Gday all

I did a little experiment with my inverter yesterday. I have a coffee machine that draws 5amps AC, two 100AH AGM batteries and a 100W solar panel.

I turned the mains off and ran on batteries. inverter did the trick but my voltmeter told me the batteries were down to 11.8 volts under sustained load, had a nice coffee BTW, interesting they recovered (it seemed) on the solar to 13 volts, however when I put the 240 back on the batteries started to draw 20 amps fully charged in 30 mins. I suspect I used the surface charge with my coffee.

Now, not knowing a lot about AGM batteries (I was bought up on lead acid and NiCads) and the batteries being 3 years old, I suspect a problem, I also suspect I was drawing around 50 amps from the batteries?????

Would appreciate an opinion or two. Cheers

Hi Phil,

Not sure what the question is but here are a few answers;

If the coffee mc draws 5 A at 240 v then in round figures it will be drawing 100 A at 12V. How long for ?

The recharging put back 20a for 30 mins so that is 10 ahrs. so was the coffee mc on for 6 minutes (.1 hr). EG 0.1 hr x 100 a = 10ahrs.

I guess the solar was not doing much at the time or ? 100W is about 6-7a at charging volts depending on things.

Jaahn

-- Edited by Jaahn on Sunday 28th of February 2016 11:53:37 AM

Jaahn types faster than me.... Graphic Artist, not a typist and I need to think due to CRAFT disease (my excuse if my calculations are off).

He's my take on this and doesn't fully take into account what extra power the inverter will consume to generate 230 Volts AC and as Jaahn says we don't know how long you ran the inverter for, so my calculations...

230 Volts * 5 Amps = 1150 Watts
Lets say you ran the Coffee Machine for 10 minutes ????
So, 1150 / 60 minutes = 19.16 Lets round that to 20 Watts per minute to allow something for the inverter.
20 * 10 = 200 Watts   then 200 / 12volts = 16.67 Amps off the battery capacity in 10 minutes
In my book that's a heavy load off your battery bank.

2 * 100 Amp batteries gives you 100 Amps usable power depending on what lower level you prescribe to.

So this draw is almost one fifth of power available in 10 minutes.

When batteries are drawing a heavy load they will show a lower voltage. Then when the draw is off they will stabilise and show the actual voltage and that can take some time.
Personally I think you need bigger batteries and lots more solar..... but that's another issue.

Hi Phil,

In a word (well several !) not enough solar for free camping.

To put up some perpective , if your 240v charger can put out 20amp and do it for 24 hrs then a solar panel which puts out 7amps max for ~ 8 hrs (some of that at much less amps) will not be any comparison. Compare 480Ahr against say 56 ahrs !! see the problem.

You must have some other form of charging !

Jaahn 

Jaahn wrote:

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Hi Phil,

In a word (well several !) not enough solar for free camping.

To put up some perpective , if your 240v charger can put out 20amp and do it for 24 hrs then a solar panel which puts out 7amps max for ~ 8 hrs (some of that at much less amps) will not be any comparison. Compare 480Ahr against say 56 ahrs !! see the problem.

You must have some other form of charging !

Jaahn 

-- Edited by Jaahn on Sunday 28th of February 2016 01:52:16 PM

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 Yeah I agree Jaahn, we are investing in another 100W panel in a few months time. Last lot of free camping we did was in bright sunshine and the batts did well on the solar. Mind you we had a few caravan park stops as well so not a real good test.

Should be interesting this Perth trip, will test out the batts and the solar.

Hope you are well mate...

why would you be using 20amps for 24hrs? 

grahamg wrote:

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why would you be using 20amps for 24hrs? 

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 I Think Jaahn was telling us that the charger (hooked up to the 240) has enough to supply 20 amps all day. We have a generator as well that will cool us on a hot day and charge the batts if needed. 

Cheers

-- Edited by Phil C on Monday 29th of February 2016 12:18:06 PM

After 30 yrs using Wet Lead Acid Deep Cycle and AGM's we Upgraded to Lithiums in Oct 2014 and there is No way I will ever go back to Leads.

What you worry about with Power Draw was what I used to do also but now use anything 240volt through the 2000 watt PSW Inverter and the Packs Do Not know what's happened and ReCharge from Solar twice as fast as Leads if not quicker on most days. Especially as we are Full Timers and Freedom Camp 80% of the time.

Cheers Kev.

Hi

Yes that is all good and true I am sure, however the cost is high. There are some setup changes to do for the controllers etc too. Would you like to indicate the cost and other changes done.

The fact is they run at a slightly higher voltage so the 12v items work very well. They have very low internal resistance so they discharge with little voltage drop and charge more easily with little voltage rise. The weight is much lower. Perfection but !! Give us the other side.

Jaahn

Jaahn 

Phil, your inverter would be drawing over 120 A whilst the coffee maker was working flat out. Providing you keep that within sensible limits (time) all will be OK.

If you wish to get a better indications of what is happening to your batteries then next time disconnect your solar panels before the test. Don't reconnect your panels or switch the power on for an hour or three. Keep an eye on the battery voltage and when you see that the recovery has ceased that will give you an indication of what amount of charge has been used (use the appropriate charge/voltage graph for your battery.)

 KevKim37 wrote:

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After 30 yrs using Wet Lead Acid Deep Cycle and AGM's we Upgraded to Lithiums in Oct 2014 and there is No way I will ever go back to Leads.

What you worry about with Power Draw was what I used to do also but now use anything 240volt through the 2000 watt PSW Inverter and the Packs Do Not know what's happened and ReCharge from Solar twice as fast as Leads if not quicker on most days. Especially as we are Full Timers and Freedom Camp 80% of the time.

Cheers Kev.

---

 "ReCharge from Solar twice as fast as Leads if not quicker on most days. "

Perhaps you should explain how that occurs??

La battery charge/discharge efficiency is usually in the 70 to 80% range

but decreases with age

While LIs do accept a higher  charge rates,  the  time will be dependent on solar panel specs   & solar regulator type /Specs, 

What are THOSE specs?

oldtrack123 wrote:

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HI Phil
While not downgrading the advantages of LiFePo batteries, you would understand that their charge /discharge efficiency ,whiles quite high ,, like every thing electrical cannot be 100% efficient.
That simply means you HAVE to put back in more than you take out!!!!
If you take out a 100Ahrs per day ,you have to put back 100Ahrs PLUS
Many Li enthusiasts post " That they can run "Everything"" but seem to not indicate their available recharging power

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 Gday PeterQ

One day I will change up to LI but the wallet will need some fattening up first and our hunger for cruising will need to stop as well.  Im probably wrong with my DC current, you suggest 120A, now that tells me I have a crackerjack set of batts which is happy time.

We just had a night of free camp, lights, water pump (2 showers) TV etc. Batts did well and held onto 12.9VDC. Next day the solar put it up to 13.2VDC, so Im pretty happy.

We are in Penong today and on our way to 3 free camps back to back. This will be a sure test for all the electrical systems on board although I suspect the gen will need to do some work as heavy rain is predicted.

Hope you are well mate, cheers

PeterD wrote:

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Phil, your inverter would be drawing over 120 A whilst the coffee maker was working flat out. Providing you keep that within sensible limits (time) all will be OK.

If you wish to get a better indications of what is happening to your batteries then next time disconnect your solar panels before the test. Don't reconnect your panels or switch the power on for an hour or three. Keep an eye on the battery voltage and when you see that the recovery has ceased that will give you an indication of what amount of charge has been used (use the appropriate charge/voltage graph for your battery.)

---

 Gday PeterD

Did that last nigh, batt recovered (at midnight) to 12.7VDC so I guess they are in the pink.

Hope you are well, cheers

As I have the same 610 watts of Solar/PL40 as before the upgrade and using the previous AGM's for 5 yrs I can say that the AGM'S  would be still Float Charging on Similar days at 3 to 4 pm  to achieve 100% Charge whereas the Lithiums using the same amount if Not More Power since the using of Coffee pod machine, Hot Water element, Induction Cooktop (never used before on Leads) will be fully Charged by Noon to 1 pm. 

I Know there is a lot of "Hoo Haa" goes on between others regards to Battery Types but I can say from past experience of Lead Acid Deep Cycle's/AGM's over 30 yrs of Camping/Caravanning with Solar and Generators that I Know that the Best Change I have Ever made for Full Time Vanning was to LITHIUM'S and the other half knows the difference from the way everything operates now compared to before. No Worries at all now as we use way More Power now than previously with No Hassles.

We Love Those Lithiums..

Hi,

We still haven't got an answer to HOW MUCH ?

Jaahn

Jaahn if it's the price your asking about I didn't mentioned as there was no question about $.

Our 500 Ah  Winston Thundersky Strapped, including connecting bars, Balanced and freight with a one Cell Battery Charger for Balancing if needed (still haven't had to use this)

1. 100Ah for the Ute Aux. Including one Relativity.(Balancing module).

2. 2 x 200 Ah packs. Including 2 x Relativities. 

3. Junsi Cell Loggers x 3 approx $23 each.

Total Cost $3,500 and on our way south we called in at Kuttabul to fit the 2nd 200Ah  pack which Trevor helped me wire up and fit for no extra charge.

I have since purchased from Hobbyking a Digital Signal Remote Battery Monitor for $125 so I can keep an eye on the Cell Voltages while mobile with the ABR Sidewinder DC-DC Charger running in Winter time down the southern states when the Sun Power is poorly.

Cheers Kev.

HI Kim & Kev

I am not knocking Lithium [Li Fe Po4] batteries

They have many advantages, including:

light weight

Ability to take a fast charge, IF the power is available

More efficient [fewer losses in both charging & discharging] about 95% compared to LAs at about  70%[when in good condition]

, more stable voltage 

But you can NEVER get out more than you put in

If the LAs are float charging, THEY ARE FULLY CHARGED!
That simply means they ARE fully charged as soon as the regulator goes into "FLOAT MODE".

So as I mentioned before that the Leads were still in Float at 4pm the PL40 was also only reading approx 96% SOC. Whereas the Lifes at 1pm are switched off at 100% SOC on the PL40. I do agree that you need to put more back than used but I have never said that I use more than is put back.

It's a Real Paradigm change as all New Technology can be and there is always something new in the pipeline. But for what I wanted and have achieved I am glad we fitted them. 

As we have been sitting under trees at Boddington RV Stop for 2 days to keep cool is something I would have never done before with the Leads and also using the Extra 240 volt appliances. 

I only use the Gene for 40+ days otherwise it has been in Hibernation since Oct 2014. Total fuel usage for Honda 12 litres over 3 days. I am still to have the AC wired to run of the Inverter.

Cheers Kev.

Hi Kev
Once the solar reg switched to" float ", the LA battery would be very unlikely to EVER get fully charged
Perhaps the problem lay with the regulator settings or voltage sensing point.[switching prematurely from BOOST charge ???]
Did it take the LAs up to 14.5V/14.8V before switching to "float" ?

The Lis do not require as high a voltage to fully charge as Las.