Need advice charging LifePO4 with IOTA DLS-90

solarpowernovice

I bought 4 Litime 12v 100ah lifepo4 batteries on Black Friday and an Iota IQ-LIFEPO Lithium-Iron Batteries Automatic Charge Controller for DLS Charger. The batteries arrived yesterday and I've yet to get the charge controller for my DLS-90 iota charger. I would like to know if the DLS-90 will charge all 4 batteries at the same time, hooked together in parallel or should I charge them separately?

I know the batteries need to be charged ASAP but will the IOTA do the job and what's the ideal way to connect them? Thanks in advance.

BB.

In general, LiFePO4 batteries are best kept "on the shelf" at around 50% SoC (say 20% to 80% range)... They have very low self discharge (assuming no loads)--And can sit unused for years without charging. So, unless these batteries are near 0% SoC, there is no "rush" to recharge them (unlike lead acid batteries that need to be "stored" >75% SoC or they will begin to sulfate rather quickly).

Q: What battery charger should I use for the LiTime 12V 100Ah smart LiFePO4 lithium battery?

A: We recommend using a 14.6V lithium iron phosphate (LiFePO4) battery charger to maximize the capacity. ☆ Recommend charging voltage: 14.2V ~ 14.6V ☆ Recommend charging current: 20A (0.2C): the battery will be fully charged in around 5hrs to 100% capacity. 50A (0.5C): the battery will be fully charged in around 2hrs to around 97% capacity. Attention: ☆ Connect the charger to the battery before connecting it to the grid power in case of sparks. ☆ Remember to disconnect the charger from the battery after fully charging.Assuming this is the DLS-90 specs:

https://www.iotaengineering.com/products/detail/1185701/iota/dls-90a-converter-and-charger/90-amp-acdc-power-converter-and-battery-charger-for-dc-load-operation-and-12v-battery-charging

The DLS 90A Power Converter/Battery Charger from IOTA converts nominal 108-132 AC voltage to 13.4 DC voltage for both DC load operation and 12V battery charging.
As a power supply, the unit's tightly controlled regulation allows the user to operate a nominal 12VDC load up to 90 amps.

Your batteries?

https://www.litime.com/products/litime-12v-100ah-smart-lifepo4-battery

BMS

BMS：

100A

Max. Continuous Output Power：

1280W

Max. Continuous Charge Current：

100A

Max. Continuous Discharge Current：

100A

Max. Discharge Current 5 Seconds：

300A to 500A

CHARGE

Charge Method：

CC/CV

Charge Voltage：

14.4V ± 0.2V

Recommend Charge Current：

20A (0.2C)

You may need to talk with Iota and LiTime about charging... The DLS-90 rated:

And the LiTime charging requirements:

Q: What battery charger should I use for the LiTime 12V 100Ah smart LiFePO4 lithium battery?

A: We recommend using a 14.6V lithium iron phosphate (LiFePO4) battery charger to maximize the capacity. ☆ Recommend charging voltage: 14.2V ~ 14.6V ☆ Recommend charging current: 20A (0.2C): the battery will be fully charged in around 5hrs to 100% capacity. 50A (0.5C): the battery will be fully charged in around 2hrs to around 97% capacity. Attention: ☆ Connect the charger to the battery before connecting it to the grid power in case of sparks. ☆ Remember to disconnect the charger from the battery after fully charging.

So the DLS-90 is a bit lower voltage than the LiTime batteries require(?)... You will need to figure out if this a bit issue or not (i.e., batteries may not fully recharge?).

As long as the batteries are nearly the same resting voltage (i.e., within a few 0.0xx volts of each other), you can parallel them 1-4 and recharge all from your 90 Amp charger. If you had a 20% SoC battery in parallel with a 100% SoC LiFePO4 can cause high currents between the batteries (the 100% battery charging the 20% battery and possibly exceeding charging/discharging current specifications).

For best battery service life, you probably would be better off connecting the 4 batteries in parallel to charge at (90 amps / 4 batteries in parallel=) 22.5 amps per battery... Charging one battery at 90 amps, while in specifications, is probably not best for battery cycle life (kind of hard on battery cells).

Note that the DLS-90 draws ~20 Amps on 120 VAC. A typical 15 Amp 120 VAC outlet may overheat/trip a breaker during heavy charging current.

-Bill

solarpowernovice

Thank you Bill. The batteries I have are a little different. Here is the link: 
https://www.litime.com/products/litime-12v-100ah-lithium-lifepo4-battery?utm_source=facebook&utm_medium=adcpc&utm_campaign=转化-YJ-1122-黑五+12v+100ah-兴趣-折扣图-bid+cap&utm_content=转化-YJ-1009-秋季亚马逊活动-Photovoltaics-折扣图-黄&campaign_id=120203242397750260&ad_id=120203242397700260

And for the IOTA DLS-90 charger I ordered this: Iota IQ-LIFEPO Lithium-Iron Batteries Automatic Charge Controller for DLS Charger https://a.co/d/doYfjsR  Will this charge controller raise the voltage from 13.6 to a suitable voltage for my batteries?

 The batteries are currently all sitting at 13.1 volts. Attached is a picture of how I plan on connecting them in parallel... Please correct me if you see anything wrong with the layout. If it is correct, where do I hook the cables from the charger? On opposite corners of the battery bank? Thanks again.

Dave Angelini

You really need some help from the battery Co on how to measure State of charge. The Iota is not going to charge that battery at that voltage very much. It will charge a bit but....

I think there is an option for a regulator for the iota. Not sure but if you bought it from the store here at NAZ, they could tell you !

BB.

Here is a link to the IQ4 LiFePo4 charger module which is rated to charge to 14.7 volts:

https://www.altestore.com/static/datafiles/Others/IQ-LIFEPO_Manual.pdf

It says it will charge to 14.7 volts... Which is pretty high for a LiFePO4 battery... And there is a chance the BMS will shut down the battery if >14.6 volts charging (you are on the ragged edge of design specs and manufacturing tolerances).

What will happen with your setup? Do not know.

Longer thread from a year or so ago on the DIY Solar Forum:

https://diysolarforum.com/threads/iota-engineering-iq4-lifepo4-module-discussion.15440/

No real resolution there either.

-Bill

solarpowernovice

Ok I will call iota and the battery manufacturer to see if it will work. I was planning on using my iota dls-90 to charge the batteries until the weather warms up and I can hook them up on my off grid system.

 Right now I have six 260watt solar panels, a midnite classic 150 MPPT charge controller and a 2000 watt 24v inverter.  Can these batteries be hooked up to this system or is six 260 watt panels too much for them? Please forgive my ignorance, it's been a while since I built the system...

Dave Angelini

Without guidance from the battery company on it's BMS and how you will get Soc and charge, you will make your life harder and possible damage the battery..

Be concerned with the solar when you know what you have. You do need all the panel specs!

That is the reason I like using the store here as they try and sell equipment they can support. They have really good prices and don't sell equipment that is not in your best interest! (think E-Bay) They support this forum also and it is nice when people come here for help, give back a little.

solarpowernovice

I ordered most of the parts for my system on this site and the only way I put my system together was with the help of the great people on this forum. You all are very helpful and I appreciate it. What kind of questions should I be asking the battery manufacturer? 

BB.

Midnite Classic, is pretty programmable--So you can set Bulk, absorb, and float voltage points.

You might check with Midnite directly (or NAWS) and see if you have the latest firmware (Midnite does keep up on their firmware requirements).

And there are options such as the Whizbang Jr. that MIGHT give you better charge control... Such as set the controller to 14.4 volts charging, and to "end charging" at 1% (such as 400 AH battery bank and 4 amp charging tail--Or whatever you like) battery charging current--Which is a very good way to monitor the battery charging current/needs even if you do not have a full communications channel with the BMS.

https://www.solar-electric.com/midnite-solar-whiz-bang-jr-current-sense-module.html (Midnite current sense board/comm)
https://www.solar-electric.com/mkb-500-50.html (host 50mV / 500A shunt board mounts to)

Need to know the Voc/Isc/Vmp/Imp of the panels you want to connect to the 12 volt battery bank...

Also need to know approximate location (especially minimum temperatures to figure out Voc-array-cold) to not exceed the 150 Volt Vpanel-max input limit for the Classic. You can use this link to do your own calculations:

https://www.midnitesolar.com/sizingTool/index.php

The Classic needs Vmp-array of Vmp-array 20 volts (because of Vmp-array-hot minimum needs) to Vmp-array of 110 Volts (because of Voc-array-cold limits).

Your array could probably be configured to 1 series by 6 parallel to 3 series by 2 parallel--And depending on exact panel Voc/Imp/etc. specs and your local minimum temperature even 6 series by 1 parallel string...

More or less, the most efficient MPPT array configuration is around 2x Vbatt (2x 15 volts = 30 Vmp)... The easiest wiring is to run Vmp/Voc array as high of Voltage as you can... This gives you have operating voltage and low array current--Allows you to use much smaller AWG copper wiring (save Copper $$$, longer/more efficient wire run from array to MPPT controller.

-Bill

BB.

Your Classic should be programmable to not damage your batteries and let you use most of their storage capacity. If you had a BMS feedback use, in theory you could use probably a few percent more of battery capacity.

However, you have other questions... From what little I have seen (I am no battery expert/engineer)--Ideally, running the LiFePO4 bank between 20% to 80% SoC will give you the longest cycle and "aging" life. If you run at 95% to 100% SoC, still within specs, but you will probably have a significantly shorter aging/cycling life.

Always the trade-off between a smaller (cheaper) battery bank using a "100%" of capacity and "somewhat shorter" life, vs a larger battery bank cycling to 80% of capacity (25%+ larger battery bank) and hopefully a longer life (25% longer life???).

What to ask the "engineers"? Well, more than likely you will not talk to a "design" engineer but a sales engineer instead (believe me, probably should not talk to a design engineer--Very long and sometimes confusing "answers").

The sales engineer will probably answer what is in "his" specifications. If it says 14.2 to 14.6 volts, and you feed it 14.7 volts--The answer is "outside" of specified charging voltage range. "At best", your bank would turn off (unsafe voltage). Or it will sort of run OK (what if your charger is 14.65 volts, and the BMS is set for 14.8 volts). Works most of the time except if cold or hot weather, aging, etc...

Usually just something to avoid.

I highly suggest that battery cutoff due to Over/Under voltage by the BMS should be a "last ditch" safety device--And to never use BMS On/Off functions for "normal operation".

You don't want your nicely full battery to turn off when 101% full (randomly--Some does, sometimes does not)... DC power systems (charge controllers, inverters, DC Loads) frequently "do not like" having the battery bank "turned off" during normal operation.

We tend to think of the Chargers/etc. as setting the "system voltage"--And to a degree they do--Mostly for long term averages. When you "cut off" a battery bank, that is the battery that does the millisecond to millisecond voltage regulation/buffering (i.e., the battery holds the bus voltage to XX.X volts +/- 0.1 volts... If the battery is "turned" off, many chargers can charge to >17 volts (alternator systems can charge to >100 Volts) to the "unregulated" battery bus voltage can blow out the attached DC hardware (chargers, inverters, DC loads).

Note that "going outside" the DC bus voltage range can "fry" DC transistors/etc. in milliseconds. Cutting the battery connection can cause spikes longer than that--And even secondary spikes from Inductive Kick of DC wiring, etc.

These sort of issues are why you don't want to ride the edges of specifications... You (and frequently the sales engineers) do not have the details to "know" what you can risk or not. Just avoiding the edges will usually make for a "happier" customer and more reliable installation.

Just because a manufacture designs and sells something "fit for service"--Does not mean that it always "works" as expected--For example, it is (was?) very common for and AC inverter designed to run on a 12 volt battery bus to "turn off" at 15+ volts to "save itself"... However, for our "Canadian neighbors to the far north) and other colder climates, a standard FLA battery needs to float charge at 15-16.5 volts or so when in subfreezing conditions. So, the owners would need to turn off their AC inverter, EQ the cold battery bank to 16 volts, end EQ, then turn back on their AC inverter.

These are well known mfg of very reliable 12 VDC AC inverters that had the 15.0 volt limit... Why they used 15 vs 17 volts for Battery Cutoff voltage--Don't know. Could have been the choice of Transistors, or other design choices. Or some engineer decades ago decided that 15.0 volts was the highest a working DC battery system voltage that should see--And that anything over that was a "bus voltage error"...

-Bill

BB.

solarpowernovice said:

Ok I will call iota and the battery manufacturer to see if it will work. I was planning on using my iota dls-90 to charge the batteries until the weather warms up and I can hook them up on my off grid system.

 Right now I have six 260watt solar panels, a midnite classic 150 MPPT charge controller and a 2000 watt 24v inverter.  Can these batteries be hooked up to this system or is six 260 watt panels too much for them? Please forgive my ignorance, it's been a while since I built the system...

Your second question... I really like to go back to your "requirements" / energy needs. Peak, average power (Watts), total energy needed per day (Watt*Hours), and location (hours of sun per day by season).

In general, your smallest/most efficient loads (conservation) is a good start of solar. Large loads, lots of inefficient usage of electricity can be very expensive with solar (large battery bank, lots of solar panels, etc.).

Since I don't know your requirements--Lets see what your battery bank and solar array can support. Just a generic set of calculations (so you can reference how to do them--May not be what you "need" or "expect"):

200 AH * 24 volt battery bank * 50% usage (conservative for Li Ion bank) * 1/2 days of "no sun" * 0.85 AC inverter eff = 1,020 WH per day

Can supply a "cabin" (no refrigerator, except during summer/good weather, backup genset?)... For a full time very efficient off grid home maybe start at 3,300 WH per day...

Note that with a 2 kWatt AC inverter--Running at 100% inverter output would use your "daily/overnight" power up in 30 minutes (1/2 hour). Why suggest sizing the battery bank to support your loads, and the minimum AC inverter needed to run those loads.

There is always the tradeoff of needs... A large inverters for surge current (starting a well pump) vs a smaller inverter to run "small" average AC loads (LED lighting, laptop computer, cell phone charger, RV water pump, etc.).

Or there is the 1 day of storage/overnight usage--Then 2x the WH or 2,040 WH of 1 day battery storage.

Next the solar array output... Guessing 1,560 Watt fixed array near Chesapeake bay(?), facing south, 38% tilt, 61% system eff (Li Ion batteries) or 39% losses:

 https://pvwatts.nrel.gov/pvwatts.php


Toss the bottom three months (not occupied, genset usage) gives us an average month of 4.52 hours of sun per day for February.

The average harvest would be:

1,560 Watt array * 0.61 average AC Li Ion system eff * 4.52 hours of sun (Feb Average) = 4,301 WH per ave Feb day

And for a "reliable"/easy to manage system, assume 50% to 65% of average daily harvest (occasional cloudy weather, minimize genset usage, etc.):

4,301 WH per day * 0.65 solar "fudge factor" = 2,796 WH per day "reliable" February harvest.

The typical LiFePO4 battery bank should probably be charged at 25% to 50% rate of charge (longer battery life). Some list 100% of AH rating for max charge rate... The suggested array (based on "nominal charging") would be:

Your array "typical best case" charging current:
1,560 Watt * 0.77 rate of charge * 1/29 volts = 41.4 amps typical best case charging
41.4 amp charging / 200 AH battery bank = 21%rate of charge 

Your battery bank suggested (high range) of charging based on array size
200 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.25 rate of charge = 1,883 Watt array "nominal" (IMHO)
200 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.50 rate of charge = 3,766 Watt array "aggressive"
200 AH * 29 volts charging * 1/0.77 panel+controller deratings * 1.00 rate of charge = 7,532 Watt array "not to exceed"

So for your present array and Li Ion battery bank--Your are a very "comfortable" array to battery bank size. For your loads/energy needs, your thoughts?

Note that Li Ion batteries charge much more "efficiently" than Lead Acid batteries, and there is no "minimum rate of charge" specified for LiFePO4 batteries (that I know of--Again, I am not a battery engineer). And the Li Ion batteries "accept" any current into the AH capacity--No "absorb time" like Lead Acid batteries need (2-6 hours of "holding" at Charge Set point to fully charge a Lead Acid bank).

No exact answers above--But assuming you get the energy need need from the batteries (over night, cloudy day(s), etc.) and the overall harvest from the array (i.e., run irrigation/water pump/washing machine, microwave, etc. during "the day", and fewer loads at night--That is a pretty good size array for a cabin/small home.

If you wanted to run a full size refrigerator--Then a larger array and battery bank may be in the future for you.

-Bill

SteveK

As I recall my quest for a 24V charger some 10 years ago Iota had some pretty poor specifications if one was to consider using a generator at all to ever perform charging tasks. Lots of wasted energy and the poor power factor was a deal breaker for me. I was demanding some efficiencies that Iota was not capable of producing. Here is a link to that discussion if you are interested: https://forum.solar-electric.com/discussion/8821/question-about-battery-charger-selection-with-eu2000-generator#latest

Since that time I have outfitted several RV's with chargers. I found Progressive Dynamics have some good selection in their 9100L series. They check the right boxes with Lithium in mind. I won't get long winded here about them just a simple FYI. Here's a link for your perusal: https://www.progressivedyn.com/pd9100l/

The 80A versions I've tested are 84-86% efficient but, like the Iota, does require a 20A input voltage of 105-138Vac. They do an especially admirable job of monitoring and maintaining charge levels in the long term while left connected and can also supply clean power with no battery at all as in an RV setting.

Just options...

solarpowernovice

I believe I've found the solution to the Iota DLS charger dilemma. I contacted iota's customer service and apparently there's a potentiometer inside the DLS charger that will lower the voltage. According to the tech support at IOTA, lowering the DLS-90's voltage by .2v before hooking up the lifepo4 charge controller to it will make the voltage of the DLS-90 14.5 to 14.6v. 
Here is the link: https://www.rivergatedist.com/SlotAdjustment.htm
This picture shows how I plan on wiring the batteries. I'm using a DLS-90 12v charger, lowering the voltage by .2v before hooking up the lifepo4 charge controller to it. Then I'm connecting the battries as shown to the DLS-90, then plugging in the DLS-90 to the wall outlet last. Does this look good to you guys? I will wait for your reply before plugging anything in. 

BB.

The trim pot voltage adjustment has been "hack" for many years on the Iota chargers (various models). Just double check the actual voltage when charging... There is a jumper (same RJ jack as your dongle--Historically, this could be connected to a jumper/manual switch between "high" bulk and "float" voltage charging...

-Bill