Max_Power

So I have a DuraTrax Ice charger and a Electrify Equinox balancer I have been using to balance and charge my aircraft lipos. I rencently got a electric car and am using 2S 5000Mah LiPos in it. I have 2 packs. I have been charging the packs one at a time with a 2s balancing adapter on the equinox and the charger set at 7.4v 5A charge. (The equinox says it can only "interface" at 3A but I've never had a problem and honestly never knew?) What I am wanting to do is wire a harness and charge both packs simultaneously.

In my mind I reason that the charge lead would have the 2 battery positives hooked together to the balancer red leads(why are there 2?) , then 2 small black bananas and 2 large black bananas each hooked to a cell ground(these packs have a 4mm red, a 4mm black, and a small bananna black in the middle...I assume 1 positive and a main neg plus the small neg as the 2nd cells balance ground?) I am figuring then I would set the charger to 14.8v(4S) and 5A charge and the balancer would just see it as 1 4S 5000Mah pack? Will this work? Safety concerns?

Is there a better way to charge my 2 packs with the equipment I have? I am mainly just thinking I would be able to get them both charged in the same time as one, and I wouldnt have to set the charger and swap packs to get ready to run my car. Is it really necessary or beneficial to be charging through the equinox each time? does anyone have a "pinout" diagram of the plug leaving the equinox? Thanks in advance. Todd

Goldenduff

What C rating for charging are your lipos? 5ampa is charging at 1C. Unless your lipos are rated higher then charging two will not be quicker because your chargers output cannot be increased.

guver

My Feedback: (325)

If I had your setup I would charge them in parallel (if they are both 2s packs) and use the equinox "on the side" so to speak. 1 balancer can easily keep up with multiple packs since it doesn't have to work. If you don't like this then ultimately they have to be wired up like http://www.scriptasylum.com/rc_speed/lipo.html shows.

ps. The two outer pins on equinox are also the main leads.

Max_Power

Goldenduff, The packs are 50c discharge, 5c charge so I'm already charging as fast as I can with the power supply and charger I have...which is only 1c. I actually figured if the ChARGER WAS SET TO 4S (14.8) AT 5A INSTEAD OF 2S AT 5A that each cell would still get 5a and charge at the 1c rate simultaneaously? I'm confused as this seems like what I am doing with the equinox already (Charging cells seperately through balancer but with the charger set at a voltage that is the sum of the cells voltage, If I were just from the positive to one neg balance lead(no balancer) I would need to set to 4.2v 5a to charge just one cell, to add a second cell tap and balancer and charge 2 together I set to 8.4v 5a , why not for 4 cells 14.8v 5a with four cell taps??)and that the equinox somehow splits the voltage into 1/4s to make 4x 4.2v5a circuits or something? I mean if I wired the packs in series I could charge at 14.8v 5a? with the same setup and charge twice as much battery in the same time right?

Goldenduff

Your charger  is the weakest link. If you are already charging at its maximum output you cannot go any faster. what is the max power output of your charger?

kahnen

Just to piggy back on what Golden is saying, to show you what he means, we use this equation.

Amps X Volts = Watts

Now we know your charger is limited to 50 watts and we know your trying to charge your batteries at 14.8v (4s lipo) so now we can find out how many amps your charger will be able to use, to do so.

50watts/ 14.8volts= 3.4 volts (rounded up)

So with 4s, your charger will only be able to charge at 3.4amps max, slower than your 5amp charge for 2s but still slightly quicker than charging both 2s lipos one after the other.

Goldenduff

Exactly. I haven't looked at the specs of the charger do I don't know it's only a 50w one but it is common....

kahnen

I had to look it up Its funny the Duratrax site doesn't list the wattage but I saw quite a few old posts (on various boards) claim it is 120w charger. So this changes everything for the OP.

14.8volts X 5amps= 74 watts

As long as you power supply, for your charger, can produce about 75+ watts you could charge them as a 4s in an hour. Since your batteries are rated for a 5c charge you could actually charge them at more amps (and short charge time) if your power supply can handle it.

Max_Power

I understand the maximum wattage thing, but My charger CAN charge a 4s at 5A so I don't really follow that the charger would not be able to charge 4 cells at 5A just because they are in different packs?

Mostly what I am looking for is how one would wire the harness to do so? Do the balance taps just attach to the series circuit of the cells between ones + and the next - ? I'm assuming the charger just puts out voltage equal to the sum of the cells together, and that when the resistance (determined by cell state of charge and differential between battery voltage and charging voltage) is equal each cell gets a equal amount of voltage across it? Does the balancer just provide additional path to closed circuit between the cells to alter the path and how much each cell sees? Does the adaptor circuit I described initially seem correct? I'll draw a diagram. I think my power supply is actually my weak link as it is rated at 3Amps(old radio shack box), but it has put out 10+amps many times with no voltage drop or blown fuses so I'm assuming if it will maintain 13.75 under the load its not stopping me? Thanks, Todd

Max_Power

is this correct as far as pin connections? The photo is how I am currently charging these packs singly. the black plug is for discharging.

trax de max

16.8V x 5 = 84W well within spec at 1C
If the lipos are more than 1C. I think its an 8A charger, then you can charge at 7A for about a 50min charge.
Charging a 4S at 7.1A will be MAX and will push the charger.
for a 120W charger you should look at 150W power supply.
You should look at 25% higher Watt for a power supply than the charger.

Max_Power

Sorry, now I'm thinking this is the way and that the cells all need to be in series to charge as 4s? Anyone know why all the balance adapters have two red wires? One at the far end and one at the pin following the number of blacks? Thanks

trax de max

i'm not sure if thats right for 2x2s as 4s

forgot the balancer can only charge at 3A, or 6A with special harness.

guver

My Feedback: (325)

I see that you are trying to take advantage of the charger's max power because you already have the current maxxed out. This a perfect idea and will work fine as long as the two packs require the same amount of charge.

ps. The two outer pins on equinox are also the main leads.

guver

My Feedback: (325)

I changed my other mind. IF the packs required the same amont of charge then I'd consider doing them at 8 amps in series using the equinox "on the side"

Max_Power

Thanks Guver...the packs are identical and bought the same time and with the same regularity/duration. The more I think about it I'm considering just leaving the balancer out of the equation and just balance charging every few times when I'm not running my truck right then and don't need to get them charged quickly. If I added the balancer to one pack while charging in series through the main leads it seems like it might slightly increase amperage through the other pack?

I'm thinking about just adding 1 double ended banana plug lead to go from + to - and charging in series. I have just figured out that if you tell the ICE that you are charging a larger than 5000mah battery it will charge as fast as 8 amps...which seeing as the batteries can charge at 5c and most of the charge time will be at a lower current because of the charger limiting voltage I think might be ok. As the charger limits voltage to 4.2 per cell anyway I don't see how it could be any more risky.

I may just make a series lead and charge simultaneously at 14.8v and 8Amps and when I'm not in a hurry either passively balance or balance charge individually at .5c to 1c. I guess if I went and blew about $75 bucks on one more battery and another charger I might not have to do this....but its just too easy to "75bucks" yourself to death in this hobby Todd

Max_Power

As far as a power supply I dont plan on changing until it starts popping fuses, smoking, or the charger tells me input voltage is insufficient. Is this wrong? I'm a "If it aint broke" kind of guy. I'm familiar with the "rules of thumb" and calculations...but I know sometimes this can be a distraction from reality and what is really sufficient. Did you know a average horse can make 14 horsepower in bursts? lol Todd

guver

My Feedback: (325)

I wouldn't use the balancer on just one pack during series charging (even if the balancer is "on the side or stand alone") If you won't balance them during series charging then this rule needs to be followed very strictly. They MUST require the same amount of charge. If you don't use these in series on the same run , same truck then series charging shouldn't be considered.

You are correct that using the balancer on only 1 pack may reduce the effective charge to that same pack. You are also correct about lieing to the charger about capacity to allow it to charge at 8 amps. As a safety precaution we can set the max % to about 63%

guver

My Feedback: (325)

I think that you and I think alike , but we are in the minority. Most users seem to never even max out their power supplies or chargers and rarely recommend others to do it either. I run all my stuff at the max. I agree with you. Run it till it gives up, YEA. That's what WOT is there for , right?

Handiman

My Feedback: (2)

The 5 amp output is a total output capacity.

Max_Power

I'm still confusecd Handiman? How is charging 2 2s packs in series more dangerous than charging 1 4s pack if we are assuming there is no balancer? Does the charger know that the 1 wire isnt inside the case? In the scenario I am suggesting the voltage is increased for the 4 cells and they are in series, so isnt the amperage still 5 amps per cell? If it is in series the current at any point in the circuit should be the same as at any other point ?Its like saying 5 gallons could be flowing out the end of a water hose but only 2 gallons leaving the spicket isnt it? How can more current flow through 1 part of the same circuit? If I were charging in parallel at 3.7 voklts the current would be divided by the number of cells but? The charger "specs" are good for 4 cells at 8 amps? The batteries are rated to 4.2 per cell at up to 25 amps. I'm not trying to dispute you, just trying to understand. Todd

GerKonig

The power source will burn ir you demand more than needed. Friend of mine bought the same one I have (25A) and then he got a really powerful i-charger. Connected the battery (5000 x 6 cell) to the charger, the charger to the power source promptly smoked the power source.

Lesson learned: If you have a 40 Amp charger, do not use a 25A power source:-) Now, if you need more "juice" you can a) connect 2 power supplies in parallel, or if the charger allows, you can connect 2 power 12V sources in series (and have 24V).

Good luck. Proceed with care, and remember you can also smoke the power source:-)

Gerry

trax de max

4s would be at 7.1A with the charger you have, Without any losses inside the charger.
I have to admit without a balancer keeping an eye on the cells i wouldn't try

pmerritt

My Feedback: (118)

Only if you charge them at the dark of night in the middle of the street so you can charge the neighbors for the fireworks display.

Handiman

My Feedback: (2)

Let me say, I didn't look up the specs on the ICE> I used 5 amps as a number. If it should be 7 so be it. I have used a ICE charger when I raced cars and trucks. I have been flying for the last 2 years and I was away from cars and trucks a year before that.