Battery Bank Charging

[GypsyFamilyRV]

I'm experiencing some wierdness with my battery bank. I have a 2007 Keystone Montana Mountaineer. Replaced the single battery with 4 6V golf cart batteries (224AH each). Stock converter, I don't have the model right off, but it's the converter that came with the rig. I don't yet have a battery monitor, but do have a simple 0-100 percentage digital light bar. Here is what I see:

1. When I plug into shore power, no matter whether I plug into 50A or go down to 15A at a house, the batteries charge and the display reads 100%. With conservation, the charged battery bank lasts me around 7-10 days boondocking.
2. When I run my generator (Champion 3500W generator) I plug my rig's main power cord directly into the generator. Usually, I use the 30A plug, but for testing I've also gone down to the 15A.
3. When charging from the generator, I get very mixed results. Sometimes the charge meter reads 100%, but only lasts 1-2 days. The last charge I did, the meter got up to 50%, and stopped charging (the meter blinks when charging). At that 50%, I've now been running for 3 days, and haven't lost a light yet.

So, in short, I see very mixed results when charging from the generator, even letting it run for 4-5 hours. Is that normal? Am I missing something? Iwould like to have a battery monitor, but just haven't been able to get one yet. Looking to see if there's something I can do to get my charge up to 100% off of my generator.

Thanks!

Sean

[CedarCreekWoody]

I expect it will take much longer to recharge if the batteries are seriously depleted.

[Canonman]

Here is a link to Handy Bob's blog. He has a background in electrical engineering and has some interesting information about batteries, converters, solar and RV electrical stuff in general. I'd recommend giving it a read. He's helped my understanding of battery and charging systems a bunch!
https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/

[Logan X]

I recently had a slow charging issue also. My problem was a loose ground wire. The screw where the batteries grounded to the frame had vibrated loose. I tightened up the ground screw and now I’m back to optimal charging. I would check all of your connections for tightness and corrosion, starting with the ground.

On a side note, if you are depleting your batteries below 50% state of charge you are reducing their ability to hold a charge.

[GHen]

Do you have an EMS? My EMS does not like the generator and shuts down the incoming power. Not a big problem, I turn the EMS off when using the generator and then turn it back on before using shore power again.

[GHen]

I would also agree with others, never let your batteries get below 50%. With only lights as an indicator, it’s really hard to know what you really have. As you noted, You really need something that displays the voltage. How old are your batteries?
Here are some thoughts,
If your batteries are actually 224amph each, you have 448amph at 12 volts. At 50% you are depleted by 224amps. Even if your converter provides 60 amps per hour charging, you need 4 hours minimum to charge back up. ( my golf cart batteries only have 105 amph each)

It’s possible that if you have actually depleted your batteries below 50% a few times, you may have a damaged cell or two. You should have them tested at a shop with a load tester. If you have a volt meter you could test them yourself by letting them rest for a few hours, disconnecting them and checking each one separately. Using a hydrometer and checking each cell would also work.

How about water, has the water in the batteries dropped below the internal plates?

[GHen]

This may help once you can monitor voltage.

25715

[crowbar]

Do I need to be educated on this? I thought that the purpose of a deep cycle battery was to enable you to drain it right down and then charge it back up to the top multiple times. Where as a standard starting battery would not take that abuse. Now I here you guys talking about not draining off your battery beyond 50%. If I'm in the dark on this, please bring me into the light. I welcome any re-education.

[LHaven]

1. When I plug into shore power, no matter whether I plug into 50A or go down to 15A at a house, the batteries charge and the display reads 100%. With conservation, the charged battery bank lasts me around 7-10 days boondocking.

3. When charging from the generator, I get very mixed results. Sometimes the charge meter reads 100%, but only lasts 1-2 days. The last charge I did, the meter got up to 50%, and stopped charging (the meter blinks when charging). At that 50%, I've now been running for 3 days, and haven't lost a light yet.

To be clear, most displays are going to read the battery voltage. While you are plugged into shore power or generator power, they're going to be reading the charging voltage being applied to the battery, whether or not the battery will actually be accepting it. That's a great indication of the health of the converter, but it doesn't tell you anything about the health of the actual battery.

The reading that matters is what the display says about your battery when the generator is turned off / the shore power is unplugged.

Now, this may be what you were reporting, but your report was ambiguous.

If your generator is putting out the same quality power as a shore outlet, then your convertor shouldn't be able to tell the difference, and the behavior should be identical. But to pursue that further, it would be helpful to have clarification on the other issue first.

[LHaven]

Do I need to be educated on this? I thought that the purpose of a deep cycle battery was to enable you to drain it right down and then charge it back up to the top multiple times. Where as a standard starting battery would not take that abuse. Now I here you guys talking about not draining off your battery beyond 50%. If I'm in the dark on this, please bring me into the light. I welcome any re-education.

I think the secret is that most batteries that are marketed as "deep cycle batteries for RVs" aren't actually true deep-cycle batteries. If they say anything about cold cranking amps, they are not true deep-cycle batteries, which cost significantly more and are way heavier.

[crowbar]

Thanks LHaven. That clears it up a bit. The batteries I use are from Costco and are marked Golf Cart/RV . There is no mention of CCA, only that the reserve capacity is 107 minutes @ 75 amps. And they are HEAVY (for an old guy)

[LHaven]

OK, the 6V ones are true deep-cycle. It's the 12V ones that usually masquerade, and the true deep-cycle ones are really heavy.

[JRTJH]

Thanks LHaven. That clears it up a bit. The batteries I use are from Costco and are marked Golf Cart/RV . There is no mention of CCA, only that the reserve capacity is 107 minutes @ 75 amps. And they are HEAVY (for an old guy)

Your "golf cart batteries" are "true Deep Cycle batteries"....

That said, depending on how you have them connected to the charger, you may be "charging two with two in reserve" or you may be "charging all 4 batteries equally".... The same holds true for how they are being discharged. Depending on how they are connected to the 12 VDC fuse panel, you may be "discharging two batteries with two in reserve"....

Take a look at the wiring diagrams in this article, it's pretty much self explanatory on how batteries discharge and how they are recharged. If your system is connected properly, then you are discharging/recharging your battery bank "equally". On the other hand, if you have them connected incorrectly, then you're using two and the other two are "sitting there, not carrying their fair share of the load"....

https://www.impactbattery.com/blog/tutorials/how-to-charge-marine-and-rv-batteries-in-parallel/

[crowbar]

Thanks John. I only use two 6v batteries where originally the trailer had two 12v.

[Canonman]

Since Crowbar's batteries are 6vdc golf car batteries they would be connected in series. Example shows a parallel connection.
And yes, the recommended connection would be to the positive post of the first battery and the negative post of the last.
They are true "deep cycle" batteries. However, it is still recommended that lead acid batteries not be discharged below 50% capacity to prolong the overall life of the battery.
They do provide more recharge cycles than the normal "starting" battery but care should still be taken to minimize completely discharging the battery.

[Logan X]

For any flooded lead acid battery, including true deep cycle, if you discharge them below 50% state of charge, you will reduce the amount of life cycles they have. If you take them all the way down to zero you will greatly reduce the amount of life cycles they have. The life cycle is the amount of times they can be recharged. I believe this is caused by sulfation of the lead plates.

Here is a link to an interesting blog post on this

https://www.altestore.com/blog/2015/10/understanding-deep-cycle-batteries-part-2/

And this is a pertinent quote from the blog post:

The deeper you discharge the battery, the shorter its life expectancy, or Life Cycles, will be. A cycle is each time you discharge the battery and charge it back up. In an off grid solar power system, a cycle is generally a day. Looking at the example chart for Concorde Battery’s life cycles, if you use it every day down to 70% DoD (or 30% SoC) you can expect about 800 cycles. At one cycle per day, that’s just over two years. But if you only use 20% of the battery daily for 80% DoD, you can expect about 2800 cycles, or almost 8 years. Despite being called Deep Cycle Batteries, lead acid batteries do not like to be discharged deeply on a regular basis.

[JRTJH]

Thanks John. I only use two 6v batteries where originally the trailer had two 12v.

I suppose I should have used the "multi-quote" button.... The OP stated in his first post: "Replaced the single battery with 4 6V golf cart batteries (224AH each)." and I was replying to your concern about whether your batteries were "true deep cycle batteries" as well as replying to his comment about having four 6 volt GC-2 batteries in "series parallel" and having problems recharging them with his "built in converter/charger"....

The link I posted explains how batteries MUST be connected properly to "equalize" the charge/discharge capacity....

With your "two 6 volt batteries" there's not as much concern with how they "equalize" but with 4 or 6 batteries in a system, it's CRITICAL that they be wired properly or you'll "burn up the closest pair" while never charging the last pair.....

[GHen]

Do I need to be educated on this? I thought that the purpose of a deep cycle battery was to enable you to drain it right down and then charge it back up to the top multiple times. Where as a standard starting battery would not take that abuse. Now I here you guys talking about not draining off your battery beyond 50%. If I'm in the dark on this, please bring me into the light. I welcome any re-education.


All lead acid batteries have the same issue, don’t deplete below 50%, this included deep cycle.
A car battery normally won’t ever go below 20% discharge so their plates are designed lighter to be less expensive and can’t handle being deleted to 50% very often. The design is also great at dumping a large amount of amps for a few seconds to start an engine.
A deep cycle, golf cart style battery has heavier plates so it can handle getting to 50% regularly, but they also are not designed to start an engine, but will work.
Once any lead acid battery gets below 50%, it will now have less than 12 volts and some of your electronics in the rv will no longer function.

A lithium battery is designed to go very low, I’m not sure, but I don’t think it has a problem going all the way to zero.

[GypsyFamilyRV]

To be clear, most displays are going to read the battery voltage. While you are plugged into shore power or generator power, they're going to be reading the charging voltage being applied to the battery, whether or not the battery will actually be accepting it. That's a great indication of the health of the converter, but it doesn't tell you anything about the health of the actual battery.

The reading that matters is what the display says about your battery when the generator is turned off / the shore power is unplugged.

Now, this may be what you were reporting, but your report was ambiguous.

If your generator is putting out the same quality power as a shore outlet, then your convertor shouldn't be able to tell the difference, and the behavior should be identical. But to pursue that further, it would be helpful to have clarification on the other issue first.

The batteries are brand new. I double checked their water level (all good). Unfortunately, it's only a graph style display, so it just shows a level of 0-100 on charge, and there are 11 lights on it, so about 9% per light.

[GypsyFamilyRV]

Your "golf cart batteries" are "true Deep Cycle batteries"....

That said, depending on how you have them connected to the charger, you may be "charging two with two in reserve" or you may be "charging all 4 batteries equally".... The same holds true for how they are being discharged. Depending on how they are connected to the 12 VDC fuse panel, you may be "discharging two batteries with two in reserve"....

Take a look at the wiring diagrams in this article, it's pretty much self explanatory on how batteries discharge and how they are recharged. If your system is connected properly, then you are discharging/recharging your battery bank "equally". On the other hand, if you have them connected incorrectly, then you're using two and the other two are "sitting there, not carrying their fair share of the load"....

https://www.impactbattery.com/blog/tutorials/how-to-charge-marine-and-rv-batteries-in-parallel/

Thanks for the reply! My 4 are wired in series/parallel combo, like this:
https://www.google.com/search?q=wiring+6v+batteries+in+series+and+paralle l&prmd=ivsn&sxsrf=ALeKk03ylt0yNLJhCmbQqOi-CGJJbZu75g:1584999539659&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiz6J60x7HoAhWGIDQIHUCHC34Q_AUoAXoECA8QA Q&biw=1138&bih=712&dpr=2.25#imgrc=QK4OTOihcAnXSM

[JRTJH]

Thanks for the reply! My 4 are wired in series/parallel combo, like this:
https://www.google.com/search?q=wiring+6v+batteries+in+series+and+paralle l&prmd=ivsn&sxsrf=ALeKk03ylt0yNLJhCmbQqOi-CGJJbZu75g:1584999539659&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiz6J60x7HoAhWGIDQIHUCHC34Q_AUoAXoECA8QA Q&biw=1138&bih=712&dpr=2.25#imgrc=QK4OTOihcAnXSM

There are "well over 100 diagrams" on that link, so no earthly idea which one you're talking about being "like mine".....

[travelin texans]

Thanks for the reply! My 4 are wired in series/parallel combo, like this:
https://www.google.com/search?q=wiring+6v+batteries+in+series+and+paralle l&prmd=ivsn&sxsrf=ALeKk03ylt0yNLJhCmbQqOi-CGJJbZu75g:1584999539659&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiz6J60x7HoAhWGIDQIHUCHC34Q_AUoAXoECA8QA Q&biw=1138&bih=712&dpr=2.25#imgrc=QK4OTOihcAnXSM

The pic that pops up is 2 -6 volts wired parallel which equals 6 volts. If that's how yours are wired it's connected wrong.

[GHen]

The OPs batteries worked before he had these problems, unless he rewired them, they should be wired correctly.

[roadglide]

There are "well over 100 diagrams" on that link, so no earthly idea which one you're talking about being "like mine".....

I’m using 3 AGM batteries there all connected parallel. When charging 3 batteries to get equal voltage to each battery should I connect positive to positive and a negative to negative on the opposite side crossing all batteries? The way I’m charging the batteries now charging and the third battery 3 feet from the other two it’s still parallel. This is for Solar charging when I added the third battery I didn’t remove the charge cable back to the third battery . I can’t find anything online that explains three batteries for charging Parallel.

[roadglide]

I’m using 3 AGM batteries there all connected parallel. When charging 3 batteries to get equal voltage to each battery should I connect positive to positive and a negative to negative on the opposite side crossing all batteries? The way I’m charging the batteries now charging and the third battery 3 feet from the other two it’s still parallel. This is for Solar charging when I added the third battery I didn’t remove the charge cable back to the third battery . I can’t find anything online that explains three batteries for charging Parallel.

Thank you three battery Diagram is in the link . They’re wired just like I would wire two batteries.

[GHen]

Sounds like you are hooking the charger up correctly.

Some will say all battery cables need to be equal length between batteries.
Some will also say that all 3 batteries need to be the same manufacturer, model and same age.

If you are having any issues, you could unhook them and charge each separately. Then you could monitor the resting voltage and see if one is weak and drawing the other two down.

[GypsyFamilyRV]

There are "well over 100 diagrams" on that link, so no earthly idea which one you're talking about being "like mine".....

Sorry about that, thought it was a single image link. Here's the picture of how they are wired.

[GypsyFamilyRV]

The OPs batteries worked before he had these problems, unless he rewired them, they should be wired correctly.

Correct, the issue is that they charge fine on shore power, the only time I have issues is when boondocking using the generator. It makes sense that the converter shouldn't know the difference, but it behaves strangely and is inconsistent.

[Canonman]

Gypsy,
Have you tested the output from the generator? I'd use a DVM right at the genny plug. It does take several hours of charge time to completely top off a battery system like yours, so a continuous power test over and hour or two might tell you something.
Also, you'll need 14.5 to 15 volts DC to bulk charge your system. You can check this at the battery terminals while the genny is running.
If you're testing at home you could A/B test the converter output between shore and genny power. Again, test this at the battery with a DVM.
Good Luck and keep us posted

[Steveo57]

Find out what kind of converter you have. It might be that the converter is just not capable of charging the batteries up that quickly. It is most likely just not getting a good charge when running off of the generator because you might need to be running it for a lot more than a few hours to get a good charge. You really need to get a meter so you have better information to work with.

[JRTJH]

There is a substantial difference in "charge time" between "plugging into the garage outlet and the batteries are fully charged in the morning" (12-14 hours charge time) and "plugging into the generator, running it for 90 minutes in the morning and the batteries are barely charged the next morning"...

To determine if the "120 VAC/1600 watts" provided by the generator is "equal to the 120 VAC/1600 watts" provided by the garage circuit" you've got to compare "apples to apples". Voltage, watts/amps, time, size of wire carrying the power all can play an important role in making one source "charge better" than another source. Heck, even something as "insignificant" as a burnt/corroded pin on a plug adapter can "throw a wrench into the works"....

It's going to take a "side by side/apples to apples" comparison of the two power sources to determine if they are actually providing the converter/charger with the same power. If they are, then it's "time, not the converter" that's the issue.

[GypsyFamilyRV]

There is a substantial difference in "charge time" between "plugging into the garage outlet and the batteries are fully charged in the morning" (12-14 hours charge time) and "plugging into the generator, running it for 90 minutes in the morning and the batteries are barely charged the next morning"...

To determine if the "120 VAC/1600 watts" provided by the generator is "equal to the 120 VAC/1600 watts" provided by the garage circuit" you've got to compare "apples to apples". Voltage, watts/amps, time, size of wire carrying the power all can play an important role in making one source "charge better" than another source. Heck, even something as "insignificant" as a burnt/corroded pin on a plug adapter can "throw a wrench into the works"....

It's going to take a "side by side/apples to apples" comparison of the two power sources to determine if they are actually providing the converter/charger with the same power. If they are, then it's "time, not the converter" that's the issue.

Thanks, and this makes total sense, I just don't quite have all the pieces yet. Although, the batteries are brand new, and the gen is brand new as well (maybe has 40-45 hours on it currently). I have left the generator running for around 5 hours before, after about 4 hours, the batteries just stopped charging (at least according to the cheapo monitor I have). I'm looking at battery monitors, any recommendations for a decent one that's not too expensive?

Thanks everyone for the replies!

Sean

[JRTJH]

IMHO, without spending lots of money, a simple voltmeter is the "best charge indicator" you can own. Measure the voltage at the battery terminals. Turn on the generator and measure the voltage at the battery terminals. If it goes up (and it will if the charger is operating properly) you can divide the "no charge voltage by the charge voltage" to determine the "percentage of charge" being applied to the battery bank.

Simple to use, simple to calculate, but it's more complicated than "push a button and walk away"... Again, IMHO, we've "dumbed down logical thinking" to the point that many people simply can't comprehend WHAT and WHY they are doing a test. They "just want the results" and have NO EARTHLY IDEA what the results mean beyond what the "red/green indicator" reflects.....

So, if you have a HF $6 voltmeter, use it and "think beyond what the reading indicates to "what the reading means with that indication".... In other words, if you think about what you're doing, it'll all make sense.....

[GHen]

If can’t spend a lot, Go to harbor freight and pick a volt meter, they are about $6. Even one that plugs into one of your 12 plugs inside the rv will work.
While running the generator, check the battery voltage.
12.7 or less means they are not charging.
Around 13.1 or above means they are charging.

Some converters will charge at various voltages until they are charged. Mine starts at 14.1, then drops to 13.6, then 13.1 as the batteries get charged.

Then turn off the generator and let it rest for about 30 minutes and use this charge to see how much charge your batteries have.

25751

[LHaven]

Sorry about that, thought it was a single image link. Here's the picture of how they are wired.

Theoretically, these are wired correctly. Practically, they are not.

This diagram shows both output cables connected to the upper set of batteries. For an even charge and discharge, ONE of them (not both) should be relocated to the lower set.

[Logan X]

I use the Victron BMV 700 and I am very happy with it. It’s about $150. If you will be doing any boondocking it is well worth the price.

https://www.amazon.com/Victron-Energy-Battery-Monitor-BMV-700/dp/B01BVQR0V8

It uses a shunt to monitor exactly what is coming in and out of your batteries. It will tell you the exact state of charge in % , voltage reading, amp hours used, amp hours remaining, and all sorts of good info.

[GypsyFamilyRV]

IMHO, without spending lots of money, a simple voltmeter is the "best charge indicator" you can own. Measure the voltage at the battery terminals. Turn on the generator and measure the voltage at the battery terminals. If it goes up (and it will if the charger is operating properly) you can divide the "no charge voltage by the charge voltage" to determine the "percentage of charge" being applied to the battery bank.

Simple to use, simple to calculate, but it's more complicated than "push a button and walk away"... Again, IMHO, we've "dumbed down logical thinking" to the point that many people simply can't comprehend WHAT and WHY they are doing a test. They "just want the results" and have NO EARTHLY IDEA what the results mean beyond what the "red/green indicator" reflects.....

So, if you have a HF $6 voltmeter, use it and "think beyond what the reading indicates to "what the reading means with that indication".... In other words, if you think about what you're doing, it'll all make sense.....

I have a Voltmeter. Next time I fire up the Gen, I will try this, thank you!

[GypsyFamilyRV]

Theoretically, these are wired correctly. Practically, they are not.

This diagram shows both output cables connected to the upper set of batteries. For an even charge and discharge, ONE of them (not both) should be relocated to the lower set.

I'll definitely look into this, because this is exactly how I physically wired them.

Thank you!

[LHaven]

I'll definitely look into this, because this is exactly how I physically wired them.

Thank you!


Six months ago, I would have done exactly the same, considering the connecting cable between them to have such a low resistance as to be insignificant compared to the rest of the system. Apparently, that is not true, as explained by the veteran mechanics here.

[flybouy]

When the auto manufacturers went away from analog gauges and stated using warning light only my father called them "idiot lights". I believe that's what you are relying on for your battery information.

[roadglide]

Sounds like you are hooking the charger up correctly.

Some will say all battery cables need to be equal length between batteries.
Some will also say that all 3 batteries need to be the same manufacturer, model and same age.

If you are having any issues, you could unhook them and charge each separately. Then you could monitor the resting voltage and see if one is weak and drawing the other two down.

I connected my 3 batteries correct and connected the 3 amp trickle charger it was reading 60 % incorrect connection was 80% . I ran the generator building up the voltage of the third battery . With the batteries connected right the 3 amp charger is reading full. I have 3 agm Everready 115 amp hour batteries going on 3 years old . Reconnect the control charger now the panels will charge the the batteries equal. It’s in the poll barn but it should charge the same as the 3 amp trickledown charger. I was having havoc with my volt meter wired directly to the batteries hopefully it will be more consistent. Should the volt meter be wired the sam as solar charger?

[bbells]

Some generators and converters don't get along. Borrow or rent a high amp charger and try that. If it works fine then your gen and conv don't like each other.

[JRTJH]

Some generators and converters don't get along. Borrow or rent a high amp charger and try that. If it works fine then your gen and conv don't like each other.

Remember this: If you connect a charger to the battery bank AND leave the converter connected (and powered on) they (converter and stand alone charger) will "compete with each other"... What typically happens is the stand alone charger will supply enough power to turn off the "charging sensor" in the converter and the converter will produce enough voltage to turn off the "charging sensor" in the stand alone charger....

In other words, with two voltage sensing circuits "competing with each other", neither one will "see a charge required condition" at their connection at the battery terminals....

So, disconnect the converter (turn it off, unplug it, or disconnect it) if you're going to "clamp a stand alone charger" to the battery terminals.....

[GHen]

I think JRTJH is right on. Good advice.