RV has two types of led acid...whats the ah for my CC?

[Stewfish]

I have four 6 volt golf cart batteries set up for a 12 volt RV system 2s2p. I have two Costco batteries in series w/ 210ah (@ 20 hrs) each. Then I have two batteries that I got at a small shop on the road w/ 225ah (@ 20 hrs) each

I'm using the smaller battery 210ah, for all the batteries. I'm thinking make the calculation using the smaller amp hours as the max so that I don't overcharge the smaller 210ah battery and make it boil a lot. I'm getting 420ah and that seems high. I guess the paralleled batteries cancel each other out then its just 210+210 for both series. Unfortunately I got two different batteries bc of the location I was in at the time last May. I posted the internet calculator I used.
I'm thinking I need to balance the batteries once in awhile.

Will the two series 210 and 225 balance at night while not charging?

See pics for my 2s2p in the calculator

 

[grizzzman]

Assuming that the batteries are healthy internal resistance will decide where the amps go. You plan on charging/discharging at 210 Amps? I highly doubt that.

 

[snoobler]

I have four 6 volt golf cart batteries set up for a 12 volt RV system 2s2p. I have two Costco batteries in series w/ 210ah (@ 20 hrs) each. Then I have two batteries that I got at a small shop on the road w/ 225ah (@ 20 hrs) each

Assuming the 225Ah are also 6V, so:

2S2P of 6V 210Ah batteries
2S of 6V 225Ah in parallel with the above.



Ah depends on voltage.

If you series batteries, Ah same, voltage adds.
If you parallel, Ah adds, voltage same.

So your 2S2P 210Ah 6V make a 420Ah 12V battery
If your adding two more 225A 6V, you have a 645Ah 12V battery bank.

Charge at 65-97A (10-15%C)

 

[Stewfish]

Assuming that the batteries are healthy internal resistance will decide where the amps go. You plan on charging/discharging at 210 Amps? I highly doubt that.

My charge controller has a setting to add the amp hour of my battery bank. So I put 420ah in that setting based on my thoughts above. Pardon my explanation "charging"

My setup
Series one = 6v 210ah & 6v 210ah = 12v 210ah
Series two = 6v 225ah & 6v 225ah = 12v 225ah
That would be 210+225 = 435ah.

I would over charge the 210 and under charge the 225ah if I put 435ah. I though it was wise to undercharge at 420 total, vs overcharge the 210ah series to 217.5 ah if I put 435.

 

[Stewfish]

Assuming the 225Ah are also 6V, so:

2S2P of 6V 210Ah batteries
2S of 6V 225Ah in parallel with the above.

View attachment 38306

Ah depends on voltage.

If you series batteries, Ah same, voltage adds.
If you parallel, Ah adds, voltage same.

So your 2S2P 210Ah 6V make a 420Ah 12V battery
If your adding two more 225A 6V, you have a 645Ah 12V battery bank.

Charge at 65-97A (10-15%C)

-In the first sentence I said four 6v batteries

-It is 2s2p for 12v RV, thus they are all 6v to get 12v with 2s2p.

 

[Stewfish]

Assuming that the batteries are healthy internal resistance will decide where the amps go. You plan on charging/discharging at 210 Amps? I highly doubt that.

Will the two series 210 and 225 balance at night while not charging?

I put the controller leads to the 225ah 12v series (6v+6v =12v). The 210ah series (6v+6v=12v) is paralleled off that. Will it be putting the amps into that first series and then when that tops off it will "go" into the other parallel series? Just thinking about how the charge "flows" . Does the 210ah bank constantly draw/try to balance out off the 225ah bank?

 

[snoobler]

-In the first sentence I said four 6v batteries

-It is 2s2p for 12v RV, thus they are all 6v to get 12v with 2s2p.

Doh. Yes you did.

So based on your assumptions, 420Ah was correct. 435Ah actual.

Charge at 10-15% C.

Will the two series 210 and 225 balance at night while not charging?

I put the controller leads to the 225ah 12v series (6v+6v =12v). The 210ah series (6v+6v=12v) is paralleled off that. Will it be putting the amps into that first series and then when that tops off it will "go" into the other parallel series? Just thinking about how the charge "flows" . Does the 210ah bank constantly draw/try to balance out off the 225ah bank?

Not much. There is very little current flow between parallel batteries at rest. They will quickly "balance" to the same SoC when subjected to charges/discharges proportional to the effectiveness of your wiring.

You should connect the main leads as above except for the two extra batteries. 1 on one series group, 1 on the other series group. If you had dramatically different capacities, your approach might be warranted. These aren't even 10% different.

 

[Stewfish]

You should connect the main leads as above except for the two extra batteries. 1 on one series group, 1 on the other series group. .

Ah, ok, so as an example put the positive lead on the 225ah bank + and the neg lead on the 210ah bank neg?

I bet the 225ah lead acid is from the same factory as my costco interstate batteries. I think there are only 3 factories in the world that actually make lead acid batteries. The guy said it was from the same factory as interstate. I think Interstate is from Universal in Taiwan or S. Korea or something.

 

[grizzzman]

Ah, ok, so as an example put the positive lead on the 225ah bank + and the neg lead on the 210ah bank neg?

You got that correct.

 

[mvas]

My charge controller has a setting to add the amp hour of my battery bank. So I put 420ah in that setting based on my thoughts above. Pardon my explanation "charging"

My setup
Series one = 6v 210ah & 6v 210ah = 12v 210ah
Series two = 6v 225ah & 6v 225ah = 12v 225ah
That would be 210+225 = 435ah.

I would over charge the 210 and under charge the 225ah if I put 435ah. I though it was wise to undercharge at 420 total, vs overcharge the 210ah series to 217.5 ah if I put 435.

There is no such thing as "Under-Charging the 225 Ah Bank, while simultaneously Over-Charging the 210ah bank"
If the wires connecting the battery banks are sufficient - fat and opposite diagonal (+/-) terminals then ...
your 2 battery banks are connected in PARALLEL, therefore they have (essentially) the exact same voltage.
Both banks are discharged and charged with the same voltage.
After Bulk, Absorb & Float - BOTH banks will be at 100% SOC = the same voltage, at the same time.
During discharge, BOTH banks will drop down to your Low Voltage Disconnect = the same voltage, at the same time.

Notes:
#1) Adding new batteries in parallel to old batteries is not "Best Practice".
#2) Adding different mfr, model #, Ah batteries in parallel is not "Best Practice"
But sometimes ... we do, what we need to do, it is not the end of the world either.

If these are FLA (Flooded Lead Acid) then the "C-Rate" setting in your APP should typically be "0.125" = C/8, not "1" = C/1.
But for most people, it is impossible to get 8 hours of full sun in winter,
to completely recharge a deeply discharged battery bank.
So, you may need to charge at a faster rate, as allowed per the MFR.
Values for your APP ...
Volts = "12"
Ah = "435"
C-Rate = "0.125"
Pack = "1S1P"
because you have different Ah batteries in parallel.

I can see the need for ...
a) 100+ Amps total from the Charge Controller(s)
b) 2,400+ Watts total of Solar

Whats is your planned Daily % DOD ?

 

[snoobler]

Ah, ok, so as an example put the positive lead on the 225ah bank + and the neg lead on the 210ah bank neg?

I bet the 225ah lead acid is from the same factory as my costco interstate batteries. I think there are only 3 factories in the world that actually make lead acid batteries. The guy said it was from the same factory as interstate. I think Interstate is from Universal in Taiwan or S. Korea or something.

Almost all "consumer" lead-acid batteries available in the U.S. are made by the former Power Solutions division of Johnson Controls (now Brookfield Asset Management Inc) in Mexico. Interstate included. JC had several of their own brand names including Optima. Also in play are Yuasa in Japan and different brands in S. Korea. Rolls makes their own in Canada, and various mid to high end names like Trojan make their own in the U.S.

 

[Stewfish]

You got that correct.

Should the inverter also span both sets of parallel batteries like the charger?

 

[grizzzman]

Should the inverter also span both sets of parallel batteries like the charger?

Yes

 

[snoobler]

"wiring" in link #2 in my sig for Victron document including best practices for making battery bank connections.

 

[Nakinto]

Biggest issue here, is that the 2 different ampacities will end up with degradation of ALL batteries earlier then if you just used one set of the ampacities. They WILL WORK, but they will not work for very long.

Wiring, as shown above, both leads SHOULD go to either a bus bar where the CC and the Inverter are connected to the same,




OR just run the CC to the inverter then to the batteries.



I hope the diagrams are easily legible. No matter what configuration you put the 210 and 225s in, it will always result in early death of the batteries. If you do 210-225 in series then the 210 will end up gassing a LOT and the 225 will never get that 100% charge eventually dying early. If you do 210-210 and 225-225 in series parallel then the 225's will never fully charge and will degrade to match the 210's, eventually, and quickly die after that, bringing the 210's with them.

ALSO, make sure to connect them as shown, positive goes to the last battery on ONE side and the negative to the last battery on the OTHER side. Otherwise you will end up with much higher resistance on the far side batteries then on the closer ones. AND please try to keep the lengths of wire between each battery as close to the same lengths as possible (not as important with LA as with Lithium, but still important.

 

[snoobler]

I hope the diagrams are easily legible. No matter what configuration you put the 210 and 225s in, it will always result in early death of the batteries. If you do 210-225 in series then the 210 will end up gassing a LOT and the 225 will never get that 100% charge eventually dying early. If you do 210-210 and 225-225 in series parallel then the 225's will never fully charge and will degrade to match the 210's, eventually, and quickly die after that, bringing the 210's with them.

Consider that you are making these claims based on battery capacities that vary by about 7%. Please cite your source for these claims. If you do not exceed battery ratings, you will not significantly impact their lives.

 

[Nakinto]

Consider that you are making these claims based on battery capacities that vary by about 7%. Please cite your source for these claims. If you do not exceed battery ratings, you will not significantly impact their lives.

I do not know the rules for posting this kind of stuff, but as a Moderator has asked for it, I will supply multiple articles on the subject matter of paralleling different ampacity/age/resistance Lead Acid batteries. Please note, this doesn't apply to Lithium as we use BMS's with Lithium batteries and they allow all batteries to charge to the same voltage.

Charging Information For Lead Acid Batteries – Battery University

Review various Lead Acid charging methods and examine why some systems work better than others. Find also simple guidelines for charging Lead Acid batteries.

batteryuniversity.com

The Rolls battery manual

https://rollsbattery.com/public/docs/user_manual/Rolls_Battery_Manual.pdf

I don't particularly like this one but it still has information pertinent to the question above.

Connecting batteries in parallel – BatteryGuy.com Knowledge Base

And finally, personal experience spanning multiple generations in my family working with electricity. The way LA batteries charge, you do NOT charge all the batteries to the same amperage, you charge them to the same voltage, this will cause a middle ground when charging different ampacity batteries in parallel, whether this ampacity is due to age or design. The 210's will overcharge (read boil) and the 225's will undercharge (read sulfate) this will (and does) lead to the 210's needing water more often, the 225's will require special attention, namely daily disconnects from the system and equalizing. If you equalize the system with the 210's and the 225's in parallel (any configuration) the 210's will get very hot, boil off the water (and sulphuric acid) and will release hydrogen from the boiling water, and if not properly vented cause a dangerous atmosphere of high concentrations of Hydrogen (flammable gas) and Oxygen.

 

[snoobler]

I've posted the Rolls battery manual many times along with the Trojans, and I'm very familiar with Battery University.

You haven't posted anything that supports your claims. There are best practices, and there are compromises against that. No one is arguing that it's not the best way to do things, but you've made claims that read like a catastrophe, "die," "early death, "quickly die and bring them down with them."

No battery on the planet has singular requirements. They all have a range. Typical FLA can be charged from 5-20% of the C20 rate. Typical FLA are happy in absorption in the 14.4-15.0V range. Tail currents vary as well. It's pretty easy to establish a system that keeps everything within acceptable parameters.

Will this 2S2P 435Ah battery bank wear out before a single 435Ah 12V? Absolutely. Will it die a quick death? Only if no effort is made to mimic best practices and charge according to manufacturer's recommendations. Will it last longer than either a 210Ah or a 225Ah bank alone? Absolutely.

My 48V T-1275 bank (4S2P) is comprised of batteries that vary by 21%. Their manufacture dates range from 2015 to 2018. These were removed from golf carts and put into service in late 2019. They are in a shipping container that experiences up to 45°F swings per day. One group of 4 has batteries that perform between 75 and 86% rated. The other group performs in the mid 90%'s. These are based on 25A discharges to 10.5V and compared to the rated RC.

They are treated according to the lowest capacity unit, i.e., this is a 75% battery, so the bank has a capacity of 225Ah @ 48V. It's max charge current is limited to 0.13C of the lowest capacity unit. It is cycled daily to 80-90% SoC with deeper discharges to 50, 70 and 80% DoD a few times a month. They have been operating in this capacity for 1.5 years, and there has been no apparent decrease in performance based on the voltage to SoC relationship. In that time, I have only equalized 4 times based on deviation in SG vs. their original condition.

True
3-6 years old
Substantial variations in capacity (75-96% rated)
Extreme temperature fluctuations
Effort to engage in best practices respecting battery limits

False
Die a quick death
Weak one taking out the stronger ones
Excessive gassing
Explosion or fire

 

[Stewfish]

you do NOT charge all the batteries to the same amperage, you charge them to the same voltage, this will cause a middle ground when charging different ampacity batteries

My verbage was to explain what you said, potato potato. However one begets the other as you explained, and what I was trying to elaborate on. Basically there is no BMS so they will charge at different rates and to different levels e.g voltage which in turn gives you a "usable" or sub standard "amp hour" vs their rated ah when tested. To discharge it, would not give you full ratings per oem specs.

It is what it is now, so when the time comes I will get all the same batteries. Alas, I was trying to see if there was a way to mitigate the issue.

 

[Nakinto]

I've posted the Rolls battery manual many times along with the Trojans, and I'm very familiar with Battery University.

You haven't posted anything that supports your claims. There are best practices, and there are compromises against that. No one is arguing that it's not the best way to do things, but you've made claims that read like a catastrophe, "die," "early death, "quickly die and bring them down with them."

No battery on the planet has singular requirements. They all have a range. Typical FLA can be charged from 5-20% of the C20 rate. Typical FLA are happy in absorption in the 14.4-15.0V range. Tail currents vary as well. It's pretty easy to establish a system that keeps everything within acceptable parameters.

Will this 2S2P 435Ah battery bank wear out before a single 435Ah 12V? Absolutely. Will it die a quick death? Only if no effort is made to mimic best practices and charge according to manufacturer's recommendations. Will it last longer than either a 210Ah or a 225Ah bank alone? Absolutely.

My 48V T-1275 bank (4S2P) is comprised of batteries that vary by 21%. Their manufacture dates range from 2015 to 2018. These were removed from golf carts and put into service in late 2019. They are in a shipping container that experiences up to 45°F swings per day. One group of 4 has batteries that perform between 75 and 86% rated. The other group performs in the mid 90%'s. These are based on 25A discharges to 10.5V and compared to the rated RC.

They are treated according to the lowest capacity unit, i.e., this is a 75% battery, so the bank has a capacity of 225Ah @ 48V. It's max charge current is limited to 0.13C of the lowest capacity unit. It is cycled daily to 80-90% SoC with deeper discharges to 50, 70 and 80% DoD a few times a month. They have been operating in this capacity for 1.5 years, and there has been no apparent decrease in performance based on the voltage to SoC relationship. In that time, I have only equalized 4 times based on deviation in SG vs. their original condition.

True
3-6 years old
Substantial variations in capacity (75-96% rated)
Extreme temperature fluctuations
Effort to engage in best practices respecting battery limits

False
Die a quick death
Weak one taking out the stronger ones
Excessive gassing
Explosion or fire

While this discussion should probably not be done on this person's post

Excellent job taking my statements out of context. I never said die a quick death, but that the batteries would die quickly after being damaged from either a low charge (sulfation) or overcharged (excessive gassing) due to different ampacities of the batteries. You claim overcharging won't cause excessive gassing (you said it was false) every lead acid manufacturer disagrees with you and every battery comes with a warning label stating such. I never said explosion or fire, I did infer it was a dangerous possibility, just like every FLA, AGM, SLA claim on their warning labels.

I had a FLA system for 8 years, I replaced batteries in the system multiple times. I started with a 4s2p configuration of Duracell 31M 110 AH, brand new. One battery in one string had a short on year 3, replaced just the one battery. I did a capacity test on the system, 50% DOD measured by specific gravity and resting voltage after full charge and 5 day resting period. The system was at 78% capacity then. Two years later I had an entire bank die in quick succession, guess what bank it was? Yes, the one I had only replaced the one battery on. The other string was at 64% at this time, so I replaced added two strings of new batteries. I decided to leave the old string that hadn't died yet in service. Within 9 months I had noticed a severe degradation of capacity, I checked all the batteries and found the BRAND NEW BATTERIES were at 71% capacity! The old were at 53%. I also noticed I had a nice sheen of white 'condensation' on my glass surfaces around the batteries, turns out this was evaporated sulphuric acid from the old batteries boiling off faster then normal, and yes, I had noticed I had to add water (only added distilled water ever) more often to the old batteries then I did before I put in the two new strings, and with the evaporated Sulphuric Acid, the 'old' batteries were probably closer to 65-70% but the specific gravity test put them lower. But this is what is called a "personal experience fallacy" and I don't rely on that alone for the information I have.

"No battery on the planet has singular requirements. They all have a range." At no point in time did I infer or suggest otherwise did I? You then go on to claim "best practices" are you aware of the walking contradiction here? Best practices with any batteries are to match them as close as possible in ampacity, age and internal resistance (really the internal resistance is the most important). But you claim that doesn't matter, while then going on to claim that it does!

You use hyperbole and red herring and personal experience fallacies. You state "You haven't posted anything that supports your claims." Did you even bother to read any of the links I gave? Clearly not. ALL of them stated that paralleling batteries of different internal resistances and capacities are going to shorten the lifespan of the batteries. You are taking what I have said out of context, then exaggerating what I say to fit your world view, projecting your issues onto my posts. Please do not continue to do that.