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Samlex AC chargers for LiFePo4

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  • Samlex AC chargers for LiFePo4

    Just wanted to say that I'm extremely happy with the Samlex SEC lineup of Pb based chargers for my lifepo4 banks.

    I'm currently using a Samlex SEC-1215UL on both of my 20ah and 40ah GBS batteries and have not encountered any problems in over roughly 100 charge cycles. The yellow and black paint scheme makes it easy to spot.

    Note that I already have some Samlex power-supplies for my radio gear, but they emphatically state NOT to use these for battery charging, so I went with a dedicated charger, not a power supply. I'm not willing to take the risk, so ymmv if you try and put one of their normal power supplies into battery charging use.

    Even though they are designed for lead, they are dip switch settable for a GEL voltage, which in this case happens to be exactly 14.0v. That's about 3.5v per cell, which is fine. What made me smile is that at the end of charge, the Samlex was dead-on at 14.0v when measured at the battery terminals with my Fluke 87V. The old-school analog current meter is fun, although not exactly accurate, but good enough for a general indication. It is a switch-mode supply so it doesn't pull too much ac current.

    Fortunately, when it finishes the charge, it drops into float at 13.5v, which lifepo4 doesn't need, but this is well below 13.8v, so nothing is really happening. I just pull it when it is done, but I don't have to freak out about it.

    Running at only 14v also has the advantage of giving your cells some headroom if they are a bit out of balance. I personally don't run, nor believe in adding additional points of failure on a battery bank that once balance has been established, they stay that way since we are using them in a relatively low-current, low voltage environment, which is completely different from an EV. We are also not not pushing these things to the wall trying to scrape the last ounce of capability out of them.

    My HVD is the Samlex. My LVD is my brain - that is I either know how long I can run given my load current, or watch it with a coulomb counter and in any case I never drop below 12.8v, possibly NO MORE than 12.5v under a heavy load. That voltage is monitored by an inexpensive Fluke 115. This has all been hashed out before, and if you obey the manufacturer's spec sheets to the letter, you may not be running an optimized charge routine, so it pays to be a bit conservative. Since most large prismatics like GBS, CALB, etc can easily handle 1C charge current, I was tempted to try and match that with the Samlex lineup, but since I have the time, a lower powered charger is doing fine. Personally I wouldn't take it beyond 0.5C - 0.8C when charging.

    But when it comes to balancing with external bleed boards, or a rat's nest of BMS wiring - that is sooooo 2009! I have proven it to myself that external balancing is not needed, and the Samlex set to 14.0v, (or my little Xantrex C12 solar charge controller set to 13.9 for both absorb and float to compensate for the miniscule hour-long absorb timeout) is sufficient enough. The whole bleed-off balancing board issue has been covered for 5 years or more, and all I can say is I'm glad I'm NOT using them.

    I got my blue with purple top GBS cells from Batteryspace. There are others like Elitepowersolutions, and quite a few EV dealers. The only thing I did was get mine practically bare without any junk hanging off the 4 cells, although I did get them pre-strapped and wired with the appropriate cell links to make life easier. They were pretty well balanced as they came to me, although I did play just a little bit with an RV incandescent fixture to bleed off one cell that was a little high. Once that was done, I have never needed to touch it again. Keep them terminals-up.

    The Samlex makes doing that easy, even at 14v, which is just above the start of the steep charge knee. It is good enough. Just wait an hour to let the cells rest, and if one cell is too high, just pull it down for 20 seconds or so, discharge a bit to get back down into the flat part of the curve, and recharge and repeat the hour rest period. Use of a quality meter is highly recommended, although for balance, that may not be a big issue.

    At any rate, I was happy to find an off-the-shelf charger like the Samlex that didn't puke on lifepo4, or go beyond the stated voltage specs and rendering it useless.

  • #2
    Originally posted by PNjunction View Post
    Just wanted to say that I'm extremely happy with the Samlex SEC lineup of Pb based chargers for my lifepo4 banks.

    I'm currently using a Samlex SEC-1215UL on both of my 20ah and 40ah GBS batteries and have not encountered any problems in over roughly 100 charge cycles. The yellow and black paint scheme makes it easy to spot.

    Note that I already have some Samlex power-supplies for my radio gear, but they emphatically state NOT to use these for battery charging, so I went with a dedicated charger, not a power supply. I'm not willing to take the risk, so ymmv if you try and put one of their normal power supplies into battery charging use.

    Even though they are designed for lead, they are dip switch settable for a GEL voltage, which in this case happens to be exactly 14.0v. That's about 3.5v per cell, which is fine. What made me smile is that at the end of charge, the Samlex was dead-on at 14.0v when measured at the battery terminals with my Fluke 87V. The old-school analog current meter is fun, although not exactly accurate, but good enough for a general indication. It is a switch-mode supply so it doesn't pull too much ac current.

    Fortunately, when it finishes the charge, it drops into float at 13.5v, which lifepo4 doesn't need, but this is well below 13.8v, so nothing is really happening. I just pull it when it is done, but I don't have to freak out about it.

    Running at only 14v also has the advantage of giving your cells some headroom if they are a bit out of balance. I personally don't run, nor believe in adding additional points of failure on a battery bank that once balance has been established, they stay that way since we are using them in a relatively low-current, low voltage environment, which is completely different from an EV. We are also not not pushing these things to the wall trying to scrape the last ounce of capability out of them.

    My HVD is the Samlex. My LVD is my brain - that is I either know how long I can run given my load current, or watch it with a coulomb counter and in any case I never drop below 12.8v, possibly NO MORE than 12.5v under a heavy load. That voltage is monitored by an inexpensive Fluke 115. This has all been hashed out before, and if you obey the manufacturer's spec sheets to the letter, you may not be running an optimized charge routine, so it pays to be a bit conservative. Since most large prismatics like GBS, CALB, etc can easily handle 1C charge current, I was tempted to try and match that with the Samlex lineup, but since I have the time, a lower powered charger is doing fine. Personally I wouldn't take it beyond 0.5C - 0.8C when charging.

    But when it comes to balancing with external bleed boards, or a rat's nest of BMS wiring - that is sooooo 2009! I have proven it to myself that external balancing is not needed, and the Samlex set to 14.0v, (or my little Xantrex C12 solar charge controller set to 13.9 for both absorb and float to compensate for the miniscule hour-long absorb timeout) is sufficient enough. The whole bleed-off balancing board issue has been covered for 5 years or more, and all I can say is I'm glad I'm NOT using them.

    I got my blue with purple top GBS cells from Batteryspace. There are others like Elitepowersolutions, and quite a few EV dealers. The only thing I did was get mine practically bare without any junk hanging off the 4 cells, although I did get them pre-strapped and wired with the appropriate cell links to make life easier. They were pretty well balanced as they came to me, although I did play just a little bit with an RV incandescent fixture to bleed off one cell that was a little high. Once that was done, I have never needed to touch it again. Keep them terminals-up.

    The Samlex makes doing that easy, even at 14v, which is just above the start of the steep charge knee. It is good enough. Just wait an hour to let the cells rest, and if one cell is too high, just pull it down for 20 seconds or so, discharge a bit to get back down into the flat part of the curve, and recharge and repeat the hour rest period. Use of a quality meter is highly recommended, although for balance, that may not be a big issue.

    At any rate, I was happy to find an off-the-shelf charger like the Samlex that didn't puke on lifepo4, or go beyond the stated voltage specs and rendering it useless.
    Good info PN.

    Thanks for providing this information.

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    • #3
      PNjunction is fantastic on this stuff- many have benefited from his posts - Like Sun Eagle said, Thanks!
      [SIGPIC][/SIGPIC]

      Comment


      • #4
        Thanks - I'm glad I didn't get into these 5 years ago when one had to order directly from overseas, and a balancer was considered mandatory. Many totally overcharged and overdischarged them, yet they seemed to get away with it despite the inclusion of balancing boards. Early spec sheets didn't help matters.

        That is, until the abuse finally clogged the SEI layer, and the cells would basically die a digital on/off death of working fine one day, and dead as a doornail the next. Swollen cells should have been a big clue, but sometimes there was no swelling and the SEI layer just flipped the switch so to speak. Another reason to NEVER buy used cells.

        Even though I can't find these at my local automotive parts store, I don't have to deal directly overseas. Another outlet might be EAS or Electricautosports. Nice selection of GBS stuff pre-built, but of course I prefer mine practically naked, aside from straps and cell bus links. And batteryspace has hard to find individual cell-chargers that are larger than mere wall-warts if you want to go that route, especially with a random collection of cells, and not pre-built packs. Just be sure you get lifepo4, and not similar looking ones intended for a different chemistry like lico02 !

        The Samlex's ability to be set properly to 14v allows me to charge them as they should be treated - and not as a "drop in" replacement with unnecessarily high voltages from standard pb chargers. I didn't want 14.1 or 14.2, but 14 max. The Samlex provided that.

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