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Discussion Starter #1
I have a MPPT with 100W flex panel. Linked to a 100Amp battery. I was testing the battery today with the fridge so turned it on and cranked it to 6. I was getting 38-80w from the panel when I was checking it today but the Voltage was still 12.7v .

I have come home turned the fridge down to 3 which was at 6pm. Checked again now 11pm and the battery has gone from 12.7 to 11.9v.

Is that right ? should I try and charge the battery from mains? is there a way to test the battery or do I need a new one? battery is only 12 months old but it has been under 11.9v a few times in that time.

I need it for Friday as camping 3 days off grid. have I screwed the battery up?

Thanks
 

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It's hard to be certain because there are lots of variables (for example the "resting voltage" of the battery will be different by maybe half a volt depending on whether it has just been on charge or has been "resting" for an hour or more).

But assuming your fridge is a compressor fridge (not a 3-way fridge running on 12V) then it does sound like the battery is past its best. Mine would typically run my compressor fridge for 2 days before it needed a recharge, in the days before I added the solar panel.

Taking the battery to 11.9V occasionally should not cause it major damage - the real problem seems to come when it's taken to a low state of charge and left in that state for more than a few hours.
 

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Discussion Starter #3
hi Triffic - Thanks - Yes before I had the panel then it would of been lower than 11.9v on more than one occasion. Its probably safer to purchase new then but I will try to recondition the battery tonight to see if it does anything.

Does anyone have any recommendations on a 110amp battery. for under the seat. I see the ones that are 354mm long would they still fit?
 

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I've got a banner bull 110AH from Alpha batteries under the drivers seat and seems decent. Had it for 18 months and going strong with regular maintenance/use.
 

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Discussion Starter #8
no swivel - I think I have a higher one that 190 at the moment . looks as though mine is not holding charge so going to go with the 110amp/hr
 

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I have been to an auto electrician with a 115Ah battery and a dual battery tray to have them installed beside the main battery on my 1998 T4. The electrician says there is no room and that the ECU? is blocking the fitting as there is restricted space. Any ideas?
Dennis
 

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If you are expecting the solar panel alone to charge the battery enough to run a 12v fridge it's not going to happen , a fridge is a big drain on a battery ant the panel will not charge it quick enough to keep up , if you leave the fridge switched on it will kill the battery
 

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If you are expecting the solar panel alone to charge the battery enough to run a 12v fridge it's not going to happen , a fridge is a big drain on a battery ant the panel will not charge it quick enough to keep up , if you leave the fridge switched on it will kill the battery
Depends on timescales involved, as well as the Fridge itself.
My setup is a bit different as I have 200W of panels rather then 100W, but I can leave my fridge on 24/7 without any hookup and it will work for months on end - I only switch it off when I know I have no intention of using it for the forseeable future.

If you have a modern Compressor fridge, it will last around 30 hours or so on a 110Ah battery before it drains it to 50% (max advised).
Add in a 100W solar panel into the mix and on decent day (Mid May to Mid Sept) you could reckon on putting in around 250Wh into the battery (so about 20Ah). A 100W Panel will not support a fridge on its own, but it will be good enough for a long weekend.

(you do really need 200W of Solar to be fully self-sufficient with a fridge though to provide enough charge to run in daytime whilst recharging battery, and with a 100Ah battery for enough juice to run fridge between dusk and dawn)
 

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If you are expecting the solar panel alone to charge the battery enough to run a 12v fridge it's not going to happen , a fridge is a big drain on a battery ant the panel will not charge it quick enough to keep up , if you leave the fridge switched on it will kill the battery
As Hoovie says, it's not as clear-cut as that. I have a Waeco CR50 and a 100W solar panel and I've just spent 7 days on Mull and Skye with no electric hookup, and the leisure battery never went below 12.2V.

In fairness I typically drove the van a few miles every other day, which obviously means a top-up via split charge, but even with no alternator input I would probably get at least 4-5 days without EHU unless the weather is very overcast.
 

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Discussion Starter #13
I bit the bullet and got a new 110amp battery. I was hoping to be self sufficient with a 100w flex panel with the compressor fridge. Would a 2nd panel fit on a Victon 75/15 mppt? or would I need to change the MPPT aswell?
 

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I was talking on a 100w level obviously if your solar panel supply is bigger than yes you could get away with it , I would rather have a 12v fridge but I would have to practically cover my roof with solar panels , in the future I want a lot bigger van , VW LT maybe,then it might be possible for me to do , I don't spend enough time living in my van to justify spending a lot of money on solar at the moment.
 

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Discussion Starter #15
So battery this morning after running the fridge on lvl3 last night was down to 11.5v this morning. So I think that is dead. New battery testified and on charge before weekend festival. Just need to sort out wiring for the stereo to leisure battery and I am done. This will be the test. Except how much are you guys setting from your panel today. Mine is reading with clear sky 55w which seems low but I am on mains hook up if that makes a difference?
 

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So battery this morning after running the fridge on lvl3 last night was down to 11.5v this morning. So I think that is dead. New battery testified and on charge before weekend festival. Just need to sort out wiring for the stereo to leisure battery and I am done. This will be the test. Except how much are you guys setting from your panel today. Mine is reading with clear sky 55w which seems low but I am on mains hook up if that makes a difference?
Right now, my 200W Array is showing 175W coming in which is 85% so happy enough with that. Your 55% on a clear day around this time would seem low, but if your battery is charged and you are getting power from mains via an on-board charger then I would think it would be lower (can't fill something when it's full already :) )
Maybe turn off the charger, get some load on the battery and see what the power from the panels goes up to?

Ref power from leisure battery - you need to splice the two yellows together coming from the GPS and the Radio and crimp on the male blue bulle. Similarly with the red wires, but Male bullet on the radio side, female bullet on the VW wiring side of the dandy loom.
I'm about to head away to Volksfling and won't be on-line or similar for a while (sometimes can't get any data connection at all there :( )
 

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My system is 200w of rigid solar panels on the roof, no split charge hookup or anything else to complicate the install. Panels connected to 2x 135amp batteries via mppt controller and a crx50 fridge direct from battery which is permamently on, together with lots of the usual USB connectors dotted about.

Realise i've got fairly big storage and PV but its certainly possible to go 'off grid' with this type of install, lowest my battery monitor has dropped to is 12.8 over the last year or so.

Hope that helps
 

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FWIW Ii only have a 100W panel and can now stay on-site indefinitely with careful use of lights and (compresor) fridge temperature settings. in the summer at least which, as it happens, tends to be when the fridge is needed the most. T: I'm not using a MMPT reg, just a regular (series) PWM, but a reasonably decent one, i.e. not from fleabay. check the specs, but to realise maximum advantage of your Victron MPPT with 2 panels I would suggest wiring them in series, not parallel, unless your install means one is likely to be more shaded than the other (unlikely if e.g. both mounted on roof and adjacent to each other)
 

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My leisure battery (110Ah) will run my Dometic fridge for around 1 day before the battery is down to around 12.0v and then the fridge will start to struggle to drive the compressor.

Whats a good way to test the capability of the battery, as it happily charges vai the Solar panel or split charger and will sit at 12.7v, but its around 3yrs old so could be on its way out?
 

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one can buy battery analysers that will give you a number, CTEK do one for example, but theyre not cheap, might as well put the money towards a new battery. if you whip the battery out and take it to a battery centre then they can prob test it for you e.g. via a drop test.
otherwise do your own - just fully charge it, stick a known load on it, measure the voltage vs time and thereby plot the discharge curve. effectively you've already done this test though with the fridge, if battery used to run the fridge for longer and now doesnt, and if the load hasnt changed and the battery is still being properly charged then it can only be this ! T:
 
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