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14.7v lithium battery in a 12v system?


Andrew-clark

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I am currently converting a van to a family camper, and have got to planning the electrics. I was planning a 12v system charged from the van and from a solar panel. It will run a small 12v compressor fridge, led lights, some USB charging ports and a diesel heater. I plan to avoid using an inverter for now.

 

I have been offered some used, but good condition, 14.7v 46Ah lithium batteries which were surplus to requirements elsewhere.

 

My question is whether it is possible to incorporate such a battery into a 12v setup? If so, are there any addition parts required to run the system safely?

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Hello Andrew, I know very little about the technical details of lithium systems but my motorhome is presently with a company that is replacing the original (standard) 12v leisure battery system with a lithium based system - two 110ah batteries linked to my solar panel. The batteries are just one part of the system and the rest includes a 12-12dc bluetooth smart charger for the alternator, bluetooth smart battery monitoring system, bluetooth smart battery protect system, smart solar MPPT regulator.

 

These additional items are not just to run the system safely but to get the best out of the lithium batteries. The additional elements have added a further £1000 plus VAT. As I am not capable of installing the system myself I will also have labour costs on top of this. It is a considerable investment but the immediate and long term benefits certainly justify the costs for me.

 

There are some sources that would say that a lithium battery can simply be slotted in place of the existing 12v leisure battery but I don't believe that is the case. I do know someone who can give you the technical background to what you would need if you PM me I will give you the details.

 

Good luck with the conversion.

David

 

 

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Yes, you can use 14.7V batteries in a nominal 12V system. But doing so without knowing much about specifics of lithium batteries and designing the system around them, is a recipe for trouble. There is so much clueless, cringeworthy electric work on #vanlife #selfbuild videos on YT, even by suposedly certified electricians, there really should be a danger alert button next to like/dislike buttons. This was always the case I guess, but with lithium batteries it really became critical to design safe systems. It is entirely possible to DIY but it requires navigating through a lot of dubious advice before you learn enough to zero in on those that actually know something from (bad) experience. Like this one: https://marinehowto.com/lifepo4-batteries-on-boats/

 

In essence, find someone with a lot of specific experience to do this for you, not just any electrician.

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Are these LiFePO4 or a different Lithium type?.

LiFePO4 has a different cell voltage to most other Litihum ions (3.2V instead of 3.6-3.7V) so 4 in series gives 12.8V for LiFePO4 and around 14.6V for others.

Check that the 14.7V is the charging voltage and not the nominal operating voltage.

 

Most (all?) LiFePO4 for motorhomes have built in control electronics to prevent over charge/discharge for safety reasons. Personally, I would not consider Lithiums without this.

 

 

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Andrew-clark - 2020-09-18 8:21 PM

 

I am currently converting a van to a family camper, and have got to planning the electrics. I was planning a 12v system charged from the van and from a solar panel. It will run a small 12v compressor fridge, led lights, some USB charging ports and a diesel heater. I plan to avoid using an inverter for now.

 

I have been offered some used, but good condition, 14.7v 46Ah lithium batteries which were surplus to requirements elsewhere.

 

My question is whether it is possible to incorporate such a battery into a 12v setup? If so, are there any addition parts required to run the system safely?

 

Just collected the motorhome today from Camper Components (www.campercomponents.co.uk) and have to say, after a comprehensive handover, I am impressed with the workmanship and the effectiveness of the system. These guys know what they are doing when it comes to lithium battery systems. Everything is bluetooth connected to my iphone on the Victron Connect App (although there is also a visual monitor inside the van) to monitor battery levels, charging levels charging amps from either the solar panel, alternator or mains charger and it is impressive. With the engine just on tick over there was 30+amps going in!

 

I can only reiterate Andrew, Lithium systems are brilliant but do take professional advice on building and installing the 'system' rather than just a battery.

 

David

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