hwy17
Anti-Solar Enthusiast
Yeah I was relieved when I saw that. I had been trying to look for a name brand Littlefuse before I gave up and "settled" for a blue sea.
DIY Solar Plans - Is this a safe setup?
- Thread starter Solar User
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Solar User
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Thanks. That is great information. I guess when I looked at how beefy the Class T fuse was, I just assumed that it would not work well connected directly to the battery post and/or busbar and that I would need to spend the money for the case. I like the idea of simply connecting the fuse directly to the battery but I am always thinking of strain relief for the wires and connections. This thread alone has been so helpful and it has got me thinking of several different issues now.
I thought about setting up several sets of the batteries (two in series) to be 24V "packs" and going that way so that I could use smaller fuses and smaller wires but when I started looking at the efficiency of the system when at idle (no load), it looked like it would be less efficient (24V inverter would use slightly more wattage to sit idle than 12V). I also thought it would be nice to power some 12V loads (laptops, etc.) off the system and I guess that would require a step down converter if I was running a 24V system.
If I do decide to go to a 2000 Watt inverter, do I still need to use a resistor to charge it if I have the on/off switch (planning to turn the system on and off relatively frequently)? If so, where do I find one?
Thanks again to everybody for the good discussion.
I thought about setting up several sets of the batteries (two in series) to be 24V "packs" and going that way so that I could use smaller fuses and smaller wires but when I started looking at the efficiency of the system when at idle (no load), it looked like it would be less efficient (24V inverter would use slightly more wattage to sit idle than 12V). I also thought it would be nice to power some 12V loads (laptops, etc.) off the system and I guess that would require a step down converter if I was running a 24V system.
If I do decide to go to a 2000 Watt inverter, do I still need to use a resistor to charge it if I have the on/off switch (planning to turn the system on and off relatively frequently)? If so, where do I find one?
Thanks again to everybody for the good discussion.
lot of people seem to go bus bar -> fuse -> bus bar for the connections of the 8 to 9th battery. (assuming you have 16 cells on the battery)
This way even if you short terminals on the battery, the fuse breaks at the other end of the battery
& yea higher voltage tends to be more efficient
no clue what this means lol
Hedges
I See Electromagnetic Fields!
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If the inverter keeps its input capacitors connected to battery, and you only switch on/off the transistor circuit, no need for another precharge.
My inverters have pushbutton start/stop, but also a breaker that disconnects battery input. So precharge would be needed for lithium.
My inverters have pushbutton start/stop, but also a breaker that disconnects battery input. So precharge would be needed for lithium.
Hedges
I See Electromagnetic Fields!
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Oh yeah!
In fact, when I plug in a modern toaster, it sparks.
Anything with switch mode power supply; there are capacitors to be charged up. That is usually relatively small. Can trip a breaker for some AC powered equipment.
People here have blown class T fuses or welded contactors simply connecting lithium battery to inverter. Mine use AGM, higher internal resistance so not as much of a problem.
Likely all the "supported" batteries have a soft-start (precharge) function. But the mix-n-match assembly DIY people do has often had a problem.
In fact, when I plug in a modern toaster, it sparks.
Anything with switch mode power supply; there are capacitors to be charged up. That is usually relatively small. Can trip a breaker for some AC powered equipment.
People here have blown class T fuses or welded contactors simply connecting lithium battery to inverter. Mine use AGM, higher internal resistance so not as much of a problem.
Likely all the "supported" batteries have a soft-start (precharge) function. But the mix-n-match assembly DIY people do has often had a problem.
Solar User
New Member
I apologize for not being clear in my earlier post but I think you figured it out. I was wondering about the resistor to pre-charge inverter capacitors because from what I have read, it sounds like just attaching the battery to the inverter and causing it to spark is, at best, not good practice and, at worst, could cause explosive problems. My plan has a separate on/off switch inline right after the initial fuse from the battery (I put this in place so that I could switch the system on and off in order to reduce parasitic draw when it is not in use). I guess I was wondering if having this switch turned off and then back on would have the same problems as letting it "spark" every time without a switch inline (due to the same inrush of current). I have seen resistors used to pre-charge capacitors but just not sure if that would be necessary every time you switch the system on and off. I would hate to put undue wear and tear on the system and/or the inverter by just switching it on and off all of the time (I have gotten used to the manufactured units that you can turn on and off at will since I don't have full time solar right now and only put out panels when convenient).
Solar User
New Member
Thanks for the clarification. I guess that technically means that this will not be a very convenient setup for turning off and on on a regular basis but would be ok for longer term use (thinking I would need to detach the inverter from the bus bar and use a precharge resistor every time I wanted to turn the system back on after shutting it down (maybe on a daily basis).
Another follow on question that I have since come up with - If I used this same setup but decided that I wanted to temporarily remove the 2000 watt inverter and attach a 300 watt inverter for certain applications, would I still need a Class T fuse inline between the busbar and the inverter or would I be able to use another type of fuse? It sounds to me like I might still need a Class T fuse due to the type of battery I am using but I think Blue Sea Systems only has Class T fuses that start at 110 amps which would be way more than I would need for a smaller inverter with smaller wiring.
Another follow on question that I have since come up with - If I used this same setup but decided that I wanted to temporarily remove the 2000 watt inverter and attach a 300 watt inverter for certain applications, would I still need a Class T fuse inline between the busbar and the inverter or would I be able to use another type of fuse? It sounds to me like I might still need a Class T fuse due to the type of battery I am using but I think Blue Sea Systems only has Class T fuses that start at 110 amps which would be way more than I would need for a smaller inverter with smaller wiring.
Hedges
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Fuse AIC rating based on battery short-circuit capability. Amps rating based one wire gauge.
Smaller fuse would be good for smaller inverter, maybe it protects the inverter but it is there to protect the wires (and battery).
You can get as rotary switch Off-On-On, connect pre-charge resistor to first "On" position, maybe a light a cross the resistor. Then it is convenient. The following has the functionality, but says 32V max. Difficult to find switches rated 60V, for use with 48V battery.
www.bluesea.com
Smaller fuse would be good for smaller inverter, maybe it protects the inverter but it is there to protect the wires (and battery).
You can get as rotary switch Off-On-On, connect pre-charge resistor to first "On" position, maybe a light a cross the resistor. Then it is convenient. The following has the functionality, but says 32V max. Difficult to find switches rated 60V, for use with 48V battery.
m-Series Mini Dual Circuit Plus™ Battery Switch - Black - Blue Sea Systems
300 Amps continuous rating for outboards and small gasoline or diesel engines.
www.bluesea.com
Solar User
New Member
Thanks for the explanation. I think I like your idea. In my diagram, I would be adding another circuit from the on-on-off switch that would bypass the busbar, go through a resistor, and connect directly to the inverter. To turn on, I would switch to the resistor circuit first (for a short period of time to charge the capacitors) and then switch to the regular "on" circuit.
Solar User
New Member
Regarding a Class T fuse for 40A (to be used off the busbar for a 300W inverter), would this work for the lithium batteries?
Littelfuse Jlln040 Fuse, Fast Acting, 40A, Jlln Series, 300Vac, 160Vdc, 7/8" L | eBay
Thuemling Lfs-Firetestkit Fire Truck Pump Test Kit. & Recepticles. Electrical Outlets. Light Industrial. and Enclosures. Electrical Boxes. General Purpose. & Industrial.
www.ebay.com
Solar User
New Member
Thanks for the assistance. After learning all about grounding and AIC from this discussion, I was just thinking that I should get an appropriate fuse in case I decide to wire up the smaller inverter I have to the system. This discussion has been very educational.
Solar User
New Member
I have seen many people running the 12V inverters without pre charging (usually 2000 watts or less) so I was wondering about it but I am going to keep some resistors handy and do it anyway just to be on the safe side.
Solar User
New Member
I was having a discussion regarding battery wiring today and it prompted several more thoughts/questions?
Regarding batteries, if you wire two 12V batteries in series to boost the voltage to 24V, is it necessary to put a fuse inline with the wire that is connecting the positive and negative posts of the two batteries? Someone mentioned having a fuse inline for every single battery in a pack but I had not heard that before.
Speaking of fuses, I saw where someone else was saying that Class T fuses should never be bolted to batteries or bus bars because they can easily break (they indicated that you really need fuse holders for Class T fuses). Is this correct? I initially planned to bolt on the Class T fuses directly to the battery and bus bar (taking care to reduce strain on the connections).
Regarding batteries, if you wire two 12V batteries in series to boost the voltage to 24V, is it necessary to put a fuse inline with the wire that is connecting the positive and negative posts of the two batteries? Someone mentioned having a fuse inline for every single battery in a pack but I had not heard that before.
Speaking of fuses, I saw where someone else was saying that Class T fuses should never be bolted to batteries or bus bars because they can easily break (they indicated that you really need fuse holders for Class T fuses). Is this correct? I initially planned to bolt on the Class T fuses directly to the battery and bus bar (taking care to reduce strain on the connections).
Solar User
New Member
Hedges
I See Electromagnetic Fields!
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McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
Class T:
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
(link for sockets on that page looks like wrong style; these don't have blades.)
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