charging batteries

[solar blue]

     i have 16 230 watt panels and just got lead acid wired in series for 24v questions are should they bubble hard at charging and would it be safe to set batt voltage at 30 volts  using midnite 150 have owned it bout three weeks    info greatly needed  im new to solar

[Westbranch]

You need to add all the info on those batteries / panels that you have, , make model etc, etc, etc for a reasoned response, other wise we are just guessing. 

[sigp2101]

        panels are 230watts at 24volts  canadian  batteries are 2volt 20insx4x6 11plates or sells i guess i bought them at a coal mine battery distribitor his words was charge them at round 30volts  this all new to me hope to go off grid but looks tuff for it seems there is much for me to learn

Every batt manufacturer has its own propositions on how to charge their batteries properly. Please provide batteries specifications if you know them.

[Westbranch]

Did they give you any information as to what they use them for? I have never heard of a Coal Mine battery so I googled it and it looks like they are used in mining locomotives etc instead of diesels so no fumes...

Post some pictures...

[Vic]

solar blue,

Are these batteries sealed,  or,  do they have easily removable caps on the battery top cover?

You really should either Post the manufacturer and model number of these batteries here,  or contact the manufacturer to get precise charge,  EQ  and Float voltages,  the Temperature Compensation value for charge/EQ voltages.   Information on the Specific Gravity (SG) for a fully-charged battery,  if the batteries are Flooded Lead Acid (FLA) types.   FLAs have caps on each cell that are easily removable.  You should also try to get info on the maximum charge current that the batteries will accept.

If the manufacturer has charge information for charging  the batteries from PV and a solar Charge Controller (CC),  this would be best,  as charging batteries from Grid power,  can be quite a lot different than is charging from Solar.

If you plan to use all of your PV modules to charge these batteries,   the charge current (charge rate) may be excessive for the batteries,  depending on the battery type,  and specs.   And,  you would probably need more than one CC to use all of those PVs on a 24 V battery.

FWIW,   Vic

[Vic]

Hi solar blue,

GNB Exide Titan batteries appear to be in the class of Flooded Forklift batteries.

Were the batteries that you have previously used?

Will continue to poke around on the internet.  looking for data.

The people that sold the batteries to you sure will be a good start in getting the important information on those charging details.

EDIT:  This battery may be similar to yours,  although,  it is in the GNB "Classic" line:

12-85C-11   24   425   9.84   31.5   12.94   23.25    930      M1601208511AFPC
Basic #      volts   Ah   kWh    ... dimensions ......    weight     product model number

FWIW,   Thanks,   Vic

[Westbranch]

Since you are making up a 24 volt battery you have to multiply those numbers 2.21 , and 2.6 by 12 as those are the values per 2v cell...

so 26.52V for Absorb and Float and 31.2V for an EQ,
you want to achieve a Specific Gravity of 1.285 and the reference temperature is 70* F

BUT he needs to tell you the Temperature Co- efficient , how much to adjust the charge voltage per degree change from 70*F

[dgd]

If these are FLA batteries then the float and eq voltages 26.5 and 31.2 look fairly normal but the absorb would/should probably be 29.2v for the 3 hours charge time mentioned or perhaps even closer to the 30v initially mentioned by the coal mining battery seller.
Just IMHO unless these are really designed to absorb at a low 26.5volts
Set the absorb timer for 3 hours and wire those PVs in serial connected pairs (nominal 48v) with 5 parallel strings into the Classic 150 via an MNPV6 with five  15amp breakers, one for each string.
My 2 cents worth 

Dgd

[Westbranch]

I hope you  are using the Local app that MidNite has available, it will make the settings update task very easy!

The TCV you now have is set in the Local App or MNGP and it is the amount of change that the Classic will make to the voltage it sends to the battery, if temp goes down more voltage is needed, if the temp goes up less voltage is needed.  Once set the Classic automatically adjusts based on the temp received from the BTS (Battery Temperature Sensor).

I believe he is telling you that the Specific Gravity should read 1.300 when you do an EQ but I don't understand why he gave you 2 different values. ?? 

The MNPV 6 is because you will have 5 STRINGs of panels to combine into one wire to the Classic. example
http://www.midnitesolar.com/pdfs/MNPV12%20BREAKERS%20wiring.pdf

It looks like DGD has chosen the most efficient arrangement for you based on wire costs and simplicity of pulling it all together and most importantly having a high enough Voltage to charge those batteries.

[Vic]

  dgd         i spoke to bat place tcv is like .2 i dont understnd and he says hydro should read 1.300 still dont understand what is the tcv used for  and whymnpv6 and why      and why wire pv to 48v

solar blue,

TCV is Temperature Coefficient Value.  For many Flooded batteries,  like yours,  this setting in the Classic would be in the Charge menu,  under " Temperature Compensation ".  You would want to enter -- 5 mV/C.

The target SG on your Hydrometer is 1,285.   In your phone conversation with the battery person,  you may have mentioned that your batteries were cool or cold,  right now.  In this case  Hydrometer readings would need to be compensated.   For battery temperatures below about 25 C,  the Hydrometer readings are a bit higher than the actual SG of the electrolyte.   This compensation value for SG readings is fairly small,  but,  for cold batteries,  it should be done.

Here is a good article on measuring SGs using a Hydrometer:
http://support.rollsbattery.com/support/solutions/articles/4347-measuring-specific-gravity

The above article gives approximate State Of Charge (SOC),  for batteries that have SGs that are 1.265 when fully-charged,  so your battery will need a slightly different table for that.

The compensation for Hydrometer readings is to subtract from the Hydrometer 3 SG points for every 10 degree F (about 5.5 points per degree C)  for battery temperatures below about 25 C,   and add to the SG readings that amount for temperatures above 25 C (77 F).

This is probably where that 1.300 SG value came from ...   but just guessing.

EDIT:  An Absorb voltage of about 30 V  is probably a fine place to start.  Most Charge Controllers do not have a Bulk voltage setting,  so just set Absorb voltage,  Float voltage,  and EQ voltage.   That stated Float voltage is quite high,  and if your system spends very much time in Float,  the battery will consume quite a lot of water.  You might want to start with a Float voltage  of about 27 volts.

If you do not have your Solar panels set up,  and ready to charge your batteries,  you may want a separate charger that could run from Grid power,  or from a generator.   Batteries with fairly  high SGs like yours,   will discharge themselves when sitting with no loads.

Back to work,   FWIW,   Vic

[Vic]

Hi solar blue,

Sorry for the reply delay ...   been traveling.

Regarding battery temperature.   The battery is a large,  heavy item,  and changes temperature fairly slowly.  It will really average the temperature variations that it is exposed to.

AND,  that Battery Temperature Sensor (BTS)  that came with the Classic  will do a good job of automatically changing the charge voltages,  based on the battery temperature that is measures.

For now,  just place that BTS on the top of one cell near the middle of the battery.  Later,  there may be a better place for the BTS.

When a battery is cold,  the charge voltages need to be increased somewhat to make sure that the battery is getting a good charge,  when a battery is warm,  the charge voltages need to be decreased a bit for a good charge.

More later ...  see that you are on-line now,  so will post this.

Thanks,   Vic

[Vic]

Hi solar blue,

A new Classic should have a Battery Temperature Sensor included.  This is from the description on the MidNite Solar site:

"FEATURES: •150 operating voltage   ...

   ...   Ships with MidNite Battery Temperature Sensor (MNBTS) and printed Manual".

If the Classic 150 was previously used,  then,  it is not uncommon for the BTS to not be included,  sometimes because the BTS has been installed on a battery,  and perhaps the cable pulled through conduit.

The jack for the BTS is a four conductor telephone type jack,  that is just to the right of the blue terminal block (that is used for the PV and battery cable connections).

The BTS usually has a blue,  flat cable with a blue flat plastic end for the battery,  and a four pin telephone type plug on the other.   The cable is about  4 Meters (approximately 12 - 13 feet) in length.

Here is a link to a photo of the MidNite BTS:
https://www.solar-electric.com/catalogsearch/result/?q=mnbts

More later,   Good Luck.   Vic

[Westbranch]

Solar Blue, here is a reference document from C&D that may help you to understand AGM VRLA battery charging.   http://www.cdtechno.com/pdf/ref/41_2128_0212.pdf

and terminology http://www.cdtechno.com/pdf/ref/41_7745_0112.pdf

hth

[Westbranch]

If they are so low they started to freeze, inside would be much better.

How low were the SG readings on each cell?

Are both the 12 v chargers the same make /brand?

[Vic]

solar blue,

An SG of 1.110  is a DEAD battery.

Freezing of a battery will usually cause so much physical damage that the battery is often ruined,  and not recoverable.

It can be dangerous to try to charge frozen batteries ...   although,  I have no experience doing so.

Keeping batteries in a warmer environment,   for cold climates would be better than having them outside,  even in an insulated cabinet,  box,  or shed.

Yes,  having several PVs in series would probably be fine on a 24 V battery system,  with a Classic 150.

What brand and model number are your solar panels?   This will help us give the best advice.

If you are seeing frozen batteries,   gentle charging would probably be better than charging at a high amp rate.

It may be very difficult to move your battery,   assuming that it is one battery in a metal case,  with batteries connected together with lead bars ...   your battery might have be different,  though.

More later,  Good Luck,   Vic