Wet-Cell NiCd Batteries

[S&S]

I'm looking at going to a "wet cell" NiCd system for the house bank and was wondering if anyone here has made the switch from Lead-Acid to NiCd and has any tips or experiences.

Any links or info on Charge acceptance rates, charging and float voltages and state of charge sensing would be very helpful.
Thanks!

S&S

[Pblais]

I'm looking at going to a "wet cell" NiCd system for the house bank and was wondering if anyone here has made the switch from Lead-Acid to NiCd and has any tips or experiences.

I'm not aware of any system that is set up for NiCD. Have you?

[S&S]

Originally Posted by Pblais

I'm not aware of any system that is set up for NiCD. Have you?

I'm not sure what you mean by "system". 10 cells will put out 12V nominal though.

[Wotname]

Unless you already have experience with NiCad technology, look very carefully at it's potential problems (and expense). They need regular servicing and they are not a "get and forget" system. You should remove any FLA batteries from boat if you go NiCad.

[Pblais]

10 cells will put out 12V nominal though

At what capacity? I have a NiCD solar backup vent and it works great, but it can't run a fridge or an auto pilot or my windlass. I'm not sure how you'll make a regulator to charge it either. None of the commercial marine chargers support NiCD.

[S&S]

Originally Posted by Pblais

At what capacity? I have a NiCD solar backup vent and it works great, but it can't run a fridge or an auto pilot or my windlass. I'm not sure how you'll make a regulator to charge it either. None of the commercial marine chargers support NiCD.

As Wotname noted, these are a different animal from the little NiCd's in a solar vent. These are available at up to 1500 Ah per cell.

I'm looking at these Hoeppike cells that have extended service intervals. They have catylitic recombiners for the H2 and O2.



As to chargers, That's what I'm trying to figure out. They can be charged at as high as 1.6 V/cell so I think I can program a Balmar regulator to get that, as to line chargers, the battery manufacturers all supply them . I still don't know the charging profile (but I know it's very different from Lead Acid).

[witzgall]

Before you go that route, look into LIFEPO4 technology. They can be had for $1.05 per AH @3.2v. see www.evcomponents.com for some ideas.

Chris

[S&S]

Originally Posted by witzgall

Before you go that route, look into LIFEPO4 technology. They can be had for $1.05 per AH @3.2v. see www.evcomponents.com for some ideas.

Chris

Thanks! looks interesting.
Are these able to be fast charged? That's what killed LiMH (saft) batteries for me. Those don't like fast charging or deep cycling.

[Wotname]

First of all I am NOT a NiCad expert but I am familiar with them as pertains to aviation use.
My view:
Pros - they have a very long service life - if correctly maintained; they can be very deeply discharged without ill effect; they maintain a very stable voltage during high current discharge and until almost fully discharged; they can be repaired (i.e. dead cells replaced); they have more capacity per size than FLA.

Cons - they are very very expensive; they don't like high charge rates (but can accept very high charge rates for a short time; they can suffer from thermal runaway and can be quite dangerous; they require regular servicing to maintain life and full capacity.

Having said that, most aircraft charging systems are basic and NiCads are usually charged at 1.7 V per cell. They will accept whatever current is available (depending on their state of discharge but they can be damaged if charged at this rate when deeply discharged. In theory, they only need recharging after a start so discharge is not high, therefore charge rate is not too high from a basic regulator, the rest of the time they are floated. And they are regularly serviced by being completely discharged to zero capacity and then recharged at controlled current rates.

I am not sure of the advantages to be gained by using them as a house battery (even if you have access to a smart current controlled charging system on board).

[witzgall]

LIFERPO4 are safe, can be charged and discharged at high rates (some, not all, look at the specs of cells you are interested in), and have a typical 2000 cycle life to 80% DOD.

They need to be managed with a electronic battery management system, to prevent over and under charging. THe BMS also balences the cells, to keep them in line with each other in regards to voltage.

Charging by multiple sources has not been clearly ironed out in my opinion yet.

I have a 24v 40ah pack I am working on to power our Torqeedo. Stay tuned.

Chris

[S&S]

Originally Posted by Wotname

First of all I am NOT a NiCad expert but I am familiar with them as pertains to aviation use.
My view:
Pros - they have a very long service life - if correctly maintained; they can be very deeply discharged without ill effect; they maintain a very stable voltage during high current discharge and until almost fully discharged; they can be repaired (i.e. dead cells replaced); they have more capacity per size than FLA.

Cons - they are very very expensive; they don't like high charge rates (but can accept very high charge rates for a short time; they can suffer from thermal runaway and can be quite dangerous; they require regular servicing to maintain life and full capacity.

Having said that, most aircraft charging systems are basic and NiCads are usually charged at 1.7 V per cell. They will accept whatever current is available (depending on their state of discharge but they can be damaged if charged at this rate when deeply discharged. In theory, they only need recharging after a start so discharge is not high, therefore charge rate is not too high from a basic regulator, the rest of the time they are floated. And they are regularly serviced by being completely discharged to zero capacity and then recharged at controlled current rates.

I am not sure of the advantages to be gained by using them as a house battery (even if you have access to a smart current controlled charging system on board).

VLRA's can runaway too so it's just not the chemistry. I looked into thermal runaway in aircraft and it seems like something that's detectable with a temp probe. In your experience is this something that happens when float charging only? ( that's what the cite's seemed to indicate).
What the manf'r. told me is that these (NiCd) can take an input current equal to the capacity of the bank (1C) which is more than my Balmar could deliver.
They didn't mention complete discharge (except for storage) as part of regular maintenance- could you tell me more about that?

The advantage I see is a short recharge time and a greater DOD. ( and they're not as picky as LI or some other chemistries).

witzgall-
I must be missing something on the site but it seemed that the recharge rate was pretty slow (.25C or less) I'll look again and let me know how yours work.

[S&S]

Chris-
How do you control the output voltage? (it's 2.5 to 4V per cell!) I don't know how 24v stuff runs on 40V ( probably not too well)

Dc/DC converter?

[witzgall]

S&S,

Look at this

http://www.thunder-sky.com/pdf/2008926101921.pdf spec sheet., for a Thudersky 200ah cell. Four of these could be used to make a 12v pack. The max charge rate is 3c.

Chris

[S&S]

Originally Posted by witzgall

S&S,

Look at this

http://www.thunder-sky.com/pdf/2008926101921.pdf spec sheet., for a Thudersky 200ah cell. Four of these could be used to make a 12v pack. The max charge rate is 3c.

Chris

Cool! The "no electrolyte slopping around" may make this a winner! I'll have to give them a call.
Thanks!

[S&S]

Talked to evcomponents and looks like it should work if I can get the BMS to talk to my regulator. This may be worth being a "guinea pig" : 150% of the ampacity at 1/2 the weight.

Thank You Chris!