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[Kill3rT0fu]

So zero is having their discontinued product sale. Most things for the older models are half off. Tempting time to consider a power tank, seeing as how I already have the diginow charge tank. However, the almighty Bones Jackson has posted a very informative word of caution on upgrading to power tanks after the main monolith has aged a bit. My bike only has a few thousand miles, and is coming on 5 years old now. I was hoping maybe Zero fixed the software to help offset the issues BJackson pointed out. Is a power tank worth considering right now?

[MVetter]

What I wrote about in that post was specifically a hardware issue. Software aside adding a brand new pack onto a 5 year old pack is a recipe for disaster. That's why I said the following:

In your main battery pack on the Zero, known informally as the Monolith, all the cells are aging at the same rate, in unison. They've all been working together since day 1 and so they're generally all in the same shape. They may, in fact, be in very good shape. But there is measurable degradation. Now you suddenly introduce the Power Tank. Brand new, perfect shape cells. Because these cells are in the best shape, they're more likely to be at the highest state of charge in the pack. The way power requests work in EVs is when you crank the throttle, the bike tries to pull from the highest voltage cells first. Translation: the Power Tank is getting absolutely hammered with requests. And it's 1/4 the size of the main pack getting requests for the pack 4x its size. It's getting sledgehammered.

[Fred]

The way power requests work in EVs is when you crank the throttle, the bike tries to pull from the highest voltage cells first.

Could you explain this? I assume that for cells in series that the same current would be flowing through each cell. For a battery of cells in parallel they would have to be equalised to the same voltage. I can imagine the differences in internal resistance might make a difference to how current flows through parallel cells or voltage between serial cells, but that's about it.

[T.S. Zarathustra]

If you have charge tank, where are you going to put the power tank? Don't they use the same space?

He is a wise person, but I find myself in disagreeing with MVetter regarding the power tank.
The power tank Zero is selling now is probably unused, but not new (new as in made last week/month/year). Calendar aging is a large part of cell degradation. So there is some difference between packs. Not much, probably within few percentage points. If anything, putting power tank in will reduce the load on the cells in the main pack and extend their lifecycle.
The power tank is put in parallel with the original pack. They are all the same voltage because they are connected together.

If we have imaginary battery, with four packs in parallel and add a fifth pack in parallel. You draw 10 kW from the battery. Instead of drawing 2.5 kW from each of the original four packs, you now draw 2 kW from each pack (old and new). There might be 1.95 kW drawn from each of the older cells and 2.2 from the new ones. It's still less current drawn from each series of cells than before you added the power tank.

[Richard230]

I am having a minor issue with the power tank of my 2018S. This year I started to see that the modules would get out of balance when SOC would reach around 80%, but would balance out again (3-4 mV) when charged to 100%. My guess is that the power tank is the problem. The PT in my bike seemed to be a 2017 or 2016 leftover and has a different chemistry than the rest of the modules in the main pack, which had been upgraded that year. I think that difference is finally starting to show up after 7 years.  Fortunately, it doesn't seem to affect the performance of the bike, other than I get the blinking warning light and the instantaneous power graph goes crazy when things are out of balance. 

[Specter]

Lithium technology is going to degrade whether you use it or not.
cycles bring it down a tad more
deep cycles a tad deeper
keeping it stored high hurts it
keeping it stored very low can hurt it too.
temperature is a big issue, especially if storing high.
you get the idea.

in general, putting new cells with older ones, even in parallel sets, the newer ones are going to have higher voltages until they balance but internal resistance creepage  on older cells, is going to make them able to dump less amps per volt drop..so to say, so will beat up the newer cells more on a heavy draw.  if it's a significantly smaller pack, the  c-diff can cause issues.

it's just generally not a recommended practice.  now if you are a little old lady from Pasadena who only drives it to church on Sunday, this may not be much of an issue, but if you use the bike a lot, or hard, it can turn into an issue in very short order.

even if the pack you get is unused, but 3 years old, it's still.. a 3 year old pack.

i am not sure how the bike will balance multiple 'sets' like that but trying to balance old cells with newer ones, if it looks at them as all one big happy pack,  you'll push the older ones and push and push and tear them up after a while trying to match the volts of the new cells.

Aaron

[2020_SRS_Commuter]

I just had a power tank installed with my new LI 14.4 warranty replacement battery pack a few months ago.
The main pack and the power tank do not "empty out" at the same rate. What happens is, always between 15-22% SOC while I'm riding, the bikes acceleration slows like its running out of power, shortly thereafter a banner appears "WARNING POWER PACK DEPLETED" , it disconnects the Power Tank, and then the acceleration goes back to normal and I continue on with just the main pack. The newer manuals for SRS, the 2025 for example, say this is considered normal.
They work in tandem but not a precise parallel.
IDK what this system would do if the main pack was depleted before the power tank. Maybe the reverse?

[MVetter]

The power tank Zero is selling now is probably unused, but not new (new as in made last week/month/year). Calendar aging is a large part of cell degradation.

No argument here that time degrades the pack. But that degradation is eclipsed by constant usage. In a hypothetical scenario with 2 identical battery packs I would take a 10 year old unused battery that was stored at 50% in a cool, dry environment over a 2 year old pack that had 80% DOD for a 5 day workweek 45 weeks per year over that time period.

But in either case I would not introduce a new module on top of a used module. I have written my reasoning clearly and concisely. You are free to disagree with me as is anyone here. My only goal is to try and help people get the best value for their money. I believe what I've written is true and my goal is to just help the Average Joe from throwing their money away on headaches. Power Tanks do not perform as advertised. That is my belief based on research and experience. I can only lead the proverbial horse to water.

[princec]

Neither do Charge Tanks now either grrr

Cas

[zeronimbus]

The power tank Zero is selling now is probably unused, but not new (new as in made last week/month/year). Calendar aging is a large part of cell degradation.

No argument here that time degrades the pack. But that degradation is eclipsed by constant usage. In a hypothetical scenario with 2 identical battery packs I would take a 10 year old unused battery that was stored at 50% in a cool, dry environment over a 2 year old pack that had 80% DOD for a 5 day workweek 45 weeks per year over that time period.

But in either case I would not introduce a new module on top of a used module. I have written my reasoning clearly and concisely. You are free to disagree with me as is anyone here. My only goal is to try and help people get the best value for their money. I believe what I've written is true and my goal is to just help the Average Joe from throwing their money away on headaches. Power Tanks do not perform as advertised. That is my belief based on research and experience. I can only lead the proverbial horse to water.

I have the original power tank and battery on my new 2021 SRS and I have never observed the phenomenon you describe.

[MVetter]

I have the original power tank and battery on my new 2021 SRS and I have never observed the phenomenon you describe.

Based on what you have just written I have absolutely no idea what you just said. Nothing. Please try to describe what you're talking about but make it make sense so a human can understand what you're trying to say.

[NEW2elec]

He's French.
But what he is saying is his SRS which has or came with a Powertank isn't having the problem you described.

Zeronimbus, the issue only comes from an older bike main battery with a new Powertank.  A bike that got it's powertank at purchase or very early on will be fine as all the battery cells are similar.

To the OP I'd skip it unless you have a 2024-25 bike.
I wanted the extra range but I didn't want 45 extra pounds up at the tank area.  I didn't want to pay over $1500 for 20ish extra miles either.

[MVetter]

Zeronimbus, the issue only comes from an older bike main battery with a new Powertank.  A bike that got it's powertank at purchase or very early on will be fine as all the battery cells are similar.

Incorrect. What you said would have been more or less accurate for gen 2 bikes. But gen 3 bikes with the BCB monolith aka the ones that have the capability to charge to 110% from Zero are mismatched. The cell chemistries are different and the operational voltages are different. I don't know if the early gen 3 bikes used reskinned 14.4 bricks but that would be the only saving grace if one of those bikes was sold new with a Power Tank. All the ones mated to BCB packs are screwed.

[T.S. Zarathustra]

The power tank Zero is selling now is probably unused, but not new (new as in made last week/month/year). Calendar aging is a large part of cell degradation.

No argument here that time degrades the pack. But that degradation is eclipsed by constant usage. In a hypothetical scenario with 2 identical battery packs I would take a 10 year old unused battery that was stored at 50% in a cool, dry environment over a 2 year old pack that had 80% DOD for a 5 day workweek 45 weeks per year over that time period.

But in either case I would not introduce a new module on top of a used module. I have written my reasoning clearly and concisely. You are free to disagree with me as is anyone here. My only goal is to try and help people get the best value for their money. I believe what I've written is true and my goal is to just help the Average Joe from throwing their money away on headaches. Power Tanks do not perform as advertised. That is my belief based on research and experience. I can only lead the proverbial horse to water.

I would take the 2 year old pack. As you would assume that you 10 year old pack was stored at 50%, in warehouse with cool, dry environment (and never needed to be topped up due to self discharge). In the same way I would assume that the 2 year old pack (with 450 out of "many thousands" charge cycles) was never overheated or stored empty and always fully charged right before use. So in as good condition as this theoretical daily use 2 year old pack could be.

At the end of the day Voltage is Voltage and Amperage is Amperage. These are the same no matter what the chemistry is. As long as no part of the complete battery pack, including addons, is not overloaded in any way it should be perfectly safe.

I believe I have written my reasoning clearly and concisely. This is based on my education and experience with batteries. That started with Lead Acid, to NiCad, to NiMH, and has expanded when every new chemistry became available. Of course I might be wrong, and everyone is free to have different opinion. My way of advising Average Joe is in a positive way. Pointing out possible options/viewpoints that have not been mentioned previously. The world is too full of negativity. I try not to add to that.

[MVetter]

I can almost hear the screams of the battery engineers as they read that