[GaryBIS]

Hi,
A couple thoughts/questions on your diagram...

- I'm probably missing something, but I don't see how +12 volts gets to the fuse box? It seems like normally there would be a 12 volt wire going from the house battery terminal (or positive bus bar) to the fuse box. This line should be fused as close as possible to the house battery.

- The line going from the starter battery to the house battery (via the isolator) wants to have a fuse or breaker on both ends because it has current sources on both ends. If it does not have a fuse on each end, then if there is a short of this wire to the van chassis, then one the two current sources will be shorted to the chassis.

- I'd consider using a DC to DC charger instead of the isolator. It seems like when investing quite a bit of money in the Li batteries, that its probably worth spending the extra for the DC to DC to make sure the Li batteries get charged properely. I used the Kisae DC to DC charger, which also includes a solar charger in the same unit - but, looks like you might have the charge controller already.

- I'd get familiar with the BlueSea Circuit Wizard for wire sizing. It was developed by BlueSea and follows the ABYC marine electric code. Very easy to use and very safe, but not overly conservative. If you use it to size the inverter, the aprox current is (2000 watts) / (12.5 volts)(0.85 efficiency) = 190 amps - if you use the inverter at full power. When using the Circuit Wizard to size the inverter, fill in the Duration blank with how long you expect to use it at one time.

- The Fridge seems to be not connected to anything right now? It looks like where you have positioned it, you plan to run it off the inverter? Since it runs on 12V or 120VAC, I'd consider hooking it up to your 12V fuse box instead so that you don't have to run the inverter all the time to keep the fridge running - the inverter add inefficiency and uses power even when there is no load on it.

- A lot of people use this dual pole breaker to shut off the solar and provide overcurrent protection. There is technically an NEC rule that says you need to break both of the lines from the solar panels. Since solar panels are self limiting on current, they don't really need protection, but its very handy to use the breaker as a switch.

- Be careful that all wires that are leaving a current source (eg house battery or van battery) is protected by a fuse or breaker of the right size that is located as close as possible to the current source.

Gary

 

[GaryBIS]

Hi,
The max solar input voltage on the Kisae DMT 1250 is 50 volts, so it should be fine for your panel. This is the manual: https://www.kisaepower.com/wp-conte...nual_DMT12V_24V-Series_Rev-D_190612_Print.pdf

There are pros and cons to using the combo solar charger and DC to DC charger rather than separate units. I don't look at the Kisae so much as a combination of two units, but more as a gadget that can charge the house battery from two different sources. This saves some components and money and simplifies the wiring. On the other hand, if for some reason you have a need to upgrade the solar charger or the DC to DC alone, you are stuck with getting a whole new unit.

I hate to put even more stuff on your table, but we did just get through with redoing our van electrical system after 8 years of use and we tried to make it as efficient, safe and easy to build as we could. It might be worth a look through to see if there are parts of it you can use. Its documented in mind numbing detail here...
For example, one of the things we got rid of was that Progressive Dynamics fuse box and AC distribution center - our conclusion after 8 years of use was that its a much more complicated AC distribution system than we need or want.

Gary

 

[GaryBIS]

Hi,
I used a low wattage (12 watts) heater pad under each of my 2 LiFePo4 batteries. The heaters are low enough wattage that they don't need a temperature controller to regulate their temperature.
The two pads are on a switch which I turn on manually on those rare occasions when I need them.
The most common case is that its winter and cold and the van has been cold soaking out in the driveway for days and we want to leave on a trip. I turn the heaters on when we leave or the night before and it warms up the batteries. Once the batteries and van are warmed up, the heaters are not needed even if its really cold outside.


This is the temperature plot for heaters on..

The red is under the battery near the heater.
Blue is top of battery temp.
Green is outside ambient

Looking down into the battery compartment with the heater in place.
The heater pad has paper stuck to it from a previous experiement.
The black box is one of the two SOK batteries.

I have the SOK batteries - if I were buying them again, I'd buy the new models with built in heaters, as they don't cost much more.
Whether you need the heaters depends mostly on whether you want to be able to take winter trips in the van in cold climates - we do

Gary

 

[GaryBIS]

Hi,
This page has some common camper van loads and how many amp-hrs they use per day - and some info on tradeoffs on using electricity to power things vs fossil fuel.

Camper Van Electrical – Planning the System – Build A Green RV

www.buildagreenrv.com

I tested my fridge over 24 hours and it used 42 amp-hrs over 24 hrs - this seems to be reasonably close for the small 12 volt compressor fridges used in a lot of camper van.

Gary

 

[GaryBIS]

Hi,
I use the Kisae DMT 1250 DC to DC chager. It is a full capability DC to DC charger that uses multi stage charging and is very programmable to get the charge curve you want. It does this for charging from either the solar panels or the alternator.
I think its a good unit that is well designed and they have good customer support - how often do you get a 3 page letter from customer support explaining things in even more detail than my boring posts here

One little thing I like about it is that you can adjust its max charge rate down from the 50 amps. I have mine adjusted down to 40 amps, which is plenty for me and the lower max current makes life a bit easier for both the Kisae unit and the alternator.

If you are looking for a place to buy it, I used these guys and it was a good experience with a good price. I'm not associated with them in any way, but its nice to see a "Mom and Pop" company do a good job.

Gary

 

[GaryBIS]

I think the Kisae 1250 is a decent DC2DC charger ,,, It will get you 775W @ 50 amps from the alternator 👍

If you did connect your solar panels to it you can get a max of 600W but they also show 500W (input ,,, so there might be a slight loss of output) ,,, so there is that ,,, for a van - PV Array 14.5 to 50 Vdc & 30 amps is also pretty decent. That allows a good combination/ selection & that can be very helpful in roof layout configurations to have options.

View attachment 94617

I would not hesitate to use it as a dual “alternator / solar” providing there is a system to turn off the solar panels & the system allows that ( PV input breaker switch maybe - the type used in panel combiner boxes ).

Maybe @GaryBIS would know if utilizing as a dual “alternator / solar” is flawless or if it has limitations?

Hi RV,
I normally leave the Kisae hooked up to both alternator charging and solar charging, and let it decide which it wants to use. As far as I know, it can only use one at a time. I believe that it prioritizes the alternator if the van is running, but if I want it to use solar, I can just turn off the disconnect switch on the alternator charging and it will switch to solar.
Not sure if this answers the question?

Gary

 

[GaryBIS]

Hi,
It would be good to post an updated wiring diagram.

Gary

 

[GaryBIS]

Hi,
Nice diagram.

A couple thoughts...

- It seems like you will want a switch on the hot water heater so you can disable - but, maybe it already has one.

- This is an unimportant thing, but you show 49 amps in the line from alternator into the Kisae DC to DC. If you set the DC to DC at its max of 50 amps, the input to it will be somewhat more than this due to the inefficiency of the DC to DC - maybe a bit over 60 amps?

- I'd be tempted to up the 40 amp fuse and wire to 60 or amps. With the 40 amp setup you are limiting your total at one time 12 volt DC load to 40 amps, and 12 volt loads tend to accumulate over time.

- OK, here is a thought for you and @dog_house on how to hook the house battery to the system. Hook the two positve terminals of the house battery together with a heavy cable. Put one of the MRBF fuse holders on the plus terminal of each of two house batteries. The wire out of one of MRBFs feeds the inverter directly using as short a wire as possible that goes direct to the inverter (possibly via a switch if the inverter does not already have one).
The wire out of the other MRBF goes to the plus bus bar and uses only as large a fuse and wire as is required for the loads off the DC bus bar. In your case, you have so few lines off the bus bar that you might just eliminate it. You can hook more that one wire up to the MRBF fuse holder.
It looks like you can get MRBF fuses up to 300 amps, which should be plenty for your inverter charger?

- One thing to bear in mind is that all wires coming into and out of the plus bus bar need to be fused for their wire size. You show the fuse in the one going to the DC distribution center - it should be located as close as possible to the busbar.
The wire from the bus bar to the DC to DC should also be fused as close to the bus bar as possible. You want these fuses to protect against an accidental short of the wire to the chassis (eg something dropped on it, or abraded away over time, or a terminal ripped off) - the fuse should be as close to the current source as possible. In this case the current source is the house battery via the bus bar.

Gary

 

[GaryBIS]

I like @GaryBIS idea of short parallel battery wires ,,, but I’m still using a double Blue Sea; 300 amps to the inverter if it calls up that big & a fuse sized to the 12vdc panel (If the purist in balances ng the batteries matter I suppose 2 short wires to a double Blue Sea would be good also).

I have used the “load side” of the BM712 shunt as a negative bus if I only need to attach 2 or 3 ring connectors ( caveat is - no inverter on my systems so YMMV - I am usually in the single digits of amps unless charging). Regardless - You can install a negative bus “a copper bar” with bolts etc that bolts on the “load side” of those shunts. Where all the black wires go in my schematic above.

Hi,
I think they "only" want a single 300 amp fuse/breaker...

From the manual...
Page 6

Fuse or Circuit Breaker:
• DC-rated fuse or DC-rated circuit breaker connected along the DC positive line is required.
• For IC121040 select a fuse or circuit breaker with a minimum of 150 Adc
• For IC122055, select a fuse or circuit breaker with a minimum of 300 Adc
• Based on the size of your 12V Battery Bank, determine the overall short circuit current rating of
the battery bank from the battery manufacturer. The fuse or circuit breaker chosen has to be
able to withstand the

Assuming that its the right manual.


I think that @dog_house suggested that a good way to do with would be to have a 150 amp MRBF terminal fuse off each battery to add up to 300 amps. I agree, but I think in this case it might be bettesimplier to use a 300 amp direct to inverter (or not ) , and a 2nd smaller fuse to the rest of the DC connections?

I like the double MRBF off one of the battery terminals to make all of the connections without the need for a busbar.

Gary

 

[GaryBIS]

30amps

I think thats the rating of the AC side - RV is asking about the DC side.

 

[GaryBIS]

Hi,

Here is a quick sketch of another wiring diagram.

I've not looked at what has been posted since the last one diagram, so I don't know what might have been brought up.

Edit: the unlabeled 2 batteries in the upper left are your two 100AH house batteries.

The main change is that at the house battery, it uses one dual fuse MRBF fuse holder. One fuse is a 300 amp fuse that serves the innverter charger, and the other is an 80 amp (could be 60 amp) fuse that serves the DC fuse panel (PD5000) and the DC to DC charger (DMT-1250). You could technically say that having a 300 amp plus and 80 amp excceeds the 300 amp rating of the fuse holder, but given that the inverter is never going to pull 300 amps, I feel comfortable with sayig the 300 amps total rating is not going to be exceeded.

I show a switch in the inverter line, which could be optional if the inverter has an easy to access on/off swithc, but most people seem to be more comfortable with a separate switch. This switch should technically be rated for 300 amps since its on a 300 amp fuse, even though the inverters is not going to pull that much.

I show a switch on the line from the van battery to the DC to DC - this is so that you have an easy way to turn off charging from the alternator. I use this a lot on my van when I want to charge from solar while driving.
You also need a fuse on the line from the van battery to the DC to DC and it should be as close as possbile to the van battery terminal.

No busbars as you would have so few connections to them. The ABYC marine code allows up to four lugs to be connected to one terminal.

The #8 wire shown on the PD5000 and DC to DC connection is good for the 80 amps up to 3 ft wire length with less than 3% voltage drop. For more than 3 ft, you would have to go up to #6, or drop the fuse to 60 amps. An interesting thing on the 80 amp fuse is that if the 12 volt DC loads are pulling (say) 40 amps and the DC to DC is charging at 40 amps, the fuse is seeing zero amps.

Gauge 2-0 (00) is good for 3% drop and 300 amps up to 3 ft, but, you will never see 300 amps with that 2000 watt inverter.

I had the PD5000 in my last electrical system before I redid the system. It works fine and while I could not find an actual rating for the DC section of it, its a lot more than 30 amps. I guess you could email them. On my van the DC input to the PD5000 was on a 60 amp fuse.

I like simple, and I have to say that the thing that appeals to me about this scheme is that its about the simplest van electrical system I have seen

Anyway, food for thought.

Gary

 

[GaryBIS]

Now with less fuses and more wires. Thanks @MaggieMarty I updated the drawing.

@GaryBIS I think this matches what you have aside from the ON/OFF switch MRBF being added. Really it’s just moved to make the wiring easier. You could swap the pair of 150's for a single 300 on the POS terminal of the battery if you don't want the protection for the first battery. It behaves the same electrically but I don't like unprotected lithium batteries in parallel.

View attachment 94673

Hi,
That's looking good to me.

The only comments...
- I have a breaker in the PV panel input line so I can shut off solar charging, and a switch in the line from alternator to the DC to DC so I can shut off alternator charging. I find I use these quite a bit. For example, when the van is sitting in the driveway between trips I don't want the solar charging up the house battery - that was fine with lead acid, but LFPs live longer if kept at part charge when resting between trips. There have bee other times when driving when I know the batteries will charge up with just solar, so might as well save the gasoline that runs the alternator.

- Not sure if the diagram shows a fuse where the wire leaves the van battery to go to the DC to DC charger, but there should be one there to protect against shorts to the chassis along this wire.

- I'm still doubtful about separate 150 amp fuses on each battery.
Its seems very uncommon to do, adds extra connections and components with their own failure possibilities, adds fuse and connection resistance which can vary for connection to connection and fuse to fuse in each battery circuit where you really want the resistance the same so the batteries share the load equally.
What kind of failures is having separate fuses protecting against, and is it worth the negatives?
Maybe our contingent of local electrical experts could comment - @HarryN @Baxsie @larry barello @RV8R @dog_house @diytech @SteveSS @Winston @jracca No doubt leaving some out, but you know who you are.
It would be nice if we could agree on some common advice.

Gary

 

[GaryBIS]

Looks OK, but I'm not seeing how 12 volts is getting from your house battery to your DC distribution center?

Gary