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

              
   
   
  1. #11
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    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.

  2. #12
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    Quote Originally Posted by chef View Post
    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%.

  3. #13
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    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).

  4. #14
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    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.

  5. #15
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    get some headways or some TS cells and a decent BMS. You have had bad cells on the bike and keep driving it.
    Travis

  6. #16
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    Please name te make and model(s) of reliable, proven, functional BMS for LIFEPO4

    Quote Originally Posted by frodus View Post
    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

  7. #17
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    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.)

  8. #18
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    Manzanita Micro and Elithion both makle a RELIABLE, PROVEN, FUNCTIONAL BMS.
    Travis

  9. #19
    Empulse R #24 frodus's Avatar
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    Quote Originally Posted by NonPolluter View Post
    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.
    Travis

  10. #20
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    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.

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