<span class="highlight">Solar</span> via bcdc redarc

Thanks John, sorry for the lack of detail, was thinking that the redarc would boost the solar input.. Maybe doesn't work like that?
I'd love to put more ah storage in the prado, air con pipe limits the space, and very risky to move it.. Was thinking maybe just have a spot in the rear, for a sealed battery, which is portable, and can run a lead inside from the Anderson plug, so can make more use on the redarc while driving.. Would that get me out of trouble for a few days, do you think? Thanks again.. Cheers Owen

Just dug the cpap converter out.. 12-13.8 volts input 3.1A ... 12 volt, 2.5A output.. If that helps.. Cheers

Hi Owen,

Unfortunately, one of the facts of life is that energy cannot be created - the redarc can change it to a more suitable form, but not increase (boost) it. When operating as an MPPT controller it accepts energy from the solar panel at about 17 volts and converts that to about 13 -14.5 volts to suit the battery's state of charge.

Your numbers for the cpap power supply are very useful. Like the redarc it is simply changing the voltage, in this case to suit both battery and cpap. There will be a bit of a margin built into it, so the actual cpap usage is probably about 25 watts, or about 2 amps at 12 volts. It will require about 16 Ah to run the cpap for 8 hours, which is a bit better than I'd guessed.

I'd stay with the 25 Ah per day figure for the fridge, making a total of about 40 Ah per day, which is about as far down as I'd want to run a 65 Ah battery. I think you'd be wise to add some capacity, maybe in the back of the vehicle, well bolted down and fed with heavy cables from the bcdc. Ideally, I'd move the bcdc so it's adjacent to the bigger battery.

Extra charging options - one often overlooked is that with the big bcdc charger and not a lot of fuel you can put quite a few Ah into your battery. I carry two 100Ah batteries and 150 watts of solar panels which I think would probably be about right for you. Fact is though that a few litres of fuel to cover the rare occasions and I'd need less solar!

Cheers

John

Yes Ross, mine will, but if I have a regulator already on the panel/ blanket I can use it on the camp trailer as well, when/if needed.. So if I go down this path, won't worry about doing it through the bcdc redarc.. Thanks Owen

Be wary of the battery they list that fits that battery pack as it is probably not suitable for inside the vehicle a agm or gel battery is better suited a sealed battery can still vent fumes in the confined space of a vehicle This box should be better should be able to take a 100ah agm battery http://m.supercheapauto.com.au/Product/Calibre-Battery-Box-Large-Powered/12358 I had one in the back of my pajero for many years just buy a lead with rings to anderson plug and away you go
Cheers steve

One thing though, you are not going to be sitting at camp, with the solar plugged in... And the car running eh...

Thanks Blue
I don't think it's a real issue, having the bcdc under the bonnet, mine seems to charge up the batteries (150ah)in the camp trailer quite well, when on the road, despite being about six metres from the unit..
I'm going to go and pick up one of the battery boxes today, think they are on special at present, to go in the rear of the vehicle. Might keep an eye on the solar blankets, see if they come down in price a bit.. If I have the extra battery in the back, I should be right for power, for this up coming trip any way. Sounds like you have your power needs sorted quite well Blue. The cpap machines are a pain, something else to pack and unpack each day when traveling, unless you have a van, or facilities to leave it set up, when on the road. Bit harder when camping, but, do feel better for it I guess... Cheers Odog

There are some misconceptions here.

It's never been suggested by knowledgeable people or manufacturers that "standard" AGMs are flat at 60%-70%. It is well recognised that if you take 70% out, you still have another 30% to go before the battery is flat.

I think what you're confused by is the conventional wisdom, well founded, that the less you discharge ANY lead-acid battery in each cycle, the longer it will last.
Keep it at 100% it will last maybe decades.

Discharge it to 0% SOC every cycle and it may last only months.
The conventional wisdom is that the sweet spot between practical useage and getting the maximum cycle life out of AGM batteries is to discharge them only about 50% before re-charging. At 50% they are NOT flat.

I'll give you your due - if the manufacturer says the sweet spot for Optima Yellow Tops is 80% depth of discharge, then they are indeed a better AGM battery than average in terms of the practical use vs length of life equation. But I'll bet they last even longer if you only take 50% out of them each time.

The other thing that begs comment is that test in the link you provided. That "test" proves only that the battery tested withstood abuse a few times and in each case accepted charge and apparently fully recovered. Any battery will do that and will appear to operate normally for some time afterwards. MY OEM battery in my BT50 has been flat at least 7 times in the 18 months I've owned it, due to the quirky design of its electrics. It still behaves like a new battery, but I'll be very surprised if I get another winter out of it - unlike the OEM battery which lasted 5 years in my previous vehicle and which never got flat.

What wasn't tested in the link was the effect the abuse had on both the capacity of the battery and its longevity. It may well be that the Optima Yellow Top will handle that sort of abuse better than some other batteries, but that was not established, just that it could handle it a few times.

The "torture test" was not a test, just a few blokes hooning around in electrical ignorance, abusing equipment and presenting the results in a favourable report - probably to keep the advertising dollars coming into their magazine.

It was rubbish, mate.

As Frank has pointed out, Optimas can be killed like any other battery, interestingly they do state or at least did on the Australian site that discharging to 0% SOC won't harm them, however if you ask them to supply a life cycles versus depth of discharge they refuse stating that it is commercially sensitive information!

If it is a good as they imply you would think they would be happy to supply the proof?

Figures I last found for an Optima were from memory was something like:

1200 cycles to 0% SoC ( 10.5v ) and 2,000 to 20% SoC ( 11.58v ), like any other lead acid battery they improved dramatically as DOD decreased.

Not at all sure where you two get the idea that I say they cannot be killed.
I'm simply saying that they handle a much deeper discharge than most other batteries.
Read into that what you will but try hard to take it with the context of the OP?

The review was supplied as 'interesting'. I've never seen a battery survive the sort of problems that were shown in it.
Again Frank read into that what you will.

I haven't seen any hard data that proves Optima's can tolerate deep discharges
better than any other battery. Certainly Optima won't supply anything to back up their claims, if you have hard data I would like to see it?

If this info is correct the following is an interesting read Malcom http://www.aussiebatteries.com.au/deep-cycle-battery-info/

Thanks Batts, yes I have heard of this being done, but the idea of a battery box, which will be portable, I think is a great idea, I can also use it in the tinny, with the electric motor, which will be a big advantage.. Great read about batteries that you put above, appreciate that.. Thanks Odog