Solor again

Submitted: Tuesday, May 03, 2005 at 12:04
ThreadID: 22604 Views:2124 Replies:7 FollowUps:7
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Hi all. Just when I though I had things sorted out with solor power got to think
again.On the latest trip running 2x40lt engels (1fridge-1freezer). 2x80and1x75watt
panels. The temp during the day was 36-40deg and down 20 overnight. I found
that the engels were cycling continuious.the freezer one battling to get down to
-7. I used to turn it back down to try and get through the night. In the morning
when checking the battery with a multi meter was down to to about 12.30.
Would this be doing the battery any damage letting it drop this low every day?
Am now thinking that a small gen going for a couple of hrs at night might ease
the drain on the battery.or might have let it get cooler before i go again.
Cheers Brian
Yer Rox not to far out with your guess.
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Reply By: V8troopie - Tuesday, May 03, 2005 at 18:24

Tuesday, May 03, 2005 at 18:24
Would that be an Engel fridge with their famous 'swing' compressor? I found them a poor performer when running on battery power. Generator or car power, yes, battery power, no good.
Get a fridge with a ROTARY compressor if you want reliable battery operation.

As long as your battery gets charged up reasonably soon it should cope with draining down to 12.3V

AnswerID: 109489

Follow Up By: Member- Rox (WA) - Tuesday, May 03, 2005 at 19:38

Tuesday, May 03, 2005 at 19:38
Mine(40lt) works fine on battery power I've been traveling for nearly 7 months now no problems in fact it had it on freeze (good fishing) for over 3 weeks through the desert also froze 2x 2lt of water every night to put in esky.
FollowupID: 366102

Follow Up By: Member - Jimbo (VIC) - Tuesday, May 03, 2005 at 20:44

Tuesday, May 03, 2005 at 20:44
I always found my Engel to perform extremely well. Performed brilliantly on battery power. I now own a Waeco and will not get into the "which is better debate". They are both great.

The swing versus rotary debate is worthless, they've both proven to be reliable and efficient.
FollowupID: 366114

Follow Up By: Mainey (WA) - Thursday, May 05, 2005 at 11:43

Thursday, May 05, 2005 at 11:43

what brand of fridge are you referring to with a "rotary" compressor

FollowupID: 366361

Follow Up By: V8troopie - Thursday, May 05, 2005 at 15:52

Thursday, May 05, 2005 at 15:52
Mainey, what I was referring to is a 'positive displacement' compressor, eg, a piston or rotary vane type of any brand. (Danfoss is a good one)
Engel "swing" compressors are NOT positive displacement, the oscillating movement of the piston depends very much on the applied magnetic field which in turn depends on the battery voltage. Its a very simple system but can suffer badly from low voltages where the piston travels a little less stroke and has to pump much longer to get the job done. Its a vicious circle, very noticeable on the older type engels ( like mine), the newer ones have a much better voltage regulation I believe.

A rotary type compressor pumps the same pressure as long as there is power to drive it available.

FollowupID: 366409

Follow Up By: Mainey (WA) - Thursday, May 05, 2005 at 18:30

Thursday, May 05, 2005 at 18:30
I took it to mean 'rotary' as in the commercial air conditioning compressors, or similar design to the Mazda RX7 rotary engine, a single compressor with multiple ports turning continuously in only one direction without stopping, while on the other hand the Danfos compressor is actually a piston, and similar to a car engine, it goes up, stops, goes down, stops, and continues in the up and down movement, similar to a car engine, hence the ‘slap’ noise in older, well used, compressors, and lack of compression to move around the refrigerant with excessive wear and tear.
The rotary compressors are becoming widespread with commercial air-conditioning system manufacturers because they work more efficiently and have no vibration or noise.
FollowupID: 366439

Reply By: time waster - Tuesday, May 03, 2005 at 18:51

Tuesday, May 03, 2005 at 18:51
i thought you could safely go down to 11.2volts if you only drop to 12.3 over night thats excellent.
AnswerID: 109492

Reply By: Member - Jimbo (VIC) - Tuesday, May 03, 2005 at 20:39

Tuesday, May 03, 2005 at 20:39

There's something going wrong somewhere. Even allowing for 80% efficiency from your panels in that heat (assuming they're polycrystalline panels) you still should have been getting about 16 amps in full sun. Your 40L Engels should only draw a max of 2.7 amps each when running so you should have been well ahead.

Were your fridges in the sun? A 40L Engel on full blast should easily get down to neg 12 to 15. My 39L, older and less efficient, would easily hold neg 15 in any conditions (out of the sun) and neg 21 in cooler conditions.

12.3 volts is fine, indicates about 70% charge. This is OK first thing in the morning after running all night with no solar input.


AnswerID: 109507

Reply By: Member - Brian (WA) - Tuesday, May 03, 2005 at 21:31

Tuesday, May 03, 2005 at 21:31
Hi Jim. Maybe I was expecting more as I don't seem to be any bettar than
last year when I was using just 2x80 panels.for the same result. The 2 engels are only a couple of yrs old. they were in the back of the wagon I had the doors up
as I said the daily thermometer readings were 38-40 (1.00pm)maybe just to hot.The multimeter readings
at 7.00am ranged from12.24-12.44.Going again mid june see what happens then.
Been into a metel frabrication shop. getting a new frame made to get bettar angles
for the sun. cheers brian
AnswerID: 109518

Reply By: joc45 - Tuesday, May 03, 2005 at 22:25

Tuesday, May 03, 2005 at 22:25
A few points to consider;
- "Engels were cycling continuous" - does this mean running continuously or cycling on/off? In 40deg heat, the Engel will probably be running nearly continuously as a freezer. At fridge temps, it should be doing a lot better.
- In practice, 155 watts of panels translates to about 10-11A of current into the battery, as the wattage is quoted at somewhat higher volts than 12v - more like 14-15v.
Was there any cloud? Panel output drops by several magnitudes with cloud cover; ie, 10A full sun can be 2-3A with cloud cover.
- Temperature - Output is generally quoted at about 20degC. Many solar panels drop their output by up to 20% in high temps.
- The low quoted current on the latest Engels seems to be offset by longer running time; On a trip a not long ago, a friend's Engel was observed running much longer than my Autofridge for the same internal and external temps.
- From previous postings and from some suppliers, people seem to quote using about 150w of panels for a single 40L fridge for a long-term stay; ie, no other charging; I get by with about 120w. This is more than enough on hot sunny days, but can be borderline on warm cloudy days.
AnswerID: 109537

Reply By: Mainey (WA) - Wednesday, May 04, 2005 at 23:31

Wednesday, May 04, 2005 at 23:31
(Quote)2x80and1x75watt = 225 watt, the engels were cycling continuous. In the morning the battery was down to about 12.30v (end quote)

IMO the batteries are realistically getting 11 a/h x 9 hours daily, up north, from the 3 solar panels and the fridge should be using ~10 a/h…… if cycling continuous, according to the advertising blurb from Engel. They quote a low 2.8a/h for perfect conditions and cycling on/off, at +4 degrees, in the real world and in extreme outback temps as mentioned 36-40 deg, the Engel would be running flat out and using power to the max.
11 amps X 9 hours = 99 amps into the battery.
10 amps X 12 hours = 120 amps MINIUM out of the battery…. (realistically 180amp)

Will it do damage to the battery.. depends on the battery, is it a quality DC battery?
designed to be deep cycled or a cranking battery designed to start a vehicle?
AnswerID: 109733

Follow Up By: Member - Brian (WA) - Thursday, May 05, 2005 at 10:30

Thursday, May 05, 2005 at 10:30
Hi Mainey. the battery is a new d/c trojen 130ah. I did do as you suggested once before. I ran 1x75 panel strait to the battery, by passing
the regulator. I did mean running flat out. And there was cloud cover
in fact we left early because one day there was no sun.and the next we
got up at six looked like it was going to be the same so we packed up an left. It was hot and the flys. I have got use to it being mid 20s during
the day and down to 0-2 at night when we usually go.I think they are the perfect
conditions for useing solor we have been up there and not seen a cloud
all week. I was in bunnings yesterday looking at those cheap genorators
as a back up. brian
FollowupID: 366348

Follow Up By: Mainey (WA) - Thursday, May 05, 2005 at 11:38

Thursday, May 05, 2005 at 11:38
As I have posted, the charge from the solar panels into the battery is not sufficient to continuously power the two Engel’s under the conditions you have nominated.
It’s not that the charge from the three solar panels into the battery is not high, but the power required by the two Engel’s is even higher, and it would be more efficient use of power to run a larger fridge/freezer combination, as most 100Ltr fridge/freezers use far less than you are using now.
As to using a generator it would be running hard to keep up with the Engel's also.

Could the battery, panel and fridge wiring need some investigation as to voltage loss as it appears your fridge’s use far more power than I would expect ?
OR, the solar system is not feeding into the battery, maybe the regulator is suspect?

You say you "ran 1 x 75w panel strait to the battery, bypassing
the regulator" I understood you were using three solar panels ?
FollowupID: 366358

Reply By: TheUndertaker - Thursday, May 05, 2005 at 18:17

Thursday, May 05, 2005 at 18:17
Well my maths might not be the best but if your 2x80+1x75 cant run 2x 40lt engles you have a major f/up going on,,, I scored a 64watt unisolar dirt cheap so decided to go whole hogg on solar, bought a 120watt kyocera for a total of 184watts ,, run thru a plasmatronics pl20 regulator , the unisolar puts out at best 3.8amp , add the kyocera at 7.1amps = 10.9 amps per hr in "perfect" conditions,,
ANZAC day w/end camping started on solar saturday am with AGM batts reading 13.42 unrested[driving to camp] ,,,ran 80lt waeco + 15lt engle [on paper draw 7amp per hr] ,, leaving campsite 2pm monday batts reading 12.42 ,, w/end had overcast,rain,and full sun ,,,, I would be checking all your wiring and connections.
AnswerID: 109872

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