Best place to buy individual replacement lifepo4?

[fuz]

Got a cell that is apparently weak (either that or discharging through my BMS). Anybody got any recommendations for where to get a single 20ah prismatic (rectangular box) cell?

 

[vanilla ice]

Electricrider has some cheap yesa's, but I don't know if they prismatic.

 

[dumbass]

Got a cell that is apparently weak (either that or discharging through my BMS). Anybody got any recommendations for where to get a single 20ah prismatic (rectangular box) cell?

I have always found 20ah prismatic batteriers had to come by. But if you could use a 4 pack for $128 plus shipping this is where I have been buying my Thunder Sky packs.

http://elitepowersolutions.com/products/product_info.php?cPath=16&products_id=74

 

[fuz]

Ahh, wow, no can't REALLY use a 4 pack, but I sure as heck would buy the pack just to tear apart and use one inside for that price. Any idea of the cells measurements inside?

 

[dumbass]

Ahh, wow, no can't REALLY use a 4 pack, but I sure as heck would buy the pack just to tear apart and use one inside for that price. Any idea of the cells measurements inside?

Funny you should ask.......no I don't but if you are really interested in them I guess I could pull my pack apart tomorrow and messure them for ya.

 

[Russell]

How about this one;

http://www.batteryspace.com/lifepo4prismaticmodule32v20ah3crate64whceunapproved.aspx


-R

 

[fuz]

Russell,

Thanks, that is what I was looking for. Had found another that looked just like that (forget where now) but the spec sheet said lifepo4 with a max working voltage of 4.25V. Maybe a translation error on the battery type or voltage, either way I kept looking.

Dumbass, don't want to put you out, but if it really isn't too much problem could you post a pic of the inside cells and what you find out? They probably are the correct physical size, but wanted to make sure they have some type of screw/bolt connector and not tabs. If they do then I will go with the four pack at that price, if not I will order the single that Russell found.

Vanilla,
I checked everywhere I could on their website, but all I could find is that they aren't selling lifepo4 anymore due to quality problems.

Thanks guys!

 

[vanilla ice]

They are 20ah and in the yardsale section but they are 1c iirc. I don't know what shape.

 

[amberwolf]

What about EVComponents?
http://www.evcomponents.com/ProductDetails.asp?ProductCode=TS%2DLFP40AHA
40Ah for $48.40 (including their 10% duty/shipping costs, not including shipping to you, I think). Operating voltage lists up to 4.2V but Dave at EVC said 3.8 max is nominal for best life. Under load, like most others, they'd be around 3.2 nominal for most of the discharge curve.

Seems a better deal than the 20Ah for the same price at the other link.

(EVC said TS doesn't make anything less than 40Ah nowadays, in this type of cell)

 

[dumbass]

Russell,

Thanks, that is what I was looking for. Had found another that looked just like that (forget where now) but the spec sheet said lifepo4 with a max working voltage of 4.25V. Maybe a translation error on the battery type or voltage, either way I kept looking.

Dumbass, don't want to put you out, but if it really isn't too much problem could you post a pic of the inside cells and what you find out? They probably are the correct physical size, but wanted to make sure they have some type of screw/bolt connector and not tabs. If they do then I will go with the four pack at that price, if not I will order the single that Russell found.

Vanilla,
I checked everywhere I could on their website, but all I could find is that they aren't selling lifepo4 anymore due to quality problems.

Thanks guys!

OK, got the info for ya but sorry I can't post a pic right now but I will try to over the weekend if that helps. The individual cells are 1.650" thick x 2.815" wide x 5.781 high but that does n ot include the top mounting ring that is threaded (as you were hoping for) the ring and bolt with a wire end eyelet is an additional .400" for a total height (installed) of 6.181". Remember these cells are rated at 3c constant with I think a 10c burst. They are yellow in color just like all Thunder Sky cells. I think the wire mounting screw is a 5mm thread. Let me know if you want pics. And FYI the case they come in is not sealed. It is only a pop together case that you can pry open. The hard part is getting the cells out because some of them are shimmed in really tight. I made a case for my Ezip for these cells and they fit perfectly in the original rack on the Ezil bike.

 

[fuz]

Appreciate everybody's help. Here is where I am at the moment. I still may have a bad cell but doesn't seem to have anything to do with my original problem. I have had BMS cutout problems with my cells around 12AH discharge since I have built the bike. I have installed BM6s on my cells which are split into two packs in rear panniers. I had found one cell that would droop voltage fairly seriously at around half discharge, but would bounce back within seconds of releasing the throttle. After posting here, I did a full charge and monitored their self-discharge voltages over the next 72 hours. I noticed my weak cell died down to 3.2V faster than the rest of my pack, but for the first time noticed that the cell next to it pretty much stayed at charge voltage. Then it occurred to me that if I added the extra voltage from one strong cell to my weak one, it would be completely normal. Hmmm. To make a long story short I tore apart that side of my battery pack, found completely balanced cells, and then realized that I must have always had one sense wire bad. The BM6s were reading off of the BMS which apparently can have a somewhat linear voltage across disconnected sense wire inputs (well only know one for sure). So with a missing sense wire, it still would function somewhat (actually to about 12ah on the pack). Fixed the wire and voltages were dead on. Took out for a ride back and forth to school. At about 30 miles got my dreaded beeping from my BM6s. Crap. Did I screw up another sense wire? Hopped off to take a look at the voltages, but this time much different. Whereas before the voltage would bounce back no load with a bad sense wire, one of the cells in the other side was at around 2.3V no load (about .8 less than others). It charges up fully and holds the voltage nicely (and never noticed any problem with it before), and am pretty sure I have had the pack at this level of discharge before so I need to take another hard reading on the terminals. Least I know where to get another cell now!

 

[fuz]

Yep, bad cell. Hits cutoff after 12.3AH (even at around .5C). Tore apart pack and verified on terminals. Dumbass..could you still post those pics? They would still add to the thickness of my pack but would be a few mm thinner than the 40AH and I think I could work with them.

 

[dumbass]

Yep, bad cell. Hits cutoff after 12.3AH (even at around .5C). Tore apart pack and verified on terminals. Dumbass..could you still post those pics? They would still add to the thickness of my pack but would be a few mm thinner than the 40AH and I think I could work with them.

Here's all the pics of my pack and of the cells.