Solar question

Submitted: Monday, Sep 21, 2015 at 22:03
ThreadID: 130359 Views:1933 Replies:9 FollowUps:29
This Thread has been Archived
I am building a small off road popup camper and I'd like to be able to run a little inverter aircon off the batteries at night. It is at the design stage and I am new to all of this and would appreciate some advice from wiser heads.
It will have a 400-600 AH LiPo4 battery bank with an 800 watt solar array, supported by a big alternator in the tug with a 160 amp 12v to 12v charger for a quick top-up. I don't want a noisy generator.
The best light weight solar panels I can find are 25 watt nominal voltage. If I run a controller like this one eBay MPPT Controller will I be okay?
Many thanks
Keith
Back Expand Un-Read 0 Moderator

Reply By: Gronk - Monday, Sep 21, 2015 at 22:43

Monday, Sep 21, 2015 at 22:43
Pretty impressive power supply......have you costed it out yet ?

Even so, I don't think you will run an aircon for any decent length of time.....I know you can get units that will run at approx 60A, and if you do some sums, it sounds feasible, but say you drained the batts down to 20% ( no big problem with LiPo ), how are you going to recharge them ? At a guess, 40A from your 800W solar panels won't be enough, so a minimum of approx 1200W would be needed ..
AnswerID: 590571

Reply By: PhilD - Tuesday, Sep 22, 2015 at 00:50

Tuesday, Sep 22, 2015 at 00:50
Check out the thin solar panels and gear at Solar4RVs. Where are you planning to get your Lithium from? There is a huge difference in pricing between the suppliers. What current draw does the AC have at 12 volts? That will determine how successful the set up will be.
AnswerID: 590575

Follow Up By: skulldug - Tuesday, Sep 22, 2015 at 01:10

Tuesday, Sep 22, 2015 at 01:10
Another vote for Solar4RVs. Expert advice and all the quality gear you could want at very competitive prices.

Lithium batteries and thin, direct stick panels have enabled me to have a system that would have been impossible using older technology because of weight. I'm two years in with the battery technology and it has performed faultlessly.

Skull
0
FollowupID: 858590

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 08:12

Tuesday, Sep 22, 2015 at 08:12
Skulldog, can you outline your system?
Keith
0
FollowupID: 858594

Follow Up By: skulldug - Tuesday, Sep 22, 2015 at 15:37

Tuesday, Sep 22, 2015 at 15:37
Hi Keith,

I have two x 135 w flat direct stick panels feeding into two x 90 ah LiFe Po 4 batteries. I have a battery computer unit that calculates state of charge using a shunt.

The van is a full ensuite 19' Crusader. The system has to run various LEDs, 60 l Waeco fridge, TV, sound system, iPhone, iPad charging etc.

The only 240 v appliance we run is the washing machine and for this I have installed a 700 w inverter.

In terms of performance, I have never seen the SoC below 50 %. And that was after four days of rain in Tassie. Our normal use is down to 85% after a single night and that returns to 100% before midday.

The mains charger remains off even when in caravan parks as it gets enough from the solar system and the manual for the batteries says not to trickle charge them.

The only bit missing from my puzzle is that I don't use the Anderson plug to charge the van batteries from the alternator as I haven't worked out whether there is a need to have some sort of isolator between the alternator and the panels.

I purchased the panels, controller and computer from Solar4RVs and the batteries from Evworks.

When looking at price, they are currently listed at $675 for a 90 ah battery, you need to remember that they weigh half as much, can handle many times more cycles and can be discharged down to 20% SoC without harm.

Now the usual disclaimers -no connection to the firms mentioned. I'm a user not a techo and don't want to be dazzled by the Internet experts.

Hope this helps.

Skull
0
FollowupID: 858623

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 19:39

Tuesday, Sep 22, 2015 at 19:39
Thanks Skull. It does indeed help.
That sounds like a very elegantly designed system. As I understand it, your Anderson and your solar can work together, as they will agree on the voltage between themselves. But it's not been easy to find DC-DC chargers for LiPo4 batteries, but Sterling Power now have them - some very big ones too.
Many thanks for your comments.
Keith
1
FollowupID: 858634

Reply By: Member - KeithB - Tuesday, Sep 22, 2015 at 08:11

Tuesday, Sep 22, 2015 at 08:11
You're right that it's not going to be cheap. I have been looking at EV Power in WA for the batteries as they seem to offer the best value.
Solar panels come and go the thin lightweight ones are getting cheaper by the day. I have been looking at these: eBay thin panels. At a pinch I could get 1,000 watts on the roof.
The smallest aircon I can find is the 2.1Kw Fujitsu which draws 2.2 amps at 240 volts on low setting. I guess that's about 50 amps at 12 volts when it's running. Stirling Power has some very big 12v-12v chargers that will now do LiPo4 batteries. a 400AH battery weights 50 kilos.
There are a number of suppliers in the USA who can do alternators that supply 200 amps at idle for most 4WD's and the plan would be to run the tug while the aircon cools things down.
With an 800-1000 watt array and a good MPPT controller I was hoping for at least 250AH a day in northern areas in summer. Is that reasonable?
The cost is high. With batteries, solar and all of the gubbins to run the show, the budget looks like this:
Battery $3,500
Controller $800
Charger $800
Alternator $1,000
Solar $3,500
Cabling $500
Inverter $400
Aircon $1,000
TOTAL $11,500

So it's not a cheap day out. But a normal RV style aircon and an antisocial gennie will cost about $4,000 on their own. By the time I get the thing built I am hoping that the costs will come down, particularly if the Aussie dollar goes back up again.
But I am still wondering if the project is overly ambitious.
Keith

AnswerID: 590580

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 08:14

Tuesday, Sep 22, 2015 at 08:14
Sorry, that's 58 kilos for the battery.
Keith
0
FollowupID: 858595

Follow Up By: Member - John and Val - Tuesday, Sep 22, 2015 at 08:23

Tuesday, Sep 22, 2015 at 08:23
Keith,

I was typing (below) while you were posting so didn't see your numbers. Strongly agree with your aversion to antisocial gennies, but I think that you can achieve a decent outcome without going to such a big system.

Cheers

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

Lifetime Member
My Profile  My Blog  Send Message

0
FollowupID: 858597

Follow Up By: PhilD - Tuesday, Sep 22, 2015 at 09:50

Tuesday, Sep 22, 2015 at 09:50
Keith, I agree with most of your numbers, except the inverter. You will need at least a 2000 watt pure sine inverter, and preferably a transformer based one for off road durability. The cost will be a lot more than $400. Have you tried EV Works, as they were the best value for money when I bought my cells? it is very important to get your charging right, to ensure the life of the battery. Each manufacturer of Lithium has different charging limits, so it is a matter of matching the charging eg MPPT, DCDC, etc so they are all functional.
0
FollowupID: 858599

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 10:05

Tuesday, Sep 22, 2015 at 10:05
Thanks Phil
I have not chased down inverters yet and I think the one I looked at was 2Kw with 4Kw peak on eBay. But it did look too cheap to me.
I guess I will need a charger and controller with adjustable output voltage.
The management system that comes with the batteries is a double backstop against overcharging and excessive draw down. But I am a novice at this and really value all of this help. I will look at EV Works as I get closer to buying. Still haven't built the damned camper.
Keith
0
FollowupID: 858600

Reply By: Member - John and Val - Tuesday, Sep 22, 2015 at 08:14

Tuesday, Sep 22, 2015 at 08:14
Kieth,

That's a lot of expensive power. A few things to consider:

I wouldn't try to run such a system at 12 volts as the currents will be huge, leading to major losses. The MPPT controller you suggest can be used at up to 60 volts which might help, though introduce other problems like sourcing a non-standard dc-dc charger to charge from the vehicle, and a non-standard inverter to run the a/c (assuming a conventional ac driven a/c).

An 800W solar array (lots of square metres of it) will be difficult to carry and will need some supporting structure at camp. More setup, more stuff to carry.

I wonder if an easier solution might be to insulate well, and simply use a smaller fridge system.Even feeding incoming air through a conventional 12v fridge would probably give you a good cool night's sleep for a fraction of the proposed energy budget.

Another thought - maybe talk to a refrigeration person about tailoring something based on a small compressor driven by a dc motor. This could be fabricated fairly easily, perhaps largely from automotive a/c components. Indeed, how about gutting a standard 12v fridge and building it into the camper?

Please let us know how you go, as it's very helpful to others who contemplate looking outside the conventional.

Cheers

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

Lifetime Member
My Profile  My Blog  Send Message

AnswerID: 590581

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 08:21

Tuesday, Sep 22, 2015 at 08:21
John,
The inverter will sit right by the batteries and you are right that the cables will be huge (and heavy). I spent a lot of time looking at the 12volt aircon systems that they use in truck prime movers. But, like the Rv rooftop aircons, they cannot offer inverter technology, are a pain to install and end up costing $4,000-$5,000 on their own. And they still leave the basic power supply problem.
The domestic inverter aircons are lighter and more efficient plus are very cheap to buy and maintain.
0
FollowupID: 858596

Reply By: Member - rooster350 - Tuesday, Sep 22, 2015 at 09:47

Tuesday, Sep 22, 2015 at 09:47
You sure are going to a lot of trouble and expense just to get a bit of cool air at night, we have been to Darwin a few times and it sure was hot , but a little Sirrocco 12v fan that uses all of .5 amps at top speed and weighs about 1kg and is very easy to carry kept us cool running all night at half speed and no noise. Your 800w of panels sitting flat on your roof sure aint going to give you 800w and you say it is a small poptop, good luck fitting them on and / or setting them up each day, and the WEIGHT.. whew. We also have a "noisy generator" , but if you are standing about 30ft from it you can not hear it and if I put the noise deflector around it you can be even closer to it without hearing it...cheers
AnswerID: 590585

Follow Up By: Gronk - Tuesday, Sep 22, 2015 at 13:30

Tuesday, Sep 22, 2015 at 13:30
Rooster is on the money.....

Not sure what state you are in, but I've been away over 200 times and only had approx 2 or 3 nights where it was hot enough to affect your sleep....and I haven't even got a fan.

I'd be spending a fraction of that on some insulation and plenty of ventilation for your build....and setup in the shade !
0
FollowupID: 858612

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 14:04

Tuesday, Sep 22, 2015 at 14:04
Hey Gronk,
My wife is going through the hot flushes thing and aircon is apparently not negotiable. I won't stay in caravan parks unless absolutely necessary so a powered site is not negotiable either. Generators are the modern scourge of camp grounds, so they are out too.
So aircon it is.
By the way, a decent "normal" power system with two AGM batteries, 200-300 watts of solar, 12 volt charger, controller, inverter and wiring won't leave much change out of three grand anyway. Plus I'd be buying new AGM batteries every five years or so. I think the big system will pay for itself in about fifty years.
Keith
0
FollowupID: 858616

Follow Up By: garrycol - Tuesday, Sep 22, 2015 at 14:43

Tuesday, Sep 22, 2015 at 14:43
Running refridge aircon is almost as noisy as a modern gennie.
0
FollowupID: 858620

Follow Up By: Member - rooster350 - Tuesday, Sep 22, 2015 at 15:13

Tuesday, Sep 22, 2015 at 15:13
Yes that is right ,garrycol...nothing worse than a air conditioner going half or some times all the night next door and trying to get some sleep , at least people camping with gennies have usually got them turned off by 9pm or so but not so the aircons in van parks, the attitude of some seems to be we have it we will run it and bad luck for anyone that does not like it. Usually you can not hear much of the noise the aircon is making from the inside of your van but your next door neighbor certainly can.
0
FollowupID: 858622

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 15:54

Tuesday, Sep 22, 2015 at 15:54
I agree with both of you.
But a small Fujitsu is just 44dBa at one metre, which is very quiet - about the same as a quiet urban street an night. Even so, I'd camp well away from anyone before turning it on.
0
FollowupID: 858626

Follow Up By: Gronk - Tuesday, Sep 22, 2015 at 16:34

Tuesday, Sep 22, 2015 at 16:34
Ha ha, my wife is going thru the hot flushes as well.....but she aint getting aircon !!

Bit of a misconception about the lifespan of LiPo batteries....they haven't been around long enough for reliable stats on that.....early reports from USA point to no longer spans than a well looked after AGM..

If you can get an aircon unit that will only use 40A running ( don't forget start up current, which can be up to 6x run current ) and you use it for 8hrs ( 320 a/h ), your batteries are down to approx 20%.....what happens if you wake up to rain ?? You'll need to run the gennie for at least 6+ hrs.. even in ideal sunlight ( you'll have to move the panels during the day ) 800W will take 8hrs, which you'll be lucky to achieve most days.

I know KK do aircon units for their campers, so a look thru their site might give you some ideas !

0
FollowupID: 858627

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 16:41

Tuesday, Sep 22, 2015 at 16:41
No batteries equals no aircon and we can get a quick charge of 120 amps or so from the big alternator on the tug to keep body and soul together.
0
FollowupID: 858628

Follow Up By: Gronk - Tuesday, Sep 22, 2015 at 17:54

Tuesday, Sep 22, 2015 at 17:54
Do you know anyone that gets a constant 120A from an alternator ?

If you can.....there is 3 hrs of run time from the vehicle ??

Sorry to sound pessimistic, but you have a big problem to solve....get it wrong and you have spent a lot of money for nothing !
0
FollowupID: 858629

Follow Up By: Member - KeithB - Tuesday, Sep 22, 2015 at 19:51

Tuesday, Sep 22, 2015 at 19:51
I have been looking at these alternators for my 200 series. 220 amps claimed at idle. There are quite a few USA suppliers of similar alternators.
http://www.m2kinc.com/pdf/174-brochure.pdf

0
FollowupID: 858635

Reply By: Member - Scott M (NSW) - Tuesday, Sep 22, 2015 at 18:50

Tuesday, Sep 22, 2015 at 18:50
Thought about a 12v air-con - would probably have similar draw to a fridge and you aren't going through the attendant loss of an inverter. Plently of them on the web. For example:

http://www.rencool.com.au/product/rtk5/

The other thing to consider would be an ice-chest cooler - damn sight cheaper and it'll take you QUITE a while to chew through 11 grand of ice.... even if you ran your own firdge to create ice blocks it would still be cheaper.....

http://www.ebay.com/itm/Q25-Portable-12V-Air-Conditioners-Camping-Boating-Hunting-Tailgating-Aircrafts-/231626589603
AnswerID: 590612

Follow Up By: Member - KeithB - Wednesday, Sep 23, 2015 at 14:25

Wednesday, Sep 23, 2015 at 14:25
Thanks Scott
I did mention the Rencool earlier, but not by name. It is very expensive a bugger to install and uses a lot of power.
I have spent the night thinking about the idea of using ice from the fridge to power and aircon and the engineering is starting to make my head hurt.
Keith
0
FollowupID: 858655

Reply By: Member - Scott M (NSW) - Wednesday, Sep 23, 2015 at 14:42

Wednesday, Sep 23, 2015 at 14:42
maybe something like this?

http://www.ebay.com/itm/Companion-Rechargeable-Portable-Evaporative-Cooler-Fan-Unit-12v-240v-Caravan-New-/350977191678?hash=item51b7deeefe&vxp=mtr
AnswerID: 590646

Follow Up By: Member - Scott M (NSW) - Wednesday, Sep 23, 2015 at 14:49

Wednesday, Sep 23, 2015 at 14:49
http://outdoor.companionbrands.com.au/index.php?p=caty&sid=1407281381&l=

????
0
FollowupID: 858657

Reply By: Robin Miller - Wednesday, Sep 23, 2015 at 16:16

Wednesday, Sep 23, 2015 at 16:16
Understand Keith but its easier to run a 2kw generator Keith , lot cheaper and more reliable to , probably could be made quieter inside the van than the actual aircon with a bit of extra sound proofing box as some of the new gennies are pretty quiet, also the gennie can do other things and many carry them anyway as they reduce the need for excessive battery systems and weight.
Robin Miller

Member
My Profile  Send Message

AnswerID: 590649

Follow Up By: Member - KeithB - Wednesday, Sep 23, 2015 at 16:26

Wednesday, Sep 23, 2015 at 16:26
Thanks for all the replies.
I am still very anti-generator Robin as they give me the heebie jeebies whenever I have to camp near them.
The evaporative coolers are great but aren't so good in high humidity.
I guess I'll keep my options open till the time comes to make a decision next year - in the hope that the equipment will get cheaper, which it seems to be doing all the time. Chassis and air suspension are done, but I am still at the floor and water tank stage of the build and am about to start on the walls. So there's no rush.
If it the camper comes out looking like a home made crappy job, I'll ditch the aircon idea altogether.
Keith

0
FollowupID: 858660

Follow Up By: Robin Miller - Wednesday, Sep 23, 2015 at 17:21

Wednesday, Sep 23, 2015 at 17:21
Actually Keith I have been going heavily thru the planning stages myself for a homemade camper thats fits my requirements which are a bit different than most ( I insist on solid axle for stabilty , under 600kg built so no brakes required , steel so I can weld broken things , no gas bottles, no spare wheel - uses car one , and so on).

I will probably use a genny which I have never used before because it will in nett save weight/space.

Critical things that effect comfort were control of air flow over sleeping area with oversize vent fans to reduce noise and limit the uncomfortable time down to less than an hour per day which would eliminate extra cooling.

For me though I need to carry a dirt bike so that makes it extra difficult , as to make it all work I neeed basic covering to be approximately 4mm marine ply with no insulation, and this requires good airflow control because its not like fully enclosed box.

All fun - good luck on your project , I'd like to hear more one day.

Robin Miller

Member
My Profile  Send Message

0
FollowupID: 858662

Follow Up By: Member - KeithB - Wednesday, Sep 23, 2015 at 18:20

Wednesday, Sep 23, 2015 at 18:20
Robyn
Like you, I am also using a solid axle, but with Landruiser disks and wheels and a five link air suspension with dual shocks on a 1650 mm track. The solid axle gives you a much higher roll centre than these silly trailing arm things that everyone insists on using these days and is much stronger for the weight.

More interesting. I have decided to use 15mm Polycore for the body over a gal steel chassis. It's a 1mm epoxy glass sheet around a plastic honeycomb sandwich, which is very strong and weighs just 4 Kg per sq metre, with good noise, heat, impact and fire resistance. It's a bugger to work with and you have to do a lot of epoxy fibre-glassing and fairing, plus it's not cheap.

But my camper (if I ever get the damned thing finished) will have a pullout queen bed, hard roof, 33 inch spare, separate shower and toilet, 350 litre water capacity, 70 litre grey water, 220 litre fridge, diesel heating and cooking, internal kitchen and dining for four, plus the big electrical and aircon system - and, God willing and the floods don't rise, should come in at under 1,300 kg.
That's light enough to tow over the Simpson. Do post some progress shots or PM them to me during the build. I'll do the same if you are interested.
Keith
http://www.polycore-australia.com.au/
0
FollowupID: 858665

Follow Up By: Member - KeithB - Wednesday, Sep 23, 2015 at 20:57

Wednesday, Sep 23, 2015 at 20:57
For the record, I have no relationship with Polycore which may have looked the case in the post above.
Keith
0
FollowupID: 858676

Follow Up By: Robin Miller - Thursday, Sep 24, 2015 at 18:35

Thursday, Sep 24, 2015 at 18:35
Who cares Keith , its a great product .
Robin Miller

Member
My Profile  Send Message

0
FollowupID: 858730

Reply By: Leisha Shannon - Thursday, Sep 24, 2015 at 15:30

Thursday, Sep 24, 2015 at 15:30
Don't listen to the naysayers, we run a similar setup and can run the air conditioner all night.

The Mitsubishi Heavy Industries 2kw unit has a COP of 5.71 so it draws just 350W running flat out.

If the camper is relatively well insulated it'll use much less than this. On a 35c summers day in Brisbane we average a tad over 200W to keep the interior a lovely 23c

With a decent inverter (stay away from eBay cheapies, I like the Victron Multiplus with their 5 year warranty) that'll be ~230W from your battery.

230Wh * 12 hours = 2.7kwh or about 35% of your 600Ah pack.

I wouldn't worry about the DCDC charger unless your alternator puts out less than 14v, just run some nice thick cables from the alternator to the house bank and disconnect via relay (bluesea 500A are nice) when voltage reaches 13.8v or so.

If you're not driving every few days i'd invest in more solar... we have 1.6kw (1200W on the roof, 400W portable)

Victron have their "easy solar" products which are an inverter / charger and MPPT controller in one box , again with a 5 year warranty. They're more expensive than the dodgy eBay stuff initially but with a warranty like theirs you'll only pay it once.

AnswerID: 590706

Follow Up By: Member - KeithB - Thursday, Sep 24, 2015 at 17:07

Thursday, Sep 24, 2015 at 17:07
Thank you Leisha
That post of yours is breath for fresh air. The naysayers were getting me down a bit.
I already have a 175 amp Anderson plug direct from the alternator and a voltage controlled relay is easy to add.
Can I ask: What batteries and solar panels are you using?
Keith
0
FollowupID: 858725

Follow Up By: Member - KeithB - Thursday, Sep 24, 2015 at 17:17

Thursday, Sep 24, 2015 at 17:17
As on the model number Elisha. I found it on a different website.
Low power and reverse cycle too! Looks like the one to pick over the Fujitsu.
Keith
0
FollowupID: 858726

Follow Up By: Leisha Shannon - Thursday, Sep 24, 2015 at 22:23

Thursday, Sep 24, 2015 at 22:23
We have 300Ah @ 24v (Our truck is 24v) and we're using 4 of the LG Neon 300W panels on the roof , with 4 x 100W flexible from Solar4RVs (excellent service from these guys) as the portable panels.

We have no gas or diesel appliances, everything (HWS, induction cooktops, convection oven, AC, etc) is electric and only powered by the Sun.

The reverse cycle functionality works great, although it does use a bit more power. We had a 1c morning in June and the AC averaged 370W to keep the interior a toasty 28c

We've been on the road full time since May and not plugged into 240v since leaving home.

0
FollowupID: 858735

Follow Up By: Member - KeithB - Thursday, Sep 24, 2015 at 22:55

Thursday, Sep 24, 2015 at 22:55
That's fantastic Leisha. Looks like the equivalent of 600AH and 12 volts plus 1600 watts on the roof.
Keith
0
FollowupID: 858738

Sponsored Links

Popular Products (13)