Turnigy Multistar - lightweight 10C cells

[neptronix]

Typical discharge curve for most zippy/turnigy RC Lipos. I don't have a discharge curve on hand for the multistar, but i'd suspect it is similar.

 

[icecube57]

3.7v is the resting on a Multistar at 85-90% DOD. This is a photo taken on my pack its a 44v 40AH multistar pack and I discharged 35AH out of 40AH. This is the voltage the pack cells were at.

 

[gblast123]

I guess the difference is that most bms allow lipo's to discharge to at least 3.0v.. in some instances the cut-off is 2.7 v.

I agree that if u want to keep the pack alive for the longevitiy, the parameters you indicate would do so.

However, there comes a point of diminishing returns.. i generally let my pack go down to 3.0v per cell..and u are right, there is noticible sag below 3.5 or so.

But that is a choice.. not a scientific principle...the choice is to maximize battery life.. and in that case, he is correct.

But to say that something is "almost empty", is clearly not based on the science.. it is based upon personal choice.

 

[parabellum]

I guess the difference is that most bms allow lipo's to discharge to at least 3.0v.. in some instances the cut-off is 2.7 v.

I agree that if u want to keep the pack alive for the longevitiy, the parameters you indicate would do so.

However, there comes a point of diminishing returns.. i generally let my pack go down to 3.0v per cell..and u are right, there is noticible sag below 3.5 or so.

But that is a choice.. not a scientific principle...the choice is to maximize battery life.. and in that case, he is correct.

But to say that something is "almost empty", is clearly not based on the science.. it is based upon personal choice.

You dont get it, there are about 15% capacyty left from 3.7V to 3V. So, it is not a "personal choice" it is a FACT. :lol: So yes, you can bulkcharge those 15% and then "top off" the resting 85% if that is your "personal choice"

 

[Alan B]

Try an experiment, charge to 3.7V and see how many amp hours you can draw before they fall off the cliff. Normal charge is 4.2, many charge to 4.1. Charging to 3.7 won't push it up the energy curve very far. You cannot compare charging to discharging voltage.

 

[gblast123]

I guess the difference is that most bms allow lipo's to discharge to at least 3.0v.. in some instances the cut-off is 2.7 v.

I agree that if u want to keep the pack alive for the longevitiy, the parameters you indicate would do so.

However, there comes a point of diminishing returns.. i generally let my pack go down to 3.0v per cell..and u are right, there is noticible sag below 3.5 or so.

But that is a choice.. not a scientific principle...the choice is to maximize battery life.. and in that case, he is correct.

But to say that something is "almost empty", is clearly not based on the science.. it is based upon personal choice.

You dont get it, there are about 15% capacyty left from 3.7V to 3V. So, it is not a "personal choice" it is a FACT. :lol: So yes, you can bulkcharge those 15% and then "top off" the resting 85% if that is your "personal choice"

You have trouble with engrish I see. If you bothered to read it careful, it says.

"In a pinch, i can use the regular 24v charger that comes with the mobility scooter to bulk charge the pack up to about 3.7v per cell."

I did not say that is was the preferred method was bulk charging.. ie.. "IN A PINCH", means if you see your pack is down in voltage, and you have the regular charger that comes with the mobility scooter, you can get some extra milage out of it.

I dont know about you, but I dont usually carry around a balancing charger with a power supply when i leave the house.

The preferred method is to balance charge these packs at an appropriate c rate. Why you and others get their panties in twist over what can be done.. "IN A PINCH'..is simply ridiculous.

 

[gblast123]

Try an experiment, charge to 3.7V and see how many amp hours you can draw before they fall off the cliff. Normal charge is 4.2, many charge to 4.1. Charging to 3.7 won't push it up the energy curve very far. You cannot compare charging to discharging voltage.

I agree that it won't push it up far.

Do you agree that "IN A PINCH" something is better than nothing?

 

[hydro-one]

i will not discharge below 3.7 resting voltage. so i set my pack level bms at 3.7v per cell. this keeps cells from getting killed off, if there is a slight imbalance in the pack. there is very little useful energy to be had below that. mega sagville

 

[gblast123]

i will not discharge below 3.7 resting voltage. so i set my pack level bms at 3.7v per cell. this keeps cells from getting killed off, if there is a slight imbalance in the pack. there is very little useful energy to be had below that. mega sagville

that is your choice..nothing wrong with that

 

[Ohbse]

i will not discharge below 3.7 resting voltage. so i set my pack level bms at 3.7v per cell. this keeps cells from getting killed off, if there is a slight imbalance in the pack. there is very little useful energy to be had below that. mega sagville

that is your choice..nothing wrong with that

Discharging below 3.7v on HK cells delivers very little energy and damages cells over time. You're technically correct, there is energy to be had discharging below this point. You're also technically correct that bulk charging to 3.7v is 'better than nothing' however it's a stupid idea that will result in a poor experience - hence the advice to make other charging arrangements. Your defense of a bad idea as a personal choice is just embarrassing yourself, I suggest you listen to people with direct experience with these exact batteries as to suitable set points.

 

[neptronix]

3.6v is where these cells hit the cliff and you only damage them if some cells go below 3.0v.

But as you see in my graph, the cells you get will vary in capacity slightly. Once you hit about 3.6v average across the board, you've probably got a nice spread from 3.2-3.65v across all cells. At that point, it's certainly time to stop discharging.. unless you have a BMS... then feel free to extract the last ~1-5% of the pack's capacity.

 

[gblast123]

I'm not sure why people cannot understand plain english and are simply getting on pulpit trying to show off how much they know.

In a forum predicated on scientific principles, there is a tremendous amount of inaccurate breastbeating about what is the "right" way to do things.

Quite simply, we are all human, we all make mis-calcuations/approximations in the use of our battery packs.. this is an inherent weakness of all electric powered vehicles, esp. electric bikes.

It is difficult, if not impossible to exactly calculate all the variables regarding bike usage in any given instance. Road conditions, tire pressure, air temperature, etc.. all affect how much power u will utilize in a given instance.

I simply cannot believe that everyone who has commented here, has never had an instance where there were stuck someplace with a battery pack with a voltage of 3.7v per cell or less.

I made a simple statement.. ie, "IN A PINCH".. which to the average person means an expected occurance.. a miscalculation.. which happens.. for some, more frequently than others.

What do all the above commentators do when it happens to them, pedal or walk the bike home?.. obviously not.. you nurse the pack home and charge it up asap.

For the pundits to use terms like "almost empty" or "Discharging below 3.7v on HK cells delivers very little energy " is seriously pedestrian in a forum such as this. How do u define "very little energy" or "almost empty".

Look at Neptronix graph.. from 3.7 v to the end of the cliff, you are looking at an additional approx 9 full minutes... out of a 32 min usage curve.

So, if u find that you have made a mistake or a mis-calculation, and are stuck with a pack that has fallen below 3.7v, it is better to get the voltage up to 3.7 AT LEAST.. with a simple charger that is readily available in most places..it is not the best way, but as an alternative to doing nothing, it is a much better solution.

Please bother to read this 2X, cause it seems that you don't seem to get this the first time you all read it.

 

[Alan B]

If you are going to bother to carry a charger, you might prefer to get one that will be worthwhile of the weight. The one you have was not designed for this use and will probably produce very little charge, and it will likely do it very slowly. You need to test it and monitor it very carefully to see if it is even safe to use, or if it produces any useful charge at all. Lead acid chargers have various techniques for charging, and they vary from smart to very simple. Drain your pack down to 3.5 or whatever minimum you plan to use, and apply this charger and measure the energy it puts in, and see how long it takes. The charge rate is likely to be slower than walking your bike home, and the range may only get you a few houses down the road before needing another charge boost. But you will not know until you test it. People here are just telling you in their own way that they wouldn't bother with it, but if you intend to use it you absolutely should test it ahead of time so you know what it will do for you.

 

[miuan]

In a pinch, i can use the regular 24v charger that comes with the mobility scooter to bulk charge the pack up to about 3.7v per cell.

3.7V per cell is almost empty.

I think a look at any Lipo discharge curve would indicate that your statement has little to no merit.

But take a look and get back to me on this.

gblast I did take a look. However, you need to look at CHARGE curve, not discharge as you wrongly assumed.
You are not getting more than roughly 7-10% capacity in until you hit the slowish CV phase. Provided the lead charger ever gets to 3.7/cell.
Operating the cells at these voltages makes no practical sense and will shorten their life and hinder their performance. Therefore most folks advice against it.
Get a proper charger set to correct cutoff voltage and operate them at lower IR and farther from the lipo cliff.
Very sorry for the full page of clarification that my simple sentence caused.

 

[icecube57]

The voltage sag is horrible on a pack that has cells in the last 10% of their life.It is very unusable even if you limp that bitch home at 10mph. Also you have to look at how many amps would flow into a pack when the difference in voltage isnt that much. So it may give you a slower recharge time which would not be in a pinch at that point you could probably pedal home faster than you can recharge to get the 10% you are trying to snag. You need to start looking at post counts and years on the forum before you start bashing people. We are trying to give you some firm love and tell you what you are about to do is stupid but if you want be a stubborn jackass and yell shenanigans like YOU know it all then be my guest. But think you have 5 or so seasoned forum member telling you not to do it . No one has supported your idea.

 

[miuan]

Hurry guys, the 16Ah bricks are now in stock at EU Warehouse!

 

[KINNINVIEKID]

Hurry guys, the 16Ah bricks are now in stock at EU Warehouse!

And the UK
Just bought a couple more :wink:

 

[Offroader]

If you use 32 amp hour of these cells will their be any problems drawing 80 to 100 amps peak? Will the voltage sag be noticeable compared to my 20C turnigy cells?

I only ask because I see some people complaining here.

Or is the weight savings well worth the small voltage sag I may get?

Thanks

 

[striker54]

I hope they can sustain the 2.5C continuous rate with no major voltage sag, according with icecube's tests, because i will use them with the adaptto max-e and cromotor.
I will use a 22s 40Ah pack (16ah+16ah+8Ah), so in theory good to 100A continuous.

 

[Offroader]

I hope they can sustain the 2.5C continuous rate with no major voltage sag, according with icecube's tests, because i will use them with the adaptto max-e and cromotor.
I will use a 22s 40Ah pack (16ah+16ah+8Ah), so in theory good to 100A continuous.

Yeah I am planning on using it with the cromotor and max-e at 22S also.

What type of bike do you have where you can fit a whopping 40amp hours at 22s. That's a very large pack.

 

[striker54]

I hope they can sustain the 2.5C continuous rate with no major voltage sag, according with icecube's tests, because i will use them with the adaptto max-e and cromotor.
I will use a 22s 40Ah pack (16ah+16ah+8Ah), so in theory good to 100A continuous.

Yeah I am planning on using it with the cromotor and max-e at 22S also.

What type of bike do you have where you can fit a whopping 40amp hours at 22s. That's a very large pack.

Vector frame
I have to start a build thread :wink:

 

[icecube57]

I have tested the 16Ah cells and I approve for 3C or 48A use. I just did discharge tests and they hold above 3.5v for 15.8AH and deliver 16.7AH down to 3.0v. Im going to do 1 more test to 4C or 64A. This will let me me know if I can run 1P on a 65A Lyen Controller with acceptable sag. the 3C test surprised me.

 

[icecube57]

Test charts and data for the 16AH Multistars.
https://scontent-a-atl.xx.fbcdn.net/hphotos-xfa1/t31.0-8/10548328_10152537041706073_3630190061682242192_o.jpg
https://scontent-a-atl.xx.fbcdn.net/hphotos-xpf1/t31.0-8/10929070_10152537041701073_585513403898019709_o.jpg
https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-xpa1/t31.0-8/10917778_10152537041711073_7982135348547953073_o.jpg

 

[Offroader]

I hope they can sustain the 2.5C continuous rate with no major voltage sag, according with icecube's tests, because i will use them with the adaptto max-e and cromotor.
I will use a 22s 40Ah pack (16ah+16ah+8Ah), so in theory good to 100A continuous.

Yeah I am planning on using it with the cromotor and max-e at 22S also.

What type of bike do you have where you can fit a whopping 40amp hours at 22s. That's a very large pack.

Vector frame
I have to start a build thread :wink:

I can't believe you can fit that much in that frame, I don't think the raptor could fit that much. I would relook over everything to make sure. I'd be shocked if that can all fit.

 

[icecube57]

The multistars offer 20-25% more range in the same space as regular lipo
.