BMI cells

[mcstar]

It sounds like the VMS could allow the cell voltage to go higher than the safe limit.
I never understood systems that took the cells over their desired charging voltage then used the shunt to bleed them back down to the proper level.

Fetcher's correct. There is nothing in the VMS of the Lifebatt that will prevent an over volt condition automatically. It has the alarm, but no Mosfet's for removing the charge current. That's why I wired a ping bms into my pack to use its cut out. That's what allows the balancer to have enough "off" time to properly balance the pack.

 

[Battboy]

It sounds like the VMS could allow the cell voltage to go higher than the safe limit.
I never understood systems that took the cells over their desired charging voltage then used the shunt to bleed them back down to the proper level.

Fetcher's correct. There is nothing in the VMS of the Lifebatt that will prevent an over volt condition automatically. It has the alarm, but no Mosfet's for removing the charge current. That's why I wired a ping bms into my pack to use its cut out. That's what allows the balancer to have enough "off" time to properly balance the pack.

That is why LiFeBATT recommends using only a LiFeBATT approved charger like the ones from Soneil or Zivan because these chargers are now programmed with the LiFeBATT charging algorithym which will not let the charger over-volt the packs. These chargers will cut-off automatically. The VMS will trigger an OV buzzer but you need to manually disconnect any other charger.

Don Harmon

 

[mcstar]

I'm not sure which charger microcar is using. mc??

 

[fechter]

That is why LiFeBATT recommends using only a LiFeBATT approved charger like the ones from Soneil or Zivan because these chargers are now programmed with the LiFeBATT charging algorithym which will not let the charger over-volt the packs. These chargers will cut-off automatically. The VMS will trigger an OV buzzer but you need to manually disconnect any other charger.

Don Harmon

Even with the right charging profile, if one cell gets out of balance and goes low (this can happen to abused cells), then the other cells would be too high. If you get more than one low cell, the voltage on the other cells could exceed the allowable range. Even with healthy matched cells, as they approach end of charge, there could be a wide variation in cell voltages as the charger is tapering. This would even out when all the cells stop taking charge.

 

[miro13car]

Don,
the problem is that LifeBatt charger is out of synch with OHV light/signal.
OHV light and buzzer comes on at least 7-8 minutes before green light shows on charger/end of charge/.
I noticed on newer LB charger voltage was lower from 44V to 43.8V.
And it was my question to mcstar which should I obey: OHV or charger.
It is dillema, now I allow 1-2 minute after OHV buzzer and I pull plug on charger.
SO yes charger cuts off but NOT before buzzer sounds for more than 5 minutes and resistors got very hot.
What do you recommend?
MC

 

[Battboy]

Don,
the problem is that LifeBatt charger is out of synch with OHV light/signal.
OHV light and buzzer comes on at least 7-8 minutes before green light shows on charger/end of charge/.
I noticed on newer LB charger voltage was lower from 44V to 43.8V.
And it was my question to mcstar which should I obey: OHV or charger.
It is dillema, now I allow 1-2 minute after OHV buzzer and I pull plug on charger.
SO yes charger cuts off but NOT before buzzer sounds for more than 5 minutes and resistors got very hot.
What do you recommend?
MC

Miro, the LiFeBATT charger will not over-volt the pack. It is designed to drop down to a milli - ohm trickle charge once the OHV Light/signal sounds. That 7-8 minutes assures the pack is balanced and that all cells reach a full charge. It works the way it was designed to work. I am sorry the documentation was not up to par when you received your pack. But that is all corrected now. Resistors will get warm but if the case itself dosen't feel HOT then it should be fine. If you have taken the pack apart and are actually "touching" the resistors - then you probably are feeling them as "hot".

Thanks for your input.

Don Harmon

 

[dimitrib90]

http://cgi.ebay.com/LIFEPO4-10AH-Cell-3-2v-Nominal-5C-continuous-10C-Burst_W0QQitemZ270303126584QQihZ017QQcategoryZ11332QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Anyone know what kind of cell this is?

 

[Battboy]

http://cgi.ebay.com/LIFEPO4-10AH-Cell-3-2v-Nominal-5C-continuous-10C-Burst_W0QQitemZ270303126584QQihZ017QQcategoryZ11332QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Anyone know what kind of cell this is?

That is the new Headway Cell with screw posts.

Don Harmon

 

[oofnik]

Yeah, I saw those too. Emailed the seller to confirm that they are the new Headway 38120S cells.
If any of you E-S members pick some up, please post results!

 

[dimitrib90]

Are there any specs on these cells?

 

[oofnik]

No published specs from Headway as far as I know. But ES member biggs did a test on these cells with a RIM1000, a battery internal resistance meter, and got some very nice numbers. You can find his results here. His batch measures between 7.1 and 9.4 mOhm. And I believe they are rated 10Ah.

 

[dimitrib90]

I purchased a couple of the new headway cells and guess what? Im sending them to Doctorbass to test!! High five!! :lol:

 

[oofnik]

Awesome! Can't wait for the results
Thanks a lot!

 

[c-hesscom]

I have the specs from Headway, but do not know how to post them yet

 

[dimitrib90]

This is in excel format. Im not sure if these are the 38120P or 38120S, I think they are P.

 

[dimitrib90]

This is in excel format. Im not sure if these are the 38120P or 38120S, I think they are P.

I think these are 8ah 38120P cells because they never go over 8.5ah if you check the graph. Also it says at the top 38120P (8ah).

 

[Battboy]

This is in excel format. Im not sure if these are the 38120P or 38120S, I think they are P.

Says 8Ah on the Specs.

Don