Two Chargers Simultaneous Charging

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Two Chargers Simultaneous Charging

Post by Paul9 »

Hi people,

With the increase in public charging stations, I find my 10 amp charger doesn’t “cut the mustard” at a public charging station even though it is fine for overnight charging at home. As a result I have ordered a 2KW charger from TC Charger in China. It is supposed to supply me with 18 amps at 122v dc. I would have ordered the 3KW charger but I do not have sufficient spare space in the car to put it.

The thought then occurred to me that maybe I could use both the existing 10 amp charger and the new 18 amp charger simultaneously? This should give me just shy of 3KW into the battery bank.

I could mount the new charger in the spare battery bay which became empty when I changed from lead acid batteries to lithiums. I assume (?) I could attach both chargers’ positive and negative lines to the battery positive and negative terminals. The existing connection from my 3 prong plug to the existing charger could be modified by splicing in the new chargers’ connection(?)

The existing charger is a “InPower” 96volt 12 amp charger, for lead acid batteries, which was part of the “Goombi” kit. The expert pro and BMS instruments both show this charger as delivering 10amps.

The new charger is a TC Charger 122.4 x 18 amp.

All advice appreciated!
Thanks
Paul
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Post by antiscab »

The TC charger is isolated input to output, so yes that should work
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Post by coulomb »

The TC chargers certainly parallel with themselves. If you had bought the 3 kW charger, it would have been two 1.5 kW units in a box, with inputs and outputs paralleled. One charger becomes a master and the other a slave, so when you control one, it also controls the other, so it's just like a 3 kW charger.

Paralleling two different brand chargers (the InPowers are somewhat different inside) is not quite the same, but I agree with antiscab, it should work. If you switch the mains to the TC charger, it should also be able to tolerate voltage at its output even when switched off. It will impose a minuscule load on the battery (microamps).

[ Edit: input and output -> inputs and outputs; added "even when switched off" ]
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Post by neilg »

I don't think you will get the charge current (30A) you expect.
Once the battery voltage exceeds the InPower voltage (96v) it will think the battery is "full" and stop producing current, leaving the TC charger to put 18A into the battery.

So you will get 30A to 96v then 18A to 122.4v

Even adjusting (if you can) the InPower charger to 122.4v, the two chargers will probably not output their share (ie 12A & 18A) as the voltage rises.
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Post by Paul9 »

Thanks people,

I am a little confused (so what else is new). My current charger gets the battery bank up to 124.3 volts before it cuts out. I assume, during the charging process, the existing charger constantly reads the battery voltage and doesn't stop charging until a pack voltage 124.3 volts. Why would the existing charger, under my proposed arrangement, now start cutting out at 96v?

Thanks
Paul
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Post by neilg »

Sorry for confusing you.

"The existing charger is a “InPower” 96volt 12 amp charger,....."
I don't know the charger but you quoted the above so I assumed it was set for 96 volts.
Seeing it can charge to 124.3v then it will charge at the full 12A and the current will gradually reduce as it nears 124.3v.
If you put the TC charger in parallel it would have to be set to exactly the same voltage as the InPower charger but because of small differences within the chargers they may not output their full current during the whole charging process.

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Post by 4Springs »

neilg wrote: "The existing charger is a “InPower” 96volt 12 amp charger,....."
I don't know the charger but you quoted the above so I assumed it was set for 96 volts.
Seeing it can charge to 124.3v then it will charge at the full 12A and the current will gradually reduce as it nears 124.3v.
If you put the TC charger in parallel it would have to be set to exactly the same voltage as the InPower charger but because of small differences within the chargers they may not output their full current during the whole charging process.

Neil

I'm having the same thoughts as Paul9. In my case my lead-acid charger is '144V' - designed for 12 x 12V batteries. But of course this is a nominal voltage, and it actually gets up to 170V or so before it switches off. My lithium charger (48 cells) is also a TC Charger just like Paul9 - but mine will cut out at 175.5V (or a bit less because of the BMS). So I'm hoping that I'll get a bulk charge at the maximum rate from both chargers, and then probably the lead-acid one will shut off once the voltage gets up there. It will be up to the TC Charger and the BMS to top up the last little bit.

So it sounds like a TC Charger should theoretically be ok to put in parallel with any other charger? My lead-acid charger is a Chennic bought second hand from antiscab a while ago.
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Post by coulomb »

Chennic is another name for a TC charger anyway.
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Post by Paul9 »

Thanks people.


Further thought has prompted me to set up the following based on your advice to me:

a)Remove existing 10amp charger from present spot;
b) Install new 18amp charger into spot left vacant by removal of existing 10amp charger;
c) Connect new 18 amp charger to existing wiring, battery pos and neg, and 3 prong plug (no rewiring under car required);
d) Install existing 10amp charger into spare battery bay;
e) Connect existing 10 amp charger in battery bay to battery pos and neg but do not splice into existing wiring;
f) Connect J1772 adaptor to 15amp power board with two sockets;

For normal (slow) overnight charging I just connect 3 prong plug in car to power board with short extension lead.

For fast charging I use two extension leads, one to 3 prong plug in car and the other lead to 3 prong plug on 10amp charger installed in battery bay.

The advantage of the above over my previous idea is that the above needs no re-wiring at all and therefore fits within my limited ability to install!

Any and all comments appreciated.

Thanks again,
Paul
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Post by Johny »

Paul, without reading back through your posts. Does the 10A charger cut off when any cell goes overvoltage?
I.E. Is the charging system tied back to the BMS?
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Post by 4Springs »

Johny wrote: Paul, without reading back through your posts. Does the 10A charger cut off when any cell goes overvoltage?
I.E. Is the charging system tied back to the BMS?

Good point Johny,
My BMS talks to my TC Charger and dials back the current when the first cell starts to shunt. I was thinking that I'd put a relay in the supply to the smaller charger, and have the BMS switch it off at that same time.

Paul has the EV Power BMS - can you hook up a relay in a similar way?
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Post by Paul9 »

Good point guys!

The BMS shuts off the charging process at 121v pack voltage at which stage the existing 10amp charger is charging at just 3 amps. The existing charger would get up to 124.3v pack voltage, and shut itself down, if the BMS didn't shut it down at 121v.

As my proposed "system" has the existing charger connected to the battery pos and neg at one end, and the wall outlet at the other end, then maybe it would keep charging up to 124.3? I don't know the answer to that question - I will have to check how the BMS controls the existing charger in its present position.

I will check and let you know.

But then again, if the new 18amp charger stopped at 121v (due to the BMS control) and the existing charger stops (by itself) at 124.3, then I may still have no problem - I think? 124.3 pack voltage still only equals 3.66v per cell? Any educated guesses?

Thanks
Paul

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Post by 4Springs »

Paul9 wrote:But then again, if the new 18amp charger stopped at 121v (due to the BMS control) and the existing charger stops (by itself) at 124.3, then I may still have no problem - I think? 124.3 pack voltage still only equals 3.66v per cell? Any educated guesses?

If your pack is balanced then this would be fine most of the time, but what if your BMS stopped the charger because one cell was way higher than the rest? In this case the second charger would not be stopped, and that cell would be (possibly fatally) overcharged.
It will be interesting to learn how your BMS controls your charger. And then we need to figure out how to use it to control two chargers from two different 240V supplies.
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Post by Paul9 »

Yep 4Springs - didn't think of that!! Another advantage to talking to all the bright people on this forum!

I will do some checking and let you know.

Thanks
Paul
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Post by Paul9 »

Some progress.

The EV Power BMS has functionality to have up to three PFC chargers connected at once. It has three "charge enable" sockets each with a pos and neg. I assume therefore that the TC Charger has cables coming out of it to connect it to the BMS, as well as the cables to the three phase input and pos and neg cables to the battery bank?

The problem is that my legacy InPower PFC charger is for lead acid batteries and therefore never needed connection to a BMS. Therefore it does not have the extra cables to connect to the "charge enable" sockets on a BMS.

The above is "theory". What I do know is that my mates have wired up the InPower charger so that it IS controlled by the BMS. I will have to check with them as to how they did it. Any guesses?

As one of my objectives is to reduce the amount of new wiring I will have to do, maybe it may be better to leave the existing 10 amp InPower charger exactly where it is and put the new 18 amp TC Charger in the spare battery bay? Then connect the TC to the "charge enable" socket in the BMS?

I could then still use both chargers at a public charging station and use the 10amp InPower by itself when charging overnight.

I don't know if 4Springs has a similar problem as I don't know if his old charger is a lead acid or lithium charger.

I will keep you updated.
Thanks again,
Paul

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Post by 4Springs »

Paul9 wrote:The EV Power BMS has functionality to have up to three PFC chargers connected at once. It has three "charge enable" sockets each with a pos and neg. I assume therefore that the TC Charger has cables coming out of it to connect it to the BMS, as well as the cables to the three phase input and pos and neg cables to the battery bank?

The problem is that my legacy InPower PFC charger is for lead acid batteries and therefore never needed connection to a BMS. Therefore it does not have the extra cables to connect to the "charge enable" sockets on a BMS.

The above is "theory". What I do know is that my mates have wired up the InPower charger so that it IS controlled by the BMS. I will have to check with them as to how they did it. Any guesses?

My guess is that the three Charge Enable outputs are 12V when enabled (ready to charge) and 0V when it is time to stop. The simplest way to use this would be to power a 12V relay, which switches the 240V input to the charger.
If this is the way you do it then you'll just need another relay for the new charger. The relay can either be next to the BMS or next to the charger - either way you'll need to run two wires from BMS to charger.

Your new charger will be smart enough to do some special features, but your BMS is not smart enough to take advantage of those features.
Paul9 wrote:I don't know if 4Springs has a similar problem as I don't know if his old charger is a lead acid or lithium charger.

My old charger is a lead acid one. When it was installed I had a very simple BMS which turned it off using a relay as described above. My plan now is to do the same thing - I made my BMS so I know that I can make it switch a relay.

By the way, I decided that my 2kW TC Charger got a bit hot under the bonnet. So I put in a few fans:
Image

Image
There was nothing in the design of the heatsink that allowed for attaching fans, so I have used a piece of aluminium channel I had on the shelf. Screws go into the channel and it holds them on well enough.
I also bought a thermostat from Jaycar. So the 12V fans come on when the temperature gets up to the thermostat temperature (50 degrees from memory).

I noticed that a friend has also attached a fan to his TC Charger. Here is his method:
Image

Then someone the other day said that new TC Charger come with integrated fans, so this might not be required.
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Post by Paul9 »

Update.

My 2kw TC Charger arrived today! They promised 14 days delivery but I thought that was an optomistic estimate. It was precisely 11 calendar days!

I won't have time to test it until the weekend but it appears fairly simple except for the "charge enable" cable from the charger. The cable from the charger has red, black and green wires ( I assume pos, neg and earth).

My BMS charge enable socket only has connections for pos and neg according to the wiring diagram.

Suggestions as to what I do with or where to stick the green wire in the charge enable cable? ("Stick it up your ..." won't help as I would have to stand beside the car for hours while it charged!)

Thanks muchly,
Paul
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Post by coulomb »

Paul9 wrote: The cable from the charger has red, black and green wires ( I assume pos, neg and earth).
Eek! No. The green wire connects to pack positive before the output relay comes on. It's a changeover relay, and this is the normally closed contact. (The common of the relay contacts is the pack positive via a fuse; the normally open contact goes to the charger output.)

[ Edit: I was assuming the thick green wire, that sometimes comes out with the charger output wires. I see below that maybe you were talking about the thin wires from the 7-pin round connector; these are a completely different matter. They are still referenced to pack negative, so caution is still essential. ]

It can be used as a crude "don't drive away while plugged in" protection. They call it the "keyswitch interlock" output; you're supposed to wire it to a pack rated relay coil. That is only moderately inconvenient for lower voltage packs, like 24 V or 8 V. But even ignoring that, the big problem is, when the charge is finished, the output relay goes off, and pack positive appears on the green cable again. So you can still drive off with the charger plugged in, for the common case when you want to drive after the charge has finished. So really, the green cable isn't much use, and if you assume it's an earth wire, it could be dangerous.
Suggestions as to what I do with or where to stick the green wire in the charge enable cable?

Insulate it carefully, and don't connect it to anything. Although you could wire it to a neon light (with suitably rated series resistor, other end to pack negative), and mark it "not charging".

Or maybe mark it "not useful"   Image
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Post by 4Springs »

What's the manual say?
I seem to remember some confusion on the Charge Enable line when I hooked mine up. I'd better go and have a look at what I did...
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Post by Paul9 »

Thanks Coulomb. Lucky I asked!

4Springs - the manual is unclear and I haven't talked to my (electrician) brother yet. And the lack of clarity is expressed in broken English. You know, sentences like, "Not attempt to connect any two wires that not be connected." Hmm?

4Springs - wasn't there a post or two in a previous thread about TC Chargers where you had some problem with the 12v side of things?

Thanks guys
Cheers
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Post by 4Springs »

Ok, I've found my user manual for the TC Charger. I've also found the post that Paul refers to here: 4Springs' TC Charger question

I'll assume that you have the standard TC Charger Paul, not the CAN enabled one. From memory the CAN interface is an optional extra when you order your charger. It enables greater control over the charger if you had a computer to talk to it.
So the charger I have has the following connections. Check against yours, and if anything is different disregard everything I say!
The 240V in side has three wires, not sure on the colours. But these are the normal active, neutral and earth. This is on the left side of the charger.
On the right side of the charger are two sets of wires. The 150VDC outlet is quite large and thick and has two wires, red & black. This is positive and negative 150VDC.

The final one is the interesting one. This is smaller, with a round blue connector. There are three wires in here, red, black & green. The manual says they are red, black & white.
Pin 1 = ENABLE = black.
Pin 2 = GND = green.
Pin 3 = +12V = red.

The manual describes three methods of controlling the charger. This starts on page 22 section 5. You can use method A or B, but I'd suggest A as it uses a relay which is cheap and simple. I've scanned method A:
Image
So you need to test your BMS output. You said that there are two wires, check them with a voltmeter and see what happens. My guess is that it will provide 12V to 'enable' the charger, and 0V to disable it. If this is the case then the diagram is exactly right. On the left you have your BMS, in the middle you have a relay and on the right you have the charger.

If your BMS provides 12V, then use a 12V automotive relay. There is a diode in the diagram, that is a good idea. You can get relays with diodes built into them - this would be easiest. Get one from Jaycar or an automotive shop. Think about where you are going to put it, they often come with tabs to let you screw it to a handy wall.

You can see that they say to use the 12V (red) and ENABLE (black) wires from the charger. You don't need the green one, insulate it and tuck it away somewhere. It doesn't matter which way around these two wires are on the relay. Do not connect either of these to your car's 12V system or to earth - this is the mistake I made.

If you want to test the charger first without connecting to the BMS just join the +12V and ENABLE wires. It should charge up to its set voltage and then cut out. It should also cut out as soon as you disconnect the two wires from each other.

All this is completely contrary to what coulomb says! So I guess there are different chargers out there. Check your manual and make sure it is the same as mine before you do anything I have suggested. Hopefully coulomb will come back and say something to clarify this!
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Post by Paul9 »

Thanks 4Springs. Mine is not CAN enabled and appears to be exactly the same as you describe your charger.

Subject to anything Coulomb may advise I will go with your "A" option.

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Post by coulomb »

4Springs wrote: All this is completely contrary to what coulomb says!
Perhaps Coulomb has spent too much time on the *inside* of TC Chargers, sigh. I was thinking about the green wire which is sometimes supplied with the large red and black output leads from the charger. These chargers have a three position terminal block at the output; if the thick green wire is supplied, it connects to the middle of the three output terminals. But maybe they only use the green wire on the lower voltage models, so we EVers rarely see them.

I forgot that sometimes the chargers come with a thin green wire from the 7-pin round connector. My apologies for the confusion.
So I guess there are different chargers out there.
Well, there certainly are variations. Often, the thick green lead isn't present with the output leads. Sometimes, the thin green lead isn't present from the 7-pin round connector.
Hopefully coulomb will come back and say something to clarify this!

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Post by coulomb »

Just to be clear on the type of green cable I was talking about, that has pack positive on it when the charger isn't charging, and is often not supplied:

Image

At least it is safely tucked away inside an insulated quick connect female terminal.

The thin wires from the 7-pin round connector are still tied to pack negative, so you absolutely need the relay or other device to isolate your BMS or other controlling device from the pack.

As 4Springs mentions, connecting the +12 V and enable wires together will start the charger, *provided* that there is a battery connected to the output. Otherwise, you'll get the alternating red and green LED, indicating bad or missing battery.
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Post by Paul9 »

Luckily for me both 4Springs and Coulomb know much more about what I am talking about than I do!

The picture coulomb shows with the green wire is not the same as mine. I only have the red and black coming out of the whatsa-name. The green wire that confused me was the one coming out the opposite end to the 7 pin connector. The manual spends pages ( well maybe not pages but a lot of space) explaining the uses for the 7 pins in the socket and was telling sweet nothing about the other end.

I will proceed with 4Springs set up (the "A" scenario) as both 4Springs and Coulomb appear happy with it!

Thanks guys,
Cheers
Paul
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