Smart Battery Monitor?

[a64pilot]

You have a point, I was thinking the airconditioner, but maybe on battery they do without?
I do know they do run on battery, they were doing that when I was in the Army and I think some enterprising people were actually using Honda generators strapped on the outside of them.
The 1700 SHP airplane that I have been testing for about the last two weeks, burns about 110 GPH at high power, maybe 70 or so at cruise, and at low idle burns 26 GPH, so turbines go through fuel at idle like it was free

[a64pilot]

I did find this, and saw a reference to the battery bank weighing 500 lbs, but nothing else.

Using a high power density 330 cc (20 in3) Wankel rotary engine modified to use diesel and military grade jet fuel, the Army's TARDEC developed a 220-pound (100 kg) Auxiliary Power Unit designed to fit into the M1 Abrams, replacing an existing battery pack that weighs about 500 pounds (230 kg). The new APU will also be more fuel efficient than the tank's main engine.[103] Testing of the first APUs began in 2009.

Then I found this, so they did have two banks for a total of 1,000 lbs of batteries.
Even a lead acid bank that weighs 1,000 lbs is a pretty large bank of batteries


And the Abrams apparently was designed with 1000lbs of batteries in two banks. The under-armor APU replaced one of the banks with a small diesel Wankel generator that was ~220lbs instead of 500lbs.

[Dockhead]

Originally Posted by a64pilot

I did find this, and saw a reference to the battery bank weighing 500 lbs, but nothing else.

Using a high power density 330 cc (20 in3) Wankel rotary engine modified to use diesel and military grade jet fuel, the Army's TARDEC developed a 220-pound (100 kg) Auxiliary Power Unit designed to fit into the M1 Abrams, replacing an existing battery pack that weighs about 500 pounds (230 kg). The new APU will also be more fuel efficient than the tank's main engine.[103] Testing of the first APUs began in 2009.

500 pounds of lead-acid batteries is nothing in a vehicle like that -- I have more than that on my boat.

It looks like from a bit of Googling that they're putting LiFePos in them now anyway?

[Littlechay]

Originally Posted by a64pilot

Only way I know of to tell if your bank is fully charged is to watch its acceptance rate at absorption voltage

exactly. Use a voltmeter on discharge and an ammeter (or preferably two one on the charge circuit and one on the load circuit) during charge. Then provided you know some basics you have the best battery monitor possible.

If on the other hand you don't know the basics; like many consumers; then use a monitor

[Littlechay]

Smartgauge has a lot of references to it's military supply contracts in the blurb on the various websites. However if anybody takes the fact that something has been supplied to and used by various military bodies around the world as evidence of a products usefulness then they would be deluding themselves.

Military supply contracts the world over have little to do with selecting the best product and more to do with going with what, and who, they know..

In my opinion anyway... puts kevlar on and dives into trench.

It's interesting to know that they are using certain devices as it suggests reasonable reliability but more importantly that the product is soldier-proof but not necessarily that it is the best product for the job. Apologies for the drift.

[Dockhead]

Originally Posted by Littlechay

Smartgauge has a lot of references to it's military supply contracts in the blurb on the various websites. However if anybody takes the fact that something has been supplied to and used by various military bodies around the world as evidence of a products usefulness then they would be deluding themselves.

Military supply contracts the world over have little to do with selecting the best product and more to do with going with what, and who, they know..

In my opinion anyway... puts kevlar on and dives into trench.

It's interesting to know that they are using certain devices as it suggests reasonable reliability but more importantly that the product is soldier-proof but not necessarily that it is the best product for the job. Apologies for the drift.

Not drift at all.

The military has bought tons of useless carp. The fact that the military uses any particular piece of gear for a use which might be very different from ours, carries zero water for me. The fact that someone like MaineSail uses some item of electrical gear, says 1,000,000x more, in my opinion.

But in any case, "X uses it", is not an answer to the questions "Does it work" or "How does it work?"

[a64pilot]

Originally Posted by Dockhead

500 pounds of lead-acid batteries is nothing in a vehicle like that -- I have more than that on my boat.

It looks like from a bit of Googling that they're putting LiFePos in them now anyway?

It was 1,000 lbs, but they are I believe used very similar to our boats, that is deep cycle the battery bank,and yes, I too would have expected LifePo or maybe Lithium Iron Phosphate for safety not lead acid.

You have read Maine Sail's article on the Smart Gauge haven't you?

[lateral]

Excellent thread! Thanks to all.
Acceptance rate at absorbtion for FLA should be 1-1.5% ??
What % did you use when you had them?(FLA's)

I guess depends when it "bottoms out" and no amount of charging is going to make any diff?

[a64pilot]

Acceptance rate will vary of course by SOC, starts out at charger max amps and tapers.
If your asking what is the acceptance rate at 100% SOC, best to contact manufacturer and ask, or in my opinion if you can't get an answer, then I would leave it in absorption voltage and eventually the charge rate will even out, and I would call just a tiny bit less than that as 100%.
I don't think you will kill a bank by leaving it in absorption for a few extra hours once, but I would check water level after doing that

[lateral]

Originally Posted by a64pilot

Acceptance rate will vary of course by SOC, starts out at charger max amps and tapers.
If your asking what is the acceptance rate at 100% SOC, best to contact manufacturer and ask, or in my opinion if you can't get an answer, then I would leave it in absorption voltage and eventually the charge rate will even out, and I would call just a tiny bit less than that as 100%.
I don't think you will kill a bank by leaving it in absorption for a few extra hours once, but I would check water level after doing that

Did just that and the result was not enlightening at all. He had never had the question asked before.
Unbelievable that they can import them and not be able to answer this simple question.

Let me see if I have this right:
At absorbtion phase, (constant voltage with decreasing current) as soc increases, current will tend to a point where it doesn't decrease anymore.
ie approaching 100% soc. And this will be approx. 1% of initial current flowing or 1% of total amphrs? Surely, the later?

[Stu Jackson]

Many of the points covered here are included in this thread:

Loaded Battery Voltage vs. SOC - AGM Lead Acid Battery by Maine Sail --- why using battery voltage as an indicator of battery SOC is something that requires thought & understanding.
Battery Voltage vs. State of Charge | SailboatOwners.com Forums


***********************

Maine Sail has also covered these issues quite thoroughly on his own website:

www.marinehowto.com

[lateral]

Couldn't find it in MS's articles.
Lee Hart sayes 2% of 20hr C.
Lee Hart's Lead-Acid Battery Charging Basics

Originally Posted by Stu Jackson

Many of the points covered here are included in this thread:

Loaded Battery Voltage vs. SOC - AGM Lead Acid Battery by Maine Sail --- why using battery voltage as an indicator of battery SOC is something that requires thought & understanding.
Battery Voltage vs. State of Charge | SailboatOwners.com Forums


***********************

Maine Sail has also covered these issues quite thoroughly on his own website:

www.marinehowto.com

[Stu Jackson]

Originally Posted by lateral

Couldn't find it in MS's articles.
Lee Hart says 2% of 20hr C.

If you'd scroll down to reply #13 in my previous link, the answer is there:

Your batteries can be considered full at 2A or less at 14.4V +..

That was for a 400 ah bank.

Reasonably consistent (close enough for folk music?!?), although MS continues to point out that the % charge in A should be at bulk voltage.

It's easy enough to do with a shorepower charger or even an alternator with external regulation. Just turn 'em off an have the process start over again at bulk voltage. Only takes a second.

[lateral]

Originally Posted by Stu Jackson

If you'd scroll down to reply #13 in my previous link, the answer is there:

Your batteries can be considered full at 2A or less at 14.4V +..

That was for a 400 ah bank.

Reasonably consistent (close enough for folk music?!?), although MS continues to point out that the % charge in A should be at bulk voltage.

It's easy enough to do with a shorepower charger or even an alternator with external regulation. Just turn 'em off an have the process start over again at bulk voltage. Only takes a second.

I saw that but was for AGM's so discounted it.

"% charge in A should be at (max)bulk voltage." (above)
Meaning that 2% of lee's, is not of 20hr Ahrs, but of Amps at initiation of absorbtion? Hence the 2amps instead of 8mps.

[Dockhead]

Originally Posted by Stu Jackson

Many of the points covered here are included in this thread:

Loaded Battery Voltage vs. SOC - AGM Lead Acid Battery by Maine Sail --- why using battery voltage as an indicator of battery SOC is something that requires thought & understanding.
Battery Voltage vs. State of Charge | SailboatOwners.com Forums


***********************

Maine Sail has also covered these issues quite thoroughly on his own website:

www.marinehowto.com

MaineSail is one of my personal heroes. There is more insightful information on his site than in any 10 books on my shelf. Instead of hype and verbiage, we get hard core technical information and actual testing from MaineSail.


The information about using voltage for SOC is really useful, as usual. Some people use the 20 hour discharge voltages, which is really dangerous, rather than the open circuit voltages.

Also, a small bank which you have to read at fairly high discharge rates as a percentage of C, is hard to evaluate using the voltage method.

It works much better if you have a larger bank which you can read while discharging at a rate low enough, that the voltages are close to the open circuit values. And by using ONLY the open circuit voltages, any errors will be on the harmless side. Using the 20 hour discharge rate values makes it likely you will have errors on the wrong side.

Also a good tip against using actual open circuit voltage. I don't know why the voltage would rebound to higher than the charts -- but MaineSail seems to have measured this phenomenon. Real life cruisers never use real open circuit readings because batteries when actually cruising are never left for that long with no load.

Also don't forget to correct for temperature.