Zippy Flightmax / Turnigy lipo testing

[methods]

You know those packs are rated to charge at 2C right on the site
2C charging is absolutely safe for healthy packs

As far as telling people that I charge at 3C, I am not too worried....
Who else has a 50V 30A supply on hand

3C is Gangster Status and any nOoB who follows me blinding is sure to end up with empty pockets and burnt fingers.
I am here to push the limits, not to shepard the weak thrugh the valley of darkness

When I first came to this board I was charging at 1C with a busted Lipo charger (RC nerd Status)
I was positive that a Lipo must never be charged over 1C (thanks to brow beating from ultra conservative RC geeks)

Fechter tuned me in to the fact that I could use any old power supply and I could charge at accelerated C rates.

Now I am free!

-methods

[mwkeefer]

You know those packs are rated to charge at 2C right on the site
2C charging is absolutely safe for healthy packs

I never noted that... they actually post 2C as max rate - cool!

I assume lower RI = higher C discharge rate and better ability to take fast (2c/3c) charge rates without damage or heat build up?

As far as telling people that I charge at 3C, I am not too worried....
Who else has a 50V 30A supply on hand

I can think of a few, me included (paralleled meanwells for 30A)

3C is Gangster Status and any nOoB who follows me blinding is sure to end up with empty pockets and burnt fingers.
I am here to push the limits, not to shepard the weak thrugh the valley of darkness

When I first came to this board I was charging at 1C with a busted Lipo charger (RC nerd Status)
I was positive that a Lipo must never be charged over 1C (thanks to brow beating from ultra conservative RC geeks)

Wow... Me and a few dozen others went from newbie to Gangsta status in span of 2-3 weeks (maybe Im not as dumb as I thought I was, nevermind I forgot "thinking's not my strong suit")

Keep pushing the limits (deviant - now i get it) - we all appreciate it (our fingers and pockets too), leave the meek to everyone (anyone) else.

Fechter tuned me in to the fact that I could use any old power supply and I could charge at accelerated C rates.

Now I am free!

And then you took the time to vet and test that charging process and were kind enough to freely and openly shared your results with all of us..

So on this appropriate day to be... reflective, Thanks to you and Fechter (and Gary and everyone else who has worked so hard to figure this out) for pushing the limits together! (anyone hijacks that and goes into a gaye joke will be seriously thrashed!)

Happy thanksgiving everyone!

-Mike

[Hyena]

When I first started with lipo I bought a cheap B6 charger and it blew up after a few months of use. I the learned the ways of ghetto charging from methods and nearly a year later I'm not looking back. So yeah, thanks to Methods, Gary, Fechter et.al for spreading the knowledge and making this gear accessable to us

I pity all the suckers with their 2C lifep04 and 6 hour chargers!
"ooooow lipo is so dangerous, get away from me"
Guns are dangerous too, but that's fine ladies, keep playing with your bows and arrows

BTW, just placed an order for another 4 25C zippys and a few other lipo nick nacks
I noticed HK are also selling another turnigy branded lipo monitor for $10, similar to the BM6 but with a larger illuminated LED display. It looks like a neater package over the BM6 but the display will probably suck a bit more power from the pack if you tend to leave it connected when not in use.
I grabbed one out of interest, I'll report on the accuracy when it arrives

http://www.hobbyking.com/hobbycity/stor ... &aff=81978

[Arlo1]

When I first started with lipo I bought a cheap B6 charger and it blew up after a few months of use. I the learned the ways of ghetto charging from methods and nearly a year later I'm not looking back. So yeah, thanks to Methods, Gary, Fechter et.al for spreading the knowledge and making this gear accessable to us

I pity all the suckers with their 2C lifep04 and 6 hour chargers!
"ooooow lipo is so dangerous, get away from me"
Guns are dangerous too, but that's fine ladies, keep playing with your bows and arrows ]

[mwkeefer]

I have to agree with everyone... LiFePo4 may have it's "Safety" chemistry advantages but... 20AH @ 1/2C or less? 4-8 hr for a 10AH pack (depending on charger)... forget that;

i Can bulk load my 2P15S using a pair of S-350-24 meanwells (only one having a modified voltage limit - the other is stock) from empty to full in just about 40 minutes... That will buy me about 22miles of hard riding or 35-40 if I take it easy and pedal along.

Need I say more?

-Mike

[swbluto]

I have to agree with everyone... LiFePo4 may have it's "Safety" chemistry advantages but... 20AH @ 1/2C or less? 4-8 hr for a 10AH pack (depending on charger)... forget that;

i Can bulk load my 2P15S using a pair of S-350-24 meanwells (only one having a modified voltage limit - the other is stock) from empty to full in just about 40 minutes... That will buy me about 22miles of hard riding or 35-40 if I take it easy and pedal along.

Need I say more?

-Mike

I love how this thread is turning into a LiFePO4 bash. Note, the chemistry itself isn't limited to low charge rates, it is specific brands (which I'm sure many are insinuating ping). One specific advantage that lifepo4 has on lipoly is its high charge cycle life, which may make it more economical than lipoly in the long run if it is used often enough. For performance vehicles that don't get daily use to relatively deep discharges, LiPo may be a clear winner.

As a specific example of a lifepo4 chemistry that doesn't suck, try a123. Try the next generation. Even try the newest turnigy lifepo4. This sentiment of "Get roughly similar energy capacity lifepo4 at the same rough cost of lipo and then it's worth it" makes me laugh given the longevity and safety advantages. I guess it's quite serious if you're only concerned about your capacity *now* and for the near-term, but it's not a good cost-effectiveness analysis in my opinion if you're thinking of the long-term (Unless you have high confidence energy storage technology will vastly improve in the relatively short term, which may be a pretty good guess.)

[Hyena]

I love how this thread is turning into a LiFePO4 bash.

It's not a lifepo4 bash, I think it's just that guys who prefer lifepo4 also prefer men...

anyone hijacks that and goes into a gaye joke will be seriously thrashed!

Sorry...

[methods]

(Unless you have high confidence energy storage technology will vastly improve in the relatively short term, which may be a pretty good guess.)

Yes

I paid about $100 only a year ago for the packs I now get for $50
2 years ago I paid more like $250 for "Name Brand" stuff like Thunderpower V2

Hell... I paid $109 each for three 4S 2200mah TP Extreme V2 packs only just two short years ago

Making a 5 year investment in any battery technology right now is a fools move in my opinion
By the time this stuff wears out it will be old news.

But..... Then.... I dont look at this hobby as an "economical form of transportation"
I look at this hobby as a training ground for the real Electric Revolution that is right around the corner.....

The only thing stopping me from converting my car is the price of Batteries.

-methods

[momo]

[quote][/quote]I look at this hobby as a training ground for the real Electric Revolution that is right around the corner.....

The only thing stopping me from converting my car is the price of Batteries.


I'm right with you Methods. Just yesterday a thought of converting my 89 s-10 blazer into electric came though my mind. The thought of the batteries alone very upsetting. Having a 20 year old car for 14years is pretty good though.

[number1cruncher]

I found this 3x4" vinyl gutter at Home Depot tonight. $11 for 10ft. Seems to be like what Hyena has, but ribbed.

Gutter1.jpg

(19 KiB) Downloaded 336 times

Fits two 6Ss side by side with a little room above.

GutterBatt1.jpg

(33.55 KiB) Downloaded 334 times

[recumpence]

I agree with Methods. I am not into this for cost savings on trasportation or because I love to hug trees. I am into it as a hobby that moves us closer to electric cars and motorcycles.

It is funny how, just a year ago, even guys like Gary were pushing eveyone away from Lipo. Now many are moving toward Lipo without looking back, including those who were against it not long ago. I was pretty much told by eveybody I asked that I was insane to run Lipo in my recumbent when I started collecting parts for it less than 2 years ago. Now, here we are.

At any rate, Lipo can last a loooong time if you stay well under their C rating and stay away from over-discharging. Heck, I have an RC transmitter with a 5 eyar old lipo pack in it that is still going strong!

Matt

[Hyena]

The only thing stopping me from converting my car is the price of Batteries.

Likewise. Hopefully once commercial electric cars start to become more popular that'll drive the price down. That said I'll seriously look at the chevy (holden here) volt when it comes out if its not rediculously priced.
I'm sure there'll be a way to reconfigure it's battery to run the equivalent of 1/2P - 2S to make it go like a shower of shit for a short distance

I found this 3x4" vinyl gutter at Home Depot tonight. $11 for 10ft. Seems to be like what Hyena has, but ribbed.

For her pleasure!
That stuff is around 50% higher than the stuff I'm using (why must Americans supersize everything ) but its a step in the right direction for you guys in the northern hemisphere.
Incidently, I've cut and weighed a few lengths of the 100x50 stuff I'm using and am posting it to a few members in the US and Canada.
I've run out now but can buy more if there's sufficient interest. Shipping works out at $21 for 2 14" long boxes (boxes hold 4 6S packs each)

[mwkeefer]

For her pleasure!
That stuff is around 50% higher than the stuff I'm using (why must Americans supersize everything ) but its a step in the right direction for you guys in the northern hemisphere.
Incidently, I've cut and weighed a few lengths of the 100x50 stuff I'm using and am posting it to a few members in the US and Canada.
I've run out now but can buy more if there's sufficient interest. Shipping works out at $21 for 2 14" long boxes (boxes hold 4 6S packs each)

Guys,

The ribbed 2x3 and 3x4 I have alot of experience with (made many packs using somthing akin to the Bosch FAT packs)...

A few things...

1.) If your trying to bend it, mold it or anthing - Lowest possible oven setting and aluminum foil - the stuff just withers to nothing fast!
2.) Forget the hack saws - use Airline Snips aka Tin Snips (straight and long as possible) and drill starter holes for the cutting (dremel at really low speed works good for notch to begin cutting but.... The snips leave a much cleaner edge are really alot easier and allow you to cut to form fit (ie: around the headstem for instance) with ease.
3.) I was advised not to use a Foam cutter or any other hot tool on this, I tried it anyway ... ever burned a toothbrush for epoxy when you had no glue? Or driven past a meth lab? Yuk, don't breathe the crap.

If you sheer it along an end... you can recombine as many sections as you like for added capacity... I can't fit 10S (as 2 5S packs stacked) into a normal 2x3 but only by a narrow margin - I just cut a part 3/4 length off... did that again and joined the two long parts (first with clamps then I drilled holes and finally I used small nut/bolts (Inside of packs is insulated with 1/4" dense foam so no chance of puncture and I did get the very shortest bolts I could.

They make nice above or below main tube carriers... I don't bother making them in "chunks".. I actually Just build them for the capacity I need to length... with a little work you can make a controller mount within the conduit also (isolated from batteries) then the one nice thing... they take to paint well (a little rustoleum plastic coat serves for the flex - no cracking of paint).

The one thing I haven't tried (only thought of it a few hours ago) is low temp ironing the ridges out. I know this will be a bad thing... I will wear a o2 mask but... I have to give it a shot... If these 2x3 would flatten then they could hold 10S no prob... the 3x4 already holds 12S but not 15.

Hope that helps!

Hyena - hows about just sending me some PVC pipe from over there or find the manufacturer name for us.... I can track a source here if you can find out where its coming into market there ?

Please

-Mike

[hurricaniac]

Thanks again, Mike.

I'm awaiting delivery on the 48V server PSU and will report back on how it goes. My wife still insists that all lipo charging be done out in the driveway away from the house...darn those youtube videos...
-Bruce

[mwkeefer]

Thanks again, Mike.

I'm awaiting delivery on the 48V server PSU and will report back on how it goes. My wife still insists that all lipo charging be done out in the driveway away from the house...darn those youtube videos...
-Bruce

Bruce...

She's right. Asides from the oven (and be prepared however unlikely to loose the oven) there really aren't safe places to charge lipo in bulk indoors....

That said:

My whole plethora of supplies is next to me right now (a desk over in my bedroom) and I'm doing 3 - 3.5C charges to 80% then 2C until done. Been doing this all week = )_
I do have a trash can filled partly with Kitty Litter nearby (small trashcan) and I have a haylon extingisher (and foam for those who care)... plus, I never leave them unattended (or the iCHarger incident would have taken the house down)... until now, honestly I watched them while they charged to analyze curves at various charging rates and to see how different methods ... well, differ. Now I am convinced if your not charging outdoors, YOU MUST KEEP AN EYE on them...

I think methods puffed a cell (not exploded, I don't think) because he didn't hear the BM6 going off with the enemic beep beep beep.

And the iCharger incident I had demonstrates (it did for me)... even a nicer RC charger could burn your house down if left unattended while charging/loading indoors.

Storage:

Just use common sense... you can bring them inside when there done charging... They will be plenty safe in storage if they don't get dropped, punctured or as almost happened to me once - pre heated (My mom turned the oven on to pre-heat while I was upstairs brushing my teeth - {she was over for dinner, no i don't live with my mother! }, I came down and could smell the oven... ouch, no damage done (thank god for crappy aluminum oven plates) but that could ahve been a disaster! So if your going to use the oven for storage - do what I do... put tape over the knob. Red works well!

As you become more and more accustomed to using Lipo and more familiar with your pack (new packs are most likely to fail quickly if theres going to be an issue), your wife will too...

Sooner or later the lipo will live in the house (I think most of us on here are the same after a while, maybe it's just me.)

-Mike

[Hyena]

I've gotten a bit blase with my charging. I charge using only a meanwell supply in my car port now which is below my house but I often connect it after work and forget about it. I'm usually reminded when I wake up in the middle of night and hear the BM6 beeping (my bedroom window is above the carport) Theres always one cell that takes a little bit of extra charge, never above 4.23v but its enough to trip the BM6 (other cells are at 4.18v). I've got one of those battery medic balancers on the way from HK so I'll see if it behaves after balancing. I suppose after 150 cycles of never being balanced they're a bit overdue

Re: the oven, I once killed a set of car headlights by leaving them in the oven a little too long. It's the done thing to put headlights in the oven to remove the lenses if you're giving the surrounds the 'black out treatment' but yeah, I left em a little too long and came back to find droopy headlights all melted through the shelves. My then-girlfriend had some very unkind things to say about it for quite a while...

Mike I have no idea about the pipe suppliers it doesn't come with any markings or brands on it, I just buy it from our aussie equivalent of home depot (or the workbench, from the tv show reaper - if that's actually a real store!) I can send you some though, shoot me a PM.
Heating wise this stuff doesnt take much at all to go soft and floppy - I hit it for only a few seconds longer than I would normal heat shrink with my heat gun and it went like rubber. I use a cheap compound mitre saw to cut mine - same thing I used to cut the hardwood for my deck and the 3mm aluminium angle for another project The stuff is a bit brittle when cutting it though. The first length I cut was no problem but the second lot splintered, cracked and chipped a few times if I didn't go ultra slowly. It's probably just the wrong blade for the job, but beats using a dremel when I'm cutting alot of lengths

[El_Steak]

Quick question for all you Lipo users:

While the nominal voltage of a 24s lipo pack is 88.8v (3.7v/cell) , I see that the off-the-charger voltage is around 100v. I guess that the voltage under load falls somewhere between those numbers.

Let's say I have a 24s2p pack with 20c cells, what ballpark voltage would I get under a load of 30-40 amps?

[mwkeefer]

Quick question for all you Lipo users:

While the nominal voltage of a 24s lipo pack is 88.8v (3.7v/cell) , I see that the off-the-charger voltage is around 100v. I guess that the voltage under load falls somewhere between those numbers.

Let's say I have a 24s2p pack with 20c cells, what ballpark voltage would I get under a load of 30-40 amps?

I'm going to give you a bit of "unscientific" information here in the interest of simplicity.

24S2P of 20C cells wouldn't show more than a volt of dip at 30-40A so...
Full Charged Pack: 98 - 97v @ max load
Nominal: 88 - 87v @ max load
LVC: 71-70V @ max load

* read on only if you want more specific info:

---

A single parallel string of 20C cells (5AH) would be pushing 6-8 C or Capacity under 30-40A load but by paralleling you are presenting a load between 3-4C which is nothing to these cells.

A pack of 24S2P could handle current draws of 200A sustained (20C) or 300A for 15-60 seconds (30C) by using between 3 and 4 C (which will really end up being between .5 and 4C but average will be around 1.5C).

You need to assume nominal operation, these discharge in a near linear (straight progression) manor so they will progress slowly from 4.15v per cell down to between 3.8 and 3.7... once at nominal voltage they will hang there for most of their life, with a well managed and balanced pack of 24S2P (about 10 shallow cycles before actually running) you can use a cutout at about 3.3v and all cells will end up about .3v of each other at end of cycle.

So you will have a pack with the following specs:
Fully Charged (off charger): 99.6v @ 4.15v per cell
Nominal: 88.8v
Suggested LVC: 81.6v @ 3.4v
Allowable LVC: 72v @ 3.0 if cell level monitoring / LVC is implemented.
Capacity: 888 wh

I would suggest you upgrade a controller to 160v caps, FETs and and components to handle that voltage... I would ask some of the others who have done 24s (Gary, Methods, YPedal I think, LiveforPhysics, etc) to see what controller they have used and what modifications - build ups they have done.

You will be running practically US house voltage in that ride, best build up first than repair later.

[mwkeefer]

Quick question for all you Lipo users:

While the nominal voltage of a 24s lipo pack is 88.8v (3.7v/cell) , I see that the off-the-charger voltage is around 100v. I guess that the voltage under load falls somewhere between those numbers.

Let's say I have a 24s2p pack with 20c cells, what ballpark voltage would I get under a load of 30-40 amps?

I'm going to give you a bit of "unscientific" information here in the interest of simplicity.

24S2P of 20C cells wouldn't show more than a volt of dip at 30-40A so...
Full Charged Pack: 98 - 97v @ max load
Nominal: 88 - 87v @ max load
LVC: 71-70V @ max load

* read on only if you want more specific info:

---

A single parallel string of 20C cells (5AH) would be pushing 6-8 C or Capacity under 30-40A load but by paralleling you are presenting a load between 3-4C which is nothing to these cells.

A pack of 24S2P could handle current draws of 200A sustained (20C) or 300A for 15-60 seconds (30C) by using between 3 and 4 C (which will really end up being between .5 and 4C but average will be around 1.5C).

You need to assume nominal operation, these discharge in a near linear (straight progression) manor so they will progress slowly from 4.15v per cell down to between 3.8 and 3.7... once at nominal voltage they will hang there for most of their life, with a well managed and balanced pack of 24S2P (about 10 shallow cycles before actually running) you can use a cutout at about 3.3v and all cells will end up about .3v of each other at end of cycle.

So you will have a pack with the following specs:
Fully Charged (off charger): 99.6v @ 4.15v per cell
Nominal: 88.8v
Suggested LVC: 81.6v @ 3.4v
Allowable LVC: 72v @ 3.0 if cell level monitoring / LVC is implemented.
Capacity: 888 wh

I would suggest you upgrade a controller to 160v caps, FETs and and components to handle that voltage... I would ask some of the others who have done 24s (Gary, Methods, YPedal I think, LiveforPhysics, etc) to see what controller they have used and what modifications - build ups they have done.

You will be running practically US house voltage in that ride, best build up first than repair later.

[El_Steak]

Thanks for the quick and detailled answer.

You need to assume nominal operation, these discharge in a near linear (straight progression) manor so they will progress slowly from 4.15v per cell down to between 3.8 and 3.7... once at nominal voltage they will hang there for most of their life

I should not be drawing more than 8ah (80%) out of that pack on my commute. So I guess I would be staying somewhat above nominal all that time. I know that LiFePO4 goes very quickly from full charge to nominal, it seems to be more progressive with LiPo. Is there a typical Lipo discharge curve available somewhere?

I would suggest you upgrade a controller to 160v caps, FETs and and components to handle that voltage... I would ask some of the others who have done 24s (Gary, Methods, YPedal I think, LiveforPhysics, etc) to see what controller they have used and what modifications - build ups they have done.

I'm one of the lucky owners of a Methods "Gangsta" 100v / 100a 18 fets controller so I'm all covered on that side

[mwkeefer]

At 8ah you should be fine.... stick to the 80% rule and the Lipos will last you quite some time (with proper care and feeding).

imho - LiFePo4 (of the traditional eBike variety) has a max rating of 2-3C and huge drop under load (assuming 10AH pack 12S LiFePo4)... the discharge is as you say, quick to nominal (more like jump) but the sag you get under loads is the real limiting factor of this type of LiFePo4.

There are good LiFePo4 or LiMn packs out there... but in my limited experience (very limited, I've only tested about 5 LiFePo4 packs from various vendors) the only non LiPo chemistry which has actually worked for me for 1000s of miles is the Valence Lithium Ion (Saphion?) from my Segway i2.... These are LiMnPo (Lithium Ion Magneseum Phosphase) in nature and deliver great power in a fairly safe (albeit heavy) package.

Im sure the curve is out here... I've got plots in EagleTree of logs from actual test rides if youd like some sample data for Lipo packs... the biggest I have samples for is 15S or 62.5v (EagleTree limit).

Congratz on the methods killer controller! Having just finished an upgrade on a 9FET... I have a new found respect for Mr. Methy... Those caps are a biatch! Your right you should have no issues with that controller... I don't think he programs them wide open though (current limited), you may need to program it yourself to get the desired performance (I can only assume performance with a 40A @ 98v = 3920w / 5.25hp).

How far is your commute to work and back?

Will you charge at work?

Hope it helps,
Mike

[El_Steak]

Im sure the curve is out here... I've got plots in EagleTree of logs from actual test rides if youd like some sample data for Lipo packs... the biggest I have samples for is 15S or 62.5v (EagleTree limit).

Thanks, I just did an image google search on lipo discharge curve and found more graphs than I needed!

How far is your commute to work and back? Will you charge at work?

Its 7-8 miles. I am planning on charging at work so I don't have to go to 24s4p.

The new HobbyKing 4 channel charger seems like a decent solution for a charger to carry to work. Not too big or heavy. At 2.2amps per channel its a bit slow but would also allow me to use a smaller powersupply.

[vanilla ice]

I'd wager you would have to break up a series string to use that quad.. would be cool if you didnt!

[mwkeefer]

el_steak,

I don't think hobby chargers are the way to go for this... Personally I would use hobby chargers just to break in the packs with repeated shallow cycles. Then build it up.

Then get some 48v Meanwell power supplies (40-100.00) S-350-48 which should be fairly easy to modfiy for 94 v (they are only rated to 94v on the PCB... it may be an issue, you may need to do a 20S pack instead) - fechter and Gary have been helping me work out some of the current limiting issues with these and I think we will shortly have a variable current circuit mod for these series of supplies (the S-350) to get them dialed in for stable operation (maybe 400w limited).

Combine as many of these in parallel as you like or... grab a pair of 48s or a trio of 24s and connect them in series to obtain your required voltage for 24S (24 * 4.15 = 49.8v) so a pair of 48v units connected in series would be safer and work better than a single 48v modified for expanded voltage... assuming you limit to 400w.. it will be 400 / 98 = 4A which is 1/3C (roughly)... add more in parallel for higher currents charges (each supply weighs about 2 lbs).

Someone here can likely offer lots of alternatives (there are too many to enumerate, my posts are long enough as is) for turnkey charging solutions and yep you still need a balancer of some sort (im using hobby chargers for now, balancing and cycling 5 times before I build a pack into configuration - only about every 10 charges do I cut it short at 4.125v per cell and then I break down the pack into parts, wire it all up as a single 5S pack (6P5S) and run it on the balancer/charger at 5 or 10A rate (into 30A capacity) until it's done. rebuild the pack into series configuration and off you go for another 10 cycles.

A good hobby charger is the iCharger 208B+ (specifically for your 24S pack) ... you would first want to build subsections of 6 or 8S from your packs.. then parallel 2 of each subsection together (I use 4mm gold plugs but you can do as you see fit) finally throw them all on the iCharger and run it at 20A rate (1010B+ is only able to run to 10A rate) - in this case... get a 24v meanwell and tune it down to 17v for use with the iCharger (that power has to come from somewhere)...

7 - 8 miles is nothing... you won't likely need to charge at work even. The bulk charger is the safest way... (since all of us get the dread Kentucky Fried Finger or burnt to shit when we break our packs apart into parallel for charging on these hobby chargers) and if you have a balancer board / bms from Gary (or anywhere else) it should work well with the Meanwell bulk and make it a fairly simple process. Eliminating the need to break the pack apart and keeping our fingers safe.

Hope this helps!

-Mike

[liveforphysics]

el_steak,

I don't think hobby chargers are the way to go for this... Personally I would use hobby chargers just to break in the packs with repeated shallow cycles. Then build it up.

Then get some 48v Meanwell power supplies (40-100.00) S-350-48 which should be fairly easy to modfiy for 94 v (they are only rated to 94v on the PCB... it may be an issue, you may need to do a 20S pack instead) - fechter and Gary have been helping me work out some of the current limiting issues with these and I think we will shortly have a variable current circuit mod for these series of supplies (the S-350) to get them dialed in for stable operation (maybe 400w limited).

Combine as many of these in parallel as you like or... grab a pair of 48s or a trio of 24s and connect them in series to obtain your required voltage for 24S (24 * 4.15 = 49.8v) so a pair of 48v units connected in series would be safer and work better than a single 48v modified for expanded voltage... assuming you limit to 400w.. it will be 400 / 98 = 4A which is 1/3C (roughly)... add more in parallel for higher currents charges (each supply weighs about 2 lbs).

Someone here can likely offer lots of alternatives (there are too many to enumerate, my posts are long enough as is) for turnkey charging solutions and yep you still need a balancer of some sort (im using hobby chargers for now, balancing and cycling 5 times before I build a pack into configuration - only about every 10 charges do I cut it short at 4.125v per cell and then I break down the pack into parts, wire it all up as a single 5S pack (6P5S) and run it on the balancer/charger at 5 or 10A rate (into 30A capacity) until it's done. rebuild the pack into series configuration and off you go for another 10 cycles.

A good hobby charger is the iCharger 208B+ (specifically for your 24S pack) ... you would first want to build subsections of 6 or 8S from your packs.. then parallel 2 of each subsection together (I use 4mm gold plugs but you can do as you see fit) finally throw them all on the iCharger and run it at 20A rate (1010B+ is only able to run to 10A rate) - in this case... get a 24v meanwell and tune it down to 17v for use with the iCharger (that power has to come from somewhere)...

7 - 8 miles is nothing... you won't likely need to charge at work even. The bulk charger is the safest way... (since all of us get the dread Kentucky Fried Finger or burnt to shit when we break our packs apart into parallel for charging on these hobby chargers) and if you have a balancer board / bms from Gary (or anywhere else) it should work well with the Meanwell bulk and make it a fairly simple process. Eliminating the need to break the pack apart and keeping our fingers safe.

Hope this helps!

-Mike

The 4-way 6s charger from HC uses 4 isolated chargers, and can be very simply plugged in to charge a 24s pack in a balanced fashion. It's not a bad idea really. No risk of KFF (or KFD), and you can plug in a little deans plug and a 6s JST connector for each of the 4 packs, and the order plugged in makes no difference. Not as fast as charging with a meanwell, but it's kinda slick.