Please check my power center plan

johnny5

New Member
I've revised my power center plan and would like someone to take a look at it and make sure this all looks right. Sorry for the crappy drawing and handwriting.

Here's my main components:

100ah Lithium battery
1000w pure sine inverter
50a Renogy DC to DC charger
100a DC fuse panel
2 100W renogy compact solar panels

Mainly, I would like to know what breaker size to use in between the positive bus bar and the alternator (rated for 105a), the DC charger, and DC fuse panel. Thanks in advance for the help!
 

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HRTKD

Boondocker
The input from the alternator/battery to the DC-DC charger is going to exceed 50 amps. I would start by looking in the documentation for guidance on the fuse or circuit breaker size to use. My guess is that you'll need around 70 amps. That's a lot of amps, so make sure your cable and alternator can handle that much juice. There have been a number of forum members that started down the road of using a DC-DC charger rated for that many amps and realized that the distance involved required some very large cable.

Keep in mind that the Renogy device will do only 25 amps if both PV and alternator sources are active.

Your PV arrangement of 2p is OK, as long as the voltage doesn't exceed the 25 volt max PV input limit of the Renogy device.

My opinion is that you can find better equipment than the Renogy DC-DC/MPPT.

50 amp output requires a circuit breaker of 62.5 amps. Use the next highest rating you can find, probably 70 amps.

Fuse/circuit breaker for the DC fuse panel should be sized based on the max load you intend to use. 100 amp is likely way too high, probably closer to 40 amps, but that's a guess.

There should be a fuse between the switch and the battery. Probably 150 amps, but it depends on your loads. Class T is recommended. Expensive, but you don't have to worry about it.
 

johnny5

New Member
Thanks for your reply, Jim. I did have a look in my owners manual for the DC charger and it says 75a input, 65a output, So I figured I'd go with the next size up and chose 80 for the alternator input and 70 for the output to the lithium battery. I had a look at a wire calculator to size the wire for that run to the alternator and it looks like it's calling for 6ga, at 20ft. I don't know the exact distance yet, van is in the shop at the moment. Quick question, how would I know if my alternator can handle the 70 amps? I know mine is rated for 105 amps, but I don't know about it's "true" output.

Keep in mind that the Renogy device will do only 25 amps if both PV and alternator sources are active.
This is my first van build, so please forgive my ignorance here. The DC charger I have is rated for 50a... what does that mean, I can charge my lithium battery with 50 amps in an hour? And you're saying if both solar panels and alternator are charging the battery at the same time, I can only charge at 25 amps/hour total, or each? Just trying to wrap my head around these ratings and how to interpret them. I already have the Renogy DC charger, and fighting a tight deadline as it is. What would you recommend for the future?

I see the class T fuse, thanks for the recommendation, I'll pick one up.
 

time2roll

Photon Sorcerer
100 Ah seems small for a 1000 watt inverter. That can easily be a 1C discharge rate. Consider the common 280 Ah cells.

The 50a DC-DC seems large for the alternator and large for the battery. I think 20 amp would be a better fit.

The 20 amp MC4 fuses are not needed with two low voltage panels. Just skip it.

Your breakers/fuses seem mid wire. These should be close to the power source to protect the wire.
 

johnny5

New Member
100 Ah seems small for a 1000 watt inverter. That can easily be a 1C discharge rate. Consider the common 280 Ah cells.

The 50a DC-DC seems large for the alternator and large for the battery. I think 20 amp would be a better fit.

The 20 amp MC4 fuses are not needed with two low voltage panels. Just skip it.

Your breakers/fuses seem mid wire. These should be close to the power source to protect the wire.
Thanks for your reply. I actually bought two 100ah batteries, but realized my power needs are quite low, and not thinking it will be an issue with one. That's why I bought the 1000w inverter and DC charger. My thought was that I can always add a second battery later if I find I need it. I don't plan to live in the van, but out of it. I'll be gone doing stuff all day and will only use a few hours of juice at night. I'll be doing stuff like multi-day hikes, and will park it for a few days at a time. Biggest appliance is a 28L dometic fridge, and I believe the solar panels should be enough to keep that going. But you say the 50a DC charger is too big for the alternator, you mean it could put extra stress on it? Or just unnecessary/overkill?
 

time2roll

Photon Sorcerer
But you say the 50a DC charger is too big for the alternator, you mean it could put extra stress on it? Or just unnecessary/overkill?
Depends on alternator rating and other loads. Most vehicles with a trailer charging circuit are fused at 40 amps. Yes I also think it is larger than needed especially for light loads that mostly the solar will cover. Your call.
 

HRTKD

Boondocker
Thanks for your reply, Jim. I did have a look in my owners manual for the DC charger and it says 75a input, 65a output, So I figured I'd go with the next size up and chose 80 for the alternator input and 70 for the output to the lithium battery. I had a look at a wire calculator to size the wire for that run to the alternator and it looks like it's calling for 6ga, at 20ft. I don't know the exact distance yet, van is in the shop at the moment. Quick question, how would I know if my alternator can handle the 70 amps? I know mine is rated for 105 amps, but I don't know about it's "true" output.


This is my first van build, so please forgive my ignorance here. The DC charger I have is rated for 50a... what does that mean, I can charge my lithium battery with 50 amps in an hour? And you're saying if both solar panels and alternator are charging the battery at the same time, I can only charge at 25 amps/hour total, or each? Just trying to wrap my head around these ratings and how to interpret them. I already have the Renogy DC charger, and fighting a tight deadline as it is. What would you recommend for the future?

I see the class T fuse, thanks for the recommendation, I'll pick one up.

I wasn't clear on the Renogy 50 amp issue. If both solar and alternator are active, then each will contribute no more than 25 amps, even is the PV is producing a measly 5 watts. The net result is you won't get many output amps. On the other hand, if you're driving at night, you should get 50 amps of alternator charging.
 
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