Solar Question

Submitted: Saturday, Jun 23, 2012 at 08:11
ThreadID: 96441 Views:5653 Replies:5 FollowUps:9
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Trying to figure out what is gong on with our Solar set up.   Previously we have gone upto 4 days in bleak conditions using tv laptop lights etc everything before we ran out of power.   Now we are not even making it through the night when ever our engel is plugged int ?...    Set up is 2.5 years old.   We have not free camped much for over a year so have not noticed this problem til now.  We have 2x135w Kyocera panels, prostar 30 controller, 2x ACDelco marine/RV maintenance free HCM27SMF 97 amp hour batteries with max recharge of 14.7 volts, solarforce battery protector SFBP-1240A cuts in Lvd at 11.4v, CTEK multi xs 25000 battery charger.
The only new thing added to our consumption is the Engel in our ute. When we are camped we now plug it into the vans 12v. If it was to run 24 hours it would use 72amps, other lights tv etc I estimate to be another 42 amps. Total max 114amps per day.
I've tried to put as much detail as possible
Would be great if someone.can unravel this for me.
Am I expecting too much from the set up or is there an issue?
Thanks in advance :)
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Reply By: Sand Man (SA) - Saturday, Jun 23, 2012 at 09:25

Saturday, Jun 23, 2012 at 09:25
You haven't stated how big the Engel is but this may be affecting the higher consumption of the van batteries, espesially if you have a longish lead back to the vehicle.

It is more likely however, that the van batteris are shot and not reaching their full charge capacity.
The only way to check this is to charge each battery with the 240v charger then take them to a battery shop or auto electrician where they can be load tested.

Bill


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Follow Up By: MEMBER - Darian, SA - Saturday, Jun 23, 2012 at 10:04

Saturday, Jun 23, 2012 at 10:04
I'm with Sandy - it could be one of a number of factors in the charging connectivity I guess (I'm no electro-whizz), but it sounds very 'battery' to me, because I've been there. My 3 x Ritar 100Ah's gave up after 3 years in the middle of a trip - in that they simply got too low, far too fast, no matter how well charged - overnight use of appliances was out of the question (compressor fridge in use). Had to ditch them at Pt Augusta and get 3 new DC Century AGMs. Ouch $$$$. By reports, these things should and often do last a whole lot longer, but mine got between 12 and 11V a couple of times when I had no sun and could not use a genny. My general habit is to keep the batteries full as a goog by whatever means available, wherever I am. As Sandy says, professional evaluation is worth the $, considering the replacement costs (but you'd need someone who 'really knows' batteries - crikey - some of the people in battery retail can be a worry).
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Reply By: Member - John and Val - Saturday, Jun 23, 2012 at 10:00

Saturday, Jun 23, 2012 at 10:00
Hi Molly,

The straight answers are – Yes you have a problem, and No, you are not expecting too much from your system. It sounds a good setup to me with plenty of storage and good solar capacity. You don’t mention how (if?) you are charging from the vehicle when the engine is running, so I assume it’s a simple system with a controller in the engine bay and then a long run of wire from the engine to the van.

Assuming I’m right about charging from the engine, I’d be very suspicious that you are not getting a decent charge from that wiring. Perhaps you never have had a good charge, so the batteries were never fully charged, but without the fridge making demands this didn’t show up as a problem until now.

Suggest check, with no fridge or other load connected and no solar charging, the van battery voltage, then start the engine and measure that voltage again. 1) If it doesn’t rise at all you have a break somewhere between engine and van batteries, possibly at the connection at the towbar. 2) The initial voltage should be around 12.6 to 12.8 volts and this should rise when charging. Ideally the charging voltage should be at least 14.4, though if the battery is much discharged it won’t be this high. If it’s less than about 13.4V I’d check the voltage at the vehicle’s own battery (that’s what’s feeding the charge line to the van batteries.). For most vehicles the battery voltage should be around 14.4V while charging, dropping a bit as the engine warms up. If there is much voltage drop (say more than about 0.75V) between the vehicle battery and the van battery, you have found your problem – could be the wire between them is too small, could be a dirty connector or a bad connection somewhere. (Note that this all assumes that I’ve assumed rightly about your setup!!) There are two wires involved here, one positive and one negative, and each contributes its own losses. Ideally both should run all the way from engine to van batteries, though often the negative one will simply be connected to the vehicle body – check that connection! This wire should be heavy, 6 B&S size is good (that’s about 6mm diameter).

One final point – Measurements and units of measure are confusing. Your 2 batteries have a total (nominal) capacity of about 200 amphours, i.e. you could expect to draw say 10 amps from them for 20 hours, or 20 amps for 10 hours, or 1 amp for 200 hours. It isn’t quite that simple, but close enough for present purposes. Assuming the motor in your Engel actually runs for about 1/3 of the time, and that it draws about (say) 3 amps when running, it will draw an average of about 1 amp, so in 24 hours will require 24 amphours. In our experience, the fridge accounts for most of the daily drain, lights etc are relatively minor. On this basis, your daily drain isn’t likely to exceed 50 amphours, so your batteries should be ok for up to 4 days without any charging. (Actually it’s best never to fully discharge them, so say 3 days.)

A final thought – is there a 3 way fridge in the van that’s also connected to these batteries? If so, it is quite capable of flattening the batteries overnight. These fridges draw 12-15 amps continuously and cannot be run satisfactorily from batteries. Because of their high demand, they shouldn’t share the same wiring from the engine bay that’s used to charge the batteries either.

You might find Electricity for Camping a useful read.

Cheers

John
J and V
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Follow Up By: Member - John and Val - Saturday, Jun 23, 2012 at 10:14

Saturday, Jun 23, 2012 at 10:14
I agree with Sandman that the batteries could be an issue, though they'd have to be very tired to have lost so much of their capacity. Another good measurement to make is the current (amps) flowing in/out of your batteries when charging and discharging. This is a bit more complicated, but any battery supply place should be able to help.

Cheers

John
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Reply By: Member - Captain (WA) - Saturday, Jun 23, 2012 at 10:09

Saturday, Jun 23, 2012 at 10:09
Hi Mrs Molly,

You seem to have a good setup and it should easily handle your load. The Engel will typically use 40-50 A/hrs over a 24 hour period, though this will vary with size and temp (I run 2 x 40L engels, one as a fridge and the other as a freezer). Your total load would likley be less than 100 a/hrs over 24 hours but even if 114 a/hrs, your batteries should easily supply this overnight. Throw in 270W solar and it should last indefinetly in sunny conditions.

As said above, I too would suspect one or both of your batteries are shot. While they may apear to be fully charged, they have likley sulphated and no longer capable of holding their 97 a/hr capacity. I too would suggest you have your batteries load checked. Also, perhaps add a battery monitor in the van, its is a good way to measure your battery usage (I have a Nasa BM1 and it is very useful) and will highlight a problem like this before it occurs.

Cheers

Captain
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Reply By: Member - Boobook - Saturday, Jun 23, 2012 at 10:17

Saturday, Jun 23, 2012 at 10:17
An important consideration is what model Engel do you have, and are you using it on freeze at all?
AnswerID: 489215

Follow Up By: MrsMolly - Saturday, Jun 23, 2012 at 11:27

Saturday, Jun 23, 2012 at 11:27
Wow thanks everyone , the engel is a 57l combi MT60F-G4C-S and we are using it half fridge half freezer. The 12v lead to the fridge is 10metres long.. Batteries charge up to 14.4 on the screen by Solar or Genie.
I think when we are driving the truck only runs the fridge, couldn't be sure on that one.
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Follow Up By: Member - John and Val - Saturday, Jun 23, 2012 at 13:45

Saturday, Jun 23, 2012 at 13:45
Molly,

Engel's specs for that fridge are not very helpful - it draws from 0.5 to 4.2 amps - maybe that's an average, maybe a characteristic of the fridge electronics. Either way nor very helpful. In any case, the actual average current drawn will vary with your usage patterns and ambient temperature, so it's hard to put a figure on your daily power requirements. Certainly though, if your batteries are ok and are well charged, you should get much more than just an overnight run from them.

If you aren't charging from the truck it's a whole new ball game, and the question then becomes, how are you charging the batteries? Suggest try to work out an energy budget as suggested in the link I gave earlier.

BTW, the 10 metres of cable from batteries to fridge may also be an issue for the fridge. Unless it's pretty heavy cable there can be considerable losses over that length, especially when we consider that there are actually 20 metres involved since losses occur in both the negative and positive legs.

Cheers

John

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Follow Up By: Member - Boobook - Saturday, Jun 23, 2012 at 15:33

Saturday, Jun 23, 2012 at 15:33
Molly, like the Waeco combo, that Engel fridge is very hungry on power. The issue is that freezing takes about 3 - 4 times the power of cooling. If you don't use the freezer you may be able to turn it down ( up) a little so it doesn't freeze. I believe it will average about 2.5 amps, that's about 60 AH per 24 hours. In other words a your two 97AH batteries will last about 42 hours before they are flat ( down to 50% capacity) if you use nothing else.

Try using it as a fridge only, I am pretty sure it will dramatically improve the battery life.

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Reply By: Member - Bruce C (NSW) - Saturday, Jun 23, 2012 at 13:02

Saturday, Jun 23, 2012 at 13:02
Hi Mrs Molly,
If you place each of your batteries, one at a time, on the CTEK and put them on recondition mode it should solve any sulphation problems. Check the voltage of each before and after charging and a couple of hours after that to give you a pretty good idea of what is going on.

Your solar panels should be able to do all you require given normal sunny weather, that is a typical day, part cloudy but mainly sunshine, even in the middle of winter.

As the others have said you have a very good setup so I would also think your problem lies in the batteries.

At quiescent state (resting) your batteries should have about 12.9 volts a couple of hours after being charged up, as they get older this level drops but unless there is something wrong with your battery/batteries they should read somewhere around 12.7 volts.

Cheers, Bruce.
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Follow Up By: MEMBER - Darian, SA - Saturday, Jun 23, 2012 at 15:18

Saturday, Jun 23, 2012 at 15:18
Re using the CTEK to give them a recon - as I recall from reading the CTEK manual, the Recondition mode is for flooded batteries only - yours are probably Gel class or maybe AGM.
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Follow Up By: Member - Bruce C (NSW) - Saturday, Jun 23, 2012 at 16:48

Saturday, Jun 23, 2012 at 16:48
It appears you are correct in the battery type Darian, I was assuming they were flooded cell.

Bruce.
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Follow Up By: MEMBER - Darian, SA - Sunday, Jun 24, 2012 at 12:09

Sunday, Jun 24, 2012 at 12:09
Batteries - so many types and models ! My 3 Century AGM's seem well suited to the van (cool and can withstand road shocks to an extent) but in my engine bay I have a flooded Century DC as my aux. Warranty is void if Century AGM's go in the engine bay. I'm sure there are heat tolerant non-flooded DC's somewhere for my engine bay, but after awhile I just have to do it and get on with my other hobbies !
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Follow Up By: oldtrack123 - Wednesday, Jun 27, 2012 at 10:41

Wednesday, Jun 27, 2012 at 10:41
HI
Re Quote "At quiescent state (resting) your batteries should have about 12.9 volts a couple of hours after being charged up, as they get older this level drops but unless there is something wrong with your battery/batteries they should read somewhere around 12.7 volts. ""

Just remember this does not indicate the actual remaining Amphr capacity

Batteries can still charge to full SOC voltages but may only gave a small% of their ORIGINAL Amphr capacity

I would suggest one or all the batteries are low on capacity due to age, sulphation not being kept fully charged etc
But do not simply replace them .
Ensure your charging systems are working correctly.

Peter
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