Universal Batteries UB-8D AGM batteries, almost 5 years later, an opinion

Les Nagy
Les Nagy Solar Expert Posts: 121 ✭✭
I have been running a battery bank of 12 Universal Battery UB-8D batteries for 4 years now. They were/are amongst the least expensive AGM high capacity batteries available. They are rated at 12V 250AH. They cost as little as around $430 each plus delivery. I live in the high desert in Chile, the Atacama Desert at 2500m/8000ft altitude so AGMs offer many benefits. The biggest benefit is the shipping issue. AGMs have no restrictions of shipping. The second benefit is the lack of need to add water in such a dry environment.

The build quality has been adequate and I have had no problems with the cases nor the terminals. The internals remain invisible so I cannot comment of the internal construction.

I have been running my batteries with a three stage charge cycle using a a Xantrex MPPT60-150 solar charge controller using the manufacturer's recommended voltages. The first couple of weeks I heard some squealing noise so I reduced the voltage a bit to stop any possible overpressure leaking of water. The batteries have been working well for four years with one change of the arrangement of the batteries to try and balance the strings. The batteries are arranged in four serial by three parallel to proved a 48V battery pile.

The past four months I have noticed a faster degradation of the capacity of the batteries when the bank voltage has been dropping much faster than the past four years. After repeated measurement of voltages of the batteries over a few days at different stages of charge and use, it became obvious that one battery had failed completely, and two others had diminished capacity beyond the other remaining good batteries. The one completely bad battery will not hold a charge and falls to less than 11V after one day of resting. The other two still hold a charge and after two days still read in around of 12.7V. I have removed one string from the pile.

For the past week, the remaining eight batteries, four serial by two parallel, have been performing very well and it is like I have almost a new battery bank. OK, not new but very good again. The unconnected battery that is still good is still holding a better than good voltage of close to 13V.

So my conclusion:

These are the least expensive AGM batteries at this capacity that are available. They cost around 60% of the other highly regarded name brands. They have lasted around 60% the lifetime of what the best I have seen the other brands reported to last. Most of the reports of the other brands do not involve 2500m/8000ft altitude so there might be some discrepancy to the comparison. I suspect that my initial possible out gassing overpressure might be related to my altitude. I have 75% the atmospheric pressure of that at sea level. So given the above facts I would conclude that Universal Battery UB-8D AGM 250AH batteries are at least as good a buy as the other more expensive brands.

This conclusion has to be weighed against my extreme conditions here, the more frequent cost of transport and labor to change to batteries, but I think they are a worthy buy and worthy of consideration for anyone looking for AGM batteries. Some people will be more comfortable paying the big bucks for brand name products but these are not a waste of money at least, and are IMHO at least the equal in value per $ to the other brands.

Questions, insults, opinions, rants, all are welcome.

Comments

  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    Re: Universal Batteries UB-8D AGM batteries, 4 years later, an opinion

    Nagy,

    That is useful information and I would more or less confirm your findings. I got about 10 of those G8 agm batteries that weight around 150lbs each from o ship. That was about three years ago. Their age was unknown when I recieved them but they are still running now and they undergo daily cycling at an installation that I completed nearly 3yrs ago.

    Cheers...
    Damani
  • Les Nagy
    Les Nagy Solar Expert Posts: 121 ✭✭
    Re: Universal Batteries UB-8D AGM batteries, 4 years later, an opinion

    Since this post I have been running with the remaining eight batteries and all is fine. Two of the batteries fro the original 12 have proven to be bad. Both are down to 10.6V or lower after only a week of sitting. Yes they have been fully charged and cycled.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Universal Batteries UB-8D AGM batteries, 4 years later, an opinion
    Les Nagy wrote: »
    The past four months I have noticed a faster degradation of the capacity of the batteries when the bank voltage has been dropping much faster than the past four years.
    <snip>
    Questions, insults, opinions, rants, all are welcome
    OK, at your request, a mini rant:

    You are a good example to others about the extra work involved in maintaining parallel batteries. It's good that you noticed the discrepancy between the daily load and the daily voltage, and then took action to save two strings. Many folks don't take action until the lights go out (or for those with AGS, until the generator runs out of fuel).

    Among the many other pitfalls of parallel batteries is the rapidity of cascading failure as the parallel strings diverge in their electrical characteristics.

    One thing you could have done differently (other than avoid parallel batteries) is to periodically monitor your battery strings with a DC clamp ammeter. You will notice the charging discrepancies in your battery strings much sooner by measuring current in each string rather than by watching the voltage of the entire bank.

    There is a good, short discussion of parallel batteries here:
    http://www.wind-sun.com/ForumVB/showthread.php?14674
    By the way, all the problems associated with wiring parallel batteries are worse with AGM batteries than with flooded batteries, because AGM batteries have lower internal resistance.

    There is also a stochastic argument against parallel batteries. Half of all battery cells are above average, half below. When you put together a string of 24 cells to make a 48 volt battery, there is almost no chance that all your cells will be above average. In fact, the single weakest cell of those 24 will determine the life and capacity of the entire 24 cell battery.

    There are outliers among cells... occasionally you will get a really weak cell. That means occasionally you will get a 24 cell battery that barely makes it through warranty. Of course, in all multi-cell battery strings there is variation among the cells and you deal with that by charging the string until all of the cells are charged... that means overcharging most of them a bit. One thing for sure about a single string of cells: the charging current is the same in each cell.

    When you have three parallel strings, you have nearly tripled your chance of getting an outlier weak cell. Furthermore you have made it much more difficult to get all the cells charged because less current is flowing into the string that needs more current to charge.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Les Nagy
    Les Nagy Solar Expert Posts: 121 ✭✭
    Re: Universal Batteries UB-8D AGM batteries, 4 years later, an opinion

    Thanks for the feedback. Yes, keeping paralleled batteries balanced is a problem. Actually I did rearrange my batteries twice during their lifetime to try to keep things balanced. Perhaps I should have done it more frequently. The other issue that I had was the probably venting at the beginning of their life here which was probably because of my extreme altitude here of 2500m/8000ft. Perhaps the two dead batteries lost too much water at that point to last any longer than they did. My situation here is rather different than most people so my results for these batteries cannot be considered as representative of what would be considered normal conditions.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Universal Batteries UB-8D AGM batteries, 4 years later, an opinion

    Les - great hands-on user report!
    I have been running my batteries with a three stage charge cycle using a a Xantrex MPPT60-150 solar charge controller using the manufacturer's recommended voltages. The first couple of weeks I heard some squealing noise so I reduced the voltage a bit to stop any possible overpressure leaking of water.

    What exactly are those settings? Any chance a rogue "EQ" setting might be taking place? We can use the Brymen multimeter, turn off the auto-power off, and use the min/max to try and catch anything odd.
    The batteries are arranged in four serial by three parallel to proved a 48V battery pile.

    Were you able to charge each one individually first prior to placing them into their final configuration? This will help you start on the right foot in regards to balance, and also spot troublemakers. Is it possible that you had one or more that *may* have had poor internal construction, especially in regards to the vents themselves? While your altitude may have something to do with it, I think an interesting test would be to get hold of a new smaller UB agm battery for a sacrificial subject, charge it with the same settings of your charge controller, and see if that one vents prematurely.

    Again, I'm not trying to discount your experience - I'd just like to cover all bases so your next set doesn't have this happen.
  • Les Nagy
    Les Nagy Solar Expert Posts: 121 ✭✭
    Re: Universal Batteries UB-8D AGM batteries, 4 years later, an opinion

    The original setting suggested by the manufacturer were 59.2 volts for absorption and 54.8 for float. When I told them that I heard some squealing that indicated possible venting they suggest dropping and so I dropped to 58.8 and 54.4. Since that change there was no more squealing. The cases never did deform at all. The charging is done with a Xantrex MPPT60-150 with temperature sensor. No, I did not charge the batteries individually at the start as I am totally off grid, nada, zip, zero.

    EQ was never enabled. I did try short equalize this year to see if it would improve the balance but had no effect. There was no apparent venting during the short equalize.

    I strongly suspect that the possible venting at the beginning was the cause of the demise of the two batteries that have failed.

    I have been thinking of a possible power controller design to force parallel strings to balance but it would probably be very expensive for the size of the IGBTs that would be needed. The idea would be to put some current control on each string and force a balance. This is just thinking out loud right now and is probably highly impractical.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Universal Batteries UB-8D AGM batteries, 4 years later, an opinion
    Les Nagy wrote: »
    The charging is done with a Xantrex MPPT60-150 with temperature sensor. No, I did not charge the batteries individually at the start as I am totally off grid, nada, zip, zero.

    Ok. Interesting problem. I think in that situation where I had no choice but to install and charge, I'd force the Xantrex into bulk or float, skipping any absorb just to see if that would at least help from balance in the bulk stage alone. If nothing strange is happening, nor overheating, I'd bump it up again, but this time purposely to "GEL", which has a lower absorb. See how that goes - still the objective is not to fully charge, but to gently convince the cells to get their act together. I wouldn't be in a hurry to accomplish all this in one day.

    Then, if that is successful, I'd take it to the low range of the UB8D spec, in your case 54.8v absorb:
    http://upgi.com/Products/batteries.aspx?cat=12

    After all that, perhaps just leave absorb there, or move it up just to hair to 58.8 where you are having no problems. Basically I'd just walk-it-up and babysit for a few cycles.
    The idea would be to put some current control on each string and force a balance. This is just thinking out loud right now and is probably highly impractical.

    There are products that do that, but I dislike doing that as much as I would on my lifepo4's. :) I think that once they have proven themselves to be behaving after a walk-up session(s), and with the appropriate wiring infrastructure and followup monitoring, it would work for you.