Hello guys - It's a bit more difficult mixing other batteries with Relion LT (low temperature) since these batteries charge at different speeds than a standard lithium battery. As the Relion LT is charged in cold temperatures, it first uses the amperage from your battery charger to first heat the cells, this can take around 6-8 amps and up to an hour. Once the battery reaches temperature, it then accepts a higher charge. You would be better off spending a bit more money and purchase another Relion battery.
Not sure of your installation, but if the lithium battery exposed to cold weather, you would increase your batteries capacity another 25-30% in winter by just relocating the battery inside the coach. This would also avoid using the built in heater as well. Here's an image below where I re-locacted my battery under the sink on my Compass.
I installed regular fuse don't care for the terminal fuse provided, as well as another battery cut-off. I built a wood removable platform over the battery so I'm not losing any space, I still have a trash can over the battery. Not shown in this image but I also added a strap and blocking to prevent the battery from moving.
I'm writing an In Depth article on the Compass covering dozens of upgrades to include a Dual Lithium Battery System, should be out in a week or so.
Stay Safe - Mike Mas
Correct- you do not want to mix battery types- should all be the same, age as well.
The terminal fuse is for the Balmar regulator if you have a UHG system- if the battery dies, the Balmar will sense that and "know" when to charge the battery.
If no voltage present, the regulator will sense that and preserve the UHG.
If the MRBF fuse is absent, the regulator will be unable to sense a problem, and it will not perform as intended and could damage the UHG.
So if you have a UHG, best to put that terminal fuse back on and red sensor wire atop of the cable lug so it can do it's job.
PM me for my PDF on how I moved my batteries up inside, and upgraded to 600A. It has details regarding that fuse and sensor wire. Critical as the UHG will fail if not on top of MRBF fuse.
I suppose if you use the exterior breaker, then at least attach the sensor lead atop the output lug so it can perform as it should.
Pics below show location of sensor wires from regulator (Balmar MC-618):
Top pic shows, red wire from Balmar pin #1 totop of lug on battery B+ post. Bottom pic shows red wire from Balmar pin #9 totop of lug on UHG B+ feed. (nut is loose-tightened after pic was taken!)
Hello guys - It's a bit more difficult mixing other batteries with Relion LT (low temperature) since these batteries charge at different speeds than a standard lithium battery. As the Relion LT is charged in cold temperatures, it first uses the amperage from your battery charger to first heat the cells, this can take around 6-8 amps and up to an hour. Once the battery reaches temperature, it then accepts a higher charge. You would be better off spending a bit more money and purchase another Relion battery.
Not sure of your installation, but if the lithium battery exposed to cold weather, you would increase your batteries capacity another 25-30% in winter by just relocating the battery inside the coach. This would also avoid using the built in heater as well. Here's an image below where I re-locacted my battery under the sink on my Compass.
I installed regular fuse don't care for the terminal fuse provided, as well as another battery cut-off. I built a wood removable platform over the battery so I'm not losing any space, I still have a trash can over the battery. Not shown in this image but I also added a strap and blocking to prevent the battery from moving.
I'm writing an In Depth article on the Compass covering dozens of upgrades to include a Dual Lithium Battery System, should be out in a week or so.
Stay Safe - Mike Mas
Also, you better make sure that trap never leaks! If you do any plumbing service, remove the battery first!! I hope you have a better spot for the upgrade... be safe!
Thanks for the replies guys - Regarding the terminal fuse, It appears someone might have given you some misinformation. The fuse on Thor RV's is nothing other than a cheap fuse. Many (newbie to lithium) companies use them since it saves the work and cost of adding "real fuse protection". These fuses saves the cost of a fuse block, fuse, cables, terminals and labor!
These fuses have no logic or sensors to communicate with the batteries BCM. All they do is open-up during an overload or short. They are terribly designed, while you might get away using them for low loads like a house battery, I don't recommend them on anything larger than a 50-100 ah battery and certainly not on any lithium system running a roof AC unit, use a real fuse terminal. I included an image below where I use a pair of these double fuses blocks on larger 51 volt 32,000 wh lithium inversion systems.
If you remove and observe the fuse, you'll see there is only a small sleeve touches the battery post, I've seen these arc before and melt the entire plastic housing & fuse. I included an image of the actual fuse to show the contact area. As shown, there's just a very thin washer that contacts the battery post, maybe only 20% the size of a real terminal lug and it's "Not" copper either.
You can mix any lithium 12 volt battery, even with different cells or even different capacity, say a 100 ah and a 120 ah or a 200 ah with a 100 ah. I've been doing so for over a decades the batteries could care less each works in its own environment. Voltages within different sets will equalize to each other during charging or discharging. In fact, if you had one battery at 50% soc and the other at 100% soc, the full battery would discharge into the lower battery to bring the lower charge up until they equalize. Charging is the same. Each battery will accept charge according to its SOC and voltage.
Regarding my Compass battery location and the battery getting wet! Have no concerns, remember this battery was originally located outside under the coach in the direct water path of the front tire where the battery is soaked each time you drive in the rain.
Thanks for the replies guys - Regarding the terminal fuse, It appears someone might have given you some misinformation. The fuse on Thor RV's is nothing other than a cheap fuse. Many (newbie to lithium) companies use them since it saves the work and cost of adding "real fuse protection". These fuses saves the cost of a fuse block, fuse, cables, terminals and labor!
These fuses have no logic or sensors to communicate with the batteries BCM. All they do is open-up during an overload or short. They are terribly designed, while you might get away using them for low loads like a house battery, I don't recommend them on anything larger than a 50-100 ah battery and certainly not on any lithium system running a roof AC unit, use a real fuse terminal. I included an image below where I use a pair of these double fuses blocks on larger 51 volt 32,000 wh lithium inversion systems.
If you remove and observe the fuse, you'll see there is only a small sleeve touches the battery post, I've seen these arc before and melt the entire plastic housing & fuse. I included an image of the actual fuse to show the contact area. As shown, there's just a very thin washer that contacts the battery post, maybe only 20% the size of a real terminal lug and it's "Not" copper either.
You can mix any lithium 12 volt battery, even with different cells or even different capacity, say a 100 ah and a 120 ah or a 200 ah with a 100 ah. I've been doing so for over a decades the batteries could care less each works in its own environment. Voltages within different sets will equalize to each other during charging or discharging. In fact, if you had one battery at 50% soc and the other at 100% soc, the full battery would discharge into the lower battery to bring the lower charge up until they equalize. Charging is the same. Each battery will accept charge according to its SOC and voltage.
Regarding my Compass battery location and the battery getting wet! Have no concerns, remember this battery was originally located outside under the coach in the direct water path of the front tire where the battery is soaked each time you drive in the rain.
Regards - Mike
Good info- and I will look into replacing with a real breaker- as my two 600Ah batteries have these from my transfer/ugrade, and point taken about running large loads, though I have run my AC as a test when did the upgrade and all went well, and since has been ok too.
I think a 250A breaker/fuse on the B+ before it goes to the buss bar is a better idea. Then I can see when it trips- these guys are hard to determine. That will cover a draw of up to 3000W- should be plenty.
When I do that, I will move my Balmar regulator sensor wire to the output side of the new breaker, keeping the protection of the UHG.
Also want to mention that these 150A MRBF fuses have no 'intelligence', but the regulator is the intelligence in this case, and my 600A batteries do have a built in BMS for other protections.
Very good explanation- and apologies for pointing out the water issue- yes they were in a bad place before, just saw that trap overhead and worried a little...
So do you think a 250A breaker is sufficient? I am dumping the roof AC for a Mabru 12V one, that uses about 1/3 the amps/watts as the Mach unit. Local custom van outfit has me all scheduled for the replacement in the spring.
The Coleman-Mach unit is too loud and inefficient.
Thanks for pointing this out!!
Mark hello and thanks for the reply - Sounds like you have everything in order and a good sized system. If you are running a 13.5 or 15k AC unit on your lithium, a 300 amp fuse might be a better choice since 12 volt systems generate high amperage and massive heat in summer when running an AC unit. Therefore, you have additional current used to heat all the cables, terminals and inverter from the high amperage plus voltage drop.
For this reason, I only use 51 volt systems in RV's when the an AC is used. As an example, if you are running an AC unit and a cook-top using 2400 watts, if the lithium system is using 51 volts, it only generates 50 amps to satisfy the loads. This same AC and cook-top with a 12 volt lithium system, generates 200 amps, 75% more amperage. Plus with 12 volts, you now have heat from the high amperage which consumes additional current from the batteries.
I included a chart below I made for a video to better explain the amperage verses voltage. There are other 48/51 volt advantages, such as you can have longer runs on your cable, have batteries on the other side of the coach, use smaller wire. The best part is virtually little to no heat and losses.
Mark hello and thanks for the reply - Sounds like you have everything in order and a good sized system. If you are running a 13.5 or 15k AC unit on your lithium, a 300 amp fuse might be a better choice since 12 volt systems generate high amperage and massive heat in summer when running an AC unit. Therefore, you have additional current used to heat all the cables, terminals and inverter from the high amperage plus voltage drop.
For this reason, I only use 51 volt systems in RV's when the an AC is used. As an example, if you are running an AC unit and a cook-top using 2400 watts, if the lithium system is using 51 volts, it only generates 50 amps to satisfy the loads. This same AC and cook-top with a 12 volt lithium system, generates 200 amps, 75% more amperage. Plus with 12 volts, you now have heat from the high amperage which consumes additional current from the batteries.
I included a chart below I made for a video to better explain the amperage verses voltage. There are other 48/51 volt advantages, such as you can have longer runs on your cable, have batteries on the other side of the coach, use smaller wire. The best part is virtually little to no heat and losses.
Regards Mike
Very clever use of the watts formula- I think I will be ok with 250A breaker for two reasons- I have two on hand, and the AC draw using the Mabru 12V unit will be about 1/3 that of what I am currently using with the Coleman "powersaver" 11kbtu (700W) unit. Also all my stuff is 12V inside anyways... I would have to change out the Combimaster and solar charge controllers- much more than I had planned.
Worst case is me re-setting the 250A breaker. Then I would bump it up a notch.
Right now I have been on the two 150A MRBF ones atop each battery, which admittedly seemed undersized when I moved everything up inside, and they have not blown yet. When I tested the new batteries, charging was the only time I noticed some heat on the B- cable. I ran the AC for 7 hours straight, no issues.
My cable runs are less than 30" in my situation to the buss bar and 80" to the combimaster. (less than they were before) The temps do not get very high from my tests.
Mark thanks for the reply - Absolutely, the lower the fuse, the safer the system is. With your short cable runs you should be fine.
For the past year or so, I've been working on my own version of an "Over-Night AC system for RV's where you can cool a bedroom or small RV. I use small 4000 btu AC unit. The unit only draws 350 watts so even a small lithium or AGM battery set would run it all night. I've installed this system in two coaches so far. I have one in my Renegade Super C. At night, I close off the rear bedroom 8'x10' and the AC cools the bedroom fine.
I recently finished an installation in a Airstream. I named the system "Li-PAC" for lithium powered AC. This is a great system for small RV's, I'll be installing one in my Compass 24 KB in the near future. I included a short video if you would like to see the install - Enjoy
Mark thanks for the reply - Absolutely, the lower the fuse, the safer the system is. With your short cable runs you should be fine.
For the past year or so, I've been working on my own version of an "Over-Night AC system for RV's where you can cool a bedroom or small RV. I use small 4000 btu AC unit. The unit only draws 350 watts so even a small lithium or AGM battery set would run it all night. I've installed this system in two coaches so far. I have one in my Renegade Super C. At night, I close off the rear bedroom 8'x10' and the AC cools the bedroom fine.
I recently finished an installation in a Airstream. I named the system "Li-PAC" for lithium powered AC. This is a great system for small RV's, I'll be installing one in my Compass 24 KB in the near future. I included a short video if you would like to see the install - Enjoy
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