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IPS 191 Lhotz Battery Upgrade


Slaughthammer

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My thinking was that connecting the balancing connectors first would only join individual cells, whereas the XT60 would join full 16s battery packs. Once some of the cells are already joined, the main jump would be smaller.

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That actually doesn't matter at all. If you have the single cells, the voltage difference is lower, but also the internal cell resistance is lower. As you cascade those cells, voltage difference and resistance gets evenly bigger so that the balancing current is always the same.

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I see. Perhaps it is better to join the XT60 first after all, since the balancing connectors might need a little wiggle that would first make an intermittent connection.

Man this is nerve wrecking! The packs are now within .1V, a few minutes after disconnecting the charger. I'll measure all connectors once more, then it's go time!

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Well that was uneventful. Everything checked fine, so I joined the connectors. No fireworks. Hot glued the connectors in place, put the device together, and it works. Put it in charger and it charges. So everything is as they're supposed to!

Although, I hadn't before checked the temperature from the app while charging. It increased to 54 Celcius in 5 minutes, and still rising, albeit slower. Does that sound normal to you?

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A question. Do I get it right that the old panasonics are still there, and completed with samsungs?

I come from the vaping world, and among the first things we learn never to mix cells of different makes or age. To the point that we "marry" batteries that are supposed to work together, so that they always discharge and charge as a unit. Of course this depends on the capacity of the controlling circuits of balancing the voltages, and the current from the different cells. In vaping gear we're one to four 18650-cells are used, the power draw from each cell is astronomical. For example I pull up to 150W from a single Sony VTC5A, for up to 5 seconds without issue. In a serial setup, I routinely pull about 220W from two cells. That kind of power is of course pulse power, the cells can handle no more than 80-85W continuously. With mismatched cells, I couldn't pull that kind of power safely. One of the cells would/could drop a lot faster, and before I know it I have one cell at 3.5V and the other at 2.5V...

So my question is this, and maybe someone with more experience in how EUCs/BCMs/Controllers handle battery packs can answer this:

Is it safe to mix and match makes and ages of battery packs?

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19 minutes ago, mrelwood said:

Although, I hadn't before checked the temperature from the app while charging. It increased to 54 Celcius in 5 minutes, and still rising, albeit slower. Does that sound normal to you?

That's perfectly normal. The balancer does it's job by drawing current from the cell with the highest voltage, and that energy has to go somewhere....

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Scatcat, yes, both batteries are in use. Each pair of parallel connected original batteries have now a third, new battery in parallel as well.

I'm also a vaper, and while I've been a single cell vaper I have bought the cells in pairs, and have always followed the battery marriage rule. I think it mainly comes down to the current draw, and the fact that the BMS in EUCs balances each paralleled cell unit while charging.

 

Slaughthammer: Thanks, good to know. It's now at 59 Celcius. Is the temp sensor the free cable located on top of the aluminium mainboard box? If so, I'm kind of looking at the charger temperature, which I know does get quite high.

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1 hour ago, mrelwood said:

Scatcat, yes, both batteries are in use. Each pair of parallel connected original batteries have now a third, new battery in parallel as well.

I'm also a vaper, and while I've been a single cell vaper I have bought the cells in pairs, and have always followed the battery marriage rule. I think it mainly comes down to the current draw, and the fact that the BMS in EUCs balances each paralleled cell unit while charging.

 

Slaughthammer: Thanks, good to know. It's now at 59 Celcius. Is the temp sensor the free cable located on top of the aluminium mainboard box? If so, I'm kind of looking at the charger temperature, which I know does get quite high.

I would be more worried about voltage mismatch as they discharge. But maybe the BCM is good for making sure there is no cell going below nominal?

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@Scatcat this hard rule for cell marriage applies mainly for cells connected in series. What we've done here is paralleling a second battery pack to the first one. In parallel configuration, everything balances itself at all times without further ado. We don't draw crazy currents from our battery, which might get us a little trouble also in parallel connections. The important bit is, that each single pack is made from matching cells, because those are cells connected in series. Without the extreme currents, matching doesn't have to be that accurate, so buying the same cells from the same production batch is enough for our application.

@mrelwood, the temperature sensor should be integrated within the main CPU on the controller. The short wire would be the Bluetooth antenna.

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2 hours ago, Slaughthammer said:

@Scatcat this hard rule for cell marriage applies mainly for cells connected in series. What we've done here is paralleling a second battery pack to the first one. In parallel configuration, everything balances itself at all times without further ado. We don't draw crazy currents from our battery, which might get us a little trouble also in parallel connections. The important bit is, that each single pack is made from matching cells, because those are cells connected in series. Without the extreme currents, matching doesn't have to be that accurate, so buying the same cells from the same production batch is enough for our application.

@mrelwood, the temperature sensor should be integrated within the main CPU on the controller. The short wire would be the Bluetooth antenna.

Thanks for the feedback @Slaughthammer. I suppose that is true, as long as each pack has some form of undervoltage-protection. If anyone took my question as criticism of the effort, please don't – I was genuinely curious. My experience with the application of lithium cells in big packs with BCMs is rather limited...

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Oh man. The upgrade is marvellous! Before I had to ease up on uphills at 10km, and slow down to a crawl at 14km. Now I was zooming uphill still after 22km of an already hilly trip! I made it to 27km total. And the torque for uphills is noticeably better than it ever was, even with a full battery.

I'm not getting it to charge to 100% though. Third charging cycle done, and every time it only gets up to 65.28V / 96% (read from the mobile app). After unplugging the charger the display turns to 100%, but still at 65.28V. Is this normal? Is the included charger not able to fully charge a 520Wh battery?

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6 hours ago, mrelwood said:

Oh man. The upgrade is marvellous! Before I had to ease up on uphills at 10km, and slow down to a crawl at 14km. Now I was zooming uphill still after 22km of an already hilly trip! I made it to 27km total. And the torque for uphills is noticeably better than it ever was, even with a full battery.

I'm not getting it to charge to 100% though. Third charging cycle done, and every time it only gets up to 65.28V / 96% (read from the mobile app). After unplugging the charger the display turns to 100%, but still at 65.28V. Is this normal? Is the included charger not able to fully charge a 520Wh battery?

Have you measured the charger output voltage to be the full 67.2V? At least on my wheels, the battery voltage drops a bit (but not that much) after removing the charger, even if doing a full balance charging until about 50mA current running into the packs. The voltages will also drop a bit under load, so might not show full 67.xx if there's any load on them, like when the wheel's turned on. If you're worried about it, might be worth checking the battery voltages themselves, with the wheel turned off so there's no load, the wheel voltage measurements may not always be 100% accurate.

If the BMS in the Lhotz can do active balancing (not only when charged to full), the difference isn't really big though (4.2V per cell vs. 4.08V per cell), somehow I doubt that last about 0.1V gives that much more, and charging to a slightly lower voltage should just give more useable cycles to the batteries.

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The voltage drops from 4.2V to around 4.0xx ... 4.1V pretty much immediately (a few mAh spent) at 2A, faster and to lower voltage with higher currents. Although the mainboard won't draw 2A and the motor uses very little current idling, it could still be due to the cells being under load?

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Thanks esaj! The Lhotz was powered off and connected to a charger for the 65.28V  in the mobile app. When disconnected and powered on, it now shows 65.49V. I'm starting to think it might take a few charge cycles and balancings to get to 100%. If I recall correctly, I did measure the charger to give the full 67.2V when not connected.

It's not an issue regarding usable capacity, there is already a lot more than my legs can handle... And the difference truly is small. Just that after an upgrade like this I get worried about little things I perhaps just didn't notice before. Like the illogical tiltback behavior below 20km/h.

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15 minutes ago, mrelwood said:

Thanks esaj! The Lhotz was powered off and connected to a charger for the 65.28V  in the mobile app. When disconnected and powered on, it now shows 65.49V. I'm starting to think it might take a few charge cycles and balancings to get to 100%. If I recall correctly, I did measure the charger to give the full 67.2V when not connected.

Might be, on the wheels I've had, the BMSs (apparently) only balance at full voltage (4.2V per cell). The first couple of hours of charging might get something like 2-300Wh (for example) into the batteries, but for the voltage to go all the way to around 67.2V and the charge current to go really low (tens of milliamps), it might still take 3-4 hours after that (on a 16S4P / 14Ah total packs), and those last hours only charge a few tens of Wh into the batteries, because the current is so low. The Firewheel-charger I had already changed the light to green when the charging current dropped below 250mA, but it would still take something like a couple of hours to really top up/balance the pack.

 

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On 25/05/2017 at 9:51 AM, Scatcat said:

I suppose that is true, as long as each pack has some form of undervoltage-protection

There is absolutely no issue with paralleling packs of any size/capacity as long as they are exactly the same voltage I.e. For example 16 series liIon cells. If one pack is (say) 4 Amp hour from one manufacturer and the other pack only 1 Amp hour from an entirely different manufacturer then the voltage of the two packs absolutely has to stay exactly the same once they are connected - it cannot do anything else as they are physically connected together at that point. That results in 4 times as much current being supplied by the 4 Amp hour pack as the 1 Amp hour pack.

There are only three dangers to consider: one, of course as discussed,  is that the two (or more) packs being connected must be at the same voltage when connected. The other is that, because the higher capacity pack will supply  the greater current any over current protection mustn't trigger, since the additional pack is usually added to the one already there, this shouldn't ever be an issue as each pack will supply less current than it would have if it was on its own.

The third, possible, problem is if the BMS still has any output protection that will cut power if the voltage gets low, or gets too hot etc. In those circumstances a cascade failure of the packs can occur as once one pack shuts down the other suddenly has to take the entire load and will probably also shut down. Again as long as modern BMS intended for EUC's are used this is VERY unlikely to occur.

Of course under no circumstances should cells of different capacity, age or manufacturer be mixed together in series - that was a major reason for the hoverboard fires a year or two ago, it will result in individual cells going too high and/or too low a voltage faster than a BMS can control.

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5 hours ago, Keith said:

There is absolutely no issue with paralleling packs of any size/capacity as long as they are exactly the same voltage I.e. For example 16 series liIon cells. If one pack is (say) 4 Amp hour from one manufacturer and the other pack only 1 Amp hour from an entirely different manufacturer then the voltage of the two packs absolutely has to stay exactly the same once they are connected - it cannot do anything else as they are physically connected together at that point. That results in 4 times as much current being supplied by the 4 Amp hour pack as the 1 Amp hour pack.

There are only three dangers to consider: one, of course as discussed,  is that the two (or more) packs being connected must be at the same voltage when connected. The other is that, because the higher capacity pack will supply  the greater current any over current protection mustn't trigger, since the additional pack is usually added to the one already there, this shouldn't ever be an issue as each pack will supply less current than it would have if it was on its own.

The third, possible, problem is if the BMS still has any output protection that will cut power if the voltage gets low, or gets too hot etc. In those circumstances a cascade failure of the packs can occur as once one pack shuts down the other suddenly has to take the entire load and will probably also shut down. Again as long as modern BMS intended for EUC's are used this is VERY unlikely to occur.

Of course under no circumstances should cells of different capacity, age or manufacturer be mixed together in series - that was a major reason for the hoverboard fires a year or two ago, it will result in individual cells going too high and/or too low a voltage faster than a BMS can control.

Thanks for the input, that cleared things up.

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I decided to check the mystery of the two thin balancing wires that carried the same voltage than the thick main + cable. I opened up the battery just enough to follow the cables. They are both soldered to the same place as the main +. So no temp protection going on, in that pin atleast.

To make the system theoretically slightly more balanced, I jumpered the leads at the connector. Meaning, now the new battery doesn't circle via the old battery to the last pin. Doubt that it makes any real difference though.

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  • 2 months later...

Just wanted to post a further update: Last week I attended a Skate by Night event in a large city here, with many inline skaters, some skateboarders and five EUC riders. It was a guided group ride of 24 km, and i was initially a bit worried about my battery range. But the average speed was really low, between 10 and 15 kph, so I had a battery level of 65% after the 24 km! Later, I wanted to see how much more mileage I can squeeze out of that battery and went for a leisurely slow ride, trying not to exceed 20 kph... I think I managed to keep my average speed as low as 17 kph, and got another 14 km out of the battery, without getting any battery alarm. That makes 38 km on a single charge (actually a bit more since I did some short extra rides in between, maybe another km in total...)! However, I should mention that I rode in much higher temperatures than my original range test in February.

Nonetheless, slowly I am getting my head more and more around the idea of getting a KS16S... double the power of the Lhotz! No more worries about overleaning!

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That's an incredible range for the Lhotz! I weigh 91kg, but I managed to do 30km. My trips were mostly 24km, past that it's just crawling on. 

On 30/07/2017 at 11:42 PM, Slaughthammer said:

Nonetheless, slowly I am getting my head more and more around the idea of getting a KS16S... double the power of the Lhotz! No more worries about overleaning!

I actually got the KS-16S two weeks ago! My battery modded Lhotz is collecting dust at the moment, but I do have great plans for it later on.

The power available for acceleration and steep hills on the KS-16S is more like three times that of the Lhotz. It is insane! I love a nearby cross-country skiing route that has three very steep inclines. Lhotz couldn't make it by a long shot, while with the 16S I could even accelerate at the steepest spot if I had more traction! Passing bicycles on smooth pavement is so much fun, as soon as the coast is clear and safe, ZAP and I'm past them! Also the pedals on the 16S are way more comfortable than the Lhotz's, even after a succesful extension mod. A 40km trip without a break is no problem!

On the Lhotz I was constantly afraid of bumps, as my 91kg takes a lot to keep upright. The hardest riding mode on the 16S feels surreal. All the bumps and uphills disappear, as the 16S keeps the pedals level no matter what. It's like standing on a train track, and the 16S is much more stable at speed. I do switch between the hard and the medium mode, as the medium doesn't provoke the speedhead in me as much!

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