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Discussion Starter · #1 ·
Recently purchased a VW beetle that has a K&W BC-20 charger in it. Currently, have 7 batteries set up in the beetle in series and am wondering how I set it up.

The current setup only had two wires coming out of the charger to hook up to the batteries. I assumed the red and black wires were just meant to hook up to one of the batteries in the series and everything would just charge after that. I set the manual current adjuster to 0 and then hooked up the batteries, as per the manual said. When I pug in the charger and increase the current the amp meter starts to go negative. Any suggestions here? I am sure I have the wires hooked up wrong to the batteries. Attaching a picture of setup for reference and a picture of the charger as well.

Thanks,
Spencer
 

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Holy Elon! Looks like you may be charging a 12v battery with a 36v 96v charger....

Try moving the skinny positive wire to the terminal where you have big positive (with red heatshrink) coming out of the box the other end of the string. Also your skinny wires aren't color-coded, make sure your polarity is correct from the charger.
 

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This is the way i was told to hook up a battery charger positive to most positive terminal, and negative to most negative terminal when charging batteries in series if the charger is set up to charge 7 12v batteries in series(84v nominal) and you are connecting the chargers leads to the a single 12v battery. Strange things will happen.
Later floyd
 

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That charger is quite sketchy - I've seen elsewhere that it can pump out over 100v when set to the max. I don't see any reference on the pot besides the screwdriver notch, not sure if it lines up with anything... It would be good to verify the output voltage before actually trying to charge anything.
 

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You have the charger connected like this:
Rectangle Slope Parallel Font Pattern


While you should connect it like so:
Rectangle Slope Font Parallel Handwriting


Without connecting the charger to the batteries check the polarity, the negative amps might suggest you have the polarity reversed. Then set the charger to ~95V (13.6V*7) before connecting the charger again.

Edit: I see my images are missing the positive and negative indications, please pretend I've drawn a + sign on the left side of the 12v batteries and a - sign on the right.
 

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You have the charger connected like this:
View attachment 128847

While you should connect it like so:
View attachment 128848

Without connecting the charger to the batteries check the polarity, the negative amps might suggest you have the polarity reversed. Then set the charger to ~95V (13.6V*7) before connecting the charger again.

Edit: I see my images are missing the positive and negative indications, please pretend I've drawn a + sign on the left side of the 12v batteries and a - sign on the right.
Nice! I got fixated on the picture, and didn't notice there were actually 7 of them.
 

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Discussion Starter · #7 · (Edited)
You have the charger connected like this:
View attachment 128847

While you should connect it like so:
View attachment 128848

Without connecting the charger to the batteries check the polarity, the negative amps might suggest you have the polarity reversed. Then set the charger to ~95V (13.6V*7) before connecting the charger again.

Edit: I see my images are missing the positive and negative indications, please pretend I've drawn a + sign on the left side of the 12v batteries and a - sign on the right.
That diagram is super helpful! I've been looking up "how to charge batteries in series" and found explanations that didn't make sense... In addition to your diagram some website said I need to connect every positive terminal into the negative line between the first and last battery into the system like I have shown in the diagram below. Here's the website for reference. Let me know what you think. And thanks for everyone's help! Love that this community is so willing to help newbie's like me, haha.

Rectangle Slope Font Parallel Pattern
 

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That diagram is super helpful! I've been looking up "how to charge batteries in series" and found explanations that didn't make sense... In addition to your diagram some website said I need to connect every positive terminal into the negative line between the first and last battery into the system like I have shown in the diagram below. Here's the website for reference. Let me know what you think. And thanks for everyone's help! Love that this community is so willing to help newbie's like me, haha.
That website correctly says how to charge your setup. You just may need to read more stuff to build a better mental picture of the context. Think about it this way - you just tried to set your thing on fire, but luckily your charger was unable to comply.
 

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Rectangle Slope Font Parallel Pattern

What?! In the above pic you have the negative wire connecting to the positive post of the 2,3,4,5,6th batteries assuming red is positive and black is negative. The above drawing is WRONG
Most positive and most negative terminal are the only two connections you need with your charger. Your charger is adjustable for voltage and current set it like ArieKanarie said
While you should connect it like so:
Rectangle Slope Font Parallel Handwriting

Without connecting the charger to the batteries check the polarity, the negative amps might suggest you have the polarity reversed. Then set the charger to ~95V (13.6V*7) before connecting the charger again.
later floyd
 

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Discussion Starter · #10 ·
That website correctly says how to charge your setup. You just may need to read more stuff to build a better mental picture of the context. Think about it this way - you just tried to set your thing on fire, but luckily your charger was unable to comply.
Rectangle Slope Font Parallel Pattern

What?! In the above pic you have the negative wire connecting to the positive post of the 2,3,4,5,6th batteries assuming red is positive and black is negative. The above drawing is WRONG
Most positive and most negative terminal are the only two connections you need with your charger. Your charger is adjustable for voltage and current set it like ArieKanarie said


later floyd
Thanks Floyd. Looking back and reading the website again, it was just talking about connecting the battery terminals together in series, and not the negative wire. Misunderstood! Here's the exact verbiage.

"One basic configuration for charging batteries in series is to connect the positive charger output (in red) to the positive end of one of the batteries. Then, connect the negative end of the battery to the positive end of the next one, and continue to do so for the rest of your batteries. For the final battery, connect the negative end of the battery to the negative output (in black) of the charger."

Definitely needed to take cricketo's advice and get a better mental picture so I don't "try to set my thing on fire", haha.
 

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Hmmm 20 max draw on a 15 amp multi tap circuit. What could possibly go wrong? Yeah I know you can limit current theoretical, but....get good fire insurance.
And bubble voltage for physical desulphation on FLA for 8 series is about 121 volts total, so not the best choice of charger. Oh and periodically change the last two negative batteries to somewhere more positive in the string. Old wives tale that is true.
 

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7 in series count the batteries, read the first post,
I agree with you about the load on circuit. he needs to use a dedicated circuit of at least 25A for charging.
bubble voltage for physical desulphation on FLA for 8 series is about 121 volts total
so 7 in series would be 105.875V for desulphation ? Which the charger can do.
Later floyd
 

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Hmmm 20 max draw on a 15 amp multi tap circuit. What could possibly go wrong? Yeah I know you can limit current theoretical, but....get good fire insurance.
And bubble voltage for physical desulphation on FLA for 8 series is about 121 volts total, so not the best choice of charger. Oh and periodically change the last two negative batteries to somewhere more positive in the string. Old wives tale that is true.
I run into that with a wirefeed welder from time to time. Breaker pops when 15A is exceeded, and that's about it.
 

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Claiming old age induced brain fade. Bubble is 106.4 on 7 or 2.53 @ cell...... non shiney plugs get really hot with high current and house circuit breakers have lousy tolerances, I wouldn't even discuss walmart purchased extension cords.
 

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Discussion Starter · #16 ·
Ok follow-up. I’ve wired thing properly in the vehicle. Now to tackle the breaker and wires. Any suggestions of what wire size/outlet/breaker set-up to plug this in? Charger has a 110v three prong input.
 

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Charger draws 20amps. Your question was answered in your other thread.

Dedicated charging circuit is at least 25 amp. Not breaker size, but circuit. That means wire sizes, plugs, sockets, breaker, and no taps anywhere. Being in a garage, it may also need GFCI.
 

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Discussion Starter · #18 ·
Charger draws 20amps. Your question was answered in your other thread.

Dedicated charging circuit is at least 25 amp. Not breaker size, but circuit. That means wire sizes, plugs, sockets, breaker, and no taps anywhere. Being in a garage, it may also need GFCI.
Largest 110v gfci’s I can find are 20amp… So instead of 110v normal outlet would I have to upgrade the charger input and wall outlet to a 240v 30a outlet like an RV hookup? In order to handle everything? link of what I’m talking about below…

Wall Outlet:
30-Amp Industrial Round Rv, Black https://www.lowes.com/pd/Utilitech-Black-30-Amp-Round-Rv-Industrial-Rv/3775473

Charger Input:

Charger Cord:
 
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