Mix and match AGM lifeline 4c's and 6c's

[Wingding]

I was just wondering. For you Alpine owners that have the problem with the close clearance of the first 2 batteries of the 6 because the chassis barely clears the first 2 posts, I was wondering if I could do something like this.

As you know it is two rows of 3 house batteries...

How about the closest 2 batteries to the chassis lifeline 4c's and the next 2 rows lifeline 6c's.....?
You might need to get a few longer battery cables to jump from the 9 1/2" height of lifeline 4c's to the 13" 6 c's.

I guess the big question is it feasible ? Can you mix a 220ah with 300ah battery?
If I do it this way, I would have a total of 1640ah vs 1320ah ..That's a difference of 320ah....
I would solve the clearance problem since you cannot fit lifeline 6c's in the first row by the chassis. But the second and third row should be no problem.
I cannot have the 1800ah {6 lifeline 6c's} but I can get alot more than 1320ah.
So what do you think? Can It be done this way and is a gain of 320 worth it for more of a boondocker?

[loranimal]

Remember if those are 6 volt batteries you can not add up the AH. Two 200 AH 6V batts only gives 200 AH at 12V.

[takepride]

And they must be of the same size/rating.

[Wingding]

Yes that is correct. My fault.... Dale did educate me on that over the phone..

Yes, one must combine the 2 6v batteries for 12v so if they are 220ah each it is 12v = 220ah not 440ah.. {I got to remember that!}

I just called lifeline to order batteries and told the guy I was wanting 2 4c's and 4 6 c's to combine but it will not work so give me 6 -4c's.....

He told me there is absolutely no problem having a combination of 2 4-c's and 4-6c's.............

So I didnt make the order.... Im stuck wondering what if any complications are there.....

Takepride, are you saying that all your house batteries must be exactly the same ah l...like if you buy a 300 ah they all have to be the same ah?

Sorry, just need to get this right cause I am trying to get the most ah possible... and there is simply no way without major work {welding up a new battery box} to fit 6 lifeline 6c's.

[wa8yxm]

So long as the batteries are all the same type (AGM Deep Cycle in this case) you can mix and match all you want. Batteries in parallel are truly socialist.

When charging one battery will indeed charge faster (If you measure amps) that being the larger battery.. and the smaller one slower

And when supplying power again the larger battery will supply more than the smaller

But if you measure charge as "percent of charge" Well, in the ti

In the time it takes the larger battery to go from 50 to 60 percent, the smaller battery will go from 50 to 60 percent as well. Provided you have good clean connections and cables big enough (Jumpers should be the same size as the service cables or larger)

So the "Oh they got to all be identical" folks.. Well, they are half right. This is not the case where they are right.

What you don't want to mix is different TYPES,, IE: flooded wet, maintenance free and AGM.

[dgerstel]

Winding,

This says it better than I would, from A battery website, pack referring to your house battery bank and chassis bank.

"Don't use two different chemistries when connecting a pack. Usually the voltages will be different, but more importantly the charge rates will be different and the capacities may be different, thus resulting in a shortened life span. - Try to match capacities as much as possible. When connecting batteries in a pack you should try to match the capacities as much as possible to avoid discharging one battery quicker than another. A pack operates at a combined voltage so your one cell that discharges quicker will likely discharge deeper than it may be able to recover from."

From Xantrex.

Consider the following recommendations for battery use.
• • •
Use only the deep discharge types for inverter applications.
Use the same battery type for all batteries in the bank.
Use only batteries from the same lot and date in your battery bank. This information is usually printed on a label located on the battery.

[wa8yxm]

Dgerstel.. Would you happen to have the URL for that website? Just so you know I am not trying to dispute what you said.. (IN fact save for you used different words it is exactly what I said in the post above it) I am just a bit surprised to find someone found a web site that supports what I say and want the cite so I can use it.

Thanks in advance

(But then you went on to "use batteries from the same lot"

This is safe advice, but it applies only to batteries in series. (IE: GC-2 size six volt) When you put 'em in series you wan't 'em identical.. (NOTE this applies only to each pair, the pair next to it can be older or newer, SO long as they are the same chemically (IE: Flooded wet cells) you can even mix six volt pairs and 12 volt singles, so long as they are the same chemically)

[ImagineIF]

Dale is correct. Although the last recommendation, "Use only batteries from the same lot and date in your battery bank. This information is usually printed on a label located on the battery" is overly restrictive. It's a good practice to have all batteries of the same age. Having an a mix of old and new will result in some batteries being over charged and some under charged.

Wingding, unless you do a lot of boondocking, you have more battery than you need anyway. I'm a bit surprised that your batteries are 13" tall. Trojan 105, that are very common are 10 11/16" tall and their largest T-106 is 11 1/2" tall. Maybe you can find a happy medium by changing batteries.

[wa8yxm]

Imagine... If all the batteries are connected in parallel, then unless you are pushing or sucking major amps they MUST, of necessity, all be at the exact same voltage.

Since for any given chemistry, State of charge determines voltage (Along with a few other things.. But at rest it's just SOC) HOW can one battery in the set be at a different SOC than the others? How can one be "Undercharged" it very simply can not happen.

What can and does happen is socialism.. That is an older, slightly weaker, battery does not deliver as much current as the newer stronger battery... But the state of charge.. Will always be identical across the deck. Can not be otherwise.

With batteries in series.. None of the above is true.

[RocketDork]

First, clean your connections...you are burning energy in each of them. Keep them clean.

Second, wire your batteries according to this instruction. They'll last longer and you'll burn less energy in the wiring.

Third, you have plenty of power to boondock, if you are a little bit conservative. Minimize power consumption, turn off lights when not in use, etc. Try to find alternate ways to do things without using electricity. I have a Melitta 10 cup coffee maker that makes good coffee with out using any electricity. A vacuum pump style pot or thermos keeps it hot for a LONG time.

Fourth, if you plan to boondock for extended time, consider getting solar panels. You could easily reduce the number of batteries and invest that money in solar. You want to balance your energy usage with you energy generation and bias toward the generation side a bit. Too much battery is just wasting $'s, too little and you run the generator too much.

LED lights like Command Electronics sells go a long way toward extending the available energy.

Leave the TV off, you are out in nature, enjoy it!

Get a Catalytic style heater to keep things warm inside if you boondock in the cold weather. Only use the forced air heater during the night, and then set the temp LOW. The catalytic heaters usually don't have a thermostat and aren't that adjustable in heat output.

I don't want to start a war here, but I'd move away from the AGM batteries and run like hell from Gel batteries. You pay a TON of money for them, and IMHO you don't get a ROI that makes sense. Trojan 105's or equivalent go for a lot less money and if you spend a few minutes a month maintaining them, you'll get lots of life out of them.

My hope is that the LiFePO4 batteries come down in price rapidly...at 2 times the volume energy density and 4 times the energy per pound. The also allow for a deeper depth of discharge (80% for 3000 cycles, 70% for 5000 cycles vs 50% for ~maybe~ 1000 cycle with lead acid) without damage or shortening the life a lot. Lifetimes that are almost an order of magnitude better...they'd be the last batteries I'd buy. Of course, I'd have to custom design my own charging system, but its much easier than charging lead acid batteries.

[takepride]

Dork:

Thanks for the food-for-thought, great website. However, you may be forgetting that some people are willing to pay a bit more for convenience, especially folks that don't want to be constantly checking and worrying about their batteries. My last coach had flooded wet cells and lasted about 4 years with perfect service for better than 2. I had to regularly fill the cells and had to jump it four times. My Alpine has AGMs that have lasted nearly 7 and I've not thought twice about them (though I admit I'm starting to think about it recently, because of this forum.)

waxy:

The Xantrex info seems to contradict your advice as it states "you should try to match the capacities". That would entail all 4C's or all 6C's. I'm surprised that no one has found info from a battery company suggesting mixing is okay. IIWM I'd question Wingding's guy at Lifeline a bit more as to his suggestion that they can be mixed.

I like the opening statement from RocketDork's website referral:

"A. Many "specialists" simply tell you..... "do it this way, this is the correct way" without ever showing why they consider it to be the correct way, and often it isn't, which is perhaps why they couldn't show you why it is(!)
B. Some things have been done for so long, in a certain manner, that it seems they must be the best way of doing it. Otherwise why hasn't another method appeared?"

I will readily bow to a proven expert who can logically back up his claim with real-world proof as well as good theory.

Truth be told, I'd mix them for my install if recommended, so I don't have to modify my battery compartment.

Lastly, I am striving for bigger capacity and more solar in order to avoid the noisy, smelly generator fouling my peace and relaxation. That is also why I paid more for a nicer coach. Everything has a value.

[RocketDork]

Originally Posted by takepride

Dork:

However, you may be forgetting that some people are willing to pay a bit more for convenience, especially folks that don't want to be constantly checking and worrying about their batteries.

Lastly, I am striving for bigger capacity and more solar in order to avoid the noisy, smelly generator fouling my peace and relaxation.

I tend to like to do the maintenance on my coach...but I do understand that others don't. I feel like there is a story that is told when I do maintenance...the coach tells me things I may not know otherwise. At the same time I'm checking the water level in my Exides, I'm also looking at the connections for corrosion, the tray for damage, etc. It helps me to pay attention to other things that are important...my preference, doesn't have to be yours though.

Properly maintained flooded cells will last just as long as AGM's, but there is a maintenance cost paid in free time...if you include that free time in the ROI calculation, you may have a different result than I do. I recognize that its different for each person...

The solar and additional batteries is a topic of intense discussion. There are so many variables to the whole thing that its hard to really decide exactly what to do. A guy known SolarBob had some pretty good advise though. Start by knowing how much energy you USE in a day. Get a device that measures how much you use...then plan from there. The way I'm planning my system is this.

1. Measure energy used for a while, get sort of an average use pattern, with max and min use.
2. Size my battery bank for about 2 days of use without charge.
3. Size my solar panels for about 1.5 days energy use.
4. Hope I guessed right.

My thinking in the above.
Battery Bank Sizing is related to how long I boondock (2 days min, 7 days max) and the typical weather patterns where I camp. It is very important to fully charge your battery bank on a regular basis...having too much capacity makes it hard to do this...
Solar Panel Sizing is related to how much energy I can put back into the batteries. Even on a cloudy day there is still energy available, so I get some into the batteries, but not a full charge. Its rarely cloudy for long where I'm at, so I should be able to return to full charge on the next sunny day.

If the weather conditions where I camp were different, my decisions would likely be different too.

The point is, if you boondock and want to avoid running your generator, there are a number of approaches...solar is one, a HUGE battery bank is another, wind another, tent still another...each one has to decide what way to go...but I'm kind of getting OT a bit from the OP.

[RocketDork]

Originally Posted by wa8yxm

HOW can one battery in the set be at a different SOC than the others?

You had me stumped there for a bit. It didn't sound right to me, but I couldn't come up with the reason why. I think I have it now...

State of charge is only accurately determined by the chemistry taking place in the battery. It is impossible to determine state of charge without allowing the battery to rest for a while.

Voltage is a secondary effect and is not a reliable measure of state of charge, or remaining capacity. Chemistry is the only way to know. Chemistry is also the mechanism that determines terminal cell voltage. The strength of the acid in the battery and the amount of Lead available for the reaction determine the terminal cell voltage.

So, you can overcharge a battery that is in parallel with others. Once the terminal voltage as determined by the existing chemistry in a specific battery is reached, you are overcharging it. If the Terminal Voltage is lower because the battery is old or of a different vintage that the rest...you can and will find that it reaches its full charge state before the others...

Again, its about the chemistry, not about the voltage. I think if you examine the charging algorithm for Lead Acid batteries, you'll agree. Typical three stage charge Algorithm goes like this.
Bulk charge - constant current until 2.30 to 2.45 volts per cell is reached.
Acceptance - constant voltage until current falls below 0.03C
Float - Drop to 2.25V per cell. This takes care of the self discharge characteristics of the battery...
Reference material for above

If Voltage were the determining factor of state of charge, we'd have a very different way to charge them. We'd skip the acceptance part of the charge algorithm and move directly to float.

I hope I made sense and didn't confuse.

Found this on my research path. Seems to be a give the customer what he wants, not what he needs kind of thing to me.

[ImagineIF]

WA8YXM, you are right...thanks for agreeing. Weaker batteries will reduce the effectiveness of the entire bank when being used. The same weaker batteries will reduce the combined voltage of the bank, resulting in overcharging of the better batteries or not enough charge to the weaker batteries. This is no different than a single weak cell making a battery worthless. Surely, we've all heard of bad batteries being bad due to a single weak cell.

Having spent a few years boating with trawlers, this topic comes up often. We often have battery banks with 6 - 10 golf cart batteries for the house as well as 2 - 3 other banks. So, having to change all batteries in a bank at once is a major expense, especially if using AGMs or gels.

Takepride,

If you want more battery capacity, moved to sealed batteries (AGM, Gel, or Optima) and move your engine start bank elsewhere. This way you can fully dedicate that tray to house.