Force Bulk Charge "Maximum Smoke"

[HawaiiOffGrid]

Hello Everybody!

so ive been trying to follow Sunking's theory of "Maximum Smoke' to get the best out of my FLA batteries. (GC2 costco 6V 210AH. 2 strings of 8 =48V) I have 4000 Watts of panels (4 strings ) and use about <3kwh of power a day. I have a FP1 3648 Outback inverter/FM80 CC. I live in Hawaii and even in winter get pretty decent sun. I recently changed my settings to Bulk/Absorb/Float=59.2. Absorb time=0 Float time=4hrs. My problem is that i cant get it to BULK. it starts floating in the morning and the voltage on mate3 reads 59ish, but my SG readings are about 1.250. which is only 70% charged according to spec sheet for those batteries (100% is 1300) . Batteries are 5 months old and have never been taken down to 50%DoD. When i manually initiate bulk from mate3 it immediately switches back to float because voltage is high enough.

Appreciate any advice,
Thanks!

[Mike90250]

With Absorb time = 0, it will go right to float. But you say that float volt voltage is 59.2, so what's the issue? Change Absorb to be 4 hours might do something different

[HawaiiOffGrid]

The issue is that it is float charging when (according to my specific gravity readings) my batteries are only ~70%. With the low amps of a float charge they will never reach 100%. As I understood the “maximum smoke” theory is to skip the absorb step, use bulk charging to get your batteries as full as they can (90%+) by overpumping them with current, then float when they are just about full. Because there is not enough time to absorb charge using solar. It slightly overcharges your batteries, but it is better than undercharging them.

[Bala]

Once you have set Bulk, Absorb and float to the same V as as your Bulk setting you now only have bulk charge rate. It does not matter what it is stage it is in. When in float it is still trying to get the battery V to the 59.2 you have.

The amount of Amps used to keep the batteries at that 59.2V is dependent on how charged they are and any other draw, from the inverter etc.
If you have a low current reading when at 59.2V then either the batteries are close to full charge or one or more could be faulty.

Are all your sg readings the same across every cell?

Are you using temp compensation for your sg readings?

Are you sure that 1300 is your target for full charge? seems a bit high.

[HawaiiOffGrid]

Every one is pretty close to 1250 (temp compensated) ...but that was at mid afternoon while still charging and fridge as only load. They might even be lower at resting? I haven’t done an equalize in a few months, but am trying to get them as full as I can before I do that. I contacted manufacturer of batteries and they sent me a chart that says 1300 is full and 1255 is 75%, but I thought it seemed high too... Especially considering they are one of the cheaper 6v deep cell batteries available.

One thing I can think is that maybe I put a little too much water in on last fill? The water is just barely under or just barely touching the bottom of the plastic vent. I read after that it should be 1/4” under the vent. I figured it would have evaporated by now, but haven’t lost a noticeable amount in the last 3 months. Maybe having slightly too much water dilutes electrolyte to give lower SG reading?

[Bala]

Have a look at this link from trojan,

https://www.trojanbattery.com/tech-support/battery-maintenance/

It gives good info, on low SG readings.

I had a quality set of batteries that lasted me 12 years and 12.6 was about as good as I got them to, the SG chart for them only goes as high as 12.8.

I would be doing and equalize and see if you can get them up.

Do you know if the batteries were new or old stock when you got them?

Did you take an SG and V reading when you first got them?

[HawaiiOffGrid]

I guess it’s possible I was sent me the wrong SG specs from manufacturer, I could double check with them... I didn’t do SG when I first got them, didn’t have hydrometer yet. First measurement was a few months ago (maybe 2 months after buying batteries) and readings were even lower. (1235-1250 right after sunset with no load) but that was shortly after adding water. They were new batteries from Costco with a 6/2019 sticker on em. Did you use manufacture suggested parameters, or “maximum smoke” parameters? You completely off grid?

[Mike90250]

if the batteries are not bubbling and you are not adding water, they are not being charged enough. Generally.

[Bala]

It would worry me that some were 1235 when you got them.

I am completely off grid and used manufacturers specs with my own adjustments over the years.

I live in the wet tropics in Qld Australia, I had trouble with mine using to much water. I had no need to use max smoke.

I have gone to sealed batteries so I dont have to worry about water.

As Mike asked, are they bubbling/gassing?

What is you V and sg reading in the morning before they start charging

[HawaiiOffGrid]

Right now it’s 11:20pm and voltage is 50.4. (Higher than typical for this time before switching charging settings) I’ll take some measurements in the morning. I’ve only adjusted specs to max smoke for the past 2 days and batteries seem to be bubbling and charging more than before. Before float voltage was set around 54v so it would float at that all day. (Manufacturer says fully charged resting voltage is 51.3)

[HawaiiOffGrid]

At 8am (and very cloudy, pulling 0.2kw) voltage was 52. SG readings pretty much the same (1250)

[Bala]

By the V readings it does not look to me like there is to much wrong.

I have a 24V system and are happy if Im not below 24.8 in the mornings. I have fridges and a freezer going.

I would give them a good equalize charge and see if you can get the sg up.

I would also buy another hydrometer. They are cheap and just to ensure that the one you have is reading correctly.