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

i used 80 32650 cells 6 amph
 
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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.
 
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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.
 
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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.
 
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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...
 
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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.
 
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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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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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We've just bought a hugely expensive lithium battery. It's a Lifos 68ah.
When it arrived it was showing 50% discharged but still put out 13.7v at the terminals. This is entirely different to a lead acid battery which would put out around 12.2v if it were taken down by 50%.
We've charged up the Lifos now and have installed it in the caravan. But I'm now wondering how does the caravan charger deal with this battery? I'm thinking it's not going to charge the Lifos as it thinks it's already at capacity, even when it's actually down to 50%?
 
Nov 11, 2009
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We've just bought a hugely expensive lithium battery. It's a Lifos 68ah.
When it arrived it was showing 50% discharged but still put out 13.7v at the terminals. This is entirely different to a lead acid battery which would put out around 12.2v if it were taken down by 50%.
We've charged up the Lifos now and have installed it in the caravan. But I'm now wondering how does the caravan charger deal with this battery? I'm thinking it's not going to charge the Lifos as it thinks it's already at capacity, even when it's actually down to 50%?
Don’t lithium require 14.6 v for a full charge and I guess it depends on your power supply unit specification and battery management system. Didnt you talk to the supplier of the battery first in case you need additional fitment. Road pro have a good guide on their website.
 
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Don’t lithium require 14.6 v for a full charge and I guess it depends on your power supply unit specification and battery management system. Didnt you talk to the supplier of the battery first in case you need additional fitment. Road pro have a good guide on their website.
Yes. Spoke to Lifos first. They assured me that no additional equipment would be required and that any charger would be able to charge the battery due to its smart battery management electronics. I'm just trying to understand how it all works.
 
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Because the charging curve is very flat on lifepo4 cells between 10%and 90% it is not possible for Lead acid battery chargers to see the need to charge because it always looks fully charged, lithium charges need only 14-6 volts cc charge now the BMS will monitor the battery and when the battery reaches full it will rapidly rise and when it reaches the set voltage it will cut the charge to the battery same at the bottom end down to a preset minimum which you set yourself not down to dead flat not right to the top you choose the capacity that you consider safe for the battery and this i do on my iphone using the bluetooth APP
supplyed by the BMS manufacturers. now to tweak the onboard charger is the next thing to sort there will be a trimming pot in side and you should be able to set the charge voltage higher but i havent looked yet i will keep you posted
 
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Our Truma solar panel controller has the option for Gel, AGM or Liquid. Not sure if the solar panel controller can recharge a Lithium battery.
BTW what is the weight saving using a Lithium battery that is the equivalent of a 100ah AGM battery?
 
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Our Truma solar panel controller has the option for Gel, AGM or Liquid. Not sure if the solar panel controller can recharge a Lithium battery.
BTW what is the weight saving using a Lithium battery that is the equivalent of a 100ah AGM battery?
The lithium battery suppliers give weights. A 100 lead acid can be variable depending on quality but around 22-26kg.

https://www.outandaboutlive.co.uk/c...lithium-leisure-batteries-a-caravanners-guide

Spot the error in the link above👎

 
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Reading
Lithium leisure battery challenges

  • Lead acid batteries automatically balance the cells, but lithium batteries do not, and cells that are subjected to too much voltage can fail. This can be a problem when using solar panels with charge controllers. It’s important that lithium batteries for leisure use come with an in-built battery management system (BMS), as cell balancing is one function it should perform. Also, lithium batteries should not be charged in temperatures below 0°C, as this may result in permanent damage. It's the role of the integral BMS to prevent damage through issues such as those raised above.
  • The electronics needed are complex and inevitably add to the cost, especially for the more comprehensive types. For example, cold weather charging can be facilitated by employing internal heaters to automatically warm the battery first. Of course, while this may be fine in some situations, it’s clearly less than ideal when caravanning off grid. The bottom line here is that, under load, a fully charged lithium battery will outperform a similar- capacity lead acid one any day; the challenge is in ensuring the full charge in the first place.
The above about "balancing cells" is enough to put us off purchasing one for the caravan even if we could afford to buy one.
 
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Lithium leisure battery challenges

  • Lead acid batteries automatically balance the cells, but lithium batteries do not, and cells that are subjected to too much voltage can fail. This can be a problem when using solar panels with charge controllers. It’s important that lithium batteries for leisure use come with an in-built battery management system (BMS), as cell balancing is one function it should perform. Also, lithium batteries should not be charged in temperatures below 0°C, as this may result in permanent damage. It's the role of the integral BMS to prevent damage through issues such as those raised above.
  • The electronics needed are complex and inevitably add to the cost, especially for the more comprehensive types. For example, cold weather charging can be facilitated by employing internal heaters to automatically warm the battery first. Of course, while this may be fine in some situations, it’s clearly less than ideal when caravanning off grid. The bottom line here is that, under load, a fully charged lithium battery will outperform a similar- capacity lead acid one any day; the challenge is in ensuring the full charge in the first place.
The above about "balancing cells" is enough to put us off purchasing one for the caravan even if we could afford to buy one.
If you saw the journey of Euan McGregor and Charlie Borman starting in Patagonia it was a real problem charging the motorcycle batteries in sub zero temperature and eventually they were wheeled indoors overnight for charging.
Perhaps a form of battery heating is used in EV cars but not leisure lithium batteries.
 
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i started building lithium batteries about a year ago and what a interesting project this has been and to date i have done 10 batteries i got started on Youtube and bought off the shelf modem replacment packs never used 2 years old £1-80 a pack so i bought a 100 packs giving me 400 18650 cells and i built a 48 volt 60 amph battery to help with my solar system on my house, one of my battery banks a converted forklift battery was knackered, but i got 4 years out of it. Opening the packs was a challenge they were glued together but i found when they are cold a smack along the seam and they open and you have got 4 cells, charge them to 4-2 volts and let them stand, out of 400 there were 4 duds 4 that lost voltage, the rest all usable. If you are interested i will tell you more
 
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Interesting-this is how Nissan house batteries are made-using recycled car batteries isn't going to be an issue as it's starting already! And things will ramp up. The batteries on our Mini have a complex heating and cooling system built in-you can precondition the car which also conditions the batteries so you're warmed up ready to go in the winter on the mains and don't lose so much range-a major issue is less range in the winter-mind only seems to be 10 miles or so on ours so far.
Clive is quite right about charging on the long way up-there was a lack of infrastructure too so some cold clime charging visits had systems whereby the house had to be switched off before enough current was given to charge the bikes! It was so interesting and very brave of both Rivian and Harley to use prototypes to make a programme-and refreshing-great advert if it went well-could be the death nell if it had been a disaster-we were suitably impressed. The Harley is a bit more expensive than our Mini EV and has the same range!!!!! So it isn't cheap but is getting rave reviews-Bike mag even called it the best Harley made, and even liked the noise-me too-sounded they said like a cross between a Federation Tai fighter and a ... ..can't remember-sorry! Be some while before the bikers get round to adopting though as many think the point of the bike is the engine-me-would absolutely love one-when I win the lottery I'll have one!!!!
 
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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...
 
Dec 30, 2020
21
6
515
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hi there is a way to recharge you have to bypas the BMS and go straight to pos and neg then the BMS will come back on and you can charge as normal
 

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