Posted: 11/23/2013 8:05:20 AM EDT
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The place I work is getting read of some batteries I am wondering if they would be ok for solar / backup power applications current plan is I would keep them on a 110v maintainer and then when the power goes out use them to run my pellet stove and fridge until I can get a generator setup. Battery Specs are below.
MCG-120 110 Ah @ 20 Hr Rate to 1.75 Vpc @ 77 degrees F 12V VRLA Non-Spillable Battery Float Volts 13.62 - 13.80V @ 77 degrees F Also I do not know if all of these batteries are good or bad how would be best to charge and load test these batteries? |
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The place I work is getting read of some batteries I am wondering if they would be ok for solar / backup power applications current plan is I would keep them on a 110v maintainer and then when the power goes out use them to run my pellet stove and fridge until I can get a generator setup. Battery Specs are below. MCG-120 110 Ah @ 20 Hr Rate to 1.75 Vpc @ 77 degrees F 12V VRLA Non-Spillable Battery Float Volts 13.62 - 13.80V @ 77 degrees F Also I do not know if all of these batteries are good or bad how would be best to charge and load test these batteries? I'm not that battery savvy, but it sounds like a reasonable idea to me. Hopefully Gamma, Expy, Ski, etc. can help you out. |
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If they're free, I'd git as many of 'em as I could!
Even if they're toast, there's enough lead in 'em to make hauling them to the scrapyard worthwhile. In order to test them, you'll need some sort of charger to recharge them first. Then, after they've been fully recharged, you connect a constant DC load to them - a few light bulbs, for example, measuring the amount of current the bulbs draw. Leave the DC load connected until the battery voltage drops below approx. 11.5 volts. Multiply the hours the DC load is connected by the amount of current your load draws, and that'll be roughly how many amp-hours the battery has provided. For example: Let's say your DC load draws 6 amps. If your battery provided 6 amps for 15 hours before dropping below 11.5 volts, that's 6 amps x 15 hours = 90 amp-hours. For a battery rated at 110 amp-hours, 90 amp-hours would be pretty decent, especially since you didn't completely discharge it. OTOH, if your 110 amp-hour battery only provided 6 amps for 2 hours (i.e., 12 amp-hours), it would mean that either (1.) your battery was toast, or (2.) it wasn't fully recharged before you started the test. |
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You can draw down deep cycle batteries up to 50% but more than that shortens the life span. Standard car batteries arnt good for deep cycling but if you dont draw them down more that 20 % each time, they will be ok for a long time if they are kept charged. I have just one Trojan that is sulfated but it still will put out 80 amps at 12 volts. So yes old batteries can be very useful. I also have 2 car batteries I can draw 20 amps each from. As far as gel or VRLA goes, other guys on the board will know more than I do. |
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Wvjeeper, I agree with Skibane that grabbing as many of those batteries as possible would be a good idea. Charge them using a good multi-stage battery charger (I use an Iota), a battery tender is a good idea, but I wouldn't do the main charging with a cheap little charger.
Re. load testing, I'd draw 50% of their capacity (55 ah in your case)---you can measure this if you have a meter, I use a Watts-Up and a Kill-A-Watt for my little system. You can also estimate based on the specs of the appliance (don't forget to include the inverter draw). After you've drawn ~55 amp-hours, disconnect the inverter and let the battery rest for a few hours, then measure voltage with a multimeter to determine state of charge (I use this chart [XLS]. If it's well under 50%, they're probably a bit spent, but they might still be useful. I tested an old 150 ah AGM this way not too long ago and found that its useful capacity was a fair bit less than it should have been. Still runs the lights just fine, just not for as long. I treat it like a 100 ah battery now. |
| I have a kill a watt and a good multi meter to use another question is if I wire these batteries in series will they charge or discharge incompletely if a weaker battery ends up in the middle of the series somewhere? Also what limits me to how many batteries I can have in a series? I have not purchased a inverter yet my main goal is to be able to power my fridge, pellet stove, TV, DVR, Modem, wireless Router for 12-24 hours I will start tonight and run the kill a watt and see what my total draw for the devices would be over a 24hr period and I guess go from there.At this point I will be looking at a good charger/ tender that is 110V to keep the batteries up when not in use would like on that will tell me possibly the state of discharge of the bank so I know how much is left and when I run the generator when the batteries are fully charged. |
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if I wire these batteries in series will they charge or discharge incompletely if a weaker battery ends up in the middle of the series somewhere? Quoted:
if I wire these batteries in series will they charge or discharge incompletely if a weaker battery ends up in the middle of the series somewhere? Yep. Connecting them in series helps, but they'll still only be capable of supplying as many amp-hours as the weakest battery in the string - and will also recharge unequally. Ideally, you want all batteries to be the same brand, chemistry, AH rating, and age. For used batteries, you also want them to have shared the same work history. what limits me to how many batteries I can have in a series? From a practical standpoint, you'll probably be limited by the availability of inverters and battery chargers in your chosen DC voltage. Once you get above 48 volts, there's not a whole lot available - particularly in small-to-mid-sized models. At this point I will be looking at a good charger/ tender that is 110V to keep the batteries up when not in use would like on that will tell me possibly the state of discharge of the bank so I know how much is left and when I run the generator when the batteries are fully charged. Although it's not a battery charger, Bogart Engineering's TriMetric meter does an excellent job of keeping track of battery discharge/recharge. |
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will the charge completely and discharge completely in parallel? The problem with mis-matched batteries becomes even more severe when they're connected in parallel. At least in series, all batteries have the same charge or discharge current flowing through them, which helps to minimize any differences between them. In parallel, each battery can supply or consume a different amount of current than the others. Typically, sick batteries contribute less than their fair share of current to the load, and take more than their fair share of recharge current. This forces the other, healthier batteries to work harder, shortening their lifespan. This imbalance problem becomes worse as more batteries are connected in parallel - Generally, connecting two batteries (or battery banks) in parallel is acceptable; connecting three in parallel is marginal, and four or more in parallel is a no-no. |
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on my Kill A Watt what should I be tracking KWA per given period, peak wattage I see when something kicks on, anything else I need to llok at to accuratley size my system? With just a Kill-A-Watt I'd keep track of kWh primarily, plus keep an eye on peak amps. Run your loads for 24+ hours and determine total kWh per day. With a 110 ah battery drawn down to 50% you have 55 amp-hours. So let's say your Kill-A-Watt says you used 0.6 kWh/day. 0.6kWh = 50 amp-hours per day. This gives you 1 day autonomy with a 110 ah battery. This does not include inverter draw---the Kill-A-Watt does not measure this. My little 400W Cobra inverter draws 0.5 amps with no load (measured with a Watts Up meter). If I left it on 24/7 the inverter alone would draw 12 amp-hours per day. Generally speaking, the bigger the inverter, the bigger the no-load draw. |