Isuzu NPS 300 camper build

[SkiFreak]

Hmmmm... did not assume 2 x 6v batteries. Good pick up.

 

[SkiFreak]

can't charge LifePO4 below 32F

As much as I do not have to deal with very low temperatures myself, I have my batteries inside the camper body.

 

[IGBT]

As much as I do not have to deal with very low temperatures myself, I have my batteries inside the camper body.

Yes, I didn't think Australia would see a lot of sub freezing or sub zero events

Utah might though.

I was considering putting a Lithium bank in the unheated garage pod on our vehicle, but the 0F limit on storage and 32F limit on charging is kind of a showstopper since we plan on extensive Alaskan travel.

I could try to rig up a heating blanket to keep the batteries warm, but we may leave the vehicle for weeks at a time if we do the Iron Dog on snow machines.

 

[david506th]

Technomadia.com has said they have seen degradation in their Lithium battery bank from heat as well. They keep theirs in the cargo hold under their bus. They do recommend them being in a controlled environment unlike AGM.

I would love to see a write up Owen on your site about your electrical plans. I use your site for reference all the time.

 

[GR8ADV]

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)?

500 ah's. Ok that is what I thought, just wanted to make sure.
.
Not sure if it applies to the Lithium discussion or not. I have a lithium battery in my Moto and the method of 'tender' charging of that unit, which may be similar to solar charging in concept, is considerably different than a regular battery. So the words of caution expressed in this thread should be considered.

 

[yabanja]

I have 8 3.2 v 100ah cells LifePO4. Still researching best setup. Leaning towards 200ah 12v. These will be the coach batteries and I am mounting them inside the cabin to keep them warm and cozy. My understanding is that they are stable to 20 degrees f. I haven't read anything about them being dangerous...


Sent from my iPhone using Tapatalk

 

[SkiFreak]

I have 8 3.2 v 100ah cells.

This raises an interesting issue that is not widely discussed, that being the resting voltage of LiFePO4 cells.

There are numerous companies out there that offer charging solutions for LiFePO4 batteries. Their sales pitch is normally that their product includes a "lithium charge profile", so it must be appropriate, right?
The resting voltage for my Winston cells is 3.6v, so can I use the same charging device as someone that has LiFePO4 cells with a resting voltage of 3.2v? I would argue that you cannot.
Basically... not all lithium batteries are created equal, so a "one size fits all" solution is a bit of a pipe dream.

Without hijacking this thread and making it all about LiFePO4 batteries, unless you intend on buying a complete "lithium system", of which there are some very nice, but expensive ones available, my recommendation (for what it's worth) would be to buy charging products that are user programmable. That way you can set the charging rate to something that is appropriate to the specific LiFePO4 cells you have.

Still researching best setup.

Having all of the cells in series is the simplest for monitoring the individual cells, which you need to do (via a BMS), but this setup may not be practical. Electric vehicles run numerous banks of batteries in a series/parallel setup, which is an accepted thing to do. You just have to decide on what output voltage suits your needs best, then wire the cells together accordingly.

 

[SkiFreak]

I would love to see a write up Owen on your site about your electrical plans. I use your site for reference all the time.

I have not updated my website content for some time now, as would be obvious to anyone that has visited my site recently.
Life gets in the way of some things, and my website has been a victim of this lately. Lots of half written articles that I need to finish, but it's finding the time that is the challenge.

 

[4x4coaster]

Thanks everyone for your input and questions, obviously solar & electrics is still a black art to many of us!

Here is another question;

There is not a lot of options out there for 24v solar panels so I will base my question around 12v panels to be used in a 24v setup, ie Isuzu wiring.

Let’s say my aim is to have 400watts of solar, so I purchase 4 x 100w 12v solar panels. I join 2 panels in series twice (4 panels) then join the 2 sets of series in parallel.
So now I have 2 sets of panels each producing 24v & 200watts joined together so that they still produce 24v but now I have my 400watts of solar input.
By using the advice to convert to watts instead of amps, is my calculation correct? Remember we are talking about the principle here not detailed specifics.


Thanks!

 

[chosen]

No trouble... it so awesome to be part of this community!

So you actually don't need to get exactly 24volt panels, it is all down to the regulator you make use of... so if you got the right regulator that is a MPPT 24 volt regulator, you can make use of good quality high voltage panels. The type many people make use of for their houses, only try for the thicker frames around them. You then could get say 48volt panels, and the MPPT regulator would convert most of the excess voltage (the voltage above the charging output required) into amps going into your batteries.

GSL make a resonable MPPT regulator that can cope with either 30 or 60 amps... other than that give Nimbus Engineering a call (in South Australia), Michael is very helpful and only sells the best quality gear.

 

[SkiFreak]

Chosen is correct that using a higher voltage panel is a better option.
As long as you have a good MPPT regulator that can handle the total open circuit voltage of the panels (Voc) then you will be all good. In fact, it is normally better to run higher voltages into your MPPT regulator, as this will give you the best efficiency as the light conditions change.

GSL make a resonable MPPT regulator that can cope with either 30 or 60 amps...

I disagree with this. The first MPPT regulator I bought was a GSL and it's charge profiles for lithium batteries was excessively high, in my opinion. I sent it back and replaced it with a Victron unit, which is user programmable. Victron make MPPT regulators for both 12v and 24v systems.

Also, as I mentioned above, a factor that needs to be taken into consideration is the maximum open circuit voltage that the regulator will allow, not just its maximum amp rating. The higher the maximum voltage, the more panels you can put in series. Just one word of caution here... check with your state laws as to the maximum allowable DC voltage allowed in a camper, without it having to be installed and certified by a licensed electrician. In Australia its about 60VDC.

 

[chosen]

Thanks everyone for your input and questions, obviously solar & electrics is still a black art to many of us!

Here is another question;

There is not a lot of options out there for 24v solar panels so I will base my question around 12v panels to be used in a 24v setup, ie Isuzu wiring.

Let’s say my aim is to have 400watts of solar, so I purchase 4 x 100w 12v solar panels. I join 2 panels in series twice (4 panels) then join the 2 sets of series in parallel.
So now I have 2 sets of panels each producing 24v & 200watts joined together so that they still produce 24v but now I have my 400watts of solar input.
By using the advice to convert to watts instead of amps, is my calculation correct? Remember we are talking about the principle here not detailed specifics.


Thanks!

Also, yes your calculation is correct... although 12 volt panels aren't 12 volt output, they are more like 18 or 14 depending on the panel. But you are spot on regarding the joining in series to double the volts and parallel to double the amps.

The only thing I would point out is that panels in series effect each other... in other words, should one of the two panels in series get a gigantic bird poop on it, or be under shade at a camping ground, this will dramatically effect the output of the panel it is joined with. This is not the case for panels joined in parallel.

 

[chosen]

Chosen is correct that using a higher voltage panel is a better option.
As long as you have a good MPPT regulator that can handle the total open circuit voltage of the panels (Voc) then you will be all good. In fact, it is normally better to run higher voltages into your MPPT regulator, as this will give you the best efficiency as the light conditions change.



I disagree with this. The first MPPT regulator I bought was a GSL and it's charge profiles for lithium batteries was excessively high, in my opinion. I sent it back and replaced it with a Victron unit, which is user programmable. Victron make MPPT regulators for both 12v and 24v systems.

Also, as I mentioned above, a factor that needs to be taken into consideration is the maximum open circuit voltage that the regulator will allow, not just its maximum amp rating. The higher the maximum voltage, the more panels you can put in series. Just one word of caution here... check with your state laws as to the maximum allowable DC voltage allowed in a camper, without it having to be installed and certified by a licensed electrician. In Australia its about 60VDC.

Some very good points about the maximum voltage as well as the amp rating.

GSL have two levels of their regulators, you are right that they would not have a good charging cycle for the lithium batteries, but their better quality units are also programmable. Their display unit can program the regulator also, but its display has accuracy problems and does not provide a true indication of the batteries voltage and is cannot be calibrated. I am aware that this has been brought to their attention in the past and they have not rectified this. Victron make very good quality gear! Their inverters are also top shelf!

I once had a GSL 2000 watt inverter that caught fire in my camper, luckily I was there to disconnect it from its supply voltage!!! I would not recommend their inverters ever due to this issue

 

[4x4coaster]

thanks again to all, and once again its back to the minefield.
So I find a unit that suits my 24v, mppt controller, dc charger, inverter, 240v management etc, then I look at 4 panels I think are good value and the total Voc exceeds the MPPT component, back to the drawing board!
This is so frustrating.

 

[chosen]

This is why I personally plan to keep it all 12 volts (after-all, there are more 12 volt items available anyway). There are issues with voltage drop and larger cables being required (as SkiFreak pointed out earlier)... but this is more for the high drawer items such as inverter and alike. Items like LED lights, etc. with very little current drawer aren't effected as much.

Stay 12 volts, get a 12 volt MPPT solar/booster/charger system, get larger solar panels if your roof size is large enough, such as 2 x 250 watt solar panels (or even more he he he) and join them in parallel.