3 stage charger for RV with solar system

jackbombayjackbombay Solar Expert Posts: 46
I have a small solar system set up on my sprinter conversion van, 135 watt panel and with a prostar 30 amp charge controller and a 200 AH AGM battery. I want to instal a 3 stage charger, but want to make sure I don't need something specific to play nice with the solar system. I was looking at this charger, http://www.amazon.com/SEC-1215UL-ADVANCED-AUTOMATIC-BATTERY-CHARGER/dp/B00BMU7YPG/ref=sr_1_1?ie=UTF8&qid=1403364006&sr=8-1&keywords=Samlex+SEC-1215UL

Will that work fine with what I have?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 3 stage charger for RV with solar system

    Not a problem.
    Other than some small 'disagreements' about Voltage, set points, and charge stage multiple charge sources work together. I don't have any experience with the Samlex charger, but their other equipment is decent.

    You have only one 135 Watt panel, so why do you have a 30 Amp charge controller? Room for expansion? At about 7 Amps that set-up isn't going to do much for 200 Amp hours of battery. The plug-in charger I'd say is a must-have.
  • BB.BB. Super Moderators, Administrators Posts: 30,190 admin
    Re: 3 stage charger for RV with solar system

    Should be fine...

    15 amps is a bit small if you want to "quick charge" from a generator or AC shore power--But for floating at home/relatively low power usage from your battery system (i.e., if long term DC loads are less than 15 amps)--It will work fine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: 3 stage charger for RV with solar system

    I've got that very same charger headed my way.

    Personally, I've found that when dealing with agm's, conventional ones at least like East Penn / Deka, when you get below about 0.1C charge current, you are entering into a "maintainer" category, rather than a charger, and may encounter more of a surface charge than a decent deep-pore charge.

    I'd recommend upping that to the 30A version for your 200ah agm.

    My main interest is using the switchable 14.4 / 14.0v absorb for my LiFePo4 banks, which is covered elsewhere. We'll see when it gets here. My other Samlex inverters have been of general high quality, so I'm looking forward to seeing how this compares.
  • jackbombayjackbombay Solar Expert Posts: 46
    Re: 3 stage charger for RV with solar system
    Not a problem.
    Other than some small 'disagreements' about Voltage, set points, and charge stage multiple charge sources work together.

    Good to hear, thanks :-)
    You have only one 135 Watt panel, so why do you have a 30 Amp charge controller? Room for expansion? At about 7 Amps that set-up isn't going to do much for 200 Amp hours of battery. The plug-in charger I'd say is a must-have.

    This time of year I have seen as much as 9.6 amps of charge (cool weather and high altitude) but I do currently have way more charge controller than I need. You are spot on though, room for expansion, I will be installing another 135 watt panel soon. The single 135 was usually enough for us, but in the spring and fall the battery/charger rarely hit float voltage.
    BB. wrote: »
    Should be fine...

    15 amps is a bit small if you want to "quick charge" from a generator or AC shore power--But for floating at home/relatively low power usage from your battery system (i.e., if long term DC loads are less than 15 amps)--It will work fine.

    -Bill

    Not looking for a quick charge all that much, we won't plug in all that often, but there are some possibilities for plugging in for extend times in shady areas.
    PNjunction wrote: »
    I've got that very same charger headed my way.

    Personally, I've found that when dealing with agm's, conventional ones at least like East Penn / Deka, when you get below about 0.1C charge current, you are entering into a "maintainer" category, rather than a charger, and may encounter more of a surface charge than a decent deep-pore charge.

    I'd recommend upping that to the 30A version for your 200ah agm.

    This is something I had not considered, and something I didn't know about. Will long term charging at less than .1C hurt the battery? I purchased the battery form NAWS and asked them about charge rate and they said it shouldn't be over 30 amps (%15 of battery capacity) but I didn't ask about minimum charge rates.

    The 30 amp Samlex isn't too much more money and if the higher charge rate will extend the life of the battery I'll gladly pay it, being able to quick charge the battery could certainly be useful at times too.
    PNjunction wrote: »
    My other Samlex inverters have been of general high quality, so I'm looking forward to seeing how this compares.

    Good to hear it!
  • BB.BB. Super Moderators, Administrators Posts: 30,190 admin
    Re: 3 stage charger for RV with solar system

    It also depends on the size of your AC power source(s) too... If you are charging from 120 VAC utility power--A larger charger is no problem.

    If you are going to have a Honda eu1000i -- Then a 30 charge controller may be a bit large. If you have a Honda eu2000i or larger/similar genset--Then you can should be able to charge at ~40 amps + 12 volts without problems.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 3 stage charger for RV with solar system
    BB. wrote: »
    It also depends on the size of your AC power source(s) too... If you are charging from 120 VAC utility power--A larger charger is no problem.

    If you are going to have a Honda eu1000i -- Then a 30 charge controller may be a bit large. If you have a Honda eu2000i or larger/similar genset--Then you can should be able to charge at ~40 amps + 12 volts without problems.

    -Bill

    Depending on what else the generator must run at the same time.

    Regarding charge rates, I am running some experiments on this with my own batteries. Higher current over shorter time, it would appear, is not desirable. It seems too much of the energy goes into heat and not enough to charging. Tests have not been completed yet and on the basis of only one example I wouldn't draw any conclusions anyway.
  • jackbombayjackbombay Solar Expert Posts: 46
    Re: 3 stage charger for RV with solar system
    BB. wrote: »
    It also depends on the size of your AC power source(s) too... If you are charging from 120 VAC utility power--A larger charger is no problem.

    If you are going to have a Honda eu1000i -- Then a 30 charge controller may be a bit large. If you have a Honda eu2000i or larger/similar genset--Then you can should be able to charge at ~40 amps + 12 volts without problems.

    -Bill

    No generator typically, but we may end up with a honda at some point, a 2000.
    Depending on what else the generator must run at the same time.

    Regarding charge rates, I am running some experiments on this with my own batteries. Higher current over shorter time, it would appear, is not desirable. It seems too much of the energy goes into heat and not enough to charging. Tests have not been completed yet and on the basis of only one example I wouldn't draw any conclusions anyway.

    If I'm plugged in I'm not too worried about the efficiency of the charging, it seems that higher charge rates could help the battery according to this link http://www.powerstream.com/SLA-fast-charge.htm

    Hmmmm, back to google!
  • BB.BB. Super Moderators, Administrators Posts: 30,190 admin
    Re: 3 stage charger for RV with solar system

    Trojan (for one) recommends a 10% minimum rate of charge (last I checked).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jackbombayjackbombay Solar Expert Posts: 46
    Re: 3 stage charger for RV with solar system
    BB. wrote: »
    Trojan (for one) recommends a 10% minimum rate of charge (last I checked).

    -Bill

    Boy, they sure do, http://www.trojanbattery.com/pdf/U.S.%20Battery%20Charge%20Profile%20Full%20%2011-12-13.pdf

    I'll buy the 30 Amp charger.


    Thanks for the feedback and information guys :-)
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: 3 stage charger for RV with solar system

    Typically most conventional AGM's have about a 0.25C to 0.33C max charge rate. The advantage of getting it close to the max (East Penn / Deka recommends this) is not only to get a deep-pore charge, but also to charge fast enough to help ensure that you finish absorb, and get at least 8-24 hours of float time in.

    Some manufacturers say that float is "optional", and certainly, long term storage under cool conditions without a parasitic load you don't need to float an AGM.

    However, if we take a big hint from the Enersys / Odyssey playbook, getting at least 8 hours or more of float is crucial for agm longevity. Practically speaking, many of us can't do that when cycling on a daily basis, but if you charge close to the max rate, you better your odds of getting *some* good float time in. Of course it would also be ridiculous to run a genny for 8 hours doing float and wasting fuel!

    The very bad analogy here is that with agm, by not getting in enough float time, it is like having plaque under your gumline. Sure, you seem to brush 99.99% clean every day, but that .01% over time, hardens / sulfates and the overall percentage increases too. Whether this is enough to beat the clock under just normal aging of the battery itself depends on your situation.

    So I'm trying to keep it real and recognize that many hours of float is often impossible in our situation. BUT, still according to both Enersys and East-Penn, finishing absorb quick enough without going past the max charge current limits, will get you to float faster, which is good for AGM. This is actually a common-misunderstanding regarding Enersys AGM's, that in their manual specify a minimum of 0.4C, which is not primarily a normal charge issue, but one of TIME to get you to float fast - a holdover from the go-go EV days of 1998 or so...

    In my portable case with agm's, before storage, I always make sure that I have not only completed absorb, but have about 24 hours of float on them before storing. If I can afford a day of downtime with low demand loads, I'll spend the whole day doing nothing but float - as much as that makes me crazy with all the panel power wasted. :)
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: 3 stage charger for RV with solar system

    If one is doing daily cycling of any consequence, and you reach float, but have very little time to remain in float due to lack of solar insolation, the easiest compensation is to just extend your elevated voltage absorb time. You can do this by setting your float voltage to the same value as your absorb voltage.

    This still doesn't relieve you of many hours of float, but it does shorten it quite a bit. As long as you aren't exceeding a manufacturer's timeout limit for the absorb period, you should be better off, although we'll never usually reach the ideal amount of float for daily solar cycling. If you aren't cycling daily, then I'd set my float to the normal lower voltage value.

    This compensation relieves one of having to calculate "end amps" and the like. Just set your float voltage to the absorb voltage, and let the sun set turn off the switch. :)

    This is one reason I prefer charge controllers that will actually let me change the float voltage somewhere near the absorb setpoint. In the case of a Xantrex C12 that I use, it has a one-hour absorb timeout. Setting the float voltage the same as absorb helps assure that I will finish absorb, and hopefully compensate for the lack of a long float time by extending the absorb time. The sun sets long before I exceed the manufacturer's absorb timeout limitation. But this trick is used for daily cycling - if it is not cycling daily, then I set float back to the normal value.

    If you are running small loads during the charge, you may be doing an extended absorb unintentionally anyway, which the sun will take care of eventually, but if you are using an AC charger which has the float and absorb voltages set the same, you've GOT to keep an eye out on the time limitation - not to mention that your loads will be seeing the absorb voltage most of the time, which in some cases is not ideal.
  • jackbombayjackbombay Solar Expert Posts: 46
    Re: 3 stage charger for RV with solar system

    Thanks for the info, your posts helped a lot at helping me understand how to keep everything working happily together :-)
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