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Shane B avatar image

Quattro reading batteries as full, when they are not.

I have a Quattro 48/10000/140 hooked up to two BYD 24v 200ah batteries connected in series, with two blusolar 70 amp mppts and a 5kw array, all connected with a Venus. We are totally offgrid, so fully dependent on our setup. It has been working fine for the past two months since setting it up, but now that we have added some larger draw appliances it has been acting strangely.


The main issue is the Quattro reading the batteries as fully charged, when they are not even close. As a result, it is only float or absorption charging when it should be bulk. Every time I have run my generator (5Kva), no matter what level the batteries are at, it immediately give a false 95% full reading. Even during the day, the mppts will charge the batteries up to about 53v, then they start reading the batteries as full and reading 55.5 float. In both instances, when I use the multimeter to check the actual state of the batteries, they read 53v, not the 55v the charger and quattros are reading.


For example: Yesterday the mppts said the batteries were full at 10 am and started float charging at 55.5v. when I checked the actual voltage of the batter it was about 53.2v. over the course of the day the actual reading slowly climbed to about 53.7v. During the time of day when I know the panels are able to produce over 5kw, they are only producing enough to run the house and float. When the sun goes down, I check the batteries and they are at 52v after just a short time with a medium load. As a result, the batteries don't make it through the night with even a small load of fans, etc. (its 45-50C during day, and 30-35C at night here, so sleeping without a fan is difficult). So the batteries died at 04:30, The Venus read 47.3V (but was claiming to be 43% full), and actual battery reading was 48.1v (Venus was with 800w load, battery was with no load after power to house had cut off). So I started the generator to run the house and charge the batteries. But as soon as I connected it the venus went to 95% and started float charging at 55.5v at about 50w. The actual battery reading was at 48.4v. So I ran it until there was just enough sun to at least run a fan (about 1.5 hours) and when I shut it off the batteries were reading 48.8v.


The first few times I ran the generator, it would run the house and air conditioners on full blast (about 2,200w) and charge at about 1500w. but now it seems it won't charge the batteries because they immediately think they are full. Its really frustrating to have to continually worry about the power running out at night, getting up and starting/stoping the generator. Especially if I have to run it just to power a fan. Please, any help would be greatly appreciated. Thank you.

battery chargingGeneratorbattery system voltage
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JohnC avatar image
JohnC answered ·
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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Can you give us some more information about your system and the batteries? I only know the 48V batteries of BYD and can't find info's about 24V 200Ah models.

Do the batteries have a internal battery monitor (connected to the Venus) or do you have an external battery monitor?

Do you have any DC load?

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