Programmable chargers for LiFePo

[Izabarack]

What I want is a charger that will take solar or alternator input and put out 14.1 to a LiFePo 12 volt (nominal) bank until current in drops to 150 mA, then disconnects all charge. No float setting is wanted or desired, just turn off all charging operations when the battery bank reads 14.1. Don't give a Fat Rat's Arse (FRA) about balance between cells at this point, just a cessation of charging effort at 14.1 indicated by a drop of charging current to 150mA. 14.1 is the figure I decided on as containing enough fiddle factor to really/actually achieve a rested voltage of no more than 14 volts for 4 in series cells or 3.5 volts per cell. Is there a device already out there to do the job? I do have the contacts to get one designed and built but am trying to get past that delay and cost.

The other end of the charge/discharge cycle management I want to set in place is a low voltage cutout that also sets an alarm to trigger my input to set the recharge cycle. I'm currently doing that with a multimeter a few times a day using back-of-an-envelope calculations (I'm BSing there, I do the calculations in my head) of energy usage to predict SOC in real time. In the recent weeks this has worked fine. I put the battery bank on charge first thing in the morning and turn off/disconnect charging by about lunch time. Test conditions are a 40 litre Engel keeping half a slab of Fat Yak cold (really cold) plus a small thermal mass of food stuff. I run three runs of LED lights at night for effect.

The second paragraph is to give some context to the question in the first paragraph.

Iza

[T1 Terry]

I doubt it Iza, the end current is far too low for a decent sized battery pack at that end voltage. 14.1v is also an average of 3.525v per cell, 0.125v over full voltage charged so unless the pack was perfectly balanced and remained perfectly balanced a cell run away is highly likely.
So I doubt very much if any manufacturer would produce such a device.
There are far better ways to achieve the desired effect using commonly available off the shelf charging gear without needing to spend additional funds on special chargers and solar controllers.
The lithium project team have spent 3 yrs now developing/adapting the base control unit to work with anything available on the market. It's a tribute to the 100 plus members who have all worked together, no back biting etc, to achieve a safe and reliable control system at minimal cost and more than one method of doing it as well, just to prove it's the principles that are the important feature, not just how it's done.

T1 Terry

[Izabarack]

The lithium project team have spent 3 yrs now developing/adapting the base control unit to work with anything available on the market. It's a tribute to the 100 plus members who have all worked together, no back biting etc, to achieve a safe and reliable control system at minimal cost and more than one method of doing it as well, just to prove it's the principles that are the important feature, not just how it's done.

And just how is that, Terry?

Iza

[T1 Terry]

Secret Squirrel stuff Iza I'm guessing (well a reasonably well informed guess actually) that it will become part of a commercially available system designed for each application and members of the lithium group who choose to do so will form a team of experienced system installers using the collective wisdom of the group to help nut out any possible issues that arise during the systems life. This way the more feed back from actual working systems we get the more complete the picture will be. There are a number of systems within the group at over 3 1/2 yrs full time operation (live on the road, free camp etc) that have been able to supply some great feed back that verifies we have got it right, so we are confident enough now to move on to the next step, setting the group up to getting the systems out there, how that will work is still being thrashed out within the group.
More info on that some time in the new yr as there are still a lot to be sorted out before such a thing gets off the ground, so this is not a free plug for the lithium install business... well not yet anyway

T1 Terry

[cvtripper]

You teaser, Terry

But, yep, Terry is right - good luck finding anything on the market that does that! There are quite a few that say they work but they don't have the figures correct and a number of suppliers with Lithium programs that are just plain wrong! One that starts with E comes to mind straight away!

There are plenty of battery monitors available that have relay outputs that would allow you to achieve what you are after though, so that might suit you? But 150mA is far to low - you'll never get there - and 14.1v too high for all the reasons Terry has already documented in his Lithium thread.

[T1 Terry]

You teaser, Terry

But, yep, Terry is right - good luck finding anything on the market that does that! There are quite a few that say they work but they don't have the figures correct and a number of suppliers with Lithium programs that are just plain wrong! One that starts with E comes to mind straight away!

There are plenty of battery monitors available that have relay outputs that would allow you to achieve what you are after though, so that might suit you? But 150mA is far to low - you'll never get there - and 14.1v too high for all the reasons Terry has already documented in his Lithium thread.

There is one with a British sounding name starting with S yet made in Taiwan and An Aussie MPPT one that starts with G that both claim they have a lithium charging profile that I'd avoid using their charging regime, along with the advertised charging regime for lithium on the Plasmatronics site, it only suits one resellers BMS system and I'm not too sure how well it goes with that either so if you chose to go down that path you would need a few independent reports on how well it worked just for peace of mind.

T1 Terry