Isuzu NPS 300 camper build

[4x4coaster]

Owen,
you are correct about the bad PR for LiFePO4, when I asked about them at Battery World, they replied, "do you want your motorhome to burn to the ground?"

I'm sure they will be the way of the future but a bit pricey for me now.
What length are your unisolar panels?



Shannon,
how are you managing solar? what setup & watts do you have?

 

[LeishaShannon]

Shannon,
how are you managing solar? what setup & watts do you have?

We use the Victron gear for solar too. The 70A model for the 1200W on the roof and the 15A model for the 400W of portable panels. Sticking with a single supplier you get some neat integration across the entire power system -

 

[fog cutter]

....I cleaned the insides of all the metal dust that tends to accumulate and painted the clean surface ....

that's thorough! following along; nice work.

 

[SkiFreak]

Owen,
you are correct about the bad PR for LiFePO4, when I asked about them at Battery World, they replied, "do you want your motorhome to burn to the ground?"

Yep, that is exactly the kind of crap I hear constantly. Isn't ignorance a wonderful thing?

What length are your unisolar panels?

I have PVL68 and PVL136 panels.
The PVL68 panels are 2849mm x 394mm and the PVL136 panels are 5486mm x 394mm.
The PVL136 panels are too long for my roof, but I know how to shorten them.

 

[4x4coaster]

That is a lot of solar for that amount of battery storage.

I found 2 different solar calculator sites and put through some figures, you are correct.
I would still go for 2x125 AH AGM's but could scale back to 400w and still have plenty of extra capacity.
One of the sites (not ebay, has a physical presence in Melbourne) has the flexible panels in 135w for about $330, so I would go for 3 of these to get 405w.

 

[SkiFreak]

Don't get me wrong... more solar is definitely better than less.
The biggest plus with having more solar is that you will replenish your battery usage much faster and on "less than perfect" days you should not really struggle to get back to fully charged.
My personal opinion on solar is to fit as much as you can, so my comment does not really reflect what I actually would do myself.
The catch cry of Tim Allen probably says it all... MORE POWER!!!

 

[4x4coaster]

I read in a solar post that when you join 2 125AH batteries together in a 24v configuration you still only have 125AH at your disposal.
So I guess the pay-off is that, for example, a fridge that runs on 12 or 24volts, may use 6 amps at 12v but only 3 at 24v so in effect, you have the same capacity at your disposal.
Is my understanding correct?

 

[chosen]

You do only have 125AH at your disposal at 24 volts, however the less amp drawer that you pointed out means that the joined batteries would last potentially 2 times longer in the example you have given... so your capacity is still double if you look at it that way. I find watts a good measurement to balance things out in your mind.

 

[SkiFreak]

In a 24v system with 125Ah of battery capacity you would have a total of 3000 watt hours at your disposal (amps x volts = watts). In my opinion it is far less confusing to think in watts when it comes to power usage.

Assuming that you can get the theoretical maximum capacity from your batteries (they are new and meet manufacturer specifications) and you only draw down to 50% SOC, then you would have 1500 watt hours of capacity at your disposal. I am also assuming that you can charge your AGM batteries to 100%, which is unlikely, but let's say that we can. In reality, you are more likely to get a usable 35-40% of the rated capacity of an AGM battery (1050-1200 watts).

With that information you can look at the specifications of your appliances (which are normally rated in watts, not amps) to work out if you have enough capacity for your needs.

 

[SkiFreak]

I might also add... a big plus of 24v vehicle systems is that you can run thinner wire (which saves on weight and cost), as the current draw for an appliance would be half that of a 12v system.

 

[yabanja]

I am reading all this with great interest as I have just purchased 200 ah of LifePO4 batteries for FIDO.

Allan

 

[GR8ADV]

I am reading all this with great interest as I have just purchased 200 ah of LifePO4 batteries for FIDO.

Allan

I am as well. Can someone school me. I have two 250 ah batteries tied together in my 12v system . How many ah do I have. Damn his sounds like a middle school math word problem.

 

[SkiFreak]

I am reading all this with great interest as I have just purchased 200 ah of LifePO4 batteries for FIDO.

Just remember... there are significant differences between AGM and LiFePO4 batteries.
LiFePO4 batteries are definitely not a drop in replacement for AGM batteries and it is a bit more difficult to setup a complete lithium charging system, but I think the hassle is definitely worth the effort.
Unfortunately, the market has still not really got on board with LiFePO4 batteries and there is a lot of misinformation being dished out about their safety. It is a pity, as I believe they are a far superior solution for an expedition camper.
At some point I should probably post how I have configured my 400Ah LiFePO4 system, but that's for another day...

 

[IGBT]

I am as well. Can someone school me. I have two 250 ah batteries tied together in my 12v system . How many ah do I have. Damn his sounds like a middle school math word problem.

Answer is D) Not enough information given

If you have two 6V batteries of 250AH tied together in series for a 12V system, you have a 12V 250AH system.

If you have two 12V 250AH batteries tied together in parallel for a 12V system, you have a 12V 500AH system.


For the LifePO4 guy, what cells did you end up going with and are you worried about temps below 32F in Utah in the winter (can't charge LifePO4 below 32F)?

 

[SkiFreak]

Can someone school me. I have two 250 ah batteries tied together in my 12v system . How many ah do I have.

I have to assume that you have the two batteries in parallel, which would mean that you have 500Ah @ 12v. The two batteries are connected minus to minus and positive to positive. For correct charging the negative on one battery should go to ground and the alternator positive cable should go to the positive on the other battery.
If you had them in series then you would be blowing stuff up, as you would be outputting 24v, not 12v.