Front Compartment Workshop

[notnsuv]

Ordered the Xantrex 2000 from http://www.donrowe.com just now.
Also ordered the complete solar setup from AMSolar.
Might be ready for archery elk season in Montana.. opens 9/16.

[Jim and Lonnie]

Loook at the math on your needs, my 337 has gone to all LEDs lights which helps alot on the lighting pull on the battery. it looks like the Samlex is a good unit, just look at the reviews. What is the warranty on the unit? Any problems with getting response from the company. I like the fan idea, but the battery is in a box that is vented to the outside. I think that moving it to your basement is good, easy access to the unit? Just look at spaceing around the unit and how much cable, shorter is better for the lost in voltage. try to keep it simple. I was look at just plugging the inverter into the shore Power input and unpluging the battery charger ( the WFCO unit) at first. keeping the air flow around the unit, it should work for years. Good stuff!!!

[notnsuv]

We have a medical device that will run all night at 3.4A AC. Will be interesting to see how 432ah hold up to it. Rule of thumb for solar is 1w/ah of battery so got 420ah in panels.
Heard back from Don Rowe today and he likes both inverters. He also said they handle warranty on the Xantrex for several retailers so will buy direct from them and have that end covered. It should work fine for me.

[Cate&Rob]

Hi Gary,

You do need to "check the math" on the exact type of batteries in your bank and recharge rate vs discharge rate.
3.4A at 120VAC will draw 34A at 12VDC. Because of inverter inefficiency, this will likely be closer to 40A.

The Ah "capacity" of a battery bank can be a little misleading. It is a good rule of thumb to size your discharge/recharge cycle to about 1/3 of the theoretical bank capacity. The reason for this is that the batteries should never be taken below 50% state of charge (this can damage them) and charging above 80% state of charge is a slow process that takes a long time. Good if you can get it, but not to be counted on. Thus, living between 80% and 50% gives you a 30% (or 1/3) range.

For your 432 Ah bank, 1/3 of this is about 140 Ah. Within this range, you will only be able to draw 40A for about 3.5 hrs.
If you can recharge above 80% this time will be longer, but the inverter will shut down when it sees a battery voltage roughly equal to 50% state of charge, to protect the batteries.

To really track charge/discharge, you need an Ah meter such as the Victron BMV702
http://www.victronenergy.com/battery-monitors/bmv-700
There are lots of other versions of this as well. This will track battery state of charge in terms of Ah and can be programmed to your bank size so that it gives you state of charge as a % of capacity.

Rob

[notnsuv]

Rob,

I'm reconsidering the whole solar setup and thinking of just using a quality stand alone charger. Since the converter in the 303 only puts out 4 amps it's unlikely I'd ever get back to 80% or better with either shore power or the generator. And even with 400W of solar it might be unlikely to recover the battery charge, especially on a less than optimal day of sunshine.

In the past we've had great luck with small solar setups for 2 12v batteries and economy of use but under the current conditions where we NEED to have good batteries I have to go with something more reliable than just the sun. I have a Honda 2000 and also wonder how much battery charger it will drive?

I'm finding 12v chargers anywhere from 10A on up to 40 and 60A. (http://www.donrowe.com/Xantrex-TRUEc...04-1240-02.htm). My understanding (limited) is that batteries should not be charged at a rate more than 20% their ah rating. So with my 216ah batteries (4 of them; 2 each in series and the pairs in parallel for 432ah) should I keep the amperage at or below 40A using the 216ah rating? Or is even that too much? Or can I go 40A or more using the 432ah rating of the two pairs? The Xantrex above is adjustable for charge rate so can take it under the 40A rate.

Is a converter/charger something I should consider? One of several I've found: http://www.donrowe.com/Xantrex-807-2...p/807-2055.htm
This also has to be Pure Sine Wave.

How's this battery monitor: http://www.amsolar.com/home/amr_1441...ic_2030-a.html

Thanks so much for your input (everyone)! I certainly don't need the expense of solar only to find it doesn't meet the need.

[Cate&Rob]

Hi Gary,

First off, the converter in the 303 will put out up to 55 amps at 13.6V. (See picture of converter . . . assuming yours is the same)
This would be to a battery that was discharged down towards 50%.

Battery charging is more of a "pull from the battery" than a "push from the charger"
As the battery climbs over 80% state of charge, its voltage goes up and the charge rate goes down, regardless of charger maximum capability.
No matter what the charging source, a battery approaching 100% can only be charged at a few amps.

So, back to the 140 Ah ideal range (50% to 80%), the on board converter will recover this in about 3 hours whether powered by shore power or a generator. In reality, probably more like 4 hours since charge rate will go down as battery voltage climbs.

The battery monitor that you found, is doing essentially the same as the Victron monitor that I mentioned. The large shunt in the wiring harness is the device that can measure amps in or out of the battery bank. Then the monitor can calculate this into Ah.

So much depends on how & where you camp. Dry camping with lots of full sun makes solar systems attractive.
Access to shore power leads to a different recharging plan. If you don't mind listening to the generator, that's another way.

Rob

[Paul & Deb]

Man Rob, you talk way over my head. I should have spent more time picking your brain about my setup while we were with you at the rally. I need to pick up a decent monitor system. Do you think this would be what I need or do you have some other recommendation?

http://www.solar-electric.com/trtmbamosy1.html

[Cate&Rob]

Hi Paul,

We were having too much fun at the Rally, to get into the "technical" stuff .

The monitor in your link should give you the info you need. I note that it doesn't have a button for Ah but reading the literature, you can find this number with a double button push. The % state of charge is based on Ah taken/added to whatever you program in as your bank Ah size. In my case (boat reference) I will sometimes switch in or out batteries, for different reasons, so my bank size can change. The Ah will still be correct but the % might not be. This is not important if your bank is hardwired and thus always stays the same size.

I note that the manufacturer offers a 100 A and a 500 A shunt. You will need the larger one because any inverter secondary draw over 10 amps at 120 VAC will draw more than 100 A at 12 VDC. A motor starting spike on the 120 VAC side can easily draw close to 200 A on the DC side. Make sure your 12 V wiring and fusing is sized for 200 A .

Rob

[Paul & Deb]

Hi Paul,

We were having too much fun at the Rally, to get into the "technical" stuff .

The monitor in your link should give you the info you need. I note that it doesn't have a button for Ah but reading the literature, you can find this number with a double button push. The % state of charge is based on Ah taken/added to whatever you program in as your bank Ah size. In my case (boat reference) I will sometimes switch in or out batteries, for different reasons, so my bank size can change. The Ah will still be correct but the % might not be. This is not important if your bank is hardwired and thus always stays the same size.

I note that the manufacturer offers a 100 A and a 500 A shunt. You will need the larger one because any inverter secondary draw over 10 amps at 120 VAC will draw more than 100 A at 12 VDC. A motor starting spike on the 120 VAC side can easily draw close to 200 A on the DC side. Make sure your 12 V wiring and fusing is sized for 200 A .

Rob

See, that's what I mean, you lost me after "The monitor in your link should give you the info you need".

I'm going to search for some others as well. I will check back for your advice on those .... I think

[notnsuv]

Rob,

I've attached a .pdf from the Xantex SW2000 inverter Owner's Manual describing wiring configurations. My setup has 2 banks of 2 6v batteries for 432ah total and the 2000w inverter like the "Heavy Load" config (sans vehicle battery and alternator). Question is: Do I need to get as elaborate as the "Heavy Load" config in the document with 2 Battery Selectors (one at Inverter, the other at "Other DC Loads"), an isolator (not in a vehicle), and a fuse at each + terminal of each battery? Would those fuses be the 300A ANL? If this config is what I need I'll do it but would naturally like to keep it simple. I don't know the need to switch between battery banks as I will need all 4 at night (see below). Give me the pros and cons please.

I have 3' of 1/0 cable to run inverter to battery, a 300A ANL fuse, and a 200A Circuit Breaker (kinda winging it with the circuit breaker and not sure it's needed or appropriate). Obviously a bunch more cable will be required for the "Heavy Load" config than the "Normal Load".

I'm running this config because of an O2 Concentrator that will be used nightly (not to be confused with a C-Pap machine). Even with the 4 batteries we'll get only about 4 hours or so of use from it and it will take approximately 4 hours to restore the batteries with a combination of generator power on the 55A converter and 400w solar power, split approximately 2 hours each. Of course, if the sun don't shine, the generator will have to run. The O2 ran 2.44 kwh in a 7.5 hour overnight test using a Kill-O-Watt meter from Home Depot (3.4a/120vac on the label).

P.S. Do I need to isolate the solar from the RV converter for charging? I don't recall any such requirement on my previous RV solar.

I appreciate your expertise and the time you take for us.

Stay at KOA is the easy answer but we're determined to not give up our dry-camping passion.