Easy way to monitor and deal with 4s packs?

They're cheap, but seems like a bit of a pain to deal with. For example, I could happily monitor 18s from 6s packs with three cell logs and just some jst parallel harnesses.

But how do you do this with 4s packs? Is there a pre-made solution or is it something I have to make? Ideally I'd like to be able to use my cell-logs efficiently and watch 8s per cell-log. (yes I've done the even drain mod)

Basically need these! http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9910

These are cheap though http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9737

and these 8s pigtails are cheap too http://www.progressiverc.com/8s-jst-xh-pigtail.html

probably be super easy to do it yourself

Well, cellogs are 8s, and so are the mid range chargers. Splice em up into 10 ah 8s packs. Then put em on Icecube style wiring harnesses. Run 8s, 16s , 24s, then charge as 8s. if you want 18s, then you'd have to use a couple 2s packs to get there. It would still be 3 cellogs to monitor. But then charging couldn't go all at once on one charger, with some packs 8s and one 2s in the thing.

If you really want 18s, then 6s packs make the most sense to me, even if a tad more pricy. 20s would work by making up 4s 10 ah packs, then putting adapters on the balance wires to give em an 8s plug. Still just three cellogs, but you'd make your charging harness for 4s, then charge all on one charger.

You seem to be knowing what you're doing. Then it's better not to mess with serial parallel connections all the time, keep it simple and purchase a bulk charger for daily duties. The ones from BMSBattery are adjustable and cheap. I've always got into trouble reconfiguring stuff too often, ultimately making a bad connection with mighty sparks and vanishing bullet plugs. Lipo is very good at keeping balance for many charges without too much attention. Just make sure you watch the lowest and highest cell rows in the string. You will soon learn which of them to keep an eye on. One buzzer for discharge, and one celllog with relay for charge is as much as I've ever needed in 3000 miles on lipo. The cells will not change their behavior rapidly, and if they do for some odd reason (e.g. physical damage), it's likely too late to do anything anyway.

If you want a custom harness for 4S packs and 8S celllogs and buzzers, It's not so hard to make with a cheap iron and shrink tube. There are guys on ES like Wojtek who can make you one too.

Just taping 2 battery together connecting and inserting balance wires in to 8s male plug donor. I mean taking out every cable out of original 4s connector and inserting in corresponding 8s male connector (removing all original connectors) place. 1 cable will be spare, like cut of and isolate candidate.

Actually - I think there was some issue with running 8s lipo with cell logs that have the even mod done to them IIRC. I'll have to check.

Yes, it unevenly drains cells 7 and 8 (drains less than from 1-6), so you need to do simple mod to even it out.

Have mentioned few times here, every monitoring system I know (I only know about 6, all from HK) will desballance your packs, if connected permanently. Better results on short connecting to know what is going on from time to time. Was kind of scary to balance every 2 days, now no monitoring and over 20 cycles in balance.

Sure, if you leave em plugged in all the time.

I find that if my dod is kept reasonable, and I know I have reasonably good packs, all I need while riding is the CA. Once in a while, or after a known deeper discharge, I'll check my packs individually with a cellog to make sure nothing went crazy low.

If you need to do a 100% discharge, then you attach your monitoring device of choice for that particular ride.

dogman said:

Sure, if you leave em plugged in all the time.

I find that if my dod is kept reasonable, and I know I have reasonably good packs, all I need while riding is the CA. Once in a while, or after a known deeper discharge, I'll check my packs individually with a cellog to make sure nothing went crazy low.

If you need to do a 100% discharge, then you attach your monitoring device of choice for that particular ride.

Click to expand...

Pretty much my way too. I still use the cheapo old buzzer boards you demo'd over a year ago when going for long unknown rides. Too much worry leaving active electronics on Lipo for extended periods of time.

I've decided against monitoring individual cell voltages during riding. It caused too many issues, and my cells definitely stay in better balance without them.
Basically, check the balance before you go on a long ride. So long as the cells are close to balanced before you leave, they should be fine. More cells in parallel also helps out, since the more you have, the less total capacity a single cell makes up.

If I get home from a long ride, and my pack voltage is low, I usually check the balance before bulk charging. I haven't balance charged in 10-20 cycles and the cells are within .05V, which is fine when I only charge to 4.1 and discharge to 3.65...

Is there any reasonably priced 12s chargers?
For $130 I could get 6 4s 5000mah hardcases and pull apart packs and reconfigure into 1 12s 10Ah brick..
(I would use this on my commuter bike as a "backup pack" for if the need ever arises - That way, if both of my lifepo4's got drained, I could just plug in the lipo pack and (maybe) use up to 7ah of it)..
Then balance charge every other time I would use it.. (probably twice a month or so).
(this would also eliminate the need to carry any lipo charging equipment with me).

Exactly, stop fretting, discharge to less than 100% as shown on whole pack voltage. If you do an 80% discharge and find a cell in a pack that is 1v lower than the others, then toss that one and buy another.

Worry about where to ride next, not whether your battery is lasting x number cycles, or is out of balance .01v.

On my dirt bike pack, one cell of one paralell paired set is lazy and won't fully charge. So what? It's been that way about 30 cycles now, and still only goes to 3.5v when all the other cells are at 3.8. Sure, I keep an eye on that pack now every couple cycles, but I sure don't try to get it to balance. Why bother? Just gonna wring a few more cycles out of it, and then dissect the good cells out of the pack when it won't charge to 4.1v anymore. That pack is not paralelled at cell level to the other, so the runt cell can just die when it feels like it. It's not dragging down the other pack any. But meanwhile, it's not shortening my range much, and not breaking the three rules, so it's still usable even if it is permanently out of balance.

Re the charger question above. Rig a wiring harness like this, http://endless-sphere.com/forums/viewtopic.php?f=4&t=32096 for 12s discharge, 4s charge. Then all you need is a reasonably priced 6s charger to fast charge the whole pack at 4s.

After testing this rig, I went and bought a bunch of bullets so I can put more of my lipo back from andersons to bullets that fit this harness.

And now I want another one, to do 20s. It's super easy to manage the packs with these adapters. Once a month or so, you pull out and balance only the packs that need it.

Well - I just ordered 10x 4s5ah hardcase packs (for only $240!!) - I'm either going to have a 20s10ah pack or use the two 6s packs I have to make a 22s10ah pack (16s + 6s). Leaning towards the 22s just because I can. Also, the 4s packs are awkward in my battery box. I'm hoping to disassemble the two spares hard case packs I ordered and see how much room the case takes up. Since the batteries are always safely in my box, I don't have to worry so much. If I'm right, I think I should be able to fit 24 of the 4s packs once the hard case is removed! That's 24s20ah or almost 2kwh! Awesome.

WRT to watching the packs. I'm starting to agree that constant babying and watching is unnecessary once you get a feel for them. However, I've found a small 4p relay which would make switching off and on the cell logs very simple. Also, instead of cell logs I'm considering using those tiny 6s $2 lipo monitors. No alarm, but then as long as the packs are in balance....

WRT to balancing it's a bit trickier - I can't balance the packs with an RC charger without opening the case - which is something I want to minimize. This is because my imax charger doesn't balance well when it's done through the balance harness (voltage drop) so I'd have to run 5 sets of balance and power wires out of the box. As of now I planned to have balance cables accessible without opening the box. I just ordered a Trakker watt meter and balancer (hobby king was sold out of battery medics) - I'll be using that to do my monthly balance.

So I still have to find a cheap easy way to parallel the 4s packs. Progressive sells the parallel harnesses... for $8 a pop... x4 is $40 after shipping
The idea of cutting, stripping, and soldering together 20 wires per 4s group using the extension leads doesn't much appeal to me.

You're likely quite lucky that HK had no medics in stock. The recent two medics I bought there were less that accurate to be usable for balancing. For the same price you can buy a complete charger that will do a better job of balancing and it can charge too.

I had a cool idea

Solder 2x 4s leads to these $4 lipo meters / alarms - sure they're probably not accurate, but I can set them at 3.5v or something reasonably high. Then break the connection to the negative pins with a relay to turn them off. This way I can monitor up to 24s for the cost of one cell log instead of three.

This way I can still unplug the individual 4s groups to balance.

these pre-tinned balance leads look easier to work with and cheap too http://www.ebay.com/itm/320669295732?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

So... I was pricing custom made PCBs.... and I could totally have boards made to make putting 4s packs in parallel easy as cake. And they'd be cheap too. Like 1/4 the price of buying the parallel harnesses.

Boards would be modular. From 4s up to 24s. Up to 6 packs in parallel. I would drop the headers and harness in myself. So everything would be ready to go! Anyone interested?

I was thinking of this.. Cut the 4s JST down into a 2s, then solder on another 2s jst. So you have two 2s on each 4s pack. Now you can use the little $4.50 2s balance chargers. Charge to 90% with a power supply and let the little buggers take care of the topping off.. or just use them alone if you have the time.

vanilla ice said:

I was thinking of this.. Cut the 4s JST down into a 2s, then solder on another 2s jst. So you have two 2s on each 4s pack. Now you can use the little $4.50 2s balance chargers. Charge to 90% with a power supply and let the little buggers take care of the topping off.. or just use them alone if you have the time.

Click to expand...

Careful. Have one of the little buggers, it charges to 4.23/cell. Maybe it is defect, just be careful!

So I ordered what I thought were 4s jst-xh pig tails off ebay.... but they were instead just mini connectors for a charger. Well shit. So then I just ordered some of the real deal from digikiey and used the colored wires that came with the ebay pigtails.



These will go to the parallel boards I'm making on one end and to cell-logs/cheapy ebay cell monitors. Another thought is that instead of using a battery medic to balance, I can just use the imax at 8s. This might be the plan until I get the main bulk charger up and cranking.

These weren't as bad as I thought to do with needle nose. I pre-tinned them first, crimped, and then heated up the pre-tinned wire with solder to make a good connection. Pretty much exactly the same method as with the jst-sm I wrote a faq for.