Sunxtender Batteries

[Tons001]

Does anyone else out there have Sunxtender batteries? I have PVX-3050Ts. Both their technical manual and customer support say they need to hit .5% of capacity to be considered fully charged. I am having a hell of time getting the EA to less than 1.5a. They seem to level off around 3 amps. If I let them absorb for 5+ hours, I can get the EA around 2 amps but that seems like a really long time.

Any suggestions on what I am missing or doing wrong? I doubt I will ever hit Float with a 0.5% of capacity EA setting or 1.5 amps across the WBjr.

Thanks ... Marc

[boB]

Sunxtender's are a common battery.

Hey, if they don't go any lower than 2.0 amps with their voltage set at absorb, then that's what
they need.  You should be able to end the absorb at there or a bit higher current I would think.

How do you really ~KNOW~ when you are at a certain capacity ?  It's hard to tell with ending
amps.  I think you just gotta do what you have done and see what the minimum current is
they take after a while.  You've evidently found that to be 2 amps.

That current will more than likely go higher than 2 amps as the batteries age.
Or, that current may go down a wee bit and then rise as they get older.

Some batteries when brand new do not reach full capacity until after around 100
charge cycles.  Could your batteries be new enough maybe that might be
the issue ?

boB

[Tons001]

Thanks Bob .... this is really useful information. I commissioned the batteries in August so I should be past the 100 cycle mark. If I had it all to do over again, I would have gotten FLA so I could check the SG and end the guessing game. Less learned.

[RossW]

If I had it all to do over again, I would have gotten FLA so I could check the SG and end the guessing game. Less learned.

As someone who's been using AGM cells for the last almost 10 years in a 100% off-grid environment (and destroyed a good number along the way), I recently designed and built a system to monitor each cell in a string.

It's been in service now for about a week and I wish I'd done it years ago. Finally, for the first time in its life, I've had meaningful data on how each cell is going. I've been able to manually assist cells balancing (adding a 0.5 ohm resistor across a cell as it gets to "full" and voltage suddenly climbs). The last couple of nights, my string has gone from barely able to run 6 hours without the generator starting, to making 60 hours straight without the generator running!

I'm just starting to think now about ways to incorporate some sort of automatic balancing. We all know LFP (LiFePO4 etc) absolutely require BMS, but I can't recall seeing anyone advocating it for lead-acid. Flooded cells may be sufficiently tolerant to just boil them for hours to equalize, but AGM/SLA/VRLA are a different beast, and from what I've observed over years, and what I can now quantify, I think there is a definite market/need for 2V cell balancing!

[ClassicCrazy]

There was a research paper I recently read about AGM batteries and how they are not floated properly in standby conditions and how they don't last long. Not sure if I read that article from a link on here somewhere or not. But I think the main point was that AGM's  need special setpoints and treatment to make them last as long as they should.

I know from work that the backup batteries in certain fire alarm panels only last a year or two. True they are not the greatest battery brand but I think the float charger is also to blame.

[boB]

I am an advocate of battery balancing.  FLA batteries could also use them as RossW points out.

But for some reason, (experience ?), I really think that AGM's and Gells need  them worse.

With battery balancing and keeping the voltage across batteries as close as possible from
the start, I think you could do wonders with a bank...  For example... wouldn't it be nice to
be able to parallel as many strings as you want to without worry ?  (as long as you can
charge them that is)

boB

[vtmaps]

For example... wouldn't it be nice to be able to parallel as many strings as you want to without worry ? 

I can't run even one string without worrying     --vtMaps

[Halfcrazy]

I am an advocate of battery balancing.  FLA batteries could also use them as RossW points out.

But for some reason, (experience ?), I really think that AGM's and Gells need  them worse.

With battery balancing and keeping the voltage across batteries as close as possible from
the start, I think you could do wonders with a bank...  For example... wouldn't it be nice to
be able to parallel as many strings as you want to without worry ?  (as long as you can
charge them that is)

boB

boB I suspect the reason you "Think" AGMs and GELs need it worse as they do not get over charged or EQed like FLAs do. So FLAs sort of get balanced by constantly over charging every one. I to would like to see an affordable battery balancer. I can not wait to buy a set up off Ross and be able to keep an eye on this new set of Trojan L16s. (Ross I assume they will do 6v cells?)

Ryan

[tecnodave]

Ryan,

Ross's work is on separately monitoring each cell individually as such it is not applicable to 6 volt sealed top batteries but only individual cells. From his postings it is capable of monitoring other voltage individual cells as well but with a maximum of 5.00 volts per cell.

David

[zoneblue]

Back in the day when i worked on aircraft, the wet nicad chargers we used in annual battery pack servicing  incorperated a rudimentaty cell balance check. It consisted of a single alligator clip you clipped onto the midpoint of the bank, as the bank cycled. I guess it assumed that it would be unlikely that a cell on one half of the bank would fail at exactly the same time as a cell  on the other half of the bank.

So even though monitoring a 6v cell is not ideal, it should still give some useful indications. However i know the tight parameters Ross was working to in order to get the resolution up.

[RossW]

Ryan,

Ross's work is on separately monitoring each cell individually as such it is not applicable to 6 volt sealed top batteries but only individual cells. From his postings it is capable of monitoring other voltage individual cells as well but with a maximum of 5.00 volts per cell.

The original design was limited to 5V peak cell voltage, however Ryan isn't the first to ask for a 6V version.
I've worked out how to make a board operate correctly with 6V "cells" without requiring an entirely new board, yet the rest of the functions will work the same. With all the extra stuff I've put in the code, I've run out of space for it to be the same code just detecting which mode its running in, but will be announcing the 6V version shortly.

[Halfcrazy]

Sweet. Let me know where to send the beer money to!

[tecnodave]

RossW,

I have been reading your threads from the start, very impressive work, I'm interested as I am using 6 volt L-16's

tecno

[RossW]

I have been reading your threads from the start, very impressive work, I'm interested as I am using 6 volt L-16's

Thanks. I've been sitting on my hands basically, waiting on bits to complete the next lot of boards. (Ordered enough for 100 boards or board-equivalents)

When I get the immediate commitments done and out the door (waves to Watt and TomW!) I'll do the 6V single-cell module. It's really just a case of leaving off 2 components, adding a jumper, and an adaptation of the code. (Most of it is unchanged, so hopefully able to knock it over if I get a couple of hours to dedicate to it)