Initial charge for NiFe using PV Array?

[bjmccall]

I have recently taken delivery of a set of 40 NiFe batteries (400 A-hr capacity), to construct a 48V battery bank for use in conjunction with a Xantrex XW6048 system. I'm trying to figure out how to perform the initial charge of these batteries, since (as most of you probably know) they come dry and without any charge. The XW system is actually powered by batteries, so I cannot use that system with the NiFe until the NiFe batteries have an initial charge of at least ~40 V or so.

I am considering performing the initial charge by directly connecting the battery bank to one of my PV arrays. The array consists of 4 parallel strings of 3 modules in series; the modules are KD210GX-LPU, and altogether the array has I_sc~34 A and V_oc~99 V. I realize that the open circuit voltage is way too high for this battery bank, but based on a post on another thread by Mike, I understand that solar panels act like a current source, and so the delivered voltage should automatically equal the battery voltage (0V right now, but will rise as it charges) and just pump the ~30 A into the batteries.

Naively, I am thinking that as long as I watch the battery voltage and do not let it exceed ~50V, this should be safe? Of course I would only leave the system hooked up in this way during the daytime on a sunny day. [Otherwise, I guess I need a blocking diode?]

Is this a sensible approach??

I would greatly appreciate any advice from all of you experts!!!

Thanks,

Ben (a renewable newbie)

[inetdog]

Naively, I am thinking that as long as I watch the battery voltage and do not let it exceed ~50V, this should be safe? Of course I would only leave the system hooked up in this way during the daytime on a sunny day. [Otherwise, I guess I need a blocking diode?]

Is this a sensible approach??

I would greatly appreciate any advice from all of you experts!!!

Thanks,

Ben (a renewable newbie)

If you watch the current, the voltage, and the cell temperature at all times, it should work. One potential problem is that it will take longer, with only a few hours per day to charge them. I don't expect that extending the initial charging period over several days will hurt the batteries in any way, but it will delay the time when you can use them. Especially if you go through several charging/discharging cycles to form them before putting them into service.
Mike is definitely that man to tell you though.

[SteveC]

Should be ok. I charged up my 700 amp hr. bank a year ago, from new and dry. I had no battery charger as such and used my array. However, my Outback MX60s and FM60s didn't mind the batteries being at low voltage. Using the array only, for charging, it took me several days to get the bank up to the level of charge for which I was working. Mine is a 12-volt setup.

As luck would have it, we were visited by a series of mostly cloudy days, unusual for here, right at that time. So, it took me three weeks to complete five charge-discharge cycles. But even though it took me some time and effort, the charging was completed, and I've seen no negative effect of doing it this way.

You should be just fine.

By the way, I've seen no temperature rise in my cells, even during charging up to 16.5 volts, or 1.65 volts per cell. That is measuring both the electrolyte temp. and the temp. of the cell case. None. Room temperature, unlike my forklift cells which would definitely heat up at times.

[Sundetective]

Beware

I have recently taken delivery of a set of 40 NiFe batteries (400 A-hr capacity), to construct a 48V battery bank for use in conjunction with a Xantrex XW6048 system. I'm trying to figure out how to perform the initial charge of these batteries, since (as most of you probably know) they come dry and without any charge. The XW system is actually powered by batteries, so I cannot use that system with the NiFe until the NiFe batteries have an initial charge of at least ~40 V or so.

I am considering performing the initial charge by directly connecting the battery bank to one of my PV arrays. The array consists of 4 parallel strings of 3 modules in series; the modules are KD210GX-LPU, and altogether the array has I_sc~34 A and V_oc~99 V. I realize that the open circuit voltage is way too high for this battery bank, but based on a post on another thread by Mike, I understand that solar panels act like a current source, and so the delivered voltage should automatically equal the battery voltage (0V right now, but will rise as it charges) and just pump the ~30 A into the batteries.

Naively, I am thinking that as long as I watch the battery voltage and do not let it exceed ~50V, this should be safe? Of course I would only leave the system hooked up in this way during the daytime on a sunny day. [Otherwise, I guess I need a blocking diode?]

Is this a sensible approach??

I would greatly appreciate any advice from all of you experts!!!

Thanks,

Ben (a renewable newbie)

Why don't you post your Ni-Fe Charging and first time Charging instructions that came with your Ni-Fe batteries, Ben.

Then we can compare these instructions with what Changhong Batteries themselves has published.

'Context Thinking' can develop with several views and several authors talking about the same Chinese Riddle.

We need before the big 'Solar Ni-Fe Sales Push' to compare with the after as far as Charging goes.

Claims of water consumption were always high - it no Lie.

Just higher now with the modern recommendations trying to make the 'Solar Blivet Charging' add up.

With that in mind as well as other things in mind I flew a revolutionary new Charging Concept
(Theory )
in another Internet Group a while back.
It went over like a lead balloon and a couple of guys went all wild on old Bill.
He he he.

It's a number of years too early for the Learning, AKA/ enlightenment.

If generator fuel were to near double in price they might gain the insight to see it - real quick like.
In the meantime we'll deal with what you have on hand.

Are you going to weigh a proper 'Measure' of your Electrolyte Chemicals to get a baseline on how much CO2 they have
already sucked up - real fine like?

Beware of Locking da Fox up in the Chicken Coop and then wondering why your Dogs (Battery Oil) are not protecting you.
What is the pH of the Distilled (or whatever water) that you are using.
It's acidic but just how bad is it every time you keep adding water like they are hungry Dogs - dat are never satisfied?

Start right off looking past 'The Veneer of Knowledge' and consider your own rules.

Believe little of the sweetboy Party Line.


Bill Blake

[bjmccall]

Thanks for all of your replies. I do have two of these PV arrays, so I suppose I could connect them both to the battery bank and still be below C/5.

The instructions I received from ChangHong do not mention the series of charge/discharge cycles; is this something that is generally accepted practice to condition the NiFe cells?

Also, is there any way to get hold of Mike? I tried to pm him, but evidently he does not allow pms. I would love to get his input on this issue as well.

Thanks again!

Ben

[inetdog]

Thanks for all of your replies. I do have two of these PV arrays, so I suppose I could connect them both to the battery bank and still be below C/5.

The instructions I received from ChangHong do not mention the series of charge/discharge cycles; is this something that is generally accepted practice to condition the NiFe cells?

Also, is there any way to get hold of Mike? I tried to pm him, but evidently he does not allow pms. I would love to get his input on this issue as well.

Thanks again!

Ben

I think that this is generally accepted practice, based on the descriptions of the original Edison NiFe cells and experience with the ChangHong batteries as well. I can't say for sure whether there is a specific mention of this on the CH site.

The importance of the discharge/charge cycles is, as far as I know, that the batteries will not develop their full capacity and therefore will not respond to load tests as well as their nominal capacity would indicate until after some number of full cycles. Since normal RE operation will not discharge the batteries to a low SOC, this has to be done deliberately. Whether going straight into shallow discharge use instead will have any long term negative effect on the batteries is a question for which I do not have the answer.

If Mike does not see this and contact you, you may want to PM one of the Moderators and ask to have a message relayed to Mike. Other than that I do not know of any way to contact him.

[Sunking]

Wel here is one of those gray areas folks do not know or figure out. NiFe break in period are no different than LA batteries. They take 30 to 50 cycle to form the plates. Form is probable not a good term to use. The plates from the factory are smooth. It takes a several cycles to pit them which increases the surface area, thus increasing capacity.

But there is a catch. You need to discharge them down to 50%, then followed up by a good long deep charged. Guess what? No solar system can give you a nice long 12 to 24 hour charge. You even apply the intitial charge the battery requires as it is an EQ charge applied for 24 hours.

So here i go back and why I say if you have an off-grid battery system, you darn well had better have a good generator and AC charger as part of the system. One capable of providing a minimum C/10 charge rate. Otherwise your batteries are in trouble from the start.

[bjmccall]

Thanks inetdog and sunking for your replies!

My system is grid-intertied, so I certainly could use an AC charger instead. Can anyone recommend a suitable model? The only ones I am familiar with are the automotive-type, which don't seem to have high enough current, and also don't seem to want to charge a "dead" battery. One option I read about in an EV book is using a Variac (autotransformer) followed by a bridge rectifier to make a "poor man's" DC power supply with variable voltage...

[russ]

I passed your message to Mike - lets see when he can come around.

[bjmccall]

Thanks, Russ.

I've done a little more reading about the "poor man's" battery charger...the idea seems to be to use an autotransformer (Variac) to step-down line voltage to the desired level, and then run this through a diode bridge, which serves as a full-wave rectifier. This doesn't exactly provide DC, but rather an all-positive variable DC that varies at 120 Hz, since it's just the sine-wave half-cycles flipped around. Evidently the current is limited by the internal resistance of the batteries. This scheme seems to be used a lot with lead acid batteries, and the "pulsed" nature is reputed to be helpful for desulfating. But I have no idea if this would be acceptable for NiFe's...does anyone know?

Alternately, if anyone knows of a good source for a reasonably-priced DC power supply, I'd be game for that. But somehow I don't want to spend ~$500 for a fancy battery charger that I'll only use once (or a few times, if I cycle them).

[ursus_maritimus]

Thanks inetdog and sunking for your replies!

My system is grid-intertied, so I certainly could use an AC charger instead. Can anyone recommend a suitable model? The only ones I am familiar with are the automotive-type, which don't seem to have high enough current, and also don't seem to want to charge a "dead" battery. One option I read about in an EV book is using a Variac (autotransformer) followed by a bridge rectifier to make a "poor man's" DC power supply with variable voltage...

There are some relatively inexpensive American made chargers (IOTA). However, the original Edison manual PDFs ( Bulletin 850 X) that have been floating around the internet the past few years specify a constant current charge rather than a constant voltage charge.

I have puzzled about a few of the recommendations in these older publications vs new. This 850 X manual also suggests cells should not stand empty, while newer recommendations suggest that storage more than a year should be empty but sealed. Possibly a mistranslation from the original Chinese?

[Mike90250]

The cells generally are charged and tested at the factory, then drained. When I filled mine, they registered voltage, and the MPPT controller "woke up". I manually set to 48v, and and let the sun do the rest. It did take a couple days to fully charge them, and now with the cloudy weather here, when they do get low, I still run generator AM to boost the cells, and when the sun comes out, they are not so low, and complete the charge faster. I'd also set my bank up in the summer, with longer days, and fewer loads, winter, it's much harder to do.

Mike

[Sundetective]

There are some relatively inexpensive American made chargers (IOTA). However, the original Edison manual PDFs ( Bulletin 850 X) that have been floating around the internet the past few years specify a constant current charge rather than a constant voltage charge.

I have puzzled about a few of the recommendations in these older publications vs new. This 850 X manual also suggests cells should not stand empty, while newer recommendations suggest that storage more than a year should be empty but sealed. Possibly a mistranslation from the original Chinese?

'Original Chinese'.

4.6 The Storage of Batteries

Storage and maintenance of the batteries should meet the specified requirement so as to prolong their service life.

Long-time storage

If the battery is stored for a long time, it is advisable to screw the vent plug tightly in a discharged state.
To clean the external metal parts, coat them with Vaseline and store them in a dry, cool and well
ventilated room where the temperature is not higher than 25 , and where the relative humidity is not
℃ higher than 75%.

Short-time storage

A battery which is stored less than one year can be stored filled with electrolyte but in a discharged state.
Adjust the electrolyte level and firmly screw the vents before storing. Keep the battery in a dry, cool and well ventilated room where the temperature is not higher than 25℃.

1.5 Storage period:

Rechargeable battery can keep
the life time performance after storage for 4
years under the required storage conditions. If
new battery were stored over 4 years, please
carry out 3 to 5 charge and discharge cycles
before capacity inspection. If the capacity can
reach the nominal capacity and no rustiness, the
battery can be put in use.


Bill Blake