Hi folks
I thought I'd share the results of our first two tests of cells purchased from Shenzhen Luyuan (Amy Wan).
We wanted to know three things:
The cells are 280ah, and we tested four of them.
We asked Amy for the official torque and were told 10nm.
We used the bus bars she provided, which are 19.8mm x 1.9mm = 37.62mmsq. We would have been keen to double them up but she only provided four bars so went with single. We wanted to know if the terminal was up to the task, not the bus bars. So I guess we got to test both.
Ambient temperature of the room was 21°C. We'd normally test with the cells in a temperature-controlled cabinet at 25°C but we wanted to make it easy to observe temperature.
We top-balanced the cells and then did tests of individual cells at 15A. We used decent cables fastened well to prevent too much voltage loss.
All four cells came out at between 289ah and 290ah. All exceeded capacity by about 10ah. Well pleased.
Connected the BMS and charged at 20A, within the knees the delta was very low - about 0.001v, again we're pleased with the results. Set the BMS to HV 3.65v and LV 2.5v.
Once fully charged we let the battery rest for about two hours and then connected a 2kw Giandel that had a 1.7kw heater attached. This drew about 160A for most of the test.
We used two shunts to measure amps and ah just out of curiosity to compare a non-cheap Victron smart shunt (£120-ish) vs an inexpensive Juntek shunt (£30-ish). Because we were drawing high currents there was a reasonably high voltage difference between the two shunts (12.54 closest to the battery vs 12.42 furthest from the battery at some stage), but amps were within 1% of each other and very similar to the BMS reported amps. Due to the voltage difference there was a reasonable difference in kwh.
The capacity got to 281ah before the BMS prevented further discharge. Again, happy with the results.
The test ran for about 01:49:00
Now for the terminal (and cable) temperature.
We had four temperature sensors in an ambient temperature of 21°C:
Not many people need to draw anything like 160A. In our own vehicle the most we usually draw is around 90A for our Nespresso coffee maker.
Coming next ... we'll do a low-C test which we hope will hit 290ah. We're thinking around 20A for the test.
On another note we're well pleased with our Giandel 2kw 24v inverter. It's around 88% efficient which isn't at all bad.
I thought I'd share the results of our first two tests of cells purchased from Shenzhen Luyuan (Amy Wan).
We wanted to know three things:
- What are the individual cell capacities and how evenly matched are they.
- What is the capacity for a a reasonably high-C - in our case this would be around 160A so around 0.6C
- What temperature do the terminals go to. These are the new welded-stud terminals with worryingly small surface contact area.
The cells are 280ah, and we tested four of them.
We asked Amy for the official torque and were told 10nm.
We used the bus bars she provided, which are 19.8mm x 1.9mm = 37.62mmsq. We would have been keen to double them up but she only provided four bars so went with single. We wanted to know if the terminal was up to the task, not the bus bars. So I guess we got to test both.
Ambient temperature of the room was 21°C. We'd normally test with the cells in a temperature-controlled cabinet at 25°C but we wanted to make it easy to observe temperature.
We top-balanced the cells and then did tests of individual cells at 15A. We used decent cables fastened well to prevent too much voltage loss.
All four cells came out at between 289ah and 290ah. All exceeded capacity by about 10ah. Well pleased.
Connected the BMS and charged at 20A, within the knees the delta was very low - about 0.001v, again we're pleased with the results. Set the BMS to HV 3.65v and LV 2.5v.
Once fully charged we let the battery rest for about two hours and then connected a 2kw Giandel that had a 1.7kw heater attached. This drew about 160A for most of the test.
We used two shunts to measure amps and ah just out of curiosity to compare a non-cheap Victron smart shunt (£120-ish) vs an inexpensive Juntek shunt (£30-ish). Because we were drawing high currents there was a reasonably high voltage difference between the two shunts (12.54 closest to the battery vs 12.42 furthest from the battery at some stage), but amps were within 1% of each other and very similar to the BMS reported amps. Due to the voltage difference there was a reasonable difference in kwh.
The capacity got to 281ah before the BMS prevented further discharge. Again, happy with the results.
The test ran for about 01:49:00
Now for the terminal (and cable) temperature.
We had four temperature sensors in an ambient temperature of 21°C:
- On the negative terminal. This got to a maximum of 38.1°C towards the end, it got to around 28°C quite early in the test and slowly worked it's way up.
- On the positive terminal. This got to a maximum of 38.8°C towards the end, it was always a few °C warmer than the negative terminal except towards the end when they became very similar.
- On other terminals and on the bus bars. We moved this around a bit. The temp was always a couple of degrees cooler than the main terminals. The middle of the bus bar was nearly a degree warmer than the terminals it was bolted to.
- On the positive cable, 35mm assembled by ourselves. This started out as several °C warmer than the terminals but eventually they all came to about the same temperature. We didn't officially measure the negative cable (came with the inverter) but it was definitely warmer than the positive. At it's hottest the positive cable was just under 40°C
Not many people need to draw anything like 160A. In our own vehicle the most we usually draw is around 90A for our Nespresso coffee maker.
Coming next ... we'll do a low-C test which we hope will hit 290ah. We're thinking around 20A for the test.
On another note we're well pleased with our Giandel 2kw 24v inverter. It's around 88% efficient which isn't at all bad.