Low specify gravity with new T105's

equis

Hello

I have just purchased 16 T105's and have then configured for 48v
They seem to work perfectly, they hold over 49 - 50v during most nights, I use about 50ah a night.
I have a shunt and its telling me what goes out and when they are at full charge.

I have confirmed all is well, at the end of the absorb charge current is about 1.5%

The problem is SG is only 1.25 when charged.
I've seen is as low as 1.20 when they are down a bit.

This seems to indicate they are not at full charge.
Today I charged and got to 57v in about 4 hours, I absorbed for another 4 hours to be double sure.

Still 1.25 SG
Tested the car batt at same time and got almost 12.9

Thanks for any help.

:-)

waynefromnscanada

Re: Low specify gravity with new T105's

According to Trojan (is that your make?) "The specific gravity at 100% state-of-charge is 1.280"
http://www.trojanbatteryre.com/PDF/datasheets/T105_TrojanRE_Data_Sheets.pdf

vtmaps

Re: Low specify gravity with new T105's

What brand/model of batteries are you using? Some batteries need higher voltage and have 'end of absorb amps' of less than 1% of the C20 capacity. --vtMaps

icarus

Re: Low specify gravity with new T105's

My quick guess, without any mordetail, is that you are chronically undercharging them. 49-50 vdc means little with out knowing the loading. Similarly, charging for four hours to 57 vdc is also not very indicative. Depending on temp, one might expect to see 57.6 or more.

By my quick calc, you should be charging at ~65 amps for bulk. To recharge your 50 ah you are going to need a minimum of 60 ah of power not counting other system loses.

We need more info,, like what are your loads, what is your charge regimen etc.

Tony

Blackcherry04

Re: Low specify gravity with new T105's

A " T105 " is a specific battery made by Trojan, let's assume they are. " Just Purchased " could mean anything. They could have been manufactured last month or 2 years ago. You should be able to contact the place you bought them from and find out what they strength of electrolyte they were filled with. If they were factory filled or you know the " Constant " to try to get back to.

1) You need the know the temperature of the Batteries to compensate the SG reading to.

You need to start doing a Equalize Charge @ 60-62 Volts. You have to control the temperature of the batteries and keep them below 115 deg or so. Every 30 minutes or so take the SG readings and see if it is rising. It could take a couple hours ( 3-8 hours or more ) It's like taking care of a sick person, you have to stay with them. As long as the SG is rising, your doing ok, once it stops, stop charging.

If the Temperature of the Batteries rise above 115 deg, stop charging and let them cool off, then start back.

What you described is the very reason you have to do a " Commissioning " EQ on a New set of Batteries, so that you start out with a " Known " that you can always go back to.

If you don't have a 48 V charger, then you'll have to break them up into a volt size you can Equalize Charge them with.

paulskirocks

Re: Low specify gravity with new T105's

Are they Trojans? Here is the page from the Trojan website showing what you should be charging them at... http://www.trojanbattery.com/BatteryMaintenance/Charging.aspx

Looks like 59.2 volts is the proper daily charge voltage for theirs... Don't forget to set your meter for the proper full charge voltage, as well...

Photowhit

Re: Low specify gravity with new T105's

Looks like you replaced your AGM batteries with these in the last couple weeks?

Trojan changed their SG in their RE batteries from 12.6 to 12.8 in March of 2012, From the T105re PDF;
"Premium Line batteries manufactured prior to March 2012 have 1.260 SG value."

So perhaps you purchased new old stock batteries or Someone missed the memo and filled them with the wrong concentrate of electrolite.

I'm big on doing maintainance equalizing, but Trojan doesn't recomend equilizing unless there is a large difference between cells, but it couldn't hurt to do an equilizing and see if you can't get the SG up.

What kind of charge controller do you have and how are you dealing with your inverter problem?

Blackcherry04

Re: Low specify gravity with new T105's

He is going to have to be more Specific as what he has a " Trojan T105 or a T105-RE. No matter what he has 1.250 is going to be low and would require some action on his part to restore their capacity, The longer he waits the longer it will take and the harder it is on the batteries and the odds of 100% recovery becomes doubtful.

equis

Re: Low specify gravity with new T105's

Hello

Yes, changed from the AGM's to Trojan T105's
Going on advise from this forum I did a 4 hour equalize, testing every 30 mins, the came up perfectly. 1.277 SG
So as others have stated, looks like they have been undercharged over the last two weeks (since new)
I have changed my absorb to 4 hours, while on fine clear days this may be too much, I think for the average day it will work out better.

My Charge controller can do 80amps but I have set it to max 58.5 amp for my 450ah bank (13% as manufacture says)
Absorb charge is 57v and that seems to be in the range allowed also.
The manual says daily charge is higher tho, what do they mean by daily charge? its higher than absorb charge.
I figure I'll do an Equalize every 3 months if needed.

The inverter cutout (over voltage) problem has not happened since since I have the new Trojans and set max charge to 57v

Thanks again for all your help.
This forum may be on the other side of the world (I'm In Aussie) but its invaluable to me.

Rhys

vtmaps

Re: Low specify gravity with new T105's

equis wrote: »

Absorb charge is 57v and that seems to be in the range allowed also.
The manual says daily charge is higher tho, what do they mean by daily charge? its higher than absorb charge.

I don't have the manual in front of me, but I suspect that Trojan (like most battery manufacturers) is not using the term 'absorb' in the same way as we use it in the solar business. Most battery chargers (except for solar charge controllers) offer the type of charging profile that Trojan recommends.

read: http://forum.solar-electric.com/showthread.php?14738, especially the comments by 'stephendv'.

--vtMaps

Blackcherry04

Re: Low specify gravity with new T105's

Smiles for you Brother. You now have your " known ", it's a place you can and should be able to return to with manipulation of your daily charge and a reasonable EQ when necessary. It should mean that 100% of your plates are exposed and you'll receive back the maximum capacity of the Batteries over their useful life.

inetdog

Re: Low specify gravity with new T105's

equis wrote: »

Going on advise from this forum I did a 4 hour equalize, testing every 30 mins, the came up perfectly. 1.277 SG
So as others have stated, looks like they have been undercharged over the last two weeks (since new)
I have changed my absorb to 4 hours, while on fine clear days this may be too much, I think for the average day it will work out better.

Rhys

Hi Rhys,

For most CCs (I don't think that you ever gave the model you are using), the Absorb time is only a maximum for Absorb, and will be terminated earlier if the battery charging current goes below the End Amps setting. In that case, there is no harm in setting a longer Absorb time. If you have correctly configured the End Amps value (which will be a fraction of the AH number which varies with battery type), then you should not need to worry. It is not costing you any energy from the panels.

On the other hand, when charging from a generator, you would not want the Absorb period to be too long if a signal from the CC going into Float mode would be used to shut down the generator

Vic

Re: Low specify gravity with new T105's

Regarding EA, usually this will need to be set and enabled for the CC to use it to end Absorb. And the normal caveat applies; CC output current includes all loads on the battery plus the battery charge current. The value of the loads on the battery are often variable, so these loads can cause a variable Absorb time, as the CC cannot know what part of the output current is rperesented by the charge current into the batteries.

For larger battery banks, and smallish inverter loads, this is less of an issue than for small banks with larger variable and unpredictable loads.

With Flooded batteries, often an EA value can be chosen that on average is quite acceptable at maintaining SGs. The ease of measuring the SG in this situation helps a great deal in finding this value.

For the systems here, CC EA is by far the best way to terminate Absorb, as the DOD of the bank (and therefore the ideal Abs time) varies considerably from day-to-day.

inetdog

Re: Low specify gravity with new T105's

Vic wrote: »

Regarding EA, usually this will need to be set and enabled for the CC to use it to end Absorb. And the normal caveat applies; CC output current includes all loads on the battery plus the battery charge current. The value of the loads on the battery are often variable, so these loads can cause a variable Absorb time, as the CC cannot know what part of the output current is rperesented by the charge current into the batteries.
...
For the systems here, CC EA is by far the best way to terminate Absorb, as the DOD of the bank (and therefore the ideal Abs time) varies considerably from day-to-day.

Thans for the more detailed explanation, Vic!

Depending on the CC, putting a heavy load on the batteries through the inverter after the CC has gone into Float could either cause the CC to go back into Bulk or back into Absorb based on either increased current or reduced voltage, which is good because it allows the CC to pick up the load current. At that point, there is no agreed-on "right" behavior as to when to go back out of Absorb again, so you will need to check what your particular CC does.

Vic

Re: Low specify gravity with new T105's

inetdog wrote: »

Thans for the more detailed explanation, Vic!

Depending on the CC, putting a heavy load on the batteries through the inverter after the CC has gone into Float could either cause the CC to go back into Bulk or back into Absorb based on either increased current or reduced voltage, which is good because it allows the CC to pick up the load current. At that point, there is no agreed-on "right" behavior as to when to go back out of Absorb again, so you will need to check what your particular CC does.

Hi inetdog,

Well, not to beat this horse too severly,

Was trying to address only the effects of down-stream loads on the inverter (and perhaps the rare direct DC loads on batts) on EA, while still in Absorb. Any of these loads look to the CC like charge current into the batts, and will delay the transition to Float. If this delay is prolonged, it can result in "overcharging" the battery.

And, yes, once in Float the CC will generally stay in Float even if the Float voltage cannot be maintained (due to too little PV or other RE input current), until the set ReBulk V is reached if it is enabled. May depend on the exact CC, but that is the way things work here.

Thanks, Vic