BMS capacity question

Stephen C

New Member
I’m building a Lifepo4 battery to replace a FLA battery bank (eight Trojan T105 clones) at an off-grid cabin. I’m ordering eight 280Ah Lifepo4 cells (to put in series for 24V), and was planning on ordering an Overkill Solar 8s 100A BMS. I have an old Trace 24V 2400w inverter. (I’m slowly upgrading the system and the inverter will be replaced in 1-3 years, likely with another 2400W inverter, since that handles my needs just fine.) My question is the size of the BMS. Is a 100A BMS adequate for a 24V 2400W inverter, or do I need to factor in some margin for error with a larger BMS? I’ve hit the high current cut-off with the inverter (2400W) only one or two times over the past 10 years. If you think I should have a higher capacity BMS, can you please suggest another smart BMS with low temp cut-off. I don’t think it matters, but the system is powered by 360W of solar panels (soon to be upgraded to about 800W), with a Victron 150V/35A charge controller. The site has cold winters, and although the Victron has low temp cut off, I’d feel better if the BMS had it as well (which is one of the reasons I like the Overkill Solar BMS). Thanks in advance for your advice.
 

Stepandwolf

Solar Addict
I’m building a Lifepo4 battery to replace a FLA battery bank (eight Trojan T105 clones) at an off-grid cabin. I’m ordering eight 280Ah Lifepo4 cells (to put in series for 24V), and was planning on ordering an Overkill Solar 8s 100A BMS. I have an old Trace 24V 2400w inverter. (I’m slowly upgrading the system and the inverter will be replaced in 1-3 years, likely with another 2400W inverter, since that handles my needs just fine.) My question is the size of the BMS. Is a 100A BMS adequate for a 24V 2400W inverter, or do I need to factor in some margin for error with a larger BMS? I’ve hit the high current cut-off with the inverter (2400W) only one or two times over the past 10 years. If you think I should have a higher capacity BMS, can you please suggest another smart BMS with low temp cut-off. I don’t think it matters, but the system is powered by 360W of solar panels (soon to be upgraded to about 800W), with a Victron 150V/35A charge controller. The site has cold winters, and although the Victron has low temp cut off, I’d feel better if the BMS had it as well (which is one of the reasons I like the Overkill Solar BMS). Thanks in advance for your advice.
Others here know better than me but I would want more amperage than that model. The maker, JBD, offers a higher amperage model if you want something like the Overkill.
 

Simi 60

Solar Enthusiast
This was the one suggested by Amy and the JbD rep


 

Stepandwolf

Solar Addict
This was the one suggested by Amy and the JbD rep


That model is 12-18S, not 8s.
 

smoothJoey

Ooga Booga!
I have an old Trace 24V 2400w inverter.
Is it a low frequency inverter or high?
A 2400 watt high frequency inverter would weigh less than 20 pounds.
A 2400 watt Low frequency inverter would weigh more than 40 pounds.

For high frequency
2400 ac watts / .85 conversion factor / 24 volts low cutoff = 117.647058824 service amps

For low frequency
2400 ac watts * 1.5 low frequency factor / 24 volts low cutoff = 150 service amps
 
Last edited:

Stephen C

New Member
Thanks. It's a low frequency inverter. I didn't think of the implications until you mentioned it. Although, either way, it sounds like a I need a larger capacity BMS. I just looked at the larger capacity JBD BMS's, although quite frankly I can't figure out the different models and which would be right. If anyone can point me in the right direction for a 150A or 200A 8s JBD BMS with bluetooth, I'd be grateful. Or another suitable brand for my situation. I'm buying the cells from Amy, so I've reached out to her as well to see what she carries or can recommend. Many thanks.
 

chrisski

Photon Sorcerer
I’m not so much a fan of a larger BMS to do the jump to 200 amp, but for my system got 16 of those cells, for two batteries with 8s, and have a 100 amp BMS for each battery. In my case I have a 3000 watt inverter I will install for 24 volts, but will rarely go that high.
 

Simi 60

Solar Enthusiast
That model is 12-18S, not 8s.
a few posts further down.........
Well.......I just spoke with the JBD store rep on AB and when asked for an 8s 24v 200amp BMS it was the above model and documentation they sent.

Questioned them about my concerns with the above screenshot and they assured me that it will do 8s 24v 200amp.
 

RichO

New Member
I’m building a Lifepo4 battery to replace a FLA battery bank (eight Trojan T105 clones) at an off-grid cabin. I’m ordering eight 280Ah Lifepo4 cells (to put in series for 24V), and was planning on ordering an Overkill Solar 8s 100A BMS. I have an old Trace 24V 2400w inverter. (I’m slowly upgrading the system and the inverter will be replaced in 1-3 years, likely with another 2400W inverter, since that handles my needs just fine.) My question is the size of the BMS. Is a 100A BMS adequate for a 24V 2400W inverter, or do I need to factor in some margin for error with a larger BMS? I’ve hit the high current cut-off with the inverter (2400W) only one or two times over the past 10 years. If you think I should have a higher capacity BMS, can you please suggest another smart BMS with low temp cut-off. I don’t think it matters, but the system is powered by 360W of solar panels (soon to be upgraded to about 800W), with a Victron 150V/35A charge controller. The site has cold winters, and although the Victron has low temp cut off, I’d feel better if the BMS had it as well (which is one of the reasons I like the Overkill Solar BMS). Thanks in advance for your advice.
My situation was exactly yours...upgrading from t105's, to in my case 230Ah cells. Old Trace 4024 that has worked flawlessly for over 20yrs now. I would suggest a larger bms if upgrading inverter soon. I had to go with the Daly 200ah do to time constraints. Having extra amp capacity at the bms than you think you need is usually a good mistake to make.
 
Top