[JRP3]

From CALB themselves, charge cutoff at 3.6V
http://www.calibpower.com/ProductDetails.aspx?p=2&id=3
Those of us who have been using the cells for a while can attest to the fact that there is almost no extra capacity going above 3.5V.

[HPEVS]

Originally Posted by tomofreno

I use the minibms so cells shunt at 3.5V. Within 20 minutes the pack relaxes to less than 124V, and within a couple hours they are less than 123V. Just driving 2/10 mile and stopping they are down around 120V. I drive down about 1/2 mile long hill after that and if I keep regen currents 25 to 50A the pack V remains below 123V. Always amazes me I can run that much current into them right after full charge and less than 2Ah used and they don't go higher in voltage.

Were the high voltage warnings you've had due to regen currents? If so, do you know their magnitude? I'm using the regen limiting map to limit max regen to about 140A. That is about what I get if I remove my foot from the accelerator when traveling at 50+ mph for a quick stop - don't want to over-volt my cells if I have to emergency stop not long after full charge. Also have the user_overvoltage parameter set to 130% or 124.8V. I have exceeded it a couple times, regen cuts out, and the car accelerates down the hill.

Yes, 3.6 is the max voltage CALB recommends.

How things have changed. Early days of Thundersky Li Fe cells the recommended voltage was 4.25 V. We never went over 3.8. Over the next month or so, I'm going to collect some real world data and see the capacity difference between 3.5 vpc and 3.7 vpc. I know when charging the cells stay in the 3.4 to 3.5 vpc area for a long time. If they are actually fully charged at 3.5, then the amount of energy to recharge will drop significantly than going all the way to 3.7.

Answer to your question Tom: It has occasional over voltage trips right after charging when in regen. Who knows, we may find we can go 48 cells without issue, stay tuned.

Brian

[Ivansgarage]

Hi Brian

Could you tell me what would be the max voltage (batts)
I can use on a 1238-6501 controller. Will be using lif batts

Thanks Ivan oh fix your tag line link for hpev

[HPEVS]

Originally Posted by Ivansgarage

Hi Brian

Could you tell me what would be the max voltage (batts)
I can use on a 1238-6501 controller. Will be using lif batts

Thanks Ivan oh fix your tag line link for hpev

Hi Ivan,

The 6501 is rated at 84 volts nominal, I have pushed it to 96 (30 cells) with lithium. The max voltage is 105 volts.

We are looking in to the link now, can't figure out why it is being routed through DIY. I have sent DIY an email, haven't heard back yet.

Thanks,
Brian

[frodus]

edit your sig in "User CP" above, go to "Edit signature", highlight the "www.hpevs.com" and click on the "break link" icon, then click on the "link" Icon and retype the URL.

Hope that helps

[HPEVS]

Originally Posted by frodus

edit your sig in "User CP" above, go to "Edit signature", highlight the "www.hpevs.com" and click on the "break link" icon, then click on the "link" Icon and retype the URL.

Hope that helps

Thanks Travis, I think that worked. If you don't mind, please test it on your end to make sure.

[HPEVS]

Originally Posted by tomofreno

Hope 48 looks ok. The CALB spec has always been different than Thundersky. It was 3.6V three years ago when JRP3 and I bought our cells from them when they were called SkyEnergy.

The charge curve below was taken on one cell when charging the pack at 25A. Charging current started tapering off toward the end of charge, but lets be generous and say it remained at 25A the entire time. Then between 3.450 and 3.701V the cell received 25*(3100-2652)/3600 = 3.1 Ah. Probably more like 2.5 Ah considering the current dropping off.
Attachment 13359

Wow, that is way different than the Voltronix (Thundersky) I have in the Porsche. I'm updating the BMS this week with new software. I'm going to set it up at 3.5 volts max and see if the over voltage trip goes away.

Thanks for the info,
Brian

[frodus]

Originally Posted by HPEVS

Thanks Travis, I think that worked. If you don't mind, please test it on your end to make sure.

Yup, works fine!

[JRP3]

Originally Posted by HPEVS

How things have changed. Early days of Thundersky Li Fe cells the recommended voltage was 4.25 V.

That was actually too high really, and I think the reason a lot of people killed some cells prematurely. I think it resulted from poor translations of Chinese instructions which probably said not to go over 4.25V, which people took to mean charge to 4.25V.

[tomofreno]

Originally Posted by HPEVS

How things have changed. Early days of Thundersky Li Fe cells the recommended voltage was 4.25 V. We never went over 3.8. Over the next month or so, I'm going to collect some real world data and see the capacity difference between 3.5 vpc and 3.7 vpc. I know when charging the cells stay in the 3.4 to 3.5 vpc area for a long time. If they are actually fully charged at 3.5, then the amount of energy to recharge will drop significantly than going all the way to 3.7.

Answer to your question Tom: It has occasional over voltage trips right after charging when in regen. Who knows, we may find we can go 48 cells without issue, stay tuned.

Brian

I deleted the post on this charge curve because there seems to be an error in the time axis when imported from LogView into Excel. The values seemed to be about what I had seen in other tests so I didn't catch it right away. I'll see if I can figure it out...

Edit: collected new data and reported it here: http://www.diyelectriccar.com/forums...1&postcount=62