How long will batterys last?

[demodriver]

Im looking at buying a inverter and 3 or 4 batterys to run household style stuff. I have no experience with these so I dont know what to expect out of them.

I am looking at a 5000 watt inverter at harbor frieght and am thinking of hooking it to three decent size deep cycle batterys.  How long would this last running stuff for three people in the evenings?  Would I have to charge it after in a few hours or would it last a few days?

I knows that it depends on what we are doing electrical wise but a rough idea would be nice.

[John316]

Eric,

Most of our bus is electric. We have to 4K watt Trace inverters. We also have six deep cycle Trojan batteries.

We can run for about 36 hours, without charging. However, that is without AC's.

FWIW

John

[technomadia]

It's very difficult to give a rough idea on how long your batteries could last.  It is very much tied to the size of your batteries, the ambient temperature (lead acid don't provide as much power at lower temperatures), how much of a draw you're pulling from your batteries and the rate of draw (higher rate of withdraw = less amperage).

We just put in a 500 aH bank of Lithium Ion batteries (which gives us ~400 aH of actual usable juice, as opposed to lead acid where you may only get 30% of the amperage of out them in real time circumstances) and a 3k smart inverter. We can go a couple days without recharging if we're being conservative with our power usage. But it will only last us 2-3 hours if running things like our microwave, our big computer monitors, air conditioning, etc.


We have a series on our blog about our experiments with LiFePO4 battery chemistry, including on going over lead acid batteries that you may (or may not) find useful:

http://www.technomadia.com/category/life-on-the-road/technology/lithium-ion/

Enjoy,
- Cherie

[bevans6]

It's all about the amp hours.  I have 235 AH at 24 volts nominal, I can run typical night time usage for us for about a week or more, but to be honest I've never tried to run more than a day or so without some opportunity to charge things up.  A TV, a couple of computers only use a few AH.  I figure it's less draw than my 12v lights, the fridge computer, etc.

Like always, recommend you look at a true sine wave unit, and a 24 volt unit.  5000 watts at 12 volts is around a million amps, or so it will seem when you try to buy cable to hook that up.  If you don't plan to run your air conditioner from the inverter (which is my killer application, I run the AC from it, via the bus alternator, while driving) then you can look for a nice little 1500  - 2000 watt PSW unit that won't cost a bomb and will run your microwave, coffee maker and the small stuff no problem.   Also highly recommend you look for one that can be properly and permanently wired into your AC house distribution panel rather than some plugs on it's front panel and extension cords.  

Brian

[demodriver]

Thanks for all of the advice. I should of been more clear with what I am doing with this set up.

I will be boon docking in a camper with two employees for several months on a job that I am getting ready to start.   This set up will be temporary but may end up in a bus when I buy another one. There will be no ac, computers, or microwaves. Just lights for the most part and maybe a tv with a game system of some sort.

Has anyone heard of anyone using the cheap inverters from harbor frieght?

[bevans6]

I use a 750 watt black and decker that costs about $50 for what you are looking at.  Recommend using 12v lighting rather than converting to 120 vac, since you lose maybe 10% inside the inverter.  But running a tv, a DVD, like that, is simple stuff.

Brian

[robertglines1]

Eric can you rig to run on you truck /equipment during working hrs to recharge. seperate carry case strapped down with a couple charge wires- 12 volt system.   Might look at cheap gen set to run for peak load and run charger couple hrs a day.   Bob

[demodriver]

Bob my excavator is set up for two battery's and I only run it on one. I could possibly rotate the battery's everyday to charge them.

I went ahead and bought the 5000 watt one from hb for $500.

What do I need to look for on the battery labels when shopping for them? I was thinking three or four battery's. Do I need that many?

I found some marine battery's that are group size 31 and are 750 cca. Would a couple of these be ok?

Thanks again.

[TomC]

The big and tall 6v batteries like the T105 are better since they are rated for deep cycle.  Personally-I like the L16's-big and lots of amps (around 400amp/hours).  What are you going to charge the batteries with?  Having an Inverter/charger is really too convenient-although they are expensive.  When you have current, they are an automatic three stage battery charger, and when the electricity leaves automatically switches to inverter power without interruption. I like the Magnum 2800 watt with 130 amp built in charger.  It is a pure sine wave inverter, but as said, are expensive-around $1,800.00.  Good Luck, TomC

[robertglines1]

need to run blower on furnace? would have 2 hooked and two charging.  What about weekends? cold weather comming.  Can't find local farmer with elect for $100 a month?  Have done that. just suggestions. bus nut in area?

[demodriver]

I have a job sight style generator (very loud, I dont want to listen to it much) that I can use with a battery charger to charge the batterys back up. I thought about doing something like Bob mentioned and rotating the batterys thru my excavator to charge them.  I would probably be running the excavator for 10 hours a day (or from daylight to dusk).  Our truck also has a forklift battery style plug in on it for the winch that I could rig up to plug into the batterys and let it charge for awhile.

[buswarrior]

Your biggest challenge appears to be re-charging.

A simple lawn mower engine with a belt driven, small amperage auto alternator might be better than a loud generator and a battery charger with how few charging amps?

You need some good amperage to get the batts recharged, or you get to charge for hours, and hours, and hours...

The surest way of killing batteries in a matter of DAYS or a FEW WEEKS, is not getting them properly charged back up between discharges.

Also, you do not want to use more than half of their rated capacity, or you'll kill them early.

You need to do some serious reading in order to not waste your money and piss off your employees when it goes wrong.

try some sites like homepower magazine:   http://homepower.com/home/

and my favorite, under the learn tab,

alternative energy store:   http://www.altestore.com/store/

It has been suggested, that batteries do not die, they are MURDERED.

You are on the path to murder.

happy coaching!
buswarrior

[demodriver]

My charger has a 50 amp charge setting. How would a low amperage alternator on a gas engine be better?  Are you meaning to let the small engine run non stop or nearly non stop?

thanks Eric

[buswarrior]

You want a smart charger with 3 or 4 stage charging that can intelligently pound high amps into the batteries in as short a time period as possible. The shorter run time to reach full charge the better.

A small automotive alternator means something in the 60 to 100amp rating, any higher might stall a smaller HP engine. It would put good amps/high amps into the batteries versus a typical plug-in battery charger, using lots less fuel than the losses with a generator to a battery charger to the batteries.

What kind of battery charger is it that you have with a 50 amp setting? Not one of those "start-boost" type things with a lower 12 and 2 amp setting as well? The boost won't charge.

A little solar to help top off the batteries is also an option.

Getting the last few amps into the batteries takes the longest time, and are most critical for good battery health.

No kidding, keeping some deep cycle batteries alive, and you need real deep cycle batteries, not marine or other tricky marketing foolishness, is a whole new world and you will spend, and then waste, a lot of money needlessly, unless you get the knowledge of how to take care of them.

I'd recommend the T-105 kind of batteries as mentioned earlier, typical golf cart batteries, 6 volt, wired properly in series/parallel strings to make the 12 or 24 volts needed, and available as good used take outs, or new, from the golf cart company or their suppliers, almost anywhere that golf is played.

happy coaching!
buswarrior