My new battery bank is not working?!

Started by MNJon, July 20, 2012, 09:23:26 AM

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MNJon

OK, I have my new system set up but something is not working correctly. I am assuming I wired something incorrectly or I have a short.

I installed the following components:

4-6V Costco (Interstate) GC-2 batteries-wired in 2 groups. (Pos-Neg/Pos-Neg then Pos-Pos and Neg-Neg with the charger leads and the inverter leads sharing the Pos-Pos and Neg-Neg terminals. I also wired a 12V water pump directly off these terminals.

2,300W Powerbright Inverter

Powermax Boondocker 75 AMP charger.

OK, all of these components are brand new. I have them charging off a Champion 2,000 Watt generator. I purchased the charger from bestconverter.com and spoke with the owner/tech who stated this charger would be more than sufficient for my application.

Now, I fully charged the batteries to 12.9 volts on day 1. We went to bed around midnight and around 7AM the inverter shut down. I went and checked and my voltage reading was 10.5. I recharged to full capacity the next day (12 hrs basically) and the same thing the next night.

Last night I disconnected everything but a small 12V fan. at around 1AM the voltage reading was 11.3 and this morning at 8AM the batteries were completely dead again at 10.5. The first two nights we had a small ref running on the system as well.

The system feeds an old camper which I have added a 16x20 addition. The entire load consists of the camper which houses the refrigerator, a few 12V lights , a 12V portable fan and a few outlets that only charge cell phones. The coffee pot and microwave only run when the generator is on. In the addition we have 1 tv,one dvd player, two AC fans and a couple battery chargers for the power tools.

Even if I had multiple items running at once this system should last longer than this, or am I way off in my calculations? The readout on the inverter reads 45 watts when hooked up with very little load.

So could a short be causing excess drain?
What about a faulty ground?
I thought maybe the old distribution panel could be draining it off. Possible?


I am going to buy a Kill-a-watt meter to help troubleshoot but it wont be here for at least a week.

When I complete the house there will be new service panel feeding the house and the system in the camper will be abandoned and use for storage, but until then I have to use it.

CjAl

you should check each cell of the batteries. when yoi have batteries hooked in.parrellel if one cell is bad the two banks will constantly fight each other to ballance the load which cases them to discharge.this is why in our big trucls we replace all four batteries at the same time. short of getting into the.amp hours used and available it sound like you have a bad battery


MNJon

That was one of my initial thoughts. I checked each cell and the read the correct voltage. Basically each cell at 6.15 volts then together at 12.3 volts. Then when the tow cells are connected I got 12.3. I will check them again when the inverter indicates a full charge.

CjAl

sounds like you are testing each battery.

each of your 6v batts has three cells. 2.4 volts per cell. you cant just test voltage as you are just testing a surface charge, it doesnt matter untill you load it. you need to pull the caps and test the specific gravity of each cell with a hydrometer.


i am not the.most well versed person around here on batteries i am just the person with the most time on my hands

alex trent

I am eagerly awaiting your solution.

I have two Trojan 12v AGM 31s...200 AH total.

I start at 95%..after waiting 20 or so hours from the last charge and i get down to 50% real quick. Only running a computer 4 hours  and charging a LED spotlight 1 hour a day, pus not more than 3 hours of 120v 60 watts of lights.

In 15 hours on the inverter I am 50%. I realize the batteries will not fully charge for 10 or so cycles..I am on 7 now, so hope that helps.  My AH calculations vs what i am getting are off by a factor of 3.  Can it be my house box and wiring suck that much?


rsbhunter

The best advice is to go to either Survival monkey.com, or backwoods home .com and ask there.(in the off grid, solar sections)..i am on both forums, and some of those guys have forgotten more than most can learn...That being said, i am setting up a larger system....10 235 watt canadian solar panels, an Outback VFX 2436 power center, and am considering iron-nickle battery bank..This is for a 20x30 cabin!!! .....What my first take is , that the power going out is more than the system can handle.....The inverter itself is a constant draw,,,see what the watt draw is just on the converter(NOT inverting, just in idle mode) See if there are any parasitic loads, drawing power when not in use (indicator lights, clocks, etc.)...if the reefer is plugged in 24/7, unless you have a sunfrost or one of the solar special reefers, that , by itself can be to much...Solar pwer, off grid, is a science....every watt you use must be minimized, and "normal" life, as far as power , does not exist. If you aren't using either CFL's or led's for lights, your done right there....every appliance should be "energy star" at least....And from what i have read, a pump is a MAJOR draw....Not to say there isn't a problem with wiring, short, or ???? but remember, most people on off grid solar will tell you"you need to adapt to your system, it WON'T adapt to you". It is a lifestyle change....Good luck, visit those sites...and plan on spending about $3000.00-1000.00 for a system that will do what your asking....rsbhunter

rdpecken

Here is the best forum I have found for off-grid battery discussions:
http://www.wind-sun.com/ForumVB/forum.php

Go to the Solar Beginners Corner section and post your questions there to get very in-depth and (in my opinion) accurate answers.

Given the list of devices you have listed, my first guess is that you are expecting too much from your 4 batteries.
But only the correct use of your kill-a-watt meter, and some simple math will tell you for certain.

Also, here is a nice FAQ that discusses deep cycle batteries:
http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery Charging

Good luck...
Randy

alex trent



.and plan on spending about $3000.00-1000.00 for a system that will do what your asking....rsbhunter


I take it you meant $3,000 to $10,000.

Nahhh

I have spent $1,400 and my system is giving me all  want. I have a little problem right now as I described, but that will get solved and likely will not cost anything.

I have adapted my use to my system...that is a forgone conclusion on a small system.  if you want to build a big system to either live like you do on grid...or just to have a big system, you will not have to adapt but, as with most things in life can make up for it by spending money.

You machine hogs need to quit feeding info about how complex a system has to be to do the job. 




Buckeye

I know that my cheepie inverter draws quite alot of power when it is idle. The cooling fans on inexpensive inverters draw alot of juice. I'm not familiar with the brand you are using, but might be something to consider.


rsbhunter

Machine hogs???  The system i'm putting together is a complete off grid system.....i'm 5 miles from the nearest power pole, and at 10,000ft. I don't have the luxury of connecting to the grid.......and i only want to build this system once.....It's not bad to start off small, and build as you can afford...i talk with guy's every week that have done that...but after alot of research, and talking to people who have, and are ACTUALLY living off grid, to the person, they will tell you that if they could have, they would rather have more than needed, than less.....And bring your battery bank down below 50% charge a couple times, and you'll have the privilage of buying new ones.....If off grid is your only option for power, then do your research....if it's just a getaway cabin, then no big deal......but when it's your life, then buy once, cry once.....rsbhunter

alex trent

You said in another post you had a 3.5 KW genet and were going to get another...4 to 6 K, I believe you said. That plus the solar.

I would not worry too much about having enough juice to run the washer/dryer and the pizza oven.

I do have a total off grid place (not a mental one, but one that exists). Works a lot different for me...hard to see where all that power is going to go with yours, especially since you know about having to adjust your power use off grid...which you graciously gave advice about.

If you really want to make the batteries last, many say do not go below 70%.  Better yoet, they will last forever if you don't use them at all.

BTW..no need to get al freaky about DOD greater than 50%. Once in a while will not do anything you are able to keep track of and other things have as much or more impact on life than that.

here is a  interesting fact.

50% DOD  1150 cycles.

70% DOD  760 cycles

For me at 2x a week that is 11.5 years vs 7.5 years...assuming I went to 70% DOD all the time.  Nothing to get your shorts in a knot over. In 7.5 years I have to buy $400 worth of batteries. You have to do it 4 years later and I live longer not worrying about discharging to..... OMG 80%..

To me off grid means living a bit more frugally, physically and mentally.  Different stokes for different folks. That is basically all I am saying. Let's not leave it with the unanswered impression that your way is the only way or the best way.

alex trent

I know that my cheepie inverter draws quite alot of power when it is idle. The cooling fans on inexpensive inverters draw alot of juice.

Good point...I just read my specs...looks live about 2 AMPS...a lot more than I thought.

In 10 hours the inverter runs draws more for itself than I normally use in a day.

rsbhunter

As far as batteries, i'm looking into iron-nickel...said to have a life of approx 25 years, or longer...when they stop keeping a charge at a recommended level, you change the acid in them, and your good to go another ??? years....Like stated, all you need is money (and i'm good at saving ).......i don't tout large systems.....i do suggest figuring on Murphys law, and try to have a 25% overage cushion...so my 10 panels might be alot more than i need, unless i get 3-4 days of snow, clouds, etc, and only a couple of hours per day of sun....Worst case scenario i understand, but, life happens. And there are alot of inverters out there available that are alot better suited for off grid living, instead of the walmart plug my stereo in types, but if thats what you can afford, then til you can upgrade, it's fine....All i'm saying is size your system for your needs, and be realistic about all considerations, now AND in the future.....(and to the generator situation, this one is a gas,small  emergency type generator, my real solar charging, backup will be a diesel or propane ) As far as not worrying about 70%-80% of discharge, i would suggest some time is spent doing research on what the honest to goodness people that know these things suggest....websites for Trojan, Rolls-Surrett, and Deka all have guidelines for battery care....True, i can take a 30 watt panel, two golfcart batteries, and a coleman "1000" watt inverter, and light a light bulb......for a while...

alex trent

You seem to be confusing system size with component quality quality and also making assumptions about the quality of what other people operate...."Walmart pug in my stereo types".

I don't disagree with what you say about sizing correctly. And, with not being too optimistic about power needs and supply.  That is pretty basic stuff that most of us with these systems have figured out and done.   I, for instance was going to go with four batteries but given my experience with low watt lighting and finding oil lamps satisfactory, did three. I have no pumps, but will have a small fridge. Cost is not a concern as it only adds a fraction of the cost of the build. Just do not need the other one. would not do any harm , but then why not five or six?

Have you actually done any of this or lived off the grid?

Yeah, others do know about all the resources available for info about this..from battery manufacture and others (some on here). And use it too.

Actually, golf cart batteries work quite well.


MountainDon

Have you tried charging the batteries up to full and then leaving them totally disconnected from everything? That can assist in determining if a battery is just plain bad.

Then you need a good meter that can measure DC amperes. Place that inline with the pos or negative battery output. The meter must be capable of handling the DC current of any device you attach to the system. Then try connecting one thing at a time.


My experience has been that old RV's can be a problem.

Just because something has been done and has not failed, doesn't mean it is good design.

UK4X4

I have a similar problem on my brand new trailer- seemingly with a 100 amp charger/ convertor, even after 7 hrs of charging off a 6500watt onan generator

Seemingly I can't recharge the batts to full..........

My fridge on propane draws only 1.2 amps which is not much and my batts are only 160amp/hr

I only have lights and the fridge on the 12V - not even an invertor

This summer I'll be going to 4 off golf cart batteries too, and my problem will become worse at 440amp/hr at 12V

Using the RV generator is way overkill for just charging the batts- its sized for 2 AC and full house electricity

Is your fridge a propane one? or an electric one, as they can be power hogs, especially older models.

It looks to me that generator battery charging is not the best, and in my case I either have to add solar- or a second battery charger to run in paralell.

Just to be able to refill the batts after usage.

the RV lights I've since found out are 50w 12V halogens...........thats 4 amps each bulb !

So they will be history and swapped for some LED's, from DHgate ---------0.9watts for the same light output aprox $60usd for 30 LED lights

Its surprising where the current goes !

I had my batts returned to the supplier- the test routine from the manufacturer  was charge for 48 hours before doing the test.............thats a hell of a lot of gasoline !

MountainDon

UK.... yes as you have found battery recharging with a generator is inefficient, especially when it comes down to the last 10 - 15% of charge. The final charge takes a fairly high voltage along with a fairly low amperage. Generators use almost as much gas for the final charge as if the batteries were highly discharged. A genset is better at the initial or bulk stage. Solar makes a fine finishing tool where a genset is relied upon for the bulk charging.


And the converter / chargers that come with many RV's suck as you've also discovered. Often their float is too high as well. Relying on a built in RV charger results in more battery sales, IMO.
Just because something has been done and has not failed, doesn't mean it is good design.

alex trent

Does only going to 90% hurt (much)..hardly seems worth it for that extra 10%.

What about a forced 10 amp charge for the last hour (10% in a 100AH battery). I bet that is not optimal, but how much does it hurt the battery, if at all?


MountainDon

Charge to only 90% frequently and the batteries will fail early. Charging to only 90% of capacity as normal practice, will allow sulfation of the battery using the 10% of battery chemistry not reactivated by the incomplete charging cycle. So, yes charging to 100% is worth it, IMO. Not by generator but by solar; also IMO.

Quote... forced 10 amp charge for the last hour...

How much will it hurt the battery?  First, it'll use more water so that equals more maintenance. It will probably get too hot with a forced high amp charge when nearly full; that is not good for the battery. Quality PV charge controllers and inverter/chargers will monitor the temperature and reduce the charge if the battery gets too hot. This is to improve battery last. This can be even worse with a sealed battery as the high current and temperatures may cause fluid level to fall, and being sealed water can not be added. Of course anyone can do what they want to, and the odd thing to me is that many folks running off grid really do abuse their batteries either intentionally or from ignorance.

C/8 to C/10 is the usual maximum charge rate recommended for a battery, but that is only during the first stage, the bulk charge. ( where C=battery rated capacity).
Just because something has been done and has not failed, doesn't mean it is good design.

alex trent

Thanks for the reasoned analysis.

Solar is poor option as my side of the mountain is cloudy a lot. I think when I do the tight calculations, it will not be a good deal.

So, I think my next best is a couple more batteries. This way the slow charge is slowly charging more batteries...say 1 amp for 5 batteries vs 1 amp for three. will take as long, but be more efficient. And with that can run genet one in 4 days not 2.  I know, now you are going to tell me I need to bring up to charge every day. I'll have to live with not doing that.

I have asked Trojan for their take on this.


MountainDon

#20
More batteries may mean another charger to be able to get the most practical "push" into them. Or is the present charger much larger than needed for the present battery(s). . (sorry if you mentioned those details... I have trouble remembering what everyone's equipment base is.)

Even cloudy daytime skies produce power, albeit in smaller doses. Just the thing for topping up a battery after being given a generator powered bulk charge. But the modules need to be able to produce a high enough voltage with the combination of clouds and summer temperatures.... something that may not be possible without a panel series and an MPPT charger.  I have to admit to having many times more sunny days than cloudy days so in the main we don't have much to worry about unless it is darkly cloudy for three days in a row.


Download the Trojan User's Guide?  They specifically state "Batteries should be fully charged after each use." Also show charge profile graphs for different battery types.
Just because something has been done and has not failed, doesn't mean it is good design.

UK4X4

So going back to the original post

He should have enough battery power - same as my planned bank -440amp/hr at 12V- giving a 220amp/hr working capacity

But I'm guessing the fridge and lights are consuming more than he can return daily from the generator, the same as me

My light consumption came as a surprise, I never would have considered they would have used such high current lights
and they are in banks of 6- thats a huge load for a small battery system.

To me 440amp/hr of batteries should be well sufficient for a small RV-cabin system- the load however needs to be considered.

Reading up on my charger convertor the 100amps is total power, if I have the lights on, radio- that takes away from the charge power- as its 100amps total power - not just charging.

ie if your running the fridge and lights etc while charging you have to discount that from the power to your batts

I think I'll be ading 440ish watts of solar and a dedicated battery charger for solar and another for generator power.

The solar really for the top up, as during the day we have low consumption, nights are really the power hog - watching dvd's with my daughter, but thats also when we run the generator

One thing I was considering, not sure it would work- but rather than have another charger in the system covert mains to the same voltage as the solar panels and just have one large charge controller...anyone tried that ?




MountainDon

Quotebut rather than have another charger in the system covert mains to the same voltage as the solar panels and just have one large charge controller...anyone tried that ?

Attempting to make different sources function properly with the different sources running through one controller is going to cause problems apparently. The same question has been asked on the Outback forum and the user members had reasons as to why it was a bad idea. The info is lost somewhere in the depths of my RAM (Really Awful Memory).  Probably something to do with the fact that the voltage from the PV modules can and will vary all over the place as the lighting changes. EG; I've seen out system  (Vmp, 28.5 x 3 = 85.5 total) module output vary between 50 or 60  something to over 90 volts, with cold weather momentary peaks as high as 141 volts.
Just because something has been done and has not failed, doesn't mean it is good design.

alex trent

A few thoughts about the original post. I am working through the same thing..kind of. Lots of different possibilities...not all relate dot one another, but any one can be the culprit.

All my thoughts are for genet charging only...no solar for me.

1. I did not get what your total AH was, but running a fridge..even a small one..can drain a lot in 12 hours.  Many run 60-80 percent of the time and even 300 watts is 2.5 amps an hour.

2. My batteries go to 80% real quick and then to 100% real slow. This is normal with today' smart chargers meant to save the battery.  So you may only be getting part of what you think you are putting in.  For me, the total time I will have to run the charger (genet not nsolar) is way long..like 6 hours to get it all done from 40% discharge. I need to figure a way around that.  The main problem here is that chargers drop to low amps..say 1-2 per hour when you get to 90-95 %..so it takes a long time for the last little bit. Some say forget the last bit and others say that will hurt batteries. How much it hurts is just a guess.  If it drops you from 1000 cycles to 800...for me worth it.  i have a call in to Trojan.  Charger people..Iota... say its an art form not a science. My solution if not really critical to charge to 100% is to add a coupe of batteries and be more efficient in pumping in amps as genset runs.

3 Reading the batteries with voltmeter will show higher voltage than you have for 12-15 hours after a charge. An hour after will be 0.2 higher or more...so you may be overestimating your charge...see #2 above..

4. I have been told new batteries will not take full charge until 10-15 cycles.  I am at about 10 now.

5. My inverter draws 2 amps just to run...in the specs, not measured

hpinson

A charge controller with a monitor that display  PV output amps, battery voltage, and load draw amps, is really instructive.  It has been an education watching that throughout the day, as conditions change.