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Discussion Starter #1 (Edited)
I'm starting an experiment to test the effects of using lithium LiFePO4 cells in parallel with cheapo lead acid batteries.

Lithiums are 40 AH Calbs, and they'll be boosting 29HMs (formerly known as 29DC) and GC8s. My current frankenpack consists of 3 29HMs and 11 GC8s.

Phase 1 of FLHE will put 8 calbs in parallel with 2 29HMs with a JLD404 to monitor AH usage and control charging. The calbs will be charged in parallel with the floodies until approx entering gassing phase where the JLD will cut the lithium contactor while the floodies finish their cycle. 1 29HM will remain unboosted as a control.

Phase 2 will add 8 calbs in parallel with 3 GC8s and tested as above.

The experiment will try to gain info about how the current sharing works out as well as how lead cycle life can be prolonged with the aid of a lithium booster.

A successful experiment would demonstrate an increase in lead cycle life sufficient to justify the cost of the lithium booster.
 

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as much as i would like to see this; I'm thinking it might be a disaster for the calbs's because the chemistry's of the different batteries just don't match up. perhaps a series string of fla then calb pack then fla and parallel those strings.
 

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As long as you don't over or under charge the lithium cells you will be fine. I had a disaster with my Prius booster pack to my lead acids. Prius cells over charged. I did not have a smart charger which would be important in the case of using different batteries. Lithium charge is nearly the same as lead acid except the balancing cycle and float cycle.

You going to use a lithium charger or lead acid charger?
 

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Discussion Starter #4
poitrsko: not sure what you mean by flood calb flood. I'll post a circuit diagram later to better explain my plan

pete: I'll be using the lead charger I currently have. They'll charge in parallel to mostly offset the unbalancing caused by discharging in parallel, and the JLD will cut them out before they get too high.

I probably want them to charge to about 3.5V/cell (14V on the lead they're boosting) so they'll rest around 3.3. Since they have to match the lead they'll probably live at a high 3.2-3.3 all the time.

I want to do a DIY lithium charger someday, but likely not until just before switching to full lithium.
 

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Parallel anything gets interesting. Paralleling different power sources is even more. But, after charging them separately , when that isolating contractor cuts back in, the fun really starts.

One will be charging the other, always, until equilibrium is met.

Series is easier. Just monitor the smallest capacity cell and charge/discharge to that.

Miz
 

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Discussion Starter #7
Yes, the plan is to have the contactor cut out when the cells are at a voltage that will let them rest equal to the lead's resting voltage. I'm sure it will take some tweaking.

One of the points of this is to see how things behave in parallel. As for upgrades, series is not even an option without either two new chargers or a new charger and motor controller.

I've had some repairs that set me back some, so I still need better baseline records, and I decided I need some more meters before I'm ready to go.
 

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Parallel anything gets interesting. Paralleling different power sources is even more. But, after charging them separately , when that isolating contractor cuts back in, the fun really starts.

One will be charging the other, always, until equilibrium is met.

Series is easier. Just monitor the smallest capacity cell and charge/discharge to that.

Miz
You can parallel Lead Acid and you can Parallel Lithium but I would not mix chemistries in series or parallel.
 

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You can parallel Lead Acid and you can Parallel Lithium but I would not mix chemistries in series or parallel.
Parallel works fine but you have to know what you are doing.

I wouldn't consider this as a solution for anything because you still have lead acid batteries in your car and you still have all of their disadvantages, namely the low energy density and high weight. The only thing people see with LA is the illusion of saving money.
 

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Parallel works fine but you have to know what you are doing.

I wouldn't consider this as a solution for anything because you still have lead acid batteries in your car and you still have all of their disadvantages, namely the low energy density and high weight. The only thing people see with LA is the illusion of saving money.
Lead along side NiMH is not a good idea. Yes it can be done but introduces a high level of complex issues.

I agree that people see the illusion of saving money. It is that illusion that stops EV's from becoming main stream. I am for breaking the illusion. I will break 13,000 miles today on my Leaf. I'd say it has fully integrated itself into society just fine. Most everyone has more than one vehicle and most driving is done commuting to and from work. Like me I commute and work 5 days a week and two days off. I do go places that negate my use of the Leaf but not often. It is then that we take the gasser. We have spent so much less in fuel it is amazing. I have now gotten our TDI back on the road so the Wife will be driving that for awhile. 46 mpg is pretty good and I may try bio fuel at home now that one tank will last at least a couple months for my wife's commute.

Electric is it and Lithium is king. Cost IS less.
 

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As long as your contactor cuts out at the right voltage, I believe your charge method will work fine. My guess is the lithium will consume the majority of the charge current due to its lower IR.

..., and I decided I need some more meters before I'm ready to go.
Not sure what you have in mind for meters, but I have one of these Doc Wattson Meters, and its pretty neat for the price. It doesn't log, so you have to manually record data at regular intervals. But for tests like this, you'll probably be monitoring it anyway.

http://www.powerwerx.com/digital-meters/doc-wattson-meter-dc-inline.html

I ended up finding one on eBay a while back, for slightly cheaper. If you google it, there seems to be more online stores carrying them now.
 

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Discussion Starter #12
I have a JLD404 for measuring amps through the CALBs, and I'll compare that to the crappy westach reading the full pack. I'll also have a bunch of cheap DVMs on individual batteries/groups.
 

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Discussion Starter #15 (Edited)
So...I've finally managed to squeeze a few commutes in between the thunderstorms.

Before starting the experiment, the floodies (HM29) measured at ~12 mΩ. The CALBs measure at 6 mΩ. So far, current sharing seems to be close to expected based on those numbers, with the CALBs passing 65%

With the batteries typically within 1/5th of a volt when connecting or coming off a cruise, current between strings starts around 10A, and decreases to ~5A within a few seconds, then tapering down to 2 within a minute or two. I never gave it a chance to fully equalize, will have to see how long that takes.

With my current charge level the CALBs were almost always feeding the floodies, though it was running backwards at least once. I need to tweak the charge level to try to minimize that.

Voltage sag for the boosted batteries was dramatically improved.

I really need another JLD or two to get better data, and will look into accessing the data port for some automated logging as well.
 

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I like experiments like this. The idea may go against conventional wisdom, but you have made some thoughtful approximations and it seems like it may work for you.

My idea was to have complete battery modules containing any number of cells of the same chemistry, and including all the BMS and charging and protection circuitry in the module, and also boosting (or bucking) the voltage so that the output is a consistent value, such as 144V. Each module would be individually rated for a certain kW-Hr and could have built-in displays showing the approximate state of charge and cycle data and expected end-of-life. But such a device would need a very efficient DC-DC converter or buck-boost circuit. It might be useful for small vehicles where you might be able to use one 2 kW-Hr pack with 320 VDC output for a 2 HP riding mower or small tractor with a 3-phase motor.

Keep up the good work. Your monitor panel is impressive! ;)
 

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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.
 

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Discussion Starter #19
Thanks. I do need to look into that or a celllogish method to store the data. My meters are great for watching, but it's a a bit of work to take samples from a video.

The JLD404's awesome, after having it for months I don't know how I ever drove without it. Mine's a bit gimpy, so I need to send it in for replacement, but I may get another one as well, haven't decided. It's only $70 from the vendor, $100 if you count the shunt and a DC-DC if you want that. It can do logging as well, but I haven't messed with that yet.
 

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Awesome! Love the expirement, regardless of the outcome. Think out of the box and take risks, that's what got us here in the first place isn't it?
 
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