LifePo4 for a 72V system

[Zenid]

I've been looking through the noob threads, but I'm still quite confused about the architecture of LIPO packs.

I and somebody else plan to upgrade our systems to a LIPO [Edit: LifePo4, I mean] bank consisting of 50 Headway 12AH 38140S cells in a 2-parallel, 25s2p configuration. This will deliver 80V at 240A maximum. However when I read elsewhere about suitable lvc boards, I read that they can only deal with about 6 or so cells typically. Are they no lvc systems that can deal with 25 cells or more?

Also I can't seem to find just one, single, power supply/charger suitable for charging on large bank. It seems to me that everyone is breaking their bank up into lots of little, separate packs and charging the individual components with separate charger. If I'm on the road and needing a recharge a power point at my destination, the last thing I want is to be dragging a stack of chargers around with me, These Meanwell chargers sound great, but where are the ones above 60V? I can't find any such animal...

Also, I've heard a lot about modding these charges with variable resistors to offer more control over them, but I can't seem to find any good decriptions of this, or threads covering the process in detail. Links, anybody?

Many thanks.

 

[Philistine]

I think you might be confusing Lipo with LifePO4. Lipo is lithium polymer, as appears in RC packs such as Turnigy or Zippy Flightmax, Headways are LifePo4. People often break up Lipo packs for charging (max 14S for RC chargers), but LifePo4 packs such as headways, are usually charged with a CCCV charger for the whole pack.

 

[theRealFury]

I've been looking through the noob threads, but I'm still quite confused about the architecture of LIPO packs.

I and somebody else plan to upgrade our systems to a LIPO bank consisting of 50 Headway 12AH 38140S cells in a 2-parallel, 25s2p configuration. This will deliver 80V at 240A maximum. However when I read elsewhere about suitable lvc boards, I read that they can only deal with about 6 or so cells typically. Are they no lvc systems that can deal with 25 cells or more?

Also I can't seem to find just one, single, power supply/charger suitable for charging on large bank. It seems to me that everyone is breaking their bank up into lots of little, separate packs and charging the individual components with separate charger. If I'm on the road and needing a recharge a power point at my destination, the last thing I want is to be dragging a stack of chargers around with me, These Meanwell chargers sound great, but where are the ones above 60V? I can't find any such animal...

Also, I've heard a lot about modding these charges with variable resistors to offer more control over them, but I can't seem to find any good decriptions of this, or threads covering the process in detail. Links, anybody?

Many thanks.

I think your getting your chemistry confused. Headway are LiFePo4 cells i beleive. Lipo is a different kettle of fish and much harder to manage via BMS and charging. Still charging an 80v headway pack is probably going to be a custom job as the usual cvoltages seem to be 48 or 72v.

 

[Zenid]

I think you might be confusing Lipo with LifePO4. Lipo is lithium polymer, as appears in RC packs such as Turnigy or Zippy Flightmax, Headways are LifePo4. People often break up Lipo packs for charging (max 14S for RC chargers), but LifePo4 packs such as headways, are usually charged with a CCCV charger for the whole pack.

Yes, sorry, that's what I meant - LifePo4. Need more coffee... :lol:

 

[frodus]

do 24s2p. Finding a charger for 25 cells is going to be a pain in the ass, believe me. Lots of 24cell chargers out there, and quite a few 24 cell BMS products available too.

 

[neptronix]

Who makes a 24 cell charger? is this motorcycle grade stuff?

 

[Zenid]

I think you might be confusing Lipo with LifePO4. Lipo is lithium polymer, as appears in RC packs such as Turnigy or Zippy Flightmax, Headways are LifePo4. People often break up Lipo packs for charging (max 14S for RC chargers), but LifePo4 packs such as headways, are usually charged with a CCCV charger for the whole pack.

Thanks. Yes, I gather my friend is going to mod two 48V meanwell chargers and stick them together to get 92V for the 80V bank (the original SLAs for our system were 72V, but this bank will give around 80V).

The question for me now is, what bits need to go in between the 92V provided by the chargers and the 25s2P banks, so that they're all properly balanced. What BMS components are needed for this side of the equation? I've combed the noobs section for FAQs, but I can't find introductory material that explains this from first principles.

I gather there's some HVC cut-off circuitry and little shunts that switch power to the individual cells off once they're finished charging, but what are these bits called and can any cope with the full 25 cells, or do I need to by a few separate boards and wire them to different parts of the banks to handle smaller chunks separately? If so, then how does the main power source get rigged up to these separate bits? Is it a number of parallel connections that split this voltage between separate charger/balance circuits?

 

[BLUESTREAK]

24 CELLS MAKE 72VOLTS AND TTHERE ARE PLENTY OF 72VOLT CHARGERS AROUND.

 

[dogman dan]

Why coluldn't he just make two 36v packs, and just pull one connector apart to charge them with two 36v chargers that are even more common?

I understand the desire to charge as one big pack, but one lousy connector,,,, If you can build a battery you can handle that. I assure you that a 10 amp 72v charger is going to be as big as two 10 amp 36v chargers. You may need even smaller ones to sucessfully use plugs out on the road anyway. So two 5 amp 36v chargers may be all a plug out there is going run.

 

[Zenid]

Why coluldn't he just make two 36v packs, and just pull one connector apart to charge them with two 36v chargers that are even more common?

Well this is where I'm getting confused. It looks to me like he's using two 48V chargers in series to get the 92V that the new 80V pack (he's notching it up from the old 72V he had). But how you get that into the individual cells is what I'm not clear about. Reading up here last night on the "v4" Fechter/Goodrum/Hecker BMS thread, it looks like their 24s BMS is what I'm looking for, but looking at the circuit board schematic, I'm seeing two charger terminal points, one left and one right. Is this arrangement for exactly what you're proposing, - two separate 36V chargers?
http://www.endless-sphere.com/forums/download/file.php?id=56372&mode=view

If so then this does seem to make sense. Two chargers isn't quite as elegant as one, but I gather that they become exponentially more expensive with voltage level, so this is probably the better solution. I just didn't want to end up with a loads of tiny little ones like i've seen some people using...

 

[dogman dan]

I was thinking smallish 12s bms's used just for charging, and something like the 5 amp lifepo4 chargers like ping sells for out on the road charging. To charge you'd unplug a series connection, then plug in the two chargers. The dinky bms would be near useless for balancing, but would shut off the charge at the right time. Completely useless for controlling discharge of more than 30 amps, so you'd use other methods to monitor pack voltage or cell voltage discharging. I'm not knowledgable about electronics, but I'm good at seeing simple solutions others may not think of. Two of those chargers is not hard to carry, I do when I want to ride 70 miles or more, and want to charge two pingbatteries at once.

The 24s bms you mention may be your best solution. I did though, want you to notice that really fast chargers get both pricy and big and heavy. Plus they may not run on the outlet outside the gas station or restaraunt, due to other devices pulling power on that circuit. So for opportunity charging, you may be more limited than you thought.

The 24 fet bms may be perfect for you, along with a fairly low wattage power supply. Sounds like you are planning a battery with some serious range anyway. So you could have a huge power supply at home, and a small one to carry.

You sure as hell don't want to have to use 24 4v power supplies to charge, but it can be a good solution for some. Always charging every cell that way. Be neat to charge that way at home perhaps.

 

[Zenid]

The 24 fet bms may be perfect for you, along with a fairly low wattage power supply. Sounds like you are planning a battery with some serious range anyway. So you could have a huge power supply at home, and a small one to carry.

Well I have an 'Ego Scoota' (see blog) that I've been overhauling and ugrading, getting the power and top speed up (it was a measly 28 mph) while still preserving a decent range (25-30+ miles or so, in 'economy mode'). These 36V ones (I'll probably need modded 48V ones like my friend, as it looks like nominal voltage on my pack will be more like 77V) don't weigh much so I can carry them with me if needs be, and I could always bolt them together or arrange 'portable' mounting points for them inside my bike. I wouldn't be getting two smaller ones AND a bigger one, as that would be just a waste of money IMO.

Which brings me to my next question, are these "V4" boards not going to be available in assembled form, and if not (or regardless) is building them with the components something a hobbyist - as opposed to an electronic engineer - can comfortably manage, as well as test?

 

[frodus]

Zenid,

Just take your time. There is a bit out there on the bike stores. Yes 48V can be easier to find in the bike world, but it can complicate the wiring of a BMS, as you pointed out.

Why not just get the right thing for the job? You don't have to get a 20A 72V charger, you could get away with a 5A 72V charger with no problem. Get that and a BMS for 24S and you're good to go.

72V chargers:
http://www.bmsbattery.com/6-charger
http://www.evassemble.com/index.php?main_page=index&cPath=3&sort=20a&page=2
http://www.batteryspace.com/smartchargerforlifepo4batterypacks.aspx

BMS:
http://www.evassemble.com/index.php?main_page=product_info&cPath=6&products_id=46
http://www.batteryspace.com/pcmfor768vlifepo4pack24inseries.aspx


What is this going into anyway? motorcycle? scooter? What kind of discharge current at 72V?

 

[chroot]

You wouldn't want deal with ev assemble. There is horrible waiting too long time and some of ES members paid and never receive items from ev assemble.

http://endless-sphere.com/forums/viewtopic.php?f=31&t=20046

Just wanted save your neck than horrible dealing with ev assemble

 

[Zenid]

Why not just get the right thing for the job? You don't have to get a 20A 72V charger, you could get away with a 5A 72V charger with no problem. Get that and a BMS for 24S and you're good to go.
{...}
What is this going into anyway? motorcycle? scooter? What kind of discharge current at 72V?

The 'Ego Scoota' - pictures:
http://zenid10.wordpress.com/category/2-scoota-pictures

I've been upgrading this 48V scooter to something with a bit more power and speed than the original, feeble configuration. I upgraded the SLA battery wiring to welding cable, added two more batteries to get it to 72V, replaced the DC converter and battery meter, and now I've upgraded the 72V 'McController' I had to a nice Lyens one that I have set on 50/120A rated/phase (see latest blog entry "Ohmless and Angry")
http://zenid10.wordpress.com/2011/04/04/ohmless-and-angry/

I can't really push the existing motor much harder than this (though the controller will top out at 65A unmodified) as I might melt the phase wires, but now I'm looking at losing some weight by building a LiFePO4 pack out of 48 Headway 38120S cells (12AH) in a 24s2p configuration to give 77V nominal at 24AH.

I know roughly what I need now, but I'm trying to get my head round the details of the charger and BMS issues, and understand how the "V4" Goodrun Fechter system should be wired up. I also need to know if this can come complete, or if not, whether building it (and testing it) isn't beyond the capabilities of a hobbyist like myself.

Thanks for the links!

 

[frodus]

You wouldn't want deal with ev assemble. There is horrible waiting too long time and some of ES members paid and never receive items from ev assemble.

http://endless-sphere.com/forums/viewtopic.php?f=31&t=20046

Just wanted save your neck than horrible dealing with ev assemble

Great heads up!

I was just searching for BMS and chargers, and those came up. I guess I was just trying to show they're easy to find.

 

[Zenid]

You wouldn't want deal with ev assemble. There is horrible waiting too long time and some of ES members paid and never receive items from ev assemble.
http://endless-sphere.com/forums/viewtopic.php?f=31&t=20046
Just wanted save your neck than horrible dealing with ev assemble

My friend got his headway cells from EV assemble, and this is where I plan to get mine. He did say, however, that you shouldn't trust them with anything more complicated than headway cells, as a BMS someone on our forum (Electric Motoring Forum) bought had to be returned.

I already saw this thread, but thanks for the heads-up anyway. The impression I get is that they are basically box-movers, but good for cheap, quality headway cells.

 

[Beavinator]

Hello zenid I am using the exact system that you are looking to do. First of all the 38120S cells are 10Ah not 12Ah. The 12Ah are 38140S. I would recommend that you go with 48cells in a 24s2p configuration because of the available BMS for that application. I am using a 50Amp capacitance BMS from EV Assemble. Here is a link: http://www.evassemble.com/index.php?main_page=product_info&cPath=6&products_id=46
As for a charger I got an Elcon 1500W 72V from them: http://www.evassemble.com/index.php?main_page=product_info&cPath=3&products_id=17
EVassemble has cheap prices but their customer service is some of the worst there is! They say that if your order takes more than 30 days they will refund you 15%. Thats a big bunch of B.S. mine took way more than that and they never gave me nothing back. Also the assembly job on their packs is horrible to say the least. I had to completely re-build my pack from scratch. I think that you will find this setup works very well. The only complaint I have is the weight but I put my packs in panniers so the weight is fairly low. Good luck, Jason.

 

[Zenid]

Hello zenid I am using the exact system that you are looking to do. First of all the 38120S cells are 10Ah not 12Ah. The 12Ah are 38140S. I would recommend that you go with 48cells in a 24s2p configuration because of the available BMS for that application. I am using a 50Amp capacitance BMS from EV Assemble. Here is a link: http://www.evassemble.com/index.php?main_page=product_info&cPath=6&products_id=46
As for a charger I got an Elcon 1500W 72V from them: http://www.evassemble.com/index.php?main_page=product_info&cPath=3&products_id=17
EVassemble has cheap prices but their customer service is some of the worst there is! They say that if your order takes more than 30 days they will refund you 15%. Thats a big bunch of B.S. mine took way more than that and they never gave me nothing back. Also the assembly job on their packs is horrible to say the least. I had to completely re-build my pack from scratch. I think that you will find this setup works very well. The only complaint I have is the weight but I put my packs in panniers so the weight is fairly low.

Yes. I'm about to get some Headway 38140S cells. I thought I said that before, but maybe I typoed and corrected it. I'm currently talking to EVassemble, but I'm also talking to someone from Zhejiang Xinghai Energy Technology Co. At the moment it's looking like a close call, because both representatives seem pretty flaky about responding and setting firm dates. It seems hard to find anybody who actually has them in stock - most of them seem to just take people's money and make excuses until they can get hold of some themselves.

As for the BMS I'm using the Goodrum Fechter board , and I'm currently populating it with all the components that I got from Mouser. For my charger, I plan to put a 48V and 32V meanwell in series to deliver 80V nominal, then mod them to tweak the total voltage up to 86.4v - 87.6v (for 3.6 - 3.65v per cell) to get the desired effect. I'm not sure if I'd want the 72V charger you got, as the bank will actually be about 77V nominal, and you'd be short of full charge capacity unless you modified it.

Yes, I heard about people's complaints against EVassemble. The consensus I'm getting is that they're fine for cells, but can't be trusted with BMS systems. I've decided to build my own so I know what's going on and can always fix it if it goes wrong.

 

[auraslip]

First off, Zhejiang Xinghai Energy Technology Co. IS Headway. They make the cells.
What ever person you are dealing with from headway, I'd recommend you search the forum for their name to get feedback on their service.

Second, they sell pre-made headway packs and chargers. So, you could pick up a charger from them. Much easier and more portable than meanwells.
Also, the chargers they provide typically have pots in them that allow the voltage to be adjusted. Lots of people have bought chargers from BMS battery. They even adjust the chargers to the voltage you want. Long shipping times though.

Meanwells will be cheaper in the end. They just take more work.

 

[Zenid]

First off, Zhejiang Xinghai Energy Technology Co. IS Headway. They make the cells.

Ahh! and there's me thinking they'd be called "Headway"...
Then why the heck don't they actually have any in stock? Everyone I speak to keeps screwing me around with delays and endless, rolling "two weeks time" estimates ...

 

[frodus]

lack of demand means they're probably trying to do more 10Ah and 16Ah which are higher in comodity. Since they don't have any, you have to wait until they make more, and they're not gonna fire up the assembly line unless there's a large order or high demand.

why not the 16Ah cell?

 

[Zenid]

why not the 16Ah cell?

They're too tall, work out too expensive and are overkill on the Ah front. 12Ah works out as the best match, and everyone else with our bike seems to agree...

 

[frodus]

unfortunately they're just not made in the quantities that the 38120S and 40160 cells are made.

Good luck though!

 

[eva-michael]

You wouldn't want deal with ev assemble. There is horrible waiting too long time and some of ES members paid and never receive items from ev assemble.

http://endless-sphere.com/forums/viewtopic.php?f=31&t=20046

Just wanted save your neck than horrible dealing with ev assemble

We have work for EV parts for three years.
We have big stock ready and low price. Our products have one year warranty and also testing before shipping.
We also have our promise: http://endless-sphere.com/forums/viewtopic.php?f=31&t=20046&hilit=some+service+promise
Right now we even have Ebay store, we cant do business if we are just slow as you said.
Also that's not possible for any seller who dont send items, Paypal and Ebay will sure kill them!!!