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Saft NiCad Batteries
By bapayton, Section Storage Posted on Thu Apr 10th, 2008 at 03:24:57 AM MST
Questions on freebie batteries

Hello everyone!
This is my first post so I hope I don't sound to ridiculous. Isn't that a rite of passage on a message board? Anyhow, I have a friend who has given me an out of spec (for the aircraft industry) Saft 4076 NiCd battery and I was going to ask everyone their opinion of it's usefulness. I should be able to obtain more of them in time. What I'm wanting to do is to power a few (maybe 4- 13 watt) CFL's in a cabin and a small TV (for football games) so I can eliminate the lighting and entertainment part of grid connection (gotta stay somewhat grid connected for A/C reasons). Everything else will be propane (water heater and fridge). I planned on connecting them as multiple 12 volt strings and charging with solar panels. Since the cabin won't be used but maybe once a month for a few days what kind of overall battery capacity would I need and how many watts of solar to keep them up during the away times? I'll attempt to attach some pictures but I'm not sure it will work.
Here are some specs from the manufacturer:
Saft 4076 NiCad
Electrical caracteristics
Nominal voltage- 24 volts
Nominal capacity- 36 Ah at 1 hour rate
Power rating- (12V-15s-23°C/70°F)
Recommended constant charging voltage- 28.5 volts
There are 20 individual 1.5v cells connected with bus bars.

Link to Battery Label

Fixed the battery picture so it displayed and linked to the photo of the label. TW

Saft NiCad Batteries | 18 comments (18 topical, 0 editorial)

Re: Saft NiCad Batteries (3.00 / 0) (#1)
by wpowokal on Thu Apr 10th, 2008 at 04:55:35 AM MST
(User Info)

Welcome Bapayton,
I'm not going to calculate your solar requirements, just to say welcome, grab all the batteries you can and congratulation for surviving on the board this far.

allan down under
A life lived in fear is a life half lived.

Re: Saft NiCad Batteries (3.00 / 0) (#2)
by warpsta on Thu Apr 10th, 2008 at 05:25:49 AM MST
(User Info)

These batteries are great garb as many as you can, however you have to be nice to them. They must be treated differently to your standard lead acid type battery.

Here is a link for you: http://en.wikipedia.org/wiki/Nickel-cadmium_battery_vented_cell_type

Re: Saft NiCad Batteries (3.00 / 0) (#3)
by wdyasq on Thu Apr 10th, 2008 at 05:54:26 AM MST
(User Info)

I don't understand how you are going to use 28V batteries for 12V devices from your post but, hey - it's your project.

Good find,

Ron
Adventure is just bad planning." -- Roald Amundsen

Re: Saft NiCad Batteries (3.00 / 0) (#4)
by Jeff (ruralmcguyver at yahoo dot com) on Thu Apr 10th, 2008 at 07:55:32 AM MST
(User Info)

Pretty sweet deal! Since they are hooked up in series, that must mean they are 1.5 volt, 36Ah each. So...9 of them in series will give you 13.5 volts, and 36Ah. That gives you enough left over to make another string of 9 in series. Hook those two banks of 9 together in paralell, and you should get about 72Ah! That's a good start on powering the lights & TV you mentioned. If those lights and TV are 12v, it would be a big plus, otherwise you'll have to get an inverter to get 110/120v AC. Like others have mentioned on this board, a good "bang for the buck" starter set of solar panels can be had from Harbor Freight for about $200. I try to keep this board posted whenever they have their frequent sales on these panels. They're 45 watt, and even come with 2 CFL's (12v!). Just search the board for 45w, or Harbor Freight, and you'll find several topics on them.
Lucky catch!
Rural McG

Re: Saft NiCad Batteries (3.00 / 0) (#5)
by Jeff (ruralmcguyver at yahoo dot com) on Thu Apr 10th, 2008 at 08:10:23 AM MST
(User Info)

Here's a couple links to the posts on those HF panels I mentioned:

http://www.fieldlines.com/story/2007/10/24/31845/824

http://www.fieldlines.com/story/2007/10/4/153940/647
Rural McG

Re: Saft NiCad Batteries (3.00 / 0) (#6)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Thu Apr 10th, 2008 at 09:09:23 AM MST
(User Info)

Talk about being lucky!! How do I bribe you for one of those :-)
Where are you located:-)
Okay, batts.
1.)NiCds ae 1.25 standing voltage not the normal 1.5 like Alkalines and Lead-Acid.
So the best thing to do would be like rualmcguyver said, link up 10 of the 20 in series then hook the 2 sets up in parallel.
This will give you a full 72Ahr of usage.

)NiCds, wet or dry can withstand a deeper drain on them than Lead-Acid, so that's also a plus!
) NiCds are current lovers and need to be charged using a constant current instead of constant voltage like most chargers will do.
) they'll need to be charged in values of 10, i.e. C/10 is a good value to charge them. C=the total amerage of a string so at 36Ah you'll not want to charge these at more than 3.6Ah for the total string C/20 is better.
) NiCds like Lead-Acid need to be able to vent, for the same reason, i.e. pressure build up. The lid I see in the back ground is metal and probably okay for previous use, but a plastic one with a bit more room would be better.

The HF PV is a good starter unit, the newer one much better than the old one.
It's max out put is 45 watts on a good day, which is way low for charging this pack fully.
you could have a pack of more than 900 watts total the HF puts out 45 watts total.
That's about 20% which would be okay for mantaining them but possibly not for a good deep charge. Since you're going to be using these once in a while it might be okay, larger unit would better, along with a NiCd specific charger.
There's a ton of charger circuits on the web if you want to build one, even ones specific for solar use.

IF you have a little more money to spend, it would be good to get a real solar controller than the one that comes with the HF set, I did.
I know this is long ;
Hope it helps
Bruce S

Re: Saft NiCad Batteries (3.00 / 0) (#11)
by joestue on Sat Apr 12th, 2008 at 06:08:09 AM MST
(User Info)

NiCds love a fast charge. About 1C or half that is good. Read the Wikipedia page about them.

(yes I know this is a storage application and that's impossible)

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#13)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Mon Apr 14th, 2008 at 08:32:54 AM MST
(User Info)

fast Charge! not totaly correct.
They CAN take a fast charge, but you wouldn't want to do that very often. When done this way they get HOT! real HOT! , this would lead to venting and unlike Lead-Acid you can't just add acid back in.
I had at one time a picture on sub-c's that were charged and I forgot to put the temp sensor on them to shut down if they overheated, wasn't pretty.. If its not there I can put it backup.

building with a C10 or even better C20 charge would give the longest use of these and then once in a while hit them with a C1 just to wake up the wiskers :-)
Wikpedia is very good at giving a global overview, but would be best to find an manufacturer and ask for specifics.

Still waiting to hear what Bribe is needed to get one of these:-<>..
Cheers
Bruce S

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#14)
by joestue on Wed Apr 16th, 2008 at 12:09:15 AM MST
(User Info)

The Devil is in the details man!

You should never charge a sub C or D battery that hard because you can't add water.

Correct me if i'm wrong, most of the heat is from the recombination of the O2 and H2 during the charge, since the amount of reconbination is the same whether you charge it fast or slow, (within reason, the increased voltage due to cell resistance will increase gasification), the small chargers just assume that if you keep the temperature down, then the internal cell pressure can't be high enough to vent the cell. With vented cell types, there is an order of magnitude less recombination.

Also, the battery should cool upon charging, until it hits end of charge and the oxygen is consumed in the catalyst.
This is not necessarily the case for all batteries, the internal resistance varies considerably between manufacturers, for instance, some Nicds can discharge 50C, others are rated only 10C or less.
http://www.mpoweruk.com/nicad.htm
www.battcon.com/PapersFinal2005/MeisnerPaper2005.pdf

BTW Nimh chemistry is 66% chemically efficient on charge, and Nicd is ~55% on a 16 hour charge, and ~80% on a fast, ~2 hour charge. Both of which lead acid can beat.

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#15)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Mon Apr 21st, 2008 at 11:45:23 AM MST
(User Info)

Joe;
I like your numbers. The C/10 or C/20 would give a good long term charge for what he's wanting to do.
Lead Acid batts are good. My main reason for sticking with NiCds are that they can be drained down to having only 20% of their total charge left and be able to recover without a noticeable damage. In fact , they work better when used in this fashion.

When building or designing for NiCds the best way would be to use the negative slope method. NiMh have this slope too, but not as easy to detect.

Cheers
Bruce S

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#16)
by joestue on Mon Apr 21st, 2008 at 02:41:20 PM MST
(User Info)

I forgot about the 80% discharge part, thanks for catching that.

If you only discharge the first 40%, I bet you could get the efficiency up.
This doesn't apply to NIMH though, speaking of which why do they put these in hybrids?
they should use NiCds.

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#17)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Tue Apr 22nd, 2008 at 03:26:47 PM MST
(User Info)

joestue
The main reason for them using the NiMh is the chemistry. They are way less dangerous. Cadnimum is a very bad thing, and MUST always be handled like the poison it is. Worse than lead paint!!
NiMh also loose their standing charge slower than NiCds do.
But possibly the more important reason is that they only last about 500 cycles before they start wearing out :-)
Lithimum is coming along just fine, once those have been around a bunch more years, they'll be better in the long run.
Price is what keeps them out of my reach.

Cheers
Bruce S

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#7)
by mettleramiel on Thu Apr 10th, 2008 at 09:09:52 AM MST
(User Info)

In order to tell you how many solar panels you need, we need to know how much power you are going to be using. For a rough, but effective estimate, find the wattage rating of your TV, it will be on the back. Multiply that by how many hours you plan to run the TV. Then multiply the total watts of your lights and multiply that by how many hours you plan on running them. Add these two totals together and you get your total watthours needed per average day.

So, lets say you have a 50w TV and you want to use it for 2 hours.
50w x 2h = 100watth

Then you have 4 12w light bulbs that you run for 3 hours.
4 x 12w x 3h = 144watth

Add them up

100wh + 144wh = 244watthours

Now we need batteries to run all of this. Assuming that everything is 12v we need at least 244 watthours worth every day, but you should always have much more than your daily allowance in order to keep your batteries in good shape.

224watthours / 12v = 18.7ah

Seeing that we need about 19ah, that 75ah battery you have would be an ideal start.

Now, as for the panels. My experience is that when everything is added up, I get roughly 4-5 hours a day of rated wattage of my panels. So,

224 / 5h = 44.8

If you have a good source of sunlight, 50 watts of solar should recharge your battery each day. I would advise you, however, not to get those garbage HF panels. They are cheap because, well, they are cheap. Thin film panels are tempting because of their initial low cost, but deteriorate quickly and my own have rarely ever seen 1/2 their rated wattage.

Re: Saft NiCad Batteries (3.00 / 0) (#8)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Thu Apr 10th, 2008 at 09:22:46 AM MST
(User Info)

I like your numbers but disagree on the HF panels. I've had mine for well over a year and have not had any problems. The controller on the other hand was only good for the power taps AFTER I fix it.

I disagree that they are garbage, in the winter I've seen more than their ratings.
It is possible you got a bad batch. Another long time poster (NothingToLose) has gotten bad ones and merely had them replaced.

Cheers;

Bruce S

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#9)
by mettleramiel on Thu Apr 10th, 2008 at 03:46:30 PM MST
(User Info)

I've never used the HF brand ones myself, but I have used 2 different brands of 15wat amorphorous panels. Motomaster and some other one I can't remember right now. I have 4 panels in total now and both of the brands have given me low power output that has slowly dwindled over the last couple of years. They started out close to rated, about 70-80% which was fine, but droped months later and never recovered.

Maybe the HF ones are of higher quality than this? I was just making a generalization based on my own experience and others who have experienced similar results.

Myself, I just got a 30w crystaline panel and am MUCH happier with my array now.

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#10)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Fri Apr 11th, 2008 at 11:42:16 AM MST
(User Info)

Cool;
Sorry to hear about those others, gives all of them a bad name , kinda like a a bad sales man:-)
Maybe those others can be used to trickle charge AAs?
The worst part of the HFs was the early controller, it sucked at best and when wooferhound got his it shorted the 3,6,9 volt outputs!! I quickly checked all the ones around the neighbourhood and sure enough other had the same problems. I basically pulled the stuff out and resoldered them, then used the noisy speaker as an ouput for a dump load controller from the famous dozen-aire (Ghurd) :-)

Hope I wasn't too rude:-)

Cheers
Bruce

[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#12)
by Jeff (ruralmcguyver at yahoo dot com) on Sun Apr 13th, 2008 at 09:22:52 AM MST
(User Info)

I forgot about those NiCad's being closer to 1.25volts, so the bank you'd want to set up would need to be 11 of those in series (13.75 volts). I say this because most controllers, and 12v systems for that matter, are made to charge at 13.5-14.4volts.

As far as solar panels, amorphorous panels will probably never compare to poly-, or mono crystaline panels. I mentioned the HF ones for "starter" purposes, they matched almost exactly wattage-wise the charging you'd need for what you have, and I'm familiar with them (have a set). I've had them about 17 months now & no problems (except the crappy controller). In fact, I'm very close to getting them on a new "tower" on a semi-automatic 2-axis tracking mount! Hopefully within a week if everything goes right. Wish I had a working camera to post pics, but that "fix-it" job is way down on the to-do list!
Rural McG
[ Parent ]

Re: Saft NiCad Batteries (3.00 / 0) (#18)
by independent on Tue Apr 29th, 2008 at 06:14:27 PM MST
(User Info)

10 standard nicads to make a 12v pack. 20 to make 24v although some use 19 in that case because of the high charged voltage. Goes over 15.3v, which I believe is the standard cutoff for inverters (inverters will shutdown above this voltage), when full for 10 pack in series.

There are ghurd's controllers if you need a fine grain approach to charge control (adjustable dump load controllers). Also, the better quality charge controllers have a charge cutoff which is variable. I would be hesitant using a charge controller which isn't made (or modified) for use with nicads. An adjustable constant current constant voltage power supply, used for electronics, would be better than a cheapie lead acid charger. If you had one of these, not only could charge them in a pack, but you could test each cell individually with controlled charges and discharges (using a large resistor) and match the similar capacity ones in strings (if you were doing 12v)

Those cells look alot like the bb600 spec ones EV people are using in their cars. There's even a yahoo group dedicated to them..

On the fieldlines (this) site is maybe some of the best info on wet cell nicads (on the whole web) if you want to search you will find the good stuff. Maybe search using google instead of the in built search function as it works better. Some of the info posted above is not very accurate to the care and attention these cells deserve. As looked after they should last a long time. Just don't keep them in the same company as PbA batteries!

[ Parent ]

Saft NiCad Batteries | 18 comments (18 topical, 0 editorial)

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