Trickle Charger for Sprinter Batteries

lkoolkin

New member
I use a Noco Genius 750, <$30 on Amazon. Since coach is plugged in when stored, this simply plugs into the 110v outlet behind the driver's seat. It comes with all cabling and connectors necessary to wire to the battery, bring cable end with connector up under the driver seat, then plug the charger in and it's cable into the connector.

It's a smart charger, colored led shows status, and no more low chassis battery even months later.
 

israndy

2007 LTV Serenity
It would seem that if you have a starting battery that has lots of missing charge, or is OLD AS F, it would take watts away from your house battery if there isn't some limiting factor. So your batteries would charge with less than ideal voltage. Especially for things like Equalize charging. Using the Trik-L-Start lets the house batteries charge in the best possible mode. When the charger is trying to sense the state of the batteries to figure out what mode to go into next it isn't affected by the state of the chassis battery, it cannot sense it at all. It only knows what the house batteries are up to. Then a little extra power trickles into the chassis battery and tries to keep that charged too. I have solar so there is usually power and I give the house batteries the best charge they can get this way including the monthly Equalization charge. My chassis battery is original but still keeps ticking so I have yet to replace it (only 12 years old, well I got the RV in 2011, perhaps it's been replaced).

-Randy
 

ablock

Member
Using the Trik-L-Start lets the house batteries charge in the best possible mode.

Randy, I'm not sure what you mean by "best possible mode"? Are you saying that using a dual-sensing battery combiner would do something less desirable in the case of a depleted chassis battery (or any other case)?

Perhaps you are saying that the current limiting feature of the Trik-L-Start is an advantage in the case where you have a depleted chassis battery because it still allows the (for example) solar charger to put most of the current into the house battery — the house battery will not "lose" excess current to the chassis battery.

I guess in the case where you have two depleted battery banks this could be an issue, and then you get into the question of what is more important: being able to start the engine or run house loads. As a practical matter it's not something that worries me, as the chassis battery should only lose a fraction of an amp-hour per day from self-discharge and parasitic loads, loss which would be easily topped up by the solar panels — perhaps the solar controller has to run in bulk charge mode for an extra minute or something.

Does that sound right?
 

israndy

2007 LTV Serenity
If left alone the chassis battery will never need bulk charging. Maybe if you leave the headlights on. It is used to start the vehicle and then it begins to charge.

So your car battery is sitting at 12.9 volts, almost full

Your house battery is depleted at 11.9 volts, ready for a full charge

If a 3 or 4 stage charger is let loose it will sense the voltage on the house batteries and decide what stage to put the charger into. At this point it will be bulk. So all the current all the time, floodgates are open. Unless you have a battery monitor it cannot know how many amps need to go back into the battery so it has to test the voltage and see. Now combine the two battery packs. It sees there is 12.9 volts out there so it doesn't charge quickly, it goes into a slower charge mode and the batteries take days to charge. Or worse, the house packs start charging from the starter battery and drop it's voltage, so the charger reads that, and goes full bore. But the starter battery already is full. This high level of charge will boil away the chassis battery while the house batts are lapping it up. This arrangement will age the batteries quickly.

So we use a Trik-L-Start, or if you think you need it, an Amp-L-Start, say you have two starter batteries and 500 AmpHours in your house battery pack. Now I am not saying RV designers always are smart about charging. Until just a few years ago, they didn't even use multi-stage charging. Just used a relay that tripped when there was charge level voltage out there so everyone charged the same and isolated while the batteries were in use so you didn't kill the starter battery with your furnace overnight. And LOTS of RV batteries were replaced all the time. Batteries can be expensive, and we are learning to take care of this.

Now we are heading into the era of BMS monitored Lithium batts. This will be a whole new world.

-Randy
 

Well, I think it's nicer to permanently hook up a trickle charger like the Trik-L-Start or Amp-L-Start out of sight between the chassis and house battery rather than having to open up the house battery compartment and hook up this battery tender between your house batteries and the cigarette lighter every time, but to each his or her own....

(On first read, I thought you were suggesting hooking up the chassis battery to trickle charge off itself through the cigarette lighter... my bad!! ;-)
 

ablock

Member
I'm not worried about boiling the chassis batteries with the solar controller or multi. Max lithium (i.e., house bank) charge voltage is 14.2 with a very short absorption time.
 

Eugene Rider

2016 Unity TB
(On first read, I thought you were suggesting hooking up the chassis battery to trickle charge off itself through the cigarette lighter... my bad!! ;-)[/QUOTE]

I have the RV heaters in my Unity during the cold weather when storing so it's real easy to use the cigar plug.
 

Suza

Member
Well, I think it's nicer to permanently hook up a trickle charger like the Trik-L-Start or Amp-L-Start out of sight between the chassis and house battery rather than having to open up the house battery compartment and hook up this battery tender between your house batteries and the cigarette lighter every time, but to each his or her own....

(On first read, I thought you were suggesting hooking up the chassis battery to trickle charge off itself through the cigarette lighter... my bad!! ;-)

I interpreted Eugene Rider's suggestion as connecting the Battery Tender to the battery via the cigarette lighter plug and powered through the 110v plug while the coach is plugged in to shore power.

Is this not correct? :idunno:
 

Suza

Member

This is the set up I am looking for, I think :idunno: Tell me if this is correct:

With the coach hooked up to shore power, the Battery Tender is connected to the battery by way of the cigarette plug using the adapter (I did not realize there was an adapter) and to power via the 110v plug (located behind the driver's seat in our TB). Is the Battery Tender cable plenty long to reach from the electrical plug to the cigarette plug?

One thing puzzles me (understand, I don't know a lot about DC power): The cigarette plug can be used to draw 12v power from the chassis battery, but it also be used in reverse, to supply power to the battery? Seems like this is what is happening.

Eugene Rider: Have you used this set up and if so, how is it working? I have seen other posts from those who say they have no problem with the chassis battery draining during storage. We have had our Unity sit idle for 1-2 months with no problem starting the engine. But then, I suppose the Battery Tender would increase the life of the battery. Is this correct?
 

ablock

Member
The cigarette plug can be used to draw 12v power from the chassis battery, but it also be used in reverse, to supply power to the battery?

Yes, though there is probably a relatively low-amperage fuse on the cigarette lighter wire that limits how much charging you could do via that route.

:thinking:

Well, I just looked it up and it looks like the cigarette lighter outlets are actually fused at 15 or 20A, which is larger than I expected. Certainly enough for a trickle charger, in any case.
 

aarpskier

2017 LTV Unity FX
Well, I just looked it up and it looks like the cigarette lighter outlets are actually fused at 15 or 20A, which is larger than I expected. Certainly enough for a trickle charger, in any case.

I don't want to hi-jack this thread, but where did you look it up? The diagrams in the "fuse supplement" booklet that came with my 2016 chassis don't match the fuse box under the left side of the dash. For example, the booklet says fuse #13 is a 15 amp fuse for the ashtray light, cigarette lighter, radio and glove box light. It is in fact a 15 amp fuse, but has nothing to do with that circuit. And, the diagram lists fuse locations 1-25, but the actual fuse box has fuse locations 1-24. :idunno:
 

alichty

2014 LTV Unity TB
I don't want to hi-jack this thread, but where did you look it up? The diagrams in the "fuse supplement" booklet that came with my 2016 chassis don't match the fuse box under the left side of the dash. For example, the booklet says fuse #13 is a 15 amp fuse for the ashtray light, cigarette lighter, radio and glove box light. It is in fact a 15 amp fuse, but has nothing to do with that circuit. And, the diagram lists fuse locations 1-25, but the actual fuse box has fuse locations 1-24. :idunno:

According to the MB manual for my 2014 the 12V socket is rated at 25A. In my Operator's Manual it is shown on page 238 although your model year manual may vary for the precise page. That page also lists the other 12V sockets and their respective amperage. The front one in the center console is the heavy hitter.
 

aarpskier

2017 LTV Unity FX
Thanks, Alan, but my issue is how to identify what the fuse controls in each location in the physical fuse box. I can't do that with the 2016 manual, or its "fuse allocation supplement" pamphlet, because the location diagrams do not match the physical boxes. A Google search turned up a similar problem with 2013 Sprinters, but that was not any help. I will have to contact the local Sprinter chassis service location for help.
 

Suza

Member
According to the MB manual for my 2014 the 12V socket is rated at 25A. In my Operator's Manual it is shown on page 238 although your model year manual may vary for the precise page. That page also lists the other 12V sockets and their respective amperage. The front one in the center console is the heavy hitter.

And this socket is hot when the ignition is off?
 

Suza

Member

What does it mean that this charger is Oregon and California approved?
 

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