LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[georgec]

Originally Posted by evm1024

The same in my manual. However the actual charger does not have a Custom battery type (like the manual says) it has "OEM Preset" in its place.

Can you check your SW3012 menu?

I'm wondering is there was a jumper that needed to be removed or firmware or?

My actual model is an 815-3000 made on 09/Aug/2011

Regards!

The menu options on the System Control Module match the manual. Once I set the battery to custom all of the parameters are set under Custom Settings. The charger inverter part number is 815-3012. I purchased it from Defender last spring during their spring sale.

[evm1024]

Originally Posted by georgec

The menu options on the System Control Module match the manual. Once I set the battery to custom all of the parameters are set under Custom Settings. The charger inverter part number is 815-3012. I purchased it from Defender last spring during their spring sale.

Thanks! You have the newer model SW3000 (815-3012). Mine is an 815-3000.

It is looking like in the early 815-3000 versions there is a custom battery type that could be set by the dealer (or factory) thus OEM Preset.

It may be that somewhere in the 815-3000 production the OEM Preset morphed into a user settable set of parameters.

Then out came the 815-3012.

Anybody know how to set the OEM preset values on the 815-3000 ?


In the mean time if I set my unit to AGM battery type I can charge my LiFePO4 bank. There is a bit of a trick....

My unit lets you set the man percentage charge current. The default is 100% and at that the unit attempts to go to 14.4 volts and current limits to 130 amps or so.

Monitoring the actual pack voltage I can shut the charger off at 13.9 volts. Of course this does not get the pack full. The knee is too abrupt at that charge rate.

I've been using 100% current and at pack voltage 13.6 change the % current to 50% which drops the current to 50 or 60 amps. Then when the pack voltage gets to 13.7 I drop the current limit to 20% which is about 25 amps and stop charging at 13.8-13.9 volts.

Regards

[Jd1]

I am happy to report that my shipment of 700 Ahr battery cells from Balqon is on the truck ... WoooHoooo !!!! Their shipping time (time before the shipment left their warehouse) was two weeks, exactly as promised !
A big worry (because of all the reports of several months delays) is off my back now.
Now I have to figure out how best to test battery capacity .... are there any easy setups or do people just hook up a load, measure current draw and see how long it takes to run the cell to the lower knee voltage ?
Ideally I would hook up a battery monitor to let it compute the AH's withdrawn to compensate for any drop in current to the load due to the slight drop in voltage but I haven't got one of those yet. I am leaning towards the Clean Power display EV Display - CleanPowerAuto LLC and would appreciate comments about it or suggestions about any better alternatives.

[nimblemotors]

That product appears to use the same 600amp current sensor I use in my 1000amp motor controller. It has limited accuracy at low current,
where 1 amp is .0025 volt and the spec is +-.035v,
so +- 20 amps. L01ZXXXS05.pdf
I built a capacity tester, and is about 5amps max discharge, at 700ah,
that would take a long time (6 days) You definitely need to account for the change in amps as the battery drains if you want accurate results.

Originally Posted by Jd1

I am happy to report that my shipment of 700 Ahr battery cells from Balqon is on the truck ... WoooHoooo !!!! Their shipping time (time before the shipment left their warehouse) was two weeks, exactly as promised !
A big worry (because of all the reports of several months delays) is off my back now.
Now I have to figure out how best to test battery capacity .... are there any easy setups or do people just hook up a load, measure current draw and see how long it takes to run the cell to the lower knee voltage ?
Ideally I would hook up a battery monitor to let it compute the AH's withdrawn to compensate for any drop in current to the load due to the slight drop in voltage but I haven't got one of those yet. I am leaning towards the Clean Power display EV Display - CleanPowerAuto LLC and would appreciate comments about it or suggestions about any better alternatives.

[Jd1]

An alternative battery monitor would be this Victron unit :
http://www.victronenergy.com/upload/...-series-EN.pdf

[evm1024]

Congrats!

Top balance them first per mainesail's directions. (let them sit parallel after charging individually etc)

Once balanced I wired in series and then discharged them about 50 AH worth and then charged them at a constant 30 amps and recorded the time for each change in mV up to a pack voltage of 13.8 volts.

This was entered into excel which can make a plot. The upper knee was clearly shown with the voltage change flat up to about 13.6 volts. Above that there was a rapid voltage gain to the cutoff at 13.8.

I've not done the discharge curve yet. If I were to discharge at 100 amps it could take 7 hours!

I might try to discharge my bank to 20%soc in spurts then discharge at a 20 amp rate and record the voltage vs time. I would be looking for the lower knee.

The goal is to have a "full" voltage (13.6 @ 30 amps charge rate) and a discharged voltage (at 20 amps rate).

I do have a victron bmv-600s that I can recommend to you for AH counting.

I also have the housepower BMS with individual cell monitor.

Regards

[evm1024]

One more thought. I do have a good Fluke portable meter and some Tektronix TM-500 series meters on my bench. I picked up (and you can too) a 500A=50mV shunt at my local marine surplus store. The shunt cost me $25 or so and allowed me to get the amps in or out for my bank when on the bench.

(the BMV-700 looks nice too)

[Jd1]

Originally Posted by evm1024

I do have a victron bmv-600s that I can recommend to you for AH counting.

What made you choose the Victron 600 vs the 700 series and was the Clean Power display considered at all ?

[evm1024]

I've had the 600 for years (I don't think the 700 was available then) Just found out about the 700 from your post.

I use the bmv-600 for ah use (and soc) and a quick check of house and start voltage.

I have plans on getting the Hobby King monitor as an initial cell level monitor. Much less expensive than the Housepower unit. The house power stuff I have is quite nice to I expect the monitoring unit to be up to par.

I do have a side project of making a monitoring unit / charge controller starting. Based on the BeagleBone micro. Not much to say about it yet. Just some Ideas to try out.

[Jd1]

Originally Posted by evm1024

Congrats!

Top balance them first per mainesail's directions. (let them sit parallel after charging individually etc)

Once balanced I wired in series and then discharged them about 50 AH worth and then charged them at a constant 30 amps and recorded the time for each change in mV up to a pack voltage of 13.8 volts.

This was entered into excel which can make a plot. The upper knee was clearly shown with the voltage change flat up to about 13.6 volts. Above that there was a rapid voltage gain to the cutoff at 13.8.

I've not done the discharge curve yet. If I were to discharge at 100 amps it could take 7 hours!

I might try to discharge my bank to 20%soc in spurts then discharge at a 20 amp rate and record the voltage vs time. I would be looking for the lower knee.

The goal is to have a "full" voltage (13.6 @ 30 amps charge rate) and a discharged voltage (at 20 amps rate).

I do have a victron bmv-600s that I can recommend to you for AH counting.

I also have the housepower BMS with individual cell monitor.

Regards

I have the mainesail recommended Mastech power supply coming so the plan was to first let the cells sit in parallel for a few days then hook them up in series and charge to 13.8V without much concern about the actual charge rate. Then manually top balance each cell until they all match. After that I would attach a load of some kind (still to be determined) and discharge to the lower knee voltage while somehow keeping track of the Ahr's used up. I would then recharge to a 13.8V pack voltage and verify that the cells are still in balance.
I do have some cellog8's coming in to monitor the individual cells and allow for emergency shut-down if anything weird happens. Unfortunately I have no idea when those things will come in as they are likely coming from the far east.

[simat]

Originally Posted by Jd1

Now I have to figure out how best to test battery capacity .... are there any easy setups or do people just hook up a load, measure current draw and see how long it takes to run the cell to the lower knee voltage ?

The project I have made and using to monitor my battery bank using the Beaglebone would do the job. I am happy to modify the software to facilitate this type of testing, would be useful for me as well.

Simon

[OceanSeaSpray]

Originally Posted by Jd1

Now I have to figure out how best to test battery capacity .... are there any easy setups or do people just hook up a load, measure current draw and see how long it takes to run the cell to the lower knee voltage ?
...

What is testing battery capacity going to achieve? Unless you are going to send some cells back if you are not happy, you are pretty well stuck with what you have got.

If you want to rate the capacity to track degradation over time and cycles, you will need pretty good gear in terms of Ah-meter and the test would need to be performed in the exact same conditions again later.
If you do that, you might want to rate each cell separately. The capacity of the pack is at best equal to the smallest cell and normally smaller.

[Jd1]

Originally Posted by OceanSeaSpray

What is testing battery capacity going to achieve? Unless you are going to send some cells back if you are not happy, you are pretty well stuck with what you have got.

I have heard of Balqon cells that had less than rated capacity. The 700 Ahr pack is a significant enough investment that I want to make sure I got what I paid for. If the capacity turns out to be below spec then I will be looking for replacement(s) that meet or exceed spec.

[Maine Sail]

Originally Posted by Jd1

I have heard of Balqon cells that had less than rated capacity. The 700 Ahr pack is a significant enough investment that I want to make sure I got what I paid for. If the capacity turns out to be below spec then I will be looking for replacement(s) that meet or exceed spec.

In order to accurately test these cells to "spec" you would need a 350A load. A tad large.... They are rated at 700Ah at a .5C load (50% of capacity)...

For example on my own 400Ah bank I test them at a .25C load (100A) and get 425Ah's. If I test them at .5C I get about 400Ah. If I test them at 15A I can extract 440Ah's from them.....

On my next capacity test, at 550 cycles, it will be done at a 40A load and future tests will be done there because my capacity testing equipment for lead acid only goes to 40A and I can easier automate it than I can the 100A load.. All my capacity tests from the beginning have been done using the same equipment and the same load to remain as consistent as possible.

Lead acid batteries are rated at a 20 hour load which is Ah capacity ÷ 20. So a 400Ah lead acid bank would be tested at a 20A load to the cut off voltage at 75-80F. There is a huge difference between a bank rated at .5C vs one rated at .05C

[nimblemotors]

It is also good to test each cell to make sure they are relatively balanced capacity, since you only get what the weakest cell gives when connected in series.

Originally Posted by Jd1

I have heard of Balqon cells that had less than rated capacity. The 700 Ahr pack is a significant enough investment that I want to make sure I got what I paid for. If the capacity turns out to be below spec then I will be looking for replacement(s) that meet or exceed spec.