Power Consumption for Dummies

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antiscab
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Post by antiscab »

yes, uve got it exactly.

now your on to the more tedious task of will the Ping battery fit in the space of 3x12V SLA.

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Post by scooterage »

ok, i bought the 36v 20ah ping battery, he had a flat sized battery that fit perfectly into the boards battery case (by the way ping has excellent customer service, i have asked him heaps of questions and he answers quite promptly, and delivers quite quickly, i highly reccomend him to anyone) ive connected it the way ping has suggested in his guide (positive=red disharging and charging, blue = negative charging, black = negative discharging, i bought wire that takes 25amps, it was slightly thicker than the positive wire on the batteery i have charged it for about 10 hours for the first charge like he said, it flicks from red to green every 20-30 sec's ping said this is normal as the charger is balancing the battery. i took it for a ride yesterday, it went great for about 15mins, the board cut out all of a sudden, i pressed the power button on the board but it would not power up. so i disconnected the cable between the speed control and the battery and then reconnected it,pressed the button and it turned on. i got on the board, took of for about 3mtrs and it cut out again, i repeated the same thing disconnected/connected but then i turned the board upside down and tested the motor, pressed the power button and pressed the accelerator or the wireless controller and the wheel turned fine and did not cut out. I then turned the board the right way up and got on and took off...again only about 3mtrs then it cut out. what might be causing this, it worked fine for 15mins...is it just that it is a new battery and i have to charge and discharge it a few times before it reaches its full capacity?...the speed control has a cut out mechanism that triggers if the battery is insufficient battery or if there is problems.
i walked the board home and charged it...it stayed red for about 1h and 30mins, then turned green then back to red on the 20-30 sec basis.
could it be my soldering that has done this..i made sure when i soldered the wires that the solder went through as much wire as possible to give it a good connection...can i test the connection some how?

anyone have any ideas/suggestions/insight for me?

i am a little concerned on the postive connection to, as there was only one wire for it so i had to connect the one wire to two,. discharging and charging. I took about an inch of cover off the positive battery wire and about half an inch off the positive discharging and charging wires and curled the pos discharing wire to the exposed postive battery wire closest to the cover, and curled the pos charging wire at the top of the exposed positive battery wire. this seemed to be the ugliest looking connection of all the connections, as the wire is quite thick (25amp) so the soldering made it look even more bulky and very stiff.. would i have been better just to use one postive wire going from charging to discharging and split the cover in the middle of that discharging/charging positive wire and just curl the battery postive to that?

again anyone have any ideas/suggestions/insight for me?

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Post by Johny »

Even if your connections are ugly I don't think that's the reason for your low range. Lithium batteries DO need to be cycled about 3 times before they reach full capacity and I have a feeling that there is more to that too. Ask ping what he thinks is going on and specifically about care for the pack in it's early days.

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Post by scooterage »

i just took it for a test run again and it did the same thing....tho if i leave it for about 15mins, it rides normal again but just for about 15mins and then cuts out again. the guy at jaycar said it may be the heatsink in the speed control, he said that the lifepo4 batteries run slightly higher voltage than the sla batteries, and i may need to get a better heatsink or put a fan on the control, to keep it cool and prevent it overheating and using the cut off mechanism, (i tested the voltage on the ping battery after it cut out, it reads 39.4v...the original sla battery tested at 38.7v)

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Richo
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Post by Richo »

Also consider that the batteries may have a different internal impedance.
So the harder you try to accelerate the more the voltage to the controller will drop.
And possibly to the point where the contoller thinks the voltage is too low and shuts down.
The only way to know is connect the volt meter to the contoller power input and measure it when you ride.
Looking at it after won't help as the voltage will be back up again.

On the other side of battery impedance.
When you accelerate the battery pack can supply more power as the voltage drops less than the original batteries.
A lot of the skateboard controllers are quite basic and offer rudimentary control.
So the controller would get hot a lot quicker - to the point where every time you try to restart it - it overheats again and shuts down.
The way to test this is to run it until it shuts down then try run it again.
If it shuts down again straight away then leave the board for 15-20min for it to cool down - don't recharge the batteries.
If after this time you get back on the board again and it runs fine then you know heat is the problem.

So the short answer is NO but the long answer is YES.
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Post by antiscab »

this problem sounds very familiar.

how many amps do you draw? do you know?
it is most likely the BMS that is disconnecting the battery.
a quick fix would be to bypass the BMS for discharge

i had this same problem with the Yesa booster pack on my emax, mainly because i draw way more amps than the BMS would take (the Fet doing the switching got hot enough to desolder themselves from the board).

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Post by scooterage »

i tested it again...RICHO it is ur second paragraph that seems right it maybe overheating...after 15mins it cuts out..it wont start up again fro another 15mins..so it could be the control that needs to cool down,i tested it after 15mins and put the multimeter tester to the connection between the controller input and battery outputhad it upside down while i tested it so the wheel could just spin on the stand still...(i didnt recharge the battery at this point) it ran again for around 15mins and then cut out...the voltage stayed at about 39v, the board would not turn on again...so it could be the control...BUT, i then hooked the original sla battery that was tested at 39v and the board worked again fine, the control had no probs turning on again. so the remote control may not be over heating... ANTISCAB u may be right with the amps..it may be drawing too much amps from the battery which the control then uses the cut off mechanism to prevent overheating..the battery is a max continuous of 40amps and peak at 60amps..it the bms on the batt also has a cutoff mechanism if the amps get between 40-50amps (this i dont understand)...its a 36v 20ah lifepo4 batt...the original sla battery is a 36v 12ah..so could it be that the with this battery, i now have too much amps for the control to handle?...keep in mind the first lithium batt i got was 10ah and this was not enough to power the board uphill, but it never cut out....
if this is so..is there a way to make the control accept more amps or for the battery to reduce its amp output
i think i was told a coupl of pages back on this site i needed at least 22amps to run the 800w board ..and that the ping 36v 20ah with 40amp continuous would be fine..i didnt think it would deliver too much amps, just what it needed.

any ideas people?..thanks again for your help guys!!!

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Post by Richo »

Sorry I haven't looked at the details of your new battery pack.
It sounds like that it is specific to your new batteries.
It is possible that if there is a BMS included in the pack itself it maybe that a temperature sensor in the pack is causing the BMS to shut down the battery.
After 15min of use the pack gets hot and the BMS shuts the battery down.
You wait 15min for the batteries to cool down and it works again.
Maybe the way the batteries are packaged (as a 12V SLA replacement/look a like) is not allowing the heat generated in the batteries to cool down quick enough.

This is usually more the case when the impedance is high - creating more heat in the battery themsleves.
So the short answer is NO but the long answer is YES.
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Post by scooterage »

that battery or bms don seem to be overheating..the temp doesnt seem to change, thats why i was thinking it may be the control cutting it due to too much amps maybe?...it doesnt seem to overheat either...but it has a cut off to prevent that..so it might be triggered by that ...tho .. not sure...
ping (who i bought it off said it should work all handle it no probs, but i emailed him friday on my problem and he hasnt got back to me yet, being the weekend...maybe there is an actual problem with the batt?...
antiscab wouldnt not using the bms for discharge possibly inbalance the cells and possibly cause worse problems...i thought the bms needed to be there to reduce problems with lithium cells?

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Post by scooterage »

how would i keep the packs cool?...would i need to put spacing between each cell or something to reduce the heat between them?

antiscab
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Post by antiscab »

the ping batteries dont use a temp sensor (they arent nearly that advanced)

scooterage - discharging without the BMS wont cause any balance issues.
it will however no longer protect the pack from over discharge.
if this is an issue, you can use the original BMS to disable the control remotely, rather than having full current going through the BMS
this could be the form of a contactor

I personally hate the idea of a computer over-ridign one of my commands, so i never enable this on *any* of the BMS on my battery packs.

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Post by lithbattboss »

Scooterage, a guy in the USA called "mcstar" suggests on his blog the possibility of connecting a few Ping BMS boards in parallel to improve the dischargre current. You can read what he says about the Ping BMS down the page a bit here-
http://www.vistarwebtech.com/VistarWebTech/eBike/

If on the other hand the BMS is ok and your battery is pysically getting hot during use that is a bad sign (in terms of expected battery life) since (in simple/non technical terms)the chemical reaction to produce the high current demanded is struggling to keep up. You might have to either use a bigger battery or alternatively use higher discharge cells. Maybe there is a temperature sensor/thermistor somewhere in the pack which is causing the BMS to cut off when the cells get too hot?

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Post by scooterage »

well, could it be then the control cutting out the power? if the original design of the board was with an sla abttery 36v 12ah, does that mean the lifepo4 36v20ah iis over heating the conrtol which maybe cutting the power?...i dont know if it has a temp sensor...but it says that if the battery gets low or the current has problems it may use the cut off mechanism as a safety...but when it cuts out ..i swap the sla battery straight away over and the sla battery orks fine

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Post by lithbattboss »

It sounds like the voltage is dropping below the LVC threshold which is why power is disconnected. Most e-bike type motor controllers which are designed for 36 volt SLA batteries have an LVC cut off setting of approx 31 volts. If you have some way of connecting a voltmeter to the battery and watching the voltage while riding you will know for sure if the BMS is cutting off the battery due to excessively low voltage.

Antiscab is probably right in that there is no temperature monitoring but I know there were a few revisions made in similar BMS's such as the one used by Cyclone. Perhaps newer versions have temperature sensing? If the sensor is fitted to the bottom of the PCB with the wiring leading into the cells from under the board you would not know that temperature was being monitored.

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Post by scooterage »

the voltage does not drop when it cuts out and the battery is not overheating...i just had it checked with an electrician...he said the control may have a thermal cut out fuse/resistor/switch which triggers over a period of time due overcurrent from too much amps, the new 36v 20ah lifepo4 battery heats the speed control more so than the usual sla 36v 12ah battery. this is why after about 15mins it cuts out then if left for another 15mins it starts working for a while again. we are now looking at putting a resistor between the battery and the speed controller to reduce the amps so the speed control recieves the original style 12ah instead of the 20ah...

so if we put a 5 ohm resistor in series between the battery and control will that help reduce the amps before it gets to the control? (the electrician just wants me to check with u guys if his math is right,he also said the 5ohm reisiter would need to be 50-100w or higher..preferably higher.
Last edited by scooterage on Sun, 22 Feb 2009, 16:50, edited 1 time in total.

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Post by coulomb »

scooterage wrote:so if we put a 5 ohm resistor in series between the battery and control will that help reduce the amps before it gets to the control? (the electrician just wants me to check with u guys if his math is right,he also said the 5ohm reisiter would need to be 50-100w or higher..preferably higher.

Well, if you are drawing 22A, then 5 ohms is way too much; it will limit the current to about 7A. I'd say you need to replicate the sag of the original battery, which might be 1-2v (wild guess). So you want say 1v/22A or about a 20th of an ohm, up to a tenth of an ohm (0.1 ohms) at the most. It would dissipate up to 22*2 watts, say 50W. You can't really buy this as a single part from Jaycar; you might try a roll of automotive wire (leave it on the roll if you can get to both ends of it). Or get a dozen 0.1 ohm 5 watt resistors (about $4 from Jaycar or Dick Smith), and connect 3 or 4 in parallel. Try one to four sets of these in series. If you have a multimeter, try to get about 1-2v drop across the resistors when the load is on.

They will get really hot, so strap them to something metal.

This is not a great solution, but it won't cost a lot to try it out.

BTW, the additional capacity of the new battery (greater amp hours) isn't the cause of the problem. It just means the new battery will last longer then the old. It won't cause more current to flow, except that the new battery probably sags less under load (remains close to its initial voltage, say 36v, even when supplying 22A or more of current).

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Post by scooterage »

ok.i'll rule out the ah as a problem......now i am a bit lost...ok how do i check how much amps the control draws? i can easily check the voltage, but all multimeters only go upto 10a so is there some other way on the multimeter i can get a read of the amps drawn?
I guess i could also test skateboard bypassing the bms discharge..if it doesnt cut out i'll then know it is the bms cutting the battery...but if it does still cut out after 15mins it would be the control doing it right?
if it is the control over heating i can't tell this by touching it because the heatsink is the control box..so the speed conrtol is inside the heat sink...we tried to open the heat sink to get a look at the control board but can only open the side parts of it as the manufacturer seal the slide case (which is the heatsink) and has lined the whole inside with black glue tar looking stuff and it is also stuck to the top of the capaciters which are then stuck to the top of the slide part to open it...they really dont want u opening this thing.
ok..so if it is just a heat problem with the control...how do i fix this..put a fan on it like the jaycar kid told me?..use a resister like the electrician said and the way coulomb suggested?....
if it is the bms cutting out the power (tho the battery doesnt feel hot when the skateboard cuts out...will using a second bms to improve the discharge current fix this problem?

this is becoming more trouble than its worth..2 lithium batteries ive gone through and the skateboard doesnt like either...one is not powerful enough..the other seems too powerful..aaaaaaahhhhhh!!!!!!i don't want the $1100 ive spent on 2 batts go down the drain)
any of you guys in sydney can help me out? i'll take the board around to ur place and show u what is happening..this is becomeing a nightmare for something that seem pretty simple

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Post by lithbattboss »

So to get this straight, the skateboard only has the problem of cutting out with the lithium batteries you have fitted. Did it ever have the same problem with the SLA's?
Can you replace the controller with a higher power unit?
What part of Sydney are you in scooterage?

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Post by Electrocycle »

I can lend a hand and do some testing.
I'm near Hornsby.
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Post by scooterage »

yes it only cuts out like this with the lithium battery, not with the sla...id like to replace the controller with i higher powered one but the the company only sell one type of control for the 800w board (ive seen in the uk they have 800w boards with lithium batts..but 12ah and they use the same control as the sla batt...but it is not my control..but the same concept..they dont have a different control between there sla and lithium...tho it is the same 12ah for both)and id love to make a new control for it but would have no idea where to begin with that!! lol......and the elecrician that looked at it yesterday said it looks like it also controls the power going to the reciever for the wireless hand remote accelerator controller.
but if u know how to make a new one or help me in any way, it would be awsome!!!!...i live in the lower blue mountains (blaxland)...but work in eastern creek and five dock...but to be honest i'll travel anywhere in sydney to anyone that can possibly fix the problem!!!

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Post by scooterage »

my email address is happyblessings@gmail.com...if lithbattboss or electrocycle can email me so i can work out a time and date and address that would be great!!! thanks guys!!
i just emailed an electrical engineer at an all experts site the details of my problem and they said to use one or two 0.1 ohms 50w resistor in series if that stops it from cutting out but if it runs too slow to put it in parallel and it should create the sag required (like coloumb said)

http://www.allexperts.com/user.cgi?m=6& ... ID=4824241

....now does anyone know where i could get 0.1ohm 50w resisters? (jaycar only go up to 10w ohms resisters)

but they also said the bms may have an internal limiter that opens up if the internal temp gets too high which u cant check external by touching the battery.. but some one said here that the ping bms doesnt have that sort of thing...and why would a brand new battery would be heating like that unless its faulting , i dont know...but i dont know a great deal as u guys ... this is all getting beyong me...my brain is hurting lol!!
Last edited by scooterage on Mon, 23 Feb 2009, 08:49, edited 1 time in total.

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Post by antiscab »

id say your best bet is to find the shunt resistor inside the controller, and increase its resistance.
usually it wil be made up of a few strips of nichrome wire (i think its called nichrome).
ill try and find an example pic.
This will lower motor side amps, (and performance) and reduce the controller heating rate.
This will be cheaper than adding a resistor to the battery (and much more efficient)

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Post by scooterage »

[quote="scooterage"] the speed control is inside the heat sink...we tried to open the heat sink to get a look at the control board but can only open the side parts of it as the manufacturer seal the slide case (which is the heatsink) and has lined the whole inside with black glue tar looking stuff and it is also stuck to the top of the capaciters which are then stuck to the top of the slide part to open the heat sink ...they really dont want me opening this thing.


i couldnt open the heat sink completely enough to get a good look at the control board..its really sealed tight..so i cant change anything in the control...id like to, but u gotta see this thing!!!

i'll try and take some photos so u can see what i am dealing with trying to open!! even the control board face is lined with this black hardened goo stuff so i may not be able (even if i open the heat sink), to replace the reister to a stronger one
Last edited by scooterage on Mon, 23 Feb 2009, 07:54, edited 1 time in total.

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Post by Johny »

Hi scooterage. My 2 cents worth.
If you want to prove that it's the controller and not the battery pack.
1/ Run it on the Lithium pack until it cuts out.
2/ Replace the pack with the SLA pack as quickly as you can.
3/ Run it again
If it cuts out after a tiny amount of time (as with the Lithium), then it's the controller.
If it goes OK, put the Lithium pack back in - again quickly and run it again. If it cuts out quickly then it's the Lithium pack.

At least that way you will absolutely know if it's the pack or the controller.

I think your earlier post indicated that you had measured the pack voltage DURING the cut-out time and while it was attempting to power the board - and the pack measured 39 volts or so. Is that correct?
One other question - does the board appear to have lots more power on the Lithium pack?

It is possible to de-pot the controller (extract it from all the black goo). Some of the guys you are talking to can probably even test it up to the point it cuts out without the board so you can see if improvements have been made. My guess is that it is overheating internally.


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Post by scooterage »

thanks johnny...u got it thats exactly what is happening...ok..sorry i am so slow and confused with all the info i am recieving...the lithium cuts out in 15mins...i put the sla straight on after and it works fine, i put the lithium back on and it cuts out pretty much within 5secs or immediatly....
yes the volts measured 39volts when it cut out...
the board doesnt seem to have more speed with the lithium (the speed control maybe hold it back from going faster...not sure)but it goes up heavy hills alot easier...u dont feel the lag the sla had...sla u could feel it was drawing alot of power just to keep it going but it got me up those inclines ok...where as the lithium took the hill fine with little lag at all. maybe it was those hills doing it..i would use a few hills to test it power, it work great...but at times testing it it wouldnt matter if it cut out going up hill or down...it woulld be that it took about 15mins of ridingg to do it.
so if it is the battery heating internally which is causing the bms to cut out causing the problem..does that mean its faulty and i should send it back to ping? or is it just how all lithiums at 20ah will work?...would putting a second bms fix it? or is it just the what i am hooking it up to which is causing it to over heat?
how do i stop the cells overheating internally
Last edited by scooterage on Mon, 23 Feb 2009, 10:27, edited 1 time in total.

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