Floodie / Lithium hybrid battery experiment

40198 Views 93 Replies 16 Participants Last post by dougingraham, May 24, 2013

Ziggythewiz

Discussion Starter · May 25, 2012 (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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41 - 60 of 94 Posts

Jamie EV

· #41 · Oct 8, 2012

dtbaker said:
lead sags more under high load, and suffers from peukart's.

I see...and it's heavy....so that's lead's weakness....what's Lithium's?

Ziggythewiz

Discussion Starter · #42 · Oct 8, 2012

Lithium can take higher C rates, but the floodies have over 3x the (sticker) capacity. I want them to share somewhere between 5:5 and 2.5:5 F:L. 3:5 would be ideal.

Ziggythewiz

Discussion Starter · #43 · Oct 8, 2012

Jamie EV said:
I see...and it's heavy....so that's lead's weakness....what's Lithium's?

Just $$$ and potential damage if overcharged/discharged. In my setup the lead makes it impossible to overdischarge the lithium (without trying) and the JLDs will prevent overcharge.

Jamie EV

· #44 · Oct 8, 2012

Ziggythewiz said:
Just $$$ and potential damage if overcharged/discharged. In my setup the lead makes it impossible to overdischarge the lithium (without trying) and the JLDs will prevent overcharge.

Sweet! In theory that's a marriage made in heaven. What's a JLD? I know dumb question...

Ziggythewiz

Discussion Starter · #45 · Oct 8, 2012

In (my) theory it's a good way to get from lead to lithium without the huge upfront cost. If you have the money, straight LiFePO4 is the way to go.

The JLD404 is a smart meter that reads V, A, counts AH, and has two programmable relays. At $65 I think it's the coolest device known to EVdom.

Jamie EV

· #46 · Oct 8, 2012

Good price for sure.
I think I saw a 96 volt array of lithium cells (each 100ah) including bms and charger for like 5000. that's not bad considering the cost of Valence cells....yikes! Don't know if they are crap or not.

Jamie EV

· #47 · Oct 9, 2012

Ziggythewiz said:
$5000 would get you a nice 128V 100AH set of CALBs.

Might have been cheaper. I just thought the fact that included bms and charger was good.

Ziggythewiz

Discussion Starter · #48 · Oct 31, 2012

Finally got some new meters in, so I can rebuild my gauge panel without needing so many isolated DC-DCs (I managed to lose 2 and fried another one (that's 3 I've fried)).

Using 3 of these 50V DVMs instead of 2 99V meters will also give me more insight to the booster pack, since ~1/3 is SEs and ~2/3 is CAs.

Pack is working fine but I haven't pushed it for range or current. Surprisingly the lithiums seemed more affected by the cold snap we had the last few days than the floodies. Hopefully I can get a box on em this week and then make a couple for the floodies in the next couple weeks.

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Jamie EV

· #49 · Nov 1, 2012

How cold was cold? Does charging not heat them up sufficiently?

Ziggythewiz

Discussion Starter · #50 · Nov 1, 2012

Low 40's. They're done charging by midnight, so unless I plug em back in in the morning they're ambient (garaged most of this week) by the time I leave. Once I get em in some insulated boxes they should hold some of the charging warmth till morning.

Jamie EV

· #51 · Nov 1, 2012

it can't take much heating to keep the inside of a batt box warm. I mean how many btus could it need? Has anyone calculated that? How many watts? I would imagine you could use some of that electric radiant in floor heating stuff to do it. That would be compatible. I think it runs on 120volts....that small amount wouldn't draw much.

You could line your boxes with that maybe. I would be worried about the temp differential between the warm side and cold side of the batteries though. Maybe use spacing to get convection in there too?

Ziggythewiz

Discussion Starter · #52 · Nov 1, 2012

I don't plan to add any heating. Just insulating and garaging should be good enough. After the first cold night when the lithium seemed saggy I finished getting the garage cleared enough to fit the bug in and no issues since. Now it's back in the 60s at night so no worries for a couple weeks.

Jamie EV

· #53 · Nov 1, 2012

That's not cold at all. My winters get down to -30 C below or so. -40 C on a bad day.

Jamie EV

· #54 · Nov 1, 2012

Average of about -15 in January. I would install a heater as a "just in case" precaution. It probably won't ever have to click on.

Ziggythewiz

Discussion Starter · #55 · Nov 1, 2012

Yeah, just non-winter Houston cold. That's why I was surprised by the saggy lithium. I expected the lead to be super saggy at those temps, but it handled it better, though I don't know how much on either because I don't have all my meters on.

I don't plan to waste time, effort, and money on something I'll likely never need. I've got plenty of other things I don't have time for.

dougingraham

· #56 · Nov 1, 2012

Jamie EV said:
You could line your boxes with that maybe. I would be worried about the temp differential between the warm side and cold side of the batteries though. Maybe use spacing to get convection in there too?

Probably you don't need to worry about differences across a cell. If you think about it these batteries are a stack of copper and aluminum foils with a thin electrical insulator saturated with electrolyte between them. The case might be different temps from one side to the other but there won't be much difference from one side of the internals to the other for very long.

It gets very cold here on occasion (I have seen -40 a couple of times in the last 38 years). I insulated my battery boxes (A little better than R3) and if it proves to be a problem I will put a heat plate under the cells. I expect a few jackrabbit starts will warm them up enough though. Heating this last summer was not an issue. The most I saw was about 10 degrees above ambient and with the cells in the insulated box they stayed cooler than the inside of the car when it was sitting in the sun. What I am trying to say is that the battery temps vary less than the outside air temp.

Jamie EV

· #57 · Nov 2, 2012

dougingraham said:
Probably you don't need to worry about differences across a cell. If you think about it these batteries are a stack of copper and aluminum foils with a thin electrical insulator saturated with electrolyte between them. The case might be different temps from one side to the other but there won't be much difference from one side of the internals to the other for very long.

It gets very cold here on occasion (I have seen -40 a couple of times in the last 38 years). I insulated my battery boxes (A little better than R3) and if it proves to be a problem I will put a heat plate under the cells. I expect a few jackrabbit starts will warm them up enough though. Heating this last summer was not an issue. The most I saw was about 10 degrees above ambient and with the cells in the insulated box they stayed cooler than the inside of the car when it was sitting in the sun. What I am trying to say is that the battery temps vary less than the outside air temp.

That's good to know. I guess batt insulation can solve a lot of problems for extreme weather. R3 is next to nothing. If that's all that is needed, I'm glad.

Ziggythewiz

Discussion Starter · #58 · Nov 10, 2012

Booster bonus feature:

Doing my semi-annual battery watering I noticed a a very loose terminal on a floodie. It was very discolored from the heat, and there were a couple spots where molten lead had formed. It it weren't for the redundancy provided by the booster pack the whole terminal would have blown off.

Also good that I happened to be watering today to notice.

Jamie EV

· #59 · Nov 12, 2012

Ziggythewiz said:
Booster bonus feature:

Doing my semi-annual battery watering I noticed a a very loose terminal on a floodie. It was very discolored from the heat, and there were a couple spots where molten lead had formed. It it weren't for the redundancy provided by the booster pack the whole terminal would have blown off. Also good that I happened to be watering today to notice.

Is there anything negative that you've observed so far?

Ziggythewiz

Discussion Starter · #60 · Nov 13, 2012

Jamie EV said:
Is there anything negative that you've observed so far?

Just that having a half lithium pack really makes me want a full lithium pack.

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