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WMOV Profile
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Date Registered: 07-2016
TOTAL POSTS: 10
Reply | QUOTE
Charge voltage


Hey all,
Since i installed dual batteries on my t31 i have had voltage monitoring on both std and Aux circuits

The charging usually sits between 13.7 and 14v, but i would prefer to see it up around the 14.5 mark

does anyone have any detailed experience on the charging circuit / voltage regulation?

some cars around the period have a fuse for the voltage sense circuit, and you can trick the computer into charging higher by tapping off some voltage through a resistor in series with the fuse.

Happy to cut and solder into the voltage sense wire instead if there is one

Any help appreciated
6/Dec/2016, 3:20 pm Link to this post Send Email PM   Send Private Message Blog
 
Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 5814
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Re: Charge voltage


That charge level will take the battery into the gassing state and cause not only excessive water loss but higher battery temps which could damage the long-term capacity of the battery especially in ambient temps higher than 30degC as you would get under the bonnet and especially in summer.

---
Kev X450(c) T30 Guru
03 Titanium Ti T30 Series 1 **MODIFIED**
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6/Dec/2016, 4:09 pm Link to this post Send Email PM   Send Private Message Blog
 
WMOV Profile
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Date Registered: 07-2016
TOTAL POSTS: 10
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Re: Charge voltage


Thanks for the comment kev

Really???

Can you let me know what you base that on, as my trusted auto electrician suggested that I should be aiming for that voltage to get the best charging out of the deep cycle battery, and would also be fine for the starter battery.

He didn't have time before Christmas to book me in to look at the system, thus the post here.
6/Dec/2016, 4:18 pm Link to this post Send Email PM   Send Private Message Blog
 
Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 5814
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Re: Charge voltage


Search for "maximum charging voltage for 12v wet lead acid battery"
Various sites talk about optimum charging voltages for lead acid batteries being 2.3-2.35v/cell

14.5V for a standard wet 6-cell 12V lead acid battery is 2.417V/cell and gassing starts at 2.4v/cell

The other thing to remember about raising the voltage of your charging circuit is that vehicles now have far more electronics than they did and these electronics may be sensitive to over-voltages. Vehicle manufacturers would design circuits to cope with the expected charging circuits they design, not too much greater. One of the reasons they recommend jumper leads with surge protection to protect the ECU and other electronics.

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Kev X450(c) T30 Guru
03 Titanium Ti T30 Series 1 **MODIFIED**
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7/Dec/2016, 11:11 pm Link to this post Send Email PM   Send Private Message Blog
 
krocjp Profile
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Date Registered: 05-2017
TOTAL POSTS: 10
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Re: Charge voltage


Hi All,
I also had the same problem as WMOV with the charging of my 120AH, Deep Cycle AGM battery in the rear of Xtrail. Before my modification, the starting battery was charging to 14.0V maximum and the aux. battery to 13.9V max. The maximum charge for the AGM battery is 14.8V. My starting battery is a Yuasa NS70LX MF. Maximum charge voltage stated on the battery is 14.5V. The modification was to use a silicone diode (1N4004) 1 amp, in series with the alternator sense wire just before the plug on the alternator. There is 2 wires in the plug. Blue is the field wire and pink is the sense wire. I chose that location because the T31 X-Trail does not have a dedicated fuse for the sense wire. Its supply is fuse 34 in the engine bay fuse box and it also supplies the horn circuit. I used an in line automotive fuse holder to mount the diode. Just modify the fuse by removing the fuse element and replace it with the diode. The diode cathode (line end) goes to the alternator side. By using a fuse holder you can revert the standard charging if you wish by replacing the diode with a fuse. Remove fuse 34 while doing the modification. With this modification, the starting battery charges to 14.5v max. and the AUX battery charges to 14.4V . Also schottky diodes have a voltage drop of 0.2v approx. so by using 2 schottky in series, you can increase the charge voltage by 0.4v instead of 0.6v if you wish.


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Peter, Member No. X-5158
Newcastle N.S.W.
T31, 2012, Precision Grey, Ongoing Modifications
26/Jun/2019, 1:50 pm Link to this post Send Email PM   Send Private Message Blog
 
Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 5814
Reply | QUOTE
Re: Charge voltage


Keep an eye on your water level in the main battery and let us know how it goes in a couple of months please. That way others will know if there really is any danger to increasing the charging voltage with this mod.

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Kev X450(c) T30 Guru
03 Titanium Ti T30 Series 1 **MODIFIED**
My Blog
My CarPC Worklog
26/Jun/2019, 5:13 pm Link to this post Send Email PM   Send Private Message Blog
 
krocjp Profile
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Date Registered: 05-2017
TOTAL POSTS: 10
Reply | QUOTE
Re: Charge voltage


Hi Kev,
The start battery mentioned is a sealed no maintenance lead acid battery.
Cheers,
P.C.

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Peter, Member No. X-5158
Newcastle N.S.W.
T31, 2012, Precision Grey, Ongoing Modifications
26/Jun/2019, 5:17 pm Link to this post Send Email PM   Send Private Message Blog
 


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