Squiffy
Forum Member
Over the last few months I have been experimenting with two lifepo4 batteries and victron solar mppt and seperate shunts for both batteries.
One is the go to for general use a 100ah lifepo4 and the other a 200ah lifepo4 for use with my 1500w pure sine cotek inverter, running a 900w microwave and a single portable induction hob ( Not both at the same time ).
I have to say that it has transformed my views on battery power. One of the things it has done is to make me more aware of how to charge them and what equipment I needed for the safe operation of both the microwave and the hob.
I wanted an easy quick way to turn on the inverter so I made up a plug and lead, the 3 pin plug went to the inverter and the lead I put straight into the back one of my mains plug units the inverter was connected straight to the 200ah battery via an 175A mega fuse and a anderson connector, this all worked well, the microwave operated at full chat without a problem and the induction hob worked well to so long as I kept the power down to 1500w on 1800w it still worked well but it was over the rated inverter on 2200w the battery BMS cut out. This was all good. After finishing I'd pull the Anderson plug to isolate the inverter from the battery.
This is when the problems started, as the inverter was unplugged I assumed the the inverter was now isolated from the mains ring, WRONG!! All this ofcourse was being done whilst not on shore power. I then decided to plug into shore power as I have this all setup outside my garage, the Rcd in the garage tripped immediately, hmmmm so even though the inverter was isolated from the battery there was still a confrontation with the front end of the inverter and so tripped the cct.
So I didn't want to have to switch the inverter off and unplug each time, as it was a pain because it was all mounted under the rear bed, plus the fact that having unplugged the lead I now had a 3 pin plug that was live if I was plugged into shore power.
The solution was either an expensive relay to sense the inverter or shore power, plus all the complicated wiring or simple switches so I went for switches.
From the inverter to the back of one of my mains plugs I fitted an AC isolation switch so that I could isolate the inverter from my mains ring cct, then to make things easier I fitted a heavy duty 300amp continuous isolation switch between the inverter and battery instead of the Anderson plug. This meant I could leave the inverter switched on physically but isolated from battery and ring cct and hence could use shore power.
When off grid I switch the battery power on and switch the 240v lead to the back of the socket on and then all my sockets are live, ahhh forgot to mention I also fitted in retrospect a 30ma rcd between the inverter and the 240v isolated switch.
All this is under the bunk and the two switches are mounted to the bunk/side panel. Just have to remember to isolated the inverter after finishing with it. The worst that can happen is it trips the van rcd or the site rcd if I forget.
Now after that I started to think about charging ect, I already had a victron DC-DC fitted which is bluetooth and so decided the get two bluetooth shunts one for each battery again victron so now I can at a glance see the SOC of both battery's and the solar mppt, then started thinking about how to set up the Victron mppt there is a preset setting for lifepo4 batteries but I noticed that if you use these settings the battery is not charging till it gets below the float voltage, so in other words if you start with a fully charged battery say 14.4v and the float voltage is 13.8v most of the day you are using the battery depleting it till it gets 13.8v and then it starts a bulk charge but this could be three quarters way through the day and the sun is just going down over the hills and you only have a half charged battery. So I did some googling and came across several sites on utube that explained a lot of what I was thinking about. This is one guy I quite like he's humorous too.
But there are many utube channels that delve into lithium and solar.
The answer is to set your absorption and float voltages to exactly the same voltage i.e. abs 14.4v float 14.4v this way when the sun is out the solar panels will operate you 12v appliances and charge you battery as well, because lifepo4 batteries do not need absorbtion or float voltages as when they are fully charged the battery bms shuts down the charge so you can't over charge them, but as soon as you draw from the battery and it goes below 14.4v ( Or whatever you decide you want to be your fully charged voltage ) the solar panels kick in to attempt to recharge.
Well sorry for the long winded post but I now find Lithium batteries quite interesting and I would recommend you go onto utube and start digging around about it.
. Phil
One is the go to for general use a 100ah lifepo4 and the other a 200ah lifepo4 for use with my 1500w pure sine cotek inverter, running a 900w microwave and a single portable induction hob ( Not both at the same time ).
I have to say that it has transformed my views on battery power. One of the things it has done is to make me more aware of how to charge them and what equipment I needed for the safe operation of both the microwave and the hob.
I wanted an easy quick way to turn on the inverter so I made up a plug and lead, the 3 pin plug went to the inverter and the lead I put straight into the back one of my mains plug units the inverter was connected straight to the 200ah battery via an 175A mega fuse and a anderson connector, this all worked well, the microwave operated at full chat without a problem and the induction hob worked well to so long as I kept the power down to 1500w on 1800w it still worked well but it was over the rated inverter on 2200w the battery BMS cut out. This was all good. After finishing I'd pull the Anderson plug to isolate the inverter from the battery.
This is when the problems started, as the inverter was unplugged I assumed the the inverter was now isolated from the mains ring, WRONG!! All this ofcourse was being done whilst not on shore power. I then decided to plug into shore power as I have this all setup outside my garage, the Rcd in the garage tripped immediately, hmmmm so even though the inverter was isolated from the battery there was still a confrontation with the front end of the inverter and so tripped the cct.
So I didn't want to have to switch the inverter off and unplug each time, as it was a pain because it was all mounted under the rear bed, plus the fact that having unplugged the lead I now had a 3 pin plug that was live if I was plugged into shore power.
The solution was either an expensive relay to sense the inverter or shore power, plus all the complicated wiring or simple switches so I went for switches.
From the inverter to the back of one of my mains plugs I fitted an AC isolation switch so that I could isolate the inverter from my mains ring cct, then to make things easier I fitted a heavy duty 300amp continuous isolation switch between the inverter and battery instead of the Anderson plug. This meant I could leave the inverter switched on physically but isolated from battery and ring cct and hence could use shore power.
When off grid I switch the battery power on and switch the 240v lead to the back of the socket on and then all my sockets are live, ahhh forgot to mention I also fitted in retrospect a 30ma rcd between the inverter and the 240v isolated switch.
All this is under the bunk and the two switches are mounted to the bunk/side panel. Just have to remember to isolated the inverter after finishing with it. The worst that can happen is it trips the van rcd or the site rcd if I forget.
Now after that I started to think about charging ect, I already had a victron DC-DC fitted which is bluetooth and so decided the get two bluetooth shunts one for each battery again victron so now I can at a glance see the SOC of both battery's and the solar mppt, then started thinking about how to set up the Victron mppt there is a preset setting for lifepo4 batteries but I noticed that if you use these settings the battery is not charging till it gets below the float voltage, so in other words if you start with a fully charged battery say 14.4v and the float voltage is 13.8v most of the day you are using the battery depleting it till it gets 13.8v and then it starts a bulk charge but this could be three quarters way through the day and the sun is just going down over the hills and you only have a half charged battery. So I did some googling and came across several sites on utube that explained a lot of what I was thinking about. This is one guy I quite like he's humorous too.
But there are many utube channels that delve into lithium and solar.
The answer is to set your absorption and float voltages to exactly the same voltage i.e. abs 14.4v float 14.4v this way when the sun is out the solar panels will operate you 12v appliances and charge you battery as well, because lifepo4 batteries do not need absorbtion or float voltages as when they are fully charged the battery bms shuts down the charge so you can't over charge them, but as soon as you draw from the battery and it goes below 14.4v ( Or whatever you decide you want to be your fully charged voltage ) the solar panels kick in to attempt to recharge.
Well sorry for the long winded post but I now find Lithium batteries quite interesting and I would recommend you go onto utube and start digging around about it.
. Phil
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