DIY Electric Car Forums banner

1 - 3 of 3 Posts
G

·
Guest
Joined
·
0 Posts
Discussion Starter #1
Setting up my lithium pack so it is balanced to the point where I can charge 3.5 volts and then terminate the charge. What I have found is that my charge is pretty much dead on balanced up to around 3.5 to 3.55 volts. Beyond that batteries will jump to 3.7 to 4.1 volts within 30 minutes. Up to 3.5 volts the charge takes about 5 hours. Slow and steady. So 3.5 is the start of the upper knee rise. It only takes about 30 minutes for some to jump. This is the reason we need to terminate at like 3.55 volts so no battery will jump beyond 4 volts. Since it only take 30 minutes or so for 34 batteries to jump from 3.55 to 4 volts that last bit of charging is really giving you very little.

My charge this evening started at 15 amps and I terminated at 12 amps. I did not turn down the amps at 3.55 but I could have and never have pushed a battery to 4 volts. So a good lithium charger could go into cv at 3.55 and hold that until amperage went to zero. That would just about right.

34 lithium 100 AH Hi-Power. I started the charge at a standing voltage of 3.1 after my run. Terminated when one battery hit 4 volts. Like I said earlier, up to 3.55 all 34 were pretty much dead on 3.55 maybe a few at 3.57 then 30 minutes later one peaked 4 volts. Some were close many were 3.76 or so. So the safe way is balance on the low end so most of the batteries are close to the same at the end. In the super low end you will also find varying voltage ranges.

Find the spot where they are all balanced cleanly and cut off discharge and terminate charge at those points to keep your batteries safe. BMS FREE.

For me I had no choice but to take my time and balance out a pack. Slow but well worth the knowledge I have gained.

Pete :)

I will try to exceed 25 miles at 55 mph next run and remain in my safe zone.

My pack is small so this will be a big test of range and it will be cold too. No battery heating except from discharge heating. I will be keeping my motor at as high of rpm as possible to keep my driving battery amps down.
 

·
Registered
Joined
·
35 Posts
Hello Gottdi,

which kind of Hipower Cells did you get? The older ones only offering 1C discharge rate or the newer ones at comparable discharge to Thundersky or Calb? Are they matched by the manufacturer?
Which area temperatures do you have now while starting drive, how much do they sag at 100Amps for example?
With my 2nd car conversion I plan to bottom balance, too and try out Hipower Cells as you.

Best regards

Roger
 
G

·
Guest
Joined
·
0 Posts
Discussion Starter #3
Hello Gottdi,

which kind of Hipower Cells did you get? The older ones only offering 1C discharge rate or the newer ones at comparable discharge to Thundersky or Calb? Are they matched by the manufacturer?
Which area temperatures do you have now while starting drive, how much do they sag at 100Amps for example?
With my 2nd car conversion I plan to bottom balance, too and try out Hipower Cells as you.

Best regards

Roger
The cells are the older of the Hi-Power cells. I have no idea but one would suspect that they would but it is always safe to check anyway. Our area temps are 35 to 45 degrees right now. When I start the resting voltage is around 3.3 so my starting pack voltage is 112 and at a 500 amp draw I can sag them down to the low 90's for a moment. Normally at at about 112 volts and 140 amp draw I am in the upper 90 volt range. More like 98 or so. I'd have to log my run with the computer to get exact measurements. I have not done a log for the last few drives. I did that nice long drive and was pulling 150 to 200 amps for the entire drive. Batteries did get warm but not hot. One problem I have is the crappy connectors provided by Hi-Power. They just plain suck. I will clean off the terminals and put on better connectors at some point. I plan on increasing the voltage of the pack to 144 volts and then check the amp draw at 55 to see if I am more in line with what the batteries can tolerate. The little car just does not have much room to put more but I think I can stuff enough extra to bring the pack voltage to 144 volts. It will mean no more DC DC converter but for now it will be OK.

Pete :)

I'd suggest you go with TS or CALB. I don't think the tiny savings you'd see buying the Hi-Power would justify the lesser quality. Unless they have just made a bunch of radical improvements your better bet is the better battery. I got mine used and at a decent price. For the savings they were well worth the value even though they are the older version. They do have value in vehicles that don't do super high amp draws. Like golf cart upgrades and such. Bicycles that want excellent range and maybe even motorcycles. Don't overheat the batteries. Don't over discharge them and don't overcharge them. Have good connectors on them to lessen the heat buildup from poor connections. Because that heat will migrate into the battery and cause the battery to overheat.
 
1 - 3 of 3 Posts
Top