Battery consumption

[Iain55]

I'm looking for some advice regarding my batteries.
I'm going off on a 65 day trip, probably 20 days off grid (1 or 2 nights each time off grid)
Trying to work out what's ok or not.

My batteries (2 x 100aH lead acid) in 3 hours went from 12.60 to 11.98 volts (went on to EHU at that point)
I was running my 21' TV (not sure of amps/watts), diesel heater (6 amps), 16w overhead light, 5w LED lamp and charging my iPhone and iPad.

My solar panel at home seems to keep the battery over 13.5 volts during the day and drops back to 12.9 volts at night.
Nothing running.

Does this seem ok ? Just needing reassurance or advice

 

[molly 2]

Heater seems high at 6 amps .? On low should drop down to about 1 amp

 

[r4dent]

I was running my 21' TV (not sure of amps/watts), diesel heater (6 amps), 16w overhead light, 5w LED lamp and charging my iPhone and iPad.

Most 12v TV draw around 5 amp; Heater = 6 amp; Lights and chargers will be around 2 amp
Total draw about 13 amp.

My batteries (2 x 100aH lead acid)

In practice, 2 x 100 ah batteries (nominal) will give a total of 100 ah (50% of nominal) before going from 100% to flat.
This assumes batteries are in good condition and well maintained.
So 100 ah at 6 amps will give 16 hours before needing charging.
So 2 days should be OK, but 4 days will be pushing the envelope.

Don't forget that there are a lot of "hidden" users of 12v that people tend to ignore. These include TV amplifiers; Clocks / Control panels; control boards in heating and fridges.

The batteries will be recharged in three ways.
a) EHU - If you are on EHU on the days when you are not off grid then the charger will probably get them back to 100%.
b) Driving- If you drive 100 miles between stops then this will put a significant amount of charge in the batteries, if you drive 20 miles this will just about replace the amount you used starting the engine.
c) Solar - Depends on how big the panel is / where you are further South the better / when you go. More in summer, less in winter / where you park (not a lot of solar in the shade).

This table gives an idea of what a 150w panel will supply.

The voltage serves as an indication of the charge state.

You asked an "how long is a piece of string?" question. Hope this helps you with your plans.

 

[Iain55]

Most 12v TV draw around 5 amp; Heater = 6 amp; Lights and chargers will be around 2 amp
Total draw about 13 amp.


In practice, 2 x 100 ah batteries (nominal) will give a total of 100 ah (50% of nominal) before going from 100% to flat.
This assumes batteries are in good condition and well maintained.
So 100 ah at 6 amps will give 16 hours before needing charging.
So 2 days should be OK, but 4 days will be pushing the envelope.

Don't forget that there are a lot of "hidden" users of 12v that people tend to ignore. These include TV amplifiers; Clocks / Control panels; control boards in heating and fridges.

The batteries will be recharged in three ways.
a) EHU - If you are on EHU on the days when you are not off grid then the charger will probably get them back to 100%.
b) Driving- If you drive 100 miles between stops then this will put a significant amount of charge in the batteries, if you drive 20 miles this will just about replace the amount you used starting the engine.
c) Solar - Depends on how big the panel is / where you are further South the better / when you go. More in summer, less in winter / where you park (not a lot of solar in the shade).

This table gives an idea of what a 150w panel will supply.
View attachment 107313
The voltage serves as an indication of the charge state.

View attachment 107315

You asked an "how long is a piece of string?" question. Hope this helps you with your plans.

Thank you, this is very helpful. I'm think we should be ok, just a bit paranoid

 

[Iain55]

Heater seems high at 6 amps .? On low should drop down to about 1 amp

To be fair that was a guess based on a google search, thanks.
I'm trying to build an understanding of what's what.
By batteries went flat, down to 10.90 volts a few weeks back, however I suspect I left something on over night.
It's never happened before and it has shaken my confidence a bit.

 

[wildebus]

1-2 nights off grid at a time .... So sounds like you be at a campsite overnight between those times, and that will give you a full charge by the morning I would expect. So main focus is can you manage 2 nights and a full day between on the batteries.
200Ah of Batteries with Solar assistance should really be easily sufficient for that if you have a Gas powered Fridge
Your voltage drop would indicate, if your batteries really are still at 100Ah capacity still, you have pulled 100AH in 3 hours - 33Ah/Hour. That is pretty unlikely.

It sounds like your batteries are not that great anymore to be honest, but if it were me, I would initially get a Battery State of Charge Monitor such as a Victron BMV or SmartShunt. This will tell you the actual Amperage use at any given time and also the Amp-Hours drawn over a period of time. THis will also come in very useful during your trip.
Make a note of the starting point, use you van for a few hours in a typical way and then see what the AHs drawn is. That will give you an idea of how much power you need for your style of "camping". What one person needs is not the same as another, so it is hard to say you need X or Y amount of Battery Capacity.

 

[Iain55]

1-2 nights off grid at a time .... So sounds like you be at a campsite overnight between those times, and that will give you a full charge by the morning I would expect. So main focus is can you manage 2 nights and a full day between on the batteries.
200Ah of Batteries with Solar assistance should really be easily sufficient for that if you have a Gas powered Fridge
Your voltage drop would indicate, if your batteries really are still at 100Ah capacity still, you have pulled 100AH in 3 hours - 33Ah/Hour. That is pretty unlikely.

It sounds like your batteries are not that great anymore to be honest, but if it were me, I would initially get a Battery State of Charge Monitor such as a Victron BMV or SmartShunt. This will tell you the actual Amperage use at any given time and also the Amp-Hours drawn over a period of time. THis will also come in very useful during your trip.
Make a note of the starting point, use you van for a few hours in a typical way and then see what the AHs drawn is. That will give you an idea of how much power you need for your style of "camping". What one person needs is not the same as another, so it is hard to say you need X or Y amount of Battery Capacity.

Thanks, again very helpful.
I have a gas fridge. My batteries are 3 years old and I have suspected they are not putting out as much as they were, but its difficult to gauge.
I think I will invest in a monitor device

 

[Derekoak]

1-2 nights off grid at a time .... So sounds like you be at a campsite overnight between those times, and that will give you a full charge by the morning I would expect. So main focus is can you manage 2 nights and a full day between on the batteries.
200Ah of Batteries with Solar assistance should really be easily sufficient for that if you have a Gas powered Fridge
Your voltage drop would indicate, if your batteries really are still at 100Ah capacity still, you have pulled 100AH in 3 hours - 33Ah/Hour. That is pretty unlikely.

It sounds like your batteries are not that great anymore to be honest, but if it were me, I would initially get a Battery State of Charge Monitor such as a Victron BMV or SmartShunt. This will tell you the actual Amperage use at any given time and also the Amp-Hours drawn over a period of time. THis will also come in very useful during your trip.
Make a note of the starting point, use you van for a few hours in a typical way and then see what the AHs drawn is. That will give you an idea of how much power you need for your style of "camping". What one person needs is not the same as another, so it is hard to say you need X or Y amount of Battery Capacity.

That sounds a lot of money you are suggesting Ian spends to monitior battery use. You suggested to me a reasonably cheap clamp meter that is a useful meter for lots of of other things and you can see the current going through any wire you can get the clamp round, so a test of the running amp value of the heater and the lights and the TV. Add up the running hours of each device times its cuurent and save the money for something like new batteries. I am pretty sure Ian would find his batteries need replacing.
Ian it is a gamble I might be wrong but it feels like your batteries are the issue, a clamp meter and some sums would clarify the issue for less initial layout.

 

[trevskoda]

Rule of thumb is 100w solar for every 100ah of battery, the voltage input seems low and should peak at 14.4 before dropping back to a float of 13.7 ish, do you have a mppt solar regulator or an old pwm, if so dump it.

 

[r4dent]

Rule of thumb is 100w solar for every 100ah of battery.

Not a bad rule of thumb for when the sun shines, (April - Sept).

A 100w solar in Aberdeen in December would take around 2 weeks to produce 50 ah to recharge a flat 100 ah battery.

 

[witzend]

Money better spent replacing battery's should improve things at 3 yrs old you'll need to be replacing them soon anyway

 

[wildebus]

Thanks, again very helpful.
I have a gas fridge. My batteries are 3 years old and I have suspected they are not putting out as much as they were, but its difficult to gauge.
I think I will invest in a monitor device

The other thing which is worth looking at is the Charging Systems. A lot of standard fitment chargers are quite dated and inefficient in how they work.
It is not uncommon for people to replace problem batteries and find the new ones don't work as well as they hoped as they are not getting a full charge.

Battery Monitor will keep an eye on discharge rates and help ensure you don't take the batteries too low. Essential for longer service life.
Correct Charging will ensure that you are getting a full charge into the battery and maximizing the available charge. Of the three chargers you will have - Mains, Solar and Split-Charge, you only really need one of those to be a Smart charger. For your described trip of 60 days with max 1-2 off-grid at any on time, I would go for a smart mains charger if you don't have one already so you will start each day on a campsite day with fully charged batteries.

 

[trevskoda]

Yep I dumped the caravan type charger for a numax all sing and dance smart charger.

 

[1 Cup]

This is optional if not keeping van
If over the water, sounds like you could get lead acid batteries cheaper when there.
Just run them to there done. Then buy new out there. Do some research befor you go.. on batteries shop and get clamp meter, With DC amps .

 

[REC]

Thanks, again very helpful.
I have a gas fridge. My batteries are 3 years old and I have suspected they are not putting out as much as they were, but its difficult to gauge.
I think I will invest in a monitor device

You said the batteries were very low on one overnight, you may have finished them as they are three years old too?

 

[Stanski]

Hello Iain55,
When are you going on you travels?
Where do live in the country?
What route in Europe you're taking?

I ask as I am about to return to UK, via Dover, have 2 110Ah batteries, that have worked with 180W solar, only 1 night Elec as it was paid for, for 50+ days.

If you want to borrow them, we could meet up and swop batteries, I have a second set back home to use while in UK.

I can use your batteries whilst in UK and tell you if they are weak.