olaf-lampe
10 kW
To the ones that are concerned about weight problems: Build it like biggs's pack and strengthen it with glassfibre strips or plates between the neighbored copper plates.
-Olaf
-Olaf
The LiFePO4 Headway cell 38120P TEST REPORT inside
- Thread starter Doctorbass
- Start date
natmartin
1 µW
- Joined
- Sep 13, 2008
- Messages
- 3
bquick said:
Hi all- I just registered to ask some questions about these cells, because I'm considering using them in a car sometime in the future.
I'm curious about why when one cell went bad it took the other three cells with it. I thought these cells generally fail open, not fail shorted.
Did the bad cell fail shorted, and the other three then discharged into it? Or did it fail open, and the others failed from overcurrent or overdischarge, since they weren't as strong as the other parallel groups in the pack?
Basically, do you think that a good BMS or LVC would have protected the good cells from failing? Or, if they shorted into the bad cell, would fuses between the cells have protected it?
Thanks,
Nate
- Brad[/quote]
Hi all- I just registered to ask some questions about these cells, because I'm considering using them in a car sometime in the future.
I'm curious about why when one cell went bad it took the other three cells with it. I thought these cells generally fail open, not fail shorted.
Did the bad cell fail shorted, and the other three then discharged into it? Or did it fail open, and the others failed from overcurrent or overdischarge, since they weren't as strong as the other parallel groups in the pack?
Basically, do you think that a good BMS or LVC would have protected the good cells from failing? Or, if they shorted into the bad cell, would fuses between the cells have protected it?
Thanks,
Nate[/quote]
Nate, since you asked, there is an absolute requirement for two things when considering these or any LiFePO4 Cells. The first is a good BMS (or VMS) and the second is a reliable "LVC" - Low Voltage Cutoff switch in the circuitry. The last (but not least) is a Charger that is preferrably dialed into the charge pattern for your particular Cells. With these three amigos, you can be relatively sure that you have covered all the bases, and if your Cells die, it's more than likely because one (or more) of these requirements failed to do their job. If they come as part of the battery pack - it's generally a good sign that the mfg. has had enough sense to protect his Cells by providing you with a "complete system" to start with. If they don't offer this - I would stay away especially as a beginner.
Doing without at least two of these elements is like having unprotected sex.
Best,
Don Harmon
Hi all- I just registered to ask some questions about these cells, because I'm considering using them in a car sometime in the future.
I'm curious about why when one cell went bad it took the other three cells with it. I thought these cells generally fail open, not fail shorted.
Did the bad cell fail shorted, and the other three then discharged into it? Or did it fail open, and the others failed from overcurrent or overdischarge, since they weren't as strong as the other parallel groups in the pack?
Basically, do you think that a good BMS or LVC would have protected the good cells from failing? Or, if they shorted into the bad cell, would fuses between the cells have protected it?
Thanks,
Nate[/quote]
Nate, since you asked, there is an absolute requirement for two things when considering these or any LiFePO4 Cells. The first is a good BMS (or VMS) and the second is a reliable "LVC" - Low Voltage Cutoff switch in the circuitry. The last (but not least) is a Charger that is preferrably dialed into the charge pattern for your particular Cells. With these three amigos, you can be relatively sure that you have covered all the bases, and if your Cells die, it's more than likely because one (or more) of these requirements failed to do their job. If they come as part of the battery pack - it's generally a good sign that the mfg. has had enough sense to protect his Cells by providing you with a "complete system" to start with. If they don't offer this - I would stay away especially as a beginner.
Doing without at least two of these elements is like having unprotected sex.
Best,
Don Harmon
natmartin
1 µW
- Joined
- Sep 13, 2008
- Messages
- 3
Don Harmon said:-
Nate, since you asked, there is an absolute requirement for two things when considering these or any LiFePO4 Cells. The first is a good BMS (or VMS) and the second is a reliable "LVC" - Low Voltage Cutoff switch in the circuitry. The last (but not least) is a Charger that is preferrably dialed into the charge pattern for your particular Cells. With these three amigos, you can be relatively sure that you have covered all the bases, and if your Cells die, it's more than likely because one (or more) of these requirements failed to do their job. If they come as part of the battery pack - it's generally a good sign that the mfg. has had enough sense to protect his Cells by providing you with a "complete system" to start with. If they don't offer this - I would stay away especially as a beginner.
Doing without at least two of these elements is like having unprotected sex.
Best,
Don Harmon
I completely agree with you, which is why I was curious how a single cell failing caused the other cells in parallel to fail. It seems to me that with appropriate precautions, a single cell failing wouldn't cause 3 others to fail. I wonder what battery safety equipment he was using, and if any of them failed in this situation.
From his description, I would imagine that the cells failed shorted, and he had no fuses between the cells.
I'm trying to find more about the failure mode of these cells. Hearing about one failing short surprises me, since I've heard in many cases they fail open.
I'm new to using LiFePO4 batteries, but not new to EVs, battery management, or Lithium chemistry cells.
-Nate
Yes, I think a LVC would have protected the other cells, but I don't know for sure. When I took the pack apart, of the 4 cells in parallel, two were at zero and two were reverse charged.
Before I took the pack apart, I put a non-balancing charger across the entire pack and the bad cells read 10 Volts, which tells me that they were in an open or semi open state. When I put a power supply across each bad cell, none of them would draw any current, verifying the open circuit failure.
So, one or two cells probably had low capacity which allowed me to discharge them too far.
- Brad
Before I took the pack apart, I put a non-balancing charger across the entire pack and the bad cells read 10 Volts, which tells me that they were in an open or semi open state. When I put a power supply across each bad cell, none of them would draw any current, verifying the open circuit failure.
So, one or two cells probably had low capacity which allowed me to discharge them too far.
- Brad
Hello,
I have now the results from my 38120S cells:
Headway 38120S (lot: HH06 HG20) Delivery from 19.08.2008
Unit U(V) Ri(mOhm)
1 3,335 15,000
2 3,333 13,500
3 3,333 17,200
4 3,330 20,000
5 3,335 14,000
6 3,331 19,900
7 3,335 15,200
8 3,334 13,500
9 3,335 12,800
10 3,333 19,300
11 3,327 20,700
12 3,334 19,600
13 3,335 14,600
14 3,334 15,000
15 3,334 14,200
16 3,335 17,800
17 3,331 14,700
18 3,333 14,200
19 3,334 19,000
20 3,335 18,000
21 3,331 13,400
22 3,333 13,500
23 3,335 19,300
24 3,335 13,700
25 3,334 13,200
26 3,335 13,500
27 3,333 13,600
28 3,333 20,900
29 3,336 14,200
30 3,333 15,000
31 3,334 14,400
32 3,331 18,200
33 3,335 13,800
34 3,331 14,200
35 3,333 14,200
36 3,335 15,400
37 3,333 15,000
38 3,334 14,900
39 3,334 19,000
40 3,335 14,500
41 3,336 19,200
42 3,333 17,000
43 3,333 16,700
44 3,335 14,000
45 3,333 13,500
46 3,332 13,600
47 3,335 14,200
48 3,333 14,300
49 3,333 19,000
50 3,334 13,700
51 3,336 16,000
52 3,332 16,600
53 3,333 14,200
54 3,335 19,100
55 3,335 13,300
56 3,334 19,000
57 3,334 14,700
58 3,332 15,000
59 3,333 15,000
60 3,332 16,000
61 3,335 14,500
62 3,334 17,600
63 3,333 14,000
64 3,332 19,700
65 3,336 13,900
66 3,332 18,800
67 3,334 17,500
68 3,335 19,700
69 3,335 13,200
70 3,335 14,000
71 3,335 13,500
72 3,332 20,900
73 3,330 13,700
74 3,336 18,000
75 3,335 14,200
76 3,335 15,800
77 3,333 20,800
78 3,335 16,000
79 3,335 13,200
80 3,334 16,300
81 3,333 12,400
82 3,332 15,300
83 3,334 16,000
84 3,331 20,000
85 3,333 12,800
86 3,332 19,000
87 3,333 19,500
88 3,334 18,000
89 3,334 14,700
90 3,334 14,500
91 3,333 18,500
92 3,334 17,200
93 3,332 14,500
94 3,330 14,000
95 3,332 19,500
96 3,336 13,900
97 3,335 14,000
98 3,334 14,000
99 3,335 13,500
100 3,335 14,100
Resistance measured with RIM 1000
Voltage measured with Kethley 197A microvolt DMM
I rebuild my pack grouping 4 cells with similar resistance. but the conclusion is that 36 cells are over 16 mOhm.
I have now the results from my 38120S cells:
Headway 38120S (lot: HH06 HG20) Delivery from 19.08.2008
Unit U(V) Ri(mOhm)
1 3,335 15,000
2 3,333 13,500
3 3,333 17,200
4 3,330 20,000
5 3,335 14,000
6 3,331 19,900
7 3,335 15,200
8 3,334 13,500
9 3,335 12,800
10 3,333 19,300
11 3,327 20,700
12 3,334 19,600
13 3,335 14,600
14 3,334 15,000
15 3,334 14,200
16 3,335 17,800
17 3,331 14,700
18 3,333 14,200
19 3,334 19,000
20 3,335 18,000
21 3,331 13,400
22 3,333 13,500
23 3,335 19,300
24 3,335 13,700
25 3,334 13,200
26 3,335 13,500
27 3,333 13,600
28 3,333 20,900
29 3,336 14,200
30 3,333 15,000
31 3,334 14,400
32 3,331 18,200
33 3,335 13,800
34 3,331 14,200
35 3,333 14,200
36 3,335 15,400
37 3,333 15,000
38 3,334 14,900
39 3,334 19,000
40 3,335 14,500
41 3,336 19,200
42 3,333 17,000
43 3,333 16,700
44 3,335 14,000
45 3,333 13,500
46 3,332 13,600
47 3,335 14,200
48 3,333 14,300
49 3,333 19,000
50 3,334 13,700
51 3,336 16,000
52 3,332 16,600
53 3,333 14,200
54 3,335 19,100
55 3,335 13,300
56 3,334 19,000
57 3,334 14,700
58 3,332 15,000
59 3,333 15,000
60 3,332 16,000
61 3,335 14,500
62 3,334 17,600
63 3,333 14,000
64 3,332 19,700
65 3,336 13,900
66 3,332 18,800
67 3,334 17,500
68 3,335 19,700
69 3,335 13,200
70 3,335 14,000
71 3,335 13,500
72 3,332 20,900
73 3,330 13,700
74 3,336 18,000
75 3,335 14,200
76 3,335 15,800
77 3,333 20,800
78 3,335 16,000
79 3,335 13,200
80 3,334 16,300
81 3,333 12,400
82 3,332 15,300
83 3,334 16,000
84 3,331 20,000
85 3,333 12,800
86 3,332 19,000
87 3,333 19,500
88 3,334 18,000
89 3,334 14,700
90 3,334 14,500
91 3,333 18,500
92 3,334 17,200
93 3,332 14,500
94 3,330 14,000
95 3,332 19,500
96 3,336 13,900
97 3,335 14,000
98 3,334 14,000
99 3,335 13,500
100 3,335 14,100
Resistance measured with RIM 1000
Voltage measured with Kethley 197A microvolt DMM
I rebuild my pack grouping 4 cells with similar resistance. but the conclusion is that 36 cells are over 16 mOhm.
dnmun
1 PW
the Ri number you use is the input impedance from your RIM 100 unit? your charger is telling you what it sees as resistance when it is charging the cell?
the internal resistance i have been using was calculated using the formula from justin where the voltage drop across the battery from an increased load is called the 'internal resistance'.
is it possible that the new screw top cells are damaged at the top crimp by being physically/structually rigid through the cap because of the screw whereas they were relatively flexible through the tabs, which have some flexibility, and this failure of 4 parallel cells is a structural problem associated with the way the weight of the battery is loading up the cell caps?
the internal resistance i have been using was calculated using the formula from justin where the voltage drop across the battery from an increased load is called the 'internal resistance'.
is it possible that the new screw top cells are damaged at the top crimp by being physically/structually rigid through the cap because of the screw whereas they were relatively flexible through the tabs, which have some flexibility, and this failure of 4 parallel cells is a structural problem associated with the way the weight of the battery is loading up the cell caps?
no the rim1000 unit is an measurement unit for battery with 0.1 mOhm resolution.dnmun said:
dnmun said:
yes for the first time i also use this formula, but with the rim 1000 it is much faster to get an result.
dnmun said:
no i don't think so because i fastend the screws last when the pack is in position.
biggs said:
Today my replacement cells arrive they are the blue one. i measured the resistance and the voltage U0.
Here are the results:
Cell U (01.10.2008) Ri(01.10.2008)
HH19-10467 3,337 7,800
HH19-10549 3,336 8,100
HH19-10559 3,336 8,500
HH19-10805 3,337 8,500
HH23-11768 3,337 7,800
HH19-10876 3,333 8,500
HH20-10619 3,337 7,200
HH23-11772 3,337 8,100
HH23-11913 3,335 7,900
HH23-11751 3,335 7,100
HH19-10443 3,335 8,200
HH21-11372 3,332 7,400
HH23-11557 3,337 8,100
HH19-10260 3,337 7,100
HH19-10416 3,337 7,300
HH19-10853 3,333 8,100
HH20-10923 3,337 8,900
HH19-10268 3,337 7,400
HH23-11518 3,334 8,500
HH20-10606 3,338 8,500
HH20-10663 3,336 7,600
HH20-11085 3,332 7,200
HH23-12294 3,335 8,100
HH20-11061 3,330 7,400
HH21-11400 3,332 7,900
HH19-10481 3,337 7,700
HH21-11397 3,337 7,000
HH19-10885 3,337 7,700
HH20-11129 3,337 7,400
HH20-10929 3,337 8,100
HH19-10797 3,337 9,400
HH20-10726 3,333 7,600
HH20-11096 3,337 7,800
HH20-10763 3,336 7,800
HH19-10792 3,337 8,600
HH23-12292 3,337 8,600
I mean that's not bad that's good
biggs said:biggs said:
Today my replacement cells arrive they are the blue one. i measured the resistance and the voltage U0.
Here are the results:
Cell U (01.10.2008) Ri(01.10.2008)
HH19-10467 3,337 7,800
HH19-10549 3,336 8,100
HH19-10559 3,336 8,500
HH19-10805 3,337 8,500
HH23-11768 3,337 7,800
HH19-10876 3,333 8,500
HH20-10619 3,337 7,200
HH23-11772 3,337 8,100
HH23-11913 3,335 7,900
HH23-11751 3,335 7,100
HH19-10443 3,335 8,200
HH21-11372 3,332 7,400
HH23-11557 3,337 8,100
HH19-10260 3,337 7,100
HH19-10416 3,337 7,300
HH19-10853 3,333 8,100
HH20-10923 3,337 8,900
HH19-10268 3,337 7,400
HH23-11518 3,334 8,500
HH20-10606 3,338 8,500
HH20-10663 3,336 7,600
HH20-11085 3,332 7,200
HH23-12294 3,335 8,100
HH20-11061 3,330 7,400
HH21-11400 3,332 7,900
HH19-10481 3,337 7,700
HH21-11397 3,337 7,000
HH19-10885 3,337 7,700
HH20-11129 3,337 7,400
HH20-10929 3,337 8,100
HH19-10797 3,337 9,400
HH20-10726 3,333 7,600
HH20-11096 3,337 7,800
HH20-10763 3,336 7,800
HH19-10792 3,337 8,600
HH23-12292 3,337 8,600
I mean that's not bad that's good
That seems odd. Are these "replacement cells" supposed to be much different from the original cells purchased(Were they advertised that way)? It seems that there's a marked difference in the average internal resistance and standard deviation between both groups and there's no overlap at all, with the second group having a lower average and lower standard deviation meaning greater "quality control" and consistency. I wonder if their construction differed or if these cells were "cherry picked" for replacement purposes(or perhaps the originals were "crap picked"?).
Are these both groups the 38120S cells with the same rated AH? And I take it the first group is the "Brown ones" and the second group is the "blue ones"?
olaf-lampe
10 kW
I wonder how to mix the new/improved cells with the regular ones?
7-8mOhm is way closer to the 6mOhm announced by victoria.
Time to buy some, before the price rises due to demand
Olaf
7-8mOhm is way closer to the 6mOhm announced by victoria.
Time to buy some, before the price rises due to demand
Olaf
dnmun
1 PW
i think this is the batch that is being purchased by the yahoo group buy from headway. if they have not already shipped, you may be able to join the group and get the surface freight shipping charges to toronto, where joshua will break the container open.
maybe nobody should be building anything more than 1P until there is more history. this would also allow everyone to replace any dead cells easily, which was the entire reason for using the threaded cap to begin with., and then talking headway into changing.
i still think that the structural forces on that large pack all applied through the screw ends, may be creating a continuity problem inside the cylinder, at the junction between the cap and sleeve leading to such rapid failure. that is not lifepo4 failure rate stuff, it is mechanical imo.
maybe nobody should be building anything more than 1P until there is more history. this would also allow everyone to replace any dead cells easily, which was the entire reason for using the threaded cap to begin with., and then talking headway into changing.
i still think that the structural forces on that large pack all applied through the screw ends, may be creating a continuity problem inside the cylinder, at the junction between the cap and sleeve leading to such rapid failure. that is not lifepo4 failure rate stuff, it is mechanical imo.
olaf-lampe
10 kW
Thanks for the offer to join the group buy, but I'm located in Germany, so this wouldn't help much to lower p&p costs.
I asked Victoria for a cheaper way than UPS, but she didn't respond for two weeks now.
The mechanical stress to the cell ends has to be minimized by gluing the cylinder walls together. But with a safety distance between the thin_shrink_tubed cells.
It's funny somehow that the high_Ri cells where packed in brown paper tubes, which hinders the cooling of the comparably hotter cells and the cooler low_Ri cells are now sold with a better cooling shrink tube.
-Olaf
PS: Someone interested in a european group buy?
I asked Victoria for a cheaper way than UPS, but she didn't respond for two weeks now.
The mechanical stress to the cell ends has to be minimized by gluing the cylinder walls together. But with a safety distance between the thin_shrink_tubed cells.
It's funny somehow that the high_Ri cells where packed in brown paper tubes, which hinders the cooling of the comparably hotter cells and the cooler low_Ri cells are now sold with a better cooling shrink tube.
-Olaf
PS: Someone interested in a european group buy?
dnmun
1 PW
i thought you were in europe, too bad they can't ship overland from china, what a waste of jet fuel to serve russian hegemony. but columbus would never have found this chunk of land if it had not been for ottoman domination of the silk road 700 years ago.
it just seems like so much risk to tie the cells in parallel, since one cell can take out all the others so quickly. i wonder if the cells actually are swelling and shrinking during the charge/discharge cycles, which may be creating forces on the end cap. i think it was flip who had bad cells before which would only work when he applied force on the end cap. maybe i remembered that incorrectly, but i just cannot believe these cells have such a short life cycle from the chemistry. just seems mechanical failure.
it just seems like so much risk to tie the cells in parallel, since one cell can take out all the others so quickly. i wonder if the cells actually are swelling and shrinking during the charge/discharge cycles, which may be creating forces on the end cap. i think it was flip who had bad cells before which would only work when he applied force on the end cap. maybe i remembered that incorrectly, but i just cannot believe these cells have such a short life cycle from the chemistry. just seems mechanical failure.
voicecoils
1 MW
I've just received two 36v headway packs with 36v 3A chargers each from e-mtb.com.au, they are 12 cells with BMS each.
I think that there is a good chance they are the same cells soon to be loaded on the boat for Joshua's group buy. The packs are in stiff shrink wrap but I can just see a bit of blue cell by peaking in one end of the pack. The packs are ~130mm wide along the cell length so I do not think I have screw ends, but the colour seems to indicate that they are from the most recent batch.
Hot off the charger they both read 44.0v. 24 hours later (with no use) both read 43.2v
I haven't got them running in either of my planned ebikes yet, but if anyone has some suggested tests they'd like to see preformed, I'll do what I can. I do not have access to a full set of EE tools however.
ZapPat
10 kW
Thanks for the testing info of the new cells you got, biggs! If headway can keep up the QC and supply cells like this at a good price then they are going to be a good choice IMO.
It would be great if someone could do some discharge tests on these new promissing headway cells, something like the tests done on the Ping V2 thread here:
Full pack discharge capacity test (Ping V2 battery, 48V 20Ah)
Or even better like Andy's tests here:
Single cell 1C through 7C discharge capacity test (PSI 10Ah cells)
Ciao!
It would be great if someone could do some discharge tests on these new promissing headway cells, something like the tests done on the Ping V2 thread here:
Full pack discharge capacity test (Ping V2 battery, 48V 20Ah)
Or even better like Andy's tests here:
Single cell 1C through 7C discharge capacity test (PSI 10Ah cells)
Ciao!
Kurt
10 kW
I have just ordered the same pack as Vioscoils has also from -mtb.com.au. I got the 36v 20ah size. I want to order anther pack later run two of them in the future so I have 36v 40ah or 72v 20ah.
I am hoping by using the 20 ah size mine wont be stressed to much and last a bit longer at between 1c and 2c .On a 5304 48amp controller.
will post my results as they come to hand.
I hope they are ok cells I was going to go with BMI cells but couldn't afford 20ah of them. I hope they are at least comparable to pings cells if not a little more robust its my first go at lithium.
Kurt.
I am hoping by using the 20 ah size mine wont be stressed to much and last a bit longer at between 1c and 2c .On a 5304 48amp controller.
will post my results as they come to hand.
I hope they are ok cells I was going to go with BMI cells but couldn't afford 20ah of them. I hope they are at least comparable to pings cells if not a little more robust its my first go at lithium.
Kurt.
voicecoils
1 MW
Kurt said:
Has your pack arrived yet, any pics? Let us know how they do perform. I'm curious about their voltage sag under full throttle. Do you have a cycle analyst? I've got the stand alone one, and will have a crystalite plug in one soon too. I could probably shoot one up to Bris Vegas for you to play around with at some point if you haven't got one yourself.
ZapPat
10 kW
I see you finally decided to go with headway instead of either BMI, Ping or power tool batteries.Kurt said:
If your cells are as good as the last batch we've seen here, then you'll be one very happy camper with this choice! It might be a good idea to have a way of testing each cell's capacity when they arrive though, since we are not sure yet how consistant quality control is yet with headway (although they seem to be improving).
Let us know how they turn out for you!
Kurt
10 kW
I came across the headway cells local so worked out better as the Aust $ very low at the moment so even Pings packs become very expensive by the time you get them to your door and the BMI cells forget about it.They may have a good product but not sure who there market is. Movie stars and royalty I think
I already have a stand alone CA but thanks for the offer anyhow Voicecoils. I only ordered it today but as soon as I have it I can throw it on my dual motor ebike it will only dray 25amps from it but it will give you some idea. I will post the numbers from the cycle analyst. It wil take me a little while to get the 5304 all up ans running but when i do i will post numbers for a 48amp draw.
I think my numbers will be a little different as I ordered the 24 cell 36v pack so its 20ah. i am after range more than all out power. this way I am not stressing them to much. See how I go.
kurt
I already have a stand alone CA but thanks for the offer anyhow Voicecoils. I only ordered it today but as soon as I have it I can throw it on my dual motor ebike it will only dray 25amps from it but it will give you some idea. I will post the numbers from the cycle analyst. It wil take me a little while to get the 5304 all up ans running but when i do i will post numbers for a 48amp draw.
I think my numbers will be a little different as I ordered the 24 cell 36v pack so its 20ah. i am after range more than all out power. this way I am not stressing them to much. See how I go.
kurt
Kurt
10 kW
I should have the battery next week and I wanted to ask what should I do first with the pack to make sure everything is ok?
Are you suggesting a full charge and discharge cycle on each individual cell? There is 24 of them I have a good RC charger/discharger/balancer that can do up to 6 cells or one at a time.If I was to charge/discharge each cell what kind of variation in capacity is consider ok and what should I set as the discharge cut off to.
Are you suggesting that some cells in the pack could have a lower capacity and make problems ?
Or should I just put it on the charger that comes with it and let it balance if it has that feature or what ever it wants to do and then take it for a ride and measure individual cell voltage after a good ride .
Another thing is the pack was sold to me as 36v 20ah with 24cells, are the new blue cells 10ah? or is my pack going to be 16ah? I did ask this question directly to my seller who is a reputable ebike store and they said yes 20ah.It will be interesting to see what kind of BMS is included.
Kurt.
voicecoils
1 MW
Kurt said:
I'm reasonably sure that your cells and BMS will be shrinkwraped in the same thick/stiff stuff mine came in. You won't be able to see anything of the BMS if thats the case, but you may be able to have a peek at the cell colour from one end of the pack.
My understanding with the BMS is that it balances the cells over a long period of time on the charger. So you may want to leave the pack on the charger once a week for a good 12 hours to balance up the cells.
If you were sold 36v10ah from John then that's what you'll get. If you discharge them at or close to the maximum discharge he's recommended for you then you probably won't hit 10ah on your CA. I don't know at what discharge rate they're rated for 10ah at.
I've got 12 single cell lifepo4 chargers but can't use them on these packs since i'd have to remove the shrink wrap. The 1-yr warranty is more important to me then playing around with the innards of the pack.
I hope to be playing with my batteries this weekend on my red bike. Won't be discharging over 30a from them though, to protect my motor from melting down at 72v.
Cheers!
Kurt
10 kW
I will be interested in your results. I just had a poke around on headways web page and I see now there is a 10ah cell . I think what I am getting is the same as what you have but bundled into one pack for 36v-20ah. I am not planing to use more than 18ah.With a 48amp controller so 2.4c max but I want to tame that down a little to say 30amps max.
If there is a 1 year warranty I wont be touching my pack during that time.I think if you are going to have any serious problems you will soon know in the first couple of months.
Voltage sag is about my only concern let me know how you go this weekend.
Kurt.
If there is a 1 year warranty I wont be touching my pack during that time.I think if you are going to have any serious problems you will soon know in the first couple of months.
Voltage sag is about my only concern let me know how you go this weekend.
Kurt.
voicecoils
1 MW
Yup, 1yr warranty is the deal.Kurt said:
did a very quick late evening test. 10kg of batteries on your back does make itself felt! My damn hall wire connectors (to the controller) keep coming loose, I need a proper connector!!!
Anyways, I only used 0.26Ah but here is what the CA repots:
Max Amps: 33.93 A
Min Volts: 66.6 V
Assuming max amps and min volts occurred at the same time, I hit a peak of 2.26kW. Probably the case, as I did see ~2.15kW up a steep hill.
Resting pack voltage 5min afterwards: 79.9 V (starting from 87.9 V hot off the charger)
Assuming the numbers are right, 66.6v / 24 cells = 2.775V/C at ~3.4C discharge rate.
