AMP-L-START compatible with Battleborn lithium batteries?

[jeegro]

Diplo, thanks for laying it all out again. I think I finally have this figured out, except for one thing.

THE PLAN:

• BCDC to charge the house lithium using alternator and solar as charge sources
• Magnum SBC to keep the starter batteries topped up WHEN parked, using the Solar from the BCDC

Here's the three scenarios that need to be accounted for when using the SBC:

1. No charge sources available (all batteries are resting)

Solution: No worries, the SBC is disconnected.

2. Parked, solar charging available

Solution: No worries, the BCDC will prioritize solar and ignore the high volts seen at the alternator due to the SBC being connected

3. Vehicle running, alternator charging available

Solution: ?? I think the SBC needs to be completely disabled, automatically. Reason being, let's say house battery is super low, the BCDC will kick on and start charging from the alternator @ 40 amps, the house battery voltage will rise, thus kicking on the SBC, and now the lithium house batt will attempt to pull 25 additional amps (SBC limit) through the SBC and charge. So, effectively charging at 65 amps (25 SBC + 40 BCDC). I don't want that to happen, I only want the lithium to be charged through the BCDC.

Looking at the SBC manual, there isn't a terminal to remotely disable the unit. So I think I need to switch the ground lead on the SBC, thus turning it off? How do I switch ground using a relay?

Am I on the right track?


Side note - Joel @ LSL Products informed me the TRIK and AMP-L-START is not suitable for lithium:

Yep, that's a problem.

After it's turned on, AMP-L-START doesn't disconnect until the house
battery voltage drops to 12.8 volts.

BOTTOM LINE: Not suitable for your application.

Joel Donaldson

 

[dreadlocks]

How do I switch ground using a relay?

exactly same way as you switch positive.. hook chassis to COM and device ground to NO.. just get a relay that has its own connectors for the coil.

 

[DiploStrat]

With no guarantees:

I think that the SBC is controlled by it's ground lead. So, if you use a normally relay to control that, you should be able to set up a system where the SBC circuit is open (i.e. is off) whenever the engine is running. (You can test this by setting up the SBC and disconnecting the ground. If the lights go out then it needs the ground to operate and you are good to go. If not, see the alternative at the end of this post.)

See the attached which I cobbled up.

This is the most elegant option.

Alternatively, simply place the normally closed relay in the actual line between the two batteries. In this case, you must use a relay capable of passing 25A @ 12v.

If you look at my Twisted Sister, you will see the pin out of a standard relay. (Look on the circuit with the BCDC 2425.

 

[dreadlocks]

Have you seen this: https://battlebornbatteries.com/shop/lifepo4-battery-isolation-manager/

 

[DiploStrat]

Have you seen this: https://battlebornbatteries.com/shop/lifepo4-battery-isolation-manager/

Interesting toy. It appears to be designed to protect the alternator from overheating by imposing 20 minute cool off sessions. Will not work Chevrolets, among others, that routinely exceed 15v, especially in winter. (I had the same problem with the SBC on my Chevrolet - the 15v cut off made it useless in cold weather.)

"If the coach battery resting voltage exceeds 13.4V than the BIM will disconnect. A resting voltage greater than 13.4V indicates a fully charged battery. Note that “resting voltage” means that no current is flowing to the coach battery."

This may defeat the purpose of charging the starter battery as I suspect that the solar controller will be holding the camper/coach battery closer to 14v.

Might be worth discussing with Battle Born or the folks at Precision Circuits, Inc.

Don't like to speculate about kit that I have not actually used.

Of course, the best option is to simply ask Battle Born what they would recommend. That gets us amateurs out of the way.

 

[jeegro]

Great, makes sense! I'll give it a go.

Have you seen this: https://battlebornbatteries.com/shop/lifepo4-battery-isolation-manager/

I don't think that would work. That's for using the alternator to charge the house, as a substitute for a BCDC:

"The BIM will disconnect if the alternator voltage drops below 13.3V. If the alternator voltage is too low, than it cannot adequately charge the coach battery, so there is no reason to connect."

 

[jeegro]

I emailed Magnum, and they said to switch one of the positive leads, not ground. Alright. Would a regular 40A automotive relay work? Then I simply use pin 87a. I'm not sure if one of the batts could attempt to push 100+ amps through it before the SBC has a chance to limit the current.

I have one of these laying around... https://www.amazon.com/dp/B0064MX7US/ref=nb_sb_ss_w_ab-sx-bia_k0_1_16?crid=20X052JAFRPC6
But I don't think it's possible to use it as a normally closed relay. I've been trying to find normally closed solenoids but no luck so far, any recommendations?

edit: possibly this? https://www.ebay.com/itm/Cole-Herse...384035&hash=item2a999437bd:g:mc4AAOSwvTpaM9RR

 

[DiploStrat]

Nope. Those are SPST relays. That means the contacts are open until connected. You want a DPST relay. (Double pole/Single Throw)

REDARC USA will sell you one, but they are very expensive. https://redarcelectronics.com/products/rk1260_relay_kit

Call Picker Components: https://pickercomponents.com/index.html and tell them what you want. You can buy from Amazon.

Looks like my diagram failed to attach to the previous post. You want to copy the wiring on the BCDC2420 circuit. (Ignore the BCDC1240D circuit.)

Terminals:

30 - One leg of the SBC load circuit
85 - Ground
86 - Ignition. When the ignition is on, this is hot
87A - Other leg of the SBC load circuit.

When the engine is off, 87A and 30 are connected.
Engine on, the contact moves to 87, where there is nothing connected, so the load circuit through the SBC is open. The SBC will still work, but no current will flow between the batteries.

Hope this helps.

(EDITED TO ADD: Be careful studying this diagram. It is designed to work 'backwards." Normally, the blue wire on the 2420 is connected to the ignition so that it is only running when the engine is on. In this case, the blue wire is connected to the source battery, but only when the engine is OFF.
When the ignition is on, the contact moves from 87A to 87. Since there is nothing connected to 87, this has the effect of shutting off the power from the 2420.

The point here is to understand how to wire a relay so that it works backwards.

So, in this case, you would put a relay on one of the wires that runs to the SBC, connecting it to the 30 and 87A terminals. Thus the SBC can pass current when the engine is NOT running. When the engine is on, the contact will be pulled to 87 and, since there is nothing there, the SBC will not have anything to pass. It will still operate, but the circuit between the batteries will be open.)

 

[jeegro]

Awesome. I understand this. I'll get crackin' and report back. Lot's to do

 

[john61ct]

+1 @DiploStrat

nit picks

That is they take from the starter battery and give to the camper battery

Even if the connection is attached physically to the "source" battery, it is still just a connection between circuits.

The charging of the target battery is actually coming from the active charge source, shore, solar, alt whatever, whichever batt is on the source side circuit does (should) never be depleted by that process.

Much better if the sources go direct to House, as keeping Starter topped up is very minor current.

If you do know another connection point off the battery posts is good, fine to use that.

If the voltage requirements are different, you either adjust the voltage of your vehicle (harder) or use a battery to battery charger (B2B) between the starter battery and the camper battery. (Easier) Lots of brands to choose from, each having different advantages

Option C - put in a Starter batt that matches those comprising House.

Sterling Power and TRK-L-START make simple units. There may be a problem with the voltage points with lithium

No, Sterling BB series DCDC allows for user-custom setpoints

 

[john61ct]

Agreed, should be automatic

Which part would flatten the starter

Any option that could leave the connection closed, with no charge sources active but House loads drawing down.

 

[jeegro]

For the relays, these should be fine?: https://www.ebay.com/itm/12V-80A-5-...917435?hash=item4d8309773b:g:dNwAAOSwdC5ceEl5

They don't look like much, but heck of a lot cheaper than the Redarc.

I'm planning on using ACC2 switched power for the relay. That way there is no chance in the relay being closed when the starter kicks on.

 

[jeegro]

Any option that could leave the connection closed, with no charge sources active but House loads drawing down.

This made me think of a potential issue. With the truck off, solar on (SBC on), and drawing loads from house batt... will the starting batteries supply any of the current for house loads? Wouldn't this throw off my battery SoC monitor? (Blue sea 1830, shunt)

I feel like what I actually need is a one way (diode based?) trickle charger, voltage sensing, not a battery combiner.

 

[DiploStrat]

+1 @DiploStrat

nit picks

Even if the connection is attached physically to the "source" battery, it is still just a connection between circuits.

The charging of the target battery is actually coming from the active charge source, shore, solar, alt whatever, whichever batt is on the source side circuit does (should) never be depleted by that process.

Much better if the sources go direct to House, as keeping Starter topped up is very minor current.

If you do know another connection point off the battery posts is good, fine to use that.

Agreed. A circuit is a circuit. There is always a challenge getting from logical circuit design and practical installation. (And vice versa is even worse! )

Option C - put in a Starter batt that matches those comprising House.

True, but he wants to use a lithium camper battery and lithium has challenges as a starter battery given the vagaries of vehicle charging circuits and freezing temperatures. Similar problem arises with some Toyotas that have very low charging voltages. They have lead acid starting batteries, but they cannot really charge house/camper/coach batteries, thus providing the entire raison d'etre for B2B's. (Interesting possibility - might such 13.9v vehicles be perfect for lithium camper batteries? I would suspect so. The timing device that is mentioned above might be reasonable protection against alternator overheat.)

No, Sterling BB series DCDC allows for user-custom setpoints

I was talking about the BM battery maintainer, not the BB series of B2B. (https://www.sterling-power-usa.com/sterling-power-usa12vto12vbatterymaintainer.aspx) In my own case, using a second B2B to maintain the starter battery is like using a sledge hammer on ants. Had I seen that Sterling has a 12v>14v BM I would have used that. I can't imagine that you really need a full blown B2B just to maintain a starter battery.

 

[DiploStrat]

This made me think of a potential issue. With the truck off, solar on (SBC on), and drawing loads from house batt... will the starting batteries supply any of the current for house loads? Wouldn't this throw off my battery SoC monitor? (Blue sea 1830, shunt)

I feel like what I actually need is a one way (diode based?) trickle charger, not a battery combiner.

You are overthinking again. You want the solar/shore power to raise the voltage of the house battery to the point that it closes the circuit in the SBC. At this time the charge will be shared with the starter battery. (It won't take much, only an amp or three.) If the sun goes down or you unplug the shore charger, the voltage of the house battery will drop. Since you have set the voltage on your SBC to a voltage HIGHER than "full" charge, the SBC will disconnect long before there is any risk to the house battery.

Added benefit - should you put a charger on the starter battery, and its voltage rises above the set point, then the SBC will close and the charge from the starter battery will start to maintain the house battery.

I used an SBC for years and it works perfectly. My only problem was that it disconnects at 15v and my Chevrolet charged at over 15v whenever the weather was cold. That is why:

A: I installed a manual dash switch with tell tale, and,
B: Next time I would simply use a BlueSea ACR.

In your case, you don't care about the 15v limit, but you do want to raise the connect voltage above the lithium resting voltage.