Low power output from batteries

[jkwilson]

Agree. But FLAs that I think the OP has (I looked on Oreillys website are the worst of the bunch. They offgas under normal use. No overcooking needed.

Two different situations.

During normal charging, vented lead-acid batteries release hydrogen gas. This is a fire hazard and needs to be vented to the outdoors.

When over charged or charged with low electrolyte levels, any lead-acid battery will release both hydrogen and hydrogen sulfide gas. H2S is both flammable and toxic and most definitely needs to be vented.

 

[huntindog]

Two different situations.

During normal charging, vented lead-acid batteries release hydrogen gas. This is a fire hazard and needs to be vented to the outdoors.

When over charged or charged with low electrolyte levels, any lead-acid battery will release both hydrogen and hydrogen sulfide gas. H2S is both flammable and toxic and most definitely needs to be vented.

Thanks for typing a detailed explanation
Basically we agree that since FLA batteries ALWAYS offgas, that they are in my words: The worst of the bunch.

 

[WhittleBurner]

I am not sold on lithium with all the reports of fire with lithium. City's have quit buying anything with lithium due to that.

 

[triplethreat]

I am not sold on lithium with all the reports of fire with lithium. City's have quit buying anything with lithium due to that.

Whittle.....there is a HUGE difference between Lithium Ion batteries and the Lithium/Iron/Phosphate type batteries. The LFP or LiFePO4 batteries like that would be used in an RV are almost impossible to create a fire or catch fire. Lithium Ion on the other hand, a lot easier, especially when overcharged. Sometimes the term Lithium battery is used without regard for the actual chemistry type, and unfortunately, some believe that any Lithium based battery is bad/dangerous/etc.

 

[Second Chance]

Hi All,

I'm having issues with my solar setup. I checked my batteries and they were at 100%, however, when I use my single hot plate, or even egg cooker, my inverter does the low power alarm. The only things directly on my fuses are my efficient DC fridge and LED lights. It's frustrating that even with 300+ Ah I can't seem to use a hot plate for more than 3-4 minutes or my egg cooker. I have 3 solar panels on the roof and my battery meter consistently shows 75-100% battery levels. I bought them a month ago, 31DCM marine super start batteries from Oreilly's. Did I do something wrong? Are all 3 batteries in parallel? I am somewhat concerned about "ground looping" - however, since the one isolated battery is underneath my passenger seat and the other 2 are in the trunk area, I attached all 3 to the chassis. Any help would be greatly appreciated!

As several members have guessed, you may have a van camper or motorhome. I just wanted to let you know that this is a site geared toward owners of Grand Design recreational vehicles. Most are towables, through Grand Design has recently introduced one motorized line.

All this to say that you may find help more specific to your RV on a forum dedicated to that RV. Otherwise, the general electrical concepts hold true and you'll get some good advice here.

I'll just throw in the fact that lead-acid batteries are only good for about 50% of their rated amp hours before they're drawn too low to recover. Lithium (LiFePO4) will give almost 100%. As stated by others, appliances that use resistive heat or things like microwaves draw HUGE amounts of energy and will draw down batteries much more quickly.

Rob

 

[Riverbug]

I am not sold on lithium with all the reports of fire with lithium. City's have quit buying anything with lithium due to that.

Please read what @triplethreat said. There is no comparison in safety between Lithium Ion and LiFePO4 batteries which is what we all talk about here. It didn't occur to me that anyone was thinking Lithium Ion for this type of use. I think that's a good reminder to those of us who have been building or buying them for a while now.

It might be likened to talking about how explosive fuel is, but one is talking about gasoline and the other is talking about diesel. They have very different reactions to flame or spark.

 

[acelaube]

Hello there!

yes, it is a remodeled van. I wasn't aware that this site was geared towards a specific rv brand, so I apologize - I was on google searching for a forum to ask questions on, and this was the first one that came up. I have a Mercedes sprinter 3500.

As far as battery safety, they are all underneath the bed, near the rear doors. While exterior ventilation in this area is minimal, my batteries have been there for the past 6 years with no issue (I have replaced them recently), it doesn't seem to be a problem? I appreciate the concerns and I will take into account the LiFePO4 and other notes next time I have to buy batteries.

That said, they are all brand new batteries, purchased in February 2025. The issue may be the wiring to the inverter. Before posting this I had 2 sets of cables going from the inverter to the batteries. While I was cleaning up the wiring (and moving all the batteries to the same location), I removed the second set of wiring going from the inverter to the batteries. I believe this may be what's causing the inverter to fail out. Unfortunately I don't currently have a way to test this, but unless someone has a better idea, that (and the only 300Ah with lithium ion) is my prevailing theory.

 

[huntindog]

Hello there!

yes, it is a remodeled van. I wasn't aware that this site was geared towards a specific rv brand, so I apologize - I was on google searching for a forum to ask questions on, and this was the first one that came up. I have a Mercedes sprinter 3500.

As far as battery safety, they are all underneath the bed, near the rear doors. While exterior ventilation in this area is minimal, my batteries have been there for the past 6 years with no issue (I have replaced them recently), it doesn't seem to be a problem? I appreciate the concerns and I will take into account the LiFePO4 and other notes next time I have to buy batteries.

That said, they are all brand new batteries, purchased in February 2025. The issue may be the wiring to the inverter. Before posting this I had 2 sets of cables going from the inverter to the batteries. While I was cleaning up the wiring (and moving all the batteries to the same location), I removed the second set of wiring going from the inverter to the batteries. I believe this may be what's causing the inverter to fail out. Unfortunately I don't currently have a way to test this, but unless someone has a better idea, that (and the only 300Ah with lithium ion) is my prevailing theory.

I am not sure how many will now respond. I almost ignored this. My reason is simple... Since you do not think breathing battery fumes is a problem...I do not want to help you cause harm...But at my job before I retired. I was the safety coordinator....Old habbits never go away.
Please either get those batteries properly sealed from the living area and vented to the outside. Or replace them with LiFePO4s now.
You only get one set of lungs

 

[redfernclan]

Got to agree here. Just read all the posts for the first time and good recommendations throughout but with the understanding things all are done safely.
Lead acid batteries in a living compartment are a ticking time bomb.
I don't care if it has worked for years, One faulty battery, one hiccup, one corroded connection increasing resistance in the circuit and you have a life threatening situation.
I spent 10 years as a heavy equipment diesel mechanic and 26 years working on battery forklifts and other building and conveyer maint.
My recommendation would also be to fix the safety concerns first. By re-doing your system you may be able to engineer fix's for your other issues and solve your problem.

 

[JPS350]

Unfortunately I don't currently have a way to test this, but unless someone has a better idea, that (and the only 300Ah with lithium ion) is my prevailing theory.

A couple of ways to check this. Measure the distance the cable run is between the batteries and inverter. Get the input current specs for the inverter, and plug these values in addition to the wire size into an online voltage drop wiring size calculator. A 1% voltage drop would be great. Anything over 3% is probably causing issues.

Alternatively, with your high loads switched on, measure the voltage at the inverter input terminal, and also measure the voltage at the batteries where the inverter wiring is attached. This will tell you if you have a big voltage drop due to undersized wiring or you have a weak or undercharged bank. You can also do the voltage drop test over the wiring (ie, pos meter lead at the battery pos and neg lead at the inverter pos). This measures the drop caused by resistance in the wiring directly. Note that high resistance in the wiring run can be caused by too small wiring, dirty contacts, bad crimps and cheap crimp connectors, cheap or bad inline fuses, or a combination of all the above.

Concerning venting lead acid batteries, it's a very good idea to get this right. That said, in the marine world, particularly sailboats which is what I'm most familiar with, lead acid batteries have been installed unvented in boat cabins for years without problems.