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Battery Isolator / Alternator question

jc1409

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Hi everyone,

I've got a 150amp battery isolator with one input, and three outputs. A 125a alternator (w/ standard/non-upgraded regulator) is connected to the isolator input. The first output goes to an AGM battery bank, the second output goes to a separate AGM battery bank, and the third output is unused.

I'd like to be able to charge a separate Lithium bank using the alternator. Can I connect a DC - DC charger (Victron Orion DC-DC TR Smart charger 12-12-30a) directly to the third output on the Isolator to do this? Or do I need to connect the DC-DC charger to one of the AGM batteries?

thanks for input
Jeff
 
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Hi everyone,

I've got a 150amp battery isolator with one input, and three outputs. A 125a alternator (w/ standard/non-upgraded regulator) is connected to the isolator input. The first output goes to an AGM battery bank, the second output goes to a separate AGM battery bank, and the third output is unused.

I'd like to be able to charge a separate Lithium bank using the alternator. Can I connect a DC - DC charger (Victron Orion DC-DC charger 12-12-30a) directly to the third output on the Isolator to do this? Or do I need to connect the DC-DC charger to one of the AGM batteries?

thanks for input
Jeff
I have not done that before, but I don't see why it wouldn't work. (BTW: I assume you are talking about the Victron Orion TR SMART)
 
Thanks FilterGuy! Yes, Victron TR Smart (just added this to original post).

Separate but related question and to help me understand how these things should work (note this would not work with my first question - otherwise I would have a 'loop' of charging. This is just separate hypothetical).

If I wanted to add a small DC-DC charger (Victron Orion 12-12-18a TR Smart or even smaller amperage if available), sending current FROM my lithium bank TO my AGM banks, could I simply add the output of the DC-DC charger to the same input that the alternator input attaches on the isolator (so that the isolator would have the alternator and the DC-DC charger on the same input connection)?

I think this would work as:
- both the DC-DC and the alternator (via diodes) would prevent any reverse current
- the Isolator is rated at 150a, and this covers my 125a alternator and 18a Dc-Dc charger

I likely don't need to do this, to keep my AGM batteries topped up, but just curious if in concept this would work.

thank you
Jeff
 
Thanks FilterGuy! Yes, Victron TR Smart (just added this to original post).

Separate but related question and to help me understand how these things should work (note this would not work with my first question - otherwise I would have a 'loop' of charging. This is just separate hypothetical).

If I wanted to add a small DC-DC charger (Victron Orion 12-12-18a TR Smart or even smaller amperage if available), sending current FROM my lithium bank TO my AGM banks, could I simply add the output of the DC-DC charger to the same input that the alternator input attaches on the isolator (so that the isolator would have the alternator and the DC-DC charger on the same input connection)?

I think this would work as:
- both the DC-DC and the alternator (via diodes) would prevent any reverse current
- the Isolator is rated at 150a, and this covers my 125a alternator and 18a Dc-Dc charger

I likely don't need to do this, to keep my AGM batteries topped up, but just curious if in concept this would work.

thank you
Jeff
There might be a problem with the voltages. Will the LiFePO4 circuit get high enough above the AGM voltage to 1) Trigger the Isolator and 2) Charge the AGM? (I don't think so)

1641072059366.png
 
Thank you - Is it correct that if the AGMs are not being charged (resting voltage ~12.8), and the LIFEPO4 batteries are being charged from separate source at ~14.4v (e.g., from solar or shore power), then I could set the the DC - DC to start charging the AGMs by sensing the LIFEPO4 source voltage? (alternator is off during entire scenario)

My goal is to find best way to have power going back and forth between lithiums and AGMs in different scenarios: when engine running, take excess alternator to Lithiums (per DC to DC charger connected to isolator in my first question); and when engine not running, figure out best way to use solar and/or shore power charging of the Lithiums to top off AGM banks.

To cover the 'engine not running' scenario, I think instead of the DC - DC from the Lithium batteries, I will instead just add a small amperage dual bank battery charger that will be powered from shore power, with the dual outputs connected to the two AGM banks I have. This won't let me have charging of AGMs from solar, but not that big of a deal I don't think.

Jeff
 
Is it correct that if the AGMs are not being charged (resting voltage ~12.8), and the LIFEPO4 batteries are being charged from separate source at ~14.4v (e.g., from solar or shore power), then I could set the the DC - DC to start charging the AGMs by sensing the LIFEPO4 source voltage?
Hmmm.... It is not clear to me what the charging algorithm of the DC-DC converter will do. The voltage will never get high enough to make the charger think it needs to go into float.... so what will it do?

Also, once the AGMs are discharged a little, they really should be fully charged back to 100% (Lead acid does not do well if it is left partially charged.) Therefore, the alternator or a shore power charger will be needed.
I think instead of the DC - DC from the Lithium batteries, I will instead just add a small amperage dual bank battery charger that will be powered from shore power, with the dual outputs connected to the two AGM banks I have.
That sounds like a good plan.
 
Connect to battery not to the alternator . The alternator needs initial battery power to start, always have the alternator connected to a LA battery.
Operating the switch from battery to converter may damage both the alternator and the converter.

Mike
 
Thanks Mike,

Understand - I should not connect the output from the DCDC charger, directly to the same 'input' on the battery isolator (together with the alternator).

Jeff
 
I was working on a phone and had to give a short comment.

Without knowing the exact type of isolator switch there are some unknowns. Is it a mechanical switch or a semiconductor? If mechanical is it 'make' before' break'? Do you have a link to the isolator?

The alternator needs battery volts to start producing power so must always have a connection to a battery when the engine is started/running. If the alternator is disconnected from a battery when running it will be damaged, ( unless additional protection circuits are connected to the alternator). If an alternator is connected direct to a lithium battery and the BMS shuts down the charge path a similar issue occurs, the output volts of the alternator 'spikes' damaging the alternator and perhaps anything else connected.

In a normal application Orion DC to DC charger is connected to a LA battery. Once the battery volts rise above a certain voltage level due to charge from the alternator, the Orion becomes active and will charge whatever is connected to its output. If the alternator stops charging the battery volts fall and the Orion switches off.
The charge / float voltages and times are fully programmable on the Orion. It can also be programmed as a power supply.

If the application is different there are a number of options.

a) its possible to program the voltage levels at which the Orion switches on. and off
b) using the H and L control pins the Orion can be forced on regardless of input volts.
c) using the H and L pins the Orion can be enabled and disabled.

I suggest keeping things simple.

I am assuming the two AGM batteries are starter and house/windless batteries.

For engine charging of the lithium connect the Orion to the starter AGM and the output to the lithium. If you wish you can control the Orion via the control pins or the app, that is, turn it on or off.

Connect the solar regulator to the lithium battery.
Connect the shore power to the lithium.

To keep the AGMs topped up, a AC charger from shore power or via an inverter from the lithium.

There are a number of variations you can adopt. What is important is that the alternator is always connected to a LA battery when the engine is running.

Mike
 
Hi Mike,
I have a 150a one input/three output Cristec isolator:


My current house AGM bank is connected to the third isolator output. When I replace with Lithiums, was hoping to just connect a DCDC charger to that third output (in between alternator and Lithiums. The other two outputs on the isolator go to two other AGM banks, so the alternator will always be connected to them in that way. But I guess connecting the DCDC only to the isolator output causes there to be no battery connection for this third output.

I could just add the DCDC to the starter battery - my concern doing this was that it would cause the DCDC to 'turn on' when I am charging the starter battery from a separate shore power charger I plan to use to maintain the battery. e.g. when connected to shore power, I have a small 5a battery charger that will be connected to the starter battery - the Orion DCDC would sense the voltage increase, and start passing charge to the LFP bank.

I guess I could either wire the DCDC to start only when the ignition is on, or just not worry about this situation as it maybe isn't problematic anyway.
 
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Why make it complicated? Just use a breaker switch on the line to the house batteries that you can switch off if you need to charge up the starter battery quickly.
 
one input/three output Cristec isolator
That makes things clearer. A better distribution for the unit would be a 'charge distributer/splitter'. I visualised a 'isolator' that isolated the batteries from the circuits they powered, a common safety feature in marine applications.
Th Cristec unit will transfer power, one way only, to any battery or circuit on any of the outputs whilst isolating the outputs from each other. It is important that the alternator is wired as indicated in the Cristec notes
the Orion DCDC would sense the voltage increase, and start passing charge to the LFP bank.

I guess I could either wire the DCDC to start only when the ignition is on
This would be the preferred method if only the starter battery is needed to charge. The Orion needs to be connected to a battery or a DC source, not the alternator, ( unless the alternator also has a LA battery connected to it)

A more powerful dc supply could be connected to the starter battery and allow the Lithium battery to be charged with the Orion charge profile. Since the Orion can be 'forced' into the on state, or reprogrammed to any start-up voltage level, the voltage of the dc supply could be anything suitable ( the float volts of the AGM ?).

A battery charger could be connected to the input of the Cristec that would charge all batteries and split the current as needed by the batteries, using the normal charge and float values for the AGM.

Mike
 
Thank you Mike!

I appreciate your (and everyone's) explanations. Just to make sure I understand, here is what I'm now planning:
- moved Orion DCDC charger to be connected to starter battery - NOT to the Cristec isolator output
- Orion DCDC charger would be enabled only with ignition ON, to allow charging only when Alternator is supplying current - NOT when shore power is supplying power to the start battery

My goal is to avoid need for any manual switching to enable / disable charging if possible, to avoid user error.

Hopefully this makes sense

1641574766797.png
 
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