Electrodacus Design-Adding Alternator and Inverter/Charger
- Thread starter APhoton
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This sounds like a big inconvenience / problem. If the inverter and charger both disconnect when the battery pack reaches the high voltage cutoff, any AC loads will be disconnected, right? How big of a deal would this be for your use case?
Contacted Dacian, his answer-"Yes the grid will be disconnected and the 110V loads will be supplied by the battery through the inverter for a bit maybe around 3% SOC then the grid will be connected again so it will cycle in this way.
The only one that will properly work as an UPS is the Victron Multiplus 3000VA or 5000VA all other inverter/chargers where just not designed for a Lithium battery."
Since I never had a solar system, I don't know if this is a problem. How often will inverter/charger be turned on and off? Is that even an issue? I realize a lot of this has to do with amount of electricity being used. If it is nice and sunny out and PV are also charging batteries at same time, etc.
Best regards,
Dacian.
The only one that will properly work as an UPS is the Victron Multiplus 3000VA or 5000VA all other inverter/chargers where just not designed for a Lithium battery."
Since I never had a solar system, I don't know if this is a problem. How often will inverter/charger be turned on and off? Is that even an issue? I realize a lot of this has to do with amount of electricity being used. If it is nice and sunny out and PV are also charging batteries at same time, etc.
Best regards,
Dacian.
You have to have the DC negative connected to chassis ground somehow to prevent static buildup. The isolated DC-DC charger means you are able to do this chassis ground connection yourself in the manner you chose rather than depending on how this was done in the engine compartment. For a VAN like I am converting, either the isolated or alternator ground would work. But for a trailer that could be decoupled from the vehicle, you really need a dedicated negative to chassis ground connection located in the trailer which requires an isolated charger.
I don't see any reason to not use an isolated DC-DC charger, it will always work, you just need to add the DC negative to chassis ground connection yourself (which means you can do it right).
Adding the price of an AC charger, ATS and a Battery Protect (the SunPower Inverter will discharge your battery pack to 20V) makes the Multiplus option cost competitive. And for the same money you are getting a better quality inverter and charger. Once you design the entire system, the value of the Victron solution comes into focus. Plus if you become interested in monitoring your system or doing more complicated control logic (managing multiple charge sources), the Victron infrastructure does that better than anyone else.
I went through the exact same process you are. I ended up with the Multiplus.
Here is my wiring plan.
I am still in the middle of doing my RV van conversion so I am still putting it together.
I expect I will end up adding a Cerbo GX
Victron as much as possible. My design with help from fellow inmates here. I thought about the Electrodacus, but using magnetic contactor was not attractive hence the Daly BMS. The BMS is only really taking care of inbalanced cells in my system (and acting as a backup to the primary control system).
I am will be doing a residential system after the van is done, that could use the Electrodacus BMS. Still undecided.
I don't see a reason not to either (other than higher price), I just wanted to clarify that it will not be isolated if both systems (starting and house bank) are grounded to chassis.
That said, I'm not fully grasping the downside of the non-isolated version that you are trying to explain (for a vehicle/single chassis). Here are the simplified wiring diagrams for both (side by side):
I can't say I fully understand the non-isolated wiring, specifically what the horizontal black/negative at the bottom is (I would think chassis-ground, but than the chassis-ground symbol is coming off of that--maybe a common negative bus for both systems?)
I find the isolated wiring more 'intuitive' to me, and it offers more flexibility so I will probably choose that option personally, but it seems like the isolated and non-isolated versions would be functionally the same for a vehicle if you assume both sides of the isolated system are chassis-grounded.
And all this (the ATS, and additional components should be factored into the price comparison).
One option though--depending on your use case--that avoids an ATS if shorepower would just be an occasional nicety and not a heavily utilized power source is to design for 'shore charging' but not 'shore power.'
All AC power would be delivered by the Inverter, and a simple standalone AC charger would be utilized to recharge the batteries when shorepower is available, but would not directly feed the AC side of your system. There are disadvantages to this but also some advantages.
The point is specifically for a system installed in a trailer that uses alternator charging in addition to solar or shore power charging. In that case if you use a non-isolated DC-DC charger then you violate the single grounding point rule by grounding the negative terminal of the house battery any time the alternator charging from the tow vehicle is connected. If you use an isolated DC-DC charger then you can ground the house battery negative with or without the tow vehicle alternator being connected.
If you don't have this situation, then you don't need an isolated DC-DC charger. It certainly doesn't hurt anything to use an isolated DC-DC charger, but it is not required.
What is left out of the drawing you posted is that the alternator negative is connected to chassis ground inside the engine compartment by the vehicle manufacturer. If you intend to add a house battery ground connection then you should use an isolated DC-DC charger to avoid the potential of ground loops.
My is not a trailer and I have no plans to have a trailer. Mine is for a van conversion. For this reason, I believe isolated would be best option.
Thank you for taking the time to explain, this makes much more sense to me now.
They aren't my diagrams, I just screenshotted the diagrams in the Victron Manuals for each product. But I believe these modifications are what you are describing, correct? (dotted line = optional)
I'm still not 100% clear on the advantage of this. You would still have multiple points where DC negative and Chassis-ground are connected would you not? And because both sides of your system are bonded to chassis, there is no isolation, correct?
I apologize for my density, This is a concept I have not fully grasped yet.
I going one of three routes
1. Victron Multiplus
2. as you just suggested, 'shore charging'
or
3. Use shore power only for AC use in van and not for charging batteries. When I have shore power just let solar and alternator top off batteries
Victron would be the best. Not sure about what's best of other 2
Sorry, I noticed that after I made my post (and I corrected this in an edit). Your modified image is correct.
To make things more explicit, the DC system is not supposed to be isolated from chassis ground, but the negative to ground connection is only supposed to happen at a single point. What an isolated DC-DC charger does is split the engines 12V electrical system from the house DC electrical system so that each can be connected to chassis ground without creating multiple ground connections in the same system (a ground loop).
Modern car electronics do not use the chassis ground for a negative return. This causes rust and corrosion in the chassis and weird electrical behavior if the body is damaged and repaired after a collision (Bondo makes for a lousy electrical conductor). The reason why the DC negative is connected to chassis ground is to eliminate static build up on the wiring and electronic equipment and also so that if a wire gets shorted to the chassis it will blow the fuse. You really want to know when your wiring is shorting out.
This is exactly the same reason why AC neutral is connected to the green ground wire at the Circuit Breaker panel. It is a code and a safety violation to have more than one ground to neutral connection in AC electrical wiring. That is precisely one of the conditions that GCFI breakers are supposed to detect and protect you against.
-Edit (to make it clear I modified this post)
And the extra ground connection is not optional when using an isolated converter. You must have the "extra" ground connection since you are not connected to chassis ground by the alternator ground connection. Basically the isolated converter makes it look from a DC standpoint (as measured with an ohm meter) that the two systems are not connected to each other at all. This is generally a good thing to do.
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Got it backwards the trailer is where you really need isolation, but there is absolutely nothing wrong with using an isolated converter (that is what I am using in my Van).