20S2P with 4S lipo

[jakequicksilver9]

Hey guys, Im trying to find a way to easily charge and discharge a 20s2p lipo pack im going to build with 4s hardases, here is my diagram for the series wiring. The bottom lines indicate where it will be connected to a 4s2p pack that i am connecting with 2 to 1 connectors for hobbyking

 

[jakequicksilver9]

This is the parallel for charging

 

[MadRhino]

Why would you want to build 20s 2p with 4s RC Lipo ?
The only good reasons I can think of, is that you can have them for free or they are aging on your shelves already.

Too many wires and connectors to assemble and charge 10 hardcase bricks. This is making it heavier and bulky, PITA to charge, with higher resistance and poor reliability. Build it simple with 4 big bricks, solder the connections and bulk charge with 2 Meanwells or a Mastech.

 

[jakequicksilver9]

4s lipos are only $15 on hobby king right now, what size bricks would you suggest 10s?

 

[Ykick]

You’ll eventually get tired of reconfiguring series/parallel wiring to recharge. Bulk charging is gonna be the way but to do this and to be reasonably safe, use a BMS.

There really isn’t that many connections using 4S since the stock 4mm bullets handle making series strings. Paralleling is another matter and you’ll either need to buy or fabricate parallel dongles.

While I use stock 4mm bullets for series strings, I then convert to APP (Anderson PowerPole) which for me is much easier to construct parallel connector blocks.

I basically series string 1P and then parallel those into whatever 2P, 3P, 4P, etc., capacity required.

If you’re going to wire in a BMS you’ll then need some parallel JST balance wire harnesses which are available through most hobby stores. Get the ones with silicone insulation.

For BMS these aren’t bad - http://www.ebay.com/itm/72V-84V-20S-60A-20x-3-6V-3-7V-4-2V-Lithium-ion-Li-ion-Li-Po-Battery-PCB-BMS-/321745442492?hash=item4ae985d6bc:g:BeUAAOSwv0tVRyqE

You’ll need to look around for a charger with about 84V output voltage.

 

[jakequicksilver9]

So would the bms balance charge also?
How easy is ut to hook it up, any soldering?
I was planning on using these for parallel then series would that still work the same as your way of S than P?
http://www.hobbyking.com/mobile/viewproduct.asp?idproduct=27078
http://www.buddyrc.com/parallel-charge-cable-4mm-bullet-connector-x2.html

 

[Ykick]

Technically yes, BMS can balance charge but often very slow and 'kinda dumb to somewhat overcharge majority of the cells and then burn that charge off through the balance leads across bleed resistors, over and over, again and again, rinse and repeat until any low cells finally catch up with the rest in the pack. It's really meant for smaller capacity groups IMO and/or very small differences in balance.

I prefer to check balance using a CellLog every once in a while. If any cell’s more than 200mV lower compared to the others at full pack charge I then rig up a single cell 2-3A charge via the balance connector and top it off that way.

How you do that is a matter of your gear and resourcefulness. I already have an iCharger so I generally use it as a 1S charger. But, I’ve also been scavenging 1S BMS from old cell phone Li-ion battery packs and wire them up to power from 5V USB and place the output into pack balance connector channel needing to be raised up.

Yeah, those are the cables which should make your life simpler. BuddyRC also has the 2P JST harness but much more money than the HK version. Check HK shipping 1st and keep in mind the BuddyRC version is slightly more reinforced where you plug in the brick JST connectors.

 

[jakequicksilver9]

Could I do some thing like this video
https://youtu.be/J_oKpOSzJpo
If I monitor the pack voltage with a cycle analyst it should cover the same things as a bms right?
If I use those 2 to 1 parallel connectors for the 4mm bullets it could be a lot simpler than the video too because i could split the 4mm bullets in half and only have to connect one cable to the neighbor instead of 2 .

 

[Ykick]

Several “ifs” about relying on pack voltage to determine LVC/HVC (low/high voltage cutoff).

“If” your cells are healthy, balanced and stay that way, pack voltage may be a reasonable method for LVC/HVC. It’s better than nothing but what happens “if” one cell dies a sudden death and shorts, which is the way majority of cells seem to suddenly fail?

In that condition, your pack voltage is assuming 20S but in reality it’s functioning as a 19S pack. If you charge in that condition your charger stops around 84V. Divide that 84V by 19S = 4.42V/cell. That’s a very dangerous voltage range to have RC Lipo. Similar things can happen on the LVC side too.

This is why individual cell voltage monitoring like what a BMS does is much preferred method of LVC/HVC. They’re not perfect either but they’ve saved my bacon many more times than they’ve cooked it.

But you don’t need to use BMS. You can be the BMS by careful monitoring, pack health testing/qualification, perhaps install some cell alarms the RC guys use?

I’ve ran “naked” before and probably will again but it’s always gotta be in the back of your mind how cells can get skewed and things turn ugly very fast.

Here’s your video imbedded.
[youtube]J_oKpOSzJpo[/youtube]

Those BM6’s are shitty, inaccurate devices and work on the “bleed” high cells principle which IMO is a dumb way to balance Lipoly/Li-ion packs.

Ideally, good cells should rarely need significant balancing and if they do, I’d 1st look into why before dicking around with bleed balancing.

 

[jakequicksilver9]

What about leaving 5 cell log 8 always connected so they could be lvc/hvc as well as balancers and monitors

 

[MadRhino]

But you don’t need to use BMS. You can be the BMS by careful monitoring, pack health testing/qualification, perhaps install some cell alarms the RC guys use?

You should monitor your cells and know each of them condition at all times.

Lico chemistry is not safe to rely on a timer, BMS, or RC charger out of immediate presence of a conscious user. Since you need to be there, fast bulk charging is much safer because you are not going to let something else distract you when you are checking the cells voltage raising quickly. If Lico cell failure does start to happen while you are watching, there is no risk of damage because you have plenty of time to deal with the situation. If you are relying on slow automatic systems, you will soon get bored and dumb about Lico safety and the day the system fails, you are likely to be doing something else, elsewhere.

One who is conscious of his Lico cells is safe, and one who is not should use another chemistry that is appropriate to rely on automatic safety.

 

[jakequicksilver9]

Ok right now I am looking around for a 900w power supply to charge at 82v 11amps. I don't want to mess around with the charger though so I think I am going to order from bms battery even though they have mixed reviews. I am also going to order an imax b6 AC for initial testing of the packs and balancing them imbetween bulk charges. Now all I need to figure out is what I am going to use for lvc/hvc and what I am going to use for monitoring cell voltages while bulk charging. If the battery medics are inaccurate then I will steer clear of them but the cell logs are out of my price point. Is there another option out there that can I monitor individual voltages with for under 10 dollars each

 

[brumbrum]

Look up lipo alarms. They are about $2 each and plug into the balance taps/leads of each pack. You will need 10. Plug them in when charging to view individual cells and have them plugged in when using your battery pack. They have a very loud beeping alarm that is pre set to 3.3volts (so if any cells drop low under load you are aware of it) but you can change this preset value higher or lower. Its not ideal, but it will help. I am currently doing exactly the same as you by setting up an 20s pack with 10x4s bricks. 84v 20ah. It is a temporary set up until i can get the funds for an adappto controller which will also have charging and bms capability. In the mean time i will be bulk charging and keeping a very close eye on the charging process, but this is not my 'everyday' bike so i do not have to charge everyday which would be a hassle.

Here...... http://www.ebay.co.uk/itm/RC-Model-...-K-/130646161167?_trksid=p2141725.m3641.l6368

 

[jakequicksilver9]

Those do seem nice but ive heard they unbalance the pack because they only draw from the bottom 2 or 3 cells, also I would only need 5 because I am paralleling first into 5 subpacks of 4s2p
How is the adaptto bms?

 

[jakequicksilver9]

Since I wont have the batteries for a while im going to start on the harness. Two orders of these
http://www.ebay.com/itm/like/171357529032?ul_noapp=true&ul_ref=http%253A%252F%252Frover.ebay.com%252Frover%252F1%252F711-117182-37290-0%252F2%253Fmtid%253D1588%2526kwid%253D1%2526crlp%253D69982082769_324272%2526itemid%253D171357529032%2526targetid%253D124340426889%2526rpc%253D0.21%2526rpc_upld_id%253D58872%2526rlsatarget%253Daud-151107829449%253Akwd-124340426889%2526device%253Dm%2526mpre%253Dhttp%25253A%25252F%25252Fwww.ebay.com%25252Fulk%25252Fitm%25252Flike%25252F171357529032%25253Flpid%25253D82%252526chn%25253Dps%2526adtype%253Dpla%2526loc%253D9008257%2526poi%253D%2526campaignid%253D313895649%2526adgroupid%253D20919789969%2526gclid%253DCj0KEQiA-NqyBRC905irsrLr-LUBEiQAWJFYTvRDHg7on3TnKlCKoT_AypmNRxgR3I9E6ueO6URmwaMaAk1O8P8HAQ%2526srcrot%253D711-117182-37290-0%2526rvr_id%253D938370806618&chn=ps&lpid=82

 

[jakequicksilver9]

I should be able to split the bullets on the outputs and connect them to their neighbors for series connections. On the posative and negative that connect to the controller and bulk charger should I make two banana to anderson cables or can I just stay with banana all the way?

 

[brumbrum]

Those do seem nice but ive heard they unbalance the pack because they only draw from the bottom 2 or 3 cells, also I would only need 5 because I am paralleling first into 5 subpacks of 4s2p
How is the adaptto bms?

well you did say something under $10.

Unfortunately adappto controllers are in the $600 region, you can balance charge through the controller itself so it does away with a standalone charger.

I cannot believe for a second that lipo alarms imbalnce big bricks of lipo..lol they will only draw a minuscule amount of current.

 

[wesnewell]

Since I wont have the batteries for a while im going to start on the harness. Two orders of these
http://www.ebay.com/itm/like/171357529032

You don't need those. All you need is 5 2X 4s parallel balance cables to parallel at cell level and then a y cable at each end to kook to controller/ I make the end cables myself fow <$1 each.
http://www.hobbyking.com/hobbyking/store/__64767__JST_XH_Parallel_Balance_Lead_4S_250mm_2xJST_XH_AR_Warehouse_.html
https://endless-sphere.com/forums/viewtopic.php?f=14&t=39666

 

[jakequicksilver9]

How do you make the y cables for under a dollar is there a thread?

 

[wesnewell]

There's 3 4mm gold connectors per end. Each cost about 15 cents. Wire is next to nothing. You can see the ones I've been using almost 5 years in the battery wiring link.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=39666

 

[jakequicksilver9]

I just got an email back from bestech that the d131 is only $65 so Im back on the bms train.

 

[jakequicksilver9]

I have been looking and can not find a difference between these what is the difference between a battery protection circuit and a protection circuit module?!?!?!

 

[Ykick]

I just got an email back from bestech that the d131 is only $65 so Im back on the bms train.

MOQ (minimum order quantity) - 2qty plus around $25-$30 DHL shipping.

Bestechpower is a royal PITA to deal with and you're SOL if/when they send you defective product. Which they do...

That's why I've moved on to buying those Supower BMS from eBay seller. They're not quite as nicely constructed but they're "good enough", you can buy 1qty and you have some recourse through eBay/PayPal if/when you require it.

No practical difference between BMS/PCM as far as I know. Which isn't much...

PS, if you respond to Bestetchpower - please let them know Joe & Dave from NYC think they suck!

 

[jakequicksilver9]

what experience did you have with them that was so bad?
on the forums I saw many people who were happy with their purchase.
they did offer me the option to buy one as a sample but i didn't ask shipping.
I looked into the supower ebay bms, it seems the highest rating they have is 60A whereas the bestech has an 80A rating. I am using an infineon 18fet at 60amp continuous but I wouldn't trust the ebay one.

 

[jakequicksilver9]

just found this site, it seems like they are just reselling bmsbattery chargers though
http://www.greenbikekit.com/battery-charger/alloy-shell-900w-charger-for-lifepo4-li-ion-lead-acid-batteries.html