Off Grid, alternate approach

[cranetruck]

With power outages popping up so often these days and so much talk about generators, I thought my solution may be of interest.
It is based on the ability of NiCd cells to take on a charge at a high rate, perhaps ten times that what's normal for Lead Acid types.

Going on two years now, my xm757 uses NiCd cells for starting and also has a 60 AH bank of cells to supply a 1KW pure sine wave inverter.

In a power outage emergency, the Nicads will supply power for lights and a TV or Computer for 10 hours or more. Not much perhaps, but the 100 amp 28V generator on the truck recharges the cells in less than an hour at high idle. This cycle can be repeated over and over without harm to the Nicad cells.

That's it in a nutshell, it works great, my only problem is that virtually all new inverters cut off at about 22VDC (to keep from harming lead acid batteries), while I'd like to see a cut-off of about 19 volts, which would be best for the Nicads.
Older non-computerized inverters will do that, so I'm still looking for one those, that would be a better match for my system.

 

[Metalflames]

Could you send me more specifics about your system. I am currently just starting out looking to building a comparable style system. What are the advantages of Nicad? How is the cot and availability?

 

[quickfarms]

Could you send me more specifics about your system. I am currently just starting out looking to building a comparable style system. What are the advantages of Nicad? How is the cot and availability?

Ditto

What is the efficiency of the inverter?

 

[Triple Jim]

I don't know who made your sine wave inverter, but I think I'd contact them and see if there's a circuit board pot you can adjust to change the voltage at which it does its low voltage shutdown. You're much better off with a modern inverter than the old transformer type that's much less efficient.

 

[o1951]

Could you post more specifics? What did the NICD pack cost?

 

[cranetruck]

I don't know who made your sine wave inverter, but I think I'd contact them and see if there's a circuit board pot you can adjust to change the voltage at which it does its low voltage shutdown. You're much better off with a modern inverter than the old transformer type that's much less efficient.

Did that and the tech that I spoke with said it couldn't be done...it probably can, but that was his answer.

 

[cranetruck]

Could you post more specifics? What did the NICD pack cost?

The Nicads are military surplus, "helicopter" batteries etc. They are made up of individual cells (BB600) and you can make up a battery bank at any suitable voltage and amp-hr capacity.
19 cells for a 24 volt system that works with the truck generator voltage for proper charging.
Cost may be $10 to $15/ea.

 

[cranetruck]

Could you send me more specifics about your system. I am currently just starting out looking to building a comparable style system. What are the advantages of Nicad? How is the cot and availability?

The advantages of the Nicad cells are high rate of charging, hundred or more amps if your charging system can supply it and the ability to handle deep cycle discharge without harm. In comparison, a lead acid battery will not regain full capacity after a deep discharge, some are better than others, but a typical starter battery will lose much of its capacity after only a few deep cycles. Yes gel cells are much better, but still nowhere near the performance of nicads.
Nicads have a life span counted in decades, not years, they have lower internal resistance for high cranking current when used for engine starting among other advantages.
If they weren't available as surplus, the cost would be prohibitive, a single new "aircraft" nicad battery costs about $2,000 (that's two thousand).

 

[Speedwoble]

My only issue with nicad is the toxicity when it comes to disposal(be sure to properly recycle them) and the memory effect, which is why I am guessing you would prefer to do a deeper discharge. NiMH don't have these disadvantages.

 

[cranetruck]

My only issue with nicad is the toxicity when it comes to disposal(be sure to properly recycle them) and the memory effect, which is why I am guessing you would prefer to do a deeper discharge. NiMH don't have these disadvantages.

The memory effect is taken care of by "flattening" the cells once a year or so, totally discharging them. With a proper inverter, the cells can be further discharged when used, preventing some of this effect.

The potassium hydroxide may be a harmful chemical, but so is sulfuric acid and my battery housings are vented to prevent build-up of hydrogen gas. The starter battery has forced air ventilation from the engine compartment.
If the nicads were not relatively safe, they wouldn't be used in aircraft and I have had zero problems after almost two years of use. Probably started the 8x8 50 times on the nicads.
There is a system in place for recycling nicads, just like for lead acid batteries.

 

[1 Patriot-of-many]

If only I had a spare xm757 lying around....

 

[o1951]

NiMH don't have these disadvantages.

I have smaller NIMH. They are far superior to NICD - I have not found any memory effect, take high charge rates, greater power density, and no failures in over 5 years of use.
However, the price would be prohibitive for this application - unless someone knows of a surplus source.

 

[camp9]

These are all relatively small batteries compared to the marine deep cell type? You'd have to hook a bunch of them up to get the same out of them?

 

[cranetruck]

These are all relatively small batteries compared to the marine deep cell type? You'd have to hook a bunch of them up to get the same out of them?

Like any other battery, you can stack them in parallel and or in series for any voltage and amp-hr capacity. The 38 cells that I have provides a total capacity 60 AH at 24 VDC nominal.
The starter battery has a 30AH capacity and has been plenty so far for the LDS465-2 engine. Accessories, like the fuel burning heaters run off the "house" battery, so that the starter battery never runs down.
The image attached shows a 12 Volt NiCd battery used by the military and is the same size as the 6TL lead acid type. It's has a 70AH capacity.

 

[Kohburn]

checked the net quickly but didn't see a ready source for these. trade secret? or care to pass along a source?

I have a 150 amp alternator i plan to install for my 5kw inverter, but want to get the battery bank figured out first.

 

[cranetruck]

Search for BB600 cells, they are used to "build" the batteries. Don't know any particular source, but popular with people making electric car conversions...
This handbook is a "must have" IMHO.