lifted club cars - lifted ezgo
Home FAQDonate Who's Online
Go Back   Buggies Gone Wild Golf Cart Forum > Golf Cart Repair and Troubleshooting > Electric Club Car
Electric Club Car Electric DS, and Precedent golf cars



Post New Thread  Reply
Thread Tools Display Modes
Unread 03-24-2014, 08:31 PM   #1
Gone Wild
 
Sergio's Avatar
Club Car
 
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 4,579
Default Passive Voltage Bypass for 8v battery

A site member spotted the passive voltage bypass on my batteries and asked me about them. I put together some images and a write up on how to build them and decided to post it here in case anyone else wanted to build them.

One of the challenges when batteries are charged in series is that the entire pack may became "out of balance". Even if you have a voltage converter and draw power from the entire pack, small differences in battery chemistry can make individual batteries have different charge/discharge profiles.
Once the pack starts to get out of balance, the batteries that reach voltage first will start to boil while the others will be undercharged due to reduced current available to them or due to the charger prematurely reaching its set voltage and turning off.

These devices basically sit there without doing anything most of the time, but when you charge the pack and the voltage across an individual battery reaches 10.2v (2.55vpc), the zeners start to conduct and they bypass some current around the battery so that the other batteries can continue to charge.

I saw the original concept in the EV car forums from a guy named Lee Hart, I did not like either of their implementations so I made some changes that I think makes the devices more reliable.

Here is a link with more information:
http://www.evdl.org/pages/hartregs.html

Diagram (Picture #1):
The part numbers are from Mouser electronics. The second circuit is to test the actual zener voltage of the diodes as they have vary.

Test Circuit (Picture #2):
I used this simple test circuit to measure the actual zener voltage of each diode and pair them together in order to obtain 10.2v. The particular zener in the picture (bottom left) tested at 5.18v, so this unit would be paired with a 5.02v unit.
Attached Images
File Type: png passive_voltage_bypass.png (26.1 KB, 0 views)
File Type: jpg pvbp_testing.jpg (253.1 KB, 0 views)
Sergio is offline   Reply With Quote
Alt Today
BGW

Golf car forum Sponsored Links

__________________
This advertising will not be shown in this way to registered members.
Register your free account today and become a member on Buggies Gone Wild Golf Cart Forum
   
Unread 03-24-2014, 08:34 PM   #2
Gone Wild
 
Sergio's Avatar
Club Car
 
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 4,579
Default Re: Passive Voltage Bypass for 8v battery

Parts (Picture #1):
I used an over-sized 10w resistor to dissipate the heat from the zeners and to act as the basis for the circuit.

I used 2 zeners instead of one since it provides lots of benefits: 5 watt zeners are much less expensive than the 10w and using 2 of them to add up to 10.2v allows you to compensate for the difference between the zeners.

I ordered the non-insulated 5/16 terminals because I wanted to solder those connections.

I had a lot of different sizes of heat shrinking tube already, so I used 3 different sizes.

Assembly (Picture #2):
Solder the red wire to the anode of one of the zener diodes.
Solder the black wire to the cathode of the other zener diode.
Place shrink tube over the solder connections but don't go over the zener diode.


Assembly (Picture #3):
Solder the other lead of the zener diode to each lead of the resistor as shown.


Assembly ( Picture #4):
Put shrink tube over the resistor-zener solder connection as shown.
Put some JB weld quick to bond the diodes to the power resistor (the areas circled in green), JB weld has good thermal transfer and it will help transfer the heat from the zener diode to the resistor.


Assembly Final (Picture #5):
Crimp/Solder the 5/16 ring terminals to the end of the wires.
Either put the zip-tie right after shrinking the tube around the entire part or re-heat the shrinking tube before putting the zip-tie. The warm supple heat shrink tube will make a pretty good seal with the zip-tie.

I ordered all parts from Mouser electronics, they have a price break at 10+ parts so keep that in mind when ordering. The final cost was around $2-$3/unit.

I built these units last year because the batteries that came with my cart were pretty out of balance. There was always a lot of "water" around the top of the good batteries. I finally started to check the individual voltages near the end of the charge cycle and discovered that my good batteries were above 11v while the bad ones barely got above 9v.
These devices kept the good batteries to about 10.6v while allowing the bad ones to gradually get to 10v.
One of the bad batteries eventually started to fail under heavy load so I decided to change the entire pack.

I have installed the devices on my new pack and hopefully they will keep the batteries from getting out of balance. It has only been 8 months since I changed the batteries and so far they are all 8.55v or 8.54v each.
Attached Images
File Type: jpg pvbp_pic_01.jpg (241.3 KB, 0 views)
File Type: jpg pvbp_pic_02.jpg (230.6 KB, 0 views)
File Type: jpg pvbp_pic_03.jpg (210.5 KB, 0 views)
File Type: jpg pvbp_pic_04.jpg (223.1 KB, 0 views)
File Type: jpg pvbp_pic_05.jpg (184.6 KB, 0 views)
Sergio is offline   Reply With Quote
Unread 03-25-2014, 11:41 AM   #3
Gone Wild
Club Car
 
Join Date: Sep 2012
Location: Alberta - Canada
Posts: 997
Default Re: Passive Voltage Bypass for 8v battery

Sergio - a few of us have been experimenting with continuous charge (virtually) using very-low-amperage battery maintainers. Would they be less inclined to allow individual batteries to fall out of balance? Kinda like the equalize-charge mode built into the chargers used on industrial battery powered forklifts and such?

My gut says yes....but....??
joesam is offline   Reply With Quote
Unread 03-25-2014, 05:33 PM   #4
Gone Wild
 
Sergio's Avatar
Club Car
 
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 4,579
Default Re: Passive Voltage Bypass for 8v battery

Not really... only a Battery Management System (BMS) with connections to all batteries or a Bank Charger would keep a series of batteries balanced.
The float or trickle chargers are good for a single battery but cannot do anything for a battery in the pack that charges faster or slower than the average battery in the pack.
Sergio is offline   Reply With Quote
Unread 03-25-2014, 06:19 PM   #5
Gone Wild
 
jjance's Avatar
Club Car
 
Join Date: Feb 2011
Location: Chattanooga TN
Posts: 2,105
Default Re: Passive Voltage Bypass for 8v battery

My 2 cents. Once a battery gets so far out of balance that it interferes with charging the entire pack it should be replaced.
jjance is offline   Reply With Quote
Unread 03-25-2014, 07:57 PM   #6
Gone Wild
Club Car
 
Join Date: Sep 2012
Location: Alberta - Canada
Posts: 997
Default Re: Passive Voltage Bypass for 8v battery

And that may be where Sergio's device comes into its own! If one of his passive bypasses is linked between ONE new and FIVE slightly older batteries - then the new battery is liable not to be bludgeoned to death with overcharging, and may integrate better into an existing (relatively healthy but slightly older) pack.

Although I have not had this happen to me, if I DID have a single battery fail in two or maybe three years - I'd be uhmmm....sad! And I'd like to have the option to replace the one dead battery (without boiling it to death) even though its going to be better at accepting charge than its companions.
joesam is offline   Reply With Quote
Unread 07-28-2014, 10:04 AM   #7
Gone Wild
 
Sergio's Avatar
Club Car
 
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 4,579
Default Re: Passive Voltage Bypass for 8v battery

Quick update:
My battery pack is now 1 year old so I decided to post the "state of balancing" of the batteries.
Pack Voltage after rest: 51.8v
Individual batteries:
8.62v
8.63v
8.63v
8.63v
8.62v
8.63v

I have been using the passive voltage balancers since day one, but since this is my first "new pack", I have no idea if 1 year old batteries stay well balanced without any help.
Sergio is offline   Reply With Quote
Unread 07-28-2014, 10:03 PM   #8
Gone Wild
 
55BigBlock's Avatar
Club Car
 
Join Date: Feb 2013
Location: NC/SC
Posts: 738
Default Re: Passive Voltage Bypass for 8v battery

Sergio, I am having trouble understanding how these are wired within the battery pack. Am I correct in assuming one circuit is across the positive and negative terminal on each battery in the pack? One more thing, why did you use the resistor only when the article called for a PR2 bulb and a resistor? I assume you did because of reliability and durability. One more thing, Is this modification invisible to the charger?
55BigBlock is offline   Reply With Quote
Unread 07-28-2014, 10:22 PM   #9
Gone Wild
 
Sergio's Avatar
Club Car
 
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 4,579
Default Re: Passive Voltage Bypass for 8v battery

Yes, there is one in parallel with each battery, they only conduct current when the battery voltage is above 10.2v.
I have used bulbs like that in other projects and did not like the idea of the vibration and heat around the batteries. The over sized resistor also makes for a good base to glue the split zener design.
It does affect the charging cycle, the idea is to prevent the charger from stopping too soon because one or more of the batteries has gone far beyond the preset voltage of 10.2+ volts.
Sergio is offline   Reply With Quote
Unread 07-28-2014, 10:54 PM   #10
Gone Wild
 
55BigBlock's Avatar
Club Car
 
Join Date: Feb 2013
Location: NC/SC
Posts: 738
Default Re: Passive Voltage Bypass for 8v battery

You said, It does affect the charging cycle, the idea is to prevent the charger from stopping too soon because one or more of the batteries has gone far beyond the preset voltage of 10.2+ volts.

Even though it affects the charging cycle, the charger will still cut off won't it? I leave the charger plugged into the cart all the time.


My batteries are out of balance. They are 4 years old. This is an inexpensive mod. that may buy me some time.
55BigBlock is offline   Reply With Quote
Reply
Go Back   Buggies Gone Wild Golf Cart Forum > Golf Cart Repair and Troubleshooting > Electric Club Car


Thread Tools
Display Modes


Similar Threads
Thread Forum
Battery Charger bypass OBC, Yellow Indicator light is blinking Electric Club Car
Battery voltage over 100% SOC Electric Club Car
battery voltage Electric EZGO
Need help hooking up a relay bypass in a club car battery charger Electric Club Car
low voltage on one battery Electric EZGO


All times are GMT -5. The time now is 04:58 AM.


Club Car Electric | EZGO Electric | Lifted Golf Carts | Gas EZGO | Used Golf Carts and Parts

Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2011, Crawlability, Inc.