Lithium Batteries for Solar

[lewster]

Using the Lithiums in low temps is not really the problem......charging them is!

I had a very long conversation with AM Solar today, and the batteries that they are showing on their web site will be built and warranted by AM Solar, including the battery cell balancing electronics and battery monitoring equipment. I will offer this abridged version of the main points of my conversation from today.

Battery specs.:

100 amp/hour basic block: 9-3/4 long, 5-3/4 wide, 10-1/2 high (these are working dimensions)

28 lbs vs. 65 lbs for a Lifeline group 27 100 amp/hour AGM

Larger batteries can be configured in many shapes, allowing them to be placed in a wider assortment of places.

The basic 100 amp/hour battery block is $1300, and this includes the cell balancing electronics and BMS (battery monitor system). Each additional 100 amp/hour block will cost approx. $700, as you only need one BMS per battery, regardless of size.

The BMS is required for the warranty to apply (3 year full replacement/5 year pro-rate replacement) as it protects the batteries from being over drawn and/or overcharged. This is EXTREMELY IMPORTANT to the long life of these batteries. Special charging requirements are necessary, as these batteries MUST be bulk charged at a constant voltage of 14.2VDC measured at the battery terminals, and float charged at 13.2VDC.

These will not be properly charged by any converter currently available, and must be charged when on-grid by a Magnum inverter/charger or similar fully adjustable power factor corrected charging system. Also, any quality solar charge controller that allows for individual voltage set points and charge duration for bulk and float will work well also. Temperature compensation is not used in these batteries

As it turns out.........the idea of Yttrium as an additive to the LiFePO-4 formula to allow for enhanced use and charging below freezing was a SCAM with no scientific or experimental backing or data. In fact, it was a ruse used by one company to try to evade a distribution contract they had signed with another for exclusive North American distribution rights to their batteries by saying that they were a different formulation. ALL SMOKE AND MIRRORS!!!!!! This LiFePO-4 formula is the best presently available.

There is significant danger of ruining these batteries when charging them at temperatures below 32ºF. Use at this temperature is not recommended but will not degrade the batteries, but charging WILL. The lithium is in a paste form and not in a mat like an AGM and will plate out to the anode and/or cathode (copper and aluminum) when charged below freezing, which will seriously degrade the performance of the batteries.

AM Solar is working on a thermostatically controlled mat that will keep these batteries above freezing at below 32ºF ambient temps. There is also NO DANGER with placing these batteries inside an RV, as they are incapable of outgassing.

Another caution: They MUST be used in the upright position....similar to a flooded lead acid type battery, as the lithium paste can migrate from covering the plated in any other orientation.

Shipping is still 'under construction' as these are classified as hazardous materials and require special handling. AM Solar is working with UPS national accounts to resolve any issues they may have with these new batteries.

Stay tuned for any late breaking developments!

[ghaynes755]

Lew looking forward to more info. Kind of a conundrum on the temp issue.

See if I have this correct. Below 32º you can use them gently but not charge them. So the idea of a heating mat would bring them up to 32º or so and then they could be charged. Challenge would be if someone is storing outside in the winter with a solar system installed it might be an interesting dance relying on solar to keep the batteries up so that the heater runs. Several bad charging days or snow cover would be the encouragement to shut everything down and manually bring the system back up. Does this sound correct?

Is there any damage to the cells in even colder temps while disconnected and not in use?

[lewster]

Originally Posted by ghaynes755

Lew looking forward to more info. Kind of a conundrum on the temp issue.

See if I have this correct. Below 32º you can use them gently but not charge them. So the idea of a heating mat would bring them up to 32º or so and then they could be charged. Challenge would be if someone is storing outside in the winter with a solar system installed it might be an interesting dance relying on solar to keep the batteries up so that the heater runs. Several bad charging days or snow cover would be the encouragement to shut everything down and manually bring the system back up. Does this sound correct?

Is there any damage to the cells in even colder temps while disconnected and not in use?

AFAIK, no problem to leave them disconnected in very low temps, as their internal discharge rate is even lower than AGMs due to almost no internal resistance. I don't see that several months of disconnected storage would be any problem.

I would think that the heat mat scenario would only be viable in an RV while in full use.

[morgandc]

Anyone know how the high discharge voltage compares to the Lifelines?

[ronstory]

Yes, charging in the below 32F can be tricky and gets complex. If a remember correctly the safe charge rate drops by to less than 1C and if you have a large pack, it can take *very long* time to charge.

Not an issue if you have access to AC power, but then you would not need to be using the battery in the first place. Controlling the temp is the best approach and I like the idea of using a thermal mat to maintain a reasonable min temp so you can charge at a typical Li rate.

[lewster]

Originally Posted by morgandc

Anyone know how the high discharge voltage compares to the Lifelines?

The BMS system that AM Solar has built operates from 11.0VDC to 16.0VDC. at the lower end, the battery has about 10-15% charge remaining, or a usable depth of discharge of about 85%.

[ghaynes755]

Morgandc if you are asking about maximum discharge rates the only thing I have found was about Thunder Sky LiFeYPO-4 batteries and it simply says max continuous of 3C. In layman terms 1C is the amp hours of the battery. So 1C on a 100aH battery would be 100amp discharge. 3C would be 300amps. That's pretty robust.

The LiPo's I use are rated between 25C and 50C, much different use. Normal flight discharge is usually in the 1.5C range.

For the Lifelines not sure how they would be rated.