diy solar

diy solar

Multiple battery

HRTKD said:
That shouldn't be necessary. If you were putting the four batteries in series, then balancers for the four batteries might be called for. But your four batteries will be in parallel, so there is no need for a balancer. A periodic check to see what each battery is at (voltage, state of charge, etc) is in order.
Click to expand...

I am happy with this plan. I will forget the balancer for the 4 batteries
 
smoothJoey said:
Looks good.
Click to expand...
Here are the adjustable parameters-
H48ea4c214b4b43649aa7a8ad929e663dk.jpg
 
Thanks for all of the help guys. This subject has been on the back of my mind and bugging me for a long time.
Multiple batteries seem simple now. Using multiple batteries solve more problems than they create.
When I start choosing the actual parts, I will check in to be sure they will work.
Is there a reason I would want to use shunts? I see the BMS shows a lot of info but I don't know if the shunt does something that I need.
 
ArthurEld said:
Thanks for all of the help guys. This subject has been on the back of my mind and bugging me for a long time.
Multiple batteries seem simple now. Using multiple batteries solve more problems than they create.
When I start choosing the actual parts, I will check in to be sure they will work.
Is there a reason I would want to use shunts? I see the BMS shows a lot of info but I don't know if the shunt does something that I need.
Click to expand...
Having one shunt to show the aggregated current is a good idea.
I think it's ok to use the bms to monitor the individual batteries.
 
System example using mine as the example.

I run a Midnite Solar SCC with a WizBandJr attached to its 500A/50mv Shunt in teh E-Panel. The Wizbang interfaces with the Midnite SCC and the firmware/software to provide whole system stats for charging, discharging & battery bank status, DOD/SOC overall. It provides a good general overview of what the system is doing and how well. The software allows for active monitoring by the SCC also & stores the data which can be retrieved into a spreadsheet or other.

Each of my LFP packs has it's own Shunt. This is because I am using a Chargery BMS that wants the shunt for it's own measurements and monitoring for the particular pack. That provides that full stats as to what is going in/out of that pack and only for it's own pack. Each of the four Battery Packs in the bank, have the ability to be fully independent of the others.

Some BMS' like the FET based ones can sometimes use an Internal Shunt and others may use a Coulomb Meter while others may use a Hall Pickup sensor. They all work but do behave a bit differently and their capacty handling is often quite limited.
 
Here is how the fault tolerance will work from a charging perspective.

You have 4 batteries in parallel.
There is a 125 amp fuse on each battery for over-current protection.
The setup will tolerate 2 batteries offline without the others falling like dominoes.

4x 280 amp hour batteries charging at .2c = 224 amps
4 batteries = 56 amps per battery
3 batteries = 75 amps per battery
2 batteries = 112 amps per battery, bms may trip
1 batteries = 224 amps per battery, bms and/or fuse should trip

That is a pretty robust setup.
 
smoothJoey said:
Here is how the fault tolerance will work from a charging perspective.

You have 4 batteries in parallel.
There is a 125 amp fuse on each battery for over-current protection.
The setup will tolerate 2 batteries offline without the others falling like dominoes.

4x 280 amp hour batteries charging at .2c = 224 amps
4 batteries = 56 amps per battery
3 batteries = 75 amps per battery
2 batteries = 112 amps per battery, bms may trip
1 batteries = 224 amps per battery, bms and/or fuse should trip

That is a pretty robust setup.
Click to expand...
I am planning to set my batteries up right so the batteries never get shut down by the BMS. Something would have to be seriously wrong for 2 batteries to shut themselves down. But I should be safe no matter what.

Thanks again, this is awesome.

I ordered the 200A BMS with 2A active balance. But it will be months before I have my system up and running.
 
ArthurEld said:
I am planning to set my batteries up right so the batteries never get shut down by the BMS. Something would have to be seriously wrong for 2 batteries to shut themselves down.
Click to expand...
Yes very unlikely.
You could have 1 offline for maintenance and 1 of the remaining 3 could decide to have a bad hair day.
Still not likely but could happen.
 
HRTKD said:
ArthurEld, the way I "parallel" connected my two batteries is that I ran 2/0 cables from each battery to the necessary common connection points. In the picture below, you can see that each battery's negative goes to the shunt and each battery's positive goes to the fuse. In my case, I wanted each battery to be independent, with no connection between the batteries.

20200903_190817-jpg.21889


Since you have four batteries to connect I would use a bus bar between the batteries and the common connection points. I say this because there aren't enough threads on the shunt or fuse block to handle four stacked lugs.
Click to expand...
Basically the same way I set up my 280 EVE's but used 5/8 butcher board with AL. angle's midway on sides for stiffness and lifting handles. To cover the all thread I used PEX tubbing. Comes in red white or blue. It also compresses a little. I am still amazed at those things. First I ran my old dome tic 12,000 AC and was pulling continuous 1300 watts, switched to a mini split and average about 450. That's a nice tidy system you have. Are you still running the original converter for charging? I have a inteli-charger but didn't hook it up I have my doubts about its li po capabilities. My aims low frequency inverter has a 80 amp charger but am questioning my 3500 watt inverter generators ability to supply the amps it would need
 
doppler said:
Basically the same way I set up my 280 EVE's but used 5/8 butcher board with AL. angle's midway on sides for stiffness and lifting handles. To cover the all thread I used PEX tubbing. Comes in red white or blue. It also compresses a little. I am still amazed at those things. First I ran my old dome tic 12,000 AC and was pulling continuous 1300 watts, switched to a mini split and average about 450. That's a nice tidy system you have. Are you still running the original converter for charging? I have a inteli-charger but didn't hook it up I have my doubts about its li po capabilities. My aims low frequency inverter has a 80 amp charger but am questioning my 3500 watt inverter generators ability to supply the amps it would need
Click to expand...

No, I installed a converter with a LiFePO4 charging profile.
 
ArthurEld said:
Your system is nice HRTKD. It was an excellent starting example for my battery setup.
Click to expand...

Thanks!

I tested the system a bit today. I ran a 500 watt 120vac space heater off of my 1000 watt inverter for an hour. The two rooftop solar panels were contributing about 375 watts (it was a bit overcast/smokey) and the batteries picked up the rest. Every so often I opened the BMS app and looked at the cells to see how closely they stayed together. Even though the batteries weren't getting worked hard, I was impressed. Whenever I checked the cells were within .005 v of each other.

The real test comes at the end of this month when I boondock for ten days.
 
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