Suggested Method for Charging: Bulk + Cell Level

How about this:

Assuming you are running some sort of Lipo pack from Hobby city in a 6S format

12S
18S
24S
30S

For day to day use a bulk charging solution - like a BMSBattery 900W charger - $129 shipped
(Set to like 4.10V or 4.15V per cell)
http://www.bmsbattery.com/alloy-she...ifepo4li-ionlead-acid-battery-ev-charger.html



Then when you want to top off or perfectly balance you would use a combo like this:

(Two) pcs 5 x 3S charger good for up to 30S (12S, 18S, 24S, or 30S): $32.23 each
http://www.hobbyking.com/hobbyking/store/__10708__Turnigy_X5_3S_5_port_Lithium_polymer_Battery_Charger.html



Link every pair of 3S together into 6S using 5 of these - About $1 each
http://www.hobbyking.com/hobbyking/store/__9718__6S_2_x_3S_Splitter_JST_XH_5pcs_bag_.html



So far this would all be plug and play and basically retard proof. The 6S packs could be attached in any order.

You would need a 400W 18V power supply to run the balance charger - those are all over ebay and tons of free supplies could work (though you would need to make sure it is well over 13.5V)

Realistically batteries only need to be balanced once a week or once a month.
I suggest bulk charging to 90% capacity then topping off with one of these.

Of course - it is still up to the user to provide Cell level LVC protection and Cell level HVC protection and several people (including myself) offer solutions for that (but that is not want I want to talk about right now).

So... what do you guys think about a solution like this?

Bulk charging - FAST, simple, easy. Throw the charger in your backpack and charge on the road.
Then you can hook this second cell level balancer up alone OR WITH the bulk charger.
These guys run something between 2A - 3A per channel.

Matthew and I would buy a bunch of these balance chargers.
From what I have read they need to be opened up and calibrated - we would do that.
We would also package them somehow, install the 3S to 6S adapters, and wire up a power supply.
When finished we would have a 3S to 30S 3A balance charger - that will get most people on the road and it is nearly zero risk balancing.

No buttons to push
No firmware menus to navigate
No changing from series to parallel and back
No center tapping of pack (charges directly through the taps)

So for the broke fools - they start with just one of these balance chargers... then after a few weeks when they realize that waiting 5 hours for a charge sucks - they pick up a bulk charger

Then of course... the unspoken.. You realize that you need cell level protection so you buy my system

The real point here is that we dont need the ULTIMATE balance charger... Two chargers can work together. One does the heavy lifting and one does the delicate balancing.

Basically we are not looking to make any money off of this - we just need something to offer our customers that is simple to use and affordable. I am just SO FRUCKING TIRED of telling people that I cant recommend a kit for them because I dont know how they will charge and manage their batteries.

-methods

I think that lack of a total kit is part of the reason some people stray away from lipos.
That and the OMG lipos will explode if i look at them and they need special chargers made by NASA!

I'm actually in the market for all this stuff. bulk charging is the way to go.
I have only charged my pack once with separate chargers and i hate it already.

I want a balance charger(s) arrangement which means I don't have to go and buy 12 x 14S chargers and mod them so the charge -ve isn't grounded.

I also don't want to have to go and disconnect all of the series connections in my pack so that I can use off-the-shelf balancers.

How hard can it be to come up with a system for balancing 100's of cells in series without having to disassemble the pack, or take a month to do it?

I have one of that exact model of hobbyking charger, it sadly uses a common ground for all the individual pack charge ports.

Which means you would have to split the connections in the packs between each group before you could charge, or it would just be shorting them.

Do you know if the negatives on the 5 x 3s charger, are isolated? I would think that they are connected all to the same negitive input wire...

Edit: Luke had to be writing at the same time I was, lol

I think this is a 100% solid plan, and exactly what I plan to do in the future. I wouldn't understate the importance of HVC/LVC cell-by-cell protection though- I think that's what really allows balancing infrequently. I feel way better about high-power bulk charging with the latching HVC watching each cell. Fortunately you've got a good solution for that too :lol:

One other notion I have about the matter- depending on the bulk charger used- some may power down automatically at after the current tapers to a certain level, some may not (dumb CC/CV supply). To add an extra layer of safety/automation I plan to switch the AC side of the bulk charger with a mechanical countdown timer- set it for a bit long than I guess the charge to take and not have to worry about end-of-charge because the whole thing will automatically be powered-off. This is what I did for my electric MX-5 conversion http://acuteaero.com/portfolio/electric-miata/charging/ .

One last notion- I like the idea of building the HVC/LVC boards and HVC charger breaker directly into the packs so the interface to the pack is main discharge leads, charge leads (through HVC breaker), LVC throttle cut leads(to controller)- and lastly, one set of balance taps- I greatly prefer having these "main" balance taps on one larger connector- not a bunch of little JST XH guys- in the past I've used Molex MinifitJR - I know the Goodrum/Fetcher/Tppacks guys use Val-U-Lok (similar style and size). If the various wiring harnesses are pre-built and tested there should be very little chance for anything going wrong with this connection in use- as well these connectors are better for more connect/disconnect cycles than the JST ones. Basically, I would build a wiring harness to break this large balance-tap-connector out for Cell-logs or Battery medics, or whatever else- leave the harness permanently connected to the device and use the main large connector to connect and disconnect from the pack. Bottom line the pack should never have to be re-wired or re-configured for switching between discharge/charge/balance/cell-by-cell-monitoring.

This is good. I like this plan.

I would not rely on a junky rebranded Chinese charger to perform my lipo management. Those units are more often than not poorly calibrated to the point of acting more like dischargers than chargers..

It is late, so maybe the problem is actually clear, but why is this an advantage over using battery medics?

I have been doing a similar version of this lately . I charge in bulk (12s) and occasionally have my battery medic even things out between the two 6s or within either of the blocks. [I have balance leads in parallel to make this very easy]
'

Edit: Also, I acknowledge the medic is worse at balance than discharge. So often it means I'm discharging both packs to 4v to balance. [by often, I mean, I had success with that once.]

Think you all doing something that is way too confusing. Battery charging should be as follows. Connect charger. Go to sleep. Wake up. My cell phone is charged. Or charge in about 20 minutes like I do with my Lithium-Ion power tools. Also I do not want to worry about setting my house on fire.

Kin said:

It is late, so maybe the problem is actually clear, but why is this an advantage over using battery medics

Click to expand...

Since the HK X5charger was noted to be unsuitable above, the battery medic is one of a couple different options for the balancing portion of this plan.. Essentially this plan is just "bulk charge regularly, balance periodically, use cell level HVC/LVC to prevent disaster." Which particular bulk charger and balancer is the best go-to solution is the real question.

You're practically already doing it! I think it's one of those things that will seem obvious once everyone's doing it-but that is not the case yet. Particularly for packs larger than 14s where the Hyperion charger is no longer applicable I think this is the best plan.

I don't mean to knock anybodies charging procedure. There are many fast, safe enough, and convenient approaches. Nothing I see wrong with this one. I like the big bulk charger, that looks nice.

Bulk charge normaly, balance only when needed , is what many of us do already. It's just deciding the nuances that complicate it at all. What's your personal definition of complicated, fast, bulk, safe, etc.

For me, 6s is bulk enough. I still put batteries on chargers, push on buttons, come back completely done a short time later. It's not a pita process of trying to cycle packs one by one through one charger. That would suck.

I just use a meanwell and two 150w RC chargers to bulk or non balance charge. I don't find it complicated or slow. My 72v 10 ah pack is quite easily plugged into paralell harnesses, so all 8 packs charge at one time, and it takes at most 2 hours. Ok, so it's not really bulk charging, but it's not pita. One setup, done, fast enough.

God, the burden of pushing the on button on two chargers instead of one is frocking killing me. I really really gotta stop doing it so complicated.

When I do balance charge, perhaps as much as monthly, It does take longer. I do that two by two, so the pair of chargers takes 2 cycles to complete the balancing. The cylcle takes about 3 hrs max to balance. If it takes longer, packs get weeded out! But often as not, only some of the packs even need it. So it takes very little extra time to balance the one pair of packs that actually need it.

I could see improving it, by using two meanwells and two 300w RC chargers. Then I'd have just about 1 hr charging.

I could see improving it, by using the lvc hvc boards. But then I have to move the boards from bike to bike, to mower, to weedwhacker. Or spend a lot. For me, easier to just charge off the bike, and use enough chargers to make it a one setup, done, procedure.

marty said:

Think you all doing something that is way too confusing. Battery charging should be as follows. Connect charger. Go to sleep. Wake up. My cell phone is charged. Or charge in about 20 minutes like I do with my Lithium-Ion power tools. Also I do not want to worry about setting my house on fire.

Click to expand...

True, but your celphone only uses one cell, so there is nothing to balance. That immediately removes quite a lot of the worry from a pack if we could all run on just a single cell.

But even celphones are not all created equally--some of them dont' bother stopping a charge like they should, and let the things charge up to 5v (or whatever the wall charger puts out), leaving it up to the little board in the battery to cut out on HVC. But sometimes they go cheap on the batteries, too, and they either don't *have* the little board, or it doesn't work right, so not only does it overcharge the battery, it overdischarges it, too, when the phone just runs it down to the lower limit of the electronics' operating spec. Probably is one reason some celphones *do* catch fire.


So taht is what all this stuff is for--to do teh same job that the electronics that *should* already be in the celphone and it's battery do. Because the batteries we get (RC LiPo, anyway) do not have anythign with them at all--just the bare cells prewired as small packs. So we have to add something to them to make them do what you want to do--connect charger and go to sleep, without worrying about waking up on fire.

My cell phone from last year was like that. Consistently charged the battery to 5v. No wonder I kept replacing the battery every 6 months.

I don't feel bad about plugging in my lifepo4 overnight and going to sleep. But then it's going to take a lot longer than 2 hours. I don't sit fretting about my lipo for two hours though. If I need to know something, my smoke alarm is right above the charger, and the shovel is right by the door 4 feet away. I don't go to bed though.

I keep thinking about that 900w charger. Even pondering the 2000w one. Sweet for the race track.

One thing just occurred to me....

Previously while thinking of the Battery Medic I assumed we would set it to 4.2V and blast the pack with the bulk charger. Of course, as we know, the problem here is the chance of overshoot.

I had not thought about just setting the Battery Medic for 4.0V, charging up everything to >4.0V, then disconnecting the charger, connecting the medic and going to sleep. In the morning - 4.0 across the board.

Yea... that sounds like the safest and cheapest way to manage a large pack.

1) Bulk charge every day with cell level HVC protection
2) Whenever you feel like it go to bed with the battery medics attached - set to 4.0V or 4.1V

So that is about $20 / medic (assuming shipping, and BS)

I think this is a solution we can suggest to our customers.

As far as the bulk charger... I would take a dumb CC/CV over a "smart" charger 8 days a week.

Thanks for the input folks. Now lets see when those Medics come back into stock so that I can buy, buy, buy them ALL!

-methods

methods said:

Thanks for the input folks. Now lets see when those Medics come back into stock so that I can buy, buy, buy them ALL!

-methods

Click to expand...

Here you can buy them to, I got 12 and all working well (except 1, little of the real values and no trim pots inside). Last pack took more then 2 1/2 months to arrive, others about 1 months. Anyway, good to have alternatives.
https://www.leaderhobby.com/product.asp?ID=9394001226065

They let adjust balance and discharge V up to 4.2V

I am probably going to get 20 or more off of ebay right now...

$14 shipped - WAY cheaper than Hobby king (assuming there usual shipping antics)
http://www.ebay.com/itm/Li-Fe-lipo-...ltDomain_0&hash=item2a12c5dbd7#ht_2233wt_1110

I am going to try and negotiate express shipping.
Anyone want to take a few as part of a group buy? Express shipping will probably bump the price a few dollars - but who wants to wait 14 days for anything? I would not even wait 14 days for a lap dance from Luke's mom.

-methods

Might wanna try a few of them out first before ordering the whole hog.. just an idea.

You never know how shitty these things are. You could be on to something, or you could be trying to make lemonade out of lemons

Well I might be interested in a few medics!
Now the real question is when is the group buy for the bms chargers going to happen!
As it is right now $90 for the charger and $80 in shipping to Ontario, Canada.
The ideal goal for me would be to have one set for 75 V (future setup) modify it to reduce to 50 V to charge my current set up.

neptronix said:

Might wanna try a few of them out first before ordering the whole hog.. just an idea.

You never know how shitty these things are. You could be on to something, or you could be trying to make lemonade out of lemons

Click to expand...

Yea - I understand your logic and I read some of your opinions on the Battery Medic in another thread.

Here is my experience....
After spending hundreds of hours of my life designing and redesigning BMS's I have come to the realization that the difference between having all of your cells +/- 5mV and +/-20mV is really not important.

20mV * 18S = 360mV

That is less than 0.5% over the fully charged voltage of the pack....

So although I get it that people frown upon the fact that after balancing with 3 or 4 of these Battery Medics their pack is "unballanced" compared to when they painstakingly charged each 6S pack with a $180 balance charger... the reality is that having cells that are within +/- 20mV is totally reasonable for an 18S pack.

+/- 5mV is awesome - but it is awesome in the kind of way that the things Doc makes are awesome. I like them (they are beautiful) but they are WAY past the point of diminishing returns. As with any sport - getting the first 90% of performance can be had very cheap if done right.... and paying for that last few percent can just blow time and money for little return.

We negotiated 30pcs shipped DHL Express.

My expectation is that they will be a very affordable way for folks to keep packs reasonably well balanced.
If it is 20mV from end to end I will be happy.

-methods

How did you get the 900W charger shipped for $125?

It's $89 and they're asking $64 to ship it! ($153!)

You have to order more than one to get shipping charges down.
We built up a huge spreadsheet comparing every aspect of these chargers. One irritating thing to note is that the 1200W charger weighs almost double what the 900W weighs but shipping is the same price

That quoted shipping price is @ 5pcs IIRC.

-methods

ryan said:

How did you get the 900W charger shipped for $125?

It's $89 and they're asking $64 to ship it! ($153!)

Click to expand...

Gotcha. When you get through you're PM inbox backlog you'll see I requested one from you direct. I'd rather give you the shipping money than them. Let me know if you have any available.

This is now a triple post - but I think it is important.

Long story short I believe that I have confirmed that there is a "high quality" and a "poor quality" version of the Battery Medic available. The price difference is only $1. I am trying to get more details - but long story short right before my order shipped out my Chinese contact let me know that the units I was purchasing were "low quality" and he did not think that I should buy them

When a Chinese guy tells you that you listen...

This guy I am talking with has been very honest and forthcoming about fees and shipping up till now so I have every reason to believe he is trying to be helpful and not just making an extra buck. The price difference on my order would be nominal and he told me that he would be more than happy to sell me the low quality units.

I will keep you guys updated.
I hope to bring in a load of these cheap enough to undercut Hobby King with a higher quality product.

-methods

methods said:

This guy I am talking with has been very honest and forthcoming about fees and shipping up till now so I have every reason to believe he is trying to be helpful and not just making an extra buck. The price difference on my order would be nominal and he told me that he would be more than happy to sell me the low quality units.

Click to expand...

If he is selling you high quality units now, take 1 of low quality in to order as well. So you will see if there are 2 different units and how different/bad they are. :wink:

parabellum said:

If he is selling you high quality units now, take 1 of low quality in to order as well. So you will see if there are 2 different units and how different/bad they are. :wink:

Click to expand...

Oh yea....
then I do a write up for you guys and charge a premium for mine (insert evil laugh here....)

-methods