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Upgrading battery backup system for my pellet stove, unsuccessful so far with Ampere Time

bigchevy79

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I have a pellet stove that currently has my homemade battery backup system that is able to power the stove for roughly 4 hours or so if the power goes out (max draw from the stove is 300 watts). I am guessing you would call this setup a UPS... The current system has 2 6volt 200ah agm batteries connected in series and I have a 1000 watt prowatt sw Xantrex pure sinewave inverter, Xantrex prowatt sw automatic transfer switch and a Noco Genius 10 amp charger. The batteries are 10 years old and getting worn out so I decided to try upgrading to a lithium 12 volt 200ah Ampere Time. I received the battery and fully charged it and then connected the inverter and charger both up to the positive and negative terminals of the battery and the prowatt sw transfer switch is plugged into the inverter and tried both powering a small house fan and also running nothing soputting no load at all on the inverter. This setup would work for a few minutes and then the inverter and battery charger both would trip and show an overvoltage alarm of about 17 volts. I ran several tests using just the inverter on the battery and using just charger on the battery and everything was fine but as soon as I connected both the inverter and charger up to battery at the same time I would get more overvoltage. I double checked the settings on the battery charger to make sure it was setup for charging lithium batteries.
I tried this setup on a few other batteries that I have and had no problems at all but unfortunately they are not lithium batteries. I contacted Ampere time and they had me do a few tests as well including connecting the charger to the back of the inverter instead of to the battery terminals. This test caused the same over voltage alarm after a few minutes. They concluded that their battery can't be used as a UPS and they sent me a shipping label and sent me a refund. Hats off to Ampere Time for trying their best to help me figure this out and quickly sending me a refund. So am I stuck using AGM batteries with this setup? Do I need an extra component for this setup to use a lithium battery?
 
NOCO has a lot of balls calling their chargers "Genius." It's mostly their marketing that's genius, not the chargers. If your charger has temperature compensation, and it's cold outside, it is unsuitable for LFP. Temperature compensation runs HIGHER voltages at lower temperatures and can easily trip BMS cut-off. It says it does. It doesn't say it turns that off for LFP. Hope it does.

The user manual indicates a 14.6V peak voltage for LFP. While that's the typical maximum recommended charge voltage, that voltage can cause a single cell in the battery to go ever so slightly above peak and trip the BMS. A BMS trip is likely going to result in momentary overvoltage.

Note that just having the inverter connected without any loads applied is a load inverter's burn juice just by being on.

IMHO, the presence of both devices permitted a condition to occur where a single cell in the battery tripped the BMS. As a result of tripping the BMS, suddenly the charger was the only source. The slight load from the inverter being on and the limited speed the NOCO could react to the battery being instantly removed from the circuit, over-voltage occured.

From the manual:

Using 12V Lithium.
12V Lithium charge mode is designed for 12-volt lithium-ion batteries only, including lithium iron phosphate.
(THIS LINE IS VERY CONCERNING AS IT'S SELF-CONTRADICTORY - THERE ARE NO NON-LFP LITHIUM-ION BATTERIES THAT WOULD WORK AT THIS VOLTAGE).

CAUTION. USE THIS MODE WITH EXTREME CARE. THIS MODE SHOULD ONLY BE USED WITH 12-VOLT LITHIUM BATTERIES THAT HAVE A BUILT-IN BATTERY MANAGEMENT SYSTEM (BMS). LITHIUM-ION BATTERIES ARE MADE AND CONSTRUCTED IN DIFFERENT WAYS AND SOME MAY OR MAY NOT CONTAIN A BATTERY MANAGEMENT SYSTEM (BMS). CONSULT THE LITHIUM BATTERY MANUFACTURER BEFORE CHARGING AND ASK FOR RECOMMENDED CHARGING RATES AND VOLTAGES. SOME LITHIUM-ION BATTERIES MAY BE UNSTABLE AND UNSUITABLE FOR CHARGING.


Does the above wording convince you that this is the best choice for your battery? Not me.

Possible solutions:

The charger has a "12V supply" mode that provides a steady 13.6V - will charge LFP to 95% full over several hours and hold it there.
Replace charger with unit that as no temperature compensation and charges to no more than 14.4V.
 
I bought an AIMS charger that has temperature compensation, and you can buy a temperature probe accessory for it (plugs into comm port provided on the charger) to mount right against the battery or cells. It also has DIP switches on it so you can set it for LiFePO4 battery.

Not saying you need to buy a different charger, but it could be an option as well.
 
I am surprised that Ampere Time didn't say anything about the charging specs of the battery charger then. I gave them all the specs for the equipment that I was using for my system. FYI this setup is indoors so cold weather shouldn't be a factor for charging. Well I no longer have this battery as it was sent back yesterday so I need to start over. I don't know if I want to order another Ampere Time battery since they told me their battery isn't compatible with my UPS system. So now apparently I need to find a different charger and a new battery. I emailed Bigbattery and have decided to steer clear of them as they stated they are not familiar with this setup that I have.
 
I am surprised that Ampere Time didn't say anything about the charging specs of the battery charger then. I gave them all the specs for the equipment that I was using for my system. FYI this setup is indoors so cold weather shouldn't be a factor for charging. Well I no longer have this battery as it was sent back yesterday so I need to start over. I don't know if I want to order another Ampere Time battery since they told me their battery isn't compatible with my UPS system.

Unfortunately, I suspect they didn't understand the system and couldn't provide a solution, especially if you used the term "UPS".

So now apparently I need to find a different charger and a new battery.

Definitely on the charger (unless you use it in 13.6V mode). Probably not on the battery.

I emailed Bigbattery and have decided to steer clear of them as they stated they are not familiar with this setup that I have.

The stated reason is not the reason to avoid them, but avoiding them is often the best solution.

Please confirm if I understand your intention correctly:

"I want to power a 12V input/120V output inverter supplying X loads with a 12V battery. I want to charge the battery with a separate AC-DC charger."

Is that correct?

If so, any suitably sized 12V LFP powering the inverter and connected to your charger in 13.6V mode should work fine.
 
inverter and battery charger both would trip and show an overvoltage alarm of about 17 volts
something is not right here.

the Amperetime BMS shuts of at 15V - so you inverter and charger shouldn't get to 17V

What could have happened is - you overcharged the battery - the BMS tripped into safety - and the voltage of your charger - with no load was shooting up.

What kind of voltage are you measuring at the battery terminals?

Have you tried Only connecting the inverter?
 
One issue you could face using a single lfp battery is the 50 to 100A max draw... and the low charging specs many bms have.
I'd recommend at least two batteries.
At only 400W 120V output you are pulling 40A average... add in the inverter drain, and could be over 50A.
 
Unfortunately, I suspect they didn't understand the system and couldn't provide a solution, especially if you used the term "UPS".



Definitely on the charger (unless you use it in 13.6V mode). Probably not on the battery.



The stated reason is not the reason to avoid them, but avoiding them is often the best solution.

Please confirm if I understand your intention correctly:

"I want to power a 12V input/120V output inverter supplying X loads with a 12V battery. I want to charge the battery with a separate AC-DC charger."

Is that correct?

If so, any suitably sized 12V LFP powering the inverter and connected to your charger in 13.6V mode should work fine.
I sent them numerous videos of my setup and videos of the problems I was having.
"I want to power a 12V input/120V output inverter supplying X loads with a 12V battery. I want to charge the battery with a separate AC-DC charger."

Is that correct? Yes it is
 
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something is not right here.

the Amperetime BMS shuts of at 15V - so you inverter and charger shouldn't get to 17V

What could have happened is - you overcharged the battery - the BMS tripped into safety - and the voltage of your charger - with no load was shooting up.

What kind of voltage are you measuring at the battery terminals?

Have you tried Only connecting the inverter?
When the charger was done fully charging the battery the voltage measured 13.5 volts at the terminals and yes I tried just the inverter connected to the battery and it was fine, also just the charger connected to the battery was fine too.
 
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Very discouraging , makes me think I'll stick with AGM batteries. Single 12 volt 200ah AGM battery at 125 LBS, I was trying to avoid that.
 
I sent them numerous videos of my setup and videos of the problems I was having.
"I want to power a 12V input/120V output inverter supplying X loads with a 12V battery. I want to charge the battery with a separate AC-DC charger."

Is that correct? Yes it is

Weird, I can't see the answer in your post.

Anyway, this is a trivial system, and either I'm missing something, or they are. Something is faulty. I suspect the Ampertime battery had marginal balance allowing one cell to drift higher during charge+load, and a charger that pushes 14.6V instead of something 14.4V or lower formed a perfect storm. BMS tripped and instant over-volt.

I'm convinced had you just slow charged to 13.6V, you'd never have had a problem.

When the charger was done fully charging the battery the voltage measured 13.5 volts at the terminals.

That's to be expected at float.
 
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One issue you could face using a single lfp battery is the 50 to 100A max draw... and the low charging specs many bms have.
I'd recommend at least two batteries.
At only 400W 120V output you are pulling 40A average... add in the inverter drain, and could be over 50A.
I just got off the phone with Battle Born batteries and they said that just having one battery for my setup should not be the problem.
 
Yes it did without any problems.

Thought so, just wanted to make sure.

Did you at any time allow the inverter to power the load for a significant period of time (~30+ minutes, drawing the battery down) and then attach the charger? If my prior theory is correct, you would have a significant run time before the overvoltage.

Did you attempt to power more loads than the charger could handle, i.e., >120W?

Something that just popped into my head as a possibility... I don't think it's the case, but I'm not that smart.

AC is powering the inverter.
Same AC is powering the charger that's charging the battery for the inverter.

There may be some interaction. I don't think so, but now I'm reaching since my brain has been left unsupervised.
 
I didn't run the inverter under any load for more than 10 minutes. After getting numerous high voltage alarms with the everything connected including the charger I was being very cautious and didn't want to risk frying something and voiding a warranty. Now I need to decide if I want to try a lithium battery again. Unfortunately the only options I see are battle born and dakota lithium both of which are double my budget if I want a 200ah
 
Given OP test results from first post, it seems to me that an interaction between inverter and charger is the culprit, or really, just the inverter. The LFP was just smart enough to say "there's a problem in the other components, and I'm shutting down". The old agm batteries weren't smart enough to indicate a problem elsewhere in the system.

If you want to get to the bottom of this, you'll probably have to involve the inverter engineers, possibly at same time as Noco engineers (not just frontline helpdesk folks). Lot's of tests and back and forth ...

I have a similar setup, w/ inverter, noco charger, and two sok lfp's, and have not experienced this issue. I don't run both inverter and charger at the same time, so only one or the other is on. Never a problem.

My guess is that the ampere time battery was fine, but the inverter is doing something wierd which will take testing to sort out. W/o testing, you could possibly id the culprit device by trying a different inverter, or charger ...

A possible workaround, hinted at in OP, is to put disconnects between the devices, so this particular inverter and charger combo can't have the interaction at all ... you just have to flip disconnects.

Hope this helps ...
 
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