Battery needed for 1200 watt inverter

[w28]

I was about the purchase an SOK 206 Ah battery, but was concerned by the 100A maximum discharge. I want to be able to operate a 1000 watt AC load for 15-20 minutes at a time (with charging in between). To be safe I guess I would want to size up the inverter to a 1200 watt rated inverter…which would then need ~120 DC amps.
Questions:

- is it necessary to size up the inverter, or can a 1000 watt inverter truly provide 1000 watts continuous.

- can the SOK battery handle this load?

- if not, should I look around for a battery with a higher maximum discharge (or learn to make a DIY battery with a higher rated BMS (Current Connected has a JBD BMS rated for 150A)).

Thanks in advance for any help you can provide. This would be used for cooking with an instant pot in a camper van.

 

[FilterGuy]

I was about the purchase an SOK 206 Ah battery, but was concerned by the 100A maximum discharge. I want to be able to operate a 1000 watt AC load for 15-20 minutes at a time (with charging in between). To be safe I guess I would want to size up the inverter to a 1200 watt rated inverter…which would then need ~120 DC amps.
Questions:

- is it necessary to size up the inverter, or can a 1000 watt inverter truly provide 1000 watts continuous.

- can the SOK battery handle this load?

- if not, should I look around for a battery with a higher maximum discharge (or learn to make a DIY battery with a higher rated BMS (Current Connected has a JBD BMS rated for 150A)).

Thanks in advance for any help you can provide. This would be used for cooking with an instant pot in a camper van.

Let's work through this.

1) I agree that running an inverter at 100% for more than a very short period is asking for problems, so let's assume a
1200W inverter.. However, if you are sure your load will never be over 1000W, then we can use that for calculating current.

Smaller inverters tend to have low efficiency, so let's assume 85%. That means the battery will have to supply 1000/.85=1177W.

The battery will have to supply the most current when the SOC is low and the voltage is low so we are looking at 1177W/12V= 98A.

98A is within the 100A spec but it sure is cutting it close.

Edit: Corrected SOC
The good news is that if you fully charge between usage, the battery will only get down to about ~85% SOC. This means the battery voltage will be higher and the current will probably be closer to 92A. That is still pushing it, but not quite as bad.

If you choose an inverter with higher efficiency, the numbers will get better. (A 90% efficient inverter would draw 87A-93A)

 

[Alice2021]

Most of 1000W inverter is truly provide 1000 watts continuous,but the better tell us your electrical appliance name,for example, fridge is only 200W, but its start power is more than 1000W ,because it has a comressor inside.
The battery size is based on your electrical power and working time,how long will you need it run by inverter.

 

[FilterGuy]

@Alice2021 brings up a good point.... but perhaps in a different way than she intended.

This would be used for cooking with an instant pot in a camper van.

This is a resistive load so I am not too concerned about large surge currents....but there could be a higher initial current while the heating element gets hot. My guess is it would not be bad enough to cause a problem but I would feel better if there was more head-room in the numbers.

However, does the nameplate say 1000W? If so there may be more headroom than we thought. Nameplate ratings are worst-case so if the nameplate says 1000W the actual usage would probably be lower.

Do you have the instant pot? Can you put a Kill-A-Watt on it and see the actual wattage?

 

[12VoltInstalls]

If you’re buying a good inverter (top shelf stuff) in my opinion 1000W will more likely run a 1000W dependably. If you are buying a lower-priced commodity inverter, I’d probably choose from the 1200W or 1500W models.
If your total needs are resistive like the instant pot with no fridge or electronics (tv) you can probably use a less costly modified sine wave- but a pure sign wave inverter is probably a must for anything electronic or with a motor. If you burn up a fridge or a computer monitor on a modified sine wave inverter- as I have- the few bucks you saved won’t pay for the thing you burnt up.
Some TVs I hear have “dirty AC” tolerant power supplies in them but I think for most it’s a gamble. And I don’t know how to tell the difference.

 

[Alice2021]

It's better to leave a little more power,for your 1000W requirement,I suggest a 1500W pure sine wave inverter + 200Ah battery.

 

[corn18]

I was about the purchase an SOK 206 Ah battery, but was concerned by the 100A maximum discharge. I want to be able to operate a 1000 watt AC load for 15-20 minutes at a time (with charging in between). To be safe I guess I would want to size up the inverter to a 1200 watt rated inverter…which would then need ~120 DC amps.
Questions:

- is it necessary to size up the inverter, or can a 1000 watt inverter truly provide 1000 watts continuous.

- can the SOK battery handle this load?

- if not, should I look around for a battery with a higher maximum discharge (or learn to make a DIY battery with a higher rated BMS (Current Connected has a JBD BMS rated for 150A)).

Thanks in advance for any help you can provide. This would be used for cooking with an instant pot in a camper van.

I have pulled 143A from a single SOK battery (286 from a pair). So have others. To be safe, I would stick to 1,200W. That would be about 115A continuous @ 85% efficiency.

You pick the Ah you need for your power needs.

 

[w28]

Thank you all for the super helpful replies. The nameplate on the Instant Pot says 1000 watts. To double check, I put the instant pot on a Kill-a-watt meter and made some soup. The Kill-a-watt registered 1003 watts for the initial heating period (10-15 minutes), then began cycling between 1000 and 0 watts once it reached pressure. This, plus a tea pot (1000 watt) would be my only large AC loads, so it sounds like I might be good with the SOK battery and a quality 1000 watt inverter (or 1200 watt for a little headroom).

Thanks again for such helpful replies.

 

[12VoltInstalls]

1200 watt for a little headroom

Yup. Big fan of headroom- a 1000W inverter I don’t think would enjoy your instant pot