36v Lifepo4 conversion

[inrealtime]

Hello Everyone
I have a Super Scooter Turbo Elite 800 & wanted to upgrade the batteries to lifepo4. The batteries are currently 36v 12ah. The battery pack I am looking to buy is a Lifepo4 36v 20ah. The guy selling it bought it around a year ago from ebay. Comes with a fast charger. He couldnt remember the name of the seller, but it seems like it may be the infamous Lau Chan Lifepo4's. Getting them for $225. Just wondering if this would be good for a conversion for my scooter. I am trying to get to the end of a reservoir 5 miles 1 way when I fish.

 

[DAND214]

If it's 20ah and still in balance, it will do the job. 20ah LiFe is more than twice of what you have.

Pay only with PayPal in case there is a problem.

WHY IS HE SELLING IT?

I had 2 packs from Lau. they were the best packs I got of Ebay. Tested it about a month ago 36v 20Ah and it was still at 19 after 4 years. Not a lot of cycles since I went LiPo.
I sold it middle of summer.

Dan

 

[inrealtime]

He said he used it in an ATV & doesnt use the ATV any longer. Just hope that it can get me in 12-15 mile range. Currently the scooter gets me over 1/2 way only. I tend ride against the wind & carry 250 lbs including me.
I assume I can cut off the current connectors & use them on the Lifepo?

 

[dogman dan]

If it's not a doorstop, then that size will work well for you. But bear in mind, that if he stuck that thing on a shelf for a year, the bms has very likely overdischarged one or more of the cell groups, ruining them.

Insist on a test and return period. Or have him put a wattmeter on it to prove it's capacity is still at least 18 ah. You may have a nice brick there, or a nice battery.

 

[arkmundi]

Everyone has a different tollerance for risk, and what they're willing to not pay to assume that risk. My general recommendation is to buy new LiFePO4 cells and make the battery youself. I'm doing that right now, having just purchased A123 26650 format cells. You can save a lot by making the battery yourself, and control how its made in the process. Mind you, every cell has a different longevity profile. The A123 nanaphosphate cells are VERY long lived, meaning they have upwards to 3000+ charge/discharge cycles in them. By buying new I get all those cycles and a guarantee. Buying used cells, you really don't know what you're getting, what capacity they may have left. And you won't know in advance, just over time in use. So even if this battery performs initially, how long will it continue to perform? You won't know until its dead.

 

[dnmun]

if this battery is local then you can put the battery on the charger and measure the cell voltages of each cell there at his house and if it has problems you can see them before you buy it. do you know what to look for?

 

[inrealtime]

He is local, but I was going to meet him halfway. Maybe I will have to drive to his place so I can test the battery properly. I am not sure what to look for in a used battery, so I was trying to search what to look for. I only have a fluke multimeter right now. If I can find something local I can buy to test otherwise I was planning to meet him Monday. I am in the san Francisco area so maybe a rc shop?

 

[dnmun]

measure cell voltage before it starts charging and then put it on the charger and measure again to see how rapidly the voltage climbs. if one cell has the voltage climbing much more rapidly than the others and goes to full charge 3.65V from 3.2V in no time and the others are stuck at 3.42-3.47V for a long time while that one goes up fast then you know that cell has higher internal resistance to charging, making it hard to balance.

if there are cells down around 0V then the BMS will be turned off at the output mosfets and you should see the gate voltage on the output mosfets be down under 0V.

 

[dogman dan]

I'd prefer to know where the guy lives, if it does turn out to be a doorstop.

But if you do meet him elsewhere, bring a voltmeter, and ask him to bring it fully charged. Check voltage, then ask to hook if up and run it for a half mile or so. If the voltage drops a lot, like below 52v in that short distance, it's junk.

You can get connected with simple wire nuts and some extra wire you bring. It ideally would be holding 56v when he brings it. It will drop a bit at first, then it should go quite a distance without dropping much below 54v.

 

[inrealtime]

I have not picked up the battery yet, but got him to offer a refund of half of the purchase price if it indeed measures
bad after I buy abd test it. May be a better time to buy it now.

Will these batteries if in Good condition give me that much more ride time?

 

[dogman dan]

Oh yes, if they are good. At best, you are getting 6-8 ah from your lead batteries. If perfect, you will get about 18-19 ah from that lifepo4. You could see your range triple.

But that brand of lifepo4 battery is notorious for under performing. 15 ah from a 20 ah size is not unusual. So double your range is more likely. Good luck.

Next time you have 16 bucks to spare, get a cheap wattmeter from ebay. Then you can actually know what your battery capacity is, and how much you might have left on any ride.

 

[dnmun]

it would be a good deal for the $225 even if it needed some help. there is nothing difficult about working on these batteries. there are parts around to fix them too. but if it measure voltage on the output you know the BMS is not shut off so the cells are still within the range allowed by the BMS.

 

[StudEbiker]

Do you know how many amps your scooter draws? You will be straining the LiFePo battery if your controller on the scooter is trying to pull more than 40 amps. Even at 40 amps, I would expect the battery to sag going up hill with 250 lbs. + scooter weight.

 

[inrealtime]

Guess I did too much research, the guy sold the battery before I picked it up. He says he know has a 36v 40ah to sell for 350 or 300 worth no charger.

 

[dogman dan]

I'd recommend a new pack, rather than another old one.

Look for sunthing on Ebay, as one lower priced seller of pouch cell packs. Or, if you like a good risk, read up on RC batteries.