Monitoring your battery voltage

Photomom

jcfaber1 said:

Durango tab, your 14 guage cable is yielding a 3.5% voltage loss.  What this means is you start out at 17.5 volts and by the time it gets to the battery it is 16.95 volts.  If a fully charged battery is 14.5 volts then you have 17.5-14.5=3 charging volts.  With the voltage drop, 16.95-14.4= 2.45 charging volts.  This represents an 18% reduction 2.45/3.0 in charging ability over the 25 ft cable.  You would be much better with a 8 guage cable.
John 

I think a fully charged 12 volt battery should be 12.6 volts, not 14.5. 2.1v per cell.

DurangoTaB

@jcfaber1...thanks!  Kinda what I figured.  25ft of 8ga wiring might be a little bulky, but even 12ga would be an improvement (and I assume no problem with installing the Zamp banana plugs).  Thanks again...

DurangoTaB

Just off the phone with the good folks at Zamp...they said someone (our dealer...now gone) sold us the "maintainer" cable...we should've gotten...
http://www.zampsolar.com/?s=ZS-HE-15-N
...and they gave me the name of a local (1hr away) dealer...nice!

Verna

DurangoTaB said:

@jcfaber1...thanks!  Kinda what I figured.  25ft of 8ga wiring might be a little bulky, but even 12ga would be an improvement (and I assume no problem with installing the Zamp banana plugs).  Thanks again...

@DurangoTaB, 25' of 10 gauge stranded marine wiring will work with the Zamp with no noticeable voltage drop. I never did try the 14 gauge Battery Tender extension with the Zamp, and it is 14 gauge.   Strange, but the same 10 gauge stranded marine wire will not work with the ARB. According to ARB, it is 10' too long, and that does cause too much of a voltage drop. 

DurangoTaB

Ryan at Zamp confirms what you say Verna...the correct replacement extension is 10-2, with little/no voltage drop.

jcfaber1

Photomom, from the reading I have done and the charging logarithms a lead acid battery during the absorption phase is usually at 14.4 or 14.5v.  I understand that at resting the nominal voltage is 2.1 per cell.  In order to fully charge a battery the voltage must be higher than what we want at resting phase or no charge will enter the battery.  There's a guys blog - handy Bob's Solar you can read that explains the charging process and the relevance of voltage drop better than I can.
John 

jcfaber1

10 guage wire ,25 ft, 17.5 volts, 4.56 amps will yield a1.37% drop says my calculator.  You should be OK.

DurangoTaB

@jcfaber1...turns out it's 15ft...even better!
Bob's Solar: https://handybobsolar.wordpress.com
Backcountry Solar (super Zamp distributor in Cortez): https://back-countrysolar.com

Nomad

I have a 10 or 12 gauge (same as the original cable on my Zamp), 30 foot extension and to tell you the truth, never notice a drop - in practice, if you have your panels out with sun, does it matter if it takes x-minutes longer to fully charge? Doesn't to me.

DurangoTaB

ours was taking 2x as long to charge!

Nomad

Hmmmm - I'd might notice that. Mine are always out, I check my start point in the morning and then don't really monitor it till I need a full battery to run the inverter and chage all my stuff. If the battery showed full at 10 vs 8-9, oh well :-)

chuckshaver

I have a Zamp 160. Does the voltage reading on the Zamp readout the charging rate or the condition of the battery?

wizard1880

Chuck I have the same panel.  The charge controller's voltage is just showing exactly what it reads from the connected battery.  It will rise up to 14.4 (for flooded acid) when the charging has reached the absorption stage of charging, then drop down to 13.2 float when it's done.  If there's any load on the battery, it will try to stay in charging mode to compensate.  There are indicators on its LCD screen to let you know which stage it's in.  I've found it to work extremely well in a plug and play scenario, i.e. plug it in and forget it.  But do put a lock cable or chain on it if you're not at camp!!