I would like to add a second isolated house bank of lithium to my existing Lead Acid - 1 starter, 2 battery house bank system. The new 200 AH lithium system would have its own distribution panel isolated from the old system. The new system would power essential electronics and navigation equipment. I would like to charge the Lithium with a DC-DC charger from the house bank. The existing lead acid house bank is charged via the alternator, solar and shore power. Any thoughts on this idea?
Adding a 2nd House Bank of Lithium to old system
- Thread starter WaterBear
- Start date
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,711
This could work.
Will all 3 systems stay 12 volt?
How much power will you be drawing off of the new lithium system?
What do you expect the total watt hours to be?
Something like the Victron Orion-Tr can charge 12 volt to 12 volt. That version can do up to 18 amps, about 220 watts to the lithium batttery, and it's isolated with no ground connection between the two battery systems.
It has a terminal that will enable it, normally used to turn it on when the alternator is providing power, but it can also be triggered manually or by a voltage sensor. When the existing lead acid system voltage is up near the absorb limit, it could turn on to charge the lithium system and shut back off if the voltage falls below a set point. That way it won't drain the existing system too low.
Will all 3 systems stay 12 volt?
How much power will you be drawing off of the new lithium system?
What do you expect the total watt hours to be?
Something like the Victron Orion-Tr can charge 12 volt to 12 volt. That version can do up to 18 amps, about 220 watts to the lithium batttery, and it's isolated with no ground connection between the two battery systems.
It has a terminal that will enable it, normally used to turn it on when the alternator is providing power, but it can also be triggered manually or by a voltage sensor. When the existing lead acid system voltage is up near the absorb limit, it could turn on to charge the lithium system and shut back off if the voltage falls below a set point. That way it won't drain the existing system too low.
Brucey
Solar Wizard
I believe there's a "smart" aka Bluetooth enabled Orion unit coming soon if you needed full control.
MisterSandals
Participation Medalist
100Wh / 12.8V = 7.1Ah battery? sounds way too small
I was thinking of a 200 AH battery - so lots of spare capacity if needed, with not that much more expense or space required. Thoughts?
MisterSandals
Participation Medalist
Do you know how much power (watts) each of your items uses and for how long (hours) you expect them to run on a battery charge? ...to get Wh number necessary for sizing a battery.
And would your DC-DC charger of choice keep up if necessary?
Radar - 24 hours - 17 watts
AIS - 24 hours - 3 watts
Chartplotter - 24 hours - 10 watts
Occasionally (hopefully never) a back up bilge pump - 100 watts
Auto Tiller (engine running) 1- 8 amps depending on the conditions
Lighting and all the original systems are on the other house bank as originally installed.
I was considering the Victron Orion-Tr Smart DC-DC - 20A charger wired from the Lead acid house bank which is charged with 200 watts of solar when at sea.
I am trying to keep it simple and functional without re-doing the whole system.
AIS - 24 hours - 3 watts
Chartplotter - 24 hours - 10 watts
Occasionally (hopefully never) a back up bilge pump - 100 watts
Auto Tiller (engine running) 1- 8 amps depending on the conditions
Lighting and all the original systems are on the other house bank as originally installed.
I was considering the Victron Orion-Tr Smart DC-DC - 20A charger wired from the Lead acid house bank which is charged with 200 watts of solar when at sea.
I am trying to keep it simple and functional without re-doing the whole system.
GXMnow
Solar Wizard
- Joined
- Jul 17, 2020
- Messages
- 2,711
Your first 3 items total to 30 watts for 24 hours. 30 x 24 = 720 watt hours. Or 0.72 kilowatt hours. When things run 24 hours a day, the energy needed does add up. That really does need every bit of a 100 amp hour 12 volt battery. 100 x 12 = 1,200 watt hours. One day is using 60% of the full battery capacity.
On the bright side, the 18 amps you can get from the Orion 12-12 charger is more than enough to keep up. But your solar panels alone might not be. 200 watt of solar panels would need to grab abut 4 sun hours a day to just keep up with those constant loads. To do that, you would need to have them tilted towards the sun. Flat on the roof won't do it. 200 watts of solar into 12 volts is a theoretical maximum current of 16.667 amps. It will typically be only 80% in good conditions, and even a bit less as battery voltage is higher than 12, but I like to plan for maximums. As the sun passes over, the power available follows a bell curve. You only get up to 160 watts (80%) when the sun is directly overhead. From sunrise to solar noon, it ramps up, then ramps back down to sunset.
When the engine is running, you can pull alternator power, but how long are you engine off? I think you need more solar panel.
On the bright side, the 18 amps you can get from the Orion 12-12 charger is more than enough to keep up. But your solar panels alone might not be. 200 watt of solar panels would need to grab abut 4 sun hours a day to just keep up with those constant loads. To do that, you would need to have them tilted towards the sun. Flat on the roof won't do it. 200 watts of solar into 12 volts is a theoretical maximum current of 16.667 amps. It will typically be only 80% in good conditions, and even a bit less as battery voltage is higher than 12, but I like to plan for maximums. As the sun passes over, the power available follows a bell curve. You only get up to 160 watts (80%) when the sun is directly overhead. From sunrise to solar noon, it ramps up, then ramps back down to sunset.
When the engine is running, you can pull alternator power, but how long are you engine off? I think you need more solar panel.
I don't like the OP post for this reason:
I recently replaced my long used FLA battery bank with a lithium bank. If I am reading your post correctly, you have an older FLA bank and want to use it's capacity to charge a lithium battery connected to a separate load panel.
Here's what gives me pause:
FLA lead acid batteries undergo much greater voltage drops under load than do lithium batteries. The internal resistance of the FLA battery to charging is much higher, the lithium battery can charge and discharge much faster than an FLA possibly limiting the efficiency of the lithium advantage. The FLA battery will lose capacity much quicker than the lithium.
My personal opinion is that if you can afford to keep your original idea, but just check the FLA battery (sell it off locally as I did my older bank) and switch to all lithium, then you will get the very high efficiency lithium provides and much more predictable and reliable operation.
I recently replaced my long used FLA battery bank with a lithium bank. If I am reading your post correctly, you have an older FLA bank and want to use it's capacity to charge a lithium battery connected to a separate load panel.
Here's what gives me pause:
FLA lead acid batteries undergo much greater voltage drops under load than do lithium batteries. The internal resistance of the FLA battery to charging is much higher, the lithium battery can charge and discharge much faster than an FLA possibly limiting the efficiency of the lithium advantage. The FLA battery will lose capacity much quicker than the lithium.
My personal opinion is that if you can afford to keep your original idea, but just check the FLA battery (sell it off locally as I did my older bank) and switch to all lithium, then you will get the very high efficiency lithium provides and much more predictable and reliable operation.
G - You have a good point - in order to convert to Lithium, what else did you change? I guess all I would need is a new charger and to ensure the alternator was correctly set up for the change. I have a couple of Dyno 85 AH to sell !
Thanks for your input - all good points to consider, so I really should look at how the whole system will work - I guess the radar and chart-plotter dont need to run for 24 hours and i could put in more capacity (200 AH?) without a huge increase in cost. Don't know if i have space for another solar panel without a whole new framework to support it.
I could have stayed with my older Outback Power system which was a tank, but I chose to jettison it all in favor a new Hybrid inverter that would be closed loop with my lithium batteries, set battery type and forget charging issues. The Outback Power supported my new batteries, but would not be closed loop communications, it would have been open loop and I was trying to simplify things for others in the future.
To me, my experiences with 8 years of solar tell me that planning in number one when it comes to the system. Understanding your power needs and expected solar generation and what you are installing is paramount to avoiding disappointment and failures.
