I've got a few of Alcad's big wet NiCads, those 11 AH per cell jobbies.
Having a huge problem, actually, getting a decent charge INTO them from a lead-acid battery charger, an IOTA 55, actually.
It starts out well, but dwindles down when the battery voltage hits around 14, and no, there is no audible bubbling in the batteries, so they aren't fully charged, but the IOTAs output is down to 3-5 amps within twenty or thirty minutes (charging six 10-cell banks).

Now, one of those old "hippie" solar guys told me that with Nicads, you don't need a charge controller because even if you get them up to fifteen or so volts, you aren't overcharging them, which, doing the math, is probably right.

So, if I throw a couple of 12V panels on, say, 200w total, does anyone know from experience if I really need a charge controller?

I'm a bit dubious of the "hippie" because he also doesn't believe in blocking diodes, saying that they cause more charge loss by slowing down the input than they'd save keeping the batteries from backflowing at night...

Cap'n Jack

Hi Cap'n Jack,

The hippie is partially right, blocking diodes lose more power than they save most of the time.

14V is a little low for the Alcads. 14.3V is about the minimum for a string of 10 cells.

Your first charge if they haven't been used for 6 months would be about 30 hours with a current limit of about 2.2A and a voltage limit of 16.5V (per string).

Do you have the model number? I could give you better info from that.

Do the cells have a layer of oil on top of the electrolyte?

What is their age?

> The hippy is partially right, blocking diodes lose more power than they
> save most of the time.

Well, cool. When, then, is the time that they're worth it?

> 14V is a little low for the Alcads. 14.3V is about the minimum for a string
> of 10 cells.

Yeah, no kidding! I'm probably skimming, I'd bet, only about ten or twenty percent of their actual use! I did have them configured for 24V before, and could easily charge them to 29+... and then my 24V inverter died (an old "U" series) so I had to drop down to 12 for the interim until I got the pennies together for an FX.

> Your first charge if they haven't been used for 6 months would be about
> 30 hours with a current limit of about 2.2A and a voltage limit of 16.5V
> (per string).

I *have* been using them, but obviously, not well. Your suggestions confirm my suspicion that they need a slow steady charge over time instead of a hard fast one from the IOTA. In a couple of weeks, I'll have a windmill tied in as well, and that, too, should give a nice steady low charge. But like I was saying, I was thinking of putting a 80 watt or so panel on, which would be in the 4-5 amp range at 16V or so for a slow steady buildup. That seems right, then, to you?

> Do you have the model number? I could give you better info from that.

Still tracking that down. They *are* AlCads, this I know, but they don't look much like the batteries on their page. They were military builds, about six or eight inches square, about 19 inches high, in stainless steel housing, crated five to a "stick". The guy I got them off of said they were 11 AH each cell. The thing that doesn't match with AlCad is that they have FOUR posts, two pos, two neg, with one central vent.

> Do the cells have a layer of oil on top of the electrolyte?

No, they do not. Any suggestion as to type I should use?

> What is their age?

80's vintage, I understand. They were part of a large military complex around here, and many hundreds of them got dumped on the local "alternative" market when it got decommissioned. They are in use, by people VERY happy with them, all around this region... I'm the only one, though, currently, that is trying to charge them with a genny, though, not a PV or wind system, hence my problem.

Hi,

You only need diodes with some very leaky panels.

From the size of your cells, I would suspect they are 200 to 400 AH, not 11AH. Can you measure them closer?

If they have as high of capacity as I think they do, you can pump 20 to 50 amps into each string and maybe more. Can you charge them at that high of a current and then float them for a while at 15 volts?

A MPPT charge control would be helpfull to you if you could run a 24V array for a 12V battery or a 48V array with a 24V battery especially in hot weather since the voltage is a little higher than Lead Acid.

By the way, I run a string of Alcad LC105P cells (105AH) on one of my systems.

Ron

> You only need diodes with some very leaky panels.

Ah. Thanks!

> From the size of your cells, I would suspect they are 200 to 400 AH, not
> 11AH. Can you measure them closer?

Now, to make sure I'm describing them properly, I have forty individual cells of that size, that, I'm told, then totals 440 AH, making each individual cell 11 AH. It is not impossible that I was told incorrectly, as nobody seems to have paper on these things, one thing, as I was saying, I'm trying to chase down.

> If they have as high of capacity as I think they do, you can pump 20 to
> 50 amps into each string and maybe more. Can you charge them at that
> high of a current and then float them for a while at 15 volts?

That's my problem: with the IOTA charger, I can't GET them to 15v (or 30 in 24v configuration). While I was using them in the fall, before my U series died, yes, I could give them a good charge still at 30V.
But yes, when the voltage is down around 11v, I can put 50 amps in... until the voltage starts to climb, then the charger loses it.

> A MPPT charge control would be helpfull to you if you could run a 24V
> array for a 12V battery or a 48V array with a 24V battery especially in
> hot weather since the voltage is a little higher than Lead Acid.

Ok, I see what you mean. Hopefully, though, soon I won't have that problem as when I get the windmill up, it's 40V DC and I can charge the batteries, back in a twenty cell 24V configuration, with the two enermaxers I have; that was the setup with the guy who last owned this system.
My problem is that I currently (pardon the recurring pun can't get the juice in with a gas genny and the IOTA charger; it has a devil of a time putting just 14V into the batteries.

> By the way, I run a string of Alcad LC105P cells (105AH) on one of my
> systems.

Cool! With all the problems I've had with my system, and by god, there've been many, that has been my mantra: "When I finally have it together, the NiCads will have been worth it" .

I think you have 40 440AH cells. That would make a 48V 440AH bank (one string of 40 cells), a 24V 880AH bank (2 strings of 20 cells) or a 12V 1760AH bank (4 strings of 10 cells).

Is your IOTA charger the standard product or a higher voltage unit for nicads? Is the dual voltage plug inserted in the charger? If it is the standard unit, it is 13.6V without the plug and 14.2V with the plug.

It looks like you can hook your 80 W panel up directly for a while without harm even with the IOTA running.

> I think you have 40 440AH cells. That would make a 48V 440AH bank (one
> string of 40 cells), a 24V 880AH bank (2 strings of 20 cells) or a 12V
> 1760AH bank (4 strings of 10 cells).

Ron, that would make me a very happy boy indeed . I'll get those precise measurements for you. I could probably even arrange a digital pic if it would help!

> Is your IOTA charger the standard product or a higher voltage unit for
> nicads? Is the dual voltage plug inserted in the charger? If it is the
> standard unit, it is 13.6V without the plug and 14.2V with the plug.

An IOTA 55, brand new, and yes, I have the plug installed.
http://www.iotaengineering.com/dvjack.htm

I also have the smart controller, but don't use it.
http://www.iotaengineering.com/dls55.htm

So that's what's pooching me, then, isn't it? I just can't get enough voltage (and thus amperage) into my cells.

Just by the way, though, do you know of anyone who makes a commercial charger that spits out, say, 16v? One thing that Trace said in the manual for my U series is that in NiCads, people were often pleased with the results of dropping a 20 cell bank down to 19 to make a more lead-comparable bank 24V system, but that they didn't suggest dropping a cell from a 10 cell 12V system.

> It looks like you can hook your 80 W panel up directly for a while
> without harm even with the IOTA running.

Ok then! Thanks much!

Look closly at the cells, there might be a number stamped somewhere.

You have exactly the charger model that I thought you did. I would suggest calling or e-mailing IOTA to see if there is an internal adjustment to turn up the voltage for alkaline cells.

I wouldn't suggest running a 9 cell string. I don't really like a 19 cell string either.

An Outback Power inverter would work very well with your cells. The 24 V version will charge up to 33 volts with a maximum current of 85 amps for the vented version.

If you really want to experiment, I suppose you could get a surplus 2.5V 50 amp power supply and put it in series with your charger.

> Look closly at the cells, there might be a number stamped somewhere.

I will take a peek, but have never seen anything on them before...

> I would suggest calling or e-mailing IOTA to see if there is an internal
> adjustment to turn up the voltage for alkaline cells.

Ok, just did. I'll let you know what they say! I asked if a) they could tell me how to do it (I'm a licenced industrial mechanic specializing in instrumentation) or b) if I could send it back to them for THEM to do it, kick it up to a 15.5 or 16V output.

> An Outback Power inverter would work very well with you cells. The 24
> V version will charge up to 33 volts with a maximum current of 85 amps
> for the vented version.

Yep, I have fond dreams of the FX... I'll buy a few of them as soon as my bank account recovers .
What, incidentally, is the cut-out on the FX? I seem to remember it's about 10V?

> If you really want to experiment, I suppose you could get a surplus 2.5V
> 50 amp power supply and put it in series with your charger.

Depending on what IOTA says, yes, that might well be a plan...

Outback cutout is adjustable but can be as low as at least 10V on the 12V version.

I would not reccomend going with a 12V system unless you absolutly have to. 24V or 48V is much better most of the time. My big system is 12V but only because I only have 6 HUGH 2V cells. It has 2 parallel 500MCM cables for the battery run. 4/O cable looks downright puny next to it.