Forum Discussion
- We have lithium battry powered chain saw. It is not the same heavy duty construction of my 50 cc gas chain saw though.
It performs well but after about the tenth use something happened to the battery and would not charge. Lowes graciously replaced it.
The little saw was only 179.00 but an extra battery was 100.00. Seems there are still some things with Lithium Ion batteries to be sorted out.
Two years ago a husband and wife, small business was selling these batteries, in Goshen, Ind rally. One battery to replace my four 6 volts was about 4,400. I seem to remember and weight less than one. A new charger and controller was about 1,100.
Quoted life of battery and no hassle of maintenance sounded good but I guess we are glad to have waited.
Within five to ten years they should be affordable and more reliable. I'm not to thrilled about the idea of a Lithium Ion bomb, in one of the bays. Anytime you pack a lot of energy in a small container, if in the form of a battery you face problems with heat and possible run away discharge, or faults between cells etc that can make for a very energetic bang of now. In the Army we had batteries on helicopters that were nickle based. You could replace indivdual cells and tey weighed next to nothing and were small. It's been so long I don't remember voltages and number of cells. I don't remember very many instances of replacing them. It took quite a bit of power to spool up the engines on Hueys especially the later G and H models. Cost is the reason they weren't used in autos. smkettner wrote:
I don't think they rate LFP batteries like that. Typically it's the full capacity (100%).
That 80% window is the "full" rating.
Similar to the 80% propane tank fill becomes the 100% usable capacity.reed cundiff wrote:
The battery management system (BMS) should prevent overcharging and over discharge. The BMS should keep you in the middle 80% to prevent damage. That 80% window is the "full" rating.
Have been following LFP and solar on Solar Forums and no one suggests going to 100% DOD. Even there folks have LiCo and LFP confused.
Similar to the 80% propane tank fill becomes the 100% usable capacity.smkettner wrote:
Most BMS's will "only" let you discharge 80-90%. Getting to 100% is tricky without permanently ruining them.
Keep in mind you only need half the capacity as Li can be discharged 100% of rating.- Have posted elsewhere that we are quite pleased with our LFP suite: four batteries composed of 4 each 180 amp-hour 3.4V cells in series to provide 180 amp-hours at 54 V, or about 9600 W-hrs of which 7500 or more is usable at 80% DOD. This was $6K a year ago and I agree with MEXICOWANDERER that the costs should drop greatly as it becomes increasingly competitive. This has made us solar autonomous. My wife can use her heating pad (55 W) for several hours every evening. We spent six days in the Olympic rain forest three weeks ago and were only down 50% DOD.
Have been following LFP and solar on Solar Forums and no one suggests going to 100% DOD. Even there folks have LiCo and LFP confused.
mlts22 The system does have a converter to step down the 54V to 12 V.
Each of the four batteries (composed of four 3. 2 V cells) has its own individual BMS. These batteries are produced by Manzanita in Washington. They are designed for electric cars, motorcycles,and boats which require high discharge rates and are not optimal for the normally low discharge rates of an RV We generally use the microwave every day, and have run the 1.5 kW ac unit a number of times as a combination of 1.4 kW of solar and the batteries. We have tested the system running both a/c and mw and the 4.0 kW PSW inverter handled it well for 20 minutes. This was done with our son (the designer and fabricator) in attendance (it was his idea).
Reed pianotuna wrote:
Hi,
400 amp-hours is getting within striking distance. Now, if they would solve the cold weather recharge problem......
Well these are LiFeYPo4 and supposedly much more well behaved across a wider temperature band than other flavors. Not sure I believe their apparent -45C - 85C charge and or discharge operating temp as indicated here:
Winston 400Ah cells- Hi,
400 amp-hours is getting within striking distance. Now, if they would solve the cold weather recharge problem...... - Keep in mind you only need half the capacity as Li can be discharged 100% of rating.
atreis wrote:
They've come down a little... (But are still quite expensive.)
LiFePO4 100AH for $1,300
LiFePO4 200AH for $2,400
These are (more-or-less) drop in 12V replacements with built-in BMS. They won't fully charge on 13.3V float though, which could mean having to use a different charger or a programmable solar charge controller that allows setting of the various voltages.
200Ah for $1430
700Ah for $3350
1200Ah for $5250
700Ah @ 24v - 1400Ah equiv. for $6650
I was told they have a 400Ah @ 12v version too for $1920- Hi mlts22,
2oldman has been using a dc to dc converter successfully for several months now.
Since most rv's now have a 120 volt converter that can be used, it would be a simple matter to just feed it from the inverter on the solar trailer. A 12 volt battery (OEM) could be used for times when the solar trailer is left behind.
