Maual does not show Bulk or Absorb charge values.

westbranch · April 2012

I have come across some very puzzling information while looking for the Bulk and Absorb voltages for some new–to-me telecom batteries. They are
AT-15P 840Ah (8 hr rate) C&D msEndur II AGM batteries (2V cells).

Sec 7.1 states” the cells should be Constant Voltage charged at the average float voltages, as noted in Table 1.
http://www.cdtechno.com/pdf/ref/rs_02044_0508.pdf

There is no mention of the words Bulk or Absorb anywhere in the manual! Just Float and EQUALIZE!!.
Sec7.1, table 1 also mentions a FRESHENING charge if needed upon installation and it is mentioned again later in the manual if Sulphation is suspected.

Table 1.
Cell type..... Float V............... Freshening V........ EQ time
AT............. 2.25 – 2.30 V /cell 2.35 +/- .02 V /cell 12 – 16 Hrs
12V equivalent 13.5 – 13.8 ......... 13.98 – 14.22
Mid point....... 13.65V................ 14.10V

Values to be temp adjusted.

Sec 8.1 states that the batteries must be constant voltage charged as per sec 7, and that an EQ should be performed when a cell is .05 volts lower than the avg float voltage..

Chargers to be current limited to 25A / 100Ah of rating (200A for this battery).
I am planning on using a 40A Meanwell charger so that is well within limits.

I phoned the “local” Office and asked about bulk or Absorb, and these concepts were not even in his vocabulary. He said just charge at a constant Voltage until charged.

C&D also has 2 lines of ‘solar batteries’. They are ~max 175 Ahr rated and I looked at their charge parameters. The parameters are a bit different:

Type
Solar TFA 155 -175 Ah Volts per Unit 12.0 V
Max Charge Current 30 Amps @ 80% DoD
Float Voltage 13.62V - 13.8V
Cycle Service & EQ Charge Voltage 14.4V – 14.8V
Charger Max Ripple 1.5% P-P of Float V
Max V = 4% P-P
Max Current = C/20 = ~ 47A

Solar VR
33 – 100 Ah 12.84 V
Mac charge current C/5 @ 20 Hr rate
Float Voltage 13.5 V - 13.8V
Cycle Service & EQ Charge Voltage 14.4V – 14.8V
Max Ripple 1.5% P-P of Float V

More like ‘standard ‘ PV recharging regimes.
Cycle Charge looks like Bulk, Float is Float so the question is: What value to use for Absorb…
I have a request in to C&D, waiting for an answer…
Comments?

niel · April 2012

Re: Maual does not show Bulk or Absorb charge values.

this often gets confusing to people because bulk voltage doesn't technically exist. a battery stays in bulk with all current available being supplied until it reaches the voltage it is to transition to absorb. (the battery rises in voltage while in bulk.) after enough charge it will hold at this transition voltage and that will cause a tapering of the current into the battery as the charge progresses. this transition voltage and what they list as cycle is the absorb voltage.

Cariboocoot · April 2012

Re: Maual does not show Bulk or Absorb charge values.

It's about the application.
Telecom batteries, right? Meant to sit there with 13.8 Volts on them 'til needed (power out) and then the charge Voltage comes back and brings 'em up again. Occasionally they get an "Equalization" (probably just after being used). Never intended to be drawn down 25% and then brought back up quickly in one day.

That's not saying they won't work that way, though.

Go with 14.4 Volts and do the usual check for time of Absorb, specific gravity, and water loss. Turn them up 0.2 Volts and check again. If they're still doing okay, go for the 14.8 and see what happens. If water use or battery temp goes up to a level you're uncomfortable with, back the Voltage down.

Often people get confused by charging data supplied by manufacturers because it "conflicts" with what they read here. But the manufacturer supplies data according to the intended use, including how it is to be recharged. Solar/RE is a relatively new thing and they don't have data for every battery you could possibly use. Look at forklift batteries. And then there's individual install variations according to the particular application.

It's mostly science, but partially art.

westbranch · April 2012

Re: Maual does not show Bulk or Absorb charge values.

Errr Marc, can't check SGs...

westbranch wrote: »

telecom batteries. They are
AT-15P 840Ah (8 hr rate) C&D msEndur II AGM batteries (2V cells).

Niel, tanks for clarifying the issue about Bulk and Absorb definitions vs "CYCLE".

Marc,"Never intended to be drawn down 25% and then brought back up quickly in one day." I thought of that and also thought about the fact that there could also be the case of 80%+ DoD (mentioned in the manual) and what would happen in a major outage? A long slow recharge is good at some times but what about when the charge is not fast enough and another outage occurs, a heavy charge should be in order..??

the strange thing about their manuals is that all applications, using different AGMs are almost all identical, with very minor differences. Don;t quite know why they would only make 175 Ahr batteries for solar applications for telecom when repeater sites could use much larger banks??

Anyway, I will see what C&D has to say. My Absolyte AGMs had a similar regime to the PV series, so I plan on using them as a guide. As you said Marc, "see what happens".

Next this conundrum turns to how to charge with a 3 stage battery charger. Have to check out if the Meanwell 1000W 2/3/8 stage charger can be adjusted.

Cariboocoot · April 2012

Re: Maual does not show Bulk or Absorb charge values.

I meant drawn down on a regular basis the way we use RE batteries.

There's a Telus substation near here which is basically a small building full of batteries ... and another small building with a generator in it. So I guess they cover their bases for long-term outages that way; either the gen autostarts at some point or a man in a truck comes by and turns the key.

Sorry I missed the AGM designation. Seem to be a bit blurry-eyed this morning.
Transformer. Transformer. Transformer.
Blast; messed it up on the last one.

(Reference to another post.)

Maual does not show Bulk or Absorb charge values.

Comments

Categories