24v mpp all in one completely dead

Hi, I've had a mpp 24v for about 2 months and it's worked flawlessly. However, it has completely died. No lights, nothing at all. I've hooked it into shore power and still absolutely nothing. I tried the breaker switch on the bottom and also nothing. I have 2 24v battleborn batteries and when they are hooked to the mpp all in one they show 9.5v, but when I disconnected the negative cable from the mpp the batteries jumped to 22.5v. This is my first system and I'm at a loss. Google didn't come up with anything like this. Any tips on what to check would be greatly appreciated.

Link to the mpp I purchased: https://www.ebay.com/itm/110Vac-240...rentrq:1ea34e2016e0a4b7b74173c1fffe23e8|iid:1

22.5v is pretty low for a 24v lithium battery. I wonder if the load from the inverter's DC input capacitors is pulling the battery down to the point where the BMS goes into low voltage disconnect.

Do you have solar panels with sunlight on them connected to the MPP? Only speculation but if the AC input power supply in the unit has failed it would need at least a semi charged battery to start up and then be able to operate from solar input only.

Apart from powering off, disconnecting, then checking fuses in the unit there's not really a lot more the average (wo)man off the street can do. If you do open it be aware that the capacitors can hold a charge for a while so sticking fingers in random places is not advised.

Yes, it had solar 800w of solar hooked to it in sunlight for approximately 8 hours before I found it. I realize the BMS shut the batteries down, but they should have been fully charged with that amount of sun. Also when I left at 3 am the batteries were at 25.5v and I had about 10w of load on it, so charging aside the batteries should have still had power.

On the surface it doesn't sound good. The inverter itself would have a minimum draw, I'll guess 2 amps from the battery from what I remember of the MPP specs. Depending on the ah rating of the battery its conceivable the inverter could draw them down to flat just from its idle draw if the MPPT/charger stopped working for some reason. It's all under micro control so the scope of what has actually failed would be 'almost anything'.

I'll assume you've done the obvious, removing all power sources from the unit for an hour, then tried powering back up from the shore power alone. It might just be that the control micro has locked up or gone off the rails.

Do you have a 24v source that could be used to try to power up the inverter from the battery input, even another battery?

I know that doesn't help you much, but I think the only things you can do are checking internal fuses and connections unfortunately, and if that doesn't help to contact the seller for a warranty claim.

I have 100 ah. 2x 24v 50ah battleborns. I have it disconnected from everything for more or less an hour and nothing. I'll try it again after several hours. No 24v source unfortunately, but I'm ordering a charger to recharge the batteries. Couldn't find anything local. I sent an email for customer service, but I'd be surprised to hear back before Monday. It has a security sticker covering one of the case screws so they know of you pulled it off so I'm going to leave it intact and see how the warranty plays out. Thanks for the help, I'll update when something changes. Fortunately I'm in the desert so busting out the generator is a viable option.

I have a 24v MPP, it will not start if it does not detect 24 volts from the battery. I have had to use a separate charger to bring up the voltage 2-small lead acids I used for awhile to get it to start. I am betting charging your batteries to 25v+ will get it going again. Another idea is to use your volt meter to see what the voltage is at the MPP terminals. If its lower than the battery voltage then make new cables or check the connections and terminals, one might be coming loose.

I wondered about that, if its start up initially requires voltage from the battery. I drained it all the way down once to see what happened and it recharged itself perfectly, however, I didn't have my 12v hooked to the batteries yet so that may have polished off the last bit of power and the battleborns signed out at a lower voltage than the mpp would except. I have a 24v charger arriving tomorrow. Unfortunately I couldn't find one local. The cables are all good.

This is an easy one to fix, your low battery cutoff voltage is set way too low, as well as the low voltage cutoff to switch over to utility.
Whats happening is that your battery is draining before the safety limits can kick in. Yeah I know this sounds weird, but if you dont have a battery charger (24V, connect your solar panels directly to your battery until they are at 24V (bush chargin - LOL), but dont let it go any higher, otherwise those batteries will be poofed!!! It would take a few hours.
Best Ian

I can understand it not starting if battery power isn't available and it's running off-grid. It's not the only unit that won't start from solar alone.

Not starting from grid power if the battery is flat is the perplexing part. Sure, don't try to charge if battery voltage is set to autosense and maybe show an alarm, but to not even turn on? That's not good design at all.

So it's back working again. I think what happened is the mpp cut off at its shut down voltage, and my 12v loads I had hooked to the battery drained it further till the BMS in the batteries shut down. I bought a battery charger, but when I hooked the mpp back to the batteries before putting charger on it turned on. Hooked up the solar and it's all good. In the future I am not going to run 12v loads off of the batteries, but instead use the lead acid battery that's already mounted and use a transfer switch so that all loads from the battery go thru the mpp. I had expected 120v in to be able to start it and charge the batteries, but I guess it requires some power form batteries to even turn on.

gnubie said:

I can understand it not starting if battery power isn't available and it's running off-grid. It's not the only unit that won't start from solar alone.

Not starting from grid power if the battery is flat is the perplexing part. Sure, don't try to charge if battery voltage is set to autosense and maybe show an alarm, but to not even turn on? That's not good design at all.

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Its not perplexing at all, the internal circuitry and CPU needs a specific voltage (and current) before charging can occur.
Battery Open circuit voltage does not count, for example your TV remote batteries when they die, you can pull them out and still read 1.5V per cell, but put any load on them and they drop like a rock), same goes for your big 24V battery, it may show a voltage but its completely drained - and cant to do any work.

Batteries need to be above the ( Cold Start Voltage 23.0Vdc ) page 25 in the manual before it can operate.
This opens up the whole question of Low DC voltage cutoff.
Lead Acid batteries can recover some voltage when left alone (hence allowing the battery voltages to drop under load before turning off the inverter (page 25), other battery chemistries don't do that so well (voltage recovery), so that's why its important to set your lower limits well above the the voltage where the battery become exhausted

Put some charge into those batteries like I mentioned above, if you are desperate, and don't have a charger, otherwise you will need to use a commercial charger to bring them up to have any life in them before the Inverter Charger can take over

All the best
Ian

My comments were specifically about it not turning on at all. Not being able to turn on at all except in the presence of a battery with at least a partial charge is, IMO, bad design for something that actually takes mains in.

It would be nice if the 120v in started it up and the battery charger. Oh well, now that I'm aware of it I don't think it will be a big deal. If everything goes thru the mpp and no additional drains from the battery I don't think this will happen. I had drained it all the way over night once to see what happened and when I got back from work everything was great and my batteries were fully charged so I think the 12v load coming off the battery is what did it in.

gnubie said:

My comments were specifically about it not turning on at all. Not being able to turn on at all except in the presence of a battery with at least a partial charge is, IMO, bad design for something that actually takes mains in.

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True, but some car battery chargers are designed the same way, they need some sense of what the battery voltage of the battery is before it starts charging it.

For example, If I connect a 12V battery to a 24V charger and bump it with 40A, this is a recipe for a disaster, it will cook that 12V battery to a crisp. Another example of a 24V battery has a dead cell, it would not be able to reach 23V to let the charger know that the battery is not compromised in some way.
If you put a battery on charge with a dead cell, it will heat up and boil to a seething mess, as it can never reach a voltage to turn off the charger

There is a method to the madness

But I hear you and agree, it should at least start up and show a fault code, which references that the battery voltage is too low to start charging

Archimbald said:

It would be nice if the 120v in started it up and the battery charger. Oh well, now that I'm aware of it I don't think it will be a big deal. If everything goes thru the mpp and no additional drains from the battery I don't think this will happen. I had drained it all the way over night once to see what happened and when I got back from work everything was great and my batteries were fully charged so I think the 12v load coming off the battery is what did it in.

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Please set your low cutoff voltage higher to 12V , its better to start higher at a higher setting (setting 19 on the menu, it is defaulted to 10.2 which is too low)

You guys beat me to it! Nice Thanks Ian

What happens if you have set it to 24 volts minimum cutoff on Mpp on a 24v system and it still dies? I paid to send my bigbattery back and they replaced it. My unit will not protect itself with 2 different batteries. I am just running a security system at first but it will not make it through the week. I know I am underpaneled but I want to be able to charge battery off generator when it gets to this state and not damage battery. My battery never makes it below 24.8 volts without turning off. I am then dead and sometimes I have to unplug battery wait a week and the voltage happens to be enough to hook up generator to mpp to start charging battery. I bought a small 24 v charger and it will not work on this battery at all. I think it's the battery but I am not paying 180.00 again to send it back. Thoughts?