(EDIT: Vic has encouraged me to report on the Trojan industrial batteries. I have arrived at charge settings that do work. I am open to other suggestions if there's a better way to simulate a bulk voltage that's higher than absorb voltage.)
Trojan publishes different charging specs for these batteries in different places. There's a data sheet that you can download from any retailer. Then there's a book specifically for these batteries that comes with each battery.
The batteries are supposed to provide an exceptionally high number of cycles. I suspect that this is linked to the low charge voltages and low specified SG. Trojan says SG of 1.26 is full instead of the more common 1.265 or higher.
The manual lists a "boost" charge of 61.92V, bulk 59.28V, absorb 56.4V, float 54V and equalize 64.8V.
The data sheet differs. There is no specification for bulk charge voltage and a higher absorb charge at 57.6V.
Does anyone know of a charge controller that will provide a 59V bulk charge then switch to a lower absorb voltage? (Rhetorical question; I'm not looking to switch. Or maybe I am curious but still not looking to switch.)
I've settled on absorb 59V, float 54V, and equalize 62V.
Absorb at 59V is using the Trojan specification for bulk charge. This works OK for now. Later I will be demanding more Wh from this system and that voltage may be too high for too long.
Float at 54V is as specified.
Equalize at 62V is using the Trojan specification for boost charge. Note that this is not a true equilization charge to correct for SG differences between cells. The user guide that comes with the batteries says to equalize when fully-charged SG drops to 1.230 or cell SGs differ by .05 or every 30 days. Seems to me the first 2 criteria are too lax; an SG of 1.230 would be about 80% charge.
I do see the SG dropping slightly and slowly then coming back up to 1.26 after an equalization charge.
If you have any other ideas about how to simulate the high bulk voltage then lower absorb voltage that Trojan specifies, then I'd be glad to hear them.
DEinME,
You are probably reading two different sets of specs intended for different uses. One set is for traction use any depends on daily charging after use. The other set of specs is more tailored to off grid use where you will not get the same timed charge daily.
In solar use a bulk charging voltage is not specified, the current is, it is usually in the range of 10-15% of the 20 hour amp hour rating of the battery, the the voltage is allowed allowed to rise to the absorb set point. At that point controller will switch to absorb and current will start to taper down to the finish current, which will trigger the float stage. At that point the controller will maintain that voltage , running all the loads.
The second set of specs is what you would want to use but do get a good hydrometer and read and record specific gravity readings. And flush,flush,flush that hydrometer to get good readings, throw away the first few readings until the hydrometer normalizes to the battery temperature. This will determine the exact absorb voltage set point. If s.g. goes over the recommended 1.260 then reduce absorb volts and or time. Too low s.g. try more time first then raise absorb voltage until you achieve that s.g.
Get a few charge cycles on those batteries and post your readings. Total kW charge , voltage at end of charge, time in absorb, and specific gravity readings and I will look at results and make further suggestions
If hydrometer readings vary more than 10 points ,start looking for trouble, at 25 points, you are in trouble, at 50 points its going to be a lot of work to recover if possible. Keep a logbook of readings any the data there will point to a problem before it gets serious.
David
I seem to have misled you.
Vic has encouraged me to report on how well these batteries are working since others seem to have trouble getting a good charge with the Trojan-recommended charge voltages. I can see why that would be with the low voltage that they recommend for absorb.
The batteries have been working fine for me with some creative reading of the Trojan specs. After a good charge I have 1.260 across all cells as accurately as I can read the hydrometer. But the batteries are still new (6 mo.).
While what I have been doing works for me, I a open to other settings that could replicate the Trojan specifications. But the batteries are getting healthy charges now and I'm very satisfied with their performance. Less satisfied perhaps with recommended settings.
I did want to report since Vic has mentioned it a couple of times.
Hi David,
Thank you very much for the report on your Trojan IND batteries.
It is good that you have been paying attention to how well the batts are getting charged early in their lives. Think that some folks with these batteries were not paying close attention initially, and probably got fairly far behind full charges regularly.
Thanks for the update, and good luck. Please let us know how well these batteries continue to work for you, as they seem to be a good candidate for larger systems.
EDIT: Often, deep cycle batteries have specs for charging from Grid power. These can be significantly different that batteries charged from RE (Solar in particular) sources. This can often explain the different charge parameters. Some battery manufacturers do not seem to have RE charge specs.
It might be possible to use Auto EQ in the Classics for the true Absorb stage, setting it to that lower Vabs. But this would probably only work is an Auto EQ only begins after the Absorb. Just a drive-by, and perhaps this makes no sense ... working on a project. Have never used Auto EQ.
Later, Vic
Your alert to me that some users have undercharged batteries certainly helped. I also couldn't ignore that higher bulk voltage although it's probably a limit and not a specification for constant-voltage charging.
I can see that if someone simply input the published absorb, float, and equalize values that they'd have significantly under-charged batteries.
The values above are working for now, but may overcharge once I am entirely on the new system. I'm still migrating services and will be for a while. E.g. there's no well yet and the cistern pump and purifier work from the old PV system.
Are these the 6 volt floor scrubber batteries?