I am a relative beginner to the solar world but am enjoying the learning process a great deal. I have a question about using several lithium iron phosphate batteries to expand the capacity of my solar power stations (specifically 12V batteries to charge Bluetti series power stations). I have used many of the Bluetti Power stations (all sizes) in the past so I am fairly familiar with them and have been happy with their operation so far. My questions revolve around the idea that I will be taking several of my power stations to a remote location for a project and there will be several large 12V lithium iron phosphate batteries already on site so I was thinking that I might utilize those batteries to expand the capacity of the Bluetti stations. I would like to be able to charge the power stations at a relatively decent rate of charge directly from the 12V batteries (DC to DC for best efficiency). I have seen videos where this was done using a boost converter (12V up to 36V) from 12V batteries and the charge rate on the bigger Bluetti stations was pretty good (exceeding 400 watts). In an attempt to do this sort of thing, I have several questions:
Does anyone make a quality boost converter that would step up 12V to 24V (or better yet 36V) that is plug and play for Bluetti stations? (I guess this converter would ideally have pre-made leads to go to the battery and then leads that go to MC4 connectors to use for the stations since there are different plug types for different size stations)
Is a fuse needed with the boost converter?
This may sound silly but how do I charge the batteries? I am only familiar with charging the power stations and Bluetti makes that very easy to do. Do I need specific equipment (charger) to plug into an AC wall outlet to charge the 12V batteries? Is there a plug and play setup that would allow me to charge the batteries with solar panels (specifically two or three of the Bluetti PV420 panels in series)? I have done some research and think I would at least need a solar charge controller but not sure about what size I would need or if there are units that have cables already made where I could plug in MC4 connectors directly to the controller.
Is there a plug and play device that I could use to monitor the State of Charge of the battery while it is being charged (again, I was spoiled by Bluetti Power stations already having an SOC meter built in so I am not familiar with how to monitor this on a battery)?
I have also looked at inverters in case I wanted to run AC directly off the battery and I was not sure if you could/should hook them directly to the battery (is a fuse or other equipment needed to be inline with the inverter)? This is not quite as important as I plan on mainly using the Bluetti power station inverters for AC applications and would mainly use the batteries for additional storage capacity but it might be nice to have the option.
Thanks in advance for any assistance as I know others may have already done this and probably have answers to some or all of the questions above.
If you are using several 12 volt batteries then you can connect them in series to get 24,36 or 48 volts or more if you have additional batteries. No step up converter required. You would need to purchase a stand alone charger capable of the output voltage of your combined batteries or you would have to charge each separately at 12 volts. I like Victron brand equipment and they have all the items you are asking about in a wide variety of capacities.
Thanks for the reply. You pointed out the obvious answer to stepping up the voltage that somehow escaped me. I guess I was thinking that I should get a boost converter just in case the batteries are not all the same size/type (not sure what exactly I will have at my disposal yet). Follow-up question to what you suggested - If I have several batteries that are the same voltage but different capacities, is it safe to combine them (ex. combine a 12V 50 Ah battery in series with a 12V 150 Ah battery to get a 24V 200 Ah combination)?
Regarding the other components, I have heard from several others that Victron is the way to go. I assume that since the Voc on the Bluetti PV420 panels is around 44V, I would need to get one of the larger Victron charge controllers to charge with multiple PV420 panels in series (keeping the amps down so not in parallel). I would probably also need a shunt to be able to tell the State of Charge of the battery unless the charge controller does that also.
Regarding the other side of the charging setup (power from batteries to Bluetti stations), does Bluetti sell pre-made cables that have clamps on one side and the connector to different stations on the other end (ex. clamps to go on the posts of the battery to XT60 connector on the other end). I know I will at least have access to a Bluetti AC500 and AC200 Max. If I go with an inverter, say a Samlex or Victron, is there a need to have a fuse between the battery and inverter (I have seen it done but was not sure if it was necessary). Thanks again for all of the help that you have already provided as it was a solution I just overlooked.
It is not recommended to connect batteries in series that are not the same type and capacity. I am not aware of any Bluetti cables that have clamps on one end and an XT60 on the other. I personally would not use clamps but would install ring terminals for a more secure connection. I would always place a fuse between a battery and an inverter for protection.
Thank you for the helpful information. It has helped me out a lot already. I am learning more about the conditions that I may be operating in and it has given me a bit better idea of what I would need to use batteries to supplement my Bluetti power stations. The batteries are the only thing available at the moment so it looks like I will need to purchase a charger, probably a battery monitor, and a solar controller (if wanting to charge the batteries with solar and not using the solar controller in the Bluetti stations), cables with ring terminals to make connections between the batteries, and a cable with positive and negative ring terminals on one end and an XT90 connector on the other end (for charging the Bluetti from the batteries). I would also need to get a cable with a fuse or circuit breaker with ring terminals on both ends and an inverter if I wanted to use AC directly from the batteries for some reason. It sounds like I will have access to at least one but probably several 200Ah 12.8V batteries so I am thinking that I could use them by themselves or connect them up in series to get either 24V (for the smaller Bluetti stations) or 36V (for the larger stations). I know that you mentioned you prefer Victron equipment and I have seen lots of good reviews for their stuff - Do you have a specific model of Victron charger that you recommend? I was thinking that one of the battery monitors with bluetooth would be nice - Do you have a specific model that you recommend or have experience with? I looked at the Victron solar charge controllers and saw one that I really liked (with a good Voc rating) but it was a bit pricey at around $800.00 (that might be worth the price though) - Do you have a model that you recommend for charging with at least 800 to 900 watts of solar (thinking 2 to 3 Bluetti PV420 panels in series)? I can probably find the cable sets online as I don’t have the tools to make them myself - Do you think 10AWG wire would be sufficient? Also, could you recommend a circuit breaker that I could put inline with the inverter (I have used Samlex inverters before so I would probably go with one of those)? I apologize in advance for all of the questions but I am just trying to see if I can get a lot of these items in advance so that I will be ready to go when I have access to the batteries. Thanks again for all of the help as I have learned a lot just from this thread alone.