Tab 320 S - AC on lithium battery

Citation · May 9

Hello all,

The previous owner of our new-to-us 2021 Tab 320S installed two 100Ah batteries and a 2000W inverter. With this set up, microwave did not run at all, but if I recall correctly, the AC ran with compressor - sorry we only had it for a month. The batteries also were not holding much charge now, so we decided to upgrade to WattCycle 314Ah Mini Super (200A BMS) lithium and replace the inverter with Renogy 2000W (4000W surge).

I mistakenly assumed that this setup would be capable of running both the Microwave and the Air8 air conditioner - not at the same time, of course.

Microwave runs fine now, but although the Air8 fans start, as soon as the compressor kicks on, the inverter goes into a fault mode. The battery is in the front storage box, via 1/0 cable, and the inverter is under the driver-side cushion. (about 8-10’?) Suspecting voltage loss being the cause, I brought the battery inside and connected via 3’ 1/0 cable, but still no go.

For those of you with lithium system capable of running AC, could you please share your set up? Inverter you are using, etc.? Once I find the working setup, I also plan on bringing the battery inside to reduce the length of the battery cable a bit.

Thanks!

Citation · May 9

Thanks otr_320. Yes, I have the high-frequency version. I see another 2000W inverter that is significantly larger/costly that seems to weigh 50lb. Considering the limited space, it seems the best option is to get the Easy Start. Thank you for your insight.

Citation · May 9

Also, if I understand correctly, and assuming the general design is the same, the switching to 3000W high-frequency version will not be able to handle Air8 due to short surge time. Thanks.

AnOldUR · May 10

@Citation
We have a 2000W Renogy inverter in our 320S. It has no problem running the Air8 air conditioner. My guess is that your air conditioner is not plunged into an outlet powered by the inverter.

Citation · May 11

@AnOldUR Thanks. That's interesting. Do you have multiple batteries in parallel? Are the batteries in the front storage box or did you move it to the cabin with shorter cable length?

Mine is plugged in. It powers on, fan runs, and as soon s the compressor starts, the inverter goes into fault mode.

ckjs · May 11

We have 2x100Ah Lithium batteries connected to a Samlex 2000 watt inverter with 5’ of 2/0 battery cables. The stiff cables are a pain to deal with. (I’d expect that 3’ of 1/0 cables would be ok.) The Danby AC runs fine.
Can you measure the voltage at the inverter terminals when the fault indicator goes off?

RTWCTS · May 11

@Citation since the peak demand of the AC compressor is greater than the capacity of your inverter, maybe you should look at a soft start unit. It contains a capacitor (sometimes called a condenser) that 'stores extra electrons' to give the compressor the boost it needs without overtaxing the source electricity. It is a common part on home heat pumps and AC units. My table saw even uses a capacitor for motor startup.

etrailer is one source for soft start units (link below):

SoftStartRV Soft Start for Single Zone Air Conditioner Setup - Qty 1 SoftStartRV RV AC Soft Start SSR54FR

Citation · May 11

@ckjs Thanks, I will measure the voltage and see if I can also measure inrush current, and report back. I really don’t want to invest in a soft start module if some of you have it running in your current setup with 2000W inverter.

@RTWCTS Thanks. I agree.. I have a feeling it comes down to either ’soft start’ module which gradually ramps up current or the ‘hard start’ module, which supplements and providing the extra current during the start, which I think you are referring to.

RTWCTS · May 11

Sorry for grouping the hard and soft start systems together @Citation… you are right, of course.

Citation · May 11

@RTWCTS Oh, I didn’t mean to come across like that. I have been reading the forum and learning as much as I can. Just learned the two different approaches. Thank you for taking time to share your insight.

AnOldUR · May 11

https://tab-rv.vanillacommunity.com/discussion/comment/221341#Comment_221341

Our two 100Ah LiFePO4’s in the front storage box wired in parallel had no problems starting the Air8. I don’t remember the gauge wire that I ran, but it was about eight feet of wire to get to the driver side wheel well. The brand of inverter may be the difference between yours not handling the initial surge. Ours is a 2000W Renogy. The number of amp hours that you have will not change the ability to run the Air8. It will only affect the time it will run before draining the battery.

For what it’s worth, I slightly undersized the wire for easier installation, but fused it at 125 amps knowing that I will not draw more than that even though the inverter has the potential to.

Citation · May 11

@AnOldUR I meant 200A BMS Discharge rate. The capacity of my single battery is 314Ah. Depending on the maximum discharge rate of BMS, it can make a difference. Installing two in parallel will not necessarily solve that problem though. Max discharge rate will still be the same, unless I am missing something.

AnOldUR · May 11

True @Citation. Although I don’t know the surge amperage of the Air8, the running is somewhere around 70 amps at 12V. Our two 100Ah LiFePO4’s each had a 100 amp maximum draw limit, so 200 amps combined. I’d bet that a single one could handle the surge, but I could be wrong.

Tab 320 S - AC on lithium battery

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