I have 4 Interstate 6v GC2-XHD-UTL house batteries, two series strings in parallel. Setting up the Midnight Solar 200 Classic Light and I think the Absorption rate appears to be on the high side.Specs at http://www.interstatedealers.com/pdf/201535.pdf show Absorption at 7.65 for 6v so I double to get 15.3I did find other documentation below that also states 7.65 Absorption Last towards bottom;http://www.batteries-faq.com/activekb/questions.php?questionid=1BatteriesInterstate GC2-XHD-UTL232ah/battery 464 totalBulk 14.4Abs. 15.3Fl. 13.4Eq. 15.6InputV Battery Offset adj. -0.1 InputV Array Offset adj. 1.8Should I stick with the 15.3 or drop it down?

First question is why look up the specs if you are going to second guess them? I use right around that voltage. Absorbtion is a higher voltage but with a continually dropping current that goes right down to almost nothing at the end, then you get the maintenance or float charge. Your numbers look perfect to me.

mchero wrote:I have 4 Interstate 6v GC2-XHD-UTL house batteries, two series strings in parallel. Setting up the Midnight Solar 200 Classic Light and I think the Absorption rate appears to be on the high side.Specs at http://www.interstatedealers.com/pdf/201535.pdf show Absorption at 7.65 for 6v so I double to get 15.3I did find other documentation below that also states 7.65 Absorption Last towards bottom;http://www.batteries-faq.com/activekb/questions.php?questionid=1Look at this it will show volts per cell. Just use the vpc and times by 6 BatteriesInterstate GC2-XHD-UTL232ah/battery 464 totalBulk 14.4Abs. 15.3Fl. 13.4Eq. 15.6InputV Battery Offset adj. -0.1 InputV Array Offset adj. 1.8Should I stick with the 15.3 or drop it down?Use this Use the VOLTS PER CELL VPC numbers times six

This comes up from time to time. Interstate wrongly gave that high voltage for the Vabs when they really meant it for the "finish" stage in a particular charging profile (third one down at bottom of this)http://pdf.wholesalesolar.com/battery-folder/charging_instruction_2011_2.pdfSo for "normal" charging like the two- step one in the middle graph, use 14.8v for your Vabs and you will be fine. Only use the 15+ voltage step occasionally to do the recommended "overcharge." Keep an eye on your SG with an hydrometer to tell when you need one of those overcharge sessions. (also makes you look at your "water" level, which is a good thing)

VintageRacer wrote:First question is why look up the specs if you are going to second guess them? I use right around that voltage. Absorbtion is a higher voltage but with a continually dropping current that goes right down to almost nothing at the end, then you get the maintenance or float charge. Your numbers look perfect to me.Because Interstate are idiots at getting correct information to there customers. The batteries are made in Mexico in a factory that US battery built. US battery charging specs

BFL13 wrote:This comes up from time to time. Interstate wrongly gave that high voltage for the Vabs when they really meant it for the "finish" stage in a particular charging profile (third one down at bottom of this)http://pdf.wholesalesolar.com/battery-folder/charging_instruction_2011_2.pdfSo for "normal" charging like the two- step one in the middle graph, use 14.8v for your Vabs and you will be fine. Only use the 15+ voltage step occasionally to do the recommended "overcharge." Keep an eye on your SG with an hydrometer to tell when you need one of those overcharge sessions. (also makes you look at your "water" level, which is a good thing)Dang BFL13 you put it sooooo much nicer then i did. :B

Absorption Voltage question. | Good Sam Community

RDMueller
Explorer
Dec 11, 2015
MEXICOWANDERER wrote:

I love it!

Car GPS instructs clearly to make a LEFT RIGHT HERE

Right up a freeway off-ramp

Mustn't question instructions...

:)

Yep, reminds me of this scene from the Office:

The Machine Knows
MEXICOWANDERER
Explorer
Dec 04, 2015
grizzzman wrote:
VintageRacer wrote:
First question is why look up the specs if you are going to second guess them? I use right around that voltage. Absorbtion is a higher voltage but with a continually dropping current that goes right down to almost nothing at the end, then you get the maintenance or float charge. Your numbers look perfect to me.

Because Interstate are idiots at getting correct information to there customers. The batteries are made in Mexico in a factory that US battery built. US battery charging specs

I love it!

Car GPS instructs clearly to make a LEFT RIGHT HERE

Right up a freeway off-ramp

Mustn't question instructions...

:)
grizzzman
Explorer
Dec 04, 2015
grizzzman wrote:
red31 wrote:
would not the screwy31 be lead Calcium while the GCs have some antimony?

Haven't I seen battery type 'calcium' as a charge profile default setting with 15.3v abs?

The interstate GC2-XHD are a hybrid battery with low antimony positive plates and calcium negative plates a "finish absorb" after a full charge (something between a top charge and a equalization) after deep discharges it is recommended at 15.3
grizzzman
Explorer
Dec 04, 2015
Oops
landyacht318
Explorer
Dec 03, 2015
Balmar's programmable voltage regulators are well regarded in the boating world, if one is willing to spend 300+ dollars for the external regulator.
mchero
Explorer
Dec 03, 2015
Thanks for all the reply's. I'll drop it down to 14.4.and work from their.
Was discussing some issues with a tech at Midnight Solar and he also thought that Absorption voltage was on the high side as well.

Guess it's good to second guess eh? LOL

Also thinking about setting up a relay that will disconnect the "Aux Start" solenoid if I'm driving down the road and the solar is charging the battery.

Has anyone played with those three stage alternators?
http://www.balmar.net/
scrubjaysnest
Explorer
Dec 03, 2015
All one can do is hope the manufacture gets it right. The interstate web site has had absorb at 15.3 for several years.
2oldman
Explorer II
Dec 03, 2015
I have never seen absorb that high.
red31
Explorer
Dec 03, 2015
would not the screwy31 be lead Calcium while the GCs have some antimony?

Haven't I seen battery type 'calcium' as a charge profile default setting with 15.3v abs?
landyacht318
Explorer
Dec 03, 2015
The screwy31 is a USbattery.

If it did not get some time( more was better) at 15.3v each solar recharge cycle,applied only after 2.5 hours at 14.9v, it packed up all its toys and went home. SG would max out at 1.225 after a week of deep cycles and Absorption voltage of only 14.7v, and overnight voltage held was abominable for the AH removed.

Granted this was a 12 volt group31 battery, not a 6v GC-2 battery.

Even with the 14.9v for 2.5 hours then afternoon of 15.3v regimen, specific gravity and performance walked downward until the next EQ charge at 16v was performed.

The screwy31 is still alive, powering lights fans and a TV in my workshop, but I estimate its usable total capacity at abou 55AH, originally claimed to be 130. It drops to 12.12v using just 23AH from it at no more than a 1.5 average amp rate.

Probably 550 deep cycles on it now. No shorted cell yet though. Lots of self discharge and it gets recharged by my twitching tweeker of a Schumacher sc2500a on the 12 amp AGM setting, whenever I feel like it.

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