24V LiFePO4 Schematic Review + Questions

[barbtalon]

Hello all,

I've mostly finished designing my camper van solar system and would appreciate some feedback. See the attached schematic and legend. This is my first build.

Any general feedback over any topic is welcome. I have a few specific questions as well:

1. Will the Epever 20A max controller work for my system or should I bump it up to 30A? Based on the data from Richsolar and my setup, it looks like the current could not exceed something like 18A on the output from the controller, but I'm not sure if panel voltage spikes on cold mornings would make it shoot up over 20A, or anything else. Just not super confident about that.

2. I haven't selected a shunt yet (component 3). Any tips on what to look for? I want one for accurate SOC measurement, as I've heard the Overkill BMS can be off. Not wanting to spring for the Victron SmartShunt.

3. I still haven't selected a battery charger (component 9). The Xijia inverter is not a charger, so if I want shore power, I'll need one of these. Can I use any random 120 AC input to 12V output charger? There are plenty of automotive ones for sale designed for AGM, and I wouldn't use one of those directly on my LiFePO4 bank, but since I have the Victron 12/24 in-between can I use any old charger? I'll seldom be hooked up to shore, so this component won't see much use.

4. I'm not sure about grounding protocols. Just ground anything with a metal case, correct? And what about AC grounding? Should I go with a GFCI or a standard outlet?

5. I haven't nailed down fuses, breakers, or wire sizes yet. Do I need a fuse between the MPPT and the busbar? Or one between the Victron 12/24 and the busbar? Any tips on fuses/breakers are appreciated.

Thanks for any and all responses.

 

[barbtalon]

Also, I haven't decided on the battery bank yet. I calculated my maximum daily power use to be 1800 W in the winter and 3000 W in the summer. I've been looking at the EnerAmp 170 Ah cells (currently sold out). Most cells out there seem to be 100 Ah or 200 Ah and not much in between, but it seems to me like the sweet spot for my system would be 150 Ah or so. Any thoughts on batteries would be helpful too.

 

[mikefitz]

Shunt and Overkill are incorrect. The BMS is part of the battery, connect the BMS to pack negative ( blue), BMS output (black) to shunt, shunt to negative/chassis.
the ' battery' with a 4 cell system

Shunt position,


Chassis ground and system negative should be connected together at some point.

Replace item 12 with a 'real' battery charger suitable for lithium.

Fuse/breaker in positive feed to solar controller at battery buss bar.

Using 9 as an input to the Orion is unusual but will work if the charger has an output voltage similar to the alternator voltage, check user instructions for voltage levels used by the Orion for voltage detection.

Item 11 and similar eBay/Amazon DC converters are not reliable, use a Victron DC to DC, or buy a good fire extinguisher suitable for electrical fires.

Item 4, the distributer, its not clear but these are intended to be used with Mega fuses so the positive feed to system parts are fused as near the power source as practical, the battery. You may need smaller value fuses, Blue seas Systems may have something suitable.
You need a 'master fuse' near the battery positive, class T ideal, MRBF fuse perhaps acceptable, search the forum for advice, this has been discussed.

Fuse values and cable gauges are nor shown so cannot comment. Incorrect fuse and/or fuse location together with incorrect sized cables are the usual cause of vehicle fires. Read up on requirements and post your best guess. The Resources section has lots of useful info.
Cable guide,



Useful info,

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You have some serious AC loads, Its doubtful a generic low cost eBay/Amazon inverter special can meet these requirements reliably or ever.

I do not know if there are safety regulations in your part of the world, but when a inverter is a permanent install with multiple appliances and cable routing in a vehicle, there is an increased risk of electrocution. For a safe installation the inverter must be a type that can be configured suitable, together with a protective device, GFCI, RCD, RCBO.

Mike