Low voltage cutoff for 10s lipo packs?

[Eujangles]

Hi all,

I'm a hair away from ordering the Zippy Compact 10s 5800mah
from hobbyking http://www.hobbyking.com/hobbyking/store/__21388__ZIPPY_Compact_5800mAh_10S_25C_Long_Lipo_Pack.html

This will be my first foray in to lipo and thanks to the members in this forum as well as hobby king's tech support, I feel pretty confident about not blowing myself up.

I do have one question that remains unanswered though: hobbyking does not carry any product to monitor cells or cutoff/alarm when low voltage is reached for 10s packs. I can't find a product from anywhere else that does this either. What can I do to ride safely with this pack? I know that a cycle analyst can be set to a low voltage cutoff, but that just monitors the voltage of the whole pack. Is there a danger that 1 cell could be drained more than the rest, or will that work safely so long as the pack is in balance?

Also, if anyone knows of any way to cut off the voltage other than a CA, I'm all ears! Will a BMS do the trick? If so, where would I get one, and which one for the 10s pack?

Thanks in advance for any advice, and once again a big thanks in general to all the contributors of ES!

 

[motomech]

Yeah, at 29V LVC, the Infinion 25A's cut-off is a little low for 10S.
Not to worry, the CA[SA or DP?} will do the job. At any rate, you will be monitoring the Voltage as you ride and the Low Voltage Gremlins won't sneak up on you
Your bike looks more like a play bike than a commuter, so you need not worry about one cell getting too low. It's not like you are going to be hammering it so as to not get to work late.
Just get to know your packs first. Cycle several discharges down to 3.5V and balance charge for a while. You will know up front in the unlikely event you have a rogue cell.
Go with the EV Falcon bag. You have the advantage with all that space to really pull it taunt and have it wrinkle free.
I compromised on the controller placement and put it in the mesh side pocket of the Falcon bag. The connectors are in a piece of intertube and the controller's shiney-ness is subdued by wrapping it in a piece of speaker grill cloth.

 

[Eujangles]

Thanks for the reply, and awesome bike!

The goal for my build is to be somewhere between a play bike and commuter. I'll be getting 2 of the 10s packs for when I think i'm going to be out on a longer ride.

Thanks so much again for replying...think I'm gonna go ahead and place my order right about now

 

[wesnewell]

LVC for 10s lipo should be 35V. Cheapest solution is to install a voltmeter so you can monitor pack voltage. Recharge at a no load voltage of 37V.

 

[dogman dan]

The 10s pack will have two 5s jst plugs. So you can use the 5s lv alarm devices, cellogs, or whatever.

I just bought a couple 0-120v voltmeters on ebay, thanks to a heads up thread. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170846310527

I won't have a pack that is whacky out of balance all the time on my bike. Stopping at a sensible voltage, such as 36v means you will never have good packs overdischarge one cell. I do like to carry a cellog in my pocket out riding though. If I have to go deep into the pack, I can do a quick look at the balance of them when I go past 3.65v per cell.

 

[Eujangles]

Thanks for the replies guys! Dogman, I think you've consistently come to the rescue every time I've asked for advice, thanks so much.

That voltmeter looks great! I might just go with one of those instead of a CA (really want the CA but am kind of already blowing the bank on this project). I guess I would need to split off the positive and negative wires on the pack to use it?

Also, unrelated question: if I play it totally safe and keep the pack between 36.5V-41V, what kind of AH can I realistically expect from the 5800mah pack?

Thanks again everyone!

 

[sn0wchyld]

Thanks for the replies guys! Dogman, I think you've consistently come to the rescue every time I've asked for advice, thanks so much.

That voltmeter looks great! I might just go with one of those instead of a CA (really want the CA but am kind of already blowing the bank on this project). I guess I would need to split off the positive and negative wires on the pack to use it?

Also, unrelated question: if I play it totally safe and keep the pack between 36.5V-41V, what kind of AH can I realistically expect from the 5800mah pack?

Thanks again everyone!

probably around 5ah. most of the capacity exists between 4.15 to 3.65. outside of that is usually no more than 10% or less of the rated capacity.

 

[kfong]

Take a look at my smart switch

Hi all,

I'm a hair away from ordering the Zippy Compact 10s 5800mah
from hobbyking http://www.hobbyking.com/hobbyking/store/__21388__ZIPPY_Compact_5800mAh_10S_25C_Long_Lipo_Pack.html

This will be my first foray in to lipo and thanks to the members in this forum as well as hobby king's tech support, I feel pretty confident about not blowing myself up.

I do have one question that remains unanswered though: hobbyking does not carry any product to monitor cells or cutoff/alarm when low voltage is reached for 10s packs. I can't find a product from anywhere else that does this either. What can I do to ride safely with this pack? I know that a cycle analyst can be set to a low voltage cutoff, but that just monitors the voltage of the whole pack. Is there a danger that 1 cell could be drained more than the rest, or will that work safely so long as the pack is in balance?

Also, if anyone knows of any way to cut off the voltage other than a CA, I'm all ears! Will a BMS do the trick? If so, where would I get one, and which one for the 10s pack?

Thanks in advance for any advice, and once again a big thanks in general to all the contributors of ES!

 

[dogman dan]

Yes, you'd need a second set of wires from the battery to the cheap voltmeter. The way I'm doing it already on one of the bikes that will get this volmeter is to just crimp a second small wire into the andersons I use to connect to the controller. So if the controller is plugged in, the meter will be powered up. Right now the bike has a lv warning beeper. I may leave the beeper on the bike when I install the meter, so I have both a gas guage and a lv warning.

Many other ways to do it, it could be part of the battery pack, with a switch to turn it on and off.

 

[alemanyorks]

Very useful information,thinking of getting one of those packs myself, what sort of range do you get with a single pack Eujangles, now I presume you've built it?

 

[dnmun]

i have seen several lipo packs where one or more of the pouches has discharged to 0V.

if you bulk charge a 6S pack with one dead pouch, do you know what the voltage would be on the remaining 5 pouches?

these people are telling you that you do not need a BMS since they have never used one and they are smarter than anyone else and therefore they feel they know that a BMS will ruin your battery even though they have never used one or have any idea how it works. maybe they can explain to you what the voltage will be on the remaining pouches.

 

[wesnewell]

i have seen several lipo packs where one or more of the pouches has discharged to 0V.

I've never seen one under 2.79V. Just checked a small single pouch that's been sitting on my desk for a few years and it still has 3.91V.

if you bulk charge a 6S pack with one dead pouch, do you know what the voltage would be on the remaining 5 pouches?

If you bulk charge a pack with a 0V cell, you're an idiot. I have never advocated bulk charging without the use of balancers, although I've done it many times.

these people are telling you that you do not need a BMS since they have never used one and they are smarter than anyone else and therefore they feel they know that a BMS will ruin your battery even though they have never used one or have any idea how it works. maybe they can explain to you what the voltage will be on the remaining pouches.

I don't know all of "these" people, but I use a BMS every time I charge my pack, It's built into the rc charger and is much more accurate than any of the cheap ass BMS's used on battery packs. And all of your stupid assumptions is wrong. I know I know how a bms works, and I'd bet most of the users here do too. I know you keep putting out ridiculous advice about the use of lipo that could cause someone with no knowledge of it to cause serious damage. I also know that many people that bought battery packs with bms have had them ruin there packs because they didn't know they would ruin their packs if just left sitting for long periods of time. I know the downfalls of both using and not using a bms. Personally, I wouldn't use a bms with a lifepo4 pack either. The convenience of a simple charge port are vastly overshadowed by the down falls of using one. I don't want my battery pack cutting out in the middle of the intersection no matter how low a cell gets. And I don't want to park my bike for a month and come out to a ruined battery pack because the BMS drained a cell group just sitting there. Advocating for some one to use a BMS without pointing out the disadvantages also is just wrong. Over 10,000 miles and almost 3 years of bms free riding with lipo without as much as a puffed cell tells me I don't want a bms that limits the potential of my batteries.

 

[Eujangles]

Very useful information,thinking of getting one of those packs myself, what sort of range do you get with a single pack Eujangles, now I presume you've built it?

Hi Alemanyorks,

I've actually since fried the pack by leaving the bike on overnight by accident (sure wish I'd got that BMS!..and wasn't a dumbass lol), but prior to that I would say I was getting about 15-18km (no pedaling, flat ground) out of it. My setup is the Q100 201 RPM motor, so pretty low consumption, but run at a bit higher amperage than it's intended for (22A with the KU93 controller). And no, I didn't build the pack, it's just one of the oversize ones from hobbyking: http://www.hobbyking.com/hobbyking/store/__21387__ZIPPY_Compact_5800mAh_10S_25C_Lipo_Pack.html

I know the range doesn't sound like much, but it was only a 5.8AH pack

I honestly would not recommend buying one. For one thing, it's easier to find frame bags and such to fit smaller packs, and for another, if you do something stupid like I did, maybe you would only have ruined one of several packs instead of your whole setup.

Cheers

 

[Eujangles]

I don't know all of "these" people, but I use a BMS every time I charge my pack, It's built into the rc charger and is much more accurate than any of the cheap ass BMS's used on battery packs. And all of your stupid assumptions is wrong. I know I know how a bms works, and I'd bet most of the users here do too. I know you keep putting out ridiculous advice about the use of lipo that could cause someone with no knowledge of it to cause serious damage. I also know that many people that bought battery packs with bms have had them ruin there packs because they didn't know they would ruin their packs if just left sitting for long periods of time. I know the downfalls of both using and not using a bms. Personally, I wouldn't use a bms with a lifepo4 pack either. The convenience of a simple charge port are vastly overshadowed by the down falls of using one. I don't want my battery pack cutting out in the middle of the intersection no matter how low a cell gets. And I don't want to park my bike for a month and come out to a ruined battery pack because the BMS drained a cell group just sitting there. Advocating for some one to use a BMS without pointing out the disadvantages also is just wrong. Over 10,000 miles and almost 3 years of bms free riding with lipo without as much as a puffed cell tells me I don't want a bms that limits the potential of my batteries.

Just a quick side note on this: I know that the BMS is supposed to drain one cell dead if left sitting for a while (I've been told by the guys at Grin that you're in trouble after about a month of it going uncharged), but strangely enough, a friend had an old 36v 10AH LiCoMn pack laying about for over a year uncharged (he didn't know), and just last month we charged it up and it's working just fine! No loss of range or anything; it's been through about a dozen cycles and so far so good. Very strange, but maybe the BMS ain't so bad for the battery after all!

 

[wesnewell]

First, you won't drain a lipo pack by leaving it connected to the controller over night. That's just BS. I've left mine on several times for more than just overnight. Controller drain is just too small to do that. I've left mine connected for several days and it used less than 1 volt from the pack.
Second. It depends on the BMS as to where it gets its voltage from. And your friend may have done what you are supposed to do for long storage and disconnected the bms power before putting it away. Then again, it's hard to believe anything you say after your first statement.

 

[Eujangles]

First, you won't drain a lipo pack by leaving it connected to the controller over night. That's just BS. I've left mine on several times for more than just overnight. Controller drain is just too small to do that. I've left mine connected for several days and it used less than 1 volt from the pack.
Second. It depends on the BMS as to where it gets its voltage from. And your friend may have done what you are supposed to do for long storage and disconnected the bms power before putting it away. Then again, it's hard to believe anything you say after your first statement.

First of all, that wasn't the first time I had left my bike on overnight. The other time I did it, like you said, it didn't drain really anything (maybe dropped a volt or 2 overnight), and so I didn't think anything of it. The next time I did it, and for no reason I can determine, it drained 25v and ruined the pack. I mentioned it previously in this thread http://endless-sphere.com/forums/viewtopic.php?f=3&t=51601&hilit=overnight, so unless I am running some kind of long-term, no-payoff con game, maybe I am just explaining what happened?

Second, no my friend did not disable the BMS. It's in a shell casing that has never been opened. I also know this because we talked about it, and because he didn't know what a BMS was, let alone how to disable one. Of course you would probably know better than I how my friend stored the battery...

What is the purpose of you jumping in to threads simply to be cantankerous? Every time I see you post, it seems like it's so you can mouth off to someone or show off your knowledge in the most arrogant way possible.

 

[dnmun]

on the BMSs that i am ordering now i use the 2.8V cutoff for LVC and 4.28V for the HVC because i wanna protect the pack from draining all the way to 2.7V when it accidentally drains down. with the .025V error spec that gives 4.255V for the HVC cutoff and it is really only hitting HVC when you are balancing a new pack. after the pack balances it stays very close for lipo.

even if the pack drains down the first 3 cells when supplying the circuit current for the BMS, the LVC will cut in and open the output mosfets so that it stops draining the battery then at the LVC. i think that is how it works from looking at the circuits. on these Bestechpower BMSs anyway.

 

[wesnewell]

What is the purpose of you jumping in to threads simply to be cantankerous? Every time I see you post, it seems like it's so you can mouth off to someone or show off your knowledge in the most arrogant way possible.

I'm not trying to be arrogant. I just get tired of all the crap I see coming from people that don't know wtf they're doing are talking about. At least you admitted you didn't know why your pack drained 25V. I've got a good idea, but see no point in mentioning it now. You can bet it wasn't the controller. What else did you have connected to the battery packs?

 

[heavymetalthunder]

You might also consider a watt meter sold by such companies as Hobby King and Nitroplanes. They can be installed in line and you monitor you power usage and voltage. I have a set of idiot lights for the battery on my bike and after using the Watt meter for about two weeks and figured out how much power my bike uses in relationship to idiot lights and was able to remove the watt meter.

 

[Eujangles]

I'm not trying to be arrogant. I just get tired of all the crap I see coming from people that don't know wtf they're doing are talking about. At least you admitted you didn't know why your pack drained 25V. I've got a good idea, but see no point in mentioning it now. You can bet it wasn't the controller. What else did you have connected to the battery packs?

Sorry I jumped down your throat...and fair enough, there is a good amount of misinformation floating around and I am certainly no expert. For that reason, I try to never weigh in on subjects where I don't have enough knowledge (and if I ever do, all I do is share my own limited experience as it applies to the topic and make it clear that's all I'm doing).

It was really strange...I have an in-line voltmeter hooked up, but it was there the other time I left my bike on as well, and even less than the usual stuff connected to the controller (throttle, speed switch...that's it, no CA or ebrake even). Since then, I've bought alarms to attach to my new packs, but even they don't drain the batteries excessively it seems.

Oh and also the controller was pretty hot in the morning, which is why I thought it was the culprit.