Any solution for 20s or greater balance charger?

[John in CR]

I want to make the Lipo leap soon as well as put my lifepo4 cells to good use, so I need charge voltage flexibility, but I don't want to run a full blown BMS. My packs will be broad in parallel structure, and I will rarely, if ever, go past 70-80% DOD and more typically I run 30-50% DOD, so I believe the risk of killing cells from not having a BMS is lower than a BMS problem killing cells.

My packs stay on my bikes, and I don't want any unplugging series/parallel connections. Instead, all of the series and parallel connections will be permanent, and I will tie the parallel structure together down to the cell level so I end up one balance tap for each series level of cells. Then I'll bulk charge via a master +/- for the entire pack, and periodically balance charge via the balance taps.

I'll have a variety of packs 20s, 24s, and maybe even some 30-36s packs. Plus on one dual motor bike I may want to draw 200-300A, so even if I trusted BMS's to be pretty much failure proof, the cost of BMSs for my packs wouldn't make economic sense. ie I would have to blow multiple packs before the cost of the lost cells exceeded the cost of the BMSs I need.

I would like to come up with a flexible solution for under $500 including relatively high power bulk charging capacity that isn't too detailed in the start-up for balance charging, which would make the odds of mistakes greater.

My balancing options seem to be:
1. Use BMSs (1 lifepo4 and 1 lipo) that I connect just for balance charging. Are BMSs flexible? eg Can I plug a 24s BMS to a 20s or 23s pack too? Are they programmable or switchable? ie Can the same BMS charge my LiMn cells to 4.1v, Lipo cells to 4.15, and Lifepo4 to 3.6 or 3.65?

2. Just get a bunch of single cell chargers. Do they even exist for Lipo voltages? Are they very dependable?

3. Use a group of RC chargers with separate power supplies. This seems to offer the best flexibility in terms of cell types, but my biggest issue is avoiding a detailed setup each time I want to charge. I'm very spoiled by almost 2 years of just pulling into my carport, plugging in a 2 wire connector and pushing a single start button.

4. Something new that I don't know about.

What do you guys recommend? Any horror stories with single cell chargers?

John

 

[hydro-one]

Hey John. You will be plugging in and walking away. Bulk charge dont forget..... You will only balance once a month or so, if your packs are well matched. Im going to buy some HC balance chargers and daisy chain them with separate 12v supplies like what dr. bass suggests here...http://endless-sphere.com/forums/viewtopic.php?f=14&t=17561&start=15 (end of page)... Bulk with a meanwell set to cutoff. Simple as that for lipos. oh and at least pack lvc.

Also cellogs would be good for discharge/charge (lvc and charger cutoff) but thats more work.....

it really is endlesss.........

 

[geetarboy]

Hey John, I have 126 cycles on my lipoly's now and have been using single pack chargers. It is less convenient than bulk charging, however I have had 2 packs go bad now. That is out of 20 packs and I was able to catch them early. That is the benefit of individual charging. They discharge very evenly down to 80% capacity and after that they can get way out of balance. It would be nice to have a balancing bulk charger. Good Luck...Mark

 

[recumbent]

Why don't you simply have one block of cells wired in parallel, (i use 3, 8s lipo) for passive balancing.

Then another block in the other pannier paralleled (that's what I'm doing) THEN wire these two blocks in series to the controler. But have an extra "-" and "+" lead for charger and monitoring at the same time with the CA. Works great.

Simply have Celllogs on each bank (or side) for extra security, but your Cycle Analyst will be your first warning if something bad is happening. My history has shown that Lipo,s and lifepo4 want to stay balanced, and always have in my useage.

Good luck, and show us what you finaly choose.

 

[John in CR]

Why don't you simply have one block of cells wired in parallel, (i use 3, 8s lipo) for passive balancing.

Then another block in the other pannier paralleled (that's what I'm doing) THEN wire these two blocks in series to the controler. But have an extra "-" and "+" lead for charger and monitoring at the same time with the CA. Works great.

Simply have Celllogs on each bank (or side) for extra security, but your Cycle Analyst will be your first warning if something bad is happening. My history has shown that Lipo,s and lifepo4 want to stay balanced, and always have in my useage.

Good luck, and show us what you finaly choose.

I can´t have blocks connected both in parallel and series other than a split second of plasma flash. If you mean disconnect the series connection and connect in parallel for charging, I have no interest in doing that kind of thing, because I believe it´s begs for errors like many have experienced. Plus I simply don´t want the inconvenience, because convenient and easy is one of my favorite things about my ebikes.

Regarding cell logs etc. I want to run them first without any real time monitoring. I think I run my packs conservatively enough that I won´t need them, and my feeling is that the less things I connect to my packs, the less points of failure I have. Even the hard wiring of the balance taps is more than I´d like, so I´ll take extra care in making sure they are overbuilt and well protected. In the early stages I will manually check how well things stay balanced pretty often just like I did with my Konion cell packs, and then evaluate whether or not I need real time voltage monitoring.

The only reasons I need to supplement my Konion packs with packs of batteries with other chemistries is my need for some higher power short range packs, and the supply of Konions is quite limited. If I could buy new Sony US18650V cells for $.50/wh or less, that´s all I would use, because they are so convenient. eg They have the same energy density as the RC lipo packs, and I have packs made with used cells that I´ve put well over 500 cycles on since the last time I´ve checked them for balance, and they´re still going strong with bulk charging only.

John

 

[drewjet]

I use the FMA Balance chargers. As long as the power supplies are isolated they work great. I use a 9 pin computer connector for each bank of 6 series. So for my motorcycle on 72 volts it is 3 connectors and turn on power supplies. Very easy very dependable. I use the same on my bikes except they run 48 volts and only use 2 connectors.

 

[nicobie]

I bought one of these. It has 36 pins, 4 will handle 16g and 32 will hold 18g. It has a nice movement, you don't just pull it apart, you twist it apart. It's real easy to plug together. 36 pins is enough for 24s It's pins are gold plated and will easily handle the 2a my rc chargers will put out. I'm not looking forward to all the soldering, but when done, it will make charging easy and fool proof. (I hope)

Price is right with free shipping too.

http://cgi.ebay.com/1-Military-36-Pin-Male-Female-Circular-Connector-F36-/170516813104?pt=LH_DefaultDomain_0&hash=item27b3981530#ht_1158wt_905

 

[John in CR]

I use the FMA Balance chargers. As long as the power supplies are isolated they work great. I use a 9 pin computer connector for each bank of 6 series. So for my motorcycle on 72 volts it is 3 connectors and turn on power supplies. Very easy very dependable. I use the same on my bikes except they run 48 volts and only use 2 connectors.

That FMA 10s charger looks nice. I especially like that it reports cell internal resistance. I was considering pulling the trigger on 2 till I saw reports of problems this summer. I think maybe I should try the Dr Bass mods to the Turnigy 4x6 charger I picked up cheap before I realized they weren't isolated, and just suffer through the tedious balancing routine since that will only be once a week or so. Hopefully someone comes out with specifically for us in the near future. I know it will come, only when is the question just like with 2 or 3spd transmissions up to the task of more that a few hundred watts of power.

Thanks all. If anyone is aware of good but cheap 6s or 8s balance chargers that will do both lipo and lifepo4 that will retain the last settings, so I can just hit the start button as long as I'm not changing chemistry, please let me know.

John

 

[drewjet]

That would be the FMA 6s BalancePro charger. It is what I have. They are no longer in production, but do show up on ebay from time to time for around $50 to $60 each. Puts out 10 amps and most versions have a A123 setting.

 

[docnjoj]

Fatpacks and Konions rule John. If they ever come down in price again they will rule the marketplace again! JMHO
otherdoc

 

[John in CR]

Fatpacks and Konions rule John. If they ever come down in price again they will rule the marketplace again! JMHO
otherdoc

I can't get past the 40% lower capacity of the VT cells though. That means 40% more weight and space for the same amount of capacity. After you factor in the higher capacity of the V cells, the higher C rate of the VTs is almost meaningless. I ran one of my big motors on one of my bikes for a year with just 6p of the V cells and that was a leftovers pack of only moderately matched cells. At 40A peak current the pack would barely get warm. My 12p pack stays cool even with 120A peaks.

I've been trying to work my way through the big company bureaucracy to get the Sony V cells in 2p5s or 10s matched cell blocks for a while. That would be so sweet for all of us, and except for those who really need the high C rate, everyone would forget this RC stuff, because based on the prices I've gotten for other 18650's we should be able to do better than $.50/wh plus shipping. Easy to assemble packs to whatever shape we want would be great.

 

[jdcburg]

If anyone is aware of good but cheap 6s or 8s balance chargers that will do both lipo and lifepo4 that will retain the last settings, so I can just hit the start button as long as I'm not changing chemistry, please let me know.

John - look at the Accucel 8150 - $42 from HK http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7523 Suitable for multiple chemistries including Lipo or LiFePO4, retains last setting, also programmable so you can load a different preloaded setting with a few button pushes. You can read or download the pdf manual here http://www.hobbyking.com/hobbyking/store/uploads/manual%281%29.pdf You'll need a power supply for it. I started using an old 12V sla and charger but eventually made a PS from an ATX computer PS - jd

 

[docnjoj]

I can't get past the 40% lower capacity of the VT cells though. That means 40% more weight and space for the same amount of capacity. After you factor in the higher capacity of the V cells, the higher C rate of the VTs is almost meaningless. I ran one of my big motors on one of my bikes for a year with just 6p of the V cells and that was a leftovers pack of only moderately matched cells. At 40A peak current the pack would barely get warm. My 12p pack stays cool even with 120A peaks.

I've been trying to work my way through the big company bureaucracy to get the Sony V cells in 2p5s or 10s matched cell blocks for a while. That would be so sweet for all of us, and except for those who really need the high C rate, everyone would forget this RC stuff, because based on the prices I've gotten for other 18650's we should be able to do better than $.50/wh plus shipping. Easy to assemble packs to whatever shape we want would be great.

[/quote]

The V cells are what are in Makita 3ah packs? The VT cells are in Fatpacks? I never can get this straight but you are so right that capacity, in most of our situations is more important than absolute d/c rate max. So you really think this will happen?
otherDoc

 

[John in CR]

Yes, the 1.5-1.6ah V cells are in the 3ah Makitas. The Bosch fatpacks and slim Makita packs have the VT cells.

Will it happen? Who knows. I spent a bunch of time and emails, phone calls and meetings last year with people from the South America division of Bosch, which ended up a waste because Corporate shot it down since they were coming up with their own ebike system. I'll let you know when they come out commercials that were actually my idea. If this time pans out then great, but I won't get excited till I get a 1000 cell sample "for testing". My need presented is totally different this time, and it has only 1 competitor unlike the ebike business, so I´m cautiously hopeful that they will deal with a startup company.

John

 

[smeagol222]

Any updates on this 6yrs later?