Power inverters - Hints? Tips?

[djf]

I am curious about FReepers experiences/recommendations regarding power inverters.

I managed to snag a CPI 1550 Cobra inverter today. Took a little bit of cleanup and blowing out dust, etc., but tested fine.

Anyone know how to convert from CCA (Cold Cranking Amps) to life cycle/watt hours output?

Thanks!

[diverteach]

http://www.boostinverter.com/faq.html

[cripplecreek]

Don’t stick your tongue in it.

[djf]

Thanks!
Helped answer a few questions.

[virgil283]

“They are not really directly related (other than with a physically larger battery—both will be larger than a smaller battery).
Problem is that Batteries with a CCA rating (Cold Cranking Amps) are designed to start car/truck/boat engines. These are not storage batteries. Starting batteries are designed for a maximum discharge of ~15% maximum (85% State of Charge)...

Deep cycle batteries are designed for an 80% maximum discharge (20% state of charge), and are not designed to provide short bursts of high current (and be of lightweight design—as need for a car). And even then, 80% cycling is still very hard on deep cycle batteries.”

[RFEngineer]

With lead-acid batteries, the life span is not dependent on CCA, it’s more dependent on Depth of Discharge and number discharge cycles.

A typical AGM-type battery (recommended) would give you approximately 1000-2000 cycles if you limit discharge level to 50%.

A standard car battery would probably give you far less than that, an a deep-cycle marine/forklift battery would be somewhere in between.

As a design guide you’d look at the typical loads you’d be powering, double the amount for battery capacity.

If you wanted to go exotic there are lithium batteries that can outperform in terms of depth of discharge and number of cycles.

I’m operating from memory - so may be sketchy but the numbers are ballpark - if you’re really interested freepmail me and I’ll get more details for you.

[bigheadfred]

HEY MAYBE IF WE PITCH IN WE CAN GET ONE BIG ENOUGH TO PLUG INTO WASHINGTON DC AND RETURN THE POWER TO AC--American Citizens

[Doogle]

*LOL*

[djf]

Thanks for the tips!
I have a generator, which I test and do minor upkeep on a couple times a year.

So I see my use of batteries/inverters as a short term solution until I get around to getting things hooked up and the generator going. I expect I would not run off an inverter for more than ten hours or so.

[PeaceBeWithYou]

Apples and oranges.

CCA(Cold Cranking Amps) is a rating for starting batteries.

RC(Reserve Capacity) is a rating for storage batteries.

Since starting batteries are designed to deliver high amps for 10-20 seconds at a time during starting, and replace that charge quickly afterwards, their reserve capacity is skewed to that task. This type of battery usually has 1/4th or less reserve capacity of a storage battery, and will not last long as a storage battery because it isn’t designed to be deeply discharged.

What you want to power an inverter is a deep cycle large reserve battery or bank of batteries that can supply a lower amperage over a longer time period.

[cripplecreek]

I thought it was a pretty good tip. Very useful.

[RFEngineer]

perfect application for it. in that case don’t worry about depth of discharge - you won’t be regularly deeply discharging it. Keeping battery on trickle charge should give you a decent lifespan for the battery itself.

[PeaceBeWithYou]

In that situation, you’d want a charge controller to charge and maintain the battery or batteries from line power, and then switch over to the generator after they discharge to 80%.
Then the generator runs supplying the inverter and charges the batteries at a safe rate, then it shuts off and you run on the stored charge until the cycle repeats.

Home Power Magazine is a very good source for just about anything you can think up. Back issues are available on CDs and DVD for not much, as well.

[norwaypinesavage]

Here are some tips:
The inverter is designed to supply 1500 watts continuously. That's a little less than what one 15 amp circuit in your house provides. That's not enough to run water pumps, air conditioners, most electric cooking devices, or hair dryers.
Don't charge batteries that are hooked up in parallel. Separate them for charging. They will fail quickly if you charge them together. You can also buy isolators if you want to charge them together.
It takes a little more than 10 amps into the inverter to produce 1 amp out. (It's actually more like 12 to 13 times because the inverter isn't completely efficient). Since the battery reserve capacity is based on 25 amps from the battery, that's about 2 amps out of the inverter, about what it takes to light 2 100 watt bulbs. Remember, though, that running a battery to its reserve capacity limit severely degrades its life.

[Texas Fossil]

Or we can all make a visit to DC armed with souped-up cattle prods.

Under the right circumstances it might be more effective than torches and pitch forks.

[phockthis]

http://www.alpha.ca/web2/products/batteries/batteries/item/alphacell-gxl-gelcell-batteries

[Usagi_yo]

Amp-Hours — the amount of current a battery can supply until it’s supply voltage is no longer useful.

Duty cycle — the max amount of time a battery can be used before it needs to be turned off. Deep cycle batteries would have long duty cycles. Starter batteries would have shorter duty cycles.

Temperature rating — generally obscure and not necessary for general use. In general, the higher the temperature the quicker the battery will deplete under load.

Max Load — the maximum amperage the battery can provide. Generally >> than the amp-hr rating, but the total amperage is still confined by the amp-hr rating. Meaning a 40amp-hr batter running 50 amps will deplete 25% sooner.

CCA — similar to max load but specific to a known short duration. IIRC that’s 15 seconds.

Finally

Volts X Amps = Watts. So a 12v batter powering a 120 watt circuit for 10 hours would need 120/12 x 10 amp-hr rating (100 amp-hr).

Loose industry standard is to derate by 20%, which would be ((120 / 12 x 10) x .20) + 120 / 12 x 10 or 120 amp-hr rating.

I hope I got that all right.

[Usagi_yo]

Here are some tips:

Check your work ... I believe you have some things incorrect.

[norwaypinesavage]

E=IR, W=(V^2)/R, Efficiency is about 70%

[al_c]

I hear they have some good ones in Toshi Station. ;-)