Precise charging voltages?

[Yellowjacket]

I have two 12 volt batteries in parallel with about 800 Ahour total capacity, a Mastervolt charger and about 1,080 of solar through a Victron 100 / 50 Blue Solar MPPT controller.

Battery manufacturuer SBS says my battereis are for pallet jacks or fork lifts and can be used as deep cycle. SBS says absorption voltage is the same as bulk voltage and is "between 14.1 VDC and 14.8 VDC." Float voltage is "between 13.0 VDC and 13.8". SBS says no temperature compensation is needed between 50ºF and 80ºF.

These recommendations seem a little loose to me based on what I read here and level of preceision available on my charging equipment. Would appreciate recommendation from the more knowledgable.

[john61ct]

It's fine to have a range, most charge sources are not adjustable.

If lots of your input is solar, adjusting to the higher end of the range will help raise SoC faster.

Set Float for the middle of its range, doesn't really matter.

Of course if you can reach their tech support they may tell you what is optimal for batt health.

Ensure whenever possible the end of charging, transition to Float doesn't happen until trailing endAmps is reached.

If they don't give that spec, can use .005C, so if 800, 4A. If that is never reached, 8A would be OK, or dropping less than .1A over an hour.

If these are FLA, keep the water topped up.

[Yellowjacket]

Thank you, John.

[noelex 77]

Often the battery manufacturer will provide different target voltages for different usage patterns such as cyclic use (this is the most applicable to regular boat use) and standby applications (where the battery is generally kept fully charged, but available, for example in the event of a main’s power failure). I assume it is the reason for the large voltage range.

Cyclic use has the highest charge voltages so I would interpret the limited information as recommending a 14.8v absortion and 13.8v float while the batteries are in regular use. This is also consistent with other manufacturers’ recommendations for flooded batteries (which I assume these are).

However, the guidelines are poor so if you can contact the manufacturer for more detailed information that would be better.

[Yellowjacket]

It has been absurdly difficult to get information from SBS Batteries. I'm six phone calls and at least that many emails into it. "Talk to your charger manufacturer," is the refrain. But now it's a challenge. I'll keep at it while I use your recommendations for FLA. Thank you.

[Yellowjacket]

I was able to get this from SBS. They did not know what I meant by bulk, absorption and float. I mean this quite literally. Four reresentatives.

I believe these are per cell voltages expected in my FLA tubular cell battery (6-85T-11) after a load draw, but some info is not labeled. It appears the info is on a spreadsheet, but with multiple variables per column. I would appreciate interpretation from the more knowledgeable:

6 hr ............. 20 hr .......... 100 hr
1.70 V..........1.75 V ...........1.9 V (in red)
450...............572...............893

Bottom row confuses me a bit. Numbers appear to be amp hours for a 12 volt battery, and that's what I was told when purchased (450 amp hours), but all other information on the sheet is per cell. It also would indicate a 20 hour draw down to 10.5 volts (6 cells X 1.75 Volts), which seems low but perhaps not for fork lifts.

[john61ct]

Those are the different AH capacities at different discharge rates, slower / lower current means higher total AH. Thanks Prof Peukert.

Nothing to do with charging.

Just use the guidance above, likely little difference.

For future reference, only buy expensive deep cycling batts from known good makers that have detailed tech specs and knowledgeable support staff readily available.

[john61ct]

The 20-hour rate is usually the one used for nameplate AH rating.

10.5V is zero SoC for load testing purposes, never go near there in normal usage

[Yellowjacket]

Blindly feeling my way forward using previous owner's footsteps, but your advice makes sense. Thank you.

I actually do know not to go to 0 SOC, but had been told or read that AH capacity was relevant to charging, but perhaps only to the battery's ability to take a charge and setting amperage for bulk. I was hoping interpolation of ideal voltage was possbile. That said, I'll follow the 14.8 V for absorption and 13.8V for float received here.

Thank you again for your assistance.

[john61ct]

The endamps stop-charge point is critical to get to 100% Full, at least 2-3 times a week when possible every cycle, precision there is more important than with setpoint voltage.

That is set relative to the capacity rating, .005C is about a 3A taper based off 572AH.

[Yellowjacket]

Thank you.

[noelex 77]

You have actually purchased more battery capacity than you realised, which is a good thing.

The capacity at a 20Hr discharge rate is 572 AHrs. So these would normally be classified as 572 AHr batteries, not 450 AHr.

Your frustration about the poor technical information is understandable, but this is not unique. Many great products have poor local distributors that have no idea how to deal with technical queries.

Try asking a technical question and you typically speak to a salesman. The electronic expert who actually designs the products and knows everything does not present the right corporate public image. On a bad day engineers such as this are known to frighten little old ladies and children so are not allowed to speak to customers.

[john61ct]

All of the makers I recommend make tech-savvy support staff available to owners of their product no matter how purchased. That is a precondition for my buying their product.

Sometimes I've spoken directly with the inventor, or a member of the founding family.

I agree that front-facing staff in distribution / retail channels hardly ever have anything useful to say, and often give out wrong information.

[Yellowjacket]

Originally Posted by noelex 77

You have actually purchased more battery capacity than you realised, which is a good thing.

The capacity at a 20Hr discharge rate is 572 AHrs. So these would normally be classified as 572 AHr batteries, not 450 AHr.

Your frustration about the poor technical information is understandable, but this is not unique. Many great products have poor local distributors that have no idea how to deal with technical queries.

Thank you, Noelex. Going over the specs, I realized I had 1,144 Ah of battery (two of these on the keel) by standard measurement, a good thing, and that they were tubular design which I believe makes them more robust as to shock. The old ones from same manufacturer withstood much.

For years it was my job to burrow past the smiles and get real info. My calls have been to the manufacturer, not local reps, but you're right, I kept getting routed to "Sales" where current knowledge was, and I quote, "you turn the knob for how long you want it to charge." I now have the name for an engineer with the firm. He's been out.

John61Ct's comment about 3 amp taper goes to a point I think you made in another thread about Victron. I can't find it now but I think you said that setting the tailing charge amp is not available on Victron, so watching amperage drop over time is key.

I've set absorption voltage at 14.8 and float at 13.8, but the Victron MPPT makes a decision when to go to float based on an algorithm unknown to me.

[Yellowjacket]

BTW, I purchased a Victron 712 yesterday ro replace the sad temp/voltage sensor that could not speak bluetooth loudly enough to be heard by the MPPT. Time to dive into wiring. Temp compensation should soon be automatic.