lb. There is also the complexity factor with two different chemistries.

As for long-term cost, the Lithium cells might last 10 years, and the FLAs 2.5 years, so that makes the lead system $6400 vs $8600. If you factor in the recycle salvage value of lead at $0.27/lb, the cost of a set of FLAs drops $350 to $1250/set or $5000 for 10 years.
http://www.earthworksrecycling.com/prices/index.html

I think LiFePO4 needs to drop to about 1/2 its present cost, and then the numbers look a lot better. I don't know if it really makes sense to use the combination at this point, especially for a high voltage pack.

Today I just happened to pass by a local BatteriesPlus store and I asked them what their price would be for 12V 12Ah SLA batteries such as I recently got on eBay for about $22 each including shipping. I think theirs were about $49/1 and the best they could do for 20 pieces was $35 each. But their 8Ah batteries would be just $16.50 each. So, for my tractor, I could get 240V 8Ah or 1.92 kWh for $330 plus $20 to make the governor happy, so just about $350. I have demonstrated that my small riding mower with me aboard will run at 24V 15A or 360 watts, so I may be able to expect 1 HP or 750 watts to go faster or climb hills or do some work, and at that level I'd draw about 3 amps (0.4C) Peukert says I'll have 5.1 Ah and I should get a run time of about 1.5 hours. That seems pretty good.

If and when I get back to my project (after my scheduled hip replacement April 22), I'll start a build thread. But this seems like a pretty good deal at $0.17/Wh (more realistically about $0.25 with tax and Peukert). The batteries have a 1 year guarantee and should be fine for occasional use, and I think they weigh about 5.25 lb each and an equivalent on eBay is about $17.50. But the batteries from BatteriesPlus are made in USA rather than China so I feel better about that.

For an electric car as an adjunct to lithium cells, the 55 Ah deep cycle battery might be appropriate, and at a list price of $150 it's not bad at $0.23/Wh. In quantity they are probably much less, maybe under $100, or close to the smaller battery's $0.17/Wh. These are 42.5 lb so a 240V 55Ah 13.2 kWh pack would be 850 lb and about $2000.

EDIT: I found out that the Werker brand from BatteriesPlus may be produced by Deka/East Penn but also could be from elsewhere, including some Mexican sources. There are some local reps for Deka/East Penn.
http://www.dekabatteries.com/default.aspx?pageid=844
http://www.dekabatteries.com/ZipSearch.aspx?pageid=843

Their factory is about 2 hours north of me in Lyons, PA.
https://maps.google.com/maps?saddr=Cockeysville,+MD+21030&daddr=Lyon+Station,+PA&hl=en&sll=40.187267,-75.311279&sspn=2.135889,5.218506&geocode=FYFvWgId7IFu-ylngO2kZxLIiTEDNpvSwWL1mg%3BFfe0aQIdggd8-ynF9kpUf9PFiTG6EDsTNxblAw&oq=21030&mra=ls&t=m&z=9