Battery Usage Question

Discussion in 'Off Grid Living' started by Maynard108, Mar 18, 2015.

  1. Maynard108

    Maynard108 Monkey

    I am new to the site, and also new to off grid living. I built a 526 sq. ft. house on 41 acres in central NY. I have 2 renergy 100 watt panels, a low to medium quality pwm charge controller, and a 428 amp hour deep cycle my question is; I use very little power (which is a good thing) but therefore my battery is always full or slightly not full. I think I recall reading somewhere that a battery should be ran down to extend it's life? I have very little means monitalrily and would like whatever I have invested in to last as long as it possibly can. I don't plan on returning to the rat race! I was wondering if anyone had experience with this, and am also very thankful for a site like this.
    Thanks in advance.
    Motomom34 likes this.
  2. oldawg

    oldawg Monkey+++

    Welcome to the tree! There are many monkeys here experienced in using solar. They'll be along shortly I'm sure.
  3. Maynard108

    Maynard108 Monkey

    Thank You!
  4. Dunerunner

    Dunerunner Brewery Monkey Moderator

    Welcome here!! What type battery? Deep Cycle RV Type lead acid? AGM?

    Deep Cycle Battery FAQ
    Last edited by a moderator: Mar 18, 2015
  5. Maynard108

    Maynard108 Monkey

    Great reference, it's a sealed marine. Nothing fancy the biggest everstart that Walmart carries, I know they're not ideal but I just want to take care of it as best I can.
  6. Dunerunner

    Dunerunner Brewery Monkey Moderator

    That link has the information you need about your starting battery.
  7. Maynard108

    Maynard108 Monkey

    Yeah, cycles vs lifespan told me exactly what I needed to know,
    Thanks so much!
  8. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Welcome to the Monkey Tree, Hope you will come back and contribute to the collective Knowledge Base....
  9. Airtime

    Airtime Monkey+++

    Lead acid battery life is driven in large measure by how deep the discharges. In short they do not like being discharged. I the battery is only discharged 10% of it's full capacity, they will typically handle 5000 cycles like that. A 50% discharge drops life to about 1000 discharge/charge cycles. And discharging one 80% of it's capacity cuts the life down to roughly 500 cycles. If you want this battery to last as long as you can, don't discharge it very much (ie keep doing what you're doing) and make sure the charger does not over charge it. The best chargers have a temperature sensor for the battery and compensate as appropriate for the temperature dependent battery chemistry.

  10. ghrit

    ghrit Bad company Administrator Founding Member

    As always, "it depends." Some batteries like to be fully cycled, like (for example) fork lift batteries. You need to know what type of cells the battery has. I'm no expert by any means, but there are differences.
    Cruisin Sloth likes this.
  11. melbo

    melbo Hunter Gatherer Administrator Founding Member

    I occasionally draw mine down to 50% and then let them come back up with the sun.
  12. Airtime

    Airtime Monkey+++

    There is not much difference in the chemistry of the various types of the lead acid batteries. The differences are structural and that shifts the discharge and life curves around but the fundamental shape of the life curves are very similar. So you may find one version of lead acid can handle a 50% discharge 1000 times and another might only tolerate that 400 times before significant compromise is noticeable. But none of them are going to have a longer life being repeatedly discharged 50% than repeatedly discharged just 10% of their full capacity. This is because the dimension that ultimately kills a leaf acid battery is chemical; the structure just changes how quickly that occurs as some can mitigate or slow the effect vs. others. Go looking and you'll find they all have a curve rather similar to the following. The difference will be the numbers across the x axis will be offset and/or scaled differently but the shape will be similar. An occasional discharge to 50% won't be very significant either way affecting positively or negatively the sulfating or uneven redeposition of lead.


    I don't consider myself a battery engineer or expert either by any remote stretch. Sadly, I am an EE (geek is spelled with two e's for a reason I've been told!) and some years ago was involved as the program manager for a product requiring extensive battery power and we went through all this very stuff. I've seen some of these very curves again in the last few months at work with some engine controls that stop an engine at a traffic light and then restarts it within 1/2 a second and less than 3/4 of a revolution from the moment the throttle pedal is depressed to go. They are using battery sensors that mount directly on the battery post that assess voltage, current, temperature and state of charge and then talk over a CAN datalink to the engine controller. The engineers assessed if there were specific battery recommendations to be made, hence their looking at battery data.

    Here's links for this info:
    Deep Cycle Battery FAQ Truth About Batteries - POWERTHRU White Paper.pdf - Batteries.pdf

    Have fun.
    Last edited: Mar 18, 2015
    ghrit and kellory like this.
  13. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Way under panelled for the size of that battery, and yes ,you will have .
    Battery Usage,

    Need more spec's info on Panels & PWM CC
  14. Maynard108

    Maynard108 Monkey

    It's actually 128 amp hours, I hit the wrong number. I really appreciate all the feedback and knowledge, the only people I have consulted for my questions have had everything professionally installed and grid tied.

    That's not to say I'm against that it just doesn't apply to my application.
    Last edited by a moderator: Mar 19, 2015
    melbo likes this.
  15. Cruisin Sloth

    Cruisin Sloth Special & Slow

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