Confusing battery levels (readings)

[BernieQ2]

Hi Dot I did query your need for that extra portable fridge.
WE have no need for one. Not possible to cook enough meals for a 6 month trip ?.
Even without the extra one I was struggling with my battery's while in Vic. I have 480amp hr and 600w of solar and they only have the fridge and occasional TV use .
All light are LED .
Bernie.

[Dot]

G has been doing his calculations for the battery draw in the bus for your perusal.
Lights (interior)............ 4amps pr day @ 4 hrs usage
TV............................ between 7 - 10 amps approx. 3 hrs pr day
Bushman fridge/freezer...15 - 20amps at - 10 deg This is the TOTAL amps pr day (measured with the boss's 12v monitor)
PC (when in use)'......... 4 amps 3-4 hrs pr day As above, used the 240v monitor
Inverter ?? had no real usage for the inverter but do switch it off when not required.
Solar IN varies from a sunny summer day of 140amps daily down to a cloudy day to about 30 amps.
The battery capacity is rated at 540ah.


G also picked up the two new batteries today. 2 x 270ah... B4 you start on "why didn't you go Lith"? well we would have IF we had time to set it up because we know nothing of how what to do to even start.

4 amps per day, oldtrack would be having a coronary if he reads this 4 amps pr day is not much at all???
I'm guessing this is 4 amps instantaneous so if used for 1 hr constant it would consume 4 Ah, x 4 hrs = 16Ah per 24hrs
TV 10Ah x 3 hrs = 30Ah
Bushman... this one is tricky, it may use 20 amps when it is running, but it doesn't run at that load constantly, so the duty cycle will tell us how long it is on compared to off. A wild guess, 60% duty cycle = 14.4hrs x 20 amps = 228Ah... that is a lot, so the duty cycle is required. A 200ltr fridge freezer uses 80Ah to 100Ah @ 12v per 24hrs, so if we use that figure, 100Ah
PC 16Ah Because we used the monitor (12v) over 24 hrs this was the monitors reading for 24 hrs.

16Ah + 30Ah + 100Ah = 16Ah = 162Ah. 2 x 270Ah of AGM will give 270Ah at a C20 draw down rate to the 50% SOC where AGM batteries are safe to discharge. The reasonably low output for amp hrs would be covered by either plugging into power or starting the genny or running the bus IF solar was insufficient.
Now it gets even more tricky, if you want to get the 270Ah you can not take out more than a C20 rate, in this case 540 divided by 20 = 27 amps, your draw looks to be around 38 amps, so you may only get 200Ah and not the 270Ah you are expecting.
All thing added together, you have 38Ah left after 24 hrs with no solar like an over cast or rainy day, then you will need to run the generator for a min 12hrs to return the battery to more than 95% SOC, or plug into mains power. At best you will recover 140Ah, but more likely 120Ah at best as the battery will not accept the full charging rate after around 70% to 80% SOC, then the amps taper off to control over voltage damaging the battery, and you are still short 42Ah each day.
You need more/better battery capacity and more solar if you want to use that much power... and you mentioned an inverter as well.......what can I say....

If you look at the extra you have added on eg pc & bushman usage this inflates the amp hrs used daily, however as this is not the case the battery management strategies should cope. Just a note that we have managed with the 2 x 200ah aged batteries prev.
Yo Bernie,
I guess the need for things is a personal one, what one doesn't need the other might. Personally I like to take food already done if poss and meat that I know is good quality and price so I start gathering some time before departure. I would have expected your 600 solar to perform better than it has been even if in overcast weather, are you sure they are all connected? (like Chucks) Do you take your home brew with you on your trips or buy on the go stuff?
Martin , it was the time factor as well, there is only a certain amount of time that the G man can spread himself over for our requirements and the other things he gets called upon to do. next time

[Chuck]

Ummm...

Well...

Maybe...

Kinda...

[T1 Terry]

I made my calculation by guestimating what the actual information offered really meant.... me thinks I didn't interpret the information correctly
May I suggest the purchase of one of these units http://www.ebay.com.au/itm/LCD-Digital- ... 339841fdac and plug each device in separately for a day (24hrs) and measure just how much it uses, then post those figures and the information might be a little closer to being useful

[BruceS]

er ... that's the unit I lent G. I'm guessing he never had time to leave it connected.
I'll see if I can get time to visit them & give more detailed instructions.
Couple of visits to Queen Eliz Hospital coming up this week so my bum might be a little busy.... literally!!

[Dot]

Lights not needed to be done for 24 hrs
TV done while in use
PC also done while in use
The bushman was in use for the exact 24 hrs while testing
So G believes the readings were accurate.
.

[T1 Terry]

Lights not needed to be done for 24 hrs
TV done while in use
PC also done while in use
The bushman was in use for the exact 24 hrs while testing
So G believes the readings were accurate.
.

OK, well the numbers given are meaningless to me so I'll pass the batten on to someone else
The only way I know how to calculate it by a 24hr usage figure and that would require 24 hrs measurement to get an accurate figure. Amps is an instantaneous measurement, Ah is an average of the instant amps use over a 1hr period, so measured for 24hrs would tell you how many Ah battery storage would be required to power the total load for 24 hrs and how many watts of solar would be required to replace that many Ah in the 3 peak sun hrs available in winter from flat mounted solar panels

[Dot]

Does this mean this has stumped you at last

[T1 Terry]

Does this mean this has stumped you at last

You already have a long history of that Dottie, it started with a whisper around a campfire as I remember it

[Dot]

Just make sure you get to the Qld gathering .