Battery setup help

[EmpirE231]

So this is my new to me motorhome, and I am trying to figure our whether I already have problems with these highline AGM's that are about 2 years old.

first off.... is this considered series or parallel? (this is the diagram on the door)



#2  hard to tell from these pics... but it looks like they are wired up the same way the diagram suggests



which brings me to the main question.  First... background of this system.... It has 2 magnum 2000 watt inverters, one dedicated to the residential fridge, and the other to the rest of the "house".... it is supposed to be 4 batteries for the fridge, and 4 for the house..... But to me it looks like all 8 are tied together?? or am I wrong?  The issue I'm getting at is how do you set charging parameters for the batteries? since you have 2 inverters trying to charge the entire bank? (I would assume it was supposed to be 1 inverter per set of 4 batteries)  Someone fill me in here if I am wayyy of base.  I am not familiar with this stuff at all... just trying to figure it out so we can go from there.  Thanks.

 

[Jaybird95]

Each pair is in a series and they are all paralleled together.

Definitely looks like all 8 are feeding both inverters.

 

[Jaybird95]

I would set the parameters up to charge 4 batteries for each inverter.

Whether you run the genny or have shore power they will all get charged.

 

[Lord of the Dunes]

Go to the battery mfr's website. Look up the recommended charging voltage and float voltage for the 6v batteries you have. Double those numbers and set both inverter/chargers to those numbers.

 

[EmpirE231]

Each pair is in a series and they are all paralleled together.

Definitely looks like all 8 are feeding both inverters.

wouldn't that make it a 24v system?  this stuff is all greek to me....... but I do know it is only setup as a 12v system currently 

 

[Jaybird95]

wouldn't that make it a 24v system?  this stuff is all greek to me....... but I do know it is only setup as a 12v system currently 

No, Each pair makes 12 volts and each pair is paralleled to the next pair.

 

[Jaybird95]

The short jumper from the + to the - is your series jumper.

Then the 4 + are paralleled together and so are the -'s

 

[Lord of the Dunes]

Go to the battery mfr's website. Look up the recommended charging voltage and float voltage for the 6v batteries you have. Double those numbers and set both inverter/chargers to those numbers.

In case you didn't read it the first time. Each pair of 6v batteries are connected in series to make 12v. You have 4 x 12v batteries made up of pairs of 6v batteries. The correct charging voltage is on the mfr website for those specific 6v batteries.

 

[IFLY]

If you have invertors they are not charging your batteries. They are only suppling power to the coach. They are drawing from all 8 batteries. You would to split your set up and have 2 separate banks of 4. Then connect only 1 inverter to each bank of 4. Would not be that hard to do. You will need to get some extra cables and I had order mine.

 

[Kraut_n_Rice]

If you have invertors they are not charging your batteries. They are only suppling power to the coach. They are drawing from all 8 batteries. You would to split your set up and have 2 separate banks of 4. Then connect only 1 inverter to each bank of 4. Would not be that hard to do. You will need to get some extra cables and I had order mine.

He could probably do that without buying anything.  Remove one each (+) and (-) parallel, the middle most ones.  Then move Inverter #2 (+) to the right side bank, and Inverter #1 (-) to the left bank.

edit...Does the refer really need that much power?  I'd probably put the refer inverter on just one pair, and the house on the other 3.

 

[Lord of the Dunes]

If you have invertors they are not charging your batteries. They are only suppling power to the coach. They are drawing from all 8 batteries. You would to split your set up and have 2 separate banks of 4. Then connect only 1 inverter to each bank of 4. Would not be that hard to do. You will need to get some extra cables and I had order mine.

In the pic it clearly shows they are both inverter/converters, so both of them charge the batteries as well as make 120v. He's better off leaving the battery bank as it is, rather than decreasing it into 2 banks of 1/2 the power. This way he has less voltage sag when he uses larger appliances, like the microwave. 

 

[Lord of the Dunes]

He could probably do that without buying anything.  Remove one each (+) and (-) parallel, the middle most ones.  Then move Inverter #2 (+) to the right side bank, and Inverter #1 (-) to the left bank.

edit...Does the refer really need that much power?  I'd probably put the refer inverter on just one pair, and the house on the other 3.

There is no advantage to splitting the battery bank, only a downside of cycling the batteries deeper, which decreases their lifespan.

If it was mine, I'd leave the batteries all connected together and move all of the outlets to the same inverter as the fridge, if they aren't already set up like that. Then I'd put only the microwave on the 2nd inverter. This way, I wouldn't be running both inverters at all times, just the one would run the TVs, laptops, phone chargers and the fridge. Running both inverters just doubles the power wasted from converting 12v to 120v. Then if I needed to run the microwave, just turn on the 2nd inverter and turn it off when no longer needed. When running the genny to charge batteries, turn on both of them to maximize charging current, as long as the total doesn't exceed the recommended charge rate of the batteries. If they do, just adjust one or both charger's output current to match it.

 

[Jaybird95]

There is no advantage to splitting the battery bank, only a downside of cycling the batteries deeper, which decreases their lifespan.

If it was mine, I'd leave the batteries all connected together and move all of the outlets to the same inverter as the fridge, if they aren't already set up like that. Then I'd put only the microwave on the 2nd inverter. This way, I wouldn't be running both inverters at all times, just the one would run the TVs, laptops, phone chargers and the fridge. Running both inverters just doubles the power wasted from converting 12v to 120v. Then if I needed to run the microwave, just turn on the 2nd inverter and turn it off when no longer needed. When running the genny to charge batteries, turn on both of them to maximize charging current, as long as the total doesn't exceed the recommended charge rate of the batteries. If they do, just adjust one or both charger's output current to match it.

The entire point of having 2 inverters is because there is a house fridge inside.

The manufacturer didn't save any money by doing this, they could have just installed a larger one.

The fridge is a major component of the RV, without it your icing chit down. PITA

I would never turn on a inverter just to run the microwave, that is a battery killer.

You run the micro for 2 to 5 minutes on the inverter then you need to run the genny for 30 minutes just restore the power you lost.

 

[r3meyer]

Uhhh.  You guys kill me sometimes.

@EmpirE231

In the battery world the BIGGER THE BANK THE BETTER.  Leave the setup alone.  Think of it as a body of water.  The larger the body the better.  IF you remove 10k gallons from your pool would you notice? -Yes.  If you remove 10k gallons from the local lake would you notice? - No

You mentioned you might have a problem but didn't state what that was.

The reason you have 2 inverter chargers is because of possible load required.  It does not matter what powers what or why.  Its just a math equation again.  Make more than you use.  When dry camping you want them cranked up to recoup as much power as possible when the generator is running.  You would need to check the MFG charge rates for those AMG's.  

What are you trying to accomplish so I can tell you where to go from here.

 

[Dockmaster]

I understand the points being made about keeping a single bank and that bigger is better. What I haven't seen any one mention is how do two inverters, both with chargers, charge the same battery bank? I have always been under the impression that multiple chargers going to the same battery can cause issues as they both sense the incoming voltage and think it's the battery voltage. Does he simply turn the charger mode off on one inverter or do you just let them both charge together?

Wouldn't there also be an advantage to having a dedicated battery and inverter feeding just the fridge? This would protect from the potential of other loads drawing down the battery bank and possibly causing fridge issues? Yes, this can be managed and even done with an auto-gen start. Not sure if he has that?

 

[Lord of the Dunes]

The entire point of having 2 inverters is because there is a house fridge inside.

The manufacturer didn't save any money by doing this, they could have just installed a larger one.

The fridge is a major component of the RV, without it your icing chit down. PITA

I would never turn on a inverter just to run the microwave, that is a battery killer.

You run the micro for 2 to 5 minutes on the inverter then you need to run the genny for 30 minutes just restore the power you lost.

No kidding about the fridge. However, let's do some math to determine what's really going on. The house fridge is a critical load. It is NOT a major load. Both inverters are 2,000w ea. The fridge consumes maybe 300w when it's running, possibly slightly more, but definitely not enough to need a 2kw inverter all by itself. Each inverter consumes power even when not in use and when inverting, is only about 90% efficient. Keeping both inverters on when only running the fridge is wasting DC power. If the one inverter is going to be on all of the time for the fridge, it might as well support other hotel loads like the outlets for no additional loss of power, like running them off of a 2nd inverter.

They didn't need to install 2 inverters for the fridge and outlets, that's 4,000w of capacity for less than 1,000w of loads, so the other inverter is probably already powering the microwave and possibly other loads, like outlets. There's a moderate chance his moho is already wired up the way I described, since that's the most efficient use of power, but I wouldn't bet on it since it's an RV and they do less than optimal things.

The whole point of dedicating the expense and space of having 8 batteries and two inverters is to have a little bit of luxury and not have to start the genny and wait for the ATS to switch over and the genny to stabilize. With 2 chargers, the battery recharge time is going to be as short as the battery charge rate will allow. He's already powering the fridge and outlets, might as well add 2 or 3 minutes of microwave. When powering the microwave, the load will be less than 150A, assuming it ran for 5 minutes, that's 1/12 of an hr, so it consumed a whopping 12.5A for that 5 minutes of use. Kind of a drop in the bucket compared to the rest of the power needed to recharge the batteries from everything else.

 

[Lord of the Dunes]

I understand the points being made about keeping a single bank and that bigger is better. What I haven't seen any one mention is how do two inverters, both with chargers, charge the same battery bank? I have always been under the impression that multiple chargers going to the same battery can cause issues as they both sense the incoming voltage and think it's the battery voltage. Does he simply turn the charger mode off on one inverter or do you just let them both charge together?

Wouldn't there also be an advantage to having a dedicated battery and inverter feeding just the fridge? This would protect from the potential of other loads drawing down the battery bank and possibly causing fridge issues? Yes, this can be managed and even done with an auto-gen start. Not sure if he has that?

Battery chargers, or any charging source, don't care what else is charging. He could have 3 chargers and a solar controller and they will all put current into the battery bank until they hit the absorption voltage they are set to. Then when they hit that V, each one shuts off. Assuming they are all set to the same V, they'd all shut off at the same time, but they could be set to shut off whenever you want. 

This is especially true for people with older chargers that can't be set for LFP batteries they just bought. The LFP batteries need 14.6V to fully charge, but if the battery charger provides 60A at 14.2V, he doesn't necessarily have to replace it if he has a solar controller set to 14.6V. In this case, the solar might provide 30A and the charger provides 60A up to 14.2V, the charger shuts off and the solar keeps going to 14.6V and they get fully charged nearly as fast, since it doesn't take much power to get from 14.2V to 14.6V.

The short version is multiple charging sources add to each other, they don't interfere with each other.

 

[EmpirE231]

Uhhh.  You guys kill me sometimes.

@EmpirE231

In the battery world the BIGGER THE BANK THE BETTER.  Leave the setup alone.  Think of it as a body of water.  The larger the body the better.  IF you remove 10k gallons from your pool would you notice? -Yes.  If you remove 10k gallons from the local lake would you notice? - No

You mentioned you might have a problem but didn't state what that was.

The reason you have 2 inverter chargers is because of possible load required.  It does not matter what powers what or why.  Its just a math equation again.  Make more than you use.  When dry camping you want them cranked up to recoup as much power as possible when the generator is running.  You would need to check the MFG charge rates for those AMG's.  

What are you trying to accomplish so I can tell you where to go from here.

Thank you all for the feedback so far. Very helpful. 
 

so the issue I’m having, is that the batteries do not seem to be holding a charge. These batteries are all full river AGM and 2 years old or less. I got this new to me Motorhome home last weekend... plugged into a regular 15 amp outlet, both inverters (chargers) fired up and started pumping juice to the batteries... that with the fridge on, tripped my breaker on my house. 
 

so I turned one charger off and let it do it’s thing for about 2 days. It went into float mode in about 3-4 hrs. All seems well... but as soon as I turn the chargers off (Motorhome is still plugged in, so technically I’m not using any battery power) the voltage drops kinda quick. For example I clicked the chargers off last night around 8pm. Went and checked the batteries with my multimeter and each battery is around 6.20-6.24. That is from sitting with no load for 12 hrs. 
 

both chargers were set to 80% charging power and 3.5 hours of absorption time. I will pull the battery and charger specs when I get back to my office a d post below (on my phone now)

this Motorhome came from A guy that hardly used it and kept it plugged in... but most likely to a 15amp outlet. 
 

so my theory (keep in mind I am not familiar with all this stuff) is either 

1. he would plug it in, it would trip the breaker and overtime the batteries would draw  down and die... without him ever noticing 

2. the chargers were set up wrong and he has over charged and cooked the batteries. (Though The magnum inverters were set to AGM2 mode, which is was fullriver recommends)

3. chargers set wrong and these things are not Getting fully charged and only charging to 70-75% capacity 

4. Somehow 8 newer high end batteries were all bad. 
 

idk... I’m doing my homework and trying to learn before I reach back out to the seller... because I’m pretty sure he said these were still under some warranty? I really don’t want to drop 3k for batteries if I can figure it out. One of the reasons I bought this coach was because it had all “fresh” high end batteries

 

[Lord of the Dunes]

Thank you all for the feedback so far. Very helpful. 
 

so the issue I’m having, is that the batteries do not seem to be holding a charge. These batteries are all full river AGM and 2 years old or less. I got this new to me Motorhome home last weekend... plugged into a regular 15 amp outlet, both inverters (chargers) fired up and started pumping juice to the batteries... that with the fridge on, tripped my breaker on my house. 
 

so I turned one charger off and let it do it’s thing for about 2 days. It went into float mode in about 3-4 hrs. All seems well... but as soon as I turn the chargers off (Motorhome is still plugged in, so technically I’m not using any battery power) the voltage drops kinda quick. For example I clicked the chargers off last night around 8pm. Went and checked the batteries with my multimeter and each battery is around 6.20-6.24. That is from sitting with no load for 12 hrs. 
 

both chargers were set to 80% charging power and 3.5 hours of absorption time. I will pull the battery and charger specs when I get back to my office a d post below (on my phone now)

this Motorhome came from A guy that hardly used it and kept it plugged in... but most likely to a 15amp outlet. 
 

so my theory (keep in mind I am not familiar with all this stuff) is either 

1. he would plug it in, it would trip the breaker and overtime the batteries would draw  down and die... without him ever noticing 

2. the chargers were set up wrong and he has over charged and cooked the batteries. (Though The magnum inverters were set to AGM2 mode, which is was fullriver recommends)

3. chargers set wrong and these things are not Getting fully charged and only charging to 70-75% capacity 

4. Somehow 8 newer high end batteries were all bad. 
 

idk... I’m doing my homework and trying to learn before I reach back out to the seller... because I’m pretty sure he said these were still under some warranty? I really don’t want to drop 3k for batteries if I can figure it out. One of the reasons I bought this coach was because it had all “fresh” high end batteries

You might have several different problems, or a combination of all of them.

1. As you suspect, these batteries might have been abused or discharged too far in the past.

2. A little known problem is that the more expensive the AGM batteries are, chances are they are far below their rated cap. Meaning they never stored the advertised power even when they were new.

3. You might have 1 bad battery that is drawing the entire bank down. The easiest way to find out which one (or more) is bad is to use an infrared temp gun while charging the batteries. All of the batteries should be the same temp. Any battery significantly higher than the rest is probably shorted. Any battery significantly colder than the rest is probably open and it's partner battery will also be cold, since they are in series.

If you are planning on replacing those batteries, for the same or less amount of money, you could get more power with LiFePo4 batteries and saving weight, room and they'll last well over 15 yrs. For example, the Ampere Time batteries are 200Ah and only $665 ea. 2 would only cost $1400, 4 would cost about $2800 and that would provide 800Ah, 640Ah usable at 80%. Your current battery bank is rated at 900ah with only 450Ah usable and in reality, probably not even close to that.  

I would recommend buying a Victron Smartshunt for $130, it will tell you every watt going in or out of the battery bank and tell you exactly how good or bad those batteries are.

Here's a YT video where they tested everything from the lowest priced 6v batteries to Battle Born and just about everything in between. The higher priced AGMs were the lowest performing of them all. If I were on a tight budget, I'd get Sam's Club 6v batteries, otherwise it would be LFP batteries, nothing in between.