Newbie questions

System
System Posts: 2,511 admin
Hello folks

I am not new to Rvs or solar stuff as i have .5 KW on the roof of RV but I just had a C-40 controller put in with a digital read out. The fellow that put my system in used twin 10 Guage silver wire to charge my batteries from the panel array.

there are different read outs on the digital monitor. I know I need to buy 6 batteries as mine are tired after 5 years and a drain mishap but I need to know what to make of the readings. Volts, watts, total AH and used AH's? Help.. thank you

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie questions

    The typical charge controller may have lots of interesting logging functions of voltage, current, power, AH, etc... However, this is really only the output energy of the charge controller. And, for an Off-Grid / Battery Based system, a set of panels+controller can usually output more power than the battery and loads can absorb--So, the numbers from the controller is sort of difficult to make much sense from.

    The "better way" (in my every so humble opinion) is the make the "battery bank" the center of your system. Measure the voltage, current, time in/out of the battery so that you can treat it right.

    Other than using a hydrometer (and measuring the resting voltage of a battery bank), the easy way is to measure Amp*Hours in/out of the battery so you can estimate the state of charge just from a glance at a Battery Monitor (Victron also makes a battery monitor that a few folks here really like).

    To check your loads, you can use an AC Watt*Hour meter like the Kill-a-Watt meter. For DC loads, using an Amp*Hour / Watt*Hour meter like one of these can be helpful.

    There are a couple of battery FAQ's that are worth reading--if you have not seen one before:

    Deep Cycle Battery FAQ
    www.batteryfaq.org

    There are lots of discussions about how best to treat a battery bank around here (lots and lots of threads). How best to treat your battery bank? Here is my slice of understanding:
    BB. wrote: »
    From what I have seen, the "gadgets" that do improve battery life/performance/efficiency:
    1. Remote Battery Temperature Sensor equipped Charge Controllers (both solar and grid powered).
    2. Battery Monitor--Allows owner to monitor battery capacity 24x7 without needing a hydrometer or resting batteries for a few hours and using a DMM to measure voltage.
    3. AGM Batteries: Much more efficient than flooded cell batteries (very little/no equalization necessary.
    4. Following Manufacturer's instructions: Minimum/maximum charging current, equalization per instructions (even AGM's should probably have a light equalization once or twice a year to ensure all cells are fully/equally charged).
    5. Not letting batteries sit for days+ at lower than 75% state of charge (prevent sulfates from hardening--one AGM mfg. claims that their batteries do not experience sulfate hardening--don't know if this is a feature of their battery or all AGM's--but would not like to test this on my battery bank--if I had one).
    6. Checking water levels and keeping properly filled with distilled water.
    7. Aftermarket Battery Caps: Can help keep battery cleaner/use less water.
    8. AGM batteries: Much more efficient and cleaner to run.
    9. Enough Battery Charging Energy (solar panels, generator backup, alternative sources, etc.) to ensure that battery bank is not "deficit" charged (is recharged promptly back to have 75%-90% of capacity within hours/1 day).
    Would be interesting to hear anyone's experiences with a air/electrolyte mixing system... I could be convinced either way (although, such a system probably needs to be designed into the battery rather than just an aftermarket add-on).
    I learned this strategy from Dave Surrette (Rolls) in the late 70's. Pretty much the bible on how I design my systems for off-grid.

    Assume that the system will never reach more than a 90% state of charge.

    Try not to go below 50% SOC, ever! Complete absorption over 90% of the year.

    Use the energy stored from 70% to 90% SOC for your daily cycles.
    Save the energy from 50% SOC to 70% SOC for aging to get long battery life.

    I know Surettes has changed their recommendations over the years but I also know they are in the business of selling batteries! If you do the above you will get 10 to 15 years on their batteries with decent maintenance.

    The OP is making it complicated by mixing battery types and not really stating a lot of information that would allow decent specific advice.

    Oh yea, I am really happy that Surrette and Trojan are making L16's with 1000 AH capacities @20HR. Been bugging them for many moons to do batteries less than 125LB's!

    And, my two cents... If your batteries are using a bit of distilled water per month--you are probably OK. If you are using none, or a lot per month--then you are probably under or over charging.
    • Undercharging and operating for long periods (below ~75%) is damaging to lead acid batteries.
    • Overcharging is less damaging to flooded cell batteries (at the cost of distilled water and wasted energy).
    • Overcharging sealed batteries (AGM, Gel, VRLA, etc.) can be fatal to those types (venting electrolyte).
    From Trojan's battery manual (PDF):
    Equalizing (flooded/wet batteries ONLY) 3.4.2.

    Equalizing is an overcharge performed on flooded/wet batteries after they have been fully charged. Trojan recommends equalizing only when batteries have low specific gravity, below 1.250 or wide ranging specific gravity, 0.030, after fully charging a battery. Gel or AGM batteries should never be equalized.
    • Confirm that the batteries are flooded/wet
    • Check electrolyte level to make sure plates are covered with water before charging
    • Check that all vent caps are secured properly on the battery before charging
    • Set charger to equalizing mode
    • The batteries will gas (bubble) during the equalization process
    • Measure the specific gravity every hour. Discontinue the equalization charge when the gravity no longer rises
    WARNING: Do not equalize gel or AGM batteries
    As always, try to get as much information from the battery manufacturer on what voltage/current/time/etc. the recommend for their battery systems.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Newbie questions
    NEVERSWEAT wrote: »
    ...... The fellow that put my system in used twin 10 Guage silver wire to charge my batteries from the panel array. ......


    I'd look into that a bit more, silver wire, while the very best conductor, is VERY expensive, and I suspect it's actually aluminum wire, and may not play well with the rest of your things, unless it has the right torque and goop applied.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Newbie questions

    The wire may be tin plated copper wire or, possibly, silver plated copper wire (but that probably both rare and expensive).

    Aluminum wire is a possibility if the RV is over ~30 years old--but probably only seen in the AC wiring (I am guessing).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    Re: Newbie questions

    My vote is on tinned copper. I assume it is stranded wire. Do they even make stranded aluminum?
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Newbie questions

    They do (did) make stranded aluminum at least in sized from ~#8 and larger.

    Tony