Battery and charger recommendations?

PNW_Steve · December 2017

Hey Everyone,

I am working on the DC side of the electrical in my skoolie. I have been going round & round looking at battery options.

I had about decided just to go with 8 of the Duracell GC2's then I saw the Renogy 12v 200AH AGM's and I can get 4 of them and be carrying less weight & using less space. Anyone have any experience with these?

I am also open to other suggestions for batteries. I am looking for 24v 400AH combined. I understand that I will have more usable capacity with AGM versus FLA.

When it comes to chargers I am really lost. I had started out looking at the RV converter/chargers and found some "intelligent" 3/4 stage units but upon researching them I found that they are very limited in setting up charge parameters.

What would you all recommend for a reasonably priced charger for the AGM battery bank?

Thanks

Stephen

Estragon · December 2017

AGM doesn't give you more usable capacity (AH), but may be better for high current (eg engine starting) applications. Pound for pound, any lead acid battery will be about the same in terms of storage capacity.

As well as (sometimes, often?) tending to withstand higher charge/discharge rates, AGMs tend to have lower self-discharge rates, which can be a factor if the batteries will sit for months with no charge source, especially if warm/hot. In marine applications, they also work in odd orientations that would otherwise spill with flooded.

The downside is they tend to be more expensive than flooded (apples to apples), and tend to not last as long in deep cycle applications because of the inability to monitor SG and maintain accordingly.

If you decide on AGM for a house bank, be sure the battery manufactures recommended charging spec has a reasonably close match to the charger options, and make sure the charger has temperature compensated charging, ideally with a remote battery temp sensor. AGMs can be quite sensitive to high voltage charging, and can be ruined quickly if they vent gas, or ruined slowly by sulfating with a too low temp compensated absorb voltage.

BB. · December 2017

I did a quick look, but did not find his post. Marc Kurth, who sells AGMs (and other) batteries had some suggestions... Hopefully, he can reply.

Or you can try sending him a private message.

http://forum.solar-electric.com/messages/add/Marc Kurth

-Bill

PNW_Steve · January 2018

Thanks for the replies.

Please help me understand: "AGM doesn't give you more usable capacity (AH)"

If I have a 400 A/H FLA bank that I can safely take to 50% DOD I will have 200A/H of usable capacity.

If I have a 400 A/H AGM bank that I can take safely to 80% DOD I will have 320 A/H of usable capacity.

It's been 30+ years since my last math class. As best I can figure 320 is more than 200. What am I missing?

Also, can anyone make recommendations regarding chargers? I have not had much luck, so far, finding anything other than the RV converter chargers and forklift chargers. Neither look like the best solution for my application?

Lastly, has anyone here had any experience with Renogy batteries?

Thanks again.

mike95490 · January 2018

You can take any of them to 50% or 80%. Deeper discharges give you fewer total cycles. FLA or AGM

Renogy batteries

i don't think they actually MAKE batteries, I suspect they are re-branded somethings. That may make warranty claims fun,

mcgivor · January 2018

The depth of discharge will have an effect on life expectancy, flooded or AGM, the deeper the discharge the fewer the cycles, both types are still essentially the same chemistry. Manufacturers claims are based on accelerated testing in laboratory conditions which are very different from real life, the ability to recharge fully immediately after discharge, controlled temperature and so forth. There are flooded battery manufacturers which claim discharge to 80% as well as AGM, but the rule of thumb is, it's best to limit it to 50% maximum for better life expectancy. Not all LA batteries are created equal regardless of type, more robust types, tubular for example, are better suited to deep discharge applications, albeit at a higher initial cost.Therefore it's best to assume they're equal, same manufacturer, in terms of capacity, the application of which to choose should be dependent primarily on what is better suited, lower maintenance, orientation etcetera. Attached are pdf files for offerings from the same manufacturer which demonstrate the life expectancy versus depth of discharge for both flooded and AGM. One advantage of flooded is the ability to more closely monitor what is happening inside the cells and the ability to correct weak cells through equalization, something not possible with AGM. Just a collection of thoughts.

2manytoyz · January 2018

I had 8 of the Duracell GC2's in my solar power setup at home. They lasted 4 years. I had gotten a year longer with the previous set of Energizer GC2s. Very hot in FL, and heat limits the life of batteries.

I replaced them with Trojan T105 batteries for $112 from the local golf cart shop. I then added the Trojan Hydrolink system to water them - much easier than manually filling them.

When solar isn't cooperating, I use an Iota 75A charger to get the job done. I added an IQ Controller to make it a 4 stage charger. While I can't change the settings, it does an excellent job right out of the box. I can unplug the IQ module, put in a supplied jumper, and force it to charge at 14.2V (fast charge). Details of the IQ Module here: https://www.iotaengineering.com/iq.htm

Pics and details of my battery bank here: http://www.2manytoyz.com/battbank2017.html

OldMan · February 2018

I can only hope the next 10 years brings an end to lead-acid batteries. Barbaric, dangerous antiques.

Raj174 · February 2018

@OldMan

I think they will be around for some time to come. They are cheap and they work in colder weather than LFP.

OldMan · February 2018

Raj174 said:

@OldMan

I think they will be around for some time to come. They are cheap and they work in colder weather than LFP.

Barbaric, dangerous antiques. Why is it, Americans are all convinced cheap and convenient is good, no matter what?

mike95490 · February 2018

Because below 40F LFP starts to loose power quickly, and below 32F ( 0C ) they cannot be recharged.

Estragon · February 2018

I agree LA will be around for some time yet.

That said, the low-temp issue is solvable by heating the bank a bit. It isn't hard to imagine a scenario in which the massive increase in lithium based battery production coming online in the next few years isn't matched by an equally large increase in EV demand, driving battery pricing way down. If they get cheap enough, I can deal with the low temperature charging problem.

Hoping my banks last long enough to see if that scenario plays out.

BB. · February 2018

Also, lead acid batteries are almost 100% recycled in the USA these days. There is almost no recycling (I think) of Li Ion batteries at this point (virgin materials still are cheaper than recycled/recovered Li Ion).

Now--The battery scrap yards/recyclers have a reputation of not being very "clean"... Another issue.

-Bill

Wheelman55 · February 2018

PNW_Steve said:

When it comes to chargers I am really lost. I had started out looking at the RV converter/chargers and found some "intelligent" 3/4 stage units but upon researching them I found that they are very limited in setting up charge parameters.

What would you all recommend for a reasonably priced charger for the AGM battery bank?

Thanks

Stephen

This guy will make you a charger to your batteries specs: https://quickcharge.com/

He builds them in OK. He made me one for my two T105's. Works great.

OldMan · February 2018

mike95490 said:

Because below 40F LFP starts to loose power quickly, and below 32F ( 0C ) they cannot be recharged.

Welp, my intent is to not be in those kind of temperatures. It can be done. Snow, after all, is morally reprehensible, especially when it's yellow, and I want nothing to do with it.

I can set up a little propane heater outside the rig, use aircraft scat tube to create a duct and blow enough warm air to keep 'em warm, lose that cool, so to speak. I know where to get scat tubing.

westbranch · February 2018

Why not duct some heat from the onboard Furnace? ( heater(s)? ) into the Batt area?

edwardphillips · February 2018

Eventhough lead acid batteries are inexpensive it was avoided due to thermal runaway that occurs due to improper charging.

Battery and charger recommendations?

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