Parallel and series flexibility

[staft]

Okay, as I close in on battery options, I want to make sure I understand how batteries work in the real world.

If I had 4 lipo packs, eg., wired at 2p12s, could the pack be rewired to suit my needs o' the day? 4p6s for increased range at the expense of speed, then back again the next day? Or does this give batteries an identity complex? Same for Lifepo4?

Also, if I understand right (big IF), making a pack by starting with sub-packs wired in parallel makes more sense because you will be disconnecting the series connections to balance the cells anyway. Correct? If so, what do you do for individual cell balancing if you have a couple of 1p12s lipo packs like this: ( http://www.hobbyking.com/hobbyking/store/%5F%5F17914%5F%5FZIPPY%5FFlightmax%5F4500mAh%5F10S1P%5F30C%5FLong%5FLipo%5FPack%5FUSA%5FWarehouse%5F.html )? Is there a charging method that will balance them still in the pack? Or have I got this all wrong? Is it better to buy packs already wired in parallel instead of series? And then, there is the issue of charging - you can find chargers that will charge strings in series, but it won't make a difference if you have cells in parallel - is that true?

How do cycle analysts connect - to battery or controller? Is this a common connector to find on a controller/battery, or do you typically need to add one?

Finally, is there a standard connector type that most controllers will come with, or is it pot luck?

My appreciation for your continuing patience...

 

[dogman dan]

It's all very complicated and confusing at first. Keep reading, especially in the lipo noob links in FAQ at first.

Generally, you don't have to balance every cycle. So that simplifies a great deal of your charging.

There is the bulk charge approach, where you either feel no need to balance, or you add some fairly pricy lvc hvc boards. These boards are not really mass produced yet, so a bit costly.

Or if you use RC chargers, you can break the packs into subunits small enough for the charger you have chosen. For example, 4- 6s packs that are in 12s 2p configuration. you disconnect your series connection, and now have two sets of 6s 2p. The packs are paralelled at the big discharge wires, and you have also paralelled them at the balance plugs with a y adapter. Now you just put each pair on an RC charger, plug in the balance wire, and select 6s balance charge lipo on the charger. How long this takes depends on how much you spent on the charger.

CA's come in two basic types. One is DP. This works with controllers that have a CA plug. With DP, you get to use all the CA functions, like amp limiting. Very handy. With the stand alone DP, you only get to measure things, watts, amps, watthours, miles, speed, wh/mi, ah used, etc. On the stand alone, you connect the shunt on the CA to the battery, then the other end of the shunt goes to the controller.

Connectors vary by vendor. Many like andersons, others prefer bullets. Figure on buying some connectors, so you can be sure you have compatibility. Or get everything from one vendor that promises the connectors will all fit, like Grin Cyclery.

In practice, you don't have to balance every ten cycles or whatever. Using a cellog 8, you can quickly check your packs, and only need to balance charger when it's actually out of balance by much. I call .1 out of balance, and .05 slightly out. Don't fret about balancing when it's only out .01, or .015 or some similar tiny bit.

90% of the time, you just hook up the main wires, and select non balance charge, 6s.

Balancing is not nearly the big deal with lipo. The BIG DEAL is not overdischarging them. Stop in time, by having a way to know your voltage. Stop in time, by knowing your range, and staying well within it.

 

[staft]

Thanks! Does this mean I shouldn't buy any 12s lipo packs unless I can find a 12s charger?

 

[Ykick]

Thanks! Does this mean I shouldn't buy any 12s lipo packs unless I can find a 12s charger?

12S is simply 2qty 6S (22V) bricks series wired for 44V. A 6S charger will work if you break 'em down but once you better understand how things work you'll probably find other ways to balance bricks if/when needed.

12S2P is a great starter configuration and fairly easy to bulk charge directly using 48V Meanwell power supply. You can check balance with a cell log without breaking the bricks down to 6S. Perhaps charge low cells directly though the balance connector without breaking 12S series wiring apart? And/or use a BM6 (battery medic) in addition to serial bulk charging.

It's hard to fully understand all the options available until you have some bricks in hand, your connectors of choice, power meter, cell log, BM6, RC and/or bulk charger? At minimum, have inline power meter to keep track of what's going in/out.

 

[Partycat]

12S actually seemed like a pretty reasonable starting configuration for LiPo, and it works relatively low with the readily available low-voltage-cutoff and balancing kit, and the Hyperion 14s capable charger. I've been off the board and the batteries for the last 6 - 8 months so something new may have come up in the meanwhile.

I'm not sure you'd get much of anywhere at 6s, that pack voltage would be miserable I'd think.

I had my pack split, 6s4p and 6s4p which made charging easier at certain times. I found the Hyperion charger didn't like the DC power my modded server PC power supply was giving it, and it would end up reading the wrong cell voltages on bank B. If I gave it a good clean 12V power source, instead of one that was a bit "higher" it worked just fine, but, I don't have any clean 45A power supplies floating around, and the rest of the bench supplies I have rarely like to run at "continuous" ratings without getting extremely hot in a short time, so I charged the pack split 6 and 6.

The biggest hassle was the wiring. The balance and LVC board was great, but, once all the wires were condensed it it way easy to have things crossed, twisted, etc.

I reterminated my packs with Anderson power poles, but, my crimper blew up two crimps in and the fine stranded copper was a massive pain to get assembled. If I had to do it again I would just go with the bullets so I wouldn't have to screw with the APPs, but, they seem more "protected" from accidental short.

The controller I purchased from Lyen came with ... I want to say ... bullets? on it, but, it is pretty trivial to replace those connectors. I replaced the phase and hall wire connectors with APPs and made a nice rainbow square connector for that whole affair.

If you charge in series then the cells connected in series will "Even out" with each other, but, balancing typically refers to triyng to get a unified value across all the cells in parallel so that your total pack voltage readings are accurate when you are charging/discharging, especially in bulk. If you expect to stop at 45V then you want to be sure you're "topping it off" evenly so nothing overflows.

Charging in series on a balance charger makes balancing take forever, and the things seem to end up off by little amounts which cause a balance cycle. It's not too bad though. My packs have been off my bike for the last 6 months and they're all within .1 or less on the cells and pretty much holding at storage voltage. I don't think I ever posted about my build and experiences, maybe I'll do that later.

 

[dogman dan]

I've not seen 12s pack, just the 10s pack you linked to. Yes, you'd need a 10s capable charger for it. One of the best chargers out there, a Hyperion, is 14s capable.

Personally, I would prefer two 6s packs to a 12s one. With a 6s pack, if one cell goes tits up, you have to buy a 6s pack to replace it. With a 12s pack, replacing a pack because of one bad cell would cost twice as much. You could still charge at 12s with that hyperion 14s charger.

 

[staft]

Okay, as usual with you guys, the more questions you answer, the more questions get stirred up! Between you all and migueraliart, who sent me the following very useful link: http://scriptasylum.com/rc_speed/lipo.html (which should go in the sticky, maybe) I am feeling sorted out about basic wiring. But clearly I have much to still learn about the many devices you bring up for maintaining my batteries. Assuming I were to get a 12s2p lipo setup, what is the must-have basic kit for taking good care of them? Economy is important, but I don't want to be re-acquiring shoddy meters or chargers after 6 months, either. I am hearing about on-bike metering, alarms for LVC-HVC, BM6, Balancers/balancing chargers, bulk chargers, cycle analyst, multimeters, inline power meters, ad infinitum. I assume I won't be able to plunk down for everything at once, so what is best to start with? Will any of these allow me to skip other parts, like a BMS or harnesses?
And what about safe charging bags - a good idea to keep batts in bags on the bike as well as charging, or not even necessary?

Suggestions for specific brands/models appreciated! I am an electronics babe in the woods, so assume I know next to nothing.

As always, I'm indebted.

 

[dogman dan]

The bulk charging crowd will strongly disagree, but I think you should start out with something similar to what I have.

Why? I just think if you are going to get into lipo at all, the starting point is a decent RC charger. Very handy to have, even if you are going to head for bulk charging later. But as the starter, it's great because you can charge and or balance any number of cells with it. As you learn, you may screw up, and suddenly your 12s pack is now 11s. Now what if you are stuck with bulk charging a certain voltage.

This is a good USA supplier. Not the cheapest, but a solid vendor with a solid return policy for anything that craps out right away. http://epbuddy.com/index.php?main_page=product_info&cPath=17_20&products_id=168

You can shave a few bux with a scrounged power supply, or a different charger, but this combo shows a solid setup with a meanwell and a decent charger. My own setup is a meanwell and two cheaper 150w chargers.

As I said, most of the time you don't need to balance. One really good way to do your charging setup is to buy or imitate Icecube 57's paralell series harness. Info in the review section, and in the for sale new section. The idea is a harness is attached to the batts. Then there is another two harnesses. One stays on the charger, the other on the bike. The bike one makes a 12s to run, the other paralells them all for one plug charging at 6s. Once in a while, you check each pack with a cellog 8, and seperate out any packs that need a balance charge. Swapping from charge to run is simple and foolproof. One plug, a few seconds, and you are back to 12s to run the bike.

Very simple, and ideal for noobs running 12s. Very cheap. If you really must, you can go mega cheap with a 50w charger. But it will be excruciatingly slow, so I don't recomend it. Get at least 150w of charger.

 

[Ykick]

The bitch about RC Lipo is that it requires a significant investment for proper testing, charging and maintenance equipment. However, once you make that investment you'll be able to replace cells economically for years down the road. Plus, you'll have everything needed to advance your education in battery tech. Which is not a bad thing to be educated about in this day and age.

While there are shortcuts to practical application serial bulk charging, it's way too complicated and risky to provide that advice. I'd put a power meter, cell log, RC Charger and power supply on my must have list. Trouble is, the later is the toughest decision because if you go small and cheap, you'll be dealing with series/parallel connections and slow charge times.

I dare say many of us move on to serial bulk charging because we bought too small/weak RC Chargers and grow weary of the lame performance. Even with an RC Charger you don't need to balance charge every cycle and something like the 14S Hyperion can possibly serve as a serial bulk charger?

It's surprisingly simple and reasonably safe once you have some experience but until you do, it's daunting and potentially dangerous. As a rough estimate, $200-$300 for chargers, power supplies and meters should put you in a good position to start working with RC Lipo bricks. Oh crap, don't forget wire, connectors, soldering iron, crimp tool, etc. Most of us probably had that type stuff laying around but if not, you'll need to get up to speed there too.

 

[dogman dan]

Good advice. I made a big mistake buying a couble little b6 chargers. But maybe not really, since I was so clueless at the time. The 50 w chargers were a cheap mistake though. Just soooo dang uselessly sloooooow. I still use em, usually when dorking around with a wonky pack, like to bring up a single cell at 1 amp. So like 5w charging...

My current setup with 300w of charging power is not bad at all. Not fast, but not crazy slow either. Seemed costly at the time, but now after a year and a half of use, well worth every penny, and likely to outlast lots of battery packs. Only time it's too slow is at the racetrack.