3 tons
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You didn’t mention the size of your MW, but if it ran good using GC’s, you’ll have no problem with two LFP’s… Microwaves are a reactive (capacitive) load, and LFP’s are well suited for such loads because of very little voltage sag…Also, it’s not uncommon for a 100a/h LFP to be capable of discharging at up to 200amps for short periods of time (with time increasing at lower discharge amps…), meaning the amp hour rating (capacity) is not always indicative of its typically greater (amperage) discharge ability…
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deltabravo
Spokane, WA
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time2roll wrote:My 4x GC2 needed 165 amps to run the MW. My lithium needs about 145 due
Actually it's the inverter that "needed" that amperage to run the microwave.
If the batteries "needed" amperage, they'd be charging.
In your scenario (batteries providing power to the inverter, to run the microwave) the batteries are discharging.
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otrfun
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12thgenusa wrote: . . . Does anyone have experience operating the microwave with 200 Ah of lithium? Important to note, Ah (amp-hour) and A (amp) are two different ratings.
A 200 Ah lifepo4 battery with a 100 A continuous current rating will not run the vast majority of microwaves. A 200 Ah lifepo4 battery with a 200 A continuous current rating will run most any microwave.
A similar caution applies if you have plans to parallel two 100 Ah lifepo4 batteries to obtain 200 Ah. Make sure *both/each* of these two 100 Ah batteries have a 100 A continuous current rating (*not* 50 A). Two 100 Ah batteries, each with a 100 A continuous current rating, paralleled together, will provide 200 A of continuous current.
* This post was
edited 03/12/23 07:36pm by otrfun *
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12thgenusa
Loveland, Colorado
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otrfun wrote:12thgenusa wrote: . . . Does anyone have experience operating the microwave with 200 Ah of lithium? Important to note, Ah (amp-hour) and A (amp) are two different ratings.
A 200 Ah lifepo4 battery with a 100 A continuous current rating will not run the vast majority of microwaves. A 200 Ah lifepo4 battery with a 200 A continuous current rating will run most any microwave.
A similar caution applies if you have plans to parallel two 100 Ah lifepo4 batteries to obtain 200 Ah. Make sure *both/each* of these two 100 Ah batteries have a 100 A continuous current rating (*not* 50 A). Two 100 Ah batteries, each with a 100 A continuous current rating, paralleled together, will provide 200 A of continuous current.
That’s exactly what was stated in the OP.
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StirCrazy
Kamloops, BC, Canada
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12thgenusa wrote:I’ll make my question a bit clearer.
When I designed and installed my system 12 years ago, lithium was still a dream for RVs. The battery discussions revolved around whether it was best to use a 12-volt battery or multiples of them, 6-volt batteries in series, or break the bank and go with AGM.
At the time, most agreed that a pair of GC2s in series were marginal to operate a microwave. That convinced me to go with four GC2s (440 Ah).
My specific question is, are the characteristics of lithium batteries sufficiently different from FLAs that 200 Amp hours of lithium batteries with at least a 200 amp BMS will operate the microwave without voltage sag causing inverter under-volt alarm or shutdown?
Should be, is not a helpful answer.
if you had a 200A BMS in one battery it would operate a microwave nice. two no problem.. the advantage of LFP is there is alomost no voltage sag undel load (there is but it is small) that is why you needed 4 GC instead of 2 as with only two the voltage sag when they get to about 80% of capacity will start your alarm going on the inverter. the LFP will stay above the alarm voltage untill they are down around 5ish % capacity.
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otrfun
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12thgenusa wrote: . . . My specific question is, are the characteristics of lithium batteries sufficiently different from FLAs that 200 Amp hours of lithium batteries with at least a 200 amp BMS will operate the microwave without voltage sag causing inverter under-volt alarm or shutdown?
Should be, is not a helpful answer. Here's a lifepo4 C rate discharge curve at 25c (77f) that may help you better understand the voltage drop that occurs while powering a microwave with a lifepo4 battery. Multiply the voltage in the graph by 4 for a 12v lifepo4 battery. Smaller .7cf microwaves will draw approx. .5c using a 200ah lifepo4 battery. The average microwave will draw .6c - .75c.
As a lot of folks have already confirmed, a 200ah lifepo4 battery with a 200a continuous rating will power a microwave. The only thing that can derail your plan is voltage drop due to the use of too small of cabling. As long as the voltage drop between the battery terminals and the input to the inverter remains below 2% (at 150a) you should be able to access almost the full ah capacity of the battery. Inverters typically start experiencing low voltage alarms (and cut-off) when the input voltage drops below 11v. Assuming less than 2% voltage drop, you should be able to power a microwave with a 150a draw down to 5-10% SOC with a 200ah lifepo4 battery before the inverter low-voltage alarm activates. This equates to a bit more than an hour of runtime.
We use a 200ah lifepo4 battery to power our 11k BTU a/c unit (and small microwave). They both draw roughly the same current (105-110a via inverter). While powering the a/c, we've inadvertently discharged the lifepo4 down to low-voltage cut-off (2.7v at cell level or 10.8v overall) many, many times. After two years of doing so, we've never experienced an inverter low-voltage alarm or shutdown.
![[image]](https://i.imgur.com/icbp8MFl.jpg)
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