thx

That is a good point. I run it at 20% load or less. Overheating could be a problem at higher loads.

Meh install a small pc fan in there and dont run it over capacity and you’ll be more than fine. The world isn’t.

Burningdown a house. No only if the thing gets shorted. they will thermally run away on you yes but it will blow the internal fuses first or just blow a fet out. Have had it happen.

I am doing a LFP upgrade on a pure sine model. I thought about using a shottky (cheap but voltage sag) or ideal diode (expensive for 20-30amps) and this will still backfeed the internal charger like you said but why would that matter? The best option would be to disable the internal charger, I cannot find any videos on this. The low voltage cuttoff is another issue but I think the only problem here is that you will not get any warning before the UPS shuts off when on batteries and it may shut off way before the batteries are drained. I used to use a deep cycle marine battery but it did not last long. I checked it after 3 yrs and it was down to 10.7 volts, dead. Probably because the charger in the UPS isnt designed to desulfate such a large battery.

Update: it turns out that some UPS chargers work on timers based on expected battery size. This may be why my lead acid battery was damaged from improper charging by my Cyperpower 1500 PFC pure sine UPS.

At that point, I might consider just getting a power inverter, large deep cycle battery, and charger instead of a dedicated UPS.

Use 10 or 12 gauge depending on how much amps you plan on drawing.

I have not had to replace the batteries. It has been working fine. handled the recent power outage without any issues. I have not specifically tested the capacity with a meter.

It seems to charge the batteries fully. I haven’t drained them completely though.

They constantly put out 13.8 volts even when fully charged and are limited to 700 mhA. This is the reason why the factory battery's only last for about a year. It slowly cooks them into submission. it will constantly float the charge and there is no cut off time. There is no cut off or time limit to it. They are designed to "have it ready at all times"

@@CotyRiddle Could incorporating a BMS module help keep from cooking off the batteries over time?

@@dustinmeier9753 The BMS would have to cut off the input voltage without making the controller think the battery has failed. This is why you can't use LiFePo batteries in these, as nice as one of those would be for this situation...

Yes, still working fine. I have had only short power outages of about a half hour to an hour or so far. I believe it will work for 8 to 10 hours.

I haven't run them down completely, I would estimate at least 4x the run time if not more. It depends somewhat on the load.

This is a 50 amp connector amzn.to/3fe0OSq you can find other amperage ratings on amazon also

@@AlanSNasar Thank you so much Alan

I am using 35ah batteries instead of original 9ah batteries. You are correct about the fuse, it will limit to about 400w. This is for safety. This should be run at 20% load for safety and will last for multiple hours. I use it for router, modem & switches and it has worked well for years.