Complete Hobby King Lipo Protection Kit

[methods]

Can you explain the reasoning behind the cutoff threshholds of 3.0V LVC and 4.29V HVC?

3.0V to 4.2V is the commonly accepted range for Lipo. Setting cell level LVC to 3.5V would = fail because you would be bouncing off of LVC under load all the time. I understand the practice of discharging to only 3.5V but that can be done by the user watching voltages. Would not make sense to set hardware limits here. If you really want a limit that high use the CA pack level LVC Limit... no need for cell level protection when so far from cell limts.

The 4.29V comes from the fact that these are 18650 production parts - they were accounting for high internal resistance and the dynamic charge current verses the resting voltage. The reality is that if you were to cut charge at 4.2V under load it would settle to way below 4.2V - so cutting at 4.29V will usually result in a resting voltage of 4.2V. Again this is a situation where the user may choose to under-utilize the capacity of their batteries in order to gain a perceived increase in cycle life... but this can be done by simply setting the charger to a lower voltage. It would never make sense to actually set the hardware limit lower.

These boards are first and foremost developed for the motorcycle racing scene... and you better believe that those guys are getting as many wh into their packs as they can. I have seen many a rider pushing bikes across the finish line. The hesitancy to do deep cycles wears off quick in that community.


I'm guessing the device is intended as a last resort fail safe to prevent destruction of the pack rather than the regular means for terminating either charge or discharge,

The proper method for terminating charge is by setting the charger to the correct voltage for a balanced pack. I dont like the idea of relying on a BMS to terminate charge on a regular basis... this is how fires start. The Battery must be able to be hooked to the charger with no BMS for safe operation at all times.

For LVC -> I never recommend that people empty their packs - so the proper way to do this is to set Pack Level LVC in the CA -> that can cut one off early... but one still has the choice of getting more if they have a few miles to go.

Are the cutoffs modifiable? I'd expect a tighter range, say 3.5V LVC to 4.2 HVC would be fine for many like myself who try to keep their batteries in a 3.7 to 4.1 volt operating range and don't want their occaisional screw ups to go too far out of bounds.

These values are not out of bounds. I think folks have taken this idea WAY too far... Lipo is meant to be run from 3.0V to 4.2V. I have thousands of cycles on RC packs where I run cells down to 2.5V and up to 4.3V over and over and over. I dont buy any of this hype about extended cycles -> the reality is that prices are dropping so quickly that by time one actually gets 3,000 cycles out of a pack... that pack is now totally irrelevant in terms of C rating and power density.

I paid $150 each for the 6S 4.15Ah packs I built my first bike with. They were 15C. Now I can get 20C packs for $40 that are 5Ah. I beat the hell out of those original packs and they are *still running* on another guys bike who I just gave them to.


-methods

[methods]

Good answer, in a lot less words

-methods

The reasoning and the voltages have been explained a few times in the various threads for this but basically that's what the parts are avaialble in, so no there's not really the option for other voltages.

It is indeed just a failsafe device, last ditch don't-destroy-your-pack kinda thing. For your regular LVC, you'd want to go with a pack LVC on your controller, Cycle Analyst, or whatever else you have on there. Regular HVC is the voltage on your charger--don't set it higher than pack voltage should be, and then it shouldn't overcharge unless there's a balancing problem, and that's the case this system is there for.

Can you explain the reasoning behind the cutoff threshholds of 3.0V LVC and 4.29V HVC?

I'm guessing the device is intended as a last resort fail safe to prevent destruction of the pack rather than the regular means for terminating either charge or discharge,

Are the cutoffs modifiable? I'd expect a tighter range, say 3.5V LVC to 4.2 HVC would be fine for many like myself who try to keep their batteries in a 3.7 to 4.1 volt operating range and don't want their occaisional screw ups to go too far out of bounds.

[SpeedEBikes]

Thanks, I just finished reading 12 pages of this thread (been out of the sphere for a while) and didn't see it mentioned.

I've been relying on cell log 8s to provide a programmable high cutoff and low alarm for per cell protection. The biggest downside is a bit of effort to rewire each unit with a more robust alarm connector and add a power switch as the standby load is a bit high. That and I have to make parallel boards for the balance connectors.

The no fuss always on aspect of this setup is appealing, but the cutoff values strike me as the biggest drawback for my purposes.

[Jay64]

Has anyone come up with a way to secure these boards once they are wired to the battery?

[methods]

Velcro on the bottom of the heat shrink is what I have seen Matthew do.
In most cases (for smaller packs) the leads are so short that they are kind of held in place. For a large motorcycle pack like yours I suppose thats not the case.

Rubber band?
Zip Ties?
Kapton Tape?
Contact adhesive?

Kapton tape is nice because it uses a really clean silicone adhesive that leaves no residue, has great electrical characteristics, have a huge temperature range, and is pretty much just sent from heaven. Best tape ever for electronics.

You can get it in many thicknesses and widths - be careful with the thicker tapes as they may want to peel up (they are meant more for short, straight, insulating applications). The super thin stuff holds well across temperature and is cheap.

-methods

[Jay64]

Cool. So it is ok to have the bottom solidly mounted to the battery, even if it is a hard box? I was just worried about possibly damaging the components on the bottom. But if that is not an issue, I'm good.

[methods]

Well...
I suggest that most people cover them with the supplied heat shrink to stop vibration from rubbing-rubbing-rubbing through the silicone conformal coating. I was thinking you would then mount that heat shrink to whatever solid surface you have available.

As far as shock and vibration - I am comfortable with them being mounted directly - though a foam tape could make an incredible difference. I did a lot of shock and vibration testing at my old job and even the thickness of a single slip of paper can incredibly attenuate the peak of a shock profile.

Try and keep the boards dry - that is the most important thing. It is ok if they get wet - but try and dry them out after the race. Standing water is our enemy.

Water = ok
Time = ok
Time + water = fail.

BTW Folks: We are stocked up on the 5S and 6S jumpers and they are $2 each. We have the 6S in 12" and the 5S in 6" and 12". Soon we will have the 6S in 6" as well as 4S in both 6" and 12"

-methods

[Jay64]

Great to hear that these are so robust. I was Treating them like they were a faberge eggs or something.

[methods]

Ha... yea... I regret having to sell them as a raw circuit board. If someone with more talent than myself could show me how to package them in a more clever way I would be all over it.

The Epoxy was just a nightmare

I look to the Chinese all the time for ideas - the RC guys know how to do good robust packaging on the cheap. I like the thick rubbery heat shrink that the BM6 units come in - I have a hundred feet of it but it is too small for these.

The boards are tough - the only reason I would baby them would be to avoid rubbing off the conformal coating. Electrolysis is our only real enemy.

After race season is over if they get the crap kicked out of them I can write up a tutorial on how to re-coat them for added reliability. The US circuit is not that wet though - so I dont think you have that much to worry about. Over in the UK things are different - that awful place is wet and cold and miserable 24/7

-methods

[Kin]

You might not have enjoyed epoxy- would a silicon based clay like http://sugru.com/ be better? You can make a cheaper version http://www.instructables.com/id/How-To- ... ubstitute/
It's basically just gorilla glue, silicon caulk, and corn starch. Might still add a bit of effort to the boards, and I know you want to keep costs down- so maybe not useful.

[methods]

The first link broke but I saw the second. Looks cool - thanks for sharing

Well... it is not so much the cost anymore. We already have enough epoxy to cover the statue of liberty - the problem is really getting the viscosity right so that it is thin enough to release the bubbles but thick enough not to run into the connectors. A huge part of the problem was working around the JST's - but since the next batch of boards wont have parts on the JST side we may consider trying Epoxy again.

Anyway - the trouble is that it is hard to make a mold that will allow us to do 8 boards at a time. With the silicone I just clean the boards well in the ultrasonic (with Iso) then clean them again with 99%, then compressed air - then I just blast them with the spray on coating 8 at a time and set them in my little heater curing box to speed things up. With the epoxy we really need to break them up into individual boards and do them one at a time. It turns into a race to beat the 5min epoxy or a waiting game for the 30min to cure.

Sigh...

I love epoxy actually - I just have not figured out how to use it wisely.

I invested pretty heavily in the gear to make silicone molds. This is an AWESOME platinum cure silicone that sets up in only an hour and requires no de-gassing. I suppose we could make a monster-mold that does a sheet of 8 boards at a time. We could then run a thicker epoxy (so it does not sneak down and around) and mask the micro-bubbles by adding a pigment. Vacuum wont work because it sucks the epoxy into the JST connectors.

But... even if that works we are still left with the other side of the board. On that side electrolysis can still attack the via's. I left this batch of via's tented - which will really help combat conductivity between points - but none the less it needs to be insulated in some way. I suppose we could paint a thin coating of epoxy on that since there are connectors but no parts.

Anyway - thanks for the help! I will check that Tek out.

-methods

[Arlo1]

Mehty If you get your mixing technique just right and you use some heat you can usually get all the bubbles to the surface. Maybe try different epoxy? Something runny with a long cure time.... I just got some eBay hi temp stuff and its really slow to cure! But this means you can keep heat on it to make it thin to let the bubbles out. Another note is to preheat the item you are about to resin then lower the temp once the resin is on it this will make a small vacuum anywhere there is an air bubble. I had to do this with my many CF projects.

[Alan B]

I heard standard procedure on epoxy was to mix with proper technique to reduce bubbles and then use a vacuum pump to get the remaining bubbles out.

[Jay64]

Unless you can't use a vacuum in order to keep it out of the JST connectors.

[amberwolf]

Vibration is another way to help ease the bubbles out. When I used to make sci-fi props and models for conventions, sometimes I'd have to cast parts out of resins, or use silicones for part molds. To get bubbles out, I'd use runny long-cure mixtures, and set them on an old linear amplifier I had with a huge power supply transformer that always vibrated badly with 60Hz hum. It got a lot of bubbles out, and if I mixed carefully I could end up with something very usable for clear stuff between the two.


Another way that was suggested to me, but that I didn't ever try, was to mix up the epoxy as runny with long cure time, then vacuum the *container* to get the bubbles out, and *then* pour the epoxy, or use syringes to inject it to minimize surface bubbles. The same thing was suggested to me for silicone molds, using platinum-cure types of silicone (like what TAP and Reynolds sell).

[methods]

Something runny with a long cure time....

Right... I have at least 5 different kinds
The trouble with thin epoxy is that it sneaks past the mold and gets into the JST connectors.

I totally agree that with thin epoxy I can get beautiful results... but to get them I have to really have a good seal on the mold.

-methods

[Arlo1]

Something runny with a long cure time....

Right... I have at least 5 different kinds
The trouble with thin epoxy is that it sneaks past the mold and gets into the JST connectors.

I totally agree that with thin epoxy I can get beautiful results... but to get them I have to really have a good seal on the mold.

-methods

Try heating the board first with thick epoxy then.... I used to get a lot of bubbles till I started preheating my work.

[Kin]

Hmm, now I don't want to waste your time, but I'm struggling to see how the epoxy gets into the JST connectors. Don't they have a little bit of a plastic wall protecting them? And is the problem that they're getting into the female connectors side [as opposed as through the bottom pins somehow?

I'm just not sure how they could get vacuumed in.


If you're interested in that silicon clay stuff I linked early, I could probably whip some up and send a bunch to you, but honestly only next weekend (after finals). I happened to notice I have a tube of new unused silicon caulking that I bought ~7 to 8 months ago, and it probably won't be worth it to bring the tube back home and it'll be no good by the end of summer. I also have the corn starch and gorilla glue that is needed. Let me know if you have any interest because this is something I wouldn't mind doing and I assume probably wouldn't cost me much to ship. Perhaps you could use this as a easy to apply border to protect the JST connectors, rather than as a full replacement for the epoxy.

[NeilP]

First admission, I have not yet read this entire thread, I just came here from a methods site, via the site link

I have just been asked about an electric outboard motor for small inflatable boat, they want power for it but not lead acid. They had a accident a while ago passing lead acid ( non gel type) down a ladder from the dock to the boat. They came to me since I
" seem to know about battery's, since you are the bloke with the fast e-bike, right?"

So I said yes and offered to help

Looks like it is a 12v unit, not sure how high up it can take, but hoping 4s LiPo will be OK

I have told them they will need charger, but they want to run a solar panel to keep it topped up

So to the point of all this, will this board be usable to act as cut off for HVC To prevent overcharge from a solar panel

[Alan B]

The HVC cutoff on these units is not intended for normal charging, only for a safety net. The charger should have its own voltage regulation.

4S LiFePO4 is a better match for a 12V application. LiPo voltage is a bit high and might damage any electronics on the motor if there are any.

[NeilP]

That is the thing, I was hoping to get away with no charger, just enough solar cells and a diode or two to fine tune the voltage
Needs to be simple minimal components on the boat/ pack

Will get them to get a balance charger for shore/ main boat charging, but just really wanted a safety cut off relay run from the HVC for when the solar panel is connected up and trickle charging it

Alternate would just be less solar cells to keep max voltage when cells in max daylight to below or just at 4 volt per cell


I have sent the motor people a mail to find out more about the working voltage range of these motors and their controllers

[methods]

There are more cost effective solutions for that particular problem.

I like 4S lipo for a Lead Acid replacement but the hot voltage is 16.8V which trips up some DC-AC Inverters and other "smart" electronics. It will be fine for most things that plug into a ciggy lighter though - as car 14V is noisy as hell.

I guess the important thing is the load they are going to run and for how long.
IF they are not pulling 80A then you could go with a MUCH cheaper 18650 Laptop cell pack with a built in BMS for total protection.

-methods

[methods]

Oh yea...

A couple of days ago Matthew and I took a 30 mile ebike ride. I had a 24S 20Ah pack and he had an 18S 15Ah pack. His pack was almost new and we had no reason to believe there was a problem. 12Ah into the trip his cell level LVC started tripping... The pack was still at 66V~!!! We had pack level LVC set at a conservative 58V - and that was useless. One group of cells was already at 3V when the rest were still up near 3.7V.

It was pretty awesome seeing the system actually work in (what I would consider) a bit of a freak situation. Neither of us thought he had a problem with his pack...

Makes me want to install a system on my pack

I mean... those cells still have to be replaced so it is not like it saved us any money... but I am not sure what would have happened if we had pulled 3AH more through those cells. I suppose we could have reversed them - though I have never done that with a pack. I think Lyen did once

-methods

[Jozzer]

Oooh, nice catch!

I've seen a few cells go through reversal in customers packs - without protection it is inevitable I think. Worse still is if you were to have stopped riding after discharging them a little further, then bulk charged them - that might have been interesting!

As you say, you didn't save much money in this particular case, but if you have packs in parallel then you lose paralleled cells needlesly (important when you have 20 odd Turnigy in parallel!).

[NeilP]

There are more cost effective solutions for that particular problem.

I like 4S lipo for a Lead Acid replacement but the hot voltage is 16.8V which trips up some DC-AC Inverters and other "smart" electronics. It will be fine for most things that plug into a ciggy lighter though - as car 14V is noisy as hell.

I guess the important thing is the load they are going to run and for how long.
IF they are not pulling 80A then you could go with a MUCH cheaper 18650 Laptop cell pack with a built in BMS for total protection.

-methods

I was working on 16.6 voltsd..4.15 need to see what the voltage range is when they get back to me

Curent draw is not an issue. 42 amps max draw, and I was thinking of a 20Ah pack. so even basic Lipo is nicely within range, not needing the expense of Nano Tech.

it is just down to what the max safe working voltage of their controller is..am waiting on a reply from them