Replacement LiPo4 charger with built in BMS

[mvadventure]

OK, here's the deal. I'm confused AGAIN. Zane of Aten Energy sent me a replacement charger for my 48V 20 AH pack as the BMS built into the battery died. The new charger is three times the size of the old one and LOTS of lights and a big fan. It also has lots of wires. LOTS of wires.

On my batteries and in the pics I've seen of others the terminals on the cells are hollow threaded aluminum. They have a nut over the outside that takes a 17MM wrench and a straight screw down the middle for fastening wires. When my batteries were new and the BMS installed the installer must have been related to King Kong as the screws were in REALLY tight. So tight they when I attempted to unscrew them (32 of them) most of them broke. This left me with a threaded post with the aforementioned 17 mm nut on them. This would have been fine had the new BMS which is built into the charger had connectors that would fit over those said threaded posts that were in reality about 1/2" in diameter. Naturally they had connectors designed to fit with the much smaller screws which were not broken and lying on my bench.

Since I wasn't really thinking ahead and since the hardware store where they sell washers is about 5.6 miles away and I had already broken all the screws and removed all the nuts from all the terminals and had merely a pile of broken screws and aluminum nuts and a LOT of wires with connectors that didn't fit anything and now the bike wouldn't run unless I pedaled it and that wasn't going to happen.

So, I put the nuts on lightly and squeezed the new connectors under the nuts and then tightened them for a friction fit I got everything working. It took awhile but my shop was cool, the stereo had an old Traffic CD playing and except for a nap I didn't have anything else to do. When I turned the key on the watts up meter showed 54 volts which is about normal and since I had been charging without a BMS for about a month I didn't bother checking each cell.

Then the real test. I plugged the new charger in. It lit up like a Christmas tree. There is a run light, a charge light and 16 red LED lights that are individually numbered to each cell. All but two of the lights, 7 & 9 came on for a few seconds and then all went out, the red charge light turned green and the fan quit. All good I figured. I must have done something right.

Then a test run of about 3 miles at 25 - 30 MPH to pull the batteries down. The new charger has an 8 AMP charge rate so I figured it wouldn't take long to bring the battery back and it didn't. After just a few minutes of simply a charge light and an on light the red LED's started coming on and going out. I figured the light indicated almost ready and out meant done. After all the lights went out the charge light which had turned orange when the LED's started coming on turned green.

Then I tested each cell. I went from most at 3.56 volts to a couple at 3.4 and one at 3.6 with a little variance between 3.54 and 3.56. Since Zane didn't answer his cell phone and no instructions came with this new charger and since it had been charging for about a month without a BMS, does anyone know if the cells will stabilize after a few charges/discharges?

The charger is a BCO Lithium Charger, model BCO 4808B and another number that was H20716510G and I couldn't find anything on it using google. Any feedback, pro or con, would be appreciated.

Mike, Crystalyte 5304 with Crystalyte 4840 controller and the LIPO batteries. It now has 2,300 miles on the 5304 and going strong.

 

[fechter]

I'd like to see a pic of that charger. It sounds like a bunch of individual cell chargers, which should work fine for charging. What about discharging? Is there no BMS to protect the cells from overdischarge now?

 

[mvadventure]

I don't know. I'll send a pic of the charger and the way I have it wired this evening. I was not happy with merely squeezing the BMS connectors between the terminals using the nuts as fastening devices in a way not intended. It was very possible a little vibration would knock one loose which would not only DC all the connections it could cause a serious short with potential for ruination. So, this AM I stripped a bunch of 14 gauge copper wire and utilized that connecting the bms that way and soldering the connections.

Midway through this procedure, which took awhile, I figured that had I left the damned battery alone to start with and merely soldered the BMS wires to the heavy duty connectors that were on there I would have been better off. Too late though as the screws were already broken making the copper connectors useless.

I did plug the charger in this AM prior to starting this project and all the red lights came on for a few seconds and I did it again after doing all the wiring. This time one cell read 3.30, one 3.60 and the rest mostly around 3.56 with a couple in the 3.40 range. Maybe they will balance out, I hope so.

Mike

 

[mvadventure]

To better answer the question re cell discharge, the answer has become an obvious no. The charger is the BMS and the old BMS has been removed. Therefore the only BMS is during charging.

Pics are of the charger w/LED's, the charger connector and the new wiring. You can see the tops of the broken screws on most of the terminals. Hopefully after todays' ride it will start balancing the individual cells. Even though the wire is only stranded 14 gauge I'm not suffering any apparent performance failure. It was cold and windy this afternoon and I made most of the three mile ride home at >30MPH.

Pretty it ain't.

Mike

 

[GGoodrum]

I agree with Richard. I'm guessing this is a bunch of 8A individual cell chargers, which is great. This is by far the best and quickest way to fully charge each cell. Do you have any contact info for Zane? I'd like to contact him about this charger.

You might want to consider adding an LVC board to this setup, in order to make sure you don't over-discharge the cells. It is pretty easy to do, as you won't get much notice at the end of the duration, before the cell voltages start dropping quick. Anyway, the LVC wireswould simply go in parallel with your existing new charger wies, and then in series with the negative power lead, to provide active cutoff.

What happens is, when a cell drops down to 2.1V, under load, it cuts power. This removes the load, so about a half-second later, power returns. If the load is still there, it will cut off again. If you back off the throttle a bit, you can probably get another 1-2 miles before even a little throttle starts causing the cutouts. What I've found with my LiFeBatt and a123-based packs is that when the first cutout hits, there's about 10% capacity left in the pack. This is plenty of reserve, as near as I can tell. I do this daily, with my a123 packs, and many of them have well over 1000 cycles on them. I'm up to about 200 cycles on my LiFeBatt packs, which I also regularly run down to cutoff, and they are still as strong as ever as well.

Anyway, PM me if you are interested in an LVC board, and I'll get you hooked up.

-- Gary