power useage

Submitted: Tuesday, Mar 25, 2014 at 04:15

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Member - Stuart and Gunny

I run a new Weaco cr110 fridge full time,tv for approx 6 hour per night,lap top approx 6 hours per night,300-600 watt inverter for approx 6 hours per night plus lead lights.I have a new Alco Trojen 150amp agm deep cycle battery.The problem i have is im flattening the battery after 1 night of free camping.The next morning the reading is 10.4 volts.I can drive 200k and the reading only comes up to 12.4 volts.My alternator is 50 amp.The honda eu20i generator struggles to bring it up to charge unless i run it for excess time.The best results i have found is to run the generator and car at the same time.My charger is a new projecta 15amp 7 stage.The problem i have is i like to free camp but i run out of power after one night.Any advise would be greatly appreciated.Thanks all hopefully someone can explain things to me and what to do.

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Reply By: Glenn C5 - Tuesday, Mar 25, 2014 at 06:56

Tuesday, Mar 25, 2014 at 06:56

You obviously need more power so work out how much you use per day and go from there. Another battery is probably a good start and maybe hook up to a solar panel during the day to run the fridge. There are lots of options and a lots of people on this site with heaps of knowledge. ( I'm not one of them ) Good Luck

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Follow Up By: Member - PJR (NSW) - Wednesday, Mar 26, 2014 at 08:51

Wednesday, Mar 26, 2014 at 08:51

I agree with Glen and would like to share this with you.

We also had an issue and ended up putting a third battery under the bonnet. We run two fridges and camping stuff. A laptop is rarely taken and if taken is only used for about 15 minutes. Lights - not much. Inverter - no longer as I got a "cig lighter" battery adaptor for the laptop. No other 240V needs. Everything we have can be charged through the 12V system.

However we could sit in one spot and smell the roses for a couple of days and with our setup don't have to worry about battery usage. It has lasted three days without any charging.

The car came with two standard and after advice from the local Redarc people we split the original pair and put a third one in which was then "paired" with the second standard one. Both these two were then connected to the main battery through a 200 amp Redarc isolator. We asked about a further battery management system at a recent show and were told, again by Redarc reps, not to bother. What we had was fine.

And note that all three are exactly the same Allrounder 100 ah batteries. No deep cycle etc. A side benefit is that if one breaks we have a spare.

Phil

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Reply By: Member - John and Val - Tuesday, Mar 25, 2014 at 08:21

Tuesday, Mar 25, 2014 at 08:21

Stuart and Gunny,

Here are my guesses at your daily consumption.

Weaco cr110 fridge full time - about 40-50 amphours (Ah)
tv for approx 6 hour per night - about 10-15 Ah
lap top approx 6 hours per night - about 10-20 Ah
300-600 watt inverter for approx 6 hours per night - depends on the load on the inverter - (if the load is one CPAP, then maybe 15 Ah without humidifier, 30+ with humidifier, more with a heated tube)
plus lead lights - depends on wattage, whether incandescent, halogen, LED, flourescent and usage time. - allow say 5 Ah.

TOTAL at least 100 Ah, and maybe 120 or more.

That is a very big ask of a 150 Ah battery. Depleted like his every day and your battery will not live long. The other major problem is that you must supply at least that much, plus say 10% to deal with inefficiencies, to recharge your battery each day. The 50A alternator will not supply this directly in a reasonable time, even if you added a dc-dc charger to deal with wiring losses.

Suggest have a read of our Electricity for Camping which covers a lot of options.

My general suggestion is that you need to minimise your electrical demand, increase your charging capacity (maybe add solar panels? maybe increase the alternator size, improve wiring and maybe add a dc-dc charger? ) and very important - double or treble your battery capacity. Apart from economising, none of that is cheap.

Hope that's some help, though I'm sure such suggestions aren't welcome!

Cheers

John

J and V
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Follow Up By: Member - John and Val - Tuesday, Mar 25, 2014 at 08:28

Tuesday, Mar 25, 2014 at 08:28

Just checked the Waeco site - your fridge is claimed to use 2.2 to 2.5 Ah per hour, say 50-60 Ah per day. It is even greedier than I guessed above!

Sorry!

John

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Reply By: Member - Frank P (NSW) - Tuesday, Mar 25, 2014 at 09:11

Tuesday, Mar 25, 2014 at 09:11

I agree with John above.
If you can, try to reduce your consumption. If you cannot do that then you will have to throw money at the problem - more battery capacity, more charging capacity.

Can you get a larger alternator for your tug? If so there are some options to improve the charging while driving.

I think you need a much bigger mains charger provided your battery can take a high inrush current. If you get more battery capacity you will need a bigger charger anyway, just to keep generator run times reasonable. I'd be looking at a 40 to 50 amp smart charger. Your EU20i will handle that.

If you want to minimise your use of the generator by adding solar, I think you'd be looking at about 400 watts of panels plus a decent MPPT regulator.

The above is based on my experience with similar daily useage. My battery capacity is 320 amp-hours, 25 amp dc-dc charger while towing, 440 watts of solar, 40 amp mains charger, Honda EU20i genny. As long as the sun shines I am self-sufficient, the Honda is the cloudy day back-up.

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Follow Up By: Pauly_T - Tuesday, Mar 25, 2014 at 11:16

Tuesday, Mar 25, 2014 at 11:16

Apologies if I'm hijacking this thread but I am curious.

Whenever battery charging is discussed the standard replies of solar, dc/dc charging, generators, run the engine etc come up. No-one ever seems to mention petrol engined battery chargers and am curious why. Something along the lines of this petrol engined battery charger from ABR Sidewinder as an example. It seems quite small in size a well. Christies Engineering seem to have a range of them as well.

Maybe there are shortcomings like noise or running air conditioning, etc, I don't know.

Paul

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Follow Up By: Bob Y. - Qld - Tuesday, Mar 25, 2014 at 22:45

Tuesday, Mar 25, 2014 at 22:45

Pauly,

I'll have to get out more, didn't realise Christies were still going.

The smaller model charger from Christies was reputed to be very noisy, and one needed to buy the larger 120 amp(???) model to get the quieter engine. Then people probably went for the Honda eu10 & eu20's, so they had both 240v, and ability to run high amp battery chargers. Oh, and air cons too :-)

Bob

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Reply By: HKB Electronics - Tuesday, Mar 25, 2014 at 13:35

Tuesday, Mar 25, 2014 at 13:35

As others have written, you really need either solar or if your going to be traveling daily a bigger alternator.

Your simply consuming more than your producing, if the aux is located in the car and you have a standard type alternator outputting around 14.4V @ 22C adding a DCDC charger would be pointless as the alternator would put more charge in faster, assuming adequate cabling is installed.

If you have a low voltage type alternator and I doubt you have as it's only 50A fitting a booster diode if possible would give you the fastest recharge, fitting a 20A DCDC charger if you can't would also improve your charging.

If battery is in van then a DCDC charger may help but again you will be limited to a 20A unit.

It would be pointless fitting a 40A charger as you alternator will not have the ability to supply sufficient current to allow it to reach its maximum output.

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Follow Up By: Member - Frank P (NSW) - Tuesday, Mar 25, 2014 at 23:52

Tuesday, Mar 25, 2014 at 23:52

HKB and S & G, g'day

Just to be clear here, the 40 amp (or 50amp) charger that I discussed was not a dc-dc charger, but a mains charger to be run off mains or the generator. With the caveats expressed in my post, that would not be pointless.

A 40 amp dc-dc charger with the present 50 amp vehicle alternator would, in all likelihood, be a waste of money - pointless, as you say - but that is not what I was suggesting.

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Follow Up By: Member - John and Val - Wednesday, Mar 26, 2014 at 08:29

Wednesday, Mar 26, 2014 at 08:29

HKB,

Pretty unlikely the battery is in the vehicle. If it is, then first priority is to move it to the van! Now the combination of wiring losses and probably low alternator output (assuming a vehicle of recent years) will ensure that charging voltage is inadequate.

The other issue that's often overlooked is that vehicle alternators aren't made to output maximum current for extended periods. A 50A alternator will not survive if delivering close to 50A for hours.

I agree with you that a dc-dc charger is wasted if the aux battery is mounted close to the cranking battery. It will in fact reduce charging current. There is though a strong case for them where the alternator output voltage is low (as in most computer controlled alternators found in recent vehicles) or where the aux battery is some distance away and significant wiring losses occur.

Cheers

John

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Follow Up By: Bob Y. - Qld - Wednesday, Mar 26, 2014 at 09:19

Wednesday, Mar 26, 2014 at 09:19

As I recall, Stuart.......and Gunny, have a small motor home. Can't remember what brand.

Bob.

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Follow Up By: HKB Electronics - Wednesday, Mar 26, 2014 at 09:54

Wednesday, Mar 26, 2014 at 09:54

John & Val,

Few models are actually computer controlled:

Nissan Navara D40, R51 Pathfinder 2011 onwards V6 Diesel only. Hyundai Santa Fe 2010 +, Range Rover 4 2011 +, Ford Ranger 2011 +, Pajero 2012 +, Mazda BT-50 2011 + and Land Rover Disco 4, Isuzu D-Max 2012.

The rest use either a conventional alternator or low voltage type.

Yes on computer controlled vehicles if the low charge function can't be turned off by the dealer then a DCDC charger is the way to go.

With regards to the low voltage type alternators Toyota etc fitting a booster diode where possible will restore voltages to near standard alternator levels.

As for charging batteries in a camper/small van, many including myself have no problems charging straight of the vehicle with no DCDC charger to be seen, in the case of a large van, with long cable runs or where inadequate cabling has been installed a DCDC charger might be the solution.

Frank P,
Sorry, yes did assume your were referring to a DCDC charger.

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Leigh

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Follow Up By: HKB Electronics - Wednesday, Mar 26, 2014 at 10:18

Wednesday, Mar 26, 2014 at 10:18

John & Val,

Forgot about alternator life, now that is a grey area, I have had long discussions with Bosch on this subject, the Bosch technical adviser stated, Bosch alternators are designed to run at 100% capacity indefinitely providing the alternator can shed its heat load. In fact they are very conservatively rated and he has found they can generally produce considerably more output than the max specified.

Of course the catch22 is "providing it can shed its heat load" ie car manufacturer has placed the alternator where it can get sufficient cool air flow.

For Nippondenso they suggest 75% max for continuous operation.

As temperatures start to increase you need to derate the alternator but at higher temperatures the alternator or DCDC charger will start reducing charging voltages so it tends to cancel out from a battery charging perspective, sticking to the 75% capacity would be a good idea.

Bottom line though, is not much good having high battery capacity and using a DCDC charger to limit the current if you can't replace the charge in a reasonable drive time, you would be better off putting in a bigger alternator.

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Reply By: Honky - Tuesday, Mar 25, 2014 at 17:37

Tuesday, Mar 25, 2014 at 17:37

This is my opinion and based on my experiences, I am far from an expert.
A dc to dc ( 20 amp ) charger is just to slow to get power back in to a depleted battery. Note that you would be still pulling most of the charge from a dcdc charger just running you equipment which means not much is charging your battery.
Good wiring from the alternator will put in a least 40 amps per hour. After the battery is about 80% than a dcdc and solar comes into its own and this is if you drive for long periods.
Even a solar set up that puts out say 20 amps per hour hour say for 6 hours? is going to be bulky and expensive.
I also would consider the 50 amp alternator quoted to be incorrect, specially if it is a 4wd.
Quickest replacement power is a petrol 12 volt charger of at least 55 amps as stated.
Next is heavy wiring direct from from alternator which should be at least 80 amps up.
Next is a small generator with a battery charge of at least 40 amps
Next is large solar array of at least 360 watts and plenty of sunshine
Next, if driving, dcdc and solar panels on roof.
Last is dcdc only.
I do have all the above and consider the cost as a lesson.

I have not factored in charging overload nor size of battery. An upgrade of battery should be considered but you still need to factor in the above.

With my system I need to increase the battery bank to say at least 200 amps ( currently running 120 ).

Honky

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