Choosing the best scooter to adapt ?

[jonv]

Yes, it is possible to build a series / parrallel pack. It is more complex, obiviously. But you begin to lose the advantages of prebuilt packs. I'd look for larger capacity prebuilt packs first.
OR take the time to build my own from high quality cells like Headway from EVAssemble http://www.evassemble.com/index.php?mai ... ti4njarbd2

Using the 8400 I am limited to the 2 parallel as opposed 4 s I cant fully use due to voltage increase . According to BM the headaway cells wouldnt fit in the size of case I have for my liteway scooter - remember ? ( And its midsize ) so how will they be any use on an even smaller scooter like the luggie ?

Sry confused..

[Burgerman]

Using the 8400 I am limited to the 2 parallel as opposed 4 s I cant fully use due to voltage increase

????

First you need a scooter.
Then you need to measure the battery compartment to see which cells, which sizes, and what type will allow the largest Ah capacity, adequate C rate, and the correct voltage.
To do that you need to understand the basics of how cells/batteries/BMS or cell balancing chargers work and are configured, and why.

[flagman1776]

Mobility controlers are 24 volts nominal... the voltage needs to be close but it does not need to be exact. Lead acid batteries charge higher... 13+ volts. Those of us with an automotive mindset initially... batteries are a fixed number of cells & that's what we think we are locked into. The high tech world is very different.

So a LiFePO4 pack like the 8400 example, are likely within acceptable tolerance for 2 in Series. The Scooter manufacturers are not very forthcoming with their specifications but if one tested the manufacturer's own Lithium (Lithium Ion, higher volts & subject to fires, but more energy dense) we'd know more about the true voltage range.

I am most familiar with TravelScoot who has offered a Lithium Ion option for some years. (Lithium Ion cells are 3.7V so 7S) gets you to an acceptable 25.4 volts. viewtopic.php?t=1674&p=29471

In MY TravelScoot, I'm running a reworked / salvaged low quality China 10Ah LiFePO4 pack... an 8S3P small cells. Let's do the math: 8 Series at 3.2 Volts is 25.6 Volts. I have no problems with the controler.

[Burgerman]

To give you a truer idea...

Lipo (Lithium Polymer nominal 3.7V) charge at 4.20V per cell, so 7x 4.2V = 29.4V total, and they do maintain that after charge. So you will be driving with 29V to start with. 3.5 lowest level before damage. They burn, are by far the most energy dense, and fragile with short lifespan and serious damage from going over or under voltage. Extremely high C rate.

LiIon (Lithium Ion Nominal 3.6 or 3.7) charge at 4.10, or 4.20V and voltage starts about 29V and drops right down to 2.6 or 7 volts per cell in use. So again 7 cells gives the same 29.4V but rapidly falls to 28.xx in use. Can burn, but safer than above, lower C rate, slightly better lifespan, used in laptops, phones. cameras, toys, travelscoot etc.

Lithium Ion Phosphate (LiFePO4) are by far the longest lasting, and are safeer than lead. You need 8S because they are 3.2V per cell to give a fully charged 28.8V and a 25 to 26V in use. Harder to damage, than the two above, but harder to balance too.

Lead 2x 12V lead batteries, are HEAVY, and store the least power and last about 1 to 2 years... Fully charged are about 26.4V which soon drops to 12.8V or less 25.6 for the two.

Mobility systems designed for lead are quite happy at up to 32V and down to 24V. So all of the above will work...

[flagman1776]

Well said Burgerman. Great overview.
One detail is that for what ever reason, TravelScoot chose to use a 7S (7 Series) LI system which LOWERS the voltage as I stated. 7 (series) X 3.6 V = 25.2 Volts

The electronic workings are different between a system using a BMS built in board & a smart charger... but both are wired with each cell or parrallel group having a small wire to a balance connector.
In the first case, the balance connector goes to the BMS board which balances the cell groups... the charger feeds the BMS board.
In the second case, the balance connector goes to the smart charger (could be combined in a single plug) with the main charge leads) which balances the cell groups.

Now I will say that if you plan to travel by air, your hand may beforced to a commercially built & certified product even if it is inferior.

[jonv]

Well said Burgerman. Great overview.
One detail is that for what ever reason, TravelScoot chose to use a 7S (7 Series) LI system which LOWERS the voltage as I stated. 7 (series) X 3.6 V = 25.2 Volts

The electronic workings are different between a system using a BMS built in board & a smart charger... but both are wired with each cell or parrallel group having a small wire to a balance connector.
In the first case, the balance connector goes to the BMS board which balances the cell groups... the charger feeds the BMS board.
In the second case, the balance connector goes to the smart charger (could be combined in a single plug) with the main charge leads) which balances the cell groups.

Now I will say that if you plan to travel by air, your hand may beforced to a commercially built & certified product even if it is inferior.

i dont know what 2 do.. I am so sensitive to vehicle vibrations I am worried about travelling . I used 7" of stratocell foam 2 days agos ( which used to work WELL ) to sit on and I still detriorated even though i couldnt feel it

Is there a kevlar type material to stop vibration dead ?

anything ?

I have ehlers danlos syndrome uc ..its a bloody nightmare

[Burgerman]

You lost me...

[flagman1776]

Kevlar is TOUGH material, highly puncture resistant. That would not seem useful for vibration cushioning. This is such an individual problem, that only someone with a similar issue could give suggestions.
7 inches of foam is a LOT of foam. Not all foam is created equal and foam dies change with age.
I think that burgerman's oversized tires at low pressure would cushion a lot of life's bumps BUT such large tires require a custom chair. They could be added to a standard scooter or chair but would increase width so much that it would not go through doorways. Air-filled tires, not foam filled hard things... would be softer riding.
Some suspension might help or even rubber flex mounts between the seat & the frame.
Maybe softer air cushions as your seating would absorb vibrations.

I don'tthink there is one "right" answer. It probably will always be an imperfect conpromise.

[Mussels]

After much commuting by pushbike I found the most effective vibration dampener is soft pneumatic tyres. Not sure how scooters will be affected but I needed to get fat tyres on bikes to make sure rolling resistance stayed OK and I didn't hit the rims on bumps.

[scootntootn]

Very interesting thread.

Is there a way to cobble together several premade packs, in such a way one could fly with it without the whole thing being confiscated?

Or even if not, is there a way for me to easily cobble together several packs to end up with something close to 12v 18Ah x2. Do they have a BMS?

I needed batteries NOW, so ordered AGM now. But if I end up using that little scooter more than anticipated, LiFePo4 looks enticing. If nothing else to extend the range of my scooter. With new batteries it’s got enough juice, but with my last pair it didn’t have enough juice for my entire shopping trip the last few times I tried (it’s a many hours trip, with some distance between malls).

[Scooterman]

Lithium Ion Phosphate (LiFePO4) . Harder to damage, than the two above, but harder to balance too.

Why is this?

Higher resist than lipo or li-ion?

[Burgerman]

No it is because during the 99 percent down to say 50% charge, the voltage varies more by individual cell manufacturing variation, or by 1 or 2 degrees in temperature than it does by state of charge. Add to this that all cell balancers, and all BMS etc are not all that accurate across the 8 voltage sensors. So that means any attempt to balance the cells, at under 99% full, or 3.45V which is the same thing, actually UNBALANCES the cells. Then theres self discharge, which hapens all day every day used or otherwise. And its very variable on LiFePO4 chemistry. So they go out of balance all by themselves over time. A day is some time. So balance will never be perfect even charged daily. And yes it takes longer too because of impedance being higher than lico, or lipo type cells.

[Scooterman]

I see, it's a shame that

That's why as you say the BattGo can't balance lifepo4, as it balances according to voltage, and voltage doesn't represent SoC below 99% (3.45v). So battgo matches/balances cell voltage (eventually...) but unbalances according to SoC.

Got it

Learning all the time...

[Burgerman]

Learning all the time...

At least you do. Some dont! Yes, in some cases the voltage actually climbs as a cell discharges. Because its resistance warms it as you drive or charge (or because one group are in the sun!) So its voltage increases as you discharge it. So any attempt to lower its state of charge by discharging, causes the voltage to rise... So rinse and repeat for a few hours.

Balance only above 3.45V or even at CV only. Or it may spend ages carefully UNBALANCING itself.