Using a deep cycle battery to temporarily cover additional wattage requirements?

lolcashcow

(Edited the first part of my post because i wrote it incorrectly. I had stated the dc to dc converter was what provided power to my induction cooker at 800 watts, but in reality the dc to dc converter is connected to the battery, supplying it power, and I have an actual inverter connected to the battery. The induction cooker being hooked up to the inverter)

I have a DC to DC Converter from a HV Battery Pack that provides about 800 watts of AC continuous power. It is hooked up to a lead acid  battery; a small one. I am in need of a little more power; about 1300 watts total to be exact. That means I need an additional 500 watts AC of power for cooking (Induction cooking). I am thinking on upgrading the lead acid to a deep cycle AGM battery to temporarily bridge the gap for about 30 minutes; that is as long as I will cook.

I'm new to this so I am trying to wrap my head around it. If the induction cooker uses 1300 watts in one hour,  and I need an increase in power of 500 watts, does this mean that for 30 minutes I will only need 250 watts?

I have a feeling I will need more than because there are some inefficiencies that come into play, but am I close to the required amount of power I need?

I am thinking my set up will look like this:

The inverter:  Xantrex prowatt sw2000 (1800W continuous 3000 Max Surge)
Copper Cables: #4/0 AWG (Cable length will be kept under 2 feet long)
http://www.amazon.com/Blue-Sea-Systems-5191-Terminal/dp/B0019ZBTV4
Blue Sea Systems 5191 Fuse Block Terminal 30-300 AMP  $17.57
http://www.amazon.com/Blue-Sea-Systems-250A-Terminal/dp/B0026KY6R0
Blue Sea Systems 250 AMP MRBF Terminal Fuse
Anderson SB350 Connector up to 450 Amps

To further worsen the case I will be using my Nissan leaf Electric car for this. To make things short the DC to DC converter can provide 800 watts continuous to the lead acid battery... which I will upgrade to a deep cycle AGM.

This type of upgrade has already been done:

http://www.mynissanleaf.com/viewtopic.php?f=27&t=11094&p=257288

He switched his lead acid to a Sun Xtender PVX-420T AGM Sealed Battery

http://www.solar-electric.com/batteries-meters-accessories/batteries/concorde-sun-xtender-pvx-solar-deep-cycle-batteries/12voagmba/concorde-sunxtender-pvx-420t.html

Which he says is smaller than the original lead acid (Meaning it could hold a somewhat larger battery). Here are the specifics of this battery

Voltage			12 Volts
BCI Group Size			U1 Tall
Ampere Hours @ 24 Hour Rate			42 Ah

I'm trying to figure out ampere hours here, but am I right to think that 42Ah is equal to 504 watts per hour?

I used first this calculator online:

https://lazycackle.com/Convert_from_Ah_to_KWh___Online_Calculator.html

Then the result was ran through:

http://convert-units.info/power/kilowatt/0.504

Basically:
42Amp hour @ 12 V = 0.504 KWH
Then
0.504 KWH =504 watts?

mike95490

lolcashcow said:

I have a power source that provides about 800 watts of AC continuous power (DC to DC Converter from a HV Battery Pack), and I am in need of a little more power; about 1300 watts to be exact. That means I need an additional 500 watts AC of power for cooking (Induction cooking). I am thinking on utilizing a deep cycle AGM battery to temporarily bridge the gap for about 30 minutes; that is as long as I will cook.......

Sorry.  I don't think adding a DC battery will improve the power capacity of your AC inverter.  The inverter components and heat sinks are only rated to dissipate the wattage of an 800W load.   It's not a battery thing, it's an inverter thing.

lolcashcow

I'm not sure if the battery is DC or AC, but the Pure sinewave inverter should be turning that current into useable AC? I don't understand how a fully charged battery would not be able to provide any additional current on top of the power coming from the DC to DC converter?

The way I was told is that the battery is like a tank and the water is the electricity. There is current coming from the dc to dc converter going into the battery then the inverter is drawing a certain amount from the battery. If the battery is full I don't see how the inverter would not be able to draw 1300 watts of power while the DC to DC converter will top the battery with 800 watts as it sees the voltage drop in the battery.

The battery having a capacity of such and such amount... the battery being already filled to the top... The only way I don't see this working is if the battery itself can also not provide more than 800 watts. The flow of ''water' being restricted ....?

The set up is connected like this:

DC to DC Converter to AGM Battery.
AGM Battery  to Pure Sinewave Inverter
Pure Sinewave Inveter to Induction cooker

The Dc to DC Converter suppling 800 watts to the battery (That has a certain amount of max capacity) which the inverter will draw energy from at 1300 watts per hour.

this is why I am trying to figure out amp hours as in how much power this battery can hold. It says:

Ampere Hours @ 24 Hour Rate 42 Ah

What is 42 Ah? 504 watts per hour?

What is the total capacity of the battery? How much electricity can it hold? I see 42 Ah @ 24 hours so is it....

504 watts * 24 hour discharge period? 12096 watts total Capacity?

Or 504 watts over a 24 hour period? 504/24= 21 watts? But if so 21 watts out put per hour seems rather useless... but it is a small battery... so I am trying to understand those points

The inverter I am using is:

The inverter:  Xantrex prowatt sw2000 (1800W continuous 3000 Max Surge)

It can provide 1800Watts continuously and can support a 3000 Max Surge. So the inverter isn't the limiting factor .... it can provide more than 800 watts.

Oh sorry mike it seems I wrote my opening post badly and the DC to DC converter is coming off as the power source (Inverter?) I will edit that. The DC to DC converter is just providing the power to the battery not the induction cooker.


Okay, here is the edit to the starting post:

I have a DC to DC Converter from a HV Battery Pack that provides about 800 watts of AC continuous power. It is hooked up to a lead acid  battery; a small one. I am in need of a little more power; about 1300 watts total to be exact. That means I need an additional 500 watts AC of power for cooking (Induction cooking). I am thinking on upgrading the lead acid to a deep cycle AGM battery to temporarily bridge the gap for about 30 minutes; that is as long as I will cook.

I hope this makes more sense

vtmaps

lolcashcow said:
I am thinking on upgrading the lead acid to a deep cycle AGM battery to temporarily bridge the gap for about 30 minutes; that is as long as I will cook.

How will you charge the AGM battery?  Does the built in charger for the original lead acid battery have adjustable charging parameters?  Usually an AGM needs different charging voltage than a flooded battery, and even if the original battery is AGM, its requirements may be different from your replacement.

Even if you replaced the original battery with a (larger) battery that required the same voltages, you might not get a proper charge... there's also a matter of time.  How does the built-in charger know when to finish absorb charge?  If it uses either time or end amps, the numbers will be different for a larger battery,

--vtMaps

lolcashcow

The DC to DC Converter charges the Lead acid battery which will be replaced with the deep cycle AGM. So it should charge it. The DC to DC converter charges the battery in its own way, but as far as I know you can't adjust it. Here is some info I found on that. I am hoping it answers some of the questions.


"The Leaf's DC-DC converter can supply up to about 1.7kW or 135a. This unit takes ~400v power from the traction battery and makes approximately 13 volts. (varies according to charge requirements of the 12v aux battery) It should be able to power up to 1.5kW of external load with no problems, provided most of the accessories are left off.

One interesting thing is, unlike the 12v system on a ICE car, there is almost no voltage sag. The DC-DC converter is a high-frequency switch mode converter, so it can respond very fast to high current surges, whereas a normal ICE car alternator cannot, and it's also RPM dependant for maximum output.

WARNING: NEVER connect anything directly to the negative post of the Leaf's 12v aux battery! This is a current sensor and doing so will disrupt the charging system! (Connect all accessories to the body ground, or, if high-current, the black wire screwed to the top of the DC-DC JB. (Behind the inverter)

Note: I have not tested it at full load for an extended period of time, so there may be some thermal limiting that could cause output to drop after long runs of high-current use.

Here's my test:


-Phil"

"You should be OK with the Leaf fully on and in park. The DC/DC converter will keep the 12v circuit energized at about 13.5 volts once the battery is topped up, and will drive your DC-AC inverter for as long as the 400v main pack holds out. (Probably a good idea to monitor it, but the Leaf will shut off when it's depleted.)

The DC/DC converter is water-cooled with a radiator and fan"

"The 12v battery is only "charged" when the LEAF is ON. Then the high-voltage (300 to 500 volt?) DC to 12 volt (nominal) DC converter might be capable of supplying 100 amps (or so)."

"

ht2 wrote:When the Leaf is ON, DC-DC converter is always on and supplying 13.5V or Turn on only when 12V battery is low?

Yes, when the LEAF is on it will always supply ~13.5v to make sure the 12v battery is charged.

Edit: Actual voltage is closer to 13.0V, not 13.5V."



"

kubel wrote:Sorry for the thread resurrection, but I can confirm that the LEAF can jump start another car without any issues while it's running. Connected positive and negative to positive and negative of the Crown Vic's battery, then connected positive to the LEAFs positive battery and negative to the top connector on the DC/DC charger. Let it sit for a minute or two and then hopped in the Crown Vic and it started right up with the LEAF running in park. Disconnected and no problems to report.

Good Job! You did it properly too!

I've done it several times now, and even charged two large 115ah deep-cycle batteries using the Leaf as an ad-hoc Lead-acid battery charger. It jumps/charges way better than most ICE alternator equipped cars!

-Phil"

I'm a little unsure how Phil used his leaf to charge TWO 115ah deep cycle batteries.... Was it just a direct battery to battery connection? Does this mean the leaf's charging system can handle more than one battery connected together?

vtmaps

vtmaps said:

How will you charge the AGM battery?  Does the built in charger for the original lead acid battery have adjustable charging parameters?  Usually an AGM needs different charging voltage than a flooded battery, and even if the original battery is AGM, its requirements may be different from your replacement.

Even if you replaced the original battery with a (larger) battery that required the same voltages, you might not get a proper charge... there's also a matter of time.  How does the built-in charger know when to finish absorb charge?  If it uses either time or end amps, the numbers will be different for a larger battery,

lolcashcow said:

The DC to DC Converter charges the Lead acid battery which will be replaced with the deep cycle AGM. So it should charge it. The DC to DC converter charges the battery in its own way, but as far as I know you can't adjust it. Here is some info I found on that. I am hoping it answers some of the questions.
<snip>

Nothing you wrote gives me any reason to believe that your AGM batteries will get charged.  Do you think that applying 13 volts to an AGM battery is the proper way to charge it?

--vtMaps

lolcashcow

I'm a beginner at all of this, but someone in the nissan leaf forum did change their lead acid with a deep cycle AGM (link above) and he has not reported any issues with it. So I would think it is being charged. How well is it being  charged I truly wouldn't know.

lolcashcow

Ok, so I am not good at this electrical stuff,  but I am SURE we can at LEAST trickle charge? the AGM battery?

From where to charge it? My initial thought was the 12 cig socket, but it is inside the cabin. How about getting a small pure sinewave inverter and hooking this one to the lead acid battery? Then hooking the AGM to the larger puresinewave inverter to help out the lead acid (Which is really the dc to dc converter) when demand is higher than 800 watts?

Thoughts on this Frankenstein approach?

vtmaps

lolcashcow said:

I'm a beginner at all of this, but someone in the nissan leaf forum did change their lead acid with a deep cycle AGM (link above) and he has not reported any issues with it. So I would think it is being charged. How well is it being  charged I truly wouldn't know.

It will be chronically undercharged and will lose capacity to sulfation.   Do you have a particular AGM battery in mind?  If so, go online and read the manufacturer's charging instructions.  As far as I know, you won't find any manufacturers that recommend 13 volts to charge their batteries.

I don't doubt that "someone in the nissan leaf forum" put an AGM in their leaf, but it may take a year or more before they notice a problem.   How soon they would see a problem depends upon how much they try to draw from the battery during the discharges.  

--vtMaps