I want to set up a new house bank, all new batteries. Due to limited space both height and length I can use gcs and L16s... is there a problem using a couple of L16s and a couple of golf carts. The l 16s will be wired in series as will the the gcs and then they will be paralleled... any issues with different ampacities but all the same type FLAs.
mixing battery sizes
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Comodave
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I would not do it. Don’t think they will charge properly.
certainly not ideal
charging will be uneven, longevity will be shorter
better most likely to treat as separate banks like old school, with a switch
but as long as the dissimilarity is only across paralleled connections, not dangerous
ideal is mod the space or select the liwest common denominator model
AGM can lie down
charging will be uneven, longevity will be shorter
better most likely to treat as separate banks like old school, with a switch
but as long as the dissimilarity is only across paralleled connections, not dangerous
ideal is mod the space or select the liwest common denominator model
AGM can lie down
caltexflanc
Guru
Sounds like the OP is another candidate for Calder's "Boat Owners Mechanical and Electrical Manual" or the "The 12 Volt Bible for Boats"
The answer is no, by the way. If charged as one bank, your batteries will die an early death.
Why can't you just use L16's? they have the same footprint as a GC.
The answer is no, by the way. If charged as one bank, your batteries will die an early death.
Why can't you just use L16's? they have the same footprint as a GC.
Ski in NC
Technical Guru
I am going to disagree with most here. A battery has no idea what it is connected to. It only knows voltage and amps in and out. If all the batts in the bank have the same chemistry and the right charging and discharging profile, it should work fine.
The preference is to have all the batts in the bank the same (size, type, mfr, age), but that is not a good option per the OP. The problem I see here is not that it will not work (it will) but the two types of batt will not age the same. At some point one group will need replacement and the other will still have some life. So he will have to choose to replace all or some and that complicates it further.
The preference is to have all the batts in the bank the same (size, type, mfr, age), but that is not a good option per the OP. The problem I see here is not that it will not work (it will) but the two types of batt will not age the same. At some point one group will need replacement and the other will still have some life. So he will have to choose to replace all or some and that complicates it further.
I am going to break further with the posters than Ski did and say that I will bet you will see little difference in battery life between the L16s and the GCs. As he points out the batteries don't know what they are connected to. The L16 will see a very, very slightly lower charge voltage due to greater voltage drop in their wiring than the GCs due to the fact that they will pull more current.
But that voltage difference is only very slightly noticeable at high charge rates. Once the batteries get more fully charged and the current decreases, that voltage difference becomes miniscule and irrelevant.
I will bet you can compensate for the voltage drop with the way you wire them. Wire the L16s first in the circuit so they get the maximum voltage and then wire the GCs downstream so they have more wire in the circuit.
But you are just fiddling with trying to make it perfect when almost perfect as psneeld notes below is just as good.
David
But that voltage difference is only very slightly noticeable at high charge rates. Once the batteries get more fully charged and the current decreases, that voltage difference becomes miniscule and irrelevant.
I will bet you can compensate for the voltage drop with the way you wire them. Wire the L16s first in the circuit so they get the maximum voltage and then wire the GCs downstream so they have more wire in the circuit.
But you are just fiddling with trying to make it perfect when almost perfect as psneeld notes below is just as good.
David
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ancora
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When we bought our boat it had four 6 volt golf cart batteries in parallel with a 4 D battery. The 4 D always died an early death, so we replaced it with two 6 volt golf cart batteries...problem solved.
I bet the short life of your 4D was due to using a starting battery for deep cycle service. There are very few if any true deep cycle 4Ds.
It is this sort of thing that perpetuates the mixed battery myth.
Don't get me wrong, I wouldn't mix FLAs with AGMs or Gels. But two different types of new deep cycle FLAs, no problem.
David
It is this sort of thing that perpetuates the mixed battery myth.
Don't get me wrong, I wouldn't mix FLAs with AGMs or Gels. But two different types of new deep cycle FLAs, no problem.
David
dhays
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Disclaimer: The following post is based on ignorance and stupidity. Be warned!
I have a hard time understanding (not unusual for me) the problem of connecting the batteries in parallel. Let’s make it simpler. What the OP is asking is if there is a problem connecting two 12v batteries in parallel of different sizes. In my simple mind I’m just assuming that each pair of L16s and GC2s are one 12v battery.
I will assume that the batteries are of the same chemistry and the manufacturers recommended charging profile are the same. If that is true then I’m not sure it matters if the 2 batteries are of different sizes. The voltage in each battery will stay the same, both during charge and discharge.
Another way to look at it, is that many of us use automatic combining relays on our boats that combine our start battery with our house battery during charging. Those are vastly different sized batteries that are being charged in parallel and yet I don’t hear about concerns there?
So, despite what Saint Calder has written, can someone explain how paralleling two batteries of unequal capacity creates problems? I’m not talking about age and chemistry, just size.
I have a hard time understanding (not unusual for me) the problem of connecting the batteries in parallel. Let’s make it simpler. What the OP is asking is if there is a problem connecting two 12v batteries in parallel of different sizes. In my simple mind I’m just assuming that each pair of L16s and GC2s are one 12v battery.
I will assume that the batteries are of the same chemistry and the manufacturers recommended charging profile are the same. If that is true then I’m not sure it matters if the 2 batteries are of different sizes. The voltage in each battery will stay the same, both during charge and discharge.
Another way to look at it, is that many of us use automatic combining relays on our boats that combine our start battery with our house battery during charging. Those are vastly different sized batteries that are being charged in parallel and yet I don’t hear about concerns there?
So, despite what Saint Calder has written, can someone explain how paralleling two batteries of unequal capacity creates problems? I’m not talking about age and chemistry, just size.
caltexflanc
Guru
Ski, but in a mixed bank they do NOT have the same charging profile. Think about it. That;s why as you mention later, death will be premature.
caltexflanc
Guru
Read the book. Don't take some stranger's opinion on the Internet for granted.
If you mean the manufacturer's recommended charging profile, maybe the two battery types don't have the same profile unless they are both Trojans or ???
But what does that matter. The charger probably has an AGM and FLA setting and if you select FLA you get one charging profile, not the one the manufacturer recommends. So what does it matter if the two have slightly different manufacturer recommended charging profiles if the charger isn't going to supply exactly that?
If by charging profile you mean the current that can be pushed through the battery at a given voltage and state of charge, then yes the L16 will generally accept twice as much current as the GC at the same voltage and state of charge. But that is like saying two GCs will accept twice the current as one. What does it matter that one battery is an L16 and the other is a GC.
How about this scenario (reduced to 6V to avoid considering series wiring): You have two GCs connected together in parallel with thick copper busses hooked up to another GC with normal 2/0 cabling.
How is that different than an L16 hooked up to a GC?
More electrons will go to the battery where the impedence is lowest. But as more electrons go to one battery its impedence rises as it reaches a higher SOC and balances with the other one.
David
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Exactly. Used as a constantly connected Bank, then The Bank will not last as long.
As long as the weakest link.
All components matched, gives the longest and most reliable life.
Ski in NC
Technical Guru
Agreed, matched is optimal. But the weaker cells in the bank may very well be "carried" by the stronger, and very well may last longer than if they formed the entire bank.
I'm going to stand by my assertion unless someone can post something on an engineering level that shows me to be wrong. Aging at different rates is not necessarily a problem, just change batts when they get weak. When that occurs is the topic.
I'm going to stand by my assertion unless someone can post something on an engineering level that shows me to be wrong. Aging at different rates is not necessarily a problem, just change batts when they get weak. When that occurs is the topic.
psneeld
Guru
That's it..... I am going to rip out all my batteries...and start over.
Going to buy all lab certified (not marine) charging sources, send out my battery wiring and switches to labs to be tested for resistance, then send them to Northrop Grumman to have satellite level
certified connectors added, then hire a factory tech to live abord to make sure the charging profiles are optimal ...etc, etc...
Anything the lab rats want to add to my list since I am giving up on reality boating?
Going to buy all lab certified (not marine) charging sources, send out my battery wiring and switches to labs to be tested for resistance, then send them to Northrop Grumman to have satellite level
certified connectors added, then hire a factory tech to live abord to make sure the charging profiles are optimal ...etc, etc...
Anything the lab rats want to add to my list since I am giving up on reality boating?
diver dave
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My engineering mind likes to take things to the extreme to solve puzzles. ie: put a motorcycle battery in parallel with an 8D and run them for a few years.
Haven't done it, but if I had to bet, I'm on the side of the table with ski.
WHat I have done is a lot of ni-cad work. And, I can tell you with certainty, you must match in a series array!
Haven't done it, but if I had to bet, I'm on the side of the table with ski.
WHat I have done is a lot of ni-cad work. And, I can tell you with certainty, you must match in a series array!
ben2go
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The lesser batteries will bring all other batteries down to their charge capacity. When recharging, the lower capacity batteries will stop the higher capacity batteries from reaching a full charge.
kchace
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If 2 higher capacity batteries are paralleled with 2 lower capacity batteries but of the exact same chemistry, the batteries will not know the difference. Since all 4 batteries should share the load equally the lower capacity batteries will "run out" of power before the higher capacity batteries. The numbers will not be exact since the lower capacity batteries will have lower output voltage before the higher capacity batteries so the higher capacity batteries will slowly share more of the load as the drawdown continues. But the net result will still be that the lower cap batteries will end up getting drawn down more deeply than the higher cap ones. As long as the higher cap batteries are in parallel with the lower cap batteries the charging will happen correctly, though if combined, the lower cap batteries will likely be charged sooner.
If possible, you could use a 1, 2 battery switch and split the charging with a multi bank charger for more efficiency during charge.
Frankly, I wouldn't bother with the L16s because you would not be able to realize the full amount of their increased capacity.
Ken
If possible, you could use a 1, 2 battery switch and split the charging with a multi bank charger for more efficiency during charge.
Frankly, I wouldn't bother with the L16s because you would not be able to realize the full amount of their increased capacity.
Ken
I believe that to be wrong unless there is a temperature sensor on the charger. As the internal resistance of the smaller capacity battery rises as it accepts a charge, ohms laws states that the voltage will increase meaning that the smaller capacity battery will be at a higher potential than the larger bank.... However since the smaller bank and the larger bank are parallel the smaller bank will actually assist in charging the larger bank until the internal resistance of the banks are in equilibrium...
If there is temperature feedback on the charge circuit I could understand how the smaller bank could limit the charge current to the larger bank resulting in a less then complete charge...
another question is what happens if you increase the number of GCs to equal the ampacity of the l16s so effectively you have 2 450 amp hour banks in parallel
diver dave
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Internal R reduces as the charge state increases.
Ohms law?? It is not the R, which is increasing with charge, it is the Voltage "source" of the cell that is increasing. This can be proven by these so-called "SoC" charts that simply use open circuit voltage to drive a % of charge meter. The Amperage thru the cells need to be close to zero to make this sorta-valid. If I = zero, then the internal R is a non-player, since no V drop occurs.
But, somehow, your assessment of the original assumption is true.
The "big battery" and the "small battery" don't see each other. They see the charger voltage. If there is some thermal sensor, which reduces V at the charger output, all batteries are equally affected, with the charge current thru each proportional to their respective sizes. "Sizes" not being the size/weight, but their internal R.
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ben2go
Guru
You may be right. When we would add newer higher capacity batteries into our equipment, they would get pulled down to the level of the old batteries. I have seen new batteries hold 13.5 to 13.8 volts and after being paired with older lesser capacity batteries at 12.5 to 12.8 volts, it didn't take long before the batteries developed a set and wouldn't full charge. All I have ever dealt with for any extended length of time (years) were flooded Trojan brand with paired charger. I have dealt with other batteries in vehicles, aircaft, and boats but not like I did in our equipment. I had my hands on those batteries multiple times a day for over five years. I saved many of them by swapping them around and matching capacities and voltages. I usually did that when one or more battery would go dead. It kept the new ones from dying faster. The place I worked for was cheap and didn't want to take care of the equipment.
Nepidae
Senior Member
Giving you a complete answer is difficult as you didn't provide any additional info as to how you plan on charging, maintaining and monitoring your new system.
I'm not sure and don't know if the L16's you are planning on are wet cell or AGM. GC batteries are usually wet cell.
You also don't provide any info on your boat size.
And you don't mention your charging and inverter setup.
I had a house bank put in our boat in '16. Previous to that we had 2 4D wet cell batteries which we used, not very well, for house & engine with a 3 way switch to utilize the batteries.
The new house bank is 6 L16 6V AGM batteries. These batteries are very heavy and I was able to remove a set of 'day tanks' that were in the bottom of the bilge and put the batteries there, low center of gravity. After these were put in I also needed to upgrade the charging system. The OEM alternators (alts) did not have the output to handle this new load. New Balmar alts 120A were put in. This also required 2 (twin engines) new regulators, duo-chargers and a centerfielder (all Balmar). The centerfielder controls where the power goes. Whether to the house or engine bank.
As I said I also kept the 2 4D wet cell batteries, which were utilized as an engine bank.
Our Xantrex, SW3012 charger/inverter has a 3 way charging system which is very important in properly maintaining your new intended battery banks. I set the charging profile to AGM as they were the most valuable part of the system of batteries. This meant that the wet cells were not being charged properly. In this instance I knew that and knew I would be swapping out the wet cell shortly, which I did at the beginning of this year.
Any charger you have should be able to Bulk, Absorb & Float charge your batteries.
A good inverter should be part of your setup. An expenditure on a good battery bank can only be utilized with a good inverter. Our Xantrex also has a control panel which enables us to 'see' exactly what's going on with the charging and discharging of our house (L16) battery bank. I am adding a separate monitoring system for the engine bank.
I would agree, with some of the posters, that combining, in a single bank, is NOT a good idea.
So, if you'd like to contact me off-forum I'd be glad to further discuss what I've done and how it could be applicable to you.
I'm not sure and don't know if the L16's you are planning on are wet cell or AGM. GC batteries are usually wet cell.
You also don't provide any info on your boat size.
And you don't mention your charging and inverter setup.
I had a house bank put in our boat in '16. Previous to that we had 2 4D wet cell batteries which we used, not very well, for house & engine with a 3 way switch to utilize the batteries.
The new house bank is 6 L16 6V AGM batteries. These batteries are very heavy and I was able to remove a set of 'day tanks' that were in the bottom of the bilge and put the batteries there, low center of gravity. After these were put in I also needed to upgrade the charging system. The OEM alternators (alts) did not have the output to handle this new load. New Balmar alts 120A were put in. This also required 2 (twin engines) new regulators, duo-chargers and a centerfielder (all Balmar). The centerfielder controls where the power goes. Whether to the house or engine bank.
As I said I also kept the 2 4D wet cell batteries, which were utilized as an engine bank.
Our Xantrex, SW3012 charger/inverter has a 3 way charging system which is very important in properly maintaining your new intended battery banks. I set the charging profile to AGM as they were the most valuable part of the system of batteries. This meant that the wet cells were not being charged properly. In this instance I knew that and knew I would be swapping out the wet cell shortly, which I did at the beginning of this year.
Any charger you have should be able to Bulk, Absorb & Float charge your batteries.
A good inverter should be part of your setup. An expenditure on a good battery bank can only be utilized with a good inverter. Our Xantrex also has a control panel which enables us to 'see' exactly what's going on with the charging and discharging of our house (L16) battery bank. I am adding a separate monitoring system for the engine bank.
I would agree, with some of the posters, that combining, in a single bank, is NOT a good idea.
So, if you'd like to contact me off-forum I'd be glad to further discuss what I've done and how it could be applicable to you.
twistedtree
Guru
I agree with Ski.
- Batteries in series need to be of the same type AND capacity.
- Batteries in parallel need to be of the same type so that the charging parameters are the same.
The only issue I can see is that once the battery voltage reaches the bulk/absorb voltage, I think the smaller cells may reach full charge and minimal acceptance current sooner than the larger cells. Then the smaller cells will be held at bulk/accept voltage until the larger cells reach full charge. The result is that the smaller cells might be held at accept voltage longer than necessary. That said, I don't think it's a big deal.
So given the choice of
1) a smaller bank made up of one size cell
2) two separate banks that need to be managed
3) Once larger combined bank
I'd pick #3.
- Batteries in series need to be of the same type AND capacity.
- Batteries in parallel need to be of the same type so that the charging parameters are the same.
The only issue I can see is that once the battery voltage reaches the bulk/absorb voltage, I think the smaller cells may reach full charge and minimal acceptance current sooner than the larger cells. Then the smaller cells will be held at bulk/accept voltage until the larger cells reach full charge. The result is that the smaller cells might be held at accept voltage longer than necessary. That said, I don't think it's a big deal.
So given the choice of
1) a smaller bank made up of one size cell
2) two separate banks that need to be managed
3) Once larger combined bank
I'd pick #3.
This has been an interesting and unfortunately typical thread. I stopped following it a week ago and just now checked on it.
What you have are five sources of information:
1. Pure unadulterated dock talk. Frankly in my experience it is at least half wrong.
2. Opinions, supported by the poster's own experience. But one or two samples does not make a trend. In many of these one off samples, there were other just as likely causes.
3. Opinions, supported by some engineering reasoning but based on a misunderstanding of the scientific or engineering principles which makes it worthless.
4. Opinions, supported by sound engineering and reasoning.
5. Opinions, by a a recognized expert like Steve D'Antonio or Nigel Calder.
I tend to pay attention to the last two and ignore the rest.
How do you separate fact from fiction if you ask a question and are basing how you operate your boat or buy a new piece of equipment on the answer?
David
What you have are five sources of information:
1. Pure unadulterated dock talk. Frankly in my experience it is at least half wrong.
2. Opinions, supported by the poster's own experience. But one or two samples does not make a trend. In many of these one off samples, there were other just as likely causes.
3. Opinions, supported by some engineering reasoning but based on a misunderstanding of the scientific or engineering principles which makes it worthless.
4. Opinions, supported by sound engineering and reasoning.
5. Opinions, by a a recognized expert like Steve D'Antonio or Nigel Calder.
I tend to pay attention to the last two and ignore the rest.
How do you separate fact from fiction if you ask a question and are basing how you operate your boat or buy a new piece of equipment on the answer?
David
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