6TL Military Battery for Silent Power

coyotecoastmarine

Looking at the compact size of the 6TL at 11.25 X 10.5 X9 in. Most of these I found online show 215 AH ( U.S. Battery) for use on 125 Ft Schooner
Liberty Clipper, Have limited space in the battery room, with the theoretical power of an 8D lead acid is a much more compact size. Will be using a 3500 watt Outback
inverter/charger @ 24VDC. currently converting from 32VDC to 24 VDC, ( anyone need a pair of 6-71 Detroit Diesel 32VDC Starters???:) Has anyone used these batteries to success in off grid application, Charging will be provided by two separate gen-sets on board.
will only use it for basic house loads while sailing and quiet Dinners.

Thanks, Mike

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BB.

Re: 6TL Military Battery for Silent Power

Welcome to the forum Mike!

What are your expectations for powering your loads?

That is probably somewhere around a 120 AH at 12 volt battery? Are you looking at two of them for 24 volts? If so, Voltage adds when in series--AH only add when batteries connected in parallel... If you get 4 batteries, two in series, then two strings in parallel--perhaps ~240 AH @ 24 volts...

Are they available in Deep Cycle rather than as a starting battery? Starting batteries are not usually great for deep cycling (poor cycle life).

A 3.5 kW inverter on this relatively small battery bank--That is a lot of power. If the battery bank is capable for that amount of power--It would only last for around 1 hour before the battery is dead driving a 3,500 watt load.

There are other battery constructions/chemistry that would do better at high loads (such as AGM). But if you need more power, either you either need more lead acid batteries--Or consider something like LiFePo4 -- Higher energy density and lots of current...

Would this be a separate house bank, or will this also be used for engine starting, wheel house electronics (radio, communications, etc.)?

I am a little confused.

-Bill

coyotecoastmarine

Re: 6TL Military Battery for Silent Power

Going to be using 6,12VDC (6TL @ 210 amp hrs, 467 Peurkert # ) battery's in 2 separate banks for House Loads, Navigation and Start banks are independent of the 24 VDC system

Ease of access in the Battery room will allow maintenance to be done with LA battery's. Not enough room for 12 8Ds. These battery's are used by the military also for standby or silent in many pieces of equipment.

BB.

Re: 6TL Military Battery for Silent Power

Do you have a link to the batteries you are looking at... The only 20 Hour Rate I could find for 12 volt 6TL batteries were for ~100-120 AH. And perhaps you could get as high as 150 AH @ 12 volt for 20 hour rate (depends on weight/design of battery). I just don't see 210 AH.

See this link for a generic 6TL battery specification from the Department of the Army (hope link works--Google Books search results):

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Hmmm, you may be confusing the Reserve Capacity? I have seen 215 Minutes at 25 Amp discharge (25 amps at XXX minutes is "reserve capacity" definition"):

• 215 min / 60 min per hour = 3.6 hour
• 215 min * 1h/60 min * 25 amps = 90 AH @ 3.6 hour discharge rate

Also the Peukert number is usually in the range of ~1.1 to 1.25 or so--467 does not make sense.

What you could use from a 6TL battery (if they are true deep cycle--And I have my doubts):

• 6*120 AH * 12 volts * 0.50 recommended discharge (for long life) * 0.85 inverter efficiency = 3,672 Watt*Hours of "useful 120 VAC power" at 20 hour rate
• 3,672 * 1/10 hour discharge rate (to 50% of battery capacity) = 367.2 watt average load for 10 hours
• 6*120 AH * 12 volts * 1/2.5 max surge power * 0.85 inverter eff = 2,938 Watts maximum recommended surge current for Deep Cycle battery

Since the "average" high quality AC inverter can surge upwards of 2x it Watt (VA) rating, I would suggest that a ~2,000 watt maximum inverter would be about the largest I would suggest as "not being oversized" for your needs. Larger AC inverters can have higher losses (power they use just being "turned on" with no loads). This inverter is 20 watts "on" and 6 watts "search mode".

In some cases, you may want two inverters... A smaller one that is on 24x7 for smaller AC loads--And a larger one for running (for example) power tools.

For example, Exeltech has some nice 250-600 watt inverters that run ~6-9 watts Tare losses.

In any case--I am really not sure that you are looking at 6TL batteries that are true deep cycle designs (lots of MCA, CCA, and Reserve Capacity numbers--All associated with non-deep cycle batteries and no C/X and AH ratings usually seen with deep cycle batteries) . And if they are Starting or Marine batteries, you could be in for some unpleasant surprises when they get cycled:

Starting, Marine, or Deep-Cycle Batteries

Starting (sometimes called SLI, for starting, lighting, ignition) batteries are commonly used to start and run engines. Engine starters need a very large starting current for a very short time. Starting batteries have a large number of thin plates for maximum surface area. The plates are composed of a Lead "sponge", similar in appearance to a very fine foam sponge. This gives a very large surface area, but if deep cycled, this sponge will quickly be consumed and fall to the bottom of the cells. Automotive batteries will generally fail after 30-150 deep cycles if deep cycled, while they may last for thousands of cycles in normal starting use (2-5% discharge).

Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates - not sponge. This gives less surface area, thus less "instant" power like starting batteries need. Although these can be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle at about 50% discharge. Unfortunately, it is often impossible to tell what you are really buying in some of the discount stores or places that specialize in automotive batteries. The golf car battery is quite popular for small systems and RV's. The problem is that "golf car" refers to a size of battery case (commonly called GC-2, or T-105), not the type or construction - so the quality and construction of a golf car battery can vary considerably - ranging from the cheap off brand with thin plates up to true deep cycle brands, such as Crown, Deka, Trojan, etc. In general, you get what you pay for.

Marine batteries are usually a "hybrid", and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. It is often hard to tell what you are getting in a "marine" battery, but most are a hybrid. Starting batteries are usually rated at "CCA", or cold cranking amps, or "MCA", Marine cranking amps - the same as "CA". Any battery with the capacity shown in CA or MCA may or may not be a true deep-cycle battery. It is sometimes hard to tell, as the term deep cycle is often overused - we have even seen the term "deep cycle" used in automotive starting battery advertising. CA and MCA ratings are at 32 degrees F, while CCA is at zero degree F. Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open - not much of an option.

You might want to read about batteries here:

http://www.windsun.com/Batteries/Battery_FAQ.htm (above is a quote from this FAQ)
http://www.batteryfaq.org/
http://batteryuniversity.com/

-Bill

coyotecoastmarine

Re: 6TL Military Battery for Silent Power

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Thanks for all the info ! The 6TL sounded a little to good to be true. If you see the photo I do not have much room, but not opposed to building new battery boxes. The where originally had 4 8volt "Tractor Batterys" for a small house bank for mostly lighting and some navigation equipment that is long gone. I put in 4 US 8VGC-XC battery's and they are good lasting despite the Consta-Volt. I am looking to be able to run silent for 3 to 4 hours( under sail) and a few hours at anchor (Breakfast/Dinner)this season. Average house load is about 10 to 15
amps during sailing, I am going through the breaker panel and getting numbers I need. On Schooner Windy I ran two Outback 2500 Inverters Stacked on two banks of 6-4DGells @ 24VDC and it provided a full schedule of daysails (except if Crew forgot to turn off the 2 water heaters!!!) This only had one freshwater pump and new reefer and decent freezer
Clipper runs 2 Pressure Pumps (FreshWater/Seawater) I think I will base the beginning on a 2500 Outback inverter with options to expand later.
and it worked great

BB.

Re: 6TL Military Battery for Silent Power

I assuming this is your ship:

http://www.libertyfleet.com/boston-harbor-sailing/our-fleet/liberty-clipper
https://www.facebook.com/pages/Schooner-Liberty-Clipper/128590424883

Are you looking at two independent banks or one bank (house+ship)?

You have several ways to go... There are the Trojan batteries (various grades), Rolls/Surrette which have some very big cells, Fork Lift, and even AGM/Sealed.

The lower end products probably will last 3-5+ years, the higher end 10-15 years, and the forklift/traction motor types 15-20+ years.

The AGM--Not sure, but 3-6 years would be a first guest... And they are 2x as expensive as flooded cell types.

Flooded cell are usually going to be the most tolerant of over charging and >80% efficient. AGM are going to be the most efficient (>90% cycling efficiency) and no water levels to check and no venting during normal operation--very low self discharge. Forklift are going to be less efficient, use more distilled water, and higher self discharge, but will take very deep cycling (down to 20% state of charge) better than any of the other type of batteries).

With flooded cell you need to access the top of the battery bank to check/fill cells. With Sealed batteries, you can stack them with less concern for weekly/monthly access for servicing cells.

More or less, AH (and Watt*Hour) storage capacity is based on battery weight. More lead, more storage. You can make modifications to the basic design (add calcium to use less water, more/thinner plates for higher discharge current, and such).

AGM batteries are available that can discharge upwards of C*4 discharge rate (and some GELs too). Why they are good for UPS systems (computer backup power supplies--Just need 15 minutes to shut down servers/start diesel backup genset).

AGMs can also take high charging currents (but not too high of charging voltage). GELs (in general in the US) cannot take higher charging voltages or charging currents (C/20 or 5% rate of charge typical maximum). Means that you discharge GELs, you will need many hours of charging (at low current) to bring them backup.

Flooded cell batteries typically are charged at ~5% to 13% rate of charge (can go to 20-25% rate of charge--But you need to monitor battery temperatures closely). Flooded cell are probably happier at 10-13% rate of charge. AGM (if fast recharge is not important) are OK at 5%-13%.

Flooded cell batteries need recharging about once per month. Old forklift batteries probably need recharging 2-4x per month (higher self discharge, and higher self discharge when old). AGM can go 3 months between recharging (or more). More or less, you want to keep batteries charged (say >~75%) to reduce sulfation.

I am certainly no battery engineer--But I would start with your requirements (stored energy, surge current), access/density (sealed vs flooded cell)... And start looking at different "classes" of batteries and see which would meet your needs best.

Batteries are expensive to ship (AGM are not hazardous as they cannot leak/spill acid). So talking with a couple local battery distributes/engineers may be interesting.

So--What is most important to you?

-Bill