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Old 12-22-2020, 11:04 AM   #1
Thorne's Avatar
Join Date: Sep 2020
Location: SF Bay Area
Posts: 42
SMB Sprinter electrics - what charges what?

I'm still quite confused about how the electrical system in my 2011 SMB Sprinter 2500 works. It was made at the Austin factory in 2012 and has only been slightly modified since (as far as I can tell). The solar panels, Zamp controller, and Tripp-Lite Inverter are all original.

I replaced the two old 65 Ah AGM house batteries with two new high-end Duracell Ultra Platinum AGM Deep Cycle Batteries, 105 Ah, Group 31M, wired in Parallel as the old batteries were. I had my auto-electrics guy (who doesn't know RV systems) install the shunt and head unit / remote of the Victron 712 Battery Monitor system, and that **seems** to be working as configured.

I set the Victron 712 to give a high voltage alarm at 14.3v, and it sent that alarm to me yesterday when the van was on shore power. The Zamp solar charger only gives me the option to have 14.4 or 14.7v as the max voltage, and even the lower rate (which I've selected) is higher than what most AGM batteries are supposed to be charged at when nearly full.

But I don't have any idea as to the basic path that the electricity takes, either from the two (presumably 100w) solar panels or the shore power plug. And I'm not sure what else might need to be replaced to keep from overcharging the new house batteries, and to give me a better picture of what voltage / amperage is going where.

I can try guessing, but really don't know how all this is supposed to work. Can anyone help?

Some guesses...

Layout 1 -
Shore Power goes into the Tripp-Lite Inverter, which then charges the house batteries.
Solar Power goes into the Zamp Solar Controller, which then charges the house batteries.

Layout 2 -
Shore Power AND Solar Power goes into the Zamp Solar Controller, which then charges the house batteries.

Layout 3 -
Shore Power directly charges the house batteries, and possibly Chassis battery.
Solar Power goes into the Zamp Solar Controller, which then charges the house batteries.


2011 Freightliner 2500 Sportsmobile RB110S, all electric, 150k
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Old 12-22-2020, 11:58 AM   #2
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Join Date: May 2007
Location: Beaverton, OR
Posts: 1,796
Option 1 would be correct. The shore power will run the Tripp-lite charger and charge the house battery. The Solar panels will provide power to the Zamp controller which will charge the house battery.

The starting battery being charged, depends on what solution you have, ACR, separator, or isolator. If it is bidirectional, it will charge the starting battery once the house battery gets high enough.

Your Tripp-lite will have an option for temperature compensation this usually taped onto the side of the battery. If you do have it the voltage setpoint will change based on the temp, lower than 77°F will cause the Tripp-lite to put out a higher voltage. The Zamp controller may or may not have temperature control.

And lastly, if your ACR/ Separator/isolator solution may provide a higher voltage when connected via the alternator.

feel free to PM if you like


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Old 12-22-2020, 08:59 PM   #3
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Join Date: Nov 2020
Posts: 8
!4.4 volts isn't that high for agm. I would leave it at that voltage especially if charging with solar. With solar its safe since the sun goes down and stops charging. I wouldn't leave it connected to shorepower 24/7 at 14.4 volts.
I had a kinitek high performance agm and always kept it at bulk 14.4v / and float 14.3v while connected to my 240 watt panel. I ran it that way for about 3 years with no problems. My oddessey agm requires 14.7 volts to fully charge. The duracell agms from what I saw on the web, just states not to charge at over 14.8 volts (thats the max), so 14.4 volts is safe for it.

What often kills an agm is undercharging or discharging too much and not recharging right away. Also some agms required a charge at high amps every once in a while.

I would definitely set the overvoltage alarm higher maybe 14.5 volts. I would want the battery to at least get to 14.4 volts. Also as the outside temperature decreases, the battery charge voltage has to be higher. Some chargers have temp sensors that will adjust output voltage as required.
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