Taking the LiFePO4 plunge

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ChrisB
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Re: Taking the LiFePO4 plunge

Postby ChrisB » Fri Sep 11, 2009 6:41 pm

phil shepherdson wrote:
ChrisB wrote:Well after much thought and investigation I'm going to go modern :shock:


Thanks for sharing your experiences ChrisB. I was interested to see what Ping batteries look like and how professional they are, knowing some Chinese stuff is low on quality. I have a Li 10amp/hr battery on my e bike kit and it only drops down a bit after 15-20 mile stint or two. However i do cheat by peddling to keep the speed up (av 17 -20 mph and this i swear seems to charge the battery up because the battery meter seems to move up a notch or two after that!

Phil'TNorth


So far very pleased with the Ping battery, yes its not pretty and really is just shrink wrapped cells with a BMS sellotaped to the top :lol: but for the money it seems to very good, the charger lead comes with a cannon plug on it and so does the charger and thus it is plug and play, its just down to you to stick what ever you like on the output.

Is your 10ah Li a ping unit ?

ChrisB
I reject reality and substitute my own !!!!!!

phil shepherdson
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Re: Taking the LiFePO4 plunge

Postby phil shepherdson » Mon Sep 14, 2009 8:35 am

Is your 10ah Li a ping unit ?

No it isnt. it came with the Alien Bike kit and is cased in an aluminium suitcase styled unit and is 36V 10Ahr. So far i have done about 70 mile on it in 10 mile stints. i would like to test how far it will go on a complete charge. the ultimate idea i have however is to find a way of taking the electric hub idea and incorporating it in my Midas car so as to create a hybrid. this might be an easier and simple way of going electric!

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ChrisB
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Postby ChrisB » Sat Sep 19, 2009 3:29 pm

Interestingly today I've used the pack quite hard and I noticed that one cell has taken considerabley longer to light the little red LED than the others :?

So should I leave it connected to the charger a bit longer do you think.

I'm at a bit of a loss as to what the little LED's actually signify, is it that its saying the cell is full charged or is it saying the BMS is now shunting the charge current away from the cell and thus signifing that the cell is fully charged and leaving it connected further isnt actually doing anything or what ??

Should I take it off charge once the last LED lights or should I leave it on for a further length of time to insure they are all fully charged

Might have to give Ping a shout if no one can shed a bit more light on these little LED's and what they actually mean.

ChrisB

PS still havent actually managed to flatten the pack to the point of it cutting out yet :lol:
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jonathan jewkes
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Postby jonathan jewkes » Sun Sep 20, 2009 8:39 pm

I am seriously considering getting some Ping batteries for my EV (yes, I would need quite a few of them). But I need some more info about the BMS supplied by Ping - in particular about the over-discharge protection.
Does it reduce the current to keep the voltage above at a minimum acceptable level? Or does it cut the current completely to zero as soon as the voltage drops below the cut -off level? (If so, how do you restart it?) Or does it just send a signal to your motor controller to reduce power a bit?
Jonathan Jewkes
Daily EV user for 10years - an enthusiast and also a realist

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ChrisB
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Postby ChrisB » Sun Sep 20, 2009 10:48 pm

I'm no expert on the PING BMS, your best bet is to drop Ping an e-mail, he's really good at answering questions.

The BMS I think just shuts down the output, and wont restart until the voltage is back where it belongs but I could be wrong, certianly theres no output to the controller from the BMS unit, theres only a set of charge wires and a set of output wires.

ChrisB
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arsharpe
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Postby arsharpe » Mon Sep 21, 2009 6:20 am

ChrisB wrote:I'm at a bit of a loss as to what the little LED's actually signify, is it that its saying the cell is full charged or is it saying the BMS is now shunting the charge current away from the cell and thus signifing that the cell is fully charged and leaving it connected further isnt actually doing anything or what ??

Should I take it off charge once the last LED lights or should I leave it on for a further length of time to insure they are all fully charged

Isn't this the same thing. i.e. it is fully AND it is shunting current, i.e. shunting current starts when fully charged. There may be a partial shunt in which case it may be worth leaving on a little more. Is it possible to measure the voltage on individual cells to see when the LED comes on and if the voltage rises anymore after the LED comes on ?

ChrisB wrote:Might have to give Ping a shout if no one can shed a bit more light on these little LED's and what they actually mean.

Probably the safest thing to do.

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Postby GregsGarage » Mon Sep 21, 2009 3:14 pm

jonathan jewkes wrote:I am seriously considering getting some Ping batteries for my EV (yes, I would need quite a few of them). But I need some more info about the BMS supplied by Ping - in particular about the over-discharge protection.
Does it reduce the current to keep the voltage above at a minimum acceptable level? Or does it cut the current completely to zero as soon as the voltage drops below the cut -off level? (If so, how do you restart it?) Or does it just send a signal to your motor controller to reduce power a bit?


Hi Jonathan,

My Ping pack is older, and doesn't have the leds that the latest packs do. I purchased it mainly to find out if they could be used just as you are describing. My conclusion is that they couldn't, at least not without some modifications. My Ping pack works by simply switching off either the load or charger if any cell goes too high or low. All the current traveling through the pack also goes through the BMS, they are connected in series. The problem that you could encounter in trying to connect packs in series is that the electronics need to be rated for the total pack voltage, which they are not if you connect in series. The problem you encounter connecting in parallel is that if one pack switches off then all the current flows through the remaining packs, possibly overloading them. So it is not a simply job of directly connecting packs together. Also the fact that they switch off without warning is acceptable on a bicycle, you can always pedal, but could be dangerous in a car. Of course that all may have changed with the newer packs, have a look on the endless sphere forums, I recall there was a lot of discussion about connecting ping packs together. Sorry I don't have a link, Google should be able to help you there.
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191


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