Charging question

Frxdy · Feb 7, 2008

Opinions please?

I have five 12V batteries on my EV motorcycle. I have five 12V chargers. I'd like to cut & splice & solder & make a giant plug that I can plug in and charge all at once. I think I'm OK doing as in this sketch, but in case I'm missing something that would make like the 4th of July..... I thought I'd ask. As long as the ignition key is off, hence the main contactor isn't closed, why wouldn't this work?

Thanks!

Fred

safe · Feb 7, 2008

Good Question

So basically you are anticipating only needing six wires for your plug?

I'm not the resident electrical guru around here, so I'm not the one to grant approval, but it seems like a good idea. The only possible problem would be if there was some sort of problem involving the interaction of the ground wires, but that doesn't seem likely. You did plan on having a true ground wire (sixth wire) right? Trying to ground to the bike is a scary proposition in my opinion.

Also, since on the bike the batteries are going to be connected in series you might want to consider what could happen along the series connections when the ground wires are connected together. That might create some unseen short of some type.

Frxdy · Feb 7, 2008

Yaaa, the idea is to have one six prong plug. The system is not grounded to the frame, a seperate ground wire for sure. I solder every connection and heat shrink them. I nevvvvver have shorts LOL.

Patrick · Feb 7, 2008

It won't be an unseen short, it will be very visible, just like the 4th of July.
You would have to disconnect all the series wiring in order to use that scheme.

The important part is whether your chargers have isolated outputs. If they do, then you can wire them in series, just like the batteries, and use a 6 pin connector no problem. If they do not, there aren't any easy answers.

Probably the easiest way to tell if they are isolated is to plug in two chargers, and see if there is any voltage between the positive of one, and negative of the other. In not, then they are isolated.

safe · Feb 7, 2008

You know now I remember reading about "ground isolation" in the power line business and that there are all kinds of issues that can crop up because of ground. You can get current that jumps from one ground location to the next.

In general it's better to break the series connection by disconnecting them physically. That's what I'm doing, I connect the batteries in series for riding and then in parallel for charging. Never had a problem.

Patrick · Feb 7, 2008

You know now I remember reading about "ground isolation" in the power line business and that there are all kinds of issues that can crop up because of ground. You can get current that jumps from one ground location to the next.

No, no, no, what he is referring to is ground loops. This is an important subject, but has nothing to do with this issue. It's a total PITA to disconnect all the series wiring (which has to have heavy current capability) to charge this way.

I don't know why Safe has to jump in to every discussion, and say "I don't know what I'm talking about, but here's what I think . . . ". I can only hope it warms up where he lives and he can go ride his bike instead of making endlessly useless posts.

TylerDurden · Feb 7, 2008

Patrick said:
I can only hope it warms up where he lives and he can go ride his bike instead of making endlessly useless posts.

We've been hoping the same thing for over 3600 posts.

Frxdy · Feb 7, 2008

Hmmmmm... it would be a total pain to disconnect all the 2 ought wires. I just went to see if they are isolated and, Waaaaa.... they are "smart chargers". Unless they are hooked to a battery they won't put out any voltage. Patrick, are you saying IF they are isolated, that it should work? The next thing, being smart chargers, would I dare to just test the idea using two batteries?

markcycle · Feb 7, 2008

he needs to stick with sanding fiberglass

http://endless-sphere.com/forums/viewtopic.php?f=6&t=1266&st=0&sk=t&sd=a&hilit=safe&start=420

Frxdy · Feb 8, 2008

I tested.... put two seperate batteries on seperate chargers. While they were charging I put a volt meter from postive on one battery to negative on the other.... zero volts. Then swapped putting the volt meter across the negative on one and positive on the other. Zero volts. I think that shows they are isolated and my idea should work. Any other thoughts?

fechter · Feb 8, 2008

Frxdy said:
I tested.... put two seperate batteries on seperate chargers. While they were charging I put a volt meter from postive on one battery to negative on the other.... zero volts. Then swapped putting the volt meter across the negative on one and positive on the other. Zero volts. I think that shows they are isolated and my idea should work. Any other thoughts?

Sounds like they are isolated. Fuses in line with the charger wires might be a good idea.

safe · Feb 8, 2008

Patrick said:
"I don't know what I'm talking about, but here's what I think . . . ".

If you actually go back and look at my posting I did identify the likely problem:

"...since on the bike the batteries are going to be connected in series you might want to consider what could happen along the series connections when the ground wires are connected together. That might create some unseen short of some type."

...so I don't see what I did wrong on that one. If I had said that everything was "okay by me" and the guy did it that would be irresponsible. I gave the correct answer. :roll:

Frxdy · Feb 10, 2008

safe said:
[ the series connections when the ground wires are connected together. That might create some unseen short of some type."[/color]

Oh baby! It was unseen until I saw the flash! LOL. OK.... 6 wires won't work, but 10 will. Off to buy another male female plug.

Frxdy · Feb 13, 2008

Done, and more importantly, it works. 10 wire, two for each charger.

safe · Feb 13, 2008

Frxdy said:
Done, and more importantly, it works. 10 wire, two for each charger.

Glad to hear everything worked out well in the end. In retrospect I should have said nothing or worded my response in such a way as to make it more clear that I was trying to advise more study before doing anything. Sometimes unless someone hears a full "no" they assume "yes" without more evidence.

Frxdy · Feb 19, 2008

If the original diagram showed the series wires making it a 60 volt system it might have been easier to understand. It was those wires that made the 6 wire idea short out when put in practice. All's well that ends well! I do appreciate everyones help.

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