How to charge 3 batteries from the power converter?

[Kerry and Mark]

I have a new to me 2023 22MLE and we mostly are off grid. I have 3, group 31, deep cell marine batteries connected in parallel to our trailer. The power converter must only be charging one battery as they are 100 amp hour each and when the monitor says “charged” we are getting a day or less with them and I estimate we’d be using about a 100 amp hour each day. We only use the fridge on off grid mode. My questions are; are group 31 okay to use as I see my owners manual recommends group 24 and 27?When I run my generator to charge the batteries, how can I get all 3 to be charged? I don’t see any settings on the power converter to change from 1-3 batteries. Thanks, Kerry

 

[huntr70]

I have a new to me 2023 22MLE and we mostly are off grid. I have 3, group 31, deep cell marine batteries connected in parallel to our trailer. The power converter must only be charging one battery as they are 100 amp hour each and when the monitor says “charged” we are getting a day or less with them and I estimate we’d be using about a 100 amp hour each day. We only use the fridge on off grid mode. My questions are; are group 31 okay to use as I see my owners manual recommends group 24 and 27?When I run my generator to charge the batteries, how can I get all 3 to be charged? I don’t see any settings on the power converter to change from 1-3 batteries. Thanks, Kerry

As long as they are hooked up correctly, they should all charge without changing any settings.

Maybe a bad cell in one of them is drawing all of them down....

 

[Kerry and Mark]

Great, thank you for this feedback. We’ll look into the battery health. Thanks again!

 

[jim_de_hunter]

Which monitor are you using. The display on our 21BHE had to be reset when I added the second battery.

 

[Kerry and Mark]

Hi Jim, thanks for the response. Not sure if I understand your question. I use the battery monitor in the front storage compartment and did increase the amp hours to 300 but that’s the only change I made. When I look at the “connect” display inside the camper it says “fully charged”. How can I reset the monitor? Thanks, Kerry

 

[jim_de_hunter]

Mine has this unit installed in the passthrough.

https://www.amazon.com/gp/aw/d/B075...&pd_rd_r=0fa72081-f184-4726-b19c-12d37221c1b7

The % charge displayed is based on its setpoint. I have to tell it what is 100% charge and what is 0% charge. I'm running lead acid batteries so I've told it it is at 100% at 164 Ah and 0% at 82 Ah.

 

[Kerry and Mark]

Okay, thanks Jim. This is helpful, I’ll just figure out how to do this. Thanks again! Kerry

 

[Lostinspace]

In my mind 300amp hours is a little light, depends on what kind of power draw you have. I discovered on my new to me 2022 399 that I would get 4 to 5 hours per 100amps with lead asid battries. I do have inverter and residential fridge, do very power hungry. I did switch to lithium and bumped up the solar, so now can camp indefinitely as far as power goes

 

[Riverbug]

All good advice here. Just wanted to add that you'll want to try not to deplete those batteries below 50% as that causes degradation and shorter life on lead acid batteries. The reason people only get 2 or 3 years out of them is because the batteries are left connected and draw down to 0% before they realize it, or consistently drawn below about 50%. Keep them charged and above 50% and you'll get several years out of them.

 

[Jomani]

Just piggybacking on what Chad said, your 300ah battery bank will only deliver about 150ah of usable power before getting to the point where the voltage drops below 12 volts.

I am not familiar with your rig, but If you have a 12v refrigerator, you should also have solar. If that is the case, the solar should theoretically provide enough power to keep the refrigerator going, so 100ah draw per day seems a little high.

 

[TimtheToolMan]

I have a new to me 2023 22MLE and we mostly are off grid. I have 3, group 31, deep cell marine batteries connected in parallel to our trailer. The power converter must only be charging one battery as they are 100 amp hour each and when the monitor says “charged” we are getting a day or less with them and I estimate we’d be using about a 100 amp hour each day. We only use the fridge on off grid mode. My questions are; are group 31 okay to use as I see my owners manual recommends group 24 and 27?When I run my generator to charge the batteries, how can I get all 3 to be charged? I don’t see any settings on the power converter to change from 1-3 batteries. Thanks, Kerry

Marine batteries are not true deep cycle so maybe limited to the 50%(?) limit that is frequently stated, while true deep cycle and especially AGM deep cycle are rated to 80-100% discharge. On average with a good battery (great is not cost effective) and proper use, 8 year life is common. Go to the manufacture and they all will tell you this. Marine are fine for some situations and may fit your need. Those that say that below 50% did not work for long at all (I fully believe them!) NOT ALL are not using shut, watching how soon batteries are fully charged, storing at below 80% SOC, equalizing, keep fluid up, and a few other (all things that we humans are not good at constantly doing and choose not to do...)

Look into checking specific gravity of each cell as this is the real test of battery health.... equalizing...easier than you think. Measuring produced Ah is very good but takes time and equipment (shunt and any load/equipment running).

The key is not how low they are discharged but how soon they are fully charged and if they are stored above 80% SOC. Yes, the longer that they are held lower the shorter the life and this has little to do with cycles so these batteries rarely see a lot of cycles but age out or lack proper charging.

Others have likely mentioned, right now there are quality 100Ah LPF batteries in the $150-190 range. True deep cycle and especially AGM are no longer cost effective unless there is no desire to go through hassel of upgrading or are selling before too long. Marine may fit this bill. LPF are more reliable/lower maintenance especially with BMS but are not bullet proof.

 

[CedarCreekWoody]

Be sure the positive cable from your converter connects to battery #1 and the negative cable to ground connects to battery #3 (not battery #1). This will force the charge to flow through all three batteries.

 

[Butcher]

while true deep cycle and especially AGM deep cycle are rated to 80-100% discharge.

Care to show evidence of this? I did a quick Google check and did not see any manufacturer that recommended anything less than 50%.

 

[Riverbug]

Marine batteries are not true deep cycle so maybe limited to the 50%(?) limit that is frequently stated, while true deep cycle and especially AGM deep cycle are rated to 80-100% discharge. On average with a good battery (great is not cost effective) and proper use, 8 year life is common.

Actually, AGM is just a different type of lead acid. It is definitely not rated for 80-100% discharge. I promise you that if you repeatedly deep discharge or let them go dead, you'll get as much life out of them as a flooded lead acid or any other lead acid - 2, maybe 3 years. If you want to get that level of discharge and keep the longer life, then you need to go with lithium. If you keep AGM or flooded cells charged up, don't deep discharge them, then 6-8 years is certainly attainable.

 

[Butcher]

If you want to get that level of discharge and keep the longer life, then you need to go with lithium.

To be fair, if you discharge a LifePo4 battery to 0 volts. the battery would be ruined instantly.

Because of the BMS, you cannot reach that level.

 

[Riverbug]

To be fair, if you discharge a LifePo4 battery to 0 volts. the battery would be ruined instantly.

Because of the BMS, you cannot reach that level.

Well, not really a fair comparison because lead acid batteries have no BMS to keep it from discharging to 0 and lithium batteries do. But I understand what you're saying. However, adding to your point, discharging an LFP battery to 10V and letting it sit that way for weeks will also cause degradation (can be catastrophic). You do need to recharge them immediately. But you can say the same for an AGM battery left to sit dead for a few months.

 

[Butcher]

If someone designed a BMS for a LA battery, it would shut off when it dropped down to about 10v. That way, it would prevent a full discharge and add life to the battery.

I am not insinuating that LA are better in any way, but when people say a complete discharge, that means [to me] 0 volts. You just cannot achieve that with a properly designed LifePo4 battery. So, it's kinda like cheating.

Saying that a LA battery has 100ah but you need to go to 0v, is also cheating because you are slowly killing a battery. That rating to me is kinda cheating too.

I don't sell batteries and with LiFePo4 batteries that are available, I see no purpose for a LA battery anymore.

 

[triplethreat]

If someone designed a BMS for a LA battery, it would shut off when it dropped down to about 10v. That way, it would prevent a full discharge and add life to the battery.

I am not insinuating that LA are better in any way, but when people say a complete discharge, that means [to me] 0 volts. You just cannot achieve that with a properly designed LifePo4 battery. So, it's kinda like cheating.

Saying that a LA battery has 100ah but you need to go to 0v, is also cheating because you are slowly killing a battery. That rating to me is kinda cheating too.

I don't sell batteries and with LiFePo4 batteries that are available, I see no purpose for a LA battery anymore.

Just a thought here (yea, I know, that could be dangerous..LOL), but what about buying something like an external BMS like I used when I built my LFP battery and using it on a FLA battery? Obviously you aren't going to get individual cell voltage readings, but going into the app, couldn't you set the LVC to say 10V.....or 11V or whatever you wanted it set at?
Caution: The above statement was NOT a well thought out answer, just a quick thought that came to me....in other words, there may be good reasons that something like that may not work and is a "Duh" moment.

 

[Butcher]

As an idiot as I am, I thought of that but since the BMS does need the individual cell readings for it to work, I suspected it would not. I know, a waste of time thinking about that, but I did have a glass of beer with me, so it was not a total waste of time.

I am certain, there are some low voltage cut off switches that someone makes. Again, after learning about LiFePo4 batteries, I've turned the page on LA batteries.

 

[Hoopy Frood]

Just a FWIW, Blue Sea offers a low voltage cutoff that is adjustable. So you could set the cutoff voltage.