Using RC quad charger to charge one 16S Lifepo pack

Hello to all,

This is my first post to this forum although I have been long term reader and your advices was very helpful for me many times.

I am planning my new ebike build and I would like to assemble my own battery pack consisting of 16 20Ah LiFePo4 cells. In order of make sure cells will be balanced during every charge I would like to use RC charger with balancer. Problem is that non of those chargers are capable of charging 16 cells at once (normally 6 - 8 cells). But I found charger (Equilibrium quad) which has 4 separate charging channels and each of them is capable of charging 6 lithium cells. So my thought is to use all 4 channels (4x4 cells) to charge my battery pack (image of connection included). But I am not sure if this is even possible. Will this connection cause shortcut the battery or not? For clarity I left out service wires for balancer in attached image.

Many thanks in advance for any ideas

As long as each charger port is completely isolated it will work fine. So the question is, are they? I think I recall the one from HK not being isolated.

Dr Bass wrote an interesting article on that 4 port charger. It is definilely not isolated and he had to do a good deal of work inside it plus use a separate D/C converter for each port to get it to charge a 16S battery. IIRC it was still fairly slow. Check for his thread on it.
otherDoc

I'm actually in the process of doing the same thing but with 23 cells. The whole goal behind this is to not have to unplug each battery off the harness every time we have to charge.

1. You will need to have a on/off switch between the controller and the batteries so you can open the circuit before charging.

2. Each charger must be isolated, that means if you buy 1 charger that has 4 ports, you must take it apart and cut the grounds and re-wire so that each charger inside can be run off seperate power. Or you can use 4 seperate chargers to start with. You also will have to have 4 different power supplies. These power supplies cannot be grounded. They must be 2 pin, Nema 1-15P (Neutral & Live)(USA). Not sure what Europe is. I've only found laptop or enclosed AC adapters that are like that now days. I will be using the Turnigy 400W 4 port.

Here are some links to more information:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=44278
Watch both of these videos from dr. bass:
http://www.youtube.com/watch?v=rYuAcivabZ8
http://www.youtube.com/watch?v=aqLwCllxIqI

I am going off of the research and information I have found. I won't be doing all this for a week or two. Hopefully everything will work and I won't blow something up! haha!

bulk charge only. use matched cells/packs from HK . use r/c balance chargers only once a year or so! I also use cell monitoring usually once a week with a cellog array . amazing success with that! thousands of cycles with a dozen larger packs and very little concern about staying in balance. I know lifepo4 may be somewhat different, but you could take advantage of self balancing effect of end of charge efficiency drop off to self balance cells........

But I also like what doc did, and ideally u would use a military connector from ebay
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bulk charge meanwells for the win

Or bulk charge using 2 8 port battery medics to balance while charging. I think that's the easiest solution.

Just bear in mind, that a typical quad charger is only 50w per channel, so think in terms of hours per charge if it's 16s 10 ah. Most of us set up charging systems that are much faster than 200w total.

Assuming you have 4s packs, why couldn't you charge with two 300w 8s chargers. Or is two plugs more than you could possibly bear? What you plan is 4 plugs anyway.

Me, I just don't get it. How is 4 chargers in one box less work than 4 chargers, or one charger and a paraboard? All of it is still unplugging 4 plugs. What's the saving in effort?

Read about Icecube 57's paralell series switching harnesses before you leap into purchases. Two harnesses, one for each 8s section and it's charger. Very simple once set up. You don't need to balance every cycle at all.

Thank you very much to all for your advices.

I can see that this way of charging woun't be ideal. In any case I don't mind to plug and unplug four harnesses, or two. Reason why I wanted to use quad charger is that I would have only one box instead of two separate charges (each for 8 cells).

Of course best option for me would be to have only one charger with one plug to whole battery pack. The way with two battery medics connected to each 8 cell group during charging would be great, but problem is that I couldn't find any battery medic (or any other balancer) for 8 cells (normally they are for 6 cells):-(((

Thanks again for your patient with me

Bear in mind, that you can paralell packs, and charge and balance them all at once. You should be able to easily ride all week without balancing. So most of the time, you can just paralell the main wires and charge at least 4 packs at a time on one charger.

My personal setup I find fairly convenient, but still a bit slow. One 350w meanwell power supply and two 150w chargers. I often put 8 packs on the two chargers, four per charger. Faster would be nice, like two 300w chargers.

For one box charging, look into bulk charging, using an HVC LVC board, or drop to 14s, where you can get a hyperion 14s charger.

dogman said:

Bear in mind, that you can paralell packs, and charge and balance them all at once. You should be able to easily ride all week without balancing. So most of the time, you can just paralell the main wires and charge at least 4 packs at a time on one charger.

My personal setup I find fairly convenient, but still a bit slow. One 350w meanwell power supply and two 150w chargers. I often put 8 packs on the two chargers, four per charger. Faster would be nice, like two 300w chargers.

For one box charging, look into bulk charging, using an HVC LVC board, or drop to 14s, where you can get a hyperion 14s charger.

Click to expand...

Thanks for this information. I have a new thought about charging thanks to you.

I rewired my diagram for charging and discharging (included) and as far as I can tell, this could work right???

Looks good to me. Only nit pick is that the connection of the battery to the charger is slightly different. The main wires paralell to 8s, and plug into one port of the charger. Then seperately, the 8s balance wires get paralelled and then they plug into the charger in another port of the charger.

90% of the time, you don't really need to balance. So most of your charges can use just the big main wires, leaving your balance wire plugs alone.

BTW, you should remove the alarms when you park the bike overnight or longer, so they don't drain the cells in storage.

Thanks very much for your revision of my connection diagram

Of course I know that balance wires and main power wires has separate ports in charger. I just draw it that way, because in this moment I still do not know what exact charger I will buy

Cell alarm will be connected only during rides. During winter storage I will be checking cell voltages only once in a while.

but this is a lifepo4 pack and not a lipo pack. i think everyone thinks you have lipo.

why would you not use a bulk charger and BMS? you would get higher charging rates and have the LVC and HVC monitoring too as well as balancing.

Yes, that is LiFePo pack. Of course BMS would be great, but every bms I could find here (Czech Republic) is either very expensive or unusable for 20aH pack. Only affordable BMS I found for me would be this: http://www.ev-power.eu/SBM-CBM-1-1/Simple-Battery-Management-Board-16-cells-48V-60A.html

But according of specs for this BMS, it has balancing current only 72mA which seems unusably low to me, but what is worse, overcharge protection is 3,9V and overdischarge is 2.0V. I thinks both margins are far beyond damaging of cells (I would rather go between 2.7V and 3.7V).

So I decided to not use BMS and rather go with RC charger and cell alarm, because I would like to have absolute control about my battery pack.

No particular reason you can't self monitor and use an RC charger with lifepo4. You'd use the lifepo4 setting on the charger of course.

You still get reasonably accurate charging including balancing. On the discharge side, you can use a controller lvc as a drop dead cutoff before the entire pack got ruined. Then pay attention to monitoring devices/ alarms just as we do with lipo.

Balancing with RC chargers, well cheap ones anyway, is still slow. But at the end of charge, bringing up a few low cells by single cell charging them through the balance wires with the RC charger is fast.

Out on the road, I wouldn't hesitate to bulk charge without the bms, but just use a lifepo4 charger with a conservative end point. That is, get one set to 56v, instead of 60v.

I've been thinking about an A123 pouch pack in 48v. Seems like a good plan to me to do both. Have a bms, but also have additional charging/discharging ports including two 8s balance plugs. That way you get the best of both methods avaliable in one pack. Then with a few plugs, you could paralell in more anytime, and discharge through the one bms easily. I'm already thinking in terms of it being two 8s packs for pannier carry, and one would plug into the other to run through a single bms.

nothing wrong with 3.9V and 2.1V limits. they are perfectly safe for the lifepo4.

ping sells useful BMSs cheap and you can buy the headway BMS for a little more. then you can get useful charging rates with a bulk charger.

I would definitely like to have system with BMS and charge with higher rates by bulk charger. I could find some BMS over some company in the world which would send it to Czech Republic

To dnmun: On datasheet which is included with those 20Ah cells there is voltage treshold between 2,7V and 3,8V and there is sentence that cells will be damage if voltage exceeds those limits, so I would rather stay within this voltage range.

Cells real world usefull life is 3.6v - 3.1v after that there is little power.

999zip999 said:

Cells real world usefull life is 3.6v - 3.1v after that there is little power.

Click to expand...

I realize that, this is the reason I would like to have BMS with some more conservative voltage tresholds.

Do you think it would destroy the cells if it is discharged to 2.0V or charged to 3,9V? According datasheet for those cells there is limit 2,7V - 3,8V as I stated above.