Serial Battery pack and parallel charging

[perpete]

Hi.
I am a newbie in the lipo world although I have some electric and electronics knowdledge.

I plan to do a 12S setup for my bike. I have bought 3 x 4S 8000mah packs that I plan to connect in Series to get the 12S.

I would like to make a stupid proof connection, and I would like to do it as easy as possible to charge, trying to avoid disconnecting many connectors.

I have thought about connecting the batteries in series using their own 5.5 bullet conectors to each other and set up a XT60 conector at the end to connect the whole pack to the controller.

My charger can charge only 8S maximun. I have bought a parallel and series ballance board as well.

But this setup means that every time I have to recharge, I have to disconnect the three packs, connect them in parallel to the board ( or one by one three times), then charge, then disconnect, connect them in series again to use it.

Is it any way to do it easy way or I do I have to buy a bulk charger from BMS and balance from time to time?

I have thought also in using only bullet connectors and disconect one pack a time, charge and next, to avoid stupid mistakes.

I have also a color coded wires end mark to avoid mistakes connecting them.

Thanks a lot in advance

 

[Tench]

I felt the same on my first venture into lipo so made a series parallel changer, there is a thread about it here;

http://endless-sphere.com/forums/viewtopic.php?f=2&t=39489&p=693460&hilit=series+parralel+changer#p693460

one of the links at the bottom of my post is the build thread for that bike, plenty of info on how I did it. There are others one here with good solutions too, use the search function.

 

[dnmun]

you can use a lipo BMS and bulk charger. that will allow you to balance the pack and give you protection from short circuit on the output and over charge and over discharge protection. and cheaper.

 

[perpete]

I felt the same on my first venture into lipo so made a series parallel changer, there is a thread about it here;

http://endless-sphere.com/forums/viewtopic.php?f=2&t=39489&p=693460&hilit=series+parralel+changer#p693460

one of the links at the bottom of my post is the build thread for that bike, plenty of info on how I did it. There are others one here with good solutions too, use the search function.

Unbelieveble. Very smart solution. I have a lot to think about.

Thanks a lot!!

 

[friendly1uk]

You listed a few options Perpete, but not the proper one. A bms. Or battery management system to give it the proper term. At 12s you only need a $20 one. It looks after everything. Making it has hard to charge your bike as it is to charge your phone. You would pair that with a bulk charger worth about $40. That is how all consumer packs are built. A little board that lives on the bike permanently. It does a fair few jobs, including the balancing. At 12s I imagine you have a 36v controller that offers no suitable lvc, and many packs are nailed for this reason alone. The board covers it though. Along with overload and short circuit protection.

Most RC chargers are no good. Give them a pack with 1 cell at zero volts and the other 11 at 3v. They will try and charge the lot, and stop when one of the 11 hits hvc. A bms would stop you using that pack because it watch's while the pack is in use. An RC charger offers no protection because it is not on the bike, so that cell will drop to zero volts, risking fire damage. Few RC chargers spot the massive variance in cell voltage when they do get plugged in. They are dumb devices and don't offer half the protection some people think they do. They will keep cycling that dead cell because they just don't understand. You may think the one's that link to the PC for logging are going to be good enough to offer this extra level of protection, but we have seen them cycling bad cells too. It is just dumb RC gear. You should really do it properly. Which is usually the cheaper option too.

 

[perpete]

Well IT's a good idea. althought the controller has a lvc I think, it's a lyen minimoster so I think I can program the LVC.
In the other hand I couldn't find many BMS for 12S Lipos, actually I couldn't find any price, I just remember one webpage with no prices in it.
Of course I's the easiest and comfortable idea, ideally if you can program the LVC the max charge voltage and so on to your preferences.
I intend to maximice the cycles and babycare the batteries from 4.1 to 3.5 volts.
I would apprecciate if you could give me any link to a bms like this in a web with prices but I'll start to search again myself.

I wouldn't know that the rc chargers where so dum, actually I bought one because I thought they were 'smart chargers' controlling lvc, top voltage, current amp charge and so on.

Thanks a lot for your help.

 

[dnmun]

you can buy a BMS for lipo from bestechpower.com and i expect you could buy the D167 for about $55 delivered DHL.

http://www.bestekpower.com/pcmbmspcbforli-ionli-polymerbatterypacks/

you really do not understand LVC. a BMS will detect low voltage on individual cells, the LVC you talk about is for controllers to prevent over discharging SLA batteries so it is not anything related to the lipo packs.

 

[dogman dan]

An RC charger can be the charging half of a bms. If you select balance charge every time, which means some more parallel connections to make on the balance plugs.

I did so many non balancing charges with no problems, I realized that I was bulk charging even though I used two RC chargers.

If you don't mind spending on the charger, a 12s or 14s RC charger will do the job without any paralleling. But there are various rigs that you can plug into to do the paralleling to use a 6s charger if you have one now. Make sure you always unplug all series connections first to hook up. I fried two paraboards forgetting to do that, and hooking up the balance taps of series connected packs.

As for discharge, setting an LVC should be able to prevent you from having a cell go below 2.7v. If you did have one go to 2.7v while all the others were at 3.75 or so, well, you had a cell that really really needed to be put in the trash anyway. That far off, I'd want it gone asap before it burns the house down. One that bad is likely to have been damaged, be leaking electrolyte, or puffed all to hell.

I try to stop before the cells go over the discharge cliff, closer to 3.65v per cell. This is just because once close to 3.5v, you can blink and the pack goes even lower. So sizing the pack so your typical ride never goes to 3.5v can be a much more effective method than an LVC. Too much trouble worrying about that last block. Dial in your route so you make the distance with plenty of spare wh, and don't have to ride staring at a wattmeter.

 

[izeman]

... a 12s or 14s RC charger will do the job without any paralleling. ...

this would be my recommendation. build a small harness to combine the 3x 4s plugs into one 12s (or 2x 6s - whatever your charger can handle) or desolder the balance leads and resolder 2x 6s plugs to it.
that's a very bullet proof solution. only one thing you have to take care of: you must not swap the 2 6s plug for each other.
or you buy 2x bc168 chargers and charge through the balance leads. with 4a (i wouldn't set more) your pack will be charged in 2h.

 

[docnjoj]

Interesting izeman. I have a Thunder 1220 and a Hyperion 1420 and have accidentally reversed the two, 6S balance leads on my 12S battery. All I get is an error message, no fireworks. I then put them in the correct order and the chargers then balance charge There are failsafes in both chargers to protect the forgetful like me, at least that has been my experience.
otherDoc

 

[izeman]

Interesting izeman. I have a Thunder 1220 and a Hyperion 1420 and have accidentally reversed the two, 6S balance leads on my 12S battery. All I get is an error message, no fireworks. I then put them in the correct order and the chargers then balance charge There are failsafes in both chargers to protect the forgetful like me, at least that has been my experience.
otherDoc

great. that's good news. you never know how clever they are designed, and I WOULD EXPECT it to be the way you described it. but you never know. better be safe then sorry i don't have a bigger then 6s charger, so i was just telling what would make sense from my point of view, and what i know of chinese product *ggg*
so i guess one if these chargers maybe the safest solution for him to use for charging without any hassle.

 

[perpete]

Ok I have read carefully.

I think that I have two options.

I have seen the BMS they have in BMSbattery that it's very cheap and looks very nice. It cost 20 bucks and can be customized so It look perfect for me.

http://www.bmsbattery.com/smart/330-lifepo4lithium-ion-smart-bms-for-513-cells-in-series.html

I think that it can be customize dto 3,6 lvc and 4,10 Over voltage protection, leave it in the bike and buy the bulk charger they have for 40 bucks

http://www.bmsbattery.com/alloy-shell/25-alloy-shell-240w-lifepo4li-ionlead-acid-battery-ebike-charger.html

What would be the best settings for the bulk charger and for the BMD to be very conservative? 3,6v and 4,15 for the BMS and 49,8V and 4Ah for the charger would be ok?

This seems to be very fool proof as you said, pity is that the icharger 208 would be totally useless but I could always sell it in ebay

In the other hand and saving some money, taking in consideration the stuff I already bought and with all the ideas you gave. I though that

I could put a XT60 connector in each one of the 4S packs, then on the bike, I could do a serial bridge, permanent attached to the controller to make the 12S so I should have to connect each one of the 3 XT60 to the brige and then I could put a buzzer alarm ( programable) to the packs to control the LVC.

Something like that.

Then for charging I should disconnect the 3 packs and connect them to the parallel board ( that would be permanent connected to the icharger ) as well as the balancing leads to the board, and charge them in parallel

I think that IT's quite bullet proof ¿What do you think?

Thanks a lot.