Lithium Batteries, who has them?

[T1 Terry]

What inverter are you running and what controller are you changing to? Always interested to see what components are being run with lithium batteries and how well they have found them as far as cooperation with the lithium charging regime. We have found one of the hardest things have been getting the solar regulator to return to boost mode without flattening the battery first. Many regulators will not return to boost unless the voltage drops below 12.6v, that's still close to fully charged for lead acid, very close to fully discharged for lithium batteries.

T1 Terry

[jon_d]

Hi Terry,

re: Many regulators will not return to boost unless the voltage drops below 12.6v,

I'm just reading though the spec of my controller.
When you say "boost" do you mean asborb, or float.

thanks
jd

[Mrcoolabah1au]

My pl 20 has a boost mode ?

[T1 Terry]

Hi Terry,

re: Many regulators will not return to boost unless the voltage drops below 12.6v,

I'm just reading though the spec of my controller.
When you say "boost" do you mean asborb, or float.

thanks
jd

Many regulators will stay in float mode till they sense a preset voltage, often 12.6v is the figure used. Absorption has a different meaning to different controller manufacturers. The likes of Plasmatronics have 3 distinctly different phases, Boost, Absorption and Float, each can have the voltage set independently, a slightly higher boost voltage than the absorption voltage achieves a faster charge to 70% in a lead acid battery and 98% - 99% in a lithium battery, then the float voltage is generally set at 13.8v to as low as 13.2v for lead acid batteries to stop excessive electrolyte boiling, well really hydrolysis, but all resulting in the temp rising and possibly damaging the battery if sustained for a long period. 13.8v is not an issue, 13.2v is around 50% SOC or less in an Li battery so a return to boost voltage is required.
Some manufacturers use the end of boost voltage as their absorption voltage and can maintain this voltage for quite a long time, a formula relating to how long it took from the charge first starting till boost voltage was reached. This is fine for a lead acid battery, death for an Li battery as the boost voltage point is reached at 99% SOC, holding that voltage for an extended period will result in a very short cycle life... something a well known manufacturer is about to discover as a rather expensive lesson no doubt.
So, as a straight fit up, very few controllers make the grade for use with Li batteries, but with a suitable interface, any charger can be tamed to a point that the lithium batteries are happy with the charging regime, the return to boost is the difficult one to over come though.

T1 Terry

[LeighC]

Hi Terry,
My Outback MX60 charge controller has the Rebulk (return to boost) set at 13.0v & seems to work quite well. The MX60 will only adjust Rebulk in full 1.0v increments though.
I have Absorb End (return) amps set to 1% (4 amps) on my 12v 400A/H Carb LiFeP04 PowerPak.
Would never dream of going back to L/A batts.
Cheers - Leigh

[T1 Terry]

Leigh and welcome to the forum,
Does the MX60 have a time before return to boost as well? The Plasmatronics units do so we use the same 13v and 1 day before return to boost. The beauty of the Plasmatronics and Outback and Midnite solar equipment is all parameters are adjustable so they can be tuned to suit the Li batteries. They still need a secondary control system that monitors cell voltage though because at the end of charge is the point cell run away occurs. The Boost voltage may be 14v or 3.5v per cell, but one cell @ 3.8v and 3 cells totalling 10.2v or an average of 3.4v still adds up to 14v, yet one cell is getting damaged without anyone knowing.
An adaption of an old saying, look after the cells and the battery voltage will look after itself

T1 Terry

[native pepper]

What inverter are you running and what controller are you changing to? Always interested to see what components are being run with lithium batteries and how well they have found them as far as cooperation with the lithium charging regime. We have found one of the hardest things have been getting the solar regulator to return to boost mode without flattening the battery first. Many regulators will not return to boost unless the voltage drops below 12.6v, that's still close to fully charged for lead acid, very close to fully discharged for lithium batteries.

T1 Terry

I'm using a 1500w 12v inverter in the bus and don't know the name of the 80ah charge controller as they haven't arrived yet, but are in the country and Slowy's kids are sending them in a few days ago after they test them for us. They were ordered before Slowy left us and the manufacturer had to make adjustments to suit what he and his kids wanted.

Do know all the charge voltages are fully programmable, so you can just use bulk charge and not float or the other unnecessary charge features. Also putting in some 150amp relays and cell alarms as safeguards to cut charge before the charger if something goes wrong with the BMS and cell balancers.

I struggle with this technology, Slowy had all the brains with this stuff. Used to amaze me how he would tell people he knew nothing, yet had heaps of qualifications in building, electronics and computing.

[jon_d]

Terry, mine does.

I can set the Absorb time between 1 minute and 100 hours.

http://www.mppsolar.com/manual/PCM_CX%2 ... new%29.pdf

[T1 Terry]

It will be interesting to see what brand they are. Slow Hand and I had a few differences in our approaches to these things, but he always sounded like he had the whole thing sorted. Keep us in the loop with how things are going with the changes to the system, always like to see other peoples approach to tackling these jobs.

T1 Terry

[T1 Terry]

Terry, mine does.

I can set the Absorb time between 1 minute and 100 hours.

Good to hear, I'm guessing all the voltages are adjustable as well then, so it will be a matter of tuning the system to suit your use patterns while still keeping the batteries at a safe voltage. The tricky bit is the end of charge voltage, too low and the battery never fills and a memory effect occurs resulting in apparent loss of capacity, too high and the cells are damaged, just right and the system looks after itself with virtually no outside interference required