How to trickle charge starter battery from house battery set up?

[DRP]

I had not heard about the Amp-l-start builders passing. I had noticed it no longer was available but had not heard why, Too bad, great product and mine has functioned perfectly for 3-4 years now.
I do use mine with a Victron BtoB and the only hicup is that when the AmplStart starts pushing up voltage the BtoB thinks that the alternator is on supplying juice and turns on, sucking from the Chassis battery to try to charge my 600AmHr House bank.
A simple switch on the dash stopped that and I actually like being able to choose when the BtoB is on.,
Also, I feed the AmpLStart from the Load terminals of one of my charge controllers. That way it only takes power when the sun is shining

 

[DiploStrat]

Based on my "Twisted Sister™" set up.

-- Wire the feed from the starter battery to the B2B that feeds the camper to close only when the engine is running.

-- Wire the feed from the camper battery to the B2B that feeds the starter to OPEN when the engine is running. (Use a normally closed "crossover" relay. Basically, when energized it opens the primary circuit and closes the secondary circuit - to which you have nothing connected. Think about it a second, it works.)

So, engine on, starter battery charges camper. Engine off, camper battery charges starter.

N.B.

-- This ain't cheap, but you can save a little bit by buying the smallest B2B you can find for the feed from the camper battery to the starter battery.

-- If you have a lithium iron camper bank, the B2B feeding the starter battery may never turn off as the camper batter will almost always be above 13.2v, the usual turn on voltage.

-- You can wire manual switches for positive control, but, in my case, with a big camper battery, I have never bothered, the B2B simply spends most of its time in float and the draw is negligible.

Enjoy!

 

[Superduty]

I have been using boost circuit boards for years to do that. Boost circuits only increase voltage, which is what is needed when a higher voltage than resting battery voltage is required to charge another battery.

Locate the boost module close to the start battery(s), same as with a solar charge controller.You simply connect the boost module's input to the source battery with long small wires (16-18 awg), and the output wires to the battery being charged. Dial in the charging voltage required for a trickle charge, then walk away.

When arriving at camp, both batteries should be charged, so initial charge current will be low.

Fuse the input for 5 to 10 amps. If you don't disconnect the module before cranking, the lowered starting battery voltage can cause a high module output, and fry it. Learned the hard, but inexpensive way.

I use the same module to keep the voltage level up to my 12v fridge to avoid low voltage beeping, blinking, and shutdown.

So, when you start your vehicle you disconnect this item from the start battery?

Does it prevent any current from going back from the start battery to the house battery?

Assume you set it at 12.6v, does it stop sending voltage to the start battery when it reaches 12.6v?

 

[Superduty]

Based on my "Twisted Sister™" set up.

-- Wire the feed from the starter battery to the B2B that feeds the camper to close only when the engine is running.

-- Wire the feed from the camper battery to the B2B that feeds the starter to OPEN when the engine is running. (Use a normally closed "crossover" relay. Basically, when energized it opens the primary circuit and closes the secondary circuit - to which you have nothing connected. Think about it a second, it works.)

So, engine on, starter battery charges camper. Engine off, camper battery charges starter.

N.B.

-- This ain't cheap, but you can save a little bit by buying the smallest B2B you can find for the feed from the camper battery to the starter battery.

-- If you have a lithium iron camper bank, the B2B feeding the starter battery may never turn off as the camper batter will almost always be above 13.2v, the usual turn on voltage.

-- You can wire manual switches for positive control, but, in my case, with a big camper battery, I have never bothered, the B2B simply spends most of its time in float and the draw is negligible.

Enjoy!

Cool idea. If I am understanding correctly you are using one B2B and reversing it? If that is correct, I believe the B2B is programmed with a particular charge profile. If I set up the lifepo4 profile, won't that be an issue when it is reversed and charging the FLA start battery?

 

[DiploStrat]

Cool idea. If I am understanding correctly you are using one B2B and reversing it? If that is correct, I believe the B2B is programmed with a particular charge profile. If I set up the lifepo4 profile, won't that be an issue when it is reversed and charging the FLA start battery?

No - two units. 24v > 12v from the starter battery to the camper and 12v > 24v from the camper battery to the starter. (If I had had the choice, I would have simply gone with a full 24v camper set up and used a step down converter for the last loads. )

 

[Hegear]

PWM units generally need to be held to less than 32v, so, if your panels are in parallel (like mine) they are likely to be running at over 50v.

I like the idea of double tapping the panels to a second controller, I just don't know the implications of doing this.

For the task of simply maintaining a lead acid starter battery you do not need a super sophisticated charger. (One reason why the AMP-L-Start was such a great product.

I thought running in parallel just increased the amps not the volts.

 

[Hegear]

Also if you bought a dual dc to dc/mmpt they trickle charge the car battery of the solar once the house battery is full.

I have both the redarc and renogy and they both have this function.

 

[waltermitty]

Parallel = totals up the amperage and maintaining voltage at 24
Series = adds up the voltage to 48 while maintaining single panel amperage

you're correct

I thought running in parallel just increased the amps not the volts.

 

[DiploStrat]

I thought running in parallel just increased the amps not the volts.

OOOPS! Age aches! You are correct, parallel boosts amps not volts. Lots of us like to go to parallel as it reduces the load on the wires and MPPT controllers love the higher voltage.

 

[burleyman]

So, when you start your vehicle you disconnect this item from the start battery?

Does it prevent any current from going back from the start battery to the house battery?

Assume you set it at 12.6v, does it stop sending voltage to the start battery when it reaches 12.6v?

Most inexpensive boost modules prevent reverse current. Mine does by use of a diode.

No, it does not shut down. it is basically a permanent load as long as the house/source battery is connected and the start battery is connected to the boost module. It can and will eventually drain the source battery.

I may have misunderstood the main objective. My use of the boost module is for short-term camping with solar charging available. As jonyjoe stated, a parked vehicle continuously drains the battery. For long-term storage, without solar or some other way to keep the house battery charged, connecting a simple boost module (poor man's B2B) would eventually discharge the house battery as the boost module is always on and is also a parasitic load. A lithium with a BMS should shut down output before completely drained.

The module I use would drain an unprotected battery to about 3v before the module would shut down. Not good. I only use mine as needed by glancing at start voltage provided by a dc voltmeter plugged into a cigarette lighter female.

How long-term is long-term? It's often stated not to leave lithiums fully charged for long term storage. If you stay parked long term between adventures, the solar would keep the lithium charged. Supposedly, also not good.

If your MPPT can provide proper start battery charging, what billiebob posted or similar. Turn off charging to the lithium when stored LONG term, and connect solar charging to the start. It would also allow you to connect both batteries to solar when needed while camping.

 

[Superduty]

Also if you bought a dual dc to dc/mmpt they trickle charge the car battery of the solar once the house battery is full.

I have both the redarc and renogy and they both have this function.

I have a victron dc to dc and i don't believe that it will function like that.

Which redarc or renogy models offer that feature?

Sent from my SM-G973U using Tapatalk

 

[Hegear]

I have a victron dc to dc and i don't believe that it will function like that.

Which redarc or renogy models offer that feature?

Sent from my SM-G973U using Tapatalk

BCDC Classic 40A In-vehicle DC Battery Charger

The REDARC BCDC1240D is a 12V, 40A In-vehicle DC to DC Battery Charger designed to keep your auxiliary battery charged when driving or with portable solar panels when parked.

www.redarcelectronics.com

DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT

Introducing the RBC50D1S, harnessing MPPT solar charging and starter battery charging to provide rapid replenishment for house batteries. Equipped with multiple electronic protection mechanisms, it ensures optimal energy utilization without compromising the vehicle's starter battery.

www.renogy.com

There are multiple models with different amperage. I have used both and they both function well. Redarcs are about half the size of renogy but double the price.
I’m sure there are other company’s that make them as well.

 

[dragonbyu]

BCDC Classic 40A In-vehicle DC Battery Charger

The REDARC BCDC1240D is a 12V, 40A In-vehicle DC to DC Battery Charger designed to keep your auxiliary battery charged when driving or with portable solar panels when parked.

www.redarcelectronics.com

DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT

Introducing the RBC50D1S, harnessing MPPT solar charging and starter battery charging to provide rapid replenishment for house batteries. Equipped with multiple electronic protection mechanisms, it ensures optimal energy utilization without compromising the vehicle's starter battery.

www.renogy.com

There are multiple models with different amperage. I have used both and they both function well. Redarcs are about half the size of renogy but double the price.
I’m sure there are other company’s that make them as well.

Redarc will not trickle charge the start battery after the aux is full using solar.

 

[Hegear]

Redarc will not trickle charge the start battery after the aux is full using solar.

So sorry I thought it did.

 

[dstefan]

Came across this a couple days ago. Seems relevant.