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View Full Version : What replacement battery for H8.5" L8" W4.5" SLA or LIFEPO4 batteries fried by BMS



NonPolluter
06 February 2011, 1616
The Thundersky LIFEPO4 batteries on our EMS Z-6 electric scooter (model changed to Z6000 for 2011) was totally discharged by the Modalis BMS.

We didn't realize that the Modalis BMS draws enough energy to deplete the State of Charge in a month or less.

Upon charging, the cells expanded, breaking many of the battery straps that act as a cage to keep the cells from expanding (apparently an important function.) Those straps aren't welded that well, or at least not strong enough. Now, there are gaps between the cells, as the cell casings have expanded and/or warped.

The pack voltage is nearly 14V and the total system voltage is 55V (on this 48V bike) but when we try to run the motor, the motor just chugs, not moving, and the fuel gauge sits at 1/4 power.

We're guessing that the cells got overcharged somehow. When the battery capacity is diminished, the charger needs to charge less, apparently. Either that, or the fully discharged battery went into thermal runaway under charge.

The BMS is unable to balance the cells now (they used to be within .001V of each other).

We're sick and tired of the LIFEPO4, charger, BMS issues and would like to replace these TS cells with SLA's. (lead acid)

The battery tray will only fit a 16AH Hawker Genesis Pure Lead or 20AH B&B SLA's.

On a side note, the manufacturer Electric Motorsport imho should have pasted a warning label on the bike about the need to charge this scooter weekly. And provided a user guide, even online, with a warning that the expensive batteries can get depleted by the 'stupid' BMS.

Another reason we want to go to lead acid is that the LIFEPO4 acts like a capacitor -- the scooter had good performance only immediately after a charge; wait a day, and some of the horsepower seems to be missing.

NonPolluter
06 February 2011, 1635
Additional information: The SLA batteries would be 13V vs 14V for the Lithium.

Under full throttle, the LIFEPO4 exhibits voltage sag. The TS LIFEPO4 obviously cannot sustain the Z6 current draw (said to be 6000 watts).

The Hawker Genesis Pure Lead batteries have NO HIGH CURRENT LIMIT, either charge or discharge.

Perhaps I should find a way to fit two Hawkers sideways for every 12V pack?

http://www.enersysreservepower.com/documents/US-EP-RS-001_0406.pdf

jazclrint
06 February 2011, 1647
I'm not sure I would blame the LiFePO4 chemistry, as much as it is now pretty clear that TS batteries aren't the best performing batteries out there. I wouldn't recommend SLA but for an interim fix. From what I have read the Headway LiFePO4 batteries perform at a much higher level, but I have no personal experience. Also, LiPo could be an option, as I am sure some will mention. Hopefully other will chime in soon. I'd also get the BMS sorted as well. It sounds like the batteries were over charged.

Hope that's helpful in some way,
Rich

EVcycle
06 February 2011, 1726
I agree with Rich. Many BMS units have been the downfall of the Lipo/Lifepo4 battery issue.

That is why I do not use one. (until I see a good one that is fool proof)
I love the headway's. But that is just one persons opinion.

Do not give up on the non-lead option just yet.

teddillard
07 February 2011, 0448
Interesting information, and good point on the BMS discharge issue. You may want to look at Staab for the SLA source, I had really good luck with them. http://www.staabbattery.com/

I think, from my experience, some good lead batteries are always good for a fix, short term or long, and they always come in handy in one form or another. ( I have some ex-scooter batteries powering my lawnmower at the moment :) )

Ed's so coy... read about his non-BMS BMS idea here: http://www.elmoto.net/showthread.php?227-The-quot-NON-BMS-quot-BMS-Conversion

For some more info on the challenges of Headway packs in particular, see this thread on ES:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=12320


On the TS, I think although the performance of those cells isn't cutting edge, they certainly have had a huge following, and in a scooter they may be a great solution with a good BMS. I'd ditto Ed, and encourage you to look for a good solution to the BMS issue. Other chemistry is going to have the same issues, and as far as LiPo goes, I'd caution you against considering it if you're looking for a hassle-free solution. It's small, light and has a high discharge rate, but they're catastrophically touchy about charge and discharge conditions... :O

Richard230
07 February 2011, 0837
Misery loves company. That is what happened to my Hi Power batteries. I am not sure if you can blame the batteries. My blame was first focused on the Modalis BMS. It was eating my batteries as fast as I could install new ones - before I finally figured out what was happening. It seemed to be something about the "master" board, rather than the slave boards on top of the other battery packs. All of those batteries are still in reasonably good condition (although I have replaced the Modalis BMS with a mini-BMS).

However, I am still having problems with the last two batteries in my pack. I had two swell up last week, but they were numbers 23 and 24 of the pack. When just sitting around for a week, they dropped from 3.3 volts to .4 volt and swelled up - after having ridden the bike for a few miles and not recharging it. However all of the other batteries were just fine and kept their charge, including the other two batteries in the 4-cell group. I have no idea what is going on, but maybe the LiFePo4 prismatic batteries can only deal with a limited amount of voltage or current passing through the batteries. I really have no idea, but that is my latest theory.

teddillard
07 February 2011, 0850
... but maybe the LiFePo4 prismatic batteries can only deal with a limited amount of voltage or current passing through the batteries.

Exactly. That's true of any battery, even lead. Running the pack with the cell at .4V is what fried it and made it swell. If that's what you're saying... not entirely sure. If you'd done that with LiPo it woulda gone boom.


http://www.youtube.com/watch?v=RQjudHKh-bI

Richard230
07 February 2011, 1546
Ted, the two cells that went bad apparently did so while the bike was just sitting around for a week. We had ridden it for several miles trying to fix the stalling problem and checked the voltage on the batteries after our ride. Each cell was showing 3.3 volts and we did not put the pack on the charger after our ride. We didn't check them again when I rode the bike 7 days later, but I immediately knew there was something wrong as I rode down to the end of the block, as the pack voltage went from 80 volts to 74 volts with a few hundred yards. Returning to the shop, we discovered the two fat batteries and replaced them with good ones. But then the stalling returned again. We have no idea what happened to those batteries while the bike sat around the shop for a week. It is all getting very distressing, especially as the BMS was hooked up at the time. The controller is showing a couple of fault codes and my friend plans to call the Sevcon expert this week to try and find out what they mean. Frankly, I would really prefer riding to fiddling. I just hope I can learn something from all this hassle.

teddillard
07 February 2011, 1601
...got it. But for whatever reason they were at low voltage, the cells being at the low voltage and getting tapped is what made them fat. Maybe. :)

Richard230
07 February 2011, 1614
...got it. But for whatever reason they were at low voltage, the cells being at the low voltage and getting tapped is what made them fat. Maybe. :)

I agree. Fat cells are unhappy cells and every fat cell that I have seen has had voltage below 1/2 volt. The odd thing is that you can squeeze them thin again and charge them back up to 3.3 volts. What happens to the Ah capacity when you do that, I have no idea.

chef
07 February 2011, 1930
The Modalis BMS does terrible things to the battery. It allows a cell to hit 4.2v which is far too high for TS. The electrolyte boils at approx 3.65v which causes swelling. The sad thing is that there is minimal capacity increase between 3.65 and 4.2v, but it kills the cell in short order. Worse yet, the Modalis doesn't do cell level LVC (or at best EMS doesn't use that feature). And now it appears that it has a relatively high drain when idle. 1 month to totally discharge an idle cell is awful. EMS really has no business selling LFP bikes with such a faulty BMS.

The problems you experienced have less to do with LFPs and more with a poor implementation. I'm out many grand buying a defective pack design from them. EMS offers no warranty or support on their packs. There are other options, the easiest may be Sky Energy (CALB) cells with the Mini BMS. Sky Energy cells are the same size in many cases.

NonPolluter
07 February 2011, 2144
The Modalis BMS does terrible things to the battery. It allows a cell to hit 4.2v which is far too high for TS. The electrolyte boils at approx 3.65v which causes swelling. The sad thing is that there is minimal capacity increase between 3.65 and 4.2v, but it kills the cell in short order. Worse yet, the Modalis doesn't do cell level LVC (or at best EMS doesn't use that feature). And now it appears that it has a relatively high drain when idle. 1 month to totally discharge an idle cell is awful. EMS really has no business selling LFP bikes with such a faulty BMS.

The problems you experienced have less to do with LFPs and more with a poor implementation. I'm out many grand buying a defective pack design from them. EMS offers no warranty or support on their packs. There are other options, the easiest may be Sky Energy (CALB) cells with the Mini BMS. Sky Energy cells are the same size in many cases.


I'm surprised EMS stays in business with these posts about having their customers pay for "beta testing" their bikes.

We only got less than 700 miles on this Z6 scooter. On time, we experimented by using a Digital Power Supply to manually charge the Thundersky LFP batteries; they were not charged (insufficient power) even at 3.7V (when the power supply drops output to zero amps, as the target voltage had been reached.) Also, the Thundersky website states that a higher voltage is necessary.

So, it is obvious that there is a LACK OF CONCENSUS on a very basic fact: What is the terminal voltage for charging LFP batteries?

I suppose the only two people who have been wildly successful with TS LFP batteries know, since they've driven the first EV to cross the continent: Ricky Gu and Colin Mastin, with the UBC electric bug. However, they used their own custom BMS. They also used three battery chargers, one of which failed en route.

How about using temperature-based sensing to terminate battery charging? The theory is explained by Jack Rickard's blogs -- i.e. 10 degree temperature rise. However, when I charge my many Lithium video light batteries, the "temperature" method doesn't indicate a fully-charged battery.

Also, look up the Thundersky battery opinions by Nap Pippin who built the 130KPH BugE electric trike in Ottawa. He opines that the TS should be rated only 1.5C not 3C due to voltage drop when the SOC is less than 70%.

chef
07 February 2011, 2335
There's been alot of discussion on the TS yahoo group about end voltage. You have to tip-toe around the BMS flame wars, but the general consensus is that any capacity gain above 3.65v is minuscule and will damage the cell. Some go as far as ending at 3.45v and sacrificing ~10% of capacity in order to maximize battery life. Anytime the cell swells, it means the electrolyte has boiled, causing loss of electrolyte and permanent damage to the cell. Supposedly when that happens, metallic lithium forms on the anode and reduces the current flow from the cell. TS reduced their original spec from 4.2v to 4.0v. I think that's way too high, though they may state that for a single cell under very specific controlled conditions which are difficult with a string of cells. For instance, a cell shouldn't see a trickle charge at 4.0v; once it touches that briefly it should not get any more charge. If shunt balancing is employed in a string of cells, the cell could keep receiving juice as it cycles on/off and the float voltage dissipates in between.

TS cells are rated for 2C continuous and 3C for short bursts. It's better to keep the discharge rate as low as possible, but tests have shown that they hold up well to 2C continuous. If you've been drawing 3C continuous, chances are you've degraded the cell. Add to that the overcharge from the Modalis BMS (4.2v) and lack of cell-level LVC (<2.5v) and it's a recipe for disaster. Your cells are damaged and the pack is not performing as well as it could.

CALB cells are rated for 3C continuous if you want more power. Headways would give you even more power as others have stated, though they wouldn't be a drop-in replacement like the CALB cells. Well, physically drop-in replacement, you'd need to adjust or replace the charger and get another BMS (or go BMS-less if you're brave).

Richard230
08 February 2011, 0903
I am reaching the point where I feel like I am throwing money down a black hole. If I can't get my GPR-S back on the road soon, even with reduced performance, I plan to sell it for pennies on the dollar and just wait for Brammo to come out with the Empulse late this year in the hopes that I will get a vehicle properly sorted out and one where the company will stand behind its product and will offer after-purchase warranty service and up-grades, if needed.

frodus
08 February 2011, 0929
get some headways or some TS cells and a decent BMS. You have had bad cells on the bike and keep driving it.

NonPolluter
08 February 2011, 1641
get some headways or some TS cells and a decent BMS. You have had bad cells on the bike and keep driving it.


We need your help, then. Please name te make and model(s) of reliable, proven, functional BMS for LIFEPO4

NonPolluter
08 February 2011, 1644
And, what about battery chargers for 16-24 cell LIFEPO4 packs? Is there a concensus on a reliable make/model? (The Delta-Q chargers used by the successful UBC car club's cross-continent EV trip are too large to carry on electric motorcycles an scooters.)

frodus
08 February 2011, 1723
Manzanita Micro and Elithion both makle a RELIABLE, PROVEN, FUNCTIONAL BMS.

frodus
08 February 2011, 1725
And, what about battery chargers for 16-24 cell LIFEPO4 packs? Is there a concensus on a reliable make/model? (The Delta-Q chargers used by the successful UBC car club's cross-continent EV trip are too large to carry on electric motorcycles an scooters.)

I have a deltaQ on my bike and it fits well. Yes its large, but its sealed and its 1000W.

The problem is, how fast do you want to charge? Wattage and weight/size both go up proportionally. If you want something small and high wattage, you'll have a problem unless you make something custom, or use what others have. What I might suggest is for convenience charging, get something small and light and low watts. Then at home, charge with a DeltaQ.

chef
08 February 2011, 1854
While a smaller charger may be less convenient, the advantage is it's gentler on the cells. Charging at a lower C rate typically prolongs cell life. Depends on the specific battery chemistry and rates relative to the manufacturer specs. It's probably safe to say that charging at 1C is better for the cells than charging at 2C. Going lower helps them last longer though at some point it's insignificant. Going with the 2 charger setup (small on-board, large external) would give you the choice.

harlan
08 February 2011, 1914
I think the majority of the time you would want the fast charging is for opportunity charging on the go, not while at home sleeping. I figure you get the biggest charger you can fit comfortably on board.

I agree with chef about a smaller charger being gentler on the cells, but its not something you'd have to worry about unless you have an extra small battery pack or your charger is powered off 220VAC.

frodus
08 February 2011, 2141
Harlan, are there somewhat "small" chargers he could use that would give between 600 and 1000W output?

I know elcon and DeltaQ do, but they're large.

harlan
08 February 2011, 2300
Harlan, are there somewhat "small" chargers he could use that would give between 600 and 1000W output?

I know elcon and DeltaQ do, but they're large.

I've heard good things about Elite Power Solutions (http://elitepowersolutions.com/products/index.php?cPath=9&osCsid=5e64ab6388b27134f274e388fedbf436) although I've never tried them personally. They have reasonably priced 15A and 20A chargers for a 16-pack that have a smaller footprint then the DeltaQ or Elcon. They also offer a BMS for both TS and GBS cells.