Help determining our "shopping list"

nickd · Mar 23, 2013

Hey guys!My wife and I are starting our first van conversion and would really appreciate some input and help figuring out how to best set up our electrical system.We don't have extreme power needs. Here's everything that I could see us potentially using:- 2x MacBook Air laptops for 2-3 hours daily (45W chargers) - 2x iPhones (will mostly charge while driving, occasionally using 12V USB) - Fan-tastic Vent for several hours daily/nightly (we will be in a hot climate, so this will be crucial) - Some small LED lighting for a few hours nightly (mostly will use battery powered or solar lanterns, but may have 12V rope light or one other 12V light) We will occasionally charge USB devices like our phones, wifi hotspot, small speaker while our computers are plugged in, but I assume this will only increase power consumption by a minimal amount.I'm not sure if we want to spring for solar right now, since our power needs are minimal. We'd like to charge off the alternator with a continuous duty solenoid, and then have a smart charger wired up so we can charge off an extension cord when possible.We probably won't be doing much boondocking, and when we do, it won't be longer than a week at a time. If we start to boondock more (or for longer periods of time), we will add solar.I need help choosing a battery and smart charger, and making sure I understand how to wire it all together. Since we probably won't need a large battery bank, I'm guessing it's worth it to spring for a single AGM, correct?Does this sound like a good starting plan? Are there other options that you guys would recommend? Would you recommend adding some solar from the beginning?Looking forward to discussing!Thanks!

Coffee Tim · Mar 23, 2013

Hi guys.  I would suggest a couple of 12 volt Trojan deep cycle batteries.  These can be purchased one at a time, if needed, and should give you the power ypu need.  A good 400 watt inverter should also meet your needs for the items you mentioned.  A smaller 150 watt plug in inverter will also work if you arent charging everything at one time. Your alternator can charge your batteries while you drive and the smart charger when you are plugged in.  I realize that two 6 volt batteries wired for 12 volts is better but they need to be bought in pairs and they are expensive. The 12 volt batteries can be added one at a time as funds permit. Just don't skimp on the solidoid as I have found that the cheap ones burn out pretty quick. Hope this helps.

peacetara · Mar 23, 2013

That's not necessarily a 'small' amount.  depending on how you size things (my math could be a little off, I tend to round up): Laptop: 45 watts at 12V: 4amps/hour    x 3 (hours) x 2 (laptops): 24ah iPhones can take up to an amp each: so that's 1ah*2: 3ah (about 1.5hrs per day to keep it happy, depending on usage.. this is a guess) Misc stuff: 1ah x 3 hrs = 3ah Fan (Not a clue what it takes): 1ah x 4 hours = 4ah Suddenly you are 34 amp hours per day.  That's not huge, but it's not exactly small, a 100ah battery (the common Trojans usually run around that).  So that means you get 50ah per battery of use (because you don't want to use more than 50% of your battery) and suddenly every single day you are almost using your entire battery. Granted, I rounded up in pretty much every case, because 1) 12V to 110V inverters will take about 30% extra electricity to convert into 110, and because everyone always uses more electricity than they say they will <img rel="lightbox" src="/images/boards/smilies/smile.gif" class="bbc_img"> So a single T105 Trojan (100ah) will last you 1 day from fully charged before it's dead (50%). To charge your battery from your car you'd have to drive many hours every day to get your battery back up to charged. I'm not trying to discourage you from doing a house battery, I'm just trying to show a possible outcome, where you have to drive 4-6+hrs every day to charge the battery (depends a lot on the cabling and type of alternator), which to me is gross-tastic.  But if it works for you, awesome!

wrcsixeight · Mar 24, 2013

It all depends on how much driving you are going to do each day, and how much you are going to use those macbook airs. You can get away with one battery, but you will be draining it below the 50% number, and these deeper discharges age a battery faster.  Especially without a weekly 100% recharge, and you cannot rely on the alternator to do this.  It takes many many hours to achieve a true 100% whatever the charging source, though if 4awg or thicker wire is used from alternator to solenoid, getting from ~20% to ~80% can be done in under 2 hours, if the alternator is capable, and if the vehicle's voltage regulator allows mid 14's for those 2 hours. Most vehicles will not allow the ~14.5 volts required for faster charges to occur for very long for fear of overcharging the original single engine starting battery which was never designed to be deeply discharged in the first place. Once the voltage is prematurely reduced to a safe battery undercharging ~13.6 volts, very few alternator amps are required to hold 13.6 volts, so getting back upto 80% can take much longer, and that last 20%, twice/thrice as long. Thicker cabling allows the voltage regulator to 'see' the depleted house batteries better, and the chances it will stay in the mid 14's is greater. Every vehicle is different, but the constants are, everybody vastly overestimates the alternator's contribution as well as how much energy is stored within a battery, and underestimates how much battery power they are using.  Most also think they are starting a discharge cycle from a fully charged battery when this is Highly unlikely in most scenarios, especially without solar. AGMs are safer unvented in the Van than other batteries, but technically should still be vented to the exterior.  Be sure to mechanically secure it.  Think worst case scenario....  a rollover.  Don't add more shrapnel to the grenade. Trojans t 105's are good batteries, but are flooded, and you cannot just use one as they are 6 volts each. 2 of them give you about 220 amp hours. Get a quality continuous duty solenoid rated for 100+ amps and much higher surge amps.  The higher the rating, the less likely the contacts are going to weld themselves together when passing high currents. I just helped someone install an older solenoid of unknown rating they had laying around, and it heated up fast passing just 20 amps, and in 5 minutes the contacts had fused and no more isolation was occurring when the engine was shut down.  This type of solenoid failure can be bad not only for the engine battery, but also if out in the boonies, you can drain the engine battery dead and be up poo creek in a barb wire canoe.  Paddle or not, no good. When you have grid power available, you should have a product like a Converter to automatically recharge the battery.  A converter can power all 12 volt devices while recharging the batteries safely.   It is hardwired to the battery.  The main difference between a converter and a battery charger is that a battery charger is designed to be portable.  A BC can also easily get confused trying to charge a battery that is powering lights or a laptop or a fridge while a converter is designed to handle loads running while charging the battery. Iota and Progressive Dynamics make good converters. They are available from 15 amps, to 100 amps.  While you may say you will never need 40 amps, a depleted AGM battery would argue with you.  The battery will only take what it needs, and voltage regulation of the converter will keep it from overcharging. I will be getting a 55 or 60 amp converter for two group 27 batteries.  These batteries can initially ask for 90+ amps from my alternator over my upgraded charging circuit, when depleted.  To bad the alternator protests such demands,  but the batteries really seem to like this short lived quenching of their thirst.  Don't fear a powerful charging source, unless it is an old style manual battery charger with wheels and the size of a large suitcase. http://www.bestconverter.com/ For your macbook airs, look into getting a car charger with a ciggy plug  vs using an inverter to power the original power brick.  Significantly less battery consumption can be realized with a dc to dc converter rather than  an inverter taking 12vDC converting it to 115vAC, then the power brick converting it back to DC. You can get away with one large AGM battery, group 27 or group 31, but you will be cycling it deeply and shortening its life, and if you do not make sure to get it back upto 100% weekly then the life is shortened further. You should get yourself a digital multimeter and learn how to take voltage readings at a minimum.  Voltage is only accurate as to battery state of charge with a battery that has not been charged or discharged for several hours, but once you do it enough, you can get an  general understanding of the trends and tendencies of how much battery power you are using, and how much is being returned when driving. While you can later add another 12 volt battery to the first 12 volt battery, this is not ideal, and the newer battery will quickly degrade in health to the same level as the first battery.  Better to buy identical age and brand batteries at the same time.  But if you do find one battery is inadequate the sooner you add the second, the better. Do not discharge an AGM and a flooded battery hooked in parallel, though they can be charged together in parallel.  But always search out the  manufacturer recommended bulk/acceptance and float voltages as see if the two batteries are similar beforehand.

nickd · Mar 24, 2013

Thanks for the help so far, everyone! Learning a lot here. I would love to get dual AGMs right from the start, but we may have to go with T105s at the beginning until we have the funds for dual AGMs. However, in case we end up being able to get AGMs right away, what are your favorites? Everything we run in the van will be 12VDC, so we won't have to worry about an inverter and its incurred power suck. I'll plan on getting a 55 amp IOTA converter for shore power. A Cole Hersee CD solenoid rated for 85 amps should be good, I assume (http://www.amazon.com/Cole-Hersee-24106-Continuous-Solenoid/dp/B001FQL43U). Once again, I appreciate the help. I'm continuing to learn, and this is very valuable to me.

wrcsixeight · Mar 24, 2013

Since I am spending your money, Odyssey and Lifeline are my AGM dream batteries. It will be possible to max out that Cole hearse CDS with adequate cabling and engine rpm.   Go for a higher rating to avoid possible issues. http://www.amazon.com/gp/product/B000CEBXRS/ref=pe_163380_28768990_email_1p_0_ti. Trojan t 105s are good, but all golf cart batteries are deep cycle batteries and the sam's and costco GC batteries are reported to give great service for a good price. Beware of 12 volt flooded batteries which say deep cycle on them.  Usually RV and Marine are included on the label.  These are dualpurpose batteries, closer to a starting battery than a deep cycle and will protest regular cycling. True 12 volt deep cycle batteries exist, but they are generally 30% more expensive than marine batteries.  Flooded batteries in the passenger compartment should be in a sealed box which is vented to the exterior of the vehicle. The first set of batteries are learner batteries.  Most learner batteries are abused into a premature death and perhaps cheaper marine batteries might be more cost efficient in the long run while you learn how much you can ask from them, and how much your vehicle is returning to them.

Zil · Mar 24, 2013

If initial battery costs are the factor, then most users recommend 6 volt golf cart batteries. Hook in series for 12 volts. As house batteries they report many years of service, if maintained. Cosco or Wally World. They are true deep cycle batteries.

nickd · Mar 25, 2013

Alright, I'll probably just head to Walmart soon and grab a couple golf cart batteries. It'll be good to keep the cost down for our first conversion, and we can always upgrade down the road.