30Q - 6p build... bike range disappointing - IDEAS?

Batteries, Chargers, and Battery Management Systems.
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brumbrum   100 kW

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by brumbrum » Feb 27 2018 4:47am

It’s not your charger is it?
Correct cutoff? Correct charging procedure for chemistry? Correct charger?

Just a thought.


You can also use your watt meter between the charger and battery to see charging status.
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djbrandonr   10 mW

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Feb 27 2018 6:35pm

999zip999 wrote:
Feb 25 2018 9:16pm
Those kits usually have a 22 amp a 26 amp and a 36 amp controller. So ?
so what? which amp?

no clue, didnt say on the listing nor did it say in the instructions or controller =/

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Feb 27 2018 6:40pm

brumbrum wrote:
Feb 27 2018 4:47am
It’s not your charger is it?
Correct cutoff? Correct charging procedure for chemistry? Correct charger?

Just a thought.


You can also use your watt meter between the charger and battery to see charging status.
nah not the charger... i mean if anyone is bored and wants additional reading homework heres my initial thread about the voltage coming in shy of 42... but i feel thats decent after closer monitoring across all packs... but i will solder both connections on each ond of the watt meter so i can monitor amount of charge and discharge in/out of the packs for reference

https://endless-sphere.com/forums/viewt ... 14&t=92382

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by docw009 » Feb 27 2018 10:45pm

djbrandonr wrote:
Jan 29 2018 1:30pm
one last bump and update... i ran this pack this week while doing deliveries...

most times I run it till its empty..meaning not empty empty as in WOT and no response but more like the pack is low enough to where I need to start pedaling more than necessary at which point I plug in my backup battery... I dont have a precise value but lets say 10% left..

Now Ive used it about 4-5times and the max charge Ive gotten is 41.6v is this good enough? All my other pre-fabbed batteries stop at 42 or just a hair above.

thx!
I still suggest checking the balance voltages again to look for a contact problem. You did say you broke apart a parallel group in that other thread and found one cell out of 7 not charged. Tells me the connection scheme isn't that good.

Wattmeter won't tell you anything other than what you know. That Vruzend pack acts like a 10AH battery. They're worth having though, I find the WH readings are not reproducible, but the AH seem the same.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 07 2018 7:22pm

so heres what we got.. i rode the bike with a full battery till it started to sag as usual... then i took this video of the results with the watt meter from battery to esc... reading about 6.5ah used and average range of 15mi.. with voltmeter still reading about 20% capacity under load...

https://youtu.be/TFvmtX4xgXE

then i brought the battery home for charging... place the watt meter from charger to battery assuming it would read the same amount charged back in (maybe an ignorant assumption based on my limited knowledge)... when the charger first stopped it read about 9ah charged in... but i left the pack plugged in all day (literally) and now were closer to 11ah and climbing...and stopping who knows where...

https://youtu.be/A-TVHlF_nvg

what are the newest thoughts?

thanks

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by mlt34 » Mar 09 2018 2:23am

To me that sounds like its an unbalancing issue. The battery is cutting out when the first cell group gets low. Then when you charge, it fills it up but because of the inbalance, it will start balancing when the first cell group is full, but the cell group that caused the cutout is still low. So now the charger will keep pumping in more Ah while the BMS does its job and balances by letting the low group fill up.

Now for the cause of the inbalance. It could be that not all of the cells are pushed all the way into the cap or are making full contact.

Here's another potential issue. Your battery is still at 37 volts which is a bit over half full. That means that the voltage is sagging to cutoff which is either due to the above problem (not all groups are truly 6p) or it could be due to higher resistance in the pack due to your cell connection method. Did you use 6 bus bars per series connection? And for the + and - terminals, did you use multiple connections or are the discharge connectors just connected to one end of the first and last parallel groups?
Are you planning your first electric bicycle conversion? I wrote a book that teaches beginners everything they need to know about building their own ebike.
Then I wrote the book (literally) on building custom lithium batteries.
I also write for EbikeSchool.com, a site that does mainly how-to style articles and other informational write-ups. Check out our youtube channel for great how-to battery building videos.
Lastly, I run www.Vruzend.com, which sells solderless 18650 battery kits, 18650 cells, li-ion chargers, BMSs and more!

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 09 2018 10:23am

yes on the 6 bus bars per series connection...and I used 2 of the terminal crimps on each end... i may have been able to squeeze 3 on there but it would have been a tight fit IMO...

as the battery has still been sitting on the charger for 2+ days now...watt meter is reading at 14ah now from charger to battery..

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by 999zip999 » Mar 09 2018 10:44am

I have sense wires with a bms or not for a cell. Meter for ez testing.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by amberwolf » Mar 09 2018 4:23pm

I might have missed it, but I still haven't seen a list of voltages measured at your cells or cell groups, which is necessary to check balance of them.

If they are badly unbalanced, then you'll see charging take days or weeks because some cells are way lower than others, so the BMS has to do it's tiny little drain of the already-full ones, then let the low ones catch up that tiny bit, then redo this over and over and over again untl they're all the same voltage.


Then you also have to check the connections of every cell in every group, to make sure they are all participating equally.

A visual check doesn't work--you have to do it electrically.

Either check with an ohmmeter, or better to check with a voltmeter while you are charging or discharging at higher currents.

Measure across the actual connection point, not across the cell itself. If there is any voltage (or resistance) across the connection, there is a problem. Don't touch or put any pressure on the connection point when measuring, or you change the measurement from what it actually is.

If they are not all equal connections, then you essentially have some groups that only have partial capacity, as only some of the cells are providing power, so those groups will drain to empty faster than others, making the whole pack cut out sooner.

This is the behavior you are seeing, and so it is likely this is the cause of that behavior, because of the connection method.


If all connections are equal but groups are still unbalanced, then you probably have bad cells that need to be replaced with ones that are the equal of all the good ones in the pack.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 09 2018 7:11pm

amberwolf wrote:
Mar 09 2018 4:23pm
I might have missed it, but I still haven't seen a list of voltages measured at your cells or cell groups, which is necessary to check balance of them.

https://endless-sphere.com/forums/viewt ... 14&t=92382

id paraphrase it but its not a very long thread...

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by amberwolf » Mar 10 2018 1:45am

Ok, but those are old tests, not ones from it's present status. Still, that thread gives enough info, plus the present results (pack still balancing, AFAICS), to most likely say that the problems found with it then are still there, most likely poor connections between the cells and the interconnects.

It's unlikely to be bad cells, but you can actually check taht by moving cells from one group to another (swapping groups basically), and if the problem follows the cells, there you go. If the problem stays with teh connection hardware....


Testing the interconnects is a PITA, but can be done as noted by measuring voltage drop with higher currents flowing.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 12 2018 10:21am

ok, im gonna unwrap the battery here later, remove all the bus bars and then measure each cell voltage individually (while still in vruzend caps and in full pack form)... should i try and test for resistance or something and how?

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by brumbrum » Mar 12 2018 11:51am

At least you have a lego kit that can be taken apart without damage or stress. It would be much worse an ordeal if you had welded and soldered the pack together.
My NYX and cromotor build
viewtopic.php?f=6&t=74615
My LMX 161 dirt bike build
viewtopic.php?f=6&t=94074

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 12 2018 6:06pm

ok..so i just tore it all down.... Ill post the numbers in just a sec per cell, and string, which were all pretty consistent... BUT
only 1 cell in string 10 wasnt making contact with the cap ends.. but had a charge of 3.8v ... can one cell not making contact with the pack be the achilles heel??

anyways...

all the strings came in between 4.15-4.16v with it being 50/50 across the 10....

and each cell per string tested out to the same value as its respective string...

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by amberwolf » Mar 12 2018 11:06pm

djbrandonr wrote:
Mar 12 2018 10:21am
ok, im gonna unwrap the battery here later, remove all the bus bars and then measure each cell voltage individually (while still in vruzend caps and in full pack form)... should i try and test for resistance or something and how?
Why not just test as already suggested?

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by amberwolf » Mar 12 2018 11:13pm

djbrandonr wrote:
Mar 12 2018 6:06pm
only 1 cell in string 10 wasnt making contact with the cap ends.. but had a charge of 3.8v ... can one cell not making contact with the pack be the achilles heel??
That's kinda the point of what I've been posting, and why I've been trying to get you to check for this problem: if cells are not connected, or have poor connections (which you haven't tested for yet; the method has been described in previous posts), then that group does not have full capacity.

So taht means it reaches full charge sooner than the other groups by however many Ah the cell(s) not connected are, potentially forcing your BMS to balance the pack for a long long time to keep draining that group down while it keeps charging the other groups.

And/or, it means that it reaches full discharge sooner than the other groups by however many Ah the cell(s) not connected are, forcing your BMS to shut off discharge that much sooner.

You'll still need to do the interconnect-resistance tests as described previously, once the pack is reassembled, to find out which cells besides that one have inconsistent and/or poor connections.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 13 2018 3:31pm

amberwolf wrote:
Mar 12 2018 11:13pm
djbrandonr wrote:
Mar 12 2018 6:06pm
only 1 cell in string 10 wasnt making contact with the cap ends.. but had a charge of 3.8v ... can one cell not making contact with the pack be the achilles heel??
That's kinda the point of what I've been posting, and why I've been trying to get you to check for this problem: if cells are not connected, or have poor connections (which you haven't tested for yet; the method has been described in previous posts), then that group does not have full capacity.

You'll still need to do the interconnect-resistance tests as described previously, once the pack is reassembled, to find out which cells besides that one have inconsistent and/or poor connections.
right, sorry, im not trying to be difficult but how exactly am i testing the resistance for for each cell and series connects and are there specific value ranges i should be looking for? where should i be putting the probes for interconnects and series? thanks!

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 15 2018 4:47pm

bump... i re-read yur previous posts mentioning testing but not specific enough details for my noob brain.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by docw009 » Mar 20 2018 10:27am

Your results and what I read about a similar battery in this thread tell me the system is problematic. It's bad contacts and some of your 6P groups are not 6P.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 21 2018 11:12am

docw009 wrote:
Mar 20 2018 10:27am
Your results and what I read about a similar battery in this thread tell me the system is problematic. It's bad contacts and some of your 6P groups are not 6P.

yeah its almost like a perfect twin post about initial balancing. All cells now are balanced and reading the same voltages since last tear down, but actual capacity is still an issue.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by docw009 » Mar 22 2018 9:27am

You'll have to run the battery down again til it triggers LVC. Then do the step-by-step voltage poll. If the contact model is valid, one of the poorly connected groups will read the lowest.

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Re: 30Q - 6p build... bike range disappointing - IDEAS?

Post by djbrandonr » Mar 22 2018 2:16pm

docw009 wrote:
Mar 22 2018 9:27am
You'll have to run the battery down again til it triggers LVC.
Hmmm this is kinda hard being its a delivery bike and trying to run it till its dead but will attempt.. Usually when its sagging hard its around 32v with throttle as it levels out...

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