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Splitting a big Elcon Charger - Problems

5187 Views 38 Replies 4 Participants Last post by  kennybobby, 
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Hello all...this is not technically an "EV" problem since it's for a boat battery bank...but here we go.

I'm in the middle of upgrading the AGM batteries on my boat to LiFePO4. The bank is 32 x 180Ah CALB cells in a 24V arrangement (4P8S)...but that's less important. I'm using an Emus BMS, and ordered the Elcon to support CAN charging.

Through some miscommunication with Elcon (that I'll take the blame for initially, though communication there has not always been 100%), what I wanted was two 3000W chargers in parallel. What I got was one massive 6000W charger 220V in, 24V out, with CAN. Other mistakes were made (like Elcon omitting the CAN dongle and any manuals from the original shipment, leading to confusion on where to connect the CAN bus), but the big delay is splitting the charger.

Several reasons for the split. The primary is that the double charger doesn't fit anywhere in the boat; it could not be installed safely in that configuration. Secondarily, I don't have any 220V circuits on the boat that can handle a 6000W load, so the source power needed to be split up.

From discussions with Elcon, I concluded the best thing to do was split the Master and Slave sides, get back plates made to mount these where I'd originally planned, and rewire them. Them being in the US and me being near Brisbane and already paying for marina space with my boat disabled in the middle of this project was a factor in not shipping it back to them, which could have taken a couple of weeks (waiting in a marina at rates for a 53-foot boat...).

As configured, the two chargers had one massive welding cable each for the positive and negative outputs. The cables were split at the base, with one half of each bundle being sent to a contact on each side of the charger, paralleling them together. (see picture)

There also was an AC input on the master that was wired to the slave.

My thinking is that taking each point where the output bundles go and making them outputs for each half would be the best way. So the + out and the - out from Master and slave are disconnected from the original cables, and new output cables are run from each source. Then, I could connect them in parallel outside the two boxes and have the same effect.

The slave also required a new A/C input (and to have the leads from the Master removed) and the CAN wire needed to be cut, extended, and reconnected.

Heres's the problem. I did all that. But when I turn the chargers on, charging kicks off...then the chargers start drawing massive load OUT of the batteries and the AC power connection to the Slave gets so hot it almost melts the wires.

Also of interest, when we completely disconnected the Slave, the Master would only put out about 1/3 of the current the BMS was requesting while making an odd high pitched whine.

Elcon suggested I might "have the slave wired backward" without telling me exactly what that might mean or providing any guidance on how to have these wired properly in the first place. That, and some finger wagging about how I should have shipped the 50Kg charger back to the US so they could rewire it... With instructions could do this in an hour or two instead of spending $$$ and weeks shipping it around the world and back, but I clearly screwed something up.

Anyone have any insights on how I screwed this up? And how I can fix it?

By way of background on me, I've done a lot of 12V & 24V electrical work, but my electronics experience is pretty weak in terms of practical applications. It's quite likely I've misjudged which end of this thing the power is coming into since the function of many of the lumps of mystery on the PCB alludes me.

Thanks in advance...
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kennybobby
Good onya Mike.

That bare control board without the black coating sure would have made our past efforts easier--but if ever there were boards that needed coating, or should have had the coating, it would surely be on an ocean-going BOAT.

i'm trying to understand how the green/yellow wire could get hot enough to melt insulation or a blob of the yellow gunk on the AC capacitor near the input fuse. Is that what was smelling of heated or burnt plastic? i don't see scorching in any pictures.
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Coulomb
kennybobby said:
That bare control board without the black coating sure would have made our past efforts easier--but if ever there were boards that needed coating, or should have had the coating, it would surely be on an ocean-going BOAT.
Click to expand...
Yes, nice. But they still have the conformal coating.Interesting that it didn't help much with the tiny sparks and the wire residue.

Edit: the 2014 HQ models are also without the black gunk.
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kennybobby said:
Good onya Mike.

That bare control board without the black coating sure would have made our past efforts easier--but if ever there were boards that needed coating, or should have had the coating, it would surely be on an ocean-going BOAT.

i'm trying to understand how the green/yellow wire could get hot enough to melt insulation or a blob of the yellow gunk on the AC capacitor near the input fuse. Is that what was smelling of heated or burnt plastic? i don't see scorching in any pictures.
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The board itself didn't have scorching, but the ground wire on the first AC feed burned through. And another wire nearby got it's insulation melted by the ground, enough so I replaced it. So there was burned insulation and a small amount of what was likely smoke residue on things.
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So our claims for success may have been premature.

We had the charger running just fine...with the back off, not mounted in position.

Today, when we put the back on it and installed it, it was back to square one. Sucking power out of the batteries, heating up the AC feed line. I'm probably going to have to replace that.

Here's a screenshot of the charger status. Note the highlighted bits. I did not mistake the negative flow from the battery...it was definitely there!

Text Font Line Screenshot Technology



I'm going to take the back cover off, check all the connections for spacing.

Elcon put a big blob of silicon over the whole mess on the Master, maybe I should do something similar to prevent any movement on the Slave.
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Continuity check with the cover on and the charger disconnected from everything shows a direct connection from the Positive output to the case, and to the AC ground wire.

Am I right in thinking when this thing connects to the battery the whole thing is maybe closing a completely inapproproprayte 24V circuit?

This could explain both the rapid wire heating - it is AC wire, 2.5mm^2 an d OK for 22A @ 240V, but it's seeing 140+ Amps - and the lack of a breaker throw from the 16A breaker on the 240 panel.

Taking the cover off now, now we may have some idea what we're looking for.
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bj_porter said:
Continuity check with the cover on and the charger disconnected from everything shows a direct connection from the Positive output to the case, and to the AC groud wire.

Am I right in thinking when this thing connects to the battery the whole thing is maybe closing a completely inapproproprayte 24V circuit?

This could explain both the rapid wire heating - it is AC wire, 2.5mm^2 an d OK for 22A @ 240V, but it's seeing 140+ Amps - and the lack of a breaker throw from the 16A breaker on the 240 panel.

Taking the cover off now, now we may have some idea what we're looking for.
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You take the cover off...problem goes away.

But there are a couple of things near the positive connector that, if shorted to, nicely complete the connection to groud from the positive output.

So we move the wires...put more electrical top on them, just in case, and are trying again. This time we will test (+) output short to ground BEFORE we turn it on again...
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kennybobby
How about a cover screw right above the Red +ve welding cable gland nut--maybe screw is cutting
into the cable and shorting to chassis?

Have you narrowed it down to the Slave pair?

Pull the cable and inspect underneath these marked areas--maybe the sharp edges have cut into the cable and short when
the cover presses on it. i would try to re-route it, it's too big anyway considering the size of the jumper wires.
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Coulomb
bj_porter said:
Continuity check with the cover on and the charger disconnected from everything shows a direct connection from the Positive output to the case, and to the AC ground wire.

Am I right in thinking when this thing connects to the battery the whole thing is maybe closing a completely inapproproprayte 24V circuit?

This could explain ...
Click to expand...
Yes! it could explain a lot of things. Like how the earth lead could overheat, yet not trip the RCD. Answer: because it's carrying DC, from the battery. There must be some resistance in the circuit somewhere, or the fault current would be well over 1000 A. Perhaps that's why my brain resisted that thought; battery faults are usually more shower of sparks than silent overheating.

Edit: I'm also used to solar energy circuits or EVs, which usually have fully floating batteries. But in a boat, you might ground the negative side of the battery. Is that the case? I'm guessing it must be, to explain this problem.
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kennybobby said:
How about a cover screw right above the Red +ve welding cable gland nut--maybe screw is cutting
into the cable and shorting to chassis?

Have you narrowed it down to the Slave pair?

Pull the cable and inspect underneath these marked areas--maybe the sharp edges have cut into the cable and short when
the cover presses on it. i would try to re-route it, it's too big anyway considering the size of the jumper wires.
Click to expand...
We re-routed that wire, seems to have sorted the problem.

That wire is OEM from Elcon, half of a big weldinbg cable. It is butt spliced to a 35mm2 tinned marine wire. Which gets warm to the touch when pushing 80A combined out of the chargers...
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Coulomb said:
Yes! it could explain a lot of things. Like how the earth lead could overheat, yet not trip the RCD. Answer: because it's carrying DC, from the battery. There must be some resistance in the circuit somewhere, or the fault current would be well over 1000 A. Perhaps that's why my brain resisted that thought; battery faults are usually more shower of sparks than silent overheating.

Edit: I'm also used to solar energy circuits or EVs, which usually have fully floating batteries. But in a boat, you might ground the negative side of the battery. Is that the case? I'm guessing it must be, to explain this problem.
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Grounding can be a little weird in boats, since we're not actually on the physical ground. It's not like you can drive a big spike into the literal ground like if you're grounding a big HF antenna.

Often there is a common ground bus, somethings this is run to a through-hull "Dynaplate" to get electrical conductivity to provide grounding.
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bj_porter said:
Grounding can be a little weird in boats, since we're not actually on the physical ground. It's not like you can drive a big spike into the literal ground like if you're grounding a big HF antenna.
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Yes, I chose the wrong word. I mean do you use the hull to conduct 24 V to lower current devices like lights?

Or more directly, do you deliberately connect battery negative (or positive or whatever) to the hull?
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Coulomb said:
Yes, I chose the wrong word. I mean do you use the hull to conduct 24 V to lower current devices like lights?

Or more directly, do you deliberately connect battery negative (or positive or whatever) to the hull?
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The hull? No. It's fiberglass. You can't use it like the frame of a car.

There's a negative bus, which is genenally connected to some sort of ground plane or Dynaplate. Negative wiring in circuits will hit this.
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This process has been both weird and educational.

I'm frankly amazed that I didn't destroy any of this hardware.

Though it's possible I did bake one of the four boards, somehow, as we seem to be only getting about 82-83A out when the BMS is set to ask for 100A.

These are CALB 180 cells, and can charge at C, so there shouldn't be an issue with charge acceptance.
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This process has been both weird and educational.

I'm frankly amazed that I didn't destroy any of this hardware.

Though it's possible I did bake one of the four boards, somehow, as we seem to be only getting about 82-83A out when the BMS is set to ask for 100A.

These are CALB 180 cells, and can charge at C, so there shouldn't be an issue with charge acceptance.

EDIT TO ADD:

It's putting out about 90A set at 100A.
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bj_porter said:
I'm frankly amazed that I didn't destroy any of this hardware.
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Agreed! That's at least 3 bullets that you've dodged, BJ!

These are CALB 180 cells, and can charge at C, so there shouldn't be an issue with charge acceptance.
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That's not the issue. The issue is getting thick enough cables so when the charger is putting out 90+ amps, the voltage measurement at the charger end isn't such that it appears that the batteries are full.

It's putting out about 90A set at 100A.
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90% of requested amps isn't too bad considering the high currents and low voltage.

BTW, on one of your screenshots, I saw that the target voltage was 29.6 V. That's 3.7 VPC. CALB recommends a maximum of 3.60 VPC, or 28.8 VPC. Other manufacturers say you can go to perhaps 4.0 VPC, but there isn't much capacity above 3.5 VPC, so I'd limit it to 28.8 V. However, the lower voltage might mean the charger cuts back too quickly at high charge currents due to the inevitable voltage drops, so you might have to leave it at 29.6 V and terminate the charge a little early, or change to 28.8 V when the current starts tapering off (say when it falls to 50 A). It would be great if you can get that to happen automatically. Watching batteries charge isn't much fun after a while. This is only an issue because of the very high charge current and low battery voltage.
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kennybobby
Good catch on the overvoltage, that will damage cells. The damage manifest as swollen cells that won't hold a charge.

That's what initially got me involved in reverse engineering these chargers, Paul had a cell in his Celica pack get damaged by the over charging and wanted to figure out how to change the voltage.

From subsequent research and testing we found that the resting voltage of a full cell is only 3.33 volts. There is no useful meaningful energy above that point as the voltage will drop immediately to that level when loaded. The risk of damage by charging to a higher voltage is not worth it.
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Coulomb said:
Agreed! That's at least 3 bullets that you've dodged, BJ!


That's not the issue. The issue is getting thick enough cables so when the charger is putting out 90+ amps, the voltage measurement at the charger end isn't such that it appears that the batteries are full.


90% of requested amps isn't too bad considering the high currents and low voltage.

BTW, on one of your screenshots, I saw that the target voltage was 29.6 V. That's 3.7 VPC. CALB recommends a maximum of 3.60 VPC, or 28.8 VPC. Other manufacturers say you can go to perhaps 4.0 VPC, but there isn't much capacity above 3.5 VPC, so I'd limit it to 28.8 V. However, the lower voltage might mean the charger cuts back too quickly at high charge currents due to the inevitable voltage drops, so you might have to leave it at 29.6 V and terminate the charge a little early, or change to 28.8 V when the current starts tapering off (say when it falls to 50 A). It would be great if you can get that to happen automatically. Watching batteries charge isn't much fun after a while. This is only an issue because of the very high charge current and low battery voltage.
Click to expand...
Yeah, after running through a full charge cycle today, we decided that in spite of those cables being rated for carrying that much voltage, they still needed to be bigger. So we're going to use the 1/0 (equivalent to about 50mm2) as the charger out cables, and put a 75mm2 cable on after the fuse.

The max charge voltage is set to 3.6V/cell, though I think the BMS will request more since you need a voltage differnential. But it stops charging at 3.60 as it is set now. At 3.5 it begins the Balancing cycle and starts tapering voltage & amperage.

3.70 volts currently triggers a High Voltage error and immediately cuts off the charge contactor.
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J
3.45V is my recommended max for LFP longevity. But that's for gentler House bank storage, not propulsion.

I don't think pushing higher up the "shoulder" of the voltage curve really buys much greater AH capacity, but it definitely costs many lifecycles off the back end.
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kennybobby
+1 on John
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