12 volt NiMh ships battery anyone ?

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Blueboatman

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Does anyone out there have any knowledge as to how near the industry is to delivering a NiMh (Nickel metal Hydryde) replacement for the lead acid ships battery ?
This post inspired by Shipswoofy earlier today querying the merits of NiCad/Dry cell/NiMh for torch batteries . How soon before we can finally consign the cosseted,heavy,leaky,fussy and self-destructive lead acid jobby to the recycler.Anyone know?
 
I have used NiCad wet batteries in my boat for 23 years. I came from the aircraft industry and these were rejects. They come as individual cells rated at about 14 AH. They are about half the weight of lead acid and while they have a low AH rating you can suck em dry and they hold the voltage until very near the end. So they have an equivalent of at least double the rated AH compared to lead acid.
Charging can be tricky if you have a high current regulated voltage charger as in engine alternator. In aircraft they are charged in this manner however. NiCad and possibly NiMh have a nasty knack that when they get hot the voltage actually falls. This can then increase current to increase heat you get a thermal run away. You really need a temperature sensor to guard against this possibility. Mine are charged from a small solar panel 2w which has no chance of overcharging or cooking the batteries. In fact it takes about 2weeks to recover from a night sail.
In aircraft at a max every 6 months the NiCad batteries are fully discharged. (deep cycled) A short across each cell for several hours before recharging. In fact some chargers discharge again with an AH test. This is called deep cycling. The same 14AH cells are required to deliver close to 1000A for about 10 seconds to get a small gas turbine up to ligh up speed. Any poor performance of the battery results in a hot start which can destroy the turbine so battery performance is critical. After a start they recharge initially at over 100 amps for a few minutes. They thrive on abuse. One thing about the NiCad is their inncredibly long life. This is especially so if you replace individual cells. The first one I had went for 15 years without any problem. Then one cell failed and I havn't been able to get a replacement so have gone to a different size (smaller).
It has occured to me that NiMh D cells are claimed to be 9 AH which could be adequate for some sailing styles (like mine) However this would be a fairly expensive option for 10 cells in a bank and 2 banks. It would go well with solar only charging. I doubt they would start a diesel.
NiCads (wet) are also used by electrical suppliers for emergency power and possibly other industries. One manufacturer is SAFT. It is not likely hower that it would be economical for you to buy new.

Just a few thoughts olewill
 
To quote one battery specialist (can't recall the name)

"The replacement for the lead acid battery is about 10 years away -- and it always will be."

Nothing gives you bang for buck like lead acid -- the AGM referred to in the other post is "dry" but its still lead acid technolgy -- lead between sheets of acid soaked glass matting I think

As others have said charging regiments for Nickel based technologies are tricky and require very smart voltage regulation and sensing.

All the best

Nick
 
You have just solved a problem for me. The boat I am currently refitting for an owner has 36 of these cells to make two banks of 24v. I will now throw out the truck battery charger installed by owner and replace it with a proper one.

I wondered why they kept boiling, indeed on first

inspection they needed 35 yes 35 litres of water

and they are heavy but the boat weighs36tons so not a problem unless you have to move them all to clean and paint.
 
Hey stop Boatbuilder. NiCad cells are always 1.2 volts so there is usually 10 to make 12 vollts. (or min. 40 to make 2x 24v banks) Obviously you have individual cell lead acid at 2 volts per cell 6 to make 12volts 12 to make 24 volts actually it sounds like 3 banks of 24 volt. The other differeence is that Nicad have an electrolyte of a mild alkyline while lead acid have dilute sulphuric acid. So they should never be mixed or even charged in the same area.
As for truck charger versus "proper one" It won't make any difference if they are NiCad as the charging regime is different so auto chargers are not so good. I would keep the truck charger for NiCad just remember to turn it off. If as I suspect you have lead acid batteries then the truck charger will boil them dry if you don't turn it off after estimating they have had enough. The proper charger will do it automatically)
Just by the way NiCad wet cells actually make water when being charged so you always check the water level at fully charged and it falls a little on discharge. Obviously however if you overcharge they also boil the water away. regards olewill
 
My electric push-bike (here) has NimH batteries (36 volt). Until recently bikes like this (and some still do) always used lead-acid batteries. I would be surprised if it was 10 years before a boat version was developed. Look how fast ni-cad developed when they became mainstream.
 
Is ALKAD not a manufacturer rather than a type of battery?
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"Artificial intelligence is no match for natural stupidity"
 
I have talked with both Alcad and Industrial battery supplies 01527 559255 and they confirm cells are ntcad and 1.2v .They also say that it is their common practice to only have 18 cells to a bank even though that does not add up to 24 . each cell is 190ah and will cost £190+vat to replace
 
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