size of battery needed for my solar panel

[muckington]

Hi

I Have 120W solar panel im putting up soon in our caravan

I have 3 motion detector cameras to run off of it. Though there will not be much motion detected where the caravan is going. I plan to have the cameras switch on when I am away and switched off when I am there

I plan to stay in the caravan a couple of nights a week and when I am there I want to run upto 2X LED lights and the diesel night heater. The electronics of the heater run off of a 12 volt system and it has a glow plug which uses a hurendus amount of power to start the heater. I dont plan on watching any TV and I will bring my laptop from home which will be full charged!

I know day light is bad at this time of year but any ideas on battery type and size please?

Thanks

 

[big-all]

120w forget any heater you may get enough to get you perhaps 40-300 w a day or 3 to 22 amp at 12v during the winter assuming minimum to no losses so perhaps11amp average that may or may not be enough to give you 24hrs camera on a 30ah battery but forget heat as a non starter

 

[big-all]

i have a 60w panel on a day when you dont have to squint your eyes to find the sun following the sun around the sky at a near perfect varying angle may give 1to1.5amp at 18v total over the day [945-1400]and on a bright sunny day again following the sun accurately the best i have managed high summer was perhaps 25amp at 18v [via ryobi ]power brick and batteries [945 am -820pm]

as an aside via the same power brick the tv uses 12w and average i get 50-55 mins per amp at 18v so efficency about 55-60% but thats plugging a tv at mains voltage into a ryobi brick

Ryobi ONE+ Gen2 Power Inverter 150W 18V RY18BI150B-0 Tool Only

The Ryobi Gen2 Power Inverter charges or powers electronic and mobile devices in addition to you Ryobi ONE+ 18V batteries. The RY18BI150B 150W Power Inverter features a USB-C charging port, 2 USB-A charging ports and a wall plug for power on the go

www.direct-powertools.co.uk

 

[ericmark]

1 kW of solar panels, will give you around 66 kWh per month. Judging by mine in Mid-Wales.
To have a three kW item run, you need around 3.2 kWh of solar panels with a lithium (LiFePo4) battery.
So 120 watt will not be enough much at all, I have 6 kW on my house roof, so 120 watt is about enough to keep a lead acid battery from becoming discharged when the caravan is in storage, so you're really looking at a battery you can take somewhere to charge.

The lead acid battery can't be recharged in much less than 12 hours, it does not matter what size charger, the battery just will not accept a faster charge. So if you want it to charge faster, looking at lithium, my lithium batteries can charge in around 1.5 hours, so the big question is what is the largest item you want to run?

So the balance is weight against output.

most of the battery packs like shown, will connect to solar panels, a caravan kettle is around 1 kW some 750 W, so the cheaper of the two shown is 300 watt, same as the old lead acid I have, which was really got to jump start with, using the 230 volt output, the inverter must run, so it uses power even when item plugged in is not running, but for 12 volts, it uses nothing on stand-by, the lithium batteries are often a higher voltage, 55 volts are typical, so does not matter if using 5 volts, 12 volts or 230 volts the inverter has to run, so to have something auto switch on, you're using battery even when it has not switched on.

But if you want to put it in your car to either charge or take to be charged, weight matters, my lead acid is about as heavy as I would want to carry, and would not want to carry it far. The larger lithium is 21.6 kg, which is about the maximum one could transport. 23.8 lbs (10.8 kg) for a 1 kWh version.

I am lucky to see 1 kW from my 6 kW panels this time of year, so 120 watt looking at 20 watt or just over 1 amp. Or in watt/hours, around 100 watt/hours is all you can expect. I am judging this as a scale down on what I get with 6 kW panels.

 

[Harry Bloomfield]

The electronics of the heater run off of a 12 volt system and it has a glow plug which uses a hurendus amount of power to start the heater.

20w for a few minutes, until they ignite, then around 5w once running. What you are proposing, simply will not work, not enough input from the panel, during winter, and no where near enough storage, to see you through the night.

 

[ericmark]

Even with massive storage, the heater can be a problem, son with a narrow boat, engine running in the day, 350 Ah of lead acid batteries, and the heater failed before the morning. The alternators 2 x 60 amps, were voltage regulated, around 13.8 volt, so only producing around 5 to 10 amps after the first half hour of running.

What he needed was a stage or pulse charger, the shore charger was a stage charger, with solar we also have special chargers, which follow the best voltage to extract maximum power, the unit to do this, uses some energy, and also costs more than a simple zener diode, so the MPPT charger is only any help with arrays over a set size.

A fork lift, golf trolley, mobility scooter, the battery is not charged and used at the same time, so a simple stage charger works well, but a narrow boat or caravan, the battery is being used while it is being charged, so if a stage charger is set to change charge rate when the current drops to 4 amp, the lights could be drawing 4 amps, so battery is over charged. So it uses a pulse, and measures the decay time, to work out battery state of charge, this costs a lot more.

But all these different methods' means, a 500 watt solar panel will give a varying amount of charge depending on the control used. And my 6 kW panels have produced 1.9 kWh today, summer they can give me 39.5 kWh, this time of year I rely on the off-peak supply, recharging them overnight.

 

[Harry Bloomfield]

Wind generation, might be a little more reliable.

 

[muckington]

120w forget any heater you may get enough to get you perhaps 40-300 w a day or 3 to 22 amp at 12v during the winter assuming minimum to no losses so perhaps11amp average that may or may not be enough to give you 24hrs camera on a 30ah battery but forget heat as a non starter

Just to clarify what i said in the OP; it is a diesel heater. All that runs on electric is the fan, the glow plug and the the ECU

So you are saying that a 30amp/hr batter should run the cameras then?

 

[muckington]

1 kW of solar panels, will give you around 66 kWh per month. Judging by mine in Mid-Wales.
To have a three kW item run, you need around 3.2 kWh of solar panels with a lithium (LiFePo4) battery.
So 120 watt will not be enough much at all, I have 6 kW on my house roof, so 120 watt is about enough to keep a lead acid battery from becoming discharged when the caravan is in storage, so you're really looking at a battery you can take somewhere to charge.

so you are saying that i dont have enough solar panel for my cameras regardless of battery size?

 

[muckington]

20w for a few minutes, until they ignite, then around 5w once running. What you are proposing, simply will not work, not enough input from the panel, during winter, and no where near enough storage, to see you through the night.

So how many 120W pannels do you think I need then? what size of battery too?
A wet day say at this time of year. How long do you think it would take to charge say 110amp/hr battery up from 50% to 100% full?

 

[muckington]

A fork lift, golf trolley, mobility scooter, the battery is not charged and used at the same time, so a simple stage charger works well, but a narrow boat or caravan, the battery is being used while it is being charged, so if a stage charger is set to change charge rate when the current drops to 4 amp, the lights could be drawing 4 amps, so battery is over charged. So it uses a pulse, and measures the decay time, to work out battery state of charge, this costs a lot more.

Do you think there is much chance of thermol-over-load and the battery catching fire from it being over charged from my 120W panel

 

[muckington]

Wind generation, might be a little more reliable.

where would you but something like that?

 

[Harry Bloomfield]

where would you but something like that?

A wind generator shop?

 

[big-all]

Just to clarify what i said in the OP; it is a diesel heater. All that runs on electric is the fan, the glow plug and the the ECU

So you are saying that a 30amp/hr batter should run the cameras then?

no way off knowing without knowing what is consumed and what is generated but probably close to zero chance without perhaps a battery charged from the mains perhaps once a week to make sure ??
do you live near by ??
if so 2 batteries one on the solar and another charged at home and changed every few days

 

[Harry Bloomfield]

Do you think there is much chance of thermol-over-load and the battery catching fire from it being over charged from my 120W panel

It, like all such system, will need a charge controller. You need to learn some basic maths, to be able to calculate how long a battery might last, and how long it might take to charge up.