[lou-ace]

Ok so I'm trying to get a handle on this lipo craze. I might start by replacing my accesory battery with lipo. If I serial connected 4 cells, 10 A*h to get a nominal 12.8 volts and used my 12 volt automotive charger, which chagres 6 amps to 14.9 volts. this would be 3.75 v. per cell what would be the problem? and if this works why couldn't i use my zivan that is used for my lead pack now which charges to 165 volts to charge 43 cells to 3.83 v. per cell?

 

[major]

Ok so I'm trying to get a handle on this lipo craze. I might start by replacing my accesory battery with lipo. If I serial connected 4 cells, 10 A*h to get a nominal 12.8 volts and used my 12 volt automotive charger, which chagres 6 amps to 14.9 volts. this would be 3.75 v. per cell what would be the problem? and if this works why couldn't i use my zivan that is used for my lead pack now which charges to 165 volts to charge 43 cells to 3.83 v. per cell?

Hey ace,

I think you should plan for 4.0 V/c on the LiPo. I've been going to just a little over that, about 4.05 V/c. I use a PbAcid 48V charger on a 14 cell LiPo pack. Seems to work, but I watch it very carefully with CellLogs monitoring each cell. And I occasionally have to play Mr. BMS and balance a few cells manually.

So for a 12V battery, it needs 3.5 LiPo cells

major

 

[DIYguy]

Hey Lou,

Just make sure you make the distinction between Li-Poly and LiFePo. I think Major is assuming you are talking Li-Poly (Lithium polymer). Are you??

Cheers,

 

[gottdi]

Ok so I'm trying to get a handle on this lipo craze. I might start by replacing my accesory battery with lipo. If I serial connected 4 cells, 10 A*h to get a nominal 12.8 volts and used my 12 volt automotive charger, which chagres 6 amps to 14.9 volts. this would be 3.75 v. per cell what would be the problem? and if this works why couldn't i use my zivan that is used for my lead pack now which charges to 165 volts to charge 43 cells to 3.83 v. per cell?

You still want a charger that will shut off at the end of charge. Most lead ones just go into float mode. I am going to be using my quickcharge select-a-charge to charge up my pack. You need to know the final voltages that the charger will charge to and then watch it like a hawk. Using a setup like this I think your risking a lot to charge up to 3.8 or 4.0. These do not have an active HV cut off for a cell that may go over the top. At this level of charge it is easy for a cell to do that and quite fast too. That is why the voltage settings are usually lower for those who do not use BMS systems. I have found that even if you do charge to like 3.8, you have that little extra you stuffed into the battery just vanish in a moment when you put a load on the car. The batteries will be quite happy with a good charge to 3.6 volts. Your not going to gain much useful energy by going into the danger zone.

I will be however getting my select-a-charge re-programmed with a lithium algorithm. It will only have one to choose from so you must let them know what your needs will be. No room for fudging a bit like I can do with my Elcon and it's 10 settings.

Pete

 

[LithiumaniacsEVRacing]

I would have to agree with Major on this one. You can charge the complete battery pack as one, BUT you MUST either watch or install balancers to each balance plug for you parallel strings. I have just been schooled for over a month on monitoring and charging Lipo batteries, caution and safety is a must!

Hey ace,

I think you should plan for 4.0 V/c on the LiPo. I've been going to just a little over that, about 4.05 V/c. I use a PbAcid 48V charger on a 14 cell LiPo pack. Seems to work, but I watch it very carefully with CellLogs monitoring each cell. And I occasionally have to play Mr. BMS and balance a few cells manually.

So for a 12V battery, it needs 3.5 LiPo cells

major

 

[LithiumaniacsEVRacing]

Another very important issue with 'some' Lipo battery packs is wire/tab size. If your wires or tabs are small, then you need to build a pack with much more packs in parallel to lessen the strain on these. My first pack is 70ah, much larger than I need, but it adds a layer of safety when your pulling the amps/volts.

 

[dtbaker]

used my 12 volt automotive charger, which chagres 6 amps to 14.9 volts. this would be 3.75 v. per cell what would be the problem? and if this works why couldn't i use my zivan that is used for my lead pack now which charges to 165 volts to charge 43 cells to 3.83 v. per cell?

lead charge curves are NOT good for Li as they most often include an 'overvoltage' phase to intentionally gas/balance floodies.... NOT where you want to go w/ Li!

many of the chargers can be re-programmed to a Li charge curve. A more conservative curve would be no more than 3.65 x number of cells in CV phase.