Need advice on replacing lead battery to AGM or Lithium? - Fiberglass RV



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Old 07-10-2019, 10:36 AM   #1
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Question Need advice on replacing lead battery to AGM or Lithium?

Here is my current setup. 13 ft Casitas


1. I have a standard multi stage charger and a solar panel wire to battery
2. Lead acid battery
3. NO converter. Everything is wire from the battery directly to fuse box then to lights and (a rarely used water pump).
4. Basically battery powers only the LED lights 95% of the time.

What is cost effective? AGM or Lithium?
Do I need another type of charger for either of the above?
Do I need anything else to make the change to AGM or Lithium?
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Old 07-10-2019, 10:53 AM   #2
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Quote:
Originally Posted by Losthwy View Post
Here is my current setup. 13 ft Casitas


1. I have a standard multi stage charger and a solar panel wire to battery
2. Lead acid battery
3. NO converter. Everything is wire from the battery directly to fuse box then to lights and (a rarely used water pump).
4. Basically battery powers only the LED lights 95% of the time.

What is cost effective? AGM or Lithium?
Do I need another type of charger for either of the above?
Do I need anything else to make the change to AGM or Lithium?
You havent said WHY you are changing.
Why not stick with lead?
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Old 07-10-2019, 11:30 AM   #3
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AGM batteries will work fine with 99 percent of chargers designed for regular lead acid batteries. I got a Vmax Tank AGM and made no changes, using a CTEK charger, Progressive Dynamics converter and Bogart Engineering Solar Charger.

Lithium batteries are expensive and will likely require replacing all chargers.

SEE: Converting to Lithium

To me its simple. AGM.
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Old 07-10-2019, 07:36 PM   #4
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I did a conversion to a lithium battery in a Lil Snoozy (you can search for the thread detailing the conversion). For your needs as described, I would stick with lead acid. To convert to Li, you would almost certainly need to change out your charger and maybe some wiring. It is hard to say about your solar without knowing more. I spent about $1500 on my conversion and am guessing you could do a lights-only system for $500 or so. But I would just stick with what you have or go to a modest AGM (like 70 amp hour).

AGM is lead acid, by the way, you just don't have to worry about adding water or venting problems.
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Old 07-11-2019, 10:12 AM   #5
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Thanks for replies. It does seem lithium is a bit pricey.
Reason for possible change is old battery not holding power like it use to.
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Old 07-11-2019, 10:48 AM   #6
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Batteries

For heavy battery use Lithium is most cost effective when all factors are considered. Li can be discharged 100%, lead acid only 50% max. much less physical battery required because Li are physically smaller and fewer are required and they charge faster and last longer. But in your case of limited use and the initial expense of upgrading charger for such a small battery bank the lower initial outlay or lead acid is my choice. AGM are more expensive than other deep discharge batteries and less AH for size. Unless you need the ability to store the battery on it's side or installing it in your living space or just want to never have to need to check electrolite a good deep discharge battery of adequate AH rating would be my choice. Not a battery just labeled marine or marine starting.
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Old 07-11-2019, 04:56 PM   #7
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I would think the most cost effective is sticking with your leaded battery since you have such low power demands. You mentioned you have a solar panel connected to your battery, but is there a solar charge controller in the circuit so that you don't end up overcharging the battery, which can kill it just as dead as undercharging.
Sounds like your DC needs are light so the standard (and cheaper) lead acid battery (look for deep cycle) should work well as long as voltage is not allowed to get too low or overcharged.
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Old 07-17-2019, 11:33 AM   #8
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J Ron and Air Doug:

AGM batteries still require venting to the outside.

Electrical Myths, Part 4: AGM Batteries Don't Need Venting - RV Nerds

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Old 07-17-2019, 12:43 PM   #9
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Venting AGM.

Thank you, I stand corrected. AGMS have a valve that allows venting under a fault condition. Thanks for preventing me continuing the myth that AGMS don't require venting, that will create an unsafe condition.
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Old 07-17-2019, 01:01 PM   #10
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Exclamation Lithium Facts vs. Lore

Most "drop-in replacement" lithium batteries use a battery management system, or BMS, that works perfectly well with a standard multi-stage charger.

Before listening to folks who aren't up-to-date on current technology, go to information sources that specialize in that technology. Will Prowse, a young YouTuber, has a good section on all types of batteries on his website ( https://www.mobile-solarpower.com/li...batteries.html ).

As for pricing, be aware that because of Lithium iron phosphate (LiFePO4) chemistry you get nearly double the usable power of a Lead-Acid battery (including SLA and AGM) so essentially you need only half the battery (capacity). You should be able to get a 40ah LiFEPO4 drop-in (equivalent to an 80ah Lead-Acid battery) for around $400 BUT it will have a 4000-5000 duty cycle life (vs. 1000-1500 duty cycles with Lead-Acid) and charges from solar 40% faster as it absorbs a charge far more efficiently than Lead-Acid (as it doesn't require staged charging). Faster solar charging means less panels necessary.

It amazes me the amount of bad information out there on Lithium batteries and, BTW, deep cycle Lithiums batteries aren't the same chemistry as mobile phone batteries so they won't explode or burst into flames!

Quote:
Originally Posted by gordon2 View Post
AGM batteries will work fine with 99 percent of chargers designed for regular lead acid batteries. I got a Vmax Tank AGM and made no changes, using a CTEK charger, Progressive Dynamics converter and Bogart Engineering Solar Charger.

Lithium batteries are expensive and will likely require replacing all chargers.

SEE: Converting to Lithium

To me its simple. AGM.
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Old 07-17-2019, 08:15 PM   #11
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If your charger is a “multi” stage charger consisting of at least 3 stages, you should be good to go. I just upgraded to an AGM battery in my Casita but I had to replace the controller panel as it only had a 2 stage charger. AGM’s are essentially lead-acid technology, for which we have 100+ years experience. Lithium cells have a much greater power density as well as other advantages, but, as you found out they are much more expensive an have a couple of very nasty failure modes if not properly designed, installed or maintained (they can catch on fire!). I’m sure someone will disagree, but they don’t allow them to be shipped on an airplane for a reason.
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Old 07-17-2019, 09:10 PM   #12
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Quote:
Originally Posted by Losthwy View Post
Thanks for replies. It does seem lithium is a bit pricey.
Reason for possible change is old battery not holding power like it use to.
Replacing a standard Lead Acid battery with a new one is whole lot cheaper than replacing with something else and it works just as well.
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Old 07-18-2019, 07:06 AM   #13
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Quote:
Originally Posted by Techscott View Post
Most "drop-in replacement" lithium batteries use a battery management system, or BMS, that works perfectly well with a standard multi-stage charger.

Before listening to folks who aren't up-to-date on current technology, go to information sources that specialize in that technology. Will Prowse, a young YouTuber, has a good section on all types of batteries on his website ( https://www.mobile-solarpower.com/li...batteries.html )....
Will Prowse might be an expert for all I know, but I dont see any references to his training or education on his web site. I do this this:
William Prowse IV (www.mobile-solarpower.com) is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.

and I noticed that the page you linked to is mostly a list of these referral links helping him get paid. And you can buy his book too. Nothing wrong with a little capitalism of course.

But back to the statement that "lithium batteries [which] use a battery management system, or BMS, ... works perfectly well with a standard multi-stage charger."

My understanding (as a self-admitted amateur in this field) is that using a lithium battery with a standard RV converter or lead acid charger (multi stage included) will give you the advantage of the greater depth of discharge available with the lithium battery but you sacrifice the higher capacity of the lithium battery because for a full charge it requires higher voltage that the lead acid chargers will usually provide. So yes, it will work. But will it work "perfectly well" is subjective.

But since I am not an expert in the field, I will quote the manufacturer of what has to be the most common brand of converter / charger in RVs... Progressive Dynamics:

Can I Use My Present Progressive Dynamics PD9200, PD4000 or PD4500 Series Lead/Acid Units With the Charge Wizard to Charge My Lithium Battery?

Yes, if you are willing to live with an expensive battery that is only partially charged. The Normal Output voltage of the PD9200, PD4000 and PD4500 Series voltage provides only 13.6-volts and a full charge voltage for Lithium needs to be 14.4 – 14.6 Volts. The PD9200, PD4000 & PD4500 Series Charge Wizard will initially jump to 14.4-volts in the Boost Mode when first connected to 120 VAC power and will remain there until the battery voltage reaches 13.8-Volts, then automatically drops down to the Normal Mode of 13.6-Volts. The faster charge rate of Lithium means that in the Boost Mode it will reach this 13.8-Volt point after only a few minutes of recharging and then the charging current will drop to ZERO AMPS and will not add any additional charge to your Lithium Battery. This lower charge state will not damage your battery, but will eliminate most of the advantages you paid for.


Then there is the issue of the BMS design - some are very basic and some are quite advanced.

So for me, the bottom line is that it is not logical to use a lithium battery unless you also pair it to a charger specifically designed for it.
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Old 07-18-2019, 10:23 AM   #14
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I'm another vote for simply purchase a new lead acid battery. They are a lot of Amp hours per dollar and not a lot of dollars per year of use given good maintenance.

Maybe buy a battery minder to provide a maintenance charge during the off season. That can help the battery have a longer life span. Not to mention you have a charged battery to use during a power outage.

A good quality battery charger can make a difference, also don't forget many battery maintenance chargers can't charge a low battery, only maintain the charge of an already charged battery. The cheap maintenance chargers from Harbor Freight are a good example. They will probably die if hooked to a low or dead battery. Higher end devices will cover both charging and maintaining.

Keep the cells topped off to the bottom of the tube with distilled water, never tap or even bottled. Distilled only. Low water will reduce charge available and eventually deterioration of plates if the water gets low enough. That deterioration will permanently reduce the capacity if not provide a self draining short.

I too have only a couple of LED lights to run. I do have an inverter to power 110 volt items if needed but it isn't normally on so not much of a factor. If needed it can be turned on to charge camera battery, or laptop or maybe run a blow dryer "briefly" so dear wife can spruce up before going back out in civilization. Most power hungry thing I run normally is a small fan. I want to replace that with a 12 volt model to run directly from the battery instead of running the inverter because that is more efficient.
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