Chargers Interfering With Each Other?

[steven]

Hi, I have an 18s 4p lipo battery pack. It is split into 3 6s 4p packs, which are connected in series.

The chargers I am using are 3 UNRC-UNA9-PLUS. They charge solely through the balance wires.

When I plug one 6s4p pack into one charger, it charges fine. However, when I plug all 3 in and charge simulatenously, I get an error and the chargers stop. If you disconnect 6s4p packs so that they are not in series with each other, they charge fine.

Can anybody help identify why the chargers interfere with each other like this? Is there a simple fix - other than just disconnecting the packs from each other each time you want to charge them?

 

[amberwolf]

Chargers charging packs seriesed together must be completely electrically isolated from each other, or else you are shorting across entire packs and chargers.

You're probably powering them all from one source when you get the error.

You have to power them from completely independent sources.

 

[fechter]

Try using an ohmmeter and measure resistance from the ground pin on the AC plug to either of the output wires. If there is any reading, the outputs are not isolated. The cheap fix is to cut the ground pin off the AC plug on 2 of the 3 chargers. Also make sure the metal case of the chargers don't make contact with each other.

A better fix is to keep the ground pin but modify the circuit board to break the connection between output and ground so you can keep the safety feature of the AC ground.

If there is no continuity between the output and the AC ground pin, then you may have some other strange problem.

 

[999zip999]

I brought a una-9 plus + and then saw a kit with a battery nanny for 30usd more but the order went thru. A battery nanny can charge 8 packs but one at a time like 6s and 8 of them.

 

[knighty]

chargers have individual isolated PSUs (genuine meanwells)

they can charge away quite happy when the battery loom is removed

as soon as you put any of the packs in series they kick up an error :-(

(I'm OP's uncle)


I thought about PSU isolation... so I used a couple of car batteries to power two of the chargers... same problem :-s

all I can think of is he PWM from the chargers is a bit noisy/messy and they're messing with each other ?

 

[Alan B]

The chargers that charge via the balance wires need to periodically stop charging and measure the cells. They may get odd readings from the other chargers that are still charging and shut down.

 

[fechter]

The Meanwells are isolated and for sure separate batteries are. That's a strange problem.

It's possible there is some high frequency trash going from one charger to the next, causing a false reading. One possible solution would be to place a ferrite choke on each charger wire. The kind that snap on over the wire are the easiest to try. If you can get multiple turns through the hole, it will be more effective. Adding a capacitor across the charger output might help also.

 

[mcintyretj]

You will need to disconnect the 6s packs when charging like this with any balance charger. The positive form one charger will be directly connected to the negative charge of the joining pack through the series connection. I am not an expert, but by unplugging, you can isolate each pack.

 

[knighty]

You will need to disconnect the 6s packs when charging like this with any balance charger. The positive form one charger will be directly connected to the negative charge of the joining pack through the series connection. I am not an expert, but by unplugging, you can isolate each pack.

there's 3 x 6s to make 18s

even if I charge the 1st and last 6s pack the chargers still error out... there's 6 idle cells between the charging cells



this is melting my brain :-o

 

[999zip999]

When charging break connection between 1 and 2 and 2 and 3 . Or bulk charge and monitor. Never leave batteries connect when not in use.

 

[knighty]

problem is the bike is built around the idea of never having to take the side off to access the battery

there's a 24 pin connector on the bike wired to all the balance connectors, and then a 24 core cable to plug into the chargers (there's a few spare cores)