Battery recommendation? Whatcha running?

[chin_k]

Very few battery setup can handle microwave, since it is 1kW. You need to fire up the gen set when you use that. Same for the heat pump on the roof, but I guess you will be using the propane, so only need to power the controller, which is not too bad. Otherwise, you need to fire up the gen set when you turn on the AC/heat pump. I don't think you can use your coffee maker either, but I don't know how many watts it is going to pull. I assume you have an inverter to run the coffee maker?

Nothing else in your list seem to be a big drain, and you maybe able to do with just one battery if you use the generator whenever you use your nuker (microwave) and your stinker (to people who don't like coffee). You may want to setup both batteries for the extra reserve, since the solar is not going to do much to charge them (more to maintain/top-off the batteries), and you really need to get the generator or to be plugged in for a few hours every day to charge them. I only say you maybe able to get away with one battery if you have nothing to use the battery after you are done with it. If you want more enjoyable time, connect both batteries (in parallel, obviously).

I hope Blue and other can chime in. You may want to tell us how many Amp hour your batteries are. We need the number to figure out how many minutes you can run the inverter when you pull 1kW on it, if you have to do that. I won't.

[68camaro]

Thanks, the 20 hr Ah is 65 so two will be 150 Ah. Inverter is 600 watts and microwave is probably 1000 as you say. Microwave can be missed but I do need my coffee. Camping will be crowded so really don't want to run generator until later in am or early afternoon.

For those that do not have slideout tray, how do you keep batteries stationary and not sliding around?

[chin_k]

150 Ah at 12 Volt, and let's assume you don't want to drain more than 50%, that will be 150 A*h * 12 V * 1/2 = 900 W*h. Assume that the inverter is 100% efficient, it will run it at 600 Watt for 1.5 hours continuous. Take a look at the coffee maker, and see how many watt it takes. Then you have to worry about other smaller items like water pump, etc., which probably will be less than 10% or 90 W*h at the most.

As for the securing the battery, it is important not to get them to bump around. Here is a thread on it here:
viewtopic.php?f=13&t=1246

[BobW9]

Note that batteries do not have the same AH at all discharge rates. The higher the discharge rate, the lower the Amp-hours the battery can supply. In addition, generally, the cheaper the battery, the less AH you will get at higher discharge rates.

I believe this goes for all batteries, except the Lithium which have a nearly flat discharge rate (a 150 AH Lithium will give you close to 150 AH even if you're drawing a 150 Amp load).

In other words (using the info of the link further down), if that inverter is running at it's maximum rate of 600 watts, call it 48 Amps, 150 AH of cheap Lead Acid batteries will probably go down to 50% in 10-20 minutes. They simply can not handle a heavy load. If you get quality AGM batteries (with a low Peukert value), you might get an hour and a bit at the 50 Amp load before its down to 50%.

See this link for a chart on average capacity of a 120AH battery for various Peukerts values. The Peukert value changes on battery type, and to a lesser degree on quality of manufacture. Regular (and cheap!) Lead Acid batteries have the highest Peukert values, and so will have the quickest discharge at higher Amp loads.

http://www.rialtainfo.com/vw/engine_battery_002.htm

The better manufacturers will have the values for their batteries on their websites. The cheaper ones will probably not (not to their advantage when trying to sell!).

Nothing is ever easy or clear, eh?

Bob

[pdemarest]

I'm running two AGM 6 volt batteries, each rated for 150 amps for a total of 300 amps. They were too large to sit in the original tray so the installer removed the tray and mounted the batteries on their side.

[dougm]

what did you end up doing?

[kdarling]

Thanks, the 20 hr Ah is 65 so two will be 150 Ah.

If it's 65 Ah, two would be 130 Ah

I'm running two AGM 6 volt batteries, each rated for 150 amps for a total of 300 amps.

Two 6v x 150Ah batteries in series to make 12v is still 150Ah.

Very few battery setup can handle microwave, since it is 1kW.

Earlier this year I decided I wanted my passengers (grandkids etc) to be able to use the microwave for little things while going down the highway... but without turning on the generator.

Since I'm a '94 with the single coach battery under the hood, that meant first moving the battery to be near to the inverter, so I decided to use the extra window-side space under the rear dinette seat. This also allowed me to put the inverter and its remote control right by the microwave.

1. As the battery would be inside, I decided to go AGM with just a couple of circular vents on the front of the seat in case it ever got overcharged.

2. My new microwave is 900 cooking watts, so I knew it needed 1.5 times that for power, or about 1350 watts of 120VAC. With inverter inefficiency, that turned out to be 150A continuous draw @11.5V or about 1700W.

3. Most 100Ah batteries only allow max 100A draw. So I went with a 100Ah AGM battery specially designed for high power audio equipment etc... the Kinetik HC-2000 REV. It's a 2000W continuous output battery (166A @ 12V), which was perfect. I'm easily able to run the microwave for five minutes to do popcorn, heat coffee etc.

4. Surprisingly, when my engine was running, the draw dropped to 100A! Apparently even at idle the (130A?) stock alternator was making up the other 50A. Neat! And this has me thinking about replacing it with a 200A output alternator.

--

5. Later, because I wanted to be able to use more than about 50Ah, I replaced the AGM with a LiFePO4 batter from Dohon in China. I had been wanting to go lithium to save weight and get more usable Ah, but the final push for me was eBay having a one day 10% off everything sale. That lowered the price of the Dohon 100Ah RV battery from $650 to around $585 with free shipping. Wow. It was a no-brainer at that price!

Why not the popular (and more expensive) Battle Born? Because those are limited to 100A continuous. The China battery I bought is rated for 300A continuous and 1500A for a few seconds. Heck, I could run the roof A/C off that!

I will post some pics later. Just wanted to say that running the microwave off even a single battery is possible with the right battery.

Kevin

[chin_k]

Is there review or testing of the Dohon battery? I am not too comfortable taking the 300A continuous number from a Chinese manufactor without third party verification. It will be interesting to see how the various components and connection in the system behave when drawing 1500A

The engine/alternator essentially is little gen set so it really helps with the battery when you were making pop corns. If they ever come up with a hybrid chassis for RV, it maybe possible to get away with generator all together. The Chevy Volt, for example, has a 55 kW generator under the hood, not that it is any good for converting to a RV.

[Blue~Go]

4. Surprisingly, when my engine was running, the draw dropped to 100A! Apparently the alternator was making up the other 50A. Neat! And this has me thinking about replacing it with a 200A output alternator.

This is essentially how I set up my "I only need a generator a few times a year for five minutes (and yet I'm carrying around a second engine)" system.

My uses are for a heat gun (shrinking wiring connectors), vacuum (usually when using a tool), or tool (a few of my tools aren't battery powered, such as the Multimaster). This is vanishingly seldom, but they are things I want to be able to use even if only infrequently. Other than that my 110 uses are all satisfied by a "cigar" plug in 75W inverter (re-charge toothbrush battery, basically).

I have a 375 amp hour AGM house bank, but I'd rather not subject it to big Peukert loads (such as the tool uses above), especially if it's not sunny. A friend had a big, thirsty, 2000 watt inverter and a similar start/house connection to mine -- plus a battery monitor -- so I did some experiments before setting up my system.

Upshot is, my "system" works great for my purposes. The setup is that I installed a 1500 watt modified sine wave inverter next to my house bank (under $200 for inverter/wire/fuse/etc.). I had already 1/0 cabling between the start and house banks, plus appropriate fuses on both ends at the respective batteries. And also, I'd already converted to bus bars and etc for my main DC setup - that made it relatively simple to add the inverter.

When I want to run one of aforementioned tools, I start my engine, turn on the inverter, and away I go. All else being equal, I try to do it when the sun's out so there is that incoming solar power as well. The result is I can do the short projects I want to do and there is no big hit to my battery bank. Neither is the alternator supplying too much power. (I can read this in real time on my BMV meter.)

Would I do this for more than an occasional few minutes? Nope. The V10 and its alternator are not meant for that. But once in a while I'm fine with it. If it were more than once in a while for a few minutes, I'd use the "real" generator (which I really should remove for my use case!).

[kdarling]

Is there review or testing of the Dohon battery? I am not too comfortable taking the 300A continuous number from a Chinese manufactor without third party verification. It will be interesting to see how the various components and connection in the system behave when drawing 1500A

RC hobbyists are used to yanking 15C rates from lithium.

As for max continuous output, that partly depends on the electronic switches being used internally. It's clear that Dohon uses heavy duty ones since they're not afraid of 300A continuous, same as several other LiFePO makers. Battle Born is the wimp of the bunch.

The lithium cells used in most American assembled batteries come from China anyway. (Including no doubt BB lithiums, since they carefully avoid saying otherwise.) Same as with solar cells made into panels by American companies.

Oh, did you guys see that Trojan is about to sell their own lithium batteries? And they provide decent lab data, unlike Battle Born. A lot of people think this is gonna cut deeply into BB sales.