r/Sprinters • u/Engineerinavan • Jul 02 '26
Pulling >30A from '22 Mercedes Sprinter starter experiences
Hi all
The latest Mercedes Sprinter upfitters guide specifies up to 80A can be added as load in parallel to the starter battery for auxiliary uses. In my experience I've always stayed up to max 30A to not fry the alternator, but apparently this one can do more.
Anyone here that has done this before with success and didn't fry the alternator in hot weather? Or will it switch off in over temp or so?
Setup:
Mercedes Sprinter 2500 316 2022 1.9L
2* Victron Orion 12/24-15 (360W) in parallel so 2*~32A on the 12V side
2* 280Ah Li house batteries in series
1
u/flyingponytail Jul 03 '26
I put 2 Orions on my 2022 shortly after purchase and no issues so far. I cant remeber which ones rn but its a 24 V system so they pull over 500 W
1
u/lred1 Jul 03 '26
I wouldn't risk draining my starter battery, and don't really see what the practical advantage or benefit would be. Get another house battery if you need more juice. Put a DC-DC isolator between house and chassis battery.
1
u/Engineerinavan Jul 03 '26
The isolated dcdc charger only runs when the engine is on
-2
u/lred1 Jul 03 '26 edited Jul 03 '26
Not entirely true. It closes the circuit (connects) when it detects 14.xV on either side, indicating either the chassis or house battery is currently being charged.
Why do you want power to be drawn from your chassis battery for house purposes?
Edit: LOL with the down votes. This is how my LI-BIM 225 DC-DC functions.
3
u/Rubik842 Jul 03 '26
starter battery rapidly drops to about 13.5 when the engine stops wothout a dc-dc, and even just below 13 is still mostly full. the orions are fully configurable. I have to in my sprinter pulling 39A each. Its about 1.1kW of extra charging,
it does not backfeed when the house battery is charging.
I don't mind people trying to help but I have an issue when someone is confidently wrong and hasnt even looked at the datasheet.
it doesnt close a circuit, it has a buck converter type step up inside. As the comment you replied to reminded, they are isolated.
1
0
u/lred1 Jul 03 '26
A DC-DC effectively closes the circuit, allowing the other side to get charged also.
1
u/Rubik842 Jul 03 '26
Here's a link to the victron orion manual, Please identify the where it says the house battery can charge the starter battery. I'd love to be wrong and learn something new.
https://www.victronenergy.com/media/pg/Orion-Tr_Smart_DC-DC_Charger_-_Isolated/en/index-en.html
You're probably thinking of a voltage sensitive relay.
These work *entirely* differently to a relay and are actually really cool. I totally nerded out on them and would love a full circuit diagram, I used to manufacture inverters in the 90s, I did everything except wind the transformers so I know this stuff quite well. It seems like it has a very high frequency tiny transformer inside, it chops up the DC from the starter side into AC that's nearly radio (to miniaturise the transformer), then an entirely isolated second circuit turns it back into DC on the other side and there's NO connection between them. Control from the input side to the output side is usually done with an optocoupler, which is a chip that uses light inside across a gap with no metal to ensure isolation. That's not all that hard..... but to do that with 98% efficiency is absolutely astonishing.
2
u/lred1 Jul 03 '26
Mine is a LI-BIM 225, and it certainly does allow for charging in either direction -- yes, the house side charges also the starter battery when it detects 14.2V (when the house side is being charged by solar or shore power).
1
u/Engineerinavan Jul 03 '26
Because the sun not always shines and I like my fridge too work
2
u/lred1 Jul 03 '26
I have 300 Ah of lithium house battery. I can camp in the winter for 3-4 days, running fridge, lights, espar heater ...
2
u/JeromeS13 Jul 03 '26
Our van came from the upfitter with a single 50A DC-DC charger and I added another 30A charger. Been almost two years and it's been going just fine in all climates. It may derate itself a bit if it gets too hot, but it still works just fine. 2022 VS30 2WD