Lithium Batteries (for the rest of us)

[mbianka]

Originally Posted by goboatingnow

Yes of course, thats because you already have the complex equipment, already, but LI is technically easier to charge, its basically a 1 stage Cv charger.

GBN:
I think he was referring to ease of replacement. Which is a consideration I am concerned about if I were to switch to LI for my electric propulsion system. My plans in a few years probably will include a trip down ICW to the Keys within the next few years. Currently if one or more of my AGM's were to die along the way. I could replace them overnight from a local battery distributor. The battery cost plus one night's dockage and then I on my way again. LithIon customers sometimes wait weeks for their batteries. That's a lot of dock expense. I'm sure delivery times will improve but, for now the cost and lead times still have me waiting on the sidelines for now.

[Hyprdrv]

Just amazing. I wish there was some how a way to just have a positive thread on a subject. I saw this same thing happen when talk of Electric Drive boats was discussed. For several years I was one of a few who actually was doing it. Then there was the Nay Sayers who said it would never work. "Their cost of energy was cheaper using Dino". Now there is a vast improvement in stored energy in the LiPo's and the argument has turned from LA to LI bashing. NOT ONE of the comments above say anything about the fuel savings with the extended discharge of the Li's. The majority of the negative comment makers probably have no idea what has been going on in the DIY EV community for the last 5 years and LiPo batteries.
I'm running 12 AGM's with a Battery monitoring system that monitors and balances my Propulsion pack at 144V and weighting in at 1800 lbs!
I can save over 1/2 ton in weight going with LiPo.
I can run longer under electric drive going with LiPo.
I can charge Faster with LiPo
The cycle life hasn't been determined because they are a new product.
There is still a huge debate whether a BMS system is even needed. Even on 300V + systems. On a simple 12V system? Come on.
The fact that people are arguing the use in a house bank makes me laugh.
The only reason I haven't switched my Propulsion bank to LiPo is the original AGM's are still very healthy. When I need to I will jump on LiPo's and the cost will be determined by how much fuel I saved over the last 5 to 8 years running a Hybrid system and the future savings over the next 10 years running LiPo's.

Steve in Solomons MD

[nimblemotors]

Originally Posted by mbianka

GBN:
I think he was referring to ease of replacement. Which is a consideration I am concerned about if I were to switch to LI for my electric propulsion system. My plans in a few years probably will include a trip down ICW to the Keys within the next few years. Currently if one or more of my AGM's were to die along the way. I could replace them overnight from a local battery distributor. The battery cost plus one night's dockage and then I on my way again. LithIon customers sometimes wait weeks for their batteries. That's a lot of dock expense. I'm sure delivery times will improve but, for now the cost and lead times still have me waiting on the sidelines for now.

I agree, this is a big downside for LiFe at present. Not many sources for retail. It was promising when Johnson Controls was bidding for A123, but that went to the Chinese. Freekin MF'rs, A123 management should be in prison, not enjoying their megayachts. We have been hoping the EV car markers with their volume would change things, but hasn't happened. It was also the case that NiMH never became more available or cheaper, even after Toyota sold millions of NiMH prius batteries, so EV cars with Lithium probably won't change it either.

The good news would be the weight savings of LiFe would mean you could carry some spares without much penalty.
If you've got that clever "Nimble Drop In" Lead/LiFe system (tm) you can always continue to use the Lead buffer until the new Lithiums arrive.

[hellosailor]

Steve-
"The cycle life hasn't been determined because they are a new product."
That's an observation not a reflection on causality. The cycle life probably HAS in fact been determined very well, since each maker states one and it would be actionable fraud if they made that statement based on anything except testing.
What has not been determined, is the real cycle life, as seen and tested under lab settings by an objective party. Like Sandia Labs, or Carnegie Mellon, or Brookhaven, or any of a dozen other places that have some public trust and no commercial interest in the matter.
An astute battery maker, seeking to make sales in the US market, would ship a couple of dozen batteries to some independent facility and simply pay for objective testing. Or donate them to a college and say "put some students on this..." and get similar results.

The US FTC is quick to point out that in their experience, when a vendor only relies on testimonials or statements with no objective tests behind them, there's often some type of lie being sold. Not all the time--but there's very little reason for a vendor not to get objective data to back up their claims.

And the way that the different makers keep squabbling and denigrating each other, of course simply puts the entire concept into question. Bottom line, the folks who make this stuff are responsible for the poor opinion some people have of it. Those makers could very easily blow away the fog, but instead they keep on pumping out more. Hmmm....

Maine-
You got your batteries at a very competitive price, but wasn't that also because Balqon had a mysterious "clearance" sale, which may have been dumping old chemistry or old stock, never really clarified and no longer available?

[deckofficer]

Competition pushes new technologies.

I've been into this since the beginning of EV competition (1/4 mile drag racing), some 20 years ago. In the very beginning we were all using flooded LA, then some of the guys switched to AGM when available, which would produce more peak amps, so they were winning. They still had to contend with the huge voltage sag as the rest of us, but those higher peak amps translated to higher peak hp and their ET's would be lower. Then about 10 years ago A123 cells were available and that changed everything. Nobody running LA had a chance against the early adopters that were using lithium. Today, all racing EVs use lithium batteries. The same benefits that ran LA technology out of competition in racing, are there for others that need to store energy, like us cruisers.

[Greggegner]

Where am I wrong? All the discussion is about the difficulty in in charging the individual cells and keeping them balanced. Why isn't there a charger that charges and manages each cell at 3.x volts, but draws power out in series at 12 volts? Then the cells would be self balancing and not at risk to be over charged. Is this how the battery management systems work?

[ebaugh]

Originally Posted by Greggegner

Where am I wrong? All the discussion is about the difficulty in in charging the individual cells and keeping them balanced. Why isn't there a charger that charges and manages each cell at 3.x volts, but draws power out in series at 12 volts? Then the cells would be self balancing and not at risk to be over charged. Is this how the battery management systems work?

It will work for 4 cells or a 100, but the Electric Car guys are the most mature market and what is practical for a 12V marine problem, does not scale well for many cells. If for no other reason 100 chargers is 100 chances for a failure.

Not what any BMS does yet.

[mcarling]

Originally Posted by ebaugh

It will work for 4 cells or a 100, but the Electric Car guys are the most mature market and what is practical for a 12V marine problem, does not scale well for many cells. If for no other reason 100 chargers is 100 chances for a failure.

If you mean a 320V system with 100 LiFePO4 cells in series, then a battery monitoring system might be justified. However, a battery monitoring system would be even more justified for a 320V system with 150 lead acid cells in series.

I believe there are very few applications where a battery monitoring system is justifiable for a 12V system, whether 4 LiFePO4 cells in series or 6 lead acid cells in series.

As for parallel charging of individual cells, I don't see any justification in either the lead acid or LiFePO4 case. As you point out, adding to the number of potential failure points probably outweighs any likely benefit. In my opinion, start with well balanced cells and don't do anything that would create an imbalance. I have seen no evidence that cells in balance have a tendency to diverge, but I would check them from time to time when doing maintenance.

[manitu]

It's actually oposite. The more cells in serie, the less extra voltage on the rest of the cells, when one dies. With only 4 cells in serie, the charge voltage will rise by 33%. This will shurely kill the rest of the cells in that string. With LiPo or LoCo you risk a serious fire too. Not too familiar with LiFePo.

What I do with the LiCo cells on my bike is this:
Each battery pack is 6 cells in series, 2 in parallel. Total of 21,6v 5200mAh.
I've got 9 of those packs, 3 in parallel, 3 in series. 64,8v, 15,6Ah in total.

What I would like to do, is to charge it with a 18s1p BMS daily and split the battery into 3 18-cell strings like once a month, to balance them all.

For now, I just hook all packs in parallel and charge them together, with a balance charger. But I balance all packs once a month or so. When I do, I exchange weak packs and repair them.

Keep in mind that 70v or so,15Ah of lithium is deadly! When you make propulsion systems, safety first! Contacts you can't touch and safety switches..

.manitu

[manitu]

My point is that it can be done safely, cheap and easy, but not all at once.

Single cell BMS control is expensive. Lots of cells in parallel is a lot of work, once in a while if you want to check all cells.

For a house bank, I would just use a cell-log8 or similar, allways connected, and hook up as many 4/8-cell packs as I needed in parallel.
I would not bother with checking/balancing single cells more than once every other month or so.

Edit: these 4/8- cell packs must have balancing leads paralleled too for parallel balancing to work.
.manitu

[ebaugh]

Originally Posted by manitu

My point is that it can be done safely, cheap and easy, but not all at once.

Single cell BMS control is expensive. Lots of cells in parallel is a lot of work, once in a while if you want to check all cells.

For a house bank, I would just use a cell-log8 or similar, allways connected, and hook up as many 4/8-cell packs as I needed in parallel.
I would not bother with checking/balancing single cells more than once every other month or so.

Edit: these 4/8- cell packs must have balancing leads paralleled too for parallel balancing to work.
.manitu

For a marine house bank, at 12V, I suggest you always maximize into one string all the parallel connections you can, then connect those in series. In my case I have 48 cells, they are connected first 12P then 4S. Then only one CellLog 8 is required. If I did 4S first then 12P, I need 12 CellLog 8's. Unless you want to have two separate banks of LFP for some reason, perhaps space considerations., there is no justification for doing it any other way.

[manitu]

I just saw someone mention large capacity 12v batteries with 4 cells.

I agree that single cells should be paralleled. You can either make big 3,3v packs have 4 in series, or you can make 13,2v batteries with balancing leads between each single cell.

I prefer the last. You can then use a single pack as emergency battery, you can charge and balance a single pack on a standard R/C charger..

But you will need to connect the balancing leads from all packs, together with the cell-log.


If you build 4 big 3,3v batteries, you'll have to rip apart a pack to identify a bad cell.

.manitu

[manitu]

I just realized that the concept of balancing leads has not been mentioned in this thread. All RC battery packs has a standarized balancing lead, with one wire between each single cell in a battery pack. This allows several packs to be paralleled together, cell by cell.

.manitu

[ebaugh]

Originally Posted by manitu

I just saw someone mention large capacity 12v batteries with 4 cells.

I agree that single cells should be paralleled. You can either make big 3,3v packs have 4 in series, or you can make 13,2v batteries with balancing leads between each single cell.

I prefer the last. You can then use a single pack as emergency battery, you can charge and balance a single pack on a standard R/C charger..

But you will need to connect the balancing leads from all packs, together with the cell-log.

.manitu

Me thinks you are living a bit in the radio control world where you use multiple batteries over the course of the day. For a deep cycle house bank, you want to maximize capacity into a single bank to eliminate managing multiple banks. This allows you to minimize depth of discharge and keep the bank in the same 20-90% (or whatever you desire) SOC range. Unless you leave out the "emergency battery" in your scenario, it will go dead with the rest of the bank unless isolated.

You are correct that the cells don't drift much, if at all. Balancing is mostly an installation task. I'm at 200+ cycles now and still in balance. It may be a maintenance task. The purpose of the CellLog is to tell you when, if ever, it needs to be done.

I don't know anyone that's tried it on a big bank, but I think one of the biggest RC chargers could help balance my bank, but it might take awhile. I've had my eye on a PowerLab 8, but more for cell testing than bank balancing.

[daddle]

Paralleled cells balance themselves, no? They can hardly be at different voltages when wired in parallel. (However they can be at different SOH.) That is why the prismatic cells can internally be a battery of several paralled cells. Balance issues arise when cells or batteries are connected in series.