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Old 03-22-2020, 11:11 PM   #1
GypsyFamilyRV
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Battery Bank Charging

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
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Old 03-23-2020, 05:30 AM   #2
CedarCreekWoody
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I expect it will take much longer to recharge if the batteries are seriously depleted.
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Old 03-23-2020, 05:47 AM   #3
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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/...ging-puzzle-2/
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Old 03-23-2020, 06:22 AM   #4
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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.
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Old 03-23-2020, 07:06 AM   #5
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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.
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Old 03-23-2020, 07:21 AM   #6
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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?
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Old 03-23-2020, 07:23 AM   #7
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This may help once you can monitor voltage.

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Old 03-23-2020, 10:25 AM   #8
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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.
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Old 03-23-2020, 10:40 AM   #9
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Quote:
Originally Posted by GypsyFamilyRV View Post
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.
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Old 03-23-2020, 10:42 AM   #10
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Quote:
Originally Posted by crowbar View Post
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.
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Old 03-23-2020, 11:34 AM   #11
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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)
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Old 03-23-2020, 11:37 AM   #12
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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.
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Old 03-23-2020, 11:43 AM   #13
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Quote:
Originally Posted by crowbar View Post
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/t...s-in-parallel/
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Old 03-23-2020, 12:02 PM   #14
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Thanks John. I only use two 6v batteries where originally the trailer had two 12v.
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Old 03-23-2020, 12:08 PM   #15
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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.
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Old 03-23-2020, 12:14 PM   #16
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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/...teries-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.
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Old 03-23-2020, 12:17 PM   #17
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Quote:
Originally Posted by crowbar View Post
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.....
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Old 03-23-2020, 12:18 PM   #18
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Quote:
Originally Posted by crowbar View Post
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.
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Old 03-23-2020, 01:37 PM   #19
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Originally Posted by LHaven View Post
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.
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Old 03-23-2020, 01:40 PM   #20
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Quote:
Originally Posted by JRTJH View Post
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/t...s-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_AUoAXoECA8Q AQ&biw=1138&bih=712&dpr=2.25#imgrc=QK4OTOihcAnXSM
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