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Care of LFP batteries


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LFP batteries should not be charged if below 32 F (0C). We have put a remote thermometer ($20 or so from Lowe's or Home Depot) in the compartment in which the battery suite is installed. It got below 24 last night but it remained above 40 in the compartment which is well insulated. All of the peripherals for the electrical system are in the same compartment and these may add heat. If the temperature gets below 35, we shall just put in an inspection lamp with 30 W bulb.

 

The other worry is getting the battery suite to hot when we are in Yucatan next month. We have three 12 V fans (1 amp at 12 V or 12 W). We can put one or two in the compartment to move air as well as opening the front panel and both side panels. TJust glad we will not have nesting Carolina Wrens down there. These beautiful and charming little birds will investigate every nook and cranny looking for a nesting site.

Reed and Elaine

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Chris and Cherie are the pioneers in this technology for RVers in USA. We have followed their blog for years. They have been most helpful and considerate in correspondence. LFP was quite expensive and chancy when they personally installed their system. Costs and battery management have greatly improved in the last four years. Do not know if they have increased their battery capacity, which was around 6 kW-hrs. The Wynns were getting a new lithium battery system. Googled this and their sub-site on LFP is not working well.

 

LFP is fairly foolproof if:

1. Good Battery Management System (BMS) is used but these are pricey. However, if you put $6k into battery suite, another $500 is rather good insurance

2. Be aware of temperature extremes. The newer Lithium Ytterium Iron Phosphate cells are supposed to work to charge at much lower temperatures.

 

As noted above, charging should not be done at temperatures below 32 F but they can be discharged at -25 F. Do not know the boundaries of the LYFP chemistry/physics

 

Discussed upgrading with son and, if we were to win the lottery, we could double to 19 kW-hrs and have just about 500# of LFP cells . This would be about 16 kW-hrs of usable energy for a supposed 2000 cycles or more to 20% SOC. Elaine thinks upgrading would be a futile effort since we have never had any problems. We seldom cycle to below 70 or 80% SOC. We did boondock twice in last 18 months for 5 and 6 days in heavy timber with very little solar and were able to utilize micro-wave to heat everything and watch 90 minutes of BBC Mystery Theater. The inverter was turned off when not required since it has a parasetic drain of 50 to 70 W.

 

We do have a 1 kW Honda generator which has only been turned on to make sure it works. Have checked our monitors when we have trialed it and the batteries are charging at around 950 W. The charge rate is linear unlike lead acid. We were n a day of irain and were down 3 kW-hrs and wanted to see how things would work. We were fully charged and past float in less than 4 hours.

 

There is a lot of discussion on the subject at Solar Panel Talk and Arizona Wind and Sun among other fora. A number of discussions get rather nasty.

 

Reed and Elaine

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They are quite safe and putting them within the main compartment should work

 

Realized why the front baggage compartment may be staying "warm". All of the electronic system plus batteries are in that compartment. The battery discharge rate is about 50 to 70 W depending if inverter is on or off. That parasitic wastage is heat and that may be enough to keep compartment 10 degrees fahrenheit warmer than ambient. The walls and doors are about 3/4" to 1" fiberglass covered foam.

 

Reed and Elaine

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We put our lithium battery behind cabinet fronts in bedroom to minimize temperature extreems.

 

That was my thought. I'm a long way from being ready to retire my current bank (only 3 years old), but it seems to make sense to try to minimize temp ranges as much as possible.

 

One acquaintance of mine went LFP's recently. They really love the hot HOT weather and installed theirs in the underbed storage. He made a stand that raises them about 1 1/4" above the flooring for ventilation, installed a 1-way sidewall/ceiling register in the side of their bed frame and ran a 2" vent pipe up and out of their roof. He also mounted a single 12v computer type fan at the vent pipe intake. It will be interesting to see what kind of temp ranges he gets this Winter.

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Some of the sports car community are going to them to get rid of extra weight from the old lead/acid battery. I've always wondered if they are actually that competitive to make the weight difference matter, or is it partly a status symbol?

 

It is about time for a major step forward in storage batteries as the old reliable ones we have been using were invented years ago. I wonder if the technology has found it's way into the submarine service yet? Now those were serious batteries! Each cell was 1 ton in weight. :o

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