PINNED - Lithium battery conversion/info

[LROBBINS]

Whatever arrangement is most convenient for laying out the wires in the space available: pairs of cells in parallel then wired 8s pairs in series, or two 8s packs then wired in parallel.

[fishinjunky]

Whatever arrangement is most convenient for laying out the wires in the space available: pairs of cells in parallel then wired 8s pairs in series, or two 8s packs then wired in parallel.

Thanks,
It's a bit of a challenging battery space an there is a devider between the two lead batteries. I'll probably remove as much as I can from the battery space for a little more room. If I'm going to invest in lifepo4 for my older chair I'm tempted to put new motors in it also. Or just finally let go of the old mwd.

[p22se]

Has anyone tried the Heltec 5amp active balancers? I am looking at building a 200ah pack and using the active balancer and a normal 20amp(ish) lipo4 charger. Am I crazy in thinking this will work?

[Burgerman]

Not crazy. But it wont work well. It thinks that voltage = state of charge. Sometimes thats correct. Such as when at rest, without load, and only when above 3.4V or below say 2.9V per cell. ALL of the rest of the time while in use the voltage at any time may be a few mV higher or lower while still accurately balanced by capacity. So it will spend much of the day UNBALANCING the pack trying to make the voltage exactly the same between cells. When it already is balanced. Only for that to cause issues when charged. That would wirk with lithium ion, or lipo, not lfp cells. And when you do charge at above that balancers max current, then the cells that are at 100% by capacity will leap up above the 3.6v limit and keep on going up. And nothing to prevent that. So at a typical charge rate of 30 to 40A or even that low 20A, the full cells will keep on climbing way above 3.6v. As theres nothing to stop this.

IF you can program this balancer to only balance ABOVE 3.45V. And only charge at a rate below that which the balancer can safely remove, say 3A to leave some headroom then it would work. And take 3 days to charge.

[p22se]

I see, thank you for your advice, Burgerman, it is very much appreciated.

[fishinjunky]

I'm curious. I've been working out the numbers with milage terrain an ah returned for determining range. But what I'm noticing is that I'm developing an instinct for the range. The numbers aren't very accurate because of all the variables but by paying attention I have a sense for the range. Have you guys also developed this "range instinct" for your lifepo4

[shirley_hkg]

No. You don't and can't add up for a dozen days mileage .

A voltmetre is much better and accurate.

[Burgerman]

I just know that I wear out first!

[Scooterman]

No. You don't and can't add up for a dozen days mileage .

You can on a scooter

A voltmetre is much better and accurate.

I have both


Scooter dashboard looks like cockpit of fighter jet, it's already fly by wire. Next upgrade is a heads up display!

BTW LCD voltmeter is SO much better than LED outdoors, cos bright sunligh light washes out LED display and you can't read the numbers.

[foghornleghorn]

I'm curious. I've been working out the numbers with mileage terrain an ah returned for determining range. But what I'm noticing is that I'm developing an instinct for the range. The numbers aren't very accurate because of all the variables but by paying attention I have a sense for the range. Have you guys also developed this "range instinct" for your lifepo4

What I see is-
• Tarmac or decent quality pavement 2Ah per mile.
• Unsurfaced road or a dry footpath 3Ah per mile.
• Muddy or very rough ground 4Ah+ per mile.

A better measure for a rough guess on how much used is time. Rough ground I cover much less distance over time but use about the same Ah in an hour as on a road.

[Scooterman]

• Tarmac or decent quality pavement 2Ah per mile.

I work on an average of 2Ah/mile on the big scooter.

1.75Ah on a long run in the summer.

2.5-3.0+ Ah/mile on short late autumn/early spring rides.

[Burgerman]

I think at best this is a ver approx guestimate.

I can take out a fully charged lead battery doing an hours and a half housework or leaf blower in the drive/garden. So it shows the last amber lights and so that the power module overheats and we are forced to wait.

Then if we go out into the street the battery id almost used up and I covered probably a mile.
Also going along a level flat surface like a runway, shopping centre, car park, etc uses very little. Going along a cambered road edge designed to dain water takes FIVE TIMES the current. Meaning you go 1/5th as far per Ah. Or use 10Ah per mile. So in a tank steered device, your mileage may vary... Literally.

[fishinjunky]

i feel comfortable saying my heavy offroad range for my 200ah pack is around 25miles and moderate usage range is around 30 miles for the bounder and thats being very conservative. An that is a huge difference compared to my 6 mile offroad or 8 mile onroad range with lead batteries. Im have a absolute blast with all the extra range an power its badass

[Scooterman]

https://www.aliexpress.com/item/1005004 ... 9807%21rec

Anyone tried this style of links?

[fishinjunky]

https://www.aliexpress.com/item/1005004111160334.html?spm=a2g0o.detail.0.0.96545f43NETtUY&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.274681.0&scm_id=1007.13339.274681.0&scm-url=1007.13339.274681.0&pvid=159fd1ce-7409-482d-bac7-78a2b9a7b57c&_t=gps-id:pcDetailBottomMoreThisSeller,scm-url:1007.13339.274681.0,pvid:159fd1ce-7409-482d-bac7-78a2b9a7b57c,tpp_buckets:668%232846%238109%231935&pdp_ext_f=%7B%22sku_id%22%3A%2212000028066689807%22%2C%22sceneId%22%3A%223339%22%7D&pdp_npi=2%40dis%21GBP%21%2128.82%21%21%21%21%21%400b0a23a716535689428973560ebbab%2112000028066689807%21rec

Anyone tried this style of links?

I would recommend bus cables always as first option but as a very last resort I would use these Flexible busbars

The ones you linked are not insulated an the holes on those don't fit right

These are the ones I used
US $3.90 | Insulated Flexible Bus Bar Flat Copper Busbar 3mm 300A for 3.2V 3.7V 100Ah 200Ah 280Ah 320Ah Battery Pcak Parts with Cu Ni
https://a.aliexpress.com/_mPRqY4A

[Burgerman]

Are they easily flexible and not solid one bit?

Like these: https://www.aliexpress.com/item/3256803787045526.html

[Scooterman]

I would recommend bus cables always as first option

I do agree, but it is a faff crimping/soldering lugs onto the ends of all the cable links. Especially with 16 cells, you need SOOOOOOOOOOOOOOOOO many links

I know you don't agree but next time I build a pack I'm going to give this style of link a go. The lack of insulation problem only really matters if you drop a spanner on top off the cells. Something I would never do!!!

Screenshot 2022-05-26 at 13.44.34.png (138.87 KiB) Viewed 1580 times

But it could be rectified with some lightweight shrink sleeve mildly shrunk. Like when you put accidentally your wool socks in the machine along with your nylons/acrylics on too hot a wash.

[Vitolds]

Are they easily flexible and not solid one bit?

Like these: https://www.aliexpress.com/item/3256803787045526.html

2mm is very flexible. I do these myself.

[fishinjunky]

I would recommend bus cables always as first option

I do agree, but it is a faff crimping/soldering lugs onto the ends of all the cable links. Especially with 16 cells, you need SOOOOOOOOOOOOOOOOO many links

I know you don't agree but next time I build a pack I'm going to give this style of link a go. The lack of insulation problem only really matters if you drop a spanner on top off the cells. Something I would never do!!!

Screenshot 2022-05-26 at 13.44.34.png

But it could be rectified with some lightweight shrink sleeve mildly shrunk. Like when you put accidentally your wool socks in the machine along with your nylons/acrylics on too hot a wash.

i just worry about the longevity of the flexible busbars including the type i used. Maybe they will be fine but maybe not. This winter i plan to reevaluate my space on top my pack an try to fit bus cables replacing the flexible busbars. Do the busbars you posted come in different lengths? if you can get them in different lengths an if you heat shrink them they should be fine. There just no data on these flexible busbars or on the ones i used in our application for packs in our chairs "lots of vibration" is yours 48v?

[fishinjunky]

looks like the new standard size lifepo4 is now 230ah / 240ah instead of 200ah to replace a set of group 24 lead batteries. The 230ah cells measurements are same as the 200ah cells im seeing. Any one have 230ah or 240ah cells replacing your group 24 batteries?

[fishinjunky]

is the resting voltage of a fully charged lifepo4 cell 3.3v an the resting voltage of a fully charged 8s pack 26.4?

[Vitolds]

flexible copper bus has been used for many years in cars, connecting the mass of the body - the engine.
You can quickly buy this braided copper bar at any auto shop. You also need a cable lug (Copper sleeve 50mm2 tinned for crimping, for wire 50 squares), if you use a copper bus 15mm wide and 2mm thick.
Cut to desired length and crimp. Drill holes slowly. Braided copper bar 15 mm wide and 2 mm thick is 16 square or 4 AWG wire

[fishinjunky]

flexible copper bus has been used for many years in cars, connecting the mass of the body - the engine.
You can quickly buy this braided copper bar at any auto shop. You also need a cable lug (Copper sleeve 50mm2 tinned for crimping, for wire 50 squares), if you use a copper bus 15mm wide and 2mm thick.
Cut to desired length and crimp. Drill holes slowly. Braided copper bar 15 mm wide and 2 mm thick is 16 square or 4 AWG wire

That would be nice you get flexibility and shorter length

[Vitolds]

no problem, make any length by cutting the wicker bar

[Vitolds]

Here are the parts for making
https://aliexpress.ru/item/100500429040 ... 4aa6Lp8ExT
GT-G-50 https://aliexpress.ru/item/100500307671 ... 4aa6Lp8ExT
a vise or press is needed to make

[Burgerman]

I wouldnt use bare copper. Oxidises fast. And that matters when we are looking at mV for balancing etc. And I would not crimp but solder. Better to buy the nickel plated ones already on that website.

[shirley_hkg]

Aren't a piece of wire and 2 ring terminals more simple and reliable ?

[Burgerman]

Yes and esp if soldered and plated against corrosion or/and oxides.

[fishinjunky]

Yes and esp if soldered and plated against corrosion or/and oxides.

That's what I was thinking,
I even went a bit overkill and used mg chemicals conductive carbon paste to help prevent corrosion between connections. This would be more of a concern if using dissimilar metals or raw copper.

[fishinjunky]

24 hours after fully charging a 8s lifepo4 pack does the voltage settle from 28.8v to 26.6v? 3.325v per cell?