I built a small 24v system based on Will's plans from a few years ago: 8 100w solar panels, epever solar controller, giandel 2000w inverter and four battle born 12v/100 Ah batteries wired series/parallel to yield 24v. . I'm using it off grid in a small cabin. Here's my problem: even with a very small power draw, the batteries have shut down twice. Battle Born says I have to charge them up individually so that they are balanced. I did that once, but they just shut down again. It appears that the individual battery BMS is shutting down two of the four batteries and I can't get the system to turn back on to charge using solar. Of course I can go charge them again, but it feels as if I need a real BMS to keep the batteries working right. Is there a BMS that would work for 12v batteries like these? Am I missing something? It is possible, but surprising, that the system would shut down due to low sun in these dark winter days. But why do the batteries shut down so that I have to recharge every time there is not enough power?
Small 24v System Shutting Down. Help!
- Thread starter papasleep
- Start date
it is best to have 24v batteries in a 24v system for this very reason (rather than two 12v batteries in series). Also it is best to have Bluetooth (or some other way) to look at the cell’s charging status to know if cells have drifted high and low.(which battle born does not provide).
There are two different problems that could cause shutdown- either the battery was out of power or an individual cell is unbalanced enough to go too low.
Do you have a shunt (like a Smartshunt or BMV712 on your system- so you know when the battery is getting low? If not you need that.
In a 12v battery (or any battery) Cells will naturally drift - the bms’s job is to rebalance those cells. If it sounds like you may have imbalances in your battery. You probably need to adjust your system so you spend more time in absorbing mode - to give the bms time to burn off power from the high cells.
If you think cell imbalances are the issue then, You need to slowly charge each 12v battery until it cuts off, then if it didn’t cut-off very near the the top of the charge voltage- discharge the battery a bit (probably 15%) and repeat - but maybe charge slower. You need to give time for the bms to work. I would keep repeating until the cutoff is at least 14.4v. You need to do this for each battery, then readjust your system so it spends more time in absorbing mode.
If you have not already gotten a shunt - get the BMV712 and then setup the mid-point. This way you can see if the first two batteries are running at a higher voltage than the second two. Victron also makes a battery balancer to help fix mid-point differences.
There are two different problems that could cause shutdown- either the battery was out of power or an individual cell is unbalanced enough to go too low.
Do you have a shunt (like a Smartshunt or BMV712 on your system- so you know when the battery is getting low? If not you need that.
In a 12v battery (or any battery) Cells will naturally drift - the bms’s job is to rebalance those cells. If it sounds like you may have imbalances in your battery. You probably need to adjust your system so you spend more time in absorbing mode - to give the bms time to burn off power from the high cells.
If you think cell imbalances are the issue then, You need to slowly charge each 12v battery until it cuts off, then if it didn’t cut-off very near the the top of the charge voltage- discharge the battery a bit (probably 15%) and repeat - but maybe charge slower. You need to give time for the bms to work. I would keep repeating until the cutoff is at least 14.4v. You need to do this for each battery, then readjust your system so it spends more time in absorbing mode.
If you have not already gotten a shunt - get the BMV712 and then setup the mid-point. This way you can see if the first two batteries are running at a higher voltage than the second two. Victron also makes a battery balancer to help fix mid-point differences.
Right now, with the batteries shut down, I don't see any SOC info. There is a monitor on the epever charge controller, and fully charged I do see 27v+. Let's assume that I have too much load (this last time I had virtually no load). Is it right that batteries shut down completely and need to be charged individually? Is there any way to take ALL the load off the system and charge with solar? Right now I have full sun, but can't reset the inverter or solar controller.
To wake up a battery it needs a charge - it sounds like your SCC will not provide a charge if the battery is not awake.
If you feel you ran your batteries low - one item you could add to your system is a Victron smart battery protect (BP-65). This will shut down the loads as they get low at ____v (user setable). That way the loads shutdown before the bms dies so you don’t have to reawaken the bms’s.
But you need to carefully check out your equipment and setup to see if that can work - (cannot go to any charger).
If you feel you ran your batteries low - one item you could add to your system is a Victron smart battery protect (BP-65). This will shut down the loads as they get low at ____v (user setable). That way the loads shutdown before the bms dies so you don’t have to reawaken the bms’s.
But you need to carefully check out your equipment and setup to see if that can work - (cannot go to any charger).
Leeds
Solar Enthusiast
- Joined
- Jul 7, 2022
- Messages
- 179
Charge each battery independently and fully and let them sit for at least an hour after the last one is removed from the charger.
Measure the voltage of each battery and make sure that each one is within a tenth of a volt of 13.6 volts.
Then and only then can you stack them back into your 2p2s bank.
The other thing that comes to mind is that your 2000w inverter probably draws 45 watts of power around the clock. That adds up to about 1/3 of the energy your panels likely deliver over a good 24 hour day. Turning it off when it's not in use would help a lot.
Measure the voltage of each battery and make sure that each one is within a tenth of a volt of 13.6 volts.
Then and only then can you stack them back into your 2p2s bank.
The other thing that comes to mind is that your 2000w inverter probably draws 45 watts of power around the clock. That adds up to about 1/3 of the energy your panels likely deliver over a good 24 hour day. Turning it off when it's not in use would help a lot.
SunDave
Solar Enthusiast
Hi. I guess that depends how they died. If they just drained down over a long period of time, and all 4 are low, even the ones that didn't get shut down, then you may just have larger output than input.
If you are not getting much sun, and have the constant draw from the idle of the inverter and anything attached, you may just be using more power than you are getting.
Interestingly, I have a small cabin with 800 watts of panels as well. I don't have as much battery though. I keep a 24v marine style shut off switch between the batteries and the inverter and all other loads. That when I am not there, only the charge controller and panels are hooked up to the battery. I know if I left anything plugged in during the winter months it would run the batteries flat in a matter of days. Depends how much sun you get of course.
One other trick I can share is that I run some Pyle brand 24 to 12 volt converters, then run the lights, ceiling fan, and furnace fan, etc. on 12v. The nice thing about having the step down from 24 to 12 is that the lights are always the same brightness, even as the AGM batteries discharge.
If you are not getting much sun, and have the constant draw from the idle of the inverter and anything attached, you may just be using more power than you are getting.
Interestingly, I have a small cabin with 800 watts of panels as well. I don't have as much battery though. I keep a 24v marine style shut off switch between the batteries and the inverter and all other loads. That when I am not there, only the charge controller and panels are hooked up to the battery. I know if I left anything plugged in during the winter months it would run the batteries flat in a matter of days. Depends how much sun you get of course.
One other trick I can share is that I run some Pyle brand 24 to 12 volt converters, then run the lights, ceiling fan, and furnace fan, etc. on 12v. The nice thing about having the step down from 24 to 12 is that the lights are always the same brightness, even as the AGM batteries discharge.
Q-Dog
¯\_(ツ)_/¯
Each of your batteries already has a BMS built in. But none of the batteries can talk to each other. So, when the batteries get out of balance with each other they don't know it.
BattleBorn used to suggest if their batteries are run in series they need to occasionally be broken down and fully charged. It is hard to do this if you are fully solar and don't have regular access to the grid or a generator and a separate charger. This is one reason why a 24 volt system might want to use 24 volt batteries.
I am 24 volt with 4 batteries in parallel and each battery has a disconnect so I can take any of them offline without shutting down the entire system. Can you shut down half of your pack and balance them while the other half keeps your system running?
mikefitz
Solar Wizard
- Joined
- May 28, 2020
- Messages
- 2,979
9. Midpoint voltage monitoring
Battery Balancer - Victron Energy
Equalize the state of charge of two series connected 12V batteries using the Battery Balancer. Find a Victron Energy dealer near you.
Thanks. Much here to take in, but I think the problem does lie here. No, I don't have a shunt. Will look into that now.
Have not heard that about the inverter drawing power. Thanks. Very helpful.
Get the Victron Bmv712 shunt. Yes it will let you know about the state of charge of your batteries - but you can also set it up for the mid-point of your battery- so you know if they are getting out of balance.
The thing the shunt really helped me with is know how much power different things use- for example, we have one light that uses very little power - but does an ok job of lighting our kitchen- so we always use that one and only use the really bright - but power hog light when we really need it.
Good Luck
The thing the shunt really helped me with is know how much power different things use- for example, we have one light that uses very little power - but does an ok job of lighting our kitchen- so we always use that one and only use the really bright - but power hog light when we really need it.
Good Luck
IMO a SCC is not the right tool to verify SOC.
As other suggested a nice victron smart shunt would help you keep track of your system and battery SOC
Also a victron SCC can charge a completely dead battery.
If you need to wake up the batteries a simple FLA battery (small lawn mower unit) quickly touched to the terminals will wake them up.
Parasitic loads are the death of a small system.
When they run 24/7 it adds up. If you’re running a fridge or something that always needs to be running its kinda impossible to escape.
If your Gona get a shunt ,spend the few extra dollars and get the Victron BMV - 712… you will be glad you did..
Similar threads
