# LiFePO4 deep cycle for use in RV type vehicle?



## hans j (Mar 31, 2008)

The topic came up in a Volkswagen Vanagon forum, specifically for use in Westfalia campers as the second battery to power the fridge and other accessories. It would need to only be 12v but would need to be somehow charge regulated by the alternator or perhaps a charge controller which also gets power from a solar panel on the roof. It would also be nice to be able to plug it in to 110v to charge if you were at a powered campground.

Any thoughts or ideas on this approach? I would love to run some 100Ah or higher! They would likely last a very long time since most people are only using 100Ah SLA for their "house" batteries. The light weight would be a big help too


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## bjfreeman (Dec 7, 2011)

using Trojans T105 you cost is about $250 for 225 AH at 12V.
Using Optima you cost is about $875
using Lithium your cost is about $1,500. which includes BM unit.
Charging rates are best with Trojans and Optima
This gives you a about 7 min with 600 Watt microwae using an inverter
you might look at the Onan Hybrid that delivers 10KW AC. cost about 21,000.


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## Outtasight (Dec 8, 2011)

Depends on how much they use the camper really. If it's a few weekends a year then just go cheap SLA - Trojans and other wet batteries are a problem in a confined space - need to be able to vent the gas or else _you_ get gassed!

I've used sealed gel and AGM batteries in my house project. Had flooded in the beginning and had to run fish tank tube to the outside to vent the charging gasses away.

Lithium would be a consideration for very heavy daily cycling for living on the road. You can get 90Ah Winston "12V" LiFePo4 monoblocks that don't need a battery managment system (BMS). The 4 cells are sealed in a box with no access to the individual terminals. They're about 400 Euros. You just need some half decent solar charge controller that can keep the thing between 11 and 15V WITHOUT FAIL. 

If you do the usual camper thing of running the battery down until the lights go out, you'll ruin a lithium pack on day 1... They cannot stand being over discharged at all. Ditto on the charger. Over charging lithium packs to 17V will kill them in a few cycles.

The 12V monoblocks are being touted as a replacement for the usual lead acid starter battery on cars so can safely be charged from a decent alternator. But leave the lights on one time and... permanently dead battery. No second-ish chances like with lead acid starting batteries.


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## hans j (Mar 31, 2008)

Outtasight said:


> Lithium would be a consideration for very heavy daily cycling for living on the road. You can get 90Ah Winston "12V" LiFePo4 monoblocks that don't need a battery managment system (BMS). The 4 cells are sealed in a box with no access to the individual terminals. They're about 400 Euros. You just need some half decent solar charge controller that can keep the thing between 11 and 15V WITHOUT FAIL.
> 
> If you do the usual camper thing of running the battery down until the lights go out, you'll ruin a lithium pack on day 1... They cannot stand being over discharged at all. Ditto on the charger. Over charging lithium packs to 17V will kill them in a few cycles.
> 
> The 12V monoblocks are being touted as a replacement for the usual lead acid starter battery on cars so can safely be charged from a decent alternator. But leave the lights on one time and... permanently dead battery. No second-ish chances like with lead acid starting batteries.


I have seen the lithium blocks used as starting batteries and they are kind of cool!

It is very unlikely the pack would get drained 100% or even 60%. Mostly a slight trickle unless I find a neat microwave to use (still a very small camper!). Many people still only have their starting batteries to handle the load, aux batteries just limit the possibility of killing your starting battery by watching dvds or something on a rainy day and definitely reduce the need to start your engine to charge the batteries while camping.

I may have found some cheap 50Ah LiFePO4batteries I can experiment with. I have also been looking at RC car battery chargers as they can keep them correctly charged by using the vehicles 12v alternator source. The RC charger also can balance and discharge for storage if necessary. The only hurdle is the RC batteries are usually up to 5000mAh and mine are basically 50000mAh! So charging time might be slower, but that's ok, lots of time on the road for that; plus solar power to supplement while parked.

Sample of a medium priced RC battery charger:
http://www.rcplanet.com/ProductDeta...gdftrk=gdfV23720_a_7c1734_a_7c7524_a_7cTHP610

This is a SLA battery often used for this application, maybe a couple of them to bump up the total Ah:
http://www.staabbattery.com/product/sla-12/UB12220-V.html

One concern I have is fire. I have seen few reports of DIY EV's catching fire but while reading the RC forums, it is much more common  So a stainless steel box is likely in order as a case when I do it.


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## Yabert (Feb 7, 2010)

Some RC charger can detect temperature and stop a abnormal charge before battery catch fire.

I used Icharger and they work perfectly: http://epbuddy.com/index.php?main_page=index&cPath=17_1&zenid=mmjipgdrdkhesjm79h96pbh947


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