Solar Controller - Multiple Batteries?

Hello Friends,

I just purchased a ... 205w 27v solar panel (http://www.solarhome.org/rec205wmodulerec205ae-ussilver.aspx) and was looking for a solar controller for it.

I have a 120v battery charger now. It has 3+ and 1 negative connector to allow 3 differernt batteries to be charged at a time without worrying about sending too much to one battery at a time (I think that's the way to word it).

My plan is two havef four new 6v batteries in a series (to create 12v - if series is the correct word) and then 2-12v batteries that are a year old.

My question is - is it possible to get a controller to take the juice from the solar panel i just purchased and have 3 outputs like i do on my 120v system.

My plan for this is i live on a boat and i want one battery to be a engine battery. 1 battery to be a backup and the 4 6v batteries to be house.... the "backup" will most likely be used as a house but i wanna see how i do with the 4-6v batteries.

Thanks,
I'm hope this messages makes sense....
-Anthony

Comments

  • azrc
    azrc Solar Expert Posts: 43
    Re: Solar Controller - Mulitpal Battteries?
    killhower wrote: »
    My plan is two have four new 6v batteries in a series (to create 12v

    4-6v batteries would make 24v. I think you'll have to charge each battery (taking the series of 6v batteries to be a single set) individually as each will will be in a different state of discharge, eg, the house set might be fairly discharged, while the motor and backup batteries will just need a float charge.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Controller - Mulitpal Battteries?

    Well... it will be 2-6v series *2 .... to make 2-12v banks... if thats possible...
    thanks,
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Solar Controller - Mulitpal Battteries?

    Yes, the correct terminology would be "two parallel strings of 6v batteries in series".

    There are some solar charge controllers that can handle multiple battery banks. They can get expensive. A simple one that is probably about the cheapest is the SunSaver Duo:

    http://store.solar-electric.com/modubachco25.html

    You could use that to charge the main bank and also to keep the engine battery topped off. Then you could use something like the Xantrex Echo Charge or the Ample Power Eliminator to keep the backup battery topped off:

    http://store.solar-electric.com/echo-charger.html

    http://www.amplepower.com/products/elim/index.html
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Controller - Mulitpal Battteries?

    you may have a problem in charging that many batteries with the 1 pv. i'm guessing the 6v batteries to be 220ah and to series/parallel them as you wish would create a 12v 440ah battery bank. at a minimum you'll need for bulk charging 5% and more than likely a 10% rate, but no more than a 13% rate. you are looking at 22a minimum from solar. if added to the other charger it could just add to it. you may find it easier to use a switch to allow for whatever batteries you wish to charge as to do all batteries at the same time will show the charge to be nearer a float level.

    seeing the high vmp on the pv may warrant an mppt controller to better reap the power of that pv for 12v. if you add more pvs then you may need a higher current model, but as it is a sunsaver mppt (15a) will work, but another option may be a rogue mppt (30a non certified) controller.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Controller - Mulitpal Battteries?

    Thanks for the advice.

    The idea is that i will have battery bank for storage and hopefully just use a little bit of the batteries every day and have the extra storage for days in which the solar panels aren't putting out too much power.

    Luckily for me the place i got my solar panel from called and told me that they are out of stock and can't find me anything simliar... fantastic.

    So any advice on a solar panel around 200w's or panels that could produce that output? I was only paying $500 for this one and found simliar sites offering the same panel for $530.

    -I just found this one http://www.solarhome.org/sunwizesw100c100watt16voltnominalsolarmodule.aspx that i could get 2...

    am i mis-understanding something or couldn't I use 2 of these 100w (16v) panel
    with a mppt to charge a 12v battery bank?
    Thanks for everything world wide wild web,
    -Anthony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Controller - Mulitpal Battteries?

    you could do it that way and many other ways, but my point was only what might work for you in keeping a charge on the batteries and 200w just isn't enough to charge the batteries properly. it may offset some power used, but will not give it a full charge even with an mppt controller optimizing the current and voltage.
    now maybe i'm misunderstanding you. if by storage you mean the solar will be called upon to float charge the batteries then you need about 1%-2% or so for the charge rate, but that's with no usage. to employ solar to charge up the batteries with some usage everyday then you need far more solar. if this is the case then it is difficult to nail this all down for you as you want to get the use of the batteries and yet only want to float charge them. i might suggest if it is a float case with small short loads to try just shy of the 5% charge rate, but no less than 4% to see if that suffices for your needs, but be prepared to possibly need more pv depending on the loads you have in mind and their duration.
  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    Re: Solar Controller - Multiple Batteries?
    killhower wrote: »
    Hello Friends,

    I just purchased a ... 205w 27v solar panel (http://www.solarhome.org/rec205wmodulerec205ae-ussilver.aspx) and was looking for a solar controller for it.

    What makes the other version of this panel half the cost, for the same power?
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Controller - Mulitpal Battteries?

    I'm way too knew to this to completly understand what i'm doing i think hahaha.

    A couple of friends of mine told me that about 300watts would be good enough for their boat (which is way more power draw then mine) Other people then aggreed with them and said 300w was more then enough. Budget cuts now has me shooting for 200w haha.

    What i'll be using the batteries
    -running a 12v refridgertor drawing about 2.5amps/24hr
    -boat lights outside drawing .5amp 12hr a day
    -interior boat lights - ~.5amp at most 8 hr a day
    -more lights - .5amps/
    -car radio - not sure about ampage on this one
    -led LCD monitor - at most 3 hours a day (i dont really watch tv)
    -vhf radio - randomly - not sure
    -etc etc etc

    Not that much. Maybe their calculations are wrong or something but this is what i was going with...

    The main power draw is going to be comeing from the refridgerator and my anchor light.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Solar Controller - Mulitpal Battteries?
    killhower wrote: »
    -running a 12v refridgertor drawing about 2.5amps/24hr

    2.5a x 24h = 60ah (amp*hours) OUT of the battery every day.

    200w (panel) / 14.4v (battery charging voltage) = 13.9a

    Figure 4 hours of good sun per day (straight down on the PV panels) that would be a harvest of:

    13.9a x 4h = 55.6ah

    Which would *almost* be enough to run your fridge for 24 hours...


    But it's actually worse than that, since the battery isn't 100% efficient at absorbing, so figure you would probably end up putting more like 45a-50a actually into the battery.


    Around 50ah per day is your power budget with 200w of PV.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Controller - Mulitpal Battteries?
    killhower wrote: »
    I'm way too knew to this to completly understand what i'm doing i think hahaha.

    A couple of friends of mine told me that about 300watts would be good enough for their boat (which is way more power draw then mine) Other people then aggreed with them and said 300w was more then enough. Budget cuts now has me shooting for 200w haha.

    What i'll be using the batteries
    -running a 12v refridgertor drawing about 2.5amps/24hr
    -boat lights outside drawing .5amp 12hr a day
    -interior boat lights - ~.5amp at most 8 hr a day
    -more lights - .5amps/
    -car radio - not sure about ampage on this one
    -led LCD monitor - at most 3 hours a day (i dont really watch tv)
    -vhf radio - randomly - not sure
    -etc etc etc

    Not that much. Maybe their calculations are wrong or something but this is what i was going with...

    The main power draw is going to be comeing from the refridgerator and my anchor light.

    others can picture me pulling my hair out.:cry:

    not only do you not have just a small load, but a plethora of things operating.:roll:

    -running a 12v refridgertor drawing about 2.5amps/24hr
    2.5a x 34% duty cycle x 24 hrs = 20.4ah guessing
    -boat lights outside drawing .5amp 12hr a day
    .5a x 12hrs = 6ah
    -interior boat lights - ~.5amp at most 8 hr a day
    .5a x 8hrs = 4ah
    -more lights - .5amps/
    .5a x assumed 2hrs = 1ah
    -car radio - not sure about ampage on this one
    roughly 1a x assumed 2hrs = 2ah
    -led LCD monitor - at most 3 hours a day (i dont really watch tv)
    size and power draw unknown if used so i will say no use and 0ah
    -vhf radio - randomly - not sure
    at least 1a draw on rx 95% of time and tx 5a guessing 5% of time
    1a x .95 x 24hrs = 22.8ah
    plus
    5a x .05 x 24hrs = 6ah
    totaling 28.8ah

    -etc etc etc
    expansion and misc 2a x 2hrs = 4ah

    grand total of 66.2ah
    66.2/440ah=15% dod per day and 66.2ah / 90% pv efficiency / 80% battery efficiency is about 92ah needed to just replace what has been drawn. over a 5hr full sun period per day this is 92ah/5hr=18.4a from pvs or 4.2% of the battery capacity and does not account for other electrical losses in addition to foggy or rainy periods. you better try to get as close to the 10% rate as you can, but even the 5% minimum would be too close and pushing it with your requirements.

    the advice others give you is not a very educated piece of advice and they most likely won't keep their batteries for very long. i am pushing it in saying i would not feel easy with less than 25a from pvs in this application and i'd possibly say more is needed. 25a x 14.5v = 363w in pvs for starters.
    edit to add: if the loads are on while charging then you will need even more pvs so that it will not go below the 5% minimum charge rate.