Underseat Sprinter electronics & three battery connection 

Thank you. Glad it was helpful.

You're welcome.

Thank you! More to come on my whole electrical system and house batteries,

Hopefully some helpful info. Ask you questions and I'll try to answer them.

Congrats to your daughter and her van. The factory batteries are AGM (or at least were). Absorbed Glass Mat uses lead acid for its electrolyte, but has a spiral wrap construction that makes them hold up better to vibrations and temperature extremes than a typical flooded lead acid vehicle battery.

Thank you! I do have a more detailed video in the works of my electrical system. Subscribe and should be out soon. In the meantime, here is a little bit about the electrical system: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-z5C-QNcuuSw.html

Here is one on the cabin: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-zkTcBIAxn9w.html

And another on the cabin: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-grVsBo3edO4.html

Check out Blue Sea Systems battery switches. They have great manual and remotely operated battery switches which make it easy to switch between or to combine battery systems. These are mostly for manual control. If you want to have it be automatic once the alternator voltage comes up, check out their automatic charging relays. Many vans use them and they work great. As for your alternator, it will only put out what it can and has a lot of extra capacity for charging house batteries, and your 2019 van's factory alternator monitors temperature amongst other things helping ensure its reliability, so I wouldn't worry about damaging it so long as it's wired safely.

Good question. I charge my house batteries, battery system number 3, via the factory Aux battery relay, so when it connects soon as the engine is running, it connects the factory Aux and my house batteries. My house batteries are over 4x the capacity of the Aux battery but each times four batteries can take about 2-3x the charge rate of the AGM since they are lithium which has far higher charge and discharge rates since much lower internal resistance. So the load on the factory alternator will be far higher than the just the Aux battery, and I noticed that the engine voltage would drop and come back up within the first 30 seconds of the engine running, and that delayed start allowed the "start up" load of fuel heaters, cabin resistance heaters, pumps, glow plugs and all of the other high loads at engine start up to settle and voltage to stabilize before I add that significant load of the potential 100+ amps of charging current going to the house batteries, and additional to the AGM Aux battery at the same time as engine is warming up and start up voltage stabilizing. I found this delay alleviated the voltage dips right after engine start up. AGM batteries like the factory Aux battery can only take a modest charge of about 20-30 amps like all lead-acid batteries, while each of the house lithium batteries can take a charge rate of up to 100 amps, and with four of them, my cabling limited it to about 120 amps total, and the factory alternator and its relay to 150 amps. At start up, current for the engine and its systems can be over 120 amps, so that maxes out the most the alternator can do at peak, yet at idle it's about half that which is less than the load of engine start up and AGM and House battery charging, so hopefully this explains why the voltage drop. MB changed the Aux battery electrics and alternator in ~2018-2019, and it sounds like your van is different than mine, so you may not be experiencing this voltage drop or not have a house battery system with the capability to accept as much of a charge as mine did, so my approach helped to preserve voltage stability while your system may not need this. It may not had been needed, but certainly helped to keep electrical systems getting a more stable voltage within acceptable range instead of the >2 volt sags I saw.

It's the excessive draw on the alternator he's preventing not flood (load) on the auxiliary battery.

I believe it's the Blue Sea's 6000 series, which is rated to 300 continuous amps and 900 cranking amps for up to 30 seconds. Much more than the Sprinter's system capability and the factory charging to house battery connection rated and limited by fuse to 150 amps. A great little switch. I'll put a link to it below.

Here is the one I am using: www.bluesea.com/products/6007200/m-Series_Mini_Selector_Battery_Switch_-_Black and purchasable here: amzn.to/3RQ0YP6

@@vantripping Thanks, my thoughts were the same but wanted to confirm. On another aspect of that electronic set you have under the seat base. The terminal fuse base off the aux battery. You have a 100A MRFB terminal fuse I believe going to power a ST fuse block which powers your outside off road lights which is switched off the weather deck. In that cabin upgrade video you verbally mention a relay. I believe you said a 100A relay. Where in the schematic did you place that relay and why?

I ordered my van with the factory auxiliary battery, which has a dedicated 150 amp fuse from the power bar connected to the starter battery, and brings that to the auxiliary power connection under the driver seat. I then use a MRBF to connect power from the aux connection to my house battery switch, and onto my house power system and main fuse panel. You could do what you want by using a relay or switch to connect power between the two batteries, just as my manual battery switch allows me to interconnect the house, aux and/or starter batteries in any way manually as needed. The factory ax relay does that connection and disconnection automatically as any relay could as well. Why I use a relay with timed delay to connect the starter & aux batteries to my house battery to allow them to come up to voltage before I add in the house battery to be charged.

@@vantripping Thanks for this much appreciated, I am interested in the cable which you have labeled "Starter" that goes back to the starter battery from your three-way switch under the seat. This joins the aux and starter if you install one, and in your case, the house setupback too. I realize that the aux batt relay feed picks up off the PDC(Power Bar) with the 150A fuse. Does the cable I mention above go back to the starter battery to bridge them also get mounted at the PDC - Power bar, as I have an extra slot left on my PDC. Was wondering what you did there, whether you mounted the return on to the Power bar also or onto the actual battery positive post. Hope that makes sense! Thanks for the speedy reply.

@@alitheiaziton5188 Great question and notice. Yes, that cable from the disconnect switch goes back to the starter battery power bar, and has it's own dedicated fuse. I have never used this but would be able to be used to provide current from the house and/or aux batteries to the starter battery, to provide a charge to it to help it start the engine. If you do this, I would recommend that you use this feature to charge the starter battery for at least a few minutes before trying to start the engine so that the all of the starting current is not going thru this connection all at once but instead over a few minutes of charging current to get the starter battery voltage up. The switch is plenty good for it, but the cable, connections or fuse at the PDC may not be rated for full starting current but good for a 100 amp charge/connection.

@@vantripping Great answer, I am claculating that as the feed for aux battery is 150 amp the return can also be that of the same rating if mounting on the PDC. Naturally as mine is the MB bulletin retofit that recommends 35mm - 2 AWG cable, I can complete the system with the same, feed and return both at 150A. My Sprinter has a 180 amp alternator as opposed to some others that carry the 220A. I am assuming your setup regarding your cab starter and auxillary battery has the same 150A feed to Aux and 150A upon re-entering the PDC to join to the starter battery. Cant imagine when, if, the alternator would ever exceed 150amps, any input on this is welcome as this is not my area of experience. Hey thanks for the info here, thumbs up from across the pond..

@@alitheiaziton5188 My van has the 200 amp alternator and the full 150 amp feed from PDC to Aux battery connection point, and the most output I ever have seen from the alternator to my house batteries is around 90 amps for a few seconds and quickly tapers down to 80 something amps, and within a few mins down to about 60 before continuing to slowly lower over an hour to about 40 and then another hour or two to 10 or less. I have 400 amp-hours of lithium capable of charging/discharging at 400, and a cable and rest of electrical sized to support the full 150 amps of charge to House batteries. So while the alternator can put out more as seen from other high-amp electrical factory components operating just fine during high charge to house battery periods, I think the lithium house batteries limits charge-rate is greatly less and I doubt anyone will see more than 100 amps output from the PDC/aux battery connection.

The rely I used is a simple 200amp relay, which are fairly easy to come by and fairly low cost. As for the timer board, I purchased it on Amazon for about $10. Just look for a programable timer relay. Let me know if you want me to provide links to these.

Here is a link to the programable timer relay I used: www.amazon.com/gp/product/B07BT25J52/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

@@vantripping Thanks for the information. Much appreciated!

@@devinderkhroad388 You're welcome. Glad it was helpful.

1. One more question, around 4:15-4:30 mark you mentioned you have protection to avoid overloading the alternator. I am assuming your are referring to the programmable timer relay. How do you address the prevention of excessive draw to the house batteries if the house batteries are severely depleted, because that condition would still exist after a couple of minutes as well. 2. I noticed you are tapping into power at the factory relay connection instead of using aux battery fuse box . If I just want to tap auxiliary battery via a relay to charge my house Lithium batteries instead of combining all thee batteries, connecting my relay via an empty/available slot in F150 fuse box with 150A mega fuse should be okay, right?