GoldenMotor.com Forum
General Category => General Discussions => Topic started by: Enpro on February 16, 2012, 07:46:04 PM
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My two 36v/15ah goldenmotor lifepo4 packs (rated for 30amps continue,60 amps peak according to goldenmotors that is..) in series and already after a couple of miles the lcv kicks in.
I got them hooked up to a 72v 45a crytalyte controller which is a little too much I know but even if I run only at half throttle the same thing happens.
At full charge they both measure 41v and after the lcv one pack reads 41v and the other 39v even with diodes. (without diodes same thing happens)
Faulty pack or am I just pulling too many amps?
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Do you have any means of measuring the actual voltage and current being used when it cuts out? This would give a good indication of whether the batteries were continuously being worked too hard, forcing the weakest one to shut down first.
Unless the LVC is higher on the GM LiFePO4 packs, I would expect the individual battery voltage to be around 32V under load before the battery's LVC should cut in.
Alan
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okay this is whats happening.
Full charged packs (81v) only drop to 70v max at fullthrottle.
After 4 km of easy low throttle riding combined voltage starts to drop to 79v (Pack 1= 41v , pack 2= 39/38.6)
Then voltage drops to 68v when full throttling only for a few seconds.
Then aftr couple minutes more riding lvc from pack 2 kicks in and pack still measures 38.6v
Trying to restart, lvc kicks in at only 5v sag and like 30% throttle.
And does anyone know the exact specs of the cells that are in these packs?
I found a few lifepo4 cells with 16ah and they are rated at 160amps continuously
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My two 36v/15ah goldenmotor lifepo4 packs (rated for 30amps continue,60 amps peak according to goldenmotors that is..) in series and already after a couple of miles the lcv kicks in.
I got them hooked up to a 72v 45a crytalyte controller which is a little too much I know but even if I run only at half throttle the same thing happens.
At full charge they both measure 41v and after the lcv one pack reads 41v and the other 39v even with diodes. (without diodes same thing happens)
Faulty pack or am I just pulling too many amps?
I know this may not help. But exactly what batteries do you have. I have not heard of 36v15ah gm batteries.
The Lithium we had were 36v16
The LiFePO4 we have now are 36v12
These are the aluminum cased batteries. Is that what you have? Do you have a picture of your batteries and possibly the label. I know this will not resolve your issue but more clarity can't hurt.
Gary
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I can't really find much info on these batteries to start with but they are the second ones on this page. www.goldenmotor.com/batterypack.htm (http://www.goldenmotor.com/batterypack.htm)
And also the box in which they came says lifepo4 so really hope they are because if they are just limno2 that means they have a lower discharge rate and I'm wrecking them for sure now.
I will post some pics of the inside of one of my packs so you can see exactly what's in them.
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Here are the pics I promised:
Please ignore the horrible paintjob ;D
(http://img833.imageshack.us/img833/8928/20120218131755.jpg)
It clearly says lfp 3616s so doesnt that meant its a lifepo4 pack?
There are 40 cells in the pack
(http://img525.imageshack.us/img525/2355/20120218131659.jpg)
Group voltages are 4v per 4 cells which is kind of strange for a lifepo4 cells?
(http://img88.imageshack.us/img88/3275/20120218131646.jpg)
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That does looks like the LiMn cells to me... ???
Without knowing for certain; I thought they used those square cells in LiFePo packs?
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I totally agree with Cornelius, it's definitely one of the earlier type Lithium Manganese Packs you have there!
The labelling is definitely misleading, but GM have been using the "LFP" prefix in the battery codes for the last three years on all of their Lithium Manganese Rack Packs.
Alan
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The new GM LiFePO4 packs have (LT) on the label after the battery size and a green paper label that stains easily as you can see. Why paper :(
This is one of my personal 48V10AH LiFePO4 packs
(https://arhservices.co.uk/GoldenMotorCanada/LiFePO4batterylabel.jpg)
Gary
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That's the same one I have, the old style. They were duds. Nothing but grief and headaches. They stopped making them because they had so many problems. And mine started acting just like yours a short while after I purchased it.
My GM bike kit has been great and worked well for years, but those GM batteries were expensive junk. Hopefully their newer designed ones are working better for people.
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So what am I suppose to do now?
I opened up my packs so my warranty is gone but now they have a much lower chance of surviving my 45amp controller because limno2 has a even lower discharge rate then lifepo4 right?
Do I have the right to claim new packs if they really are limno2? and how do I prove they aren't lifepo4's?
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Does your receipt say you purchased lifepo4?
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yep
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Then I would demand they be replaced with the actual items you ordered. It's not the point that they are defective or that you opened them, it's that they sent you a different product than what you payed for.
Plus they are defective.......
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http://www.alibaba.com/product-gs/507403016/Headway_36V10Ah_LiMnO2_LiFePO4_lithium_battery.html
For a little more weight LiFePo4 live longer the LiMn02.
It depends on the cell, pouch cells are a bit lame on the max discharge side, where as the canister cells preform much better.
I believe it's because canisters stop the gases from bulging the cell structure and pouches puff up from the heat under high loads. I would bet running a pouch pack in a hot environment is much different to a internal resistance generated type heat at heavy load times..
Temperature performance is not cut and dry.
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I remember one man had his old GM charger AC selection switch set to 240v instead of 120v
Because his electricity grid system was set to 120v, the charger being set to 240v wasnt functioning properly to charge the battery normally..
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http://www.alibaba.com/product-gs/507403016/Headway_36V10Ah_LiMnO2_LiFePO4_lithium_battery.html
For a little more weight LiFePo4 live longer the LiMn02.
It depends on the cell, pouch cells are a bit lame on the max discharge side, where as the canister cells preform much better.
I believe it's because canisters stop the gases from bulging the cell structure and pouches puff up from the heat under high loads. I would bet running a pouch pack in a hot environment is much different to a internal resistance generated type heat at heavy load times..
Temperature performance is not cut and dry.
Well I bought a 36v/25 amp sensorless controller for the moment and if I put them in parallel they should be able to handle 25/30 amps no problem right?
If they still run dry after only a couple of miles i'm definitely going to sent them back.
The bad pack is already a replacement of a early pack that wouldn't even charge to 40v at all but the other pack I have works fine.
For my 72v controller i'm going to save some money for some headways.
Also my Magic Pie 3 has gotten a lot of play on the axle only after a few test rides but besides that it performs great.
And my charger doesn't have any switch to set the input voltage so I guess that cant be the problem.
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I have one of those 72v 40 amp controllers.
First ride at 48v 40-50 amps, my battery cells got warmish just on an average ride. I opened the infinion controller and cut one of the two 20 amp shunts, problem solved, and I have not looked back.. I lost some power, but gained a lot of life in my packs. My 15ah Lifepo4 pack is 2 years old now and I have not seen any decrease in range..
Unless you have Headway or A123 cells, cutting current via a shunt this isnt such a bad idea. You may lose a little power.
Another thing was I did built an external shunt resistor from the shunts from some old GM contollers, I designed it to snap inline to my anderson connector. So it was easily plug into the circuit, this saved me from opening my controller and pulling everything apart for a while and took some heat out of the contoller and tracks, good for testing.. The single remaining shunt I have inside my controller seems to taking the load fine.
I think the 40 amp controllers are bulit with a standard 36v pack system in mind with a 36>72v option. As they are rated at 1500 watts 36v @40 amps on a 36v pack = .9 ohms resitance. @ 72v * .9 resistance = 80 amps brother. Considering the added internal resistance on the other series battery Id peg it closer to 60 amps that you draw..
As you overvolt the currrent capacity increases though the controller over 40 amps..
Unless you test the current load through your battery and be sure, you may go through a few of the cheaper battery packs until you buy one rated for the job..
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I believe we have come to the stage where our BMS's should be capable with current limitting sofftware.
I look at a lot of BMS's and they only have shunts for current limitation. Yet they have fets to shut down for LVC.
Using PWM to limit the current flow through these LVC FETS before the shunt or with more parallel higher resistance fets, IMO would make for better efficiency than to just be using shunts alone. Lose the need for HCC, if the BMS even has this or its fast enough to shut down before failure,.. One could short a battery out and not blow the LVC output fets of the BMS and use a simple fuse for battery over current discharge protection.
A person with a 48v system can use a brushed controller and some average filter caps on the output and use the throttle of this brushed controller to controll the current, this idea can be installed into a BMS and regulated by the manufacturer or user to achieve better compatability to varying systems and add a better over current protection regime for the cells.
Manufactures could use this to limit their packs current abilitiues to spec, Not unlike the Cycle analiyst can in some controllers. Batteries are too expensive to play around with.
Absolute max current needs to be controlled and set solid at the output stage of the pack IMO, and not essentially be a part of an inclusive series resistance of the BMS shunts and controller shunts added together.
The more protection pack manufacturers have against overloading cells, the more protection they have from unwanted returns.. Users will enjoy the added protection as it wont interfere with their modification tinkering of the controllers.
Yeah take it to the limits is one thing. but who really wants to over draw current over their cells capablilty and specs?
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Ok I'm now running on a single 36v pack and its still sagging over 4v at peak draw. Is this normal for these packs with a 25amp controller? I'm getting about 25km range out of it which seems pretty normal but the lvc already trips at 37/36.5v(-4V =33/32v)?
And does anyone know what the C rating of the limno2 packs are?