[bj_porter]

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...

 

[bj_porter]

Yes, agreed. If you keep with 24 V chargers, you'll need two separate chargers for each half of the pack. One half could be at a different voltage than the others, so I don't think it would work all that well having only one master.

According to Elcon, with the CAN wiring the way it is, splitting the two halves this way won't affect the master/slave relationship. It's basically 4x 1.5 kW units all paralleled together. Whether the halves are screwed together is not supposed to be relevant, so long as the wiring is right.

You're likely not going to be able to copy the firmware from the master to one of the slaves.

You say you're in Brisbane, but I assume that's not Brisbane Australia (there are a couple of Brisbanes in the USA, I believe).

I'm at Gold Coast City Marina, in Coomera...so yes, it's Brisbane, QLD. It's the only Brisbane I've been too, though I sailed here from the East Coast of the US.

Yes, that's confusing, if you bought them recently. Maybe Elcon don't sell many 6 kW models? The three white opto couplers strongly suggests a pre-2014 manufacture.

It was ordered and built in June 2017.


I have only a little experience with larger chargers; mainly a dual unit (2 x 2.5 kW).


I would think that this would have blown the DC fuse. It's rather confusing as to what has happened. Are you running the charger from 240 VAC or 120 VAC? Elcon seem to have firmware that runs the chargers hard at 120 VAC. It could be that the wiring isn't heavy enough for 6 kW at 120 VAC (that would be over 50 A total, 12.5 A through each charger unit. But they are supposed to be derated when run at 120 VAC.

220V AC/50Hz. The 220V wiring is pretty beefy that they included, however, they wired the whole 6kW thing with one A/C feed, which I can't use. I replaced one A/C circuit with 2.5mm2 marine grade tinned wire which is rated for 21A; each unit should produce max 13A or so, which should be able to run for hours without having a problem. However, the slave AC feet would have melted in minutes if I didn't turn it off, though the breaker should have prevented that.

The AC wires to the slave getting hot seems to be an overcurrent condition, such as the diode bridge is shorted, but there is a fuse on the mains that should blow.
There is a 16A breaker on the circuit, yes.

One thing i noticed is no green ground wire running to the 4th unit to the far right in the photo? For that matter, why are the grounds not connected to the input AC Ground wire and why is that wire so tiny--it should be the same size as the input at least?

It confused me too, the ground. The ground came to the 1.5Kw unit that had the power input in the master, but did NOT run to the one on top. But ta ground ran to the slave.

Is the photo the "before" picture of how it was rec'd from the vendor, or is it showing wiring changes that you made?
That's as it came from the manufacturer. I've got to pull them back out and disassemble for after pictures. I've got to do that anyway...but we didn't today because they get under foot.

How/where are you getting your 240vac--is it a generator on board, or do you connect a land line to the mains?
Both are a possibility, but in general our main source of power is a 7kW 240V/50Hz diesel generator. In the rare instances we're at a dock, we would probably charge before we left from shore power.

Nice looking boat, funny blog: could you not use the B-word for one hour...

[/QUOTE]

She's a Swedish boat, built in Europe though we bought her in America. That's why she has 240V/50Hz for mains power. Though I also have a 110V inverter, 24V house, and 12V house and start battery banks. 24V is a good choice at this size since the wiring is so much smaller. Though it's sometimes a pain in the neck to finad devices like pumps and the like in the right voltages.

 

[bj_porter]

The picture is not clear enough to read the printing on the boards or trace the wiring, but it looks like you have 4 1.5kW chargers ganged together. So i'm thinking that there would be one master and 3 slave units to make up the 6kW unit. And if you want to split them, then one of the slaves must be configured into another master.
They look like the older boards for which we have schematics, http://www.diyelectriccar.com/forums/showthread.php?t=89470,

From what Elcon is telling me, this is not the case. As long as I get the communications wiring right (which is hard to screw up) they can stay as one charger unit and no secnd master is needed. Though I'd be just as happy with two independent chargers and two CAN dongles - my BMS can handle it and I prefer the flexibility for low power situations.


But our resident expert on these chargers is "Coulomb" from Brisbane, and he has more experience with those big monster chargers. Which marina are you located?

If you wired up the slave outputs backwards, i.e. with reversed polarity, then when the output relays were commanded closed by the master, the slaves would be drawing power from the cells thru the inductors and the final stage rectifier diodes.
To the best of my knowledge the poles are not reversed. Each output is marked with a "+" or "-" on the PCB near the pole, and I took the oringal wires off and reconnected at the same poles.

The AC wires to the slave getting hot seems to be an overcurrent condition, such as the diode bridge is shorted, but there is a fuse on the mains that should blow.

One thing i noticed is no green ground wire running to the 4th unit to the far right in the photo? For that matter, why are the grounds not connected to the input AC Ground wire and why is that wire so tiny--it should be the same size as the input at least?

Is the photo the "before" picture of how it was rec'd from the vendor, or is it showing wiring changes that you made?

How/where are you getting your 240vac--is it a generator on board, or do you connect a land line to the mains?

Nice looking boat, funny blog: could you not use the B-word for one hour...

Batteries on the brain these days...this project is taking WAY too long, though this is really the last piece of the puzzle.

Outside of tricking the Emus BMS into letting my non-CAN charge sources also work (Alternator, wind generator, solar) but that's another problem entirely and much less important...

 

[bj_porter]

A post-final thought


Sigh. When I read 6000 W and 32 cells, I immediately assumed 48 V. The inductors, which change appearance with voltage, look exactly like the 48 V charger I have here at the moment. Even when you said 8S, I was still thinking 24 V. Even when you said you received a 24 V charger, it still didn't click. I assumed the voltage mismatch was just part of the mix-up with ordering, and that you'd be wiring 3000 W of charger on one half of the pack, and the other 3000 W to the other half (splitting that in two so that you could charge at a lower rate than 6000 W total). Sorry for the bonehead confusion!

So all that stuff about the outputs not being isolated... it is now irrelevant, and can't be the cause of your problem.

It's even more mysterious what the actual problem could be though.

It would probably be less mysterious if I took pictures of what I did now. Or, if you wanted to come down and have a look...

Either way I'll yank them off tomorrow AM and take better pictures. I'm not likely to hear anything back from Elcon until Tuesday at the earliest, so any poking and prodding we can do in advance of that which doesn't set fire to the boat may solve the problem earlier.

 

[bj_porter]

I think that they assume that the case will conduct the ground to the other PCB. In this case, with separate halves of the charger, I'd use a green/yellow or pure green wire to the other chassis.

Is it a poor practice? It's arguable. Certainly a cheap one.

I need to put the two halves on completely separate circuits since I don't have any 220V wiring suited for taking 6000W of power all at once. So I replicated the setup of the master on the slave with a new 220V input wire on a separate circuit on a 16A breaker, with the ground wire NOT running to the other unit.

I can't see the harm in running the wire though. Wires...I have lots of.

 

[bj_porter]

Some pictures...this is the whole slave. One side is positive & negative out, the other wires are the A/C in and the CAN control wires.

Slave Positive out...

Slave negative out.

How they will get installed. The red Positive outs get connected to the same source behind a 200A fuse, the red Negative outs go to the common ground for the 24V system. The A/C input goes to a dedicated circuit with a 16A breaker.

 

[bj_porter]

Here is the master...

 

[bj_porter]

Huge....HUGE thanks to Coulomb for making the trek down to GCCM todat to help get us sorted.

The good news...it worked. We ramped it up to 100A of 24V charging (highest practical limit on 15A shore power) and there was no smoke heat or drama.

The bad news...we didn't find anything, specifically, that I'd screwed up.

There was some crap on one of the slave's boards from the first 220A feed power that we let the smoke out of. It was too small... The crud was making sparkly noises and needed to be removed.

So he cleaned that off. We moved one wire, which may make things more optimal, but didn't really change things electrically. And we tightend down the AC feeds to the slave.

So it may have been loose or mis-connection.

We also solved the problem of the "Singing Ferrites".

The master was making a weird, high pitched and erratic noise when it ramped up charging. We couldn't source it. It sounded not quite from the charger, and down in the boat. Problem is, there were no electronic devices down in there.

We dug out some ferrrites and slapped them on the 24V positive feed. The pitch changed. We tired more...more changes. I'd installed some large ferrites on the positive and negative feeds to my old 3000W inverter/charger to cut down on noise and interferance with my SSB radio.

Finally , Coulomb suggested we pull ALL the ferrites off. And the noises stopped...

Thank you aghain, Coulomb. Coming to the aid of a random stranger popping up in these forums was a huge act of generosity and it is very appreciated.

 

[bj_porter]

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.

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.

 

[bj_porter]

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!

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.

 

[bj_porter]

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.

 

[bj_porter]

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.

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...

 

[bj_porter]

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.

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...

 

[bj_porter]

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.

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.

 

[bj_porter]

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?

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.

 

[bj_porter]

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.

 

[bj_porter]

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.

 

[bj_porter]

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.

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.