Looking for tips to improve out setup for cold weather

[SamDeleted]

Btw I wouldn't worry too much about heating AGM , they can work well below freezing point

A lot of manufactures quote charge and draw on AGM batteries at -40f ( which surprisingly is the same temperature as -40c, you learn something new everyday)

 

[Tomthumb62]

Ok interesting, we didnt consider a smaller battery could actually help us. I dont think we would want to go too small, as we want to have enough power in case of longer periods of cloudy days and such. So I guess we will look into how large of a solar panel we can go with, if we could fit a 200w.

Do you deal with below freezing temps at all? If not, then lithium might be a better option at it doesn’t require such high charging amps that AGM does. You could still go with lithium even in freezing temps if the battery has low-temp protection, but I'm not sure if any low Ah lithium batteries have the low temp protection. You can add low-temp protection with external equipment, but that adds to cost and complexity. Charging lithium is easy compared to AGM, plus you can discharge to 10-20% without much impact to the longevity of the battery, unlike lead-acid which typically gets damaged if discharged below 50% more than occasionally.

It sounds like your power requirements are actually quite small. If you have weeks of cloudy days, then you might actually need to go with a bigger battery, but if you get sun once a week, it might be enough to charge the battery back up.

If you do go with a new setup...you might want to just do a test system and see how it compares to what you're currently doing before upgrading all your stations.

 

[SamDeleted]

unlike lead-acid which typically gets damaged if discharged below 50% more than occasionally.

True for lead-acid, not deep-cycle AGM , his batteries are 100% discharge rated , as are most AGM batteries in fact, deep discharges don't have a huge effect on overall lifetime amp output. The 50% limit is an old wife's tail

 

[SamDeleted]

Datasheet says they are 100% discharge rated

View attachment 153577


It's the same with most deep cycle AGM batteries , the 50% rule is an old wife's tail when it comes to AGM , deep discharges don't have a huge effect on over all lifetime ah output

50% discharge on AGM batteries - old wife's tail

This guy has an interesting take on the 50% discharge rule https://tab-rv.vanillacommunity.com/discussion/9940/agm-battery-depth-of-discharge-myth-busted Quote: "I have been wondering for some time if the "don't discharge your batteries beyond 50%" rule really applies to AGM batteries...

diysolarforum.com

@Tomthumb62 take a look at the link to that thread


It's all about lifetime ah output, only 6% loss when comparing 80%dod to 50%dod , not worth worrying about

 

[Tomthumb62]

True for lead-acid, not deep-cycle AGM , his batteries are 100% discharge rated , as are most AGM batteries in fact, deep discharges don't have a huge effect on overall lifetime amp output. The 50% limit is an old wife's tail

Where are these 100% discharge AGMs? I’ve never heard or seen of them.

Before we knew any better, we were 100% discharging our brand new AGMs. They lasted a year before no longer holding charge. ‘Twas a $800 lesson learned.

 

[SamDeleted]

Where are these 100% discharge AGMs? I’ve never heard or seen of them.

Before we knew any better, we were 100% discharging our brand new AGMs. They lasted a year before no longer holding charge. ‘Twas a $800 lesson learned.

In OPs battery box

 

[Tomthumb62]

In OPs battery box

View attachment 153799

150-250 cycles? How is that any better? Of course you can run any lead acid to 100% DoD, but you pay for it in reduced cycles. And remember that most likely, those 150-250 cycles were created in lab conditions, so real world results are likely much less than that.

 

[SamDeleted]

Of course you can run any lead acid to 100% DoD, but you pay for it in reduced cycles.

Yea you do pay a cost, but it's only 14% of the life time capacity (at least on paper.)

150-250 cycles? How is that any better?

That same cheap battery will only do 350-550 cycles to 50%soc .



100% drain gives you DOUBLE the capacity, so each cycle is worth 2 cycles to 50%soc .

250 x 100% cycles are equivalent to 500 x 50% cycles

 

[spwath]

We are still having some issues and are looking to improve them. Our batteries are dying in some locations that are getting a lot of cloudy weather. We are using 100w solar panels now. Bigger solar panels are not much of an option, as they take up a lot of space. I am thinking lithium batteries would help with the low charge current. Maybe bigger lithium batteries.
My one concern is charging in the cold. We dont use them too far into winter, but still can get cold.
Better insulation in the battery box will help, as our components (sound level meter, router, and single board computer) generate some heat.
My options are:

• 100 ah lithium battery with self heating
  • Self heating only heats when charging, using current from the solar panel
  • Might take too much of the power to heat it?
• 200 ah lithium battery without self heating

Any thoughts?

 

[LydMekk]

True for lead-acid, not deep-cycle AGM , his batteries are 100% discharge rated , as are most AGM batteries in fact, deep discharges don't have a huge effect on overall lifetime amp output. The 50% limit is an old wife's tail

Not TAIL...TALE...