Battery and Inverter Question

[Cotie]

I can't go all the way and get the solar thing done until I sell my house and can buy a bigger van.

I'm going to take off for the winter in a Honda Odyssey mini-van and after reading Bob's article :
Baby Steps: How to Have Electricity in Your Car or Van For Very Little Money

I've decided to get a a AGM battery and an inverter.  Looking on Amazon.com has lead to some confusion and questions.

My handy man mechanical aptitude is zilch.

So, on the inverter page I was looking at the recommended Cobra 400 Watt converter.

I see that the same brand 800 Watt converter is just a little more cost. Is there any reason not to get the
800 watt?  Would I  need more that one battery? or a battery of a certain power?

On the batteries I did a search for AGM Battery on Amazon and got this page
http://amzn.to/1OH27Tf

I see one battery selling for $63. It says it is a 35AH. The more expensive battery next to it
is 125AH. Does the AH make a difference.

I there any of the less than $200 batteries on this page that anyone could recommend ? Would the $63 dollar battery be okay?

Also, as I understand, with the AGM type battery, no holes have to be drilled for ventilation, because it doesn't leak hydrogen. Is that correct? 

I've read that the AGM needs a smart charger. This is the charger I plan to get.

http://amzn.to/1QPyDC1

Any reason not to?

 

[Optimistic Paranoid]

On the question of 400 vs 800 watts, it depends entirely on what loads you are planning to power from it.

If you buy the 800 watt, and only hook 400 watts of devices up to it, it won't draw any more battery power than the 400 watt would.

800 watts divided by 12 volts equals 66 amps.

400 watts divided by 12 volts equals 33 amps.

So if you run a 400 watt load for 1 hour, it will draw 33 amp hours out of the battery.  An 800 watt load run for 1 hour would draw 66 amp hours out of the battery.

Remember that you can only draw 50% of a battery's capacity safely, so a 35ah battery can only supply 18 amp hours.  A 125ah battery can only provide 63 amp hours.

Of course, if you have your ride rigged so the alternator will charge the house battery, running the engine while using the inverter changes the math quite a bit.

Regards
John

 

[SternWake]

Good questions that raise a few of my own.

First, how and what and how often are you going to require battery power. List your devices and how often you expect to need to run them.

Will you be hoping to recharge while driving?

Here are a few things to consider, In most cases a 400 watt inverter powering a 65 watt load is going to be much more efficient than an 800 watt inverter powering the same load.

Also consider that 400 watts at 12vDC is about 38 amps. This is a huge load and a small battery cannot power it for very long before the voltage will be dragged doen the the 10 or 11 range where the low voltage alarm will sound and perhaps the unit will even shut off.

So upgrading to an 800 watt inverter, with only a small battery, could be a detraction, over a smaller inverter. if you were later to increase the battery size then you could perhaps utilize the extra 400 watts, but with only a 35AH battery, do not bother.

I happen to have both a 400 and an 800 watt inverter. I almost never use the 800 watt one, but then again I rarely use either.

if your desire for an inverter is to charge devices that are charged by USB, then an inverter, just for this purpose alone, is inefficent. A simple 12v to 5vUSB converter is much more efficient. Consider these products:

http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=mobile&field-keywords=USB+Car+Charger

If your laptop is a PC, then a car adapter is also available for this which will be at least 155 more efficient than an inverter powering the laptop provided power brick. Plug your laptop make and model into amazon electronics and add 'car adapter'.

if you have a Mac, you might require a P$W inverter over a MSW inverter, I am not sure of the offerings for macs and if car adapters are available or reliable.

As long as the AGM battery is not overcharged it will not vent. Usually the issue is chronic undercharging, not overcharging.

For those with minimal electrical loads, it is possible to forgo the house/Aux battery entirely. If so then one should carry a jumper pack, and always keep it fully charged. Some people like to use the powerpack itself for house loads, but in my opinion this is unwise, as their batteries are low capacity, and the jumpstarting ability is quickly degraded when these batteries are cycled.

The charger you get for the AGM battery is really dependent on the AGM battery you get. if you only have a short amount of time to plug into the grid to recharge then a higher amp charger is mandatory, but it still must not exceed the battery manufacturer recommendations, and most of these lesser AGMS are limited to 30%, which is 30 amps on a 100AH capacity battery.

If one wants to get good lifespan from an AGM, they must be able to return it to 100% full charge every 5 to 7 cycles. Gettin it to only 90% will have the battery walk down in capacity much faster. Charging a battery fully takes time. that last 20% generally takes 4 hours no matter how powerful the charging source might be, as the battery itself limits how much it can accept in the 80%+ charged range, and the higher the state of charge the more it limits it.

There are hundreds of ways to solve your power needs, and much depends on your power usage and how much battery longevity you expect. Seeking Ideal battery life is often a waste of effort, as it is just easier to replace the battery sooner, but one should also know how to get a reasonable life from the battery and this is all about recharging it as close to full, as often as possible, and not letting it sit in a discharged state.

Those that cant regularly get their battery up above 80% will have very short battery life indeed. Those that can can achieve acceptable battery life. those that take every step possible for maximum battery life, well it might not make financial sense to do so, or be worth the effort, since one can just buy a new battery and start the battery degradation cycle over.

So list your intended battery loads, and how long you expect to use them, and we can narrow down the battery capacity you can get by with, and the proper charger for the battery, and perhaps we can also help you to use less electricity, which is easier than creating more of it.

 

[Cotie]

Thank you very much for the replies.

My main usage will be a laptop, a larger monitor attached to the laptop, a dymo label printer and either a laser or ink-jet printer. Also, probably a light with a LED light bulb.

Research on the google I get the following watts.

ink jet = 20 watts ( I currently use a laser, but will probably buy a cheap ink-jet for the trip)
dymo = 40 watts
monitor = 30 watts
Laptop = 60
led light = 18?

I also want to use a ninja blender for smoothies, but intend to use the generator for that.

I supplement my social security retirement by selling books on the Amazon FBA program where I ship my books to amazon and they store the books,
then ship a book out when it sells.

That's why I need the the dymo printer to put labels on books and an ink jet to label the boxes going to amazon.

If I can do good enough finding books as I travel, then I can pay for the whole trip that way.

I intend to charge the battery with the generator and not with the car while it is running.

 

[SternWake]

Well, how often/long you plan on running the laptop and monitor is a huge variable so far left unaddressed.

I think you will be requiring significantly more battery power than 35AH. I think you would be better off with a 125Ah battery, and a 30 amp charger, at the minimum.

I've no personal experience with the Vmax tanks batteries:
http://www.amazon.com/Vmaxtanks-Vmaxslr125-rechargeable-Solar-Inverters/dp/B00ACNO2AO

This is another lower end Asian AGM, but only 100AH. Consider 2:

http://www.amazon.com/Universal-Pow...05240&sr=1-1&keywords=universal+battery+100AH

Top Quality AGM like Lifeline are much pricier, but can handle huge charging sources, whereas the above batteries cannot.
http://sepbatteries.com/lifeline-gpl-31xt-agm-battery?gclid=CP71yJyghMgCFZKBfgodF7kMUQ

For the lesser AGMS, I'd recommend this as a charger:
http://www.amazon.com/IOTA-Engineering-DLS30-Converter-Battery/dp/B00A0V5HPC

For the Lifeline gpl-31xt AGM I would recommend this:
http://www.amazon.com/Progressive-D...ie=UTF8&qid=1442705442&sr=1-1&keywords=PD9245

This is assuming you will be using the laptop and monitor for at least 4 hours a day. Your power needs are bigger than you suspected. I know the prices of these items is way outside your expectations, but a 35AH battery is never going to be able to meet your needs unless you only run these items for 15 minutes a day.

These converter chargers I linked to, on much provide their own cables to the battery. They can recharge and power all12vdc loads at the same time. Regular battery chargers will get confused when charging while there are still loads on the batteries.

Please beware of automatic charging sources with alligator clips attached and their accompanying marketing. They are no where near as good or effective, as they, and their owners, would like you to believe.

No charging source is perfect, but the commonly available automatic chargers today piss on you and tell you its raining. These converters might not have a pleasing exterior appearance, their ability to recharge the batteries is superior.

Sorry to be the bearer of unpleasant expensive news.

You might also require a PSW inverter for the printer, which is also more expensive than MSW. There is no way to know for sure, unless it fails, or does not. You should however be able to get away with a 200 watt PSW inverter.

All the items you list will have their power consumption listed on their backsides. Multiply volts x amps to get watts. this is the most that the device can pull, not necessarily the amount it will always pull.