cowcharge
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Post by cowcharge on May 20, 2016 5:06:34 GMT -8
Make sure you place at least the charger close to the batteries. Long wires lose a lot of the power meant for the batteries, unless they're big enough not to have a large voltage drop (I go for less than 1% voltage drop).
As for the inverter, if the batteries are in their own box there is no reason to artificially move the inverter away from them. In fact, having shorter wires is always better for efficiency (especially in solar charging). The reasons not to have your electronics in the same space as your batteries is because of corrosion from battery gases on your connections and electronics, and risk of sparks from the electronics igniting battery gases.
Smart converters are safe as chargers (I have a PD 45-amp myself, but it's not hooked up because I'm parked off-grid), because they charge at lower voltage than the battery mfgrs recommend. But that is the same reason they take forever to get you to full charge. They're really at their best for people who use hookups all the time (so their batteries never get discharged to begin with), and for when the camper is parked at home and plugged in for battery maintaining. Not good for boondockers except as a last resort to keep you above 50% discharge so you don't damage your batteries.
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sgaskill
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Post by sgaskill on May 22, 2016 18:06:40 GMT -8
If I build a box for the batteries how air tight does it need to be? Also, I'm a little confused about your last sentence. If I'm boondocking how would I even use the charger/converter to keep charge over 50% if I'm not hooked up to the grid?
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chametzoo
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Post by chametzoo on May 23, 2016 5:55:15 GMT -8
If I build a box for the batteries how air tight does it need to be? Also, I'm a little confused about your last sentence. If I'm boondocking how would I even use the charger/converter to keep charge over 50% if I'm not hooked up to the grid? A battery box shouldn't be "air tight". Hydrogen gas is lighter than air and will hover at the top of the enclosure, so duct out to fresh air at the top if possible and you will most likely be able to get rid of that gas passively but only if your vent through the trailer wall/roof is higher than the the opening in the box.. Air inlets near the bottom of the box enclosure wouldn't hurt either to encourage a good up draft too. If you can't duct the box high and vent to fresh air higher, you'll need a fan to actively pull the gasses out. A 12v electronics fan will do.
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cowcharge
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Post by cowcharge on May 26, 2016 11:26:40 GMT -8
While boondocking, you'd use a generator to power the converter. Which is horribly inefficient, which is why it should be a last resort. If you have to charge with a generator it's better to use the gen's 12v output right to the battery instead of 110v to the converter.
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sgaskill
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Post by sgaskill on May 26, 2016 15:54:58 GMT -8
I understand now. In a pinch have you ever had to run the parked vehicle to charge that way? I bet that higher outpt vehicle alternator comes in handy then.
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cowcharge
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Post by cowcharge on May 27, 2016 13:43:56 GMT -8
I haven't charged a camper that way, but I've had big batteries in a van being charged by the alternator, using a battery isolator switch that redirects the current from the car battery to the house battery after the car battery is charged. But like a generator, it's an expensive form of charging that I would only use when parked if there was no other way. A 200-300 horsepower battery charger is very wasteful.
I know you already have the battery, and I don't want to sound like a spoilsport, but for full disclosure (and for folks who haven't got a battery yet), I'm not fond of sealed batteries in campers (boats and planes with their unstable attitudes is another story). I think they're too expensive, they can't be charged as quickly as wet batteries (since I depend upon limited sunlight to do my charging, speed is of the essence), and they have less capacity per pound. And perhaps worst of all IMHO, being sealed, you can't get a true state of charge reading on them, or compare voltage between cells for maintenance purposes, because you can't test them with a hydrometer. The LEDs on your charger, and voltage readings, are inherently inaccurate ballpark figures that typically lead to perpetual undercharging. It seems to me that wet batteries, although they require checking the water periodically, are less worrisome because they are more robust.
I looked at Optima's specs on that battery (http://www.optimabatteries.com/en-us/shop/bluetop/optima-batteries-8016-103-d34m-bluetop-marine-boat-deep-cycle-starting/).
It's a marine engine-starting battery, which is designed to put out high amps for a very short time, like a car battery. That means it has lighter plates with more surface area to allow the majority of the battery's energy to be sent out all at once (870 cold cranking amps, in a 55 amp-hour battery, = .06 hours capacity at that rate, not that you're ever likely to draw that much). That also means that it's not intended to handle the deep, slow discharges that real deep-cycle batteries like the ones in golf carts and wheelchairs are subjected to. Repeatedly deep-discharging a starting battery wears down the plates, costing capacity and eventually shortening their lifespan. To make it last as long as possible, I'd recommend not discharging it deeply very often.
As for gassing and venting, I personally don't trust any battery to "never" gas to the point at which the case fails and they leak, so I would vent a sealed battery the same way I would wet batteries (not that I consider it a high risk, but unnecessary risk is unnecessary risk no matter how small).
Gassing (and heating) occurs when extra current beyond what the battery can absorb is applied. The chemistry doesn't change just because you seal the battery, ALL lead-acid batteries gas when extra current is applied to them, sealed or not. Sealed batteries are just built to hold a certain amount of gas pressure without leaking, but to keep the pressure low, they are typically charged at a lower voltage than wet batteries. Optima doesn't give a specific charging voltage in their specs, just various ranges depending on charging type, some of which go up to 15.6v, which sounds really high to me (wet battery mfgrs like Deka and Trojan recommend they be charged at 14.8v). Optima basically says you can charge them with anything as long as you keep the temperature below 125 F. Now if you're parked in the sun, with a battery on the tongue in a standard black battery box, it wouldn't take being in a desert to approach or exceed 125 degrees. That wouldn't give you much room for error in your charging scheme on hot days. And if you ARE in the desert with the battery under the dinette where the A/C doesn't reach, I wouldn't think it would take much to get to 125 either. Either way, it seems that temperature monitoring would be required during charging. I'd be sure to compare whatever you get for a charger with Optima's specs (not the charger mfgr's specs) to be safe.
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chametzoo
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Post by chametzoo on May 27, 2016 21:30:28 GMT -8
I know you already have the battery, and I don't want to sound like a spoilsport, but for full disclosure (and for folks who haven't got a battery yet), I'm not fond of sealed batteries in campers (boats and planes with their unstable attitudes is another story). I think they're too expensive, they can't be charged as quickly as wet batteries (since I depend upon limited sunlight to do my charging, speed is of the essence), and they have less capacity per pound. And perhaps worst of all IMHO, being sealed, you can't get a true state of charge reading on them, or compare voltage between cells for maintenance purposes, because you can't test them with a hydrometer. Cowcharge busts yet another electrical myth. He lives off grid… he knows what he's talking about
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cowcharge
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Post by cowcharge on Jun 3, 2016 11:44:46 GMT -8
I don't live off-grid yet. Eventually, yes. But my camper isn't done yet, and right now I'm living in my dad's house helping to take care of him.
I don't claim to know everything, or to be an "expert". I did however spend a couple of years helping to install residential and commercial solar systems for hot water and air heat as well as electrical, and have done a ton of research to build my own system. I speak up about batteries and solar charging in the hope that it helps people to build systems that actually work (as opposed to the systems the "pros" install that have a roof full of panels yet still require generators), and maybe save them some money in the process. I don't sell anything, or make any money from anyone involved in campers.
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