[MI_Ghost]

AstroWill made this comment

Yes, but 3-4 100ah lead acid batteries = 150-200ah usable. 3-4 100ah lithium = 300-400ah usable.

That's why I was asking if that was usable amp hours.

Is it possible? Dual power supply for radio.

Downside could be leaving the radio on for a really long time and draining the house batteries. But in my case with plenty of batt. capacity and solar charging, it's unlikely to happen.. Better to drain the house battery instead of the starting battery :)

www.astrosafari.com

One of the biggest additions to camperize the van is going to be the house battery.
I was planning a bank of 3-4 100ah AGM batteries.
But Will's comment got me thinking (Yes, I know it is Dangerous! ).

Lithium is clearly a better battery technology but I have never heard of the difference in useable amp hours. Explain this to me please.

Is it really worth the 50% increase in cost to use Lithium vs AGM?
Would it be better to use just one 300ah lithium vs a 3-4 100ah bank?

 

[AstroWill]

But Will's comment got me thinking (Yes, I know it is Dangerous! ).

That Fing guy, I swear

 

[tungtide]

You can read on this subject until your eyes water. Lithium will outlast AGM and give you more usable AH. Because you can discharge them farther without damage. Roughly 600 cycles for AGM 2000 cycles lithium. They are much lighter as well. Most lithium batteries have built in protection so you can’t over draw them.On the down side look carefully at the charging requirements. I believe you need 14 volts to charge them. I have a problem with my marine batteries and my newer automatic charger. I fixed this by buying an old school charger from flea bay. Then I went to an onboard charger to really cure the problem. Space and weight are big concerns in our vans. I’m thinking one large lithium will be my end choice. All I will need is to find the money. As to the cost if you plan on keeping the van 10 plus years probably ok to invest the extra dollars

 

[AstroWill]

I have already written all my thoughts on that over here: Astro-Safari-Info - Batteries

 

[copperhead]

To add to Ken's points...IIRC, lithium's have a low temperature limit of 32 F for charging, with possible permanent damage if doing so. .I went with multiple AGMs. Besides the initial cost and charging limits, I also looked at having some redundancy if one battery would fail to be a plus. I'll definitely revisit lithium's when the need for replacements arise. Hopefully the costs will be lower and charging capabilities improved.

 

[AstroWill]

I have mine inside the van as there isn't the leaking/venting issues as with lead-acid batteries. A lot, maybe most come with battery management that won't allow them to charge if they are frozen. If you mount them outside, you can use cheap heating pads to warm the battery for charging in freezing temperatures, I think they were like $15 or so.

 

[MI_Ghost]

So the useable amp hour is the difference between a starting battery and a deep cycle (storage) battery.
50% useable capacity for starting battery.
100% useable capacity for deep cycle battery.

The AGM vs LiFePo4 is mostly a size, weight, and service life issue with LiFePo4 clearly being better.
Double to triple the service life for the 50% increase in cost.
Smaller size and lighter weight.

 

[AstroWill]

So the useable amp hour is the difference between a starting battery and a deep cycle (storage) battery.
50% useable capacity for starting battery.
100% useable capacity for deep cycle battery.

No, not at all.

 

[copperhead]

No, the AGM still only has 50% usable capacity., but unlike "wet" batteries it doesn't vent, so it's considered safe to mount them inside without worries of fumes. That and supposedly you can mount them on their side if you needed to. Don't believe the lithos need venting though either.

 

[AstroWill]

http://www.dekabatteries.com/assets/base/0139.pdf

Can VRLA batteries be installed in sealed battery boxes?
NO! Never install any type of battery in a completely sealed
container. Although most of the normal gasses (oxygen and hydro-
gen) produced in a VRLA battery will be recombined as described
above, and not escape, oxygen and hydrogen will escape from the
battery in an overcharge condition (as is typical of any type battery).
For safety’s sake, these potentially explosive gasses must be allowed
to vent to the atmosphere and must never be trapped in a sealed
battery box or tightly enclosed space!

But I don't think that our vans count as a tightly enclosed space

 

[MI_Ghost]

No, not at all.

Then by all means please define this useable amp hour.

 

[chrichardson]

Lead acid batteries are rated at a 20hr rate, meaning a 100AH rated battery will discharge 100AH at a rate of 5A for 20 hours. Exceeding a 50% depth of discharge(DOD) will shorten the life (rated in charge/dischare cycles to 100% DOD) of the battery, so manufacturers only recommend discharging to 50% DOD. In addition, the faster you discharge the battery, the less capacity you will get out of it. For example, when discharging at 30A, the battery will reach 50% DOD in 1 hour for a real world capacity of 30AH.

Lithium Iron Phosphate batteries are also rated at the 20 hour rate, but are rated for 100% DOD and are affected less by discharge rate. So the battery may be rated for 100AH, and it will deliver 100A +/- 5% at 5A. At 30A it may reach 100% DOD in 3 hours for a real world capacity of 90AH.

Then we get to weight. A 300AH lead acid battery weighs around 150 pounds, a 300AH Lithium Iron battery weighs around 70 pounds. To get a usable capacity of 300AH out of the lead acid to equal the lithium battery you would need at least 600AH, or 300lbs. So for your battery size you would be saving over 200 pounds by switching to lithium. Or you could drop the lithium battery bank to 150AH to save more weight/space, reduce upfront cost, and maintain the same capacity as 300AH worth of lead acid.

Lifecycle wise, a lead acid battery typically gets around 1000 cycles vs well over 2000 for lithium (some are rated over 4000 cycles). So at a minimum you'll need 4 lead acid 300AH batteries to equal the capacity and life of a lithium iron battery, and likely 8 if that 4000 cycles claim holds up. Lithium batteries are dropping in price pretty rapidly, and it already doesn't make sense cost-wise to buy lead acid house batteries. You can already get 300AH of lithium batteries for <$1000, 8 200AH lead acid batteries would be around $3000.

Lithium is a bit more difficult to charge, that and upfront cost are their only downsides.

 

[MI_Ghost]

Great Explanation, Thank You!

 

[AstroWill]

Lithium batteries are dropping in price pretty rapidly, and it already doesn't make sense cost-wise to buy lead acid house batteries.

100% agree. Another big thing for me is the fact that I don't have to worry about charging my lithium batteries to 100% every damn day. With lead-acid batteries I would have to make that long slow climb to 100% SOC or else they are going to be damaged quicker and have less capacity.

In addition, the faster you discharge the battery, the less capacity you will get out of it. For example, when discharging at 30A, the battery will reach 50% DOD in 1 hour for a real world capacity of 30AH.

For those that want to calculate this on your own: Peukert's law - Wikipedia or just use an online calculator.

 

[MI_Ghost]

Then let me ask this.
What would be a good size for the house battery 100ah, 200ah, 300ah, or 400ah?
I will be looking to use a 1000-1500 watt inverter
Refrigerator
Microwave
House lights (LED)
Audio / Video
Camp lights (LED)
ETC...

Aux Lights
Winch F&R

I am looking to support the system with
200-400 Watt Solar (200 roof mount, 200 Suitcase)
300 amp Alternator

There may possibly be a tag along trailer also

 

[Rod's Trucks]

The camp lights, audio (reasonable...not trying to power a car show system like Mmusicman ), refrigerator etc., are relatively small loads. A coffee pot or microwave is usually a large power load ( depending upon the size), but usually it is a short term use...maybe a few minutes at most, unless you are cooking a pot roast..
The winch is a somewhat different , but certainly a significant, issue.
Winching is often fairly long term, and a very high load at the same.
What is the rating on the winch ( both winching capacity, and the amperage it draws at full load-manual should indicate what to expect)?
Needed battery capacity will mostly be determined buy the expected winch use, and how long the pot roast takes to cook!
For the best luck with the winch, you will need short heavy cables, and excellent connections.
Note: the amp draw increases as the spool winds up more cable, because it has to work harder with a fatter drum diameter.
Others have significant winches ( I just have a baby one @3000 lbs, and it still might draw 100 amps near full load) .
Hopefully the more experienced others will check in.

I have been with Jeep guys who have fried alternators and cabling while trying to winch out a friend. Occasionally, give the winch motor a chance to cool off, and the batteries a chance to recharge a bit.
Rod J

 

[AstroWill]

I guess most would just be repeating what was already linked to, but I can add a few thoughts here. These things vary so much per person that there is no easy answer.

First because each battery type varies on the max amperage draw, have you decided on what type of battery you are going to be using? Be careful with those large amp alternators, a lot of times they barely put out at idle which can be a huge PITA.

What size microwave, how long are you going to be running it(cup of coffee or Thanksgiving turkey?), most usage in the morning/day/night, are you going to be running your alternator while the microwave is in use, or does the battery bank have to support it 100%? If you are only running it with the engine/alternator running, then it really doesn't matter and I would be wiring it up to run off of the alternator/starter battery. Same with the winches.

Fridge, what size, what model, how much amperage does it use on standby/running, what are the ambient temperatures, top opening or front opening, all of that is going to determine how long it runs, which in turn determines how much energy it's going to use. Fridge/heat/ventilation end up being the huge energy users because they tend to run, a lot.

Same with audio/video, are you going to be watching movies on a tablet with headphones, or do you want a 55" inside the slider, remote surround/sub so you can feel it while at camp? That is going to determine how it's powered and how much energy it's going to use.

Lighting, you want 1-2 room lights and a reading light, or you going to have 65' of multi colored rope lights encircling the van interior and another x feet outside, have some spot lights, how long are they going to be run? Again lots of variables.

Basically you need to find out YOUR usage for YOUR system under YOUR operating conditions and then do YOUR calculations.

Make a spreadsheet that has each item, how many watts it uses and how long it will be operating per day is the first step. Then you need to know how long you want to be able to run them without having sun/alternator charging your battery bank. Once you know all of the above, then you can match your charging system to the size of your battery bank.

Fun stuff eh

 

[MI_Ghost]

The winches will likely be 9K-12K front, 6K rear. I am thinking a separate battery system to help support that setup. Burying 44s in peat bogs you get a real good understanding how a winch taxes the charging system. Not for the faint hearted.

Microwave 0.7-0.9 cu ft used mostly for short term convenience use. Basically the same I use in the semi now.

Already have the AD244 300 amp alternator because of the good idle charging. Will be looking into a high idle system also. The fun part will be figuring out the control center to handle all of it.

 

[AstroWill]

Most of the time idle/cruising amperage suffers when you increase the peak amperage. That is why I was saying that. Have an output chart for the alternator you bought?

 

[MI_Ghost]

Have an output chart for the alternator you bought?

Not right off hand. 3 years and 2 laptops later I will have to chase it down again.