lipo balancer q?
 

i plan on getting the new mrc 977 charger, and it can charge 2 3s lipo packs independently so i shouldent need a balancer right?
also i plan on wiring them in perallel in my truck so i can get longer run times do i need some kind of balancer for in the truck?
1 more thing will 1 3s low voltage cut off thing work on 2 3s packs (3s3p total) or do i need 2 of them?

If I got it right the 2 packs are going in parrellal. They are 3s 3p each pack so that make you running 3s6p. The 3s low volatage cut off should work with this set up. A balance equalizes each cell in the pack to make sure the voltage is equal in all the cells.

You will still need a balancer if you want the packs to stay in balance during the charge.
There is no balance device for parallel packs. As long as the voltage of the two packs is very similar, then you are good to go.

So your saying that you need a balancer for each pack while charging, or that you need to charge each pack seperately.

Sorry for the hijack, but i'm curious to.

sorry for the confusing post :o i posted it when i was half a asleep lol. ok so each pack is just a 3s pack, 3 cells in series to get 11.1 volts. i plan in wireing the two packs togeather with a y splitter so i can run them at 11.1 volts but get incressed run times. do i need to run a balancer on board the truck to keep both packs voltage the same or? now the charger it as to charging ports im going to charge 1 pack on one charging port and the other pack on the other do i need a balancer for the 2 packs even though they are charging basicly on to diff chargers. now the low voltage cutoff should work them sence it is 3s3p total right? one thing i know is that i need a balancer for each pack to keep the cells in the pack th same but, im just trying to save as much money as posable dont wont to have to buy like 6 of them.

Charging them ballanced is more criticall. just get a voltage cutoff.

If you were to charge both packs on different channels, you would still need one balancer per pack. If you were to charge both packs in parallel, you would still need two balancers. Any 3s cutoff will work with any 3s Lipo battery. Parallel has nothing to do with the number of cells in series. No balancer on the truck, as balancing is only done during charging (or right after a charge).

So the balancer works without the charger?

The balancer is used in conjunction with a charger. The balancer balances a pack during charging (usually at the end of the charge is when it will kick in).

Ok, i understand now

Do you run the charger threw the balancer? Or do you hook it up like normal and the balancer to the other balancer connector?

Usually you plug the balancer into the charger, and the charger into the battery. I have seen some rare cases where you can plug the charger into the balancer, and the balancer into the battery, but they are uncommon.

ok, metalman, my head's spinning.. I've got 2s 3100mah polyquest packs.. and AF109d chargers (i know you've already said that that charger isn't recomended w/ balancers..)

now, I've got PCM's, which you said were not balancers.. so the PCM makes sure that the packs are not over charged correct?
and a balancer would make sure that both cells charge equally..

so if I were to use a balancer, would I use the pcm as well? the pcm plugs into the pcm jack on the packs, and then into the charger.. is there a way to put a balancer between the pcm and battery or charger? or... gimme a hint.. I havn't tried charging the packs yet, so don't want to mess it up..
btw, what balancers would work with my cells?

thanks for any help in advance.
-nick

The PCM guards make sure that no cell in a pack is charged to over 4.25v (or somewhere around there). If a cell does reach 4.25v, the PCM guard will terminate the charge by creating an open circuit between the charger and battery. It is able to do this since it connects directly to the battery and the charger plugs into it. A balancer will do what its name says.

Generally you wouldn't use the PCM guard and a balancer at the same time because Lipo packs only have one set of balancing leads (and 1 connector). A balancer would plug into the "PCM jack" on a battery. This "PCM jack" is merely a plug that provides a direct connection to each internal cell of a pack.
Balancers work with any Lipo cells, as long as there are taps (direct connection to internal cells via a connector).

thanks a ton for replies metalman. now.. this is what I have:
http://www.starluckrc.com/catalog/pr...products_id=72

says that it monitors individual cell voltage.. if I used this every time I charged the packs, wouldn't that "balance" the cells? it'd charge each cell to the maximum voltage independently correct?
so if for whatever reason the cells became unbalanced durring discharge, when I went to charge it again using the PCM, it would charge each cell to the maximum voltage again, and therefore re-balance them.. correct?

The PCM will cut the charge as soon as a cell gets to 4.25v, and that's it. It will monitor each cell independently to see if any get to 4.25v, but it certainely won't balance the battery (which is what individual cell charging would do). When the PCM cuts the battery off, that means that you need to balance the pack.

Here is what the PCM guard does;

it cuts of the pack when 1 cell reached the 4,25 volts. it simple doesn't balance the cells, it's just a warning device, that tells you when the pack is in unbalance. nothing more...

Here is what a proper balancer does;

during the charge proces it monitors and adjusts the charging proces of each cell, not only at 4.25 volts, like the polyquest PCM, but continuesly, thru the whole charging proces

You need to balance the cells at some point. discharging or charging. imo it is the best to do it at charging, because only then, you know that all the are equal when you give them the big load or torsing a monster truck thru the fields..

Balancing during charge really is the only way to balance a Lipo. Balancing at discharge would be pointless because of the slight variations of resistance between cells. Also, constant voltage during charging is much easier than it would be for discharging.

back to me you tread jackers:p. hey i just wont to know
how a balancer hooks up? im thinking that the chargers out put goes in to the balancer and then the pack connects to the balancer :C: . im cornfuzed can any buddy draw up somthin for my simple brain

A balancer can be hooked up like that, if that is how a particular balancer works.

Ususally, you plug the battery into the charger like you normally would, and then you would plug the battery's multi-pin connector into the mating port on the balancer.

If you still need explanation in the form of a picture, just ask :).

Normally, you don't use the wires that power up your speedo, those are left untouched in the charging process (normally)

Usually I see Lipo being charged through the main leads, and if balancing is done, then a balancer is hooked up to the multi-pin connector. What I do is charge to ~4.15v/cell or higher, depending upon how well the cells are balanced. Then I individually charge each cell, just to make sure that they are all well balanced. I do this manually because I don't have a balancer, and I use male JST connectors as taps.

do i have to balance cells that are in parallel or just the ones in series, like if i had a 3s2p pack would a 3s balancer work on it?

You would only balance the cells in series, unless it is 2 3s packs put in parallel. But if it is 3 groups of 2 parallel cells, that are then put in series, then it would be fine. IE, if 2 cells in parallel, they will always remain in balance with each other because they have to remain at the same voltage. The only downside is that if one cell goes bad between these 2, then the other will go down with it (this has happened to me with 2 different packs).

ok last q? now on my big truck the one right <- there i plan in building my lipo packs for it to save money. how would i go about wiring up balacing taps for it? my guess is this

What you have there is a parallel connection. You don't need balancing for a parallel connection. Here is a drawing of a 4s2p pack wired with Polyquest-type balancing leads:

here is an article about them (pcm guards)

The PCM wiring explanation can be confusing for those that don't recognize what the cells are.

Taken from Serum's link in his post (under "Metering And Balancing")...

"If you have any doubts of your ability to meter and re-balance cells then locate someone who can do it for you. "

hmmmm - how often does balancing need to be done, and what is needed to be known by a user, to go about balancing a pack??

Is there much difference in balancing nimh and lipo cells? I assume the balancer is just a plug in feature kinda similar to the PCM?
Any pics of a pack being balanced by chance? (i wasn't sure on the PCM till i saw the diagram in the linked article - so this pic couldn't hurt for explanations sake i guess? -lol-)

Sorry for all the questions - newbie needs help - at least i was on topic? -lol-

How often you should balance cells depends upon the differences between the cells themselves, and how hard the cells are pushed. You would be fine if you did it every 3 cells or so. If you have a balancer, then all you need to know is how to plug the battery into it.

You don't really "balance" NiMh cells, you more of equalize them. Besides, NiMh is done during discharge, and Lipo balancing is done at the end of a charge. The balancer would plug into the battery just like a PCM guard would.
There is nothing special that could be gained from seeing a pack being balanced, except for the flashing LEDs indicating the condition of each cell.