Possible power drain

[Melbournewoodfinishing]

Hi, newbie here and wondering if anyone can suggest anything

My current setup in my Renault trafic camper

4x 100w renogy solar panels in parallel but done in 2 separate inputs to the 30A Renogy Rover MPPT controller and then 5x130Ah leisure batteries so a 12v setup, all is brand new and I've never let the charge drop below 50%. It also has a split charge relay from the alternator to charge while I drive

I have 3 led lights that run from the controller at 12v and a 1500w pure sine wave inverter wired directly to the battery bank

The inverter literally runs a 40l 240v fridge which at peak shows 200w when on full blast but I have it on a low setting so 45w when it's on

After a full charge and 100% reading, if I leave the fridge on overnight by 8am the charge is reading around 70%.... Understandable I guess?

My worry is that with everything powered off, fridge & inverter so absolutely no load at all overnight, my morning reading is still between 75&80%

Is this normal with temperature change or do I have a power drain somewhere?

The only change I haven't tried yet is to disconnect the relay but the van battery is brand new as well

Any advice much appreciated guys, & thanks

James

 

[Melbournewoodfinishing]

Oh they're all lead acid batteries

 

[Mattb4]

How do you obtain charge reading percent? If it is a simple battery voltage reading converted to SOC it likely is not very accurate especially so if under charge or discharge.

 

[littleharbor2]

Once the sun sets the float voltage will sink from approx. 13.6 to approx. 12.8 volts. Your voltage based soc may be seeing this as battery drain.

 

[MichaelK]

The absolute best way to determine the true charge of a lead-acid battery is with a battery hydrometer, with the best accuracy from a temperature-correcting model. I have a Denka. Something like this. It's a bit more tedious, but gives you very accurate numbers.

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[Melbournewoodfinishing]

Hello all and thanks for your help

In answer to the questions and after a bit of reading up.... I'm taking the readings directly from the Renogy rover controller so in full sun with around 20v coming from the panels the readings are 100% charge and up to 13.4v giving around 10A (if I put a voltmeter across the terminals it's more like 20A) but guessing this is the controller doing it's job

Out of the sun it quickly drops to about 1-2A input and hovers around 13v 98% charge almost the same as an hour after I have turned the engine off

Also overnight I put no load on, no fridge or inverter and I left the van in the shade so no morning sun, the readings were 84% charge and 12.8v which is what I'm guessing Littleharbor2 suggested with the float

The night before, with the fridge and inverter on from sunset to sunrise then switching everything off to normalise for an hour the readings were 75% charge and 12.6v - I suppose all I'm really asking is this an acceptable level for the setup I've got, 1500w inverter with a fridge that will peak at 200w then hang around on and off at 50w for 12 hrs before being replenished either by the sun or driving to work & just don't want a schoolboy error on my hands

After reading up about Mppt readings from the controller, yeah they drop to around 60% when there's 40w of led lights and the fridge running and the batteries are discharging but soon go right back up when I switch the load off entirely

Just if anything sounds abnormal here other than my slow learning I would be grateful of the knowledge

Thanks to you all

James

 

[MichaelK]

You are not making your reading properly. Looking at the controller in the daytime means you are reading the charging voltage, NOT the battery voltage. The only way to use voltage to look at a lead-acid's state of charge is after sunset, with a resting battery under NO load. That means the battery voltage is only approximately accurate when disconnected from anything drawing current. Same with the hydrometer. Take you readings at sunset.

Getting back to your original post, you have five 130Ah batteries in parallel? That is a lot. You don't have enough panels to support that size battery bank. Assuming you want to charge your batteries at 1/8th of C, with C being 130Ah the math is.....

[ (130Ah X 5 batteries)/8 ] X 12.5V charging = 1015W of solar. Are the panels laying flat on the roof of the trailer? Is so, derate output down to at least 75%, so the solar needed is more like 1015W/0.75 = 1353W of panels. More than 4X what you've got on it right now.

1350W would be at least 5 large residential grid-tie panels in the 250-300W range. I'll assume you can't fit that many. Look at your roof space and decide how to squeeze as many watts as you can up there.

In the mean time, I'd suggest getting your bank onto an AC-charger coming from the house. Five batteries in parallel is too many for proper charging. Isolate each battery and check each charge level independently of the others. If any of the five show a weaker state of charge, immediately get that battery fully charged separately from the rest. Link all the batteries back into parallel after all of them have been brought to the same level of charge.

 

[Melbournewoodfinishing]

Oh right, yes that's really interesting. In my head, having a large bank of batteries did make me think that as I currently drive at least 1 hour a day, mostly 2 with 14.4v coming from the alternator and the 4 renogy panels that are supposedly 18v output (but more like 20v in full sun) then I would at least store as much as I could and hope for at least 3 days off grid. If it were a home setup yes I get you, I just thought with all the additional power coming from the alternator then why not store it if I can and on bad weather days I wouldn't necessarily have to unhook the drive away awning and go for a spin or rely on electric hookup?

Oh, Yes they're all mounted flat on the roof and with regards to the split charge relay it can cope up to 140A but I'm pretty sure I've got a 40A limiter on it

 

[littleharbor2]

You haven't mentioned the specs of your panels but there's this to consider.
STC (rated) voltage something like 22.5 voc, 18 vmp.
Real world (hot panels) voltage something like 20 voc. 16.5 vmp.
Actual output voltage from CC when connected to a 12 volt battery, slightly higher than the actual batteries voltage. Voltage rises as the battery gets fuller.
These things need to be kept in mind when monitoring the solar panels voltage.
Of course this pertains to 12 volt solar panels through a pwm controller