Used AGM batteries dilemma

SolarT
SolarT Solar Expert Posts: 49 ✭
in Off Grid Solar & Battery Systems #1
I am looking at two pairs of batteries. Each has 2 AGM rated 100Ah@20hr. Below are the spec and condition and price. I am not sure which one to go for.
Brand new never charged AGM from Trojan sitting in its box for about 2 years - manuf date July 2009 ~ $175
Used for data center C&D UPS batteries float charged for 3+ years with 2 minutes activation - manuf date Dec 2007 ~ $129

Price of the UPS batteries are negotiable. Trojan are less negotiable.

Which one should I go for? Or bite the bullet and buy brand new. Any advice would be appreciated.
· Share on Twitter

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Used AGM batteries dilemma

    if i read this correctly the c&d was kept up with a float charge and that would be the one to go for of the 2. the trojan most likely has lost some capacity and would be a high risk in my opinion. don't get me wrong as any used battery has some risk to it, but one without a float charge for 2 years may even be dead.
    · Share on Twitter
  • SolarT
    SolarT Solar Expert Posts: 49 ✭
    #3
    Re: Used AGM batteries dilemma

    Thanks Niel, I had the feeling the the C&D is a better buy because of the constant float charge. Trojan might have lost capacity due to sulphation. Trojan guy would not give me a voltage on the batt.
    · Share on Twitter
  • keyturbocars
    keyturbocars Solar Expert Posts: 375 ✭✭
    #4
    Re: Used AGM batteries dilemma

    I would definitely stay way (FAR AWAY) from those Trojan AGM's that sat idle for 2 years! I bought some Lifeline AGM's that were "new", but sat for 2+ years, but they have been trouble ever since because of sulfation.

    The C&D batteries are probably meant to be kept in float mode and not subject to frequent deep discharges. From what I've read, a lot of these telecom batteries do not have a long life expectancy if you frequently discharge/charge them. I'd recommend looking up the spec sheet on those C&D batteries and see the number of cycles for which they rate them.

    Edward
    · Share on Twitter
  • SolarT
    SolarT Solar Expert Posts: 49 ✭
    #5
    Re: Used AGM batteries dilemma

    Unfortunately it does not list the charge/discharge cycle but it does list 10year design life at 77F. Dynasty UPS batteries may be stored up to 6 months @ 77F and then a refreshening (Equalizing?) charge is required.

    I have a pair of used AGM and they do work. I am sure they have sulphation. But they go in absorption mode when the sun peaks around 1pm. So I am thinking a diversion charge using a relay to a second pair to take advantage of the sun. Otherwise the 315W panel will be cranked down to about 60W when float starts. About 2 hours before absorption mode I turned on 2 large fans and 2 small tank pumps for about 5 hours and it delays the absorption mode about an hour or two.
    · Share on Twitter
  • System2
    System2 Posts: 6,290 admin
    #6
    Re: Used AGM batteries dilemma

    FWIW, I'd always go with lead-acid, never AGM or gel cells, for the simple reason that they can be easily rebuilt after a collapse. They're also the cheapest form of electrical storage known to man. That's what we use in our 5 kw system, or, for that matter, all our systems. Normally Deka, made by East Penn in Pennsylvania, but occasionally Interstate. 235 amp hours for $115 per 6 volt battery are numbers we like.
    · Share on Twitter
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #7
    Re: Used AGM batteries dilemma
    SoundWisdom wrote: »
    FWIW, I'd always go with lead-acid, never AGM or gel cells, for the simple reason that they can be easily rebuilt after a collapse. They're also the cheapest form of electrical storage known to man. That's what we use in our 5 kw system, or, for that matter, all our systems. Normally Deka, made by East Penn in Pennsylvania, but occasionally Interstate. 235 amp hours for $115 per 6 volt battery are numbers we like.
    AGM and gelled ARE Lead-Acid.
    · Share on Twitter
  • SolarT
    SolarT Solar Expert Posts: 49 ✭
    #8
    Re: Used AGM batteries dilemma

    Like WindSun said flooded, AGM and Gel are all lead acid batteries. Just different form of acid in the batteries. Liquid/paste, absorb glass mat and gel for acid.

    The advantage of AGM is no mess to deal with if you follow the manufacturers spec for charging. Must keep charge voltage to spec and no equaliztion. It also has regulated valve (VRLA). The downside is you can not determine the state of charge with hydrometer. Instead it will need a battery monitor. I am still trying to figure out my XBM (battery monitor).

    Flooded battery you can at least get the SG from the hydrometer to get a decent state of charge. I can tell you that I pulled out both my car batteries because the cells have different SGs. I am charging & equalizing them with my 4 stage Xantrex charger.

    In the future, I might try two brand new Trojan T105 batteries for the same price. And they are flooded batteries. I think I am going to hold off getting used ones for now till I figure out my XBM. I have ordered the Smartgauge from the UK for comparison. I think they are going crazy over the Royal Wedding over there - I have not heard from them yet.
    · Share on Twitter
  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    #9
    Re: Used AGM batteries dilemma

    $129 is a little high for that battery. I see them all the time in the $50 to $75 range. Keep looking you'll find a better deal on used batteries.
    Larry
    · Share on Twitter

Categories