DC>DC charger AND isolator? Or instead of isolator?

[Mex Rider]

The isolator is there so that running the house loads in the RV can't drain the starter batteries stranding you in the middle of nowhere. What the isolate will not do is protect your LiFePo4 house battery from being overcharged by the alternator. Nor will it prevent your house battery from cooking the alternator if the house batteries are at too low of a SOC when you try to charge them from the alternator.

A DC-DC charger (like an Victron Orion TR) will provide both charge management for your new lithium batteries and will also protect against draining the starter battery with house loads. The Orion will not however change your starter battery from the house battery.

Far as I can see the DC-DC converter plus a set of jumper cables (in the event you need to jump start the engine from the house battery) will do everything you need. I would replace the isolator with the DC-DC converter since otherwise you will get unnecessary power drop in the isolator.

An alternative if you will have solar power is to use a Renogy DDC50. The provides both alternator and solar charging of the house battery and will also divert solar power to charge the starter battery if needed. The downside to the DDC50 is it is 12V only (no 24V house battery), is not really configurable and has very a low solar panel input voltage limit (25V).

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

Make sure your service battery has all the juice it needs with Renogy's DCC50S DC-DC MPPT On-Board Battery Charger. 10% off: Renogy10off. Free shipping

www.renogy.com

There is an alternative to the Renogy with a higher solar input voltage limit, but the name escapes me. Starts with a K.

Kisae DMT 1250

 

[Kiwi DIYer]

Hi all, I have recently upgraded the "house" batteries in my 1994 class A m/h from 4 x 120 a/h deep cycle to 2 x 200 a/h lithium batteries.
The first time I started the couch engine the alternator belts started slipping and made a very high pitched noise. This was due to the very low resistance of lithium and that my m/h has the house battery charging relay.
To fix this I have installed the Victron Orion-tri smart DC - DC 30 amp charger.
I have used the factory cables from the relay to run the DC -DC charger.
If I ever need to us the "auxiliary start" button on the dashboard due to a flat starting battery, I only need to bypass the DC - DC charger to make a direct connection between the house batteries and the starting batteries.
This is working very well so far. I get a controlled charge to the house batteries, while driving, and can "jump" start if needed.

 

[HaldorEE]

Kisae DMT 1250

That is it. I have no idea why I couldn't remember that. Thanks.

 

[mtnbrit]

Would there be a problem if I keep the boost solenoid connected between the batteries and install the Orion DC-DC, then I use the battery boost button one day to help start the coach? Im guessing the Orion won't care if its input + output are basically shorted out?

 

[Samsonite801]

Would there be a problem if I keep the boost solenoid connected between the batteries and install the Orion DC-DC, then I use the battery boost button one day to help start the coach? Im guessing the Orion won't care if its input + output are basically shorted out?

Is it the Orion-tr Isolated or non-isolated model? It could be a problem with the isolated ones, you might want to ping Victron and ask them before you risked trying it out on yours...

 

[Soggy Man]

Hey guys. I'm new here and I have a solar setup but I plan to reconfigure it soon. I have read this thread and I think I get what I should do but still not sure. I have a Toyota Tacoma with a duel battery set up under the hood. I have the stock battery and a Optima yellow top connected with a Blue Sea ML-ACR relay. From the yellow top I've run cables to a 12V fuse block in the bed for lights etc. I have a Victron MPPT 100/20 solar controller and a 1000 w power invertor as well. I want to switch to a lithium battery as My 12v fridge keeps shutting off if I don't drive the truck literally every day. I think I just can't get enough from the yellow top although I don't think I a using that much power. So there may be another issue but I am stuck as far as what to do. I believe I understand this thread to say just eliminate the relay between the stock battery and the yellow top and replace with a dc to dc charger. I'd like to keep the yellow top up front just have as a back up for starting if possible. I have looked at so much I'm just not sure which way to go. Any help is appreciated.

 

[Reed Cole]

Hey guys. I'm new here and I have a solar setup but I plan to reconfigure it soon. I have read this thread and I think I get what I should do but still not sure. I have a Toyota Tacoma with a duel battery set up under the hood. I have the stock battery and a Optima yellow top connected with a Blue Sea ML-ACR relay. From the yellow top I've run cables to a 12V fuse block in the bed for lights etc. I have a Victron MPPT 100/20 solar controller and a 1000 w power invertor as well. I want to switch to a lithium battery as My 12v fridge keeps shutting off if I don't drive the truck literally every day. I think I just can't get enough from the yellow top although I don't think I a using that much power. So there may be another issue but I am stuck as far as what to do. I believe I understand this thread to say just eliminate the relay between the stock battery and the yellow top and replace with a dc to dc charger. I'd like to keep the yellow top up front just have as a back up for starting if possible. I have looked at so much I'm just not sure which way to go. Any help is appreciated.

You can leave the Optima yellow top and the relay in place and it shouldn't cause any issues if you add a dc-dc charger for a lifepo4 battery. You would simply have two separate charging systems for two separate battery banks running off your vehicle's charging system.

 

[its34below]

Now I am considering upgrading my batteries to LiFePO4

I am considering the same thing, but the don't the high and low temperatures experienced in a vehicle during summer and winter make LiFeP04 a bad option? I live in Virginia. I have a 1000 watt sub and I want to be able to run my 2000 watt Harbor Freight Inverter of of my 2012 Prius. Just in case of a power outage and to support the amps used by the amplifier. I also want the possibility of incorporating a solar panel as well. Of course im trying to be as safe and economical as possible. Don't want to damage my beloved prius.

Im looking at these units. The last one wont accept solar without configuring a relay or something pretty sure.

KISAE DMT1230 Abso 30A DC-DC Battery Charger | DonRowe.com

The KISAE DMT1230 DC to DC Battery Charger is a multi-stage, multi-input battery charger capable of charging different types of batteries commonly installed in boats, RV's, 4WD's and commercial vehicles.

www.donrowe.com

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

Make sure your service battery has all the juice it needs with Renogy's DCC50S DC-DC MPPT On-Board Battery Charger. 10% off: Renogy10off. Free shipping

www.renogy.com

Amazon.com

Thanks

 

[Mex Rider]

I am considering the same thing, but the don't the high and low temperatures experienced in a vehicle during summer and winter make LiFeP04 a bad option? I live in Virginia. I have a 1000 watt sub and I want to be able to run my 2000 watt Harbor Freight Inverter of of my 2012 Prius. Just in case of a power outage and to support the amps used by the amplifier. I also want the possibility of incorporating a solar panel as well. Of course im trying to be as safe and economical as possible. Don't want to damage my beloved prius.

Im looking at these units. The last one wont accept solar without configuring a relay or something pretty sure.

KISAE DMT1230 Abso 30A DC-DC Battery Charger | DonRowe.com

The KISAE DMT1230 DC to DC Battery Charger is a multi-stage, multi-input battery charger capable of charging different types of batteries commonly installed in boats, RV's, 4WD's and commercial vehicles.

www.donrowe.com

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

Make sure your service battery has all the juice it needs with Renogy's DCC50S DC-DC MPPT On-Board Battery Charger. 10% off: Renogy10off. Free shipping

www.renogy.com

Amazon.com

Thanks

The Kisae is more flexible

 

[floydo]

Note when you install the DC-DC converters with MPPT they draw 60-70ma sitting.....so over longer periods of time they can represent a drain. Other DC to DC converters w/o MPPT draw a lot less, if that is important. A solenoid such as a Blue Sea draws no current. So if using solar you may not care since the panels can make up the draw over time...These can be turned off, but that is a manual operation, and yes the KISEA appears more flexible. Higher solar voltage and easily reached on off...etc.

Another aspect of the comments above that I am struggling with is overcharging the Li battery. Since most alternators put out 14.4-14.5v that cannot overcharge as Li battery. Unregulated solar can, but that is really not a configuration on the table. Current draw from an alternator to a thirsty Li batt is a real potential issue...That is the nice thing about DC-DC or a Li BIM duty cycle switch.

 

[Mex Rider]

Note when you install the DC-DC converters with MPPT they draw 60-70ma sitting.....so over longer periods of time they can represent a drain. Other DC to DC converters w/o MPPT draw a lot less, if that is important. A solenoid such as a Blue Sea draws no current. So if using solar you may not care since the panels can make up the draw over time...These can be turned off, but that is a manual operation, and yes the KISEA appears more flexible. Higher solar voltage and easily reached on off...etc.

Another aspect of the comments above that I am struggling with is overcharging the Li battery. Since most alternators put out 14.4-14.5v that cannot overcharge as Li battery. Unregulated solar can, but that is really not a configuration on the table. Current draw from an alternator to a thirsty Li batt is a real potential issue...That is the nice thing about DC-DC or a Li BIM duty cycle switch.

Configurable with the Kisae

 

[floydo]

Configurable with the Kisae

So what is the minimum draw (sitting) without input from solar? The specs say <70ma....? Am I missing something? Thx

 

[Mex Rider]

So what is the minimum draw (sitting) without input from solar? The specs say <70ma....? Am I missing something? Thx

Right this minute my panels are "off" and my BMS is showing no current flowing. The Kisae is connected to the batteries but when I disconnect the PV input even though the Kisae is still turned on the display is off, seems as though its use is not measurable by the BMS, later when I am up and about I will look at the BM 712 but I do have an LED voltmeter and the BM 712 also drawing miniscule current and the inverter connected but off...hope that helps

 

[floydo]

I am really curious, if the panels are disconnected, what might be the draw, as I have panels planned, but really want to operate without (in a vehicle), using this as strictly DC DC. I appreciate your input and anything further you could add!

 

[Reed Cole]

I am really curious, if the panels are disconnected, what might be the draw, as I have panels planned, but really want to operate without (in a vehicle), using this as strictly DC DC. I appreciate your input and anything further you could add!

Seems like a non issue to me. If you are going to have long periods of time where you won't be using your vehicle then have an easy to way to disconnect the charger from your battery, otherwise the draw is negligible.

 

[Mex Rider]

Indeed, as @Reed Cole says, negligible. My panels have been disconnected for more than a week and my batteries have not dropped a volt.

 

[Mex Rider]

Indeed, as @Reed Cole says, negligible. My panels have been disconnected for more than a week and my batteries have not dropped a volt.

I have been watching my BM-712 and the draw is .15 amps, of course your draw will depend on your equipment. My draw reflects keeping the capacitors in my 3000 watt inverter charger and the Kisae DMT 1250 as well as an LED volt meter, the Victron battery connect, which has an LED flashing and all of the load circuitry. But still, it is a very small draw.

 

[BajaMatt]

The isolator is there so that running the house loads in the RV can't drain the starter batteries stranding you in the middle of nowhere. What the isolate will not do is protect your LiFePo4 house battery from being overcharged by the alternator. Nor will it prevent your house battery from cooking the alternator if the house batteries are at too low of a SOC when you try to charge them from the alternator.

A DC-DC charger (like an Victron Orion TR) will provide both charge management for your new lithium batteries and will also protect against draining the starter battery with house loads. The Orion will not however change your starter battery from the house battery.

Far as I can see the DC-DC converter plus a set of jumper cables (in the event you need to jump start the engine from the house battery) will do everything you need. I would replace the isolator with the DC-DC converter since otherwise you will get unnecessary power drop in the isolator.

An alternative if you will have solar power is to use a Renogy DDC50. The provides both alternator and solar charging of the house battery and will also divert solar power to charge the starter battery if needed. The downside to the DDC50 is it is 12V only (no 24V house battery), is not really configurable and has very a low solar panel input voltage limit (25V).

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

Make sure your service battery has all the juice it needs with Renogy's DCC50S DC-DC MPPT On-Board Battery Charger. 10% off: Renogy10off. Free shipping

www.renogy.com

There is an alternative to the Renogy with a higher solar input voltage limit, but the name escapes me. Starts with a K.

I know this is an old thread, but it's relevant to my current issue. Is there any significant problem or downside to installing a DC to DC controller downstream of an isolator? My main goal with the DC to DC charger is to "remove" the truck battery from the system when idle and allow the solar to charge the lithiums to a full 14.4V.

 

[HRTKD]

I know this is an old thread, but it's relevant to my current issue. Is there any significant problem or downside to installing a DC to DC controller downstream of an isolator? My main goal with the DC to DC charger is to "remove" the truck battery from the system when idle and allow the solar to charge the lithiums to a full 14.4V.

Can you provide more details? I'm not sure what order the components are intended to be in.

PV -> solar charge controller -> LiFePO4 <- DC-DC <- Isolator <- Truck battery

 

[BajaMatt]

Can you provide more details? I'm not sure what order the components are intended to be in.

PV -> solar charge controller -> LiFePO4 <- DC-DC <- Isolator <- Truck battery

Your order is correct.