LifePO4 batteries for use with Midnite Classic 150?

[Sunking]

I had a 48 volt 100 AH set of them. I liked them mechanically, but performance lacked due to very high internal resistance of the cells and higher than expected capacity loss. Mechanically I liked the covers and 4-point bussbars. But for the 23% higher price than CALB's was very disappointing performance. So got rid of them and replaced them with Leaf cells.

When you get them use the busbarrs and connect them in Parallel and walk away for a day. That will mid Balance them which does not mean much except make them safe to either Top or Bottom Balance. If you use your hobby charger and decide to Top Balance, it is going to be a very slow process and you will not be able to detect when they are fully charged with a 6-amp charger with all 4 cells in parallel. At 400 AH you hold 3.6 volts until charge current Tapers to 3% of C. 3% of C on a 400 AH battery is 12 amps. See the problem? Only way to Top Balance with your Hobby Charger is one cell at a time and terminate when charge current tapers down to 3 amps. Either way will take a couple of days with 4 cells. See a problem with that?

Never heard of a RC hobby charger limited to 50 watts, especially if you are running RC heli's. Those guys use large 6S 6000 mah packs and larger. A 50 watt charger would take 3 hours to charge a 6S@6000 mah pack. Ever consider getting a Cellpro Power Lab 8? It would make short work of maintaining and Gross Balance your new cells with either top or bottom balance @ 60 amps charge or discharge current.

[dax]

Balancing lifepo4 is simple matter and if you have the right equipment it's effortless. All this babble about top and bottom balancing is ridiculous and really shows how little some know about how to use the technology properly. It also seems those in USA are years behind us, as they still don't have dedicated lifepo4 charge controllers, we've had them for years. Now we are about to launch a new one within the next 3 months, they are 60amp, charge each cell line individually and cut of charge when each cell line reaches it's upper parameter. So no need to balance.

Presently we use bulk charge lifepo4 charge controllers, which bulk charge the pack to 14v then switch off and restart charging at 13.6v. They disconnect load at 12v, so never over charger or discharge. We also use individual cell monitors for our customers, which connect a discharge circuit when one cell goes over 3.5v and that will discharge the cell at the rate of charge.

We balance our cells at 3.2v before installing and that's it. So far and with hundreds of system in place over the last 5 years, none have any pack problems, just a few wiring or board components failing and they are all within the first 3 months. Our longest commercial installation is now close to 5 years old, still provides 100% of its energy and all the other are the same. We make sure our systems are idiot proof and don't require user input, which says a lot of problems.

However there can be charging a balance differences in how you use lifepo4 packs. if you are using lifepo4 for hobby or EV, then you may have balance and charge problems, because most times you are charging when the pack is not in use. But if you have an off grid or mobile system, then it is constantly in a state of discharge and this tends to keep the pack reasonably balanced.

In my own home system, I have just have bulk chargers connected, each charge has 750w of panels. The chargers are connected in parallel to 500ah pack connected in parallel, we have found this setup works best. Too big a pack and yo have problems, plus in an off grid situation you need power always, so if one pack system has problems, you can isolate it from the other packs and still have energy, unlike a big pack which would need to be shut down to fix.

[createthis]

I ordered a GBS battery, because it was easy to order and the shipping was simple/free. I ordered a Cell-Log8s and an LVD, but not the balance modules. If I decide I need them, they're only $45 for a 4 pack. I'm looking forward to this. Should be fun.

[createthis]

I will say the one thing bottom balancing seems to have going for it (other than being cheaper), is that you aren't charging the cells to full capacity, which they don't like anyway.

[Sunking]

I don't see why the cells should be out by 30%.

That tells me you have never worked with Chi-Com batteries, or any lithium batteries for that matter. I know of no one, no company, or no standard that would even suggest wiring new batteries in series and use a balance charger to Balance them. That could take months depending on the size of the cells. That is just plain silly talk.

I take that back, I do know someone who would recommend wiring new cells in series and use a Balance Charger to do Gross Balance. Only you Karrak would recommend that. You are on a lsland of your own making. Anyone who has ever worked with lithium cells knows the first thing you do is wire all the cells in parallel. Then either Bottom Balance or Top Balance. If this poor guys wires his cell in parallel will make a 400 AH pack. Assuming 50% SOC just how long does it take to charge them with 6 amps? 200 AH / 6 amps = 33 hours. Hell of a lot better waiting days for the Balance Chargers to Top Balance in series. While he is waiting he can paint a wall, and then watch paint dry to keep him entertained.

[karrak]

How old will he be when it balances the cells?On a 100 AH battery a difference of 30 AH is reasonable expectation of 40/70% SOC.

I don't see why the cells should be out by 30%. If they are all from the same manufacturing batch they will all have been charged to the same SOC so should only be out by a couple of % at most.

If they are badly out of balance to start with you can charge them in series until they start balance charging then parallel them up and charge them at 6 amps

Simon

[createthis]

Do you understand what you just said? It was really ignorant. If you bottom balance, capacity is equal at all levels of SOC. BB is th eeonly way you can equalize capacity. Top Balance and the cell capacity is never balanced, only voltage and only at 100% SOC. At 100% SOC the pack capacity is limited by the weakest cell. If Bottom Balanced it is dang near impossible to over discharge. Over Discharge can only happen if you Top Balance.

What he said wasn't ignorant. It was accurate.

Top balance means capacities are off at the top and over charging is a risk. Bottom balancing means capacities are off at the bottom and over discharge is a risk. It's really a personal preference thing.

I feel like this thread is those two guys in Frozen arguing bark side up or bark side down.

[Sunking]

You could use something like that. If you connect up the individual 'balance' wires from each cell to the B6AC you can do the initial balance with the cells in series using the balance program.

How old will he be when it balances the cells?

is charger only has a 0.2 amps balance charge current for each amp hour out of balance requires 5 hours to correct. No BMS or hobby charger is capable of doing initial (aka gross) balance in any reasonable time frame. All BMS including hobby chargers can only perform maintenance Balance. New cell SOC level is broad of 30% range. On a 100 AH battery a difference of 30 AH is reasonable expectation of 40/70% SOC. With a 30 amp spread with 0.2 amps balance current is 30 AH / 0.2 amps = 150 hours or 6 days to balance. If using a solar source with a 4 Sun Hour day will take 36 days. His chargger like any BMS is for maintenance only. You will grow old waiting for them to do the initial or gross balance.

Sorry Simon you are full of poop.Try reading the specs if you are capable. Page 22 of the manual. Please go ahead and read it. Balance Current 200 ma/cell.

Pre Balance aka gross or initial is done by connecting all cells in Parallel, not series. Then you either Top or Bottom Balance.

Createthis read this short white paper on Initial Balance, Karrak is giving you really bad advice. The White Paper backs up what I am telling you. If that does not convince you then read this White Paper on Gross Balance and look at the first chart, locate 200 ma on the Horizontal scale at mid point, then follow it up to 30 AH. Then look at the Vertical line for time and you will see 6 days. Make sure you read the conclusions especially the first one: "Balancing compensates for the SOC of individual cells. It does not compensate for capacity imbalance". The only way to balance capacity is via Bottom Balance. Do you need proof of that to?

[Sunking]

Big problem with this approach is that if the cells are balanced at the bottom end they will not be balanced at the top end unless their capacity is the same

Do you understand what you just said? It was really ignorant. If you bottom balance, capacity is equal at all levels of SOC. BB is the only way you can equalize capacity. Top Balance and the cell capacity is never balanced, only voltage and only at 100% SOC. At 100% SOC the pack capacity is limited by the weakest cell in the pack. If Bottom Balanced it is dang near impossible to over discharge. Over Discharge can only happen if you Top Balance.

[createthis]

Yup. I use the B6AC V2 for my RC quad copters.

[karrak]

Simon, would a B6AC V2 work? It's only 50W, but capable of delivering 6A. You said C/200, which for a 100ah cell is 0.5A right?

You could use something like that. If you connect up the individual 'balance' wires from each cell to the B6AC you can do the initial balance with the cells in series using the balance program. You can easily purchase a premade wiring harness and adapt it to suit your needs. The batteries are usually shipped with a 50% charge so you would need 0.5*100*3.25*4=650Wh of power to charge the battery to full. If the B6AC will charge at 50W it will take 650/50=13 hours to charge which is not too bad.

If you are going to use a Cellog8 I would hook it up at the same time as you are doing the balance charge as a safety check. If you set the alarm point on the Cellog8 to slightly less than the voltage that the B6AC will charge to you can check to see if the alarm function has been programmed correctly and is working correctly.

Do you already own this charger?

Simon

[createthis]

Midnight and Morningstar both make excellent controllers. Their top of the line models are fully programmable, and I use one of each, on different solar PV arrays to charge NiFe batteries which have a wide voltage range.

NiFe. Nice. How do you like those? I read they have terrible efficiency, but man do they last and last. For a stationary installation, I'd have to think real hard between NiFe and LifePO4. NiFe would be tempting.

[Mike90250]

Midnight and Morningstar both make excellent controllers. Their top of the line models are fully programmable, and I use one of each, on different solar PV arrays to charge NiFe batteries which have a wide voltage range. You need to be aware of the needs of the batteries, and not use the lead acid default setpoints. You have to chose and implement your own setpoints and failsafes. And disable the temperature compensation, which will ruin your batteries from overcharging. And set up a method to prevent charging when the batteries are cold (below 33F)

[createthis]

I'm really not opposed to bottom balancing with the cell-log8's alarm wired to the midnite classic via AUX2. Seems like a nice clean redundant solution, and I'd have a convenient way to monitor cell voltage anytime I want via the cell-log8.

[createthis]

Simon, would a B6AC V2 work? It's only 50W, but capable of delivering 6A. You said C/200, which for a 100ah cell is 0.5A right?