domestic solar

Dec 30, 2020
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hi i am a newby to P/C and i am about to fit solar to my elddis 550 we like to get lost to the world so going to fit 1 x 150 watt panel and a 20 amp MPPT controller, with the idea of fitting more panels when we find out how much is needed for pumps, led lighting, and a bit of telly, Another important part is storage, no room for a second battery.
So have been studding utube and have just finished building a 120 amph lithium battery with a bluetooth B M S so i can monitor on my phone. IMG_0763.JPG
 
Mar 14, 2005
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Hello Robbymax.

You will need to experiment to see how much power you will need, but just a few points you might find helpful, and please forgive me if you already know these considerations.

The energy used by any item based on a constant voltage (assumed 12V) will be proportional to the current rating of the item times the period of usage.

By checking the current consumption of each item, and working out how long they are actually used for, will give an indication of the amount of battery they will consume each day.

It can be quite surprising some items you might think will use a lot, actually use very little, and some you might think are economical, use considerably more than you might expect.

I have done this exercise a few times, and for our needs a daily usage of about 40Ah or less, but We didn't use a tv, and we usually used a electric hook up.

Historically other forum members have done what you are anticipating, and seem to manage with 150 to 200W of solar panel, so I don't think you're too far from the mark.
 
Dec 30, 2020
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thankyou Profjohnl started thinking about lithium when i bought the van but the price put me off, but when you learn that 100 amps means 100 amps to use
were 100 amps lead acid only means 50 amps, so when you can double capacity for the same size battery it made me think. A bit of research showed if you choose the right cells you can get 120 amph now that is a big difference so inspired me to make my own for a lot less money and it fascinated me.
 
Mar 14, 2005
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I have no doubt the battery capacity should be fine, as many people caravan with smaller (85Ah) batteries. But even Li-ion do eventually start to reduce their charge capacity with eth number of charging cycles and age. Also most of the EV manufacturers do not allow the car to use all the batteries total capacity, as deep discharges are more damaging, most seem to prevent power usage when the batteries discharge to about 15%. This prolongs the batteries integrity.

My concern is more a question of how you intend to keep it charged. If your using electric hook ups, then you can of course use a mains powered charger. If you were trying to keep the battery charged by solar panel alone, then a 150W panel should mange reasonably well, provided you can keep the panel in the well illuminated by daylight and preferably sunlight. This way most people could caravan for weeks without shortage of 12V power.

I am told you should not use a lead acid battery charger to recharge Li-ion cells. That means the caravans own charger is not suitable, and should be prevented from directly charging the LI-ion cells. Investigate getting a multi input solar charger through which either your solar panel and/or the caravans battery charger will safely recharge the battery.
 
Sep 26, 2018
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Most Lithium batteries designed for vehicles include charge adapting circuitry built in so that the battery can be used with conventional vehicle charging regimes...

I have experience of Lithium based batteries (mainly LiFePO4 for RC models) and they cannot recharge if they are absolutely flat...
 
Mar 14, 2005
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Most Lithium batteries designed for vehicles include charge adapting circuitry built in so that the battery can be used with conventional vehicle charging regimes...

I have experience of Lithium based batteries (mainly LiFePO4 for RC models) and they cannot recharge if they are absolutely flat...
If you read the OP you will see he has built the battery himself it is not a vehicle replacement battery and thus it may not have the circuitry you mention. It is certainly a matter he should investigate.
 
Dec 30, 2020
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lithium batteries are developing at a very fast rate. if you look at the picture i put up you can see a battery management system on the top, these devices make all the difference they cut the charge when full and dissconect when empty and these parameters can be set by yourself, because you monitor on your phone using bluetooth and the program, you can check capacity when ever you like.
and the charge cycles are 3000 plus using Lifep 4 cells and no maintainance
fit and forget
 
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Dec 30, 2020
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larry you mentioned about lithium batteries they have a bms and it shuts them off when flat and and sometimes they self discharge so the bms cant work so the only way to start charge is to get into them and by pass the bms once you get them started they will be ok
 

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