Help with 4S (x2) Charger option

[mjp8081]

So I'm ordering my charger and batteries (2x 4S) for my 8S dual eMTB

I'm going to wire the 2- 4Ss together, is it possible to just get a 4S charger and charge/balance them separately? Or is there something I haven't considered

The 4S chargers are pretty cheap and small, what if I get 2 of them, one for each battery?

Is there any reason why I would have to use an 8S charger for this 2x 4S setup?

I'm not concerned about how fast the batteries charge.

 

[torqueboards]

Yes, you can use a 4S charger and even charge in parallel using a parallel charging board for your end connectors.

Usually cheap, small 4S chargers charge at a slow amp rating and won't charge fast. Your looking at a few hours and if you plan on charging with a cheap charger.

You can charge at 8S but your setup would need to be in series.

 

[sl33py]

Just about any Lipo charger should do 4s. You will need a Lipo charger obviously.

The higher amp lipo chargers typically are DC only. So besides the cost of the charger, you need a DC power supply.

HK has a decent 540w (variable voltage 13-18v, 30A for ~$70:
http://www.hobbyking.com/hobbyking/store/__21857__HobbyKing_540w_100_120v_Power_Supply_13_8v_18v_30amp_US_Warehouse_.html

Paired with a HK Turnigy DC Charger (i think an iCharger clone) like this ~$47:
http://www.hobbyking.com/hobbyking/store/__56924__Turnigy_Reaktor_300W_20A_6S_Balance_Charger_US_Warehouse_.html

OR you can get some AC/DC Lipo chargers, but almost always lower Amp (slower).

HK Imax B6 ~$45:
http://www.hobbyking.com/hobbyking/store/__58285__IMAX_B6AC_V2_Professional_Balance_Charger_Discharger.html

HK x200 (10A) ~$100:
http://www.hobbyking.com/hobbyking/store/__53601__HobbyKing_8482_X200_AC_DC_Touch_Screen_Smart_Battery_Charger_10A_6S_US_Plug_.html

Recommend a parallel balance board like this:

Tons of options for what battery connectors you use, and what balance plug.
http://www.buddyrc.com/power-system/paraboard-parallel-charge-board.html

So what is the difference in speed to charge?

If you have the "typical" 4s 5000mAh, you can charge it at a maximum of "x" C. This will be noted on the battery or in the info on the page.

Example Zippy Flightmax 4s 5000mAh (30-40c discharge):
Capacity(mAh) 5000
Config (s) 4
Discharge (c) 30
Weight (g) 526
Max Charge Rate (C) 2
Length-A(mm) 149
Height-B(mm) 51
Width-C(mm) 37

So finally (sorry to be long winded) - why does it matter if you charge it individually, in parallel or at a higher C?
That cell at 1C (a good rule of thumb for battery life if you can be patient), will take 1.2 hours. So individually you are 2.4 hours charge time to charge both and ride again.

Both charged in parallel would cut your charge time in half (down to 1.2 hours from 2.4) @ 1C. (need a parallel balance board (please always balance charge!))
Both charged at max C (2 C for these particular - i have some that will do 5 C) would cut it to .6 hours!

Now imagine you have 4 batteries. 4.8 hours (individually charged) vs .6 (all in parallel at 2 C). BUT as you add more batteries and higher C, it's more Amps - the small AC/DC charger might quickly not be able to charge at that C. You get spoiled and faster is nice (less battery life risk vs "i want to ride now").

There's a calculator I use to see speed to charge at a given rate - http://www.csgnetwork.com/batterychgcalc.html

I hope this helps. If i goofed and one of the guys truly in the know wants to correct me i definitely defer to them. I'm no EE.

GL!

 

[torqueboards]

Icharger 208b is $120
350w power supply $40
550w power supply $60

Charge at 20 amps max.
Great affordable setup.

I can charge any 2, 3, 6 packs at 15amps and finish in 30-45 mins.

 

[sl33py]

Icharger 208b is $120
350w power supply $40
550w power supply $60

Charge at 20 amps max.
Great affordable setup.

I can charge any 2, 3, 6 packs at 15amps and finish in 30-45 mins.

Nice setup Dexter! Do you use a balance board w/ yours?

Also, anyone who has access to older HP and Dell servers - their power supplies (modular/swappable) make GREAT DC Power supplies (12v only). Going to try that next, a pair of them and possibly in series for 24v. Loud fans, but basically free from work!! If you are willing to tinker a bit. Cool writeup on this - http://www.tjinguytech.com/my-projects/server-ps

HTH - GL!

 

[torqueboards]

Yeah, usually charge 2 or 3 sets at a time. Balance charge them all.

 

[mjp8081]

Thanks for all the replies

So I could leave the 2 4S batteries wired in series and still charge them individually?

These little chargers (below) are so small, I was thinking I could mount 2 of them on the board and share a power supply between them (one split plug-in wire for charging both batteries)
Is it a big deal that there is no readout?

http://www.hobbyking.com/hobbyking/store/__26492__HobbyKing_8482_E4_Balance_Charger_US_Warehouse_.html

So would I need that paraboard?

How does this look:

 

[sl33py]

Hmm... That looks a bit sketchy to me. But i tend to *way* overbuild stuff, so...

Looking at your layout pic, i don't see your connection into the batteries. Not sure about in series (as 8s) charging. I think it should work fine, but a bit out of my realm.

I would want a lighter board and not have my charger get damaged (impact, dirt, water, moisture, etc.). Remember Lipo's are high energy items, and when not charged correctly (by this important charger) it can go horribly wrong (google lipo charging fire). Not something i worry about too much with reasonable precautions, but i wouldn't trust a relatively "dumb" box charger like this - especially if it were on my board taking who knows what kind of abuse.

I would get a paraboard (or a clone), and a decent charger. At least one of the nicer HK clones. There are other things some of them do that is worth knowing. Internal Resistance is one of my favorites to guage the "health" of my batteries and basically tell me when it's time to throw/replace.

I think an AC/DC charger should be the minimum, but if you get more packs and/or higher charging packs (more than 1-2C) - you will quickly wish your charger could do more than 5-10A. IMO.

What batteries do you have currently specifically? How many?

GL!

 

[mjp8081]

What about compared to this one, with readout:

http://www.hobbyking.com/hobbyking/...S_Balance_Charger_Cell_Checker_30w_2s_4s.html

Planning on ordering 2x ZIPPY Flightmax 4000mAh 4S1P 45C, unless there is something incompatible about these.
http://www.hobbyking.com/hobbyking/...Flightmax_4000mAh_4S1P_45C_US_Warehouse_.html

My theory was it would be nice to just insert one plug to charge the board up, rather than 2 power cables and a multi-wire balancer plug for each battery (6 total) when I need to power the board up (if I understand the normal process correctly). That seems like a lot of fussing around.

 

[fechter]

One thing to consider is the two packs would need to be separated before charging. If not, the common source supply will create a short (smoke). You could charge both at the same time while still connected if both chargers were completely isolated from each other.

 

[mjp8081]

One thing to consider is the two packs would need to be separated before charging. If not, the common source supply will create a short (smoke). You could charge both at the same time while still connected if both chargers were completely isolated from each other.

If I understand your advice, I think thats what I got. I may be unclear as to what I can leave connected to the battery whether it's being charged or being used to power the motors. My plan assumes that you can leave a 4S charger/balancer connected while riding/powering motors.

One interesting thing about the above HK DC-4S is that it seems to be lacking the banana sized pos/neg batt connectors, and says it charges and balances through the smaller wire bundle balancer plug--could that be right?

 

[torqueboards]

Personally, I wouldn't bother with all those on-board methods of charging. For the avg joe that adds a ton of complication plus ridiculously slow charging is annoying.

Those cheaper chargers quality control is also a lot less since it's a cheaper product. Which ultimately means it has a higher failure rate than something like an iCharger which is at a medium price range but a higher quality charger.

As sleepy mentioned - I prefer to spend the money in the beginning and not have to spend money again. You can save a few bucks but in the long run -- your going to end up getting the iCharger anyways because yours just broke.

I'd rather take the 5 seconds to remove my pack and charge in parallel also versus dealing with on-board charging and charging at 2-4amps versus 15amps.

 

[sl33py]

It's your call man. I think it's a bad idea to have even a cheap charger like that on your board permanently.

Your battery x 2 = 986g
A similar 8s battery - http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21426
single battery = 911g

You need a beefier/more-complex charger for 8s.
$139 - http://www.hobbypartz.com/75p-1030-charger.html
Still would need a decent dc power (even your smaller one does)

If you want convenience - look at a real BMS (battery management system). They are SLOW, but like you want - convenient. Usually a single plug.

Another great idea i've seen some builders do - put the balance plug and power plug on the exterior of the battery enclosure. Look at ADS setup - there is a Deans plug for power, and the balance plug. MUCH cleaner, and can still likely swap batteries inside the case.

Also, that 4000mAh battery will take 3.2 hours to charge at 1500mA. That might be ok, but seems slow to me.

I'd probably also look at some of the similar size/weight batteries that will do 5C charging. But only if you are going to use a more typical/dedicated charger like an iCharger or similar. Would be wasted if you use BMS or similar (Unless cheaper, lighter, smaller, etc. as a primary reason).

I'm not sure how you can overcome the in-series charging piece like Torque mentioned. Letting out the magic smoke is usually BAD.

GL!

 

[mccloed]

I used to use two of these for two 4s batteries. http://www.tenergy.com/01267

 

[markz]

I was where you were at; so do not be cheap on charging method(s).
I just found that adj. Vout 13.8v~18v DC HK 540W on my own, at 30A its decent for bulk charging. Its very quick. Plus for me there Im only using 500W total.
Plus if you buy the iCharger 208B you get a double packed "Whammy" (a good thing) 350W 20A for balance charging.
Which means you can balance charge 4 batteries at once (I think)
Saves time.

So for my calculations on my 4S hardcases 5Ah Turnigy. I can rock out 6 batteries in an hour up to 4.15V/cell on 540W PSU.

I am sitting here now, with a 150W 7A charger, with a 105W 7A psu, parallel board charging four 4S batteries at 6.5A. Seems like its taking total just over an hour.
Already went through one round of charge. (Cutoff set at 5000mAh)

My normal pack is going to be eight 4S batteries at 66.4V total for 16S at 10Ah.

This is a good thread, I learned alot. Liked the battery calculator.

However I am still pondering EM3ev's Al. Charger, they do not quite fit my voltage, closest is a switched 17S 4A puts it at 71.4V, 69.7V and 64.6V.
Or BMS Battery has a 900W, at 60V12A, 72V10A, 84V9A. So my needs dont quite fit. Hearing horror stories of people trying to adjust them. Plus thats an "iffy" company.

 

[torqueboards]

iCharger all the way!!! Don't waste money on a cheap charger. You'll end up paying for it later on.

iCharger is only $120 + $60 for a HK 350W Power Supply.

I'd like a PowerLab 6 or PowerLab 8 but that's a bit overcharged.