Multiple banks multiple bms ??

[Gauranga108]

Many other BMS have no problem operating in a parallel situation like this. If Daly is such a poor BMS that it can't do it, then pick a different company.

With regard to your drawing, the monitoring shunt should be placed between the BMS and the negative bus bar. I have both my BMS negative cables going directly into the battery side of my shunt.

There should be a fuse, or fuses,between the battery and the positive bus bar.

@HRTK Just out of curiosity what bms brand do you run with your 4s2p bank? You have any reasonably priced bms companies to suggest? I would go with batrium but $1300 plus later i would out of budget.

 

[HRTKD]

I use two Overkill Solar 4s 120 amp BMS. Support is excellent, warranty is even better.

 

[Gauranga108]

To bad they don't support a higher amperage rating for there 48v bms

 

[HRTKD]

At 48v, are you sure you need that many amps?

 

[Jlibrada]

C

I have 4s2p, not 16s2p. My parallel setup works fine. Please list the issues you're concerned about.

Hello can you let us know how you wired de BMS and brand , each bms + and - terminals goes to the bus bars

 

[HRTKD]

This is how I have my two batteries wired.

Battery 1 (neg) -> BMS 1 -> Shunt A
Battery 2 (neg) -> BMS 2 -> Shunt A -> Negative Common Bus Bar
Battery 1 (pos) -> Fuse A
Battery 2 (pos) -> Fuse A -> Switch A -> Positive Common Bus Bar

Two cables into the shunt, one cable out. Same on the positive side, but into the fuse. A future upgrade may be setting each battery up with its own fuse instead of sharing a fuse.

 

[upnorthandpersonal]

To bad they don't support a higher amperage rating for there 48v bms

Even at only a 100A, that's 4.8kW per battery. You can pull close to 10kW out of a system with one on each of the 16 cell packs (of a 32 call set-up).

 

[Gauranga108]

Even at only a 100A, that's 4.8kW per battery. You can pull close to 10kW out of a system with one on each of the 16 cell packs (of a 32 call set-up).

Ok so again I am new to this stuff but trying to learn fast. So here were my reasons for to larger BMS units:
1) some of wills videos and others on this forum said to better over build bms.
2) in the instance I mentioned, where one bms comes on first or one shuts off and other stays on the stand alone bms could handle the loads.

That being said my max continues load is my submersible well pump that surges when turned on at a max of 30 amps at 230vac, which coverted from ac amps to dc amps is around 158 amps dc, but only for a second then drops down to 11 amps at 230vac. So considering that high spike will it be ok to still downgrade bms from two 300amp daly bms too, two overkill 100amp bms. Other than that initial one second spike my discharge loads are low usually under 70amps dc.

 

[Gauranga108]

I am going to go ahead either way and pull the trigger tonight with Amy for 32 lishen cells with welded studs in the terminals for a dollar more per cell as I heard those m6 studs are cheap and can strip. I will do a little more deliberation on the bms options and here more from all of you on this thread and other threads.

 

[HRTKD]

At least on the 4s 120 amp Overkill Solar BMS, he's tested surge to well over the 120 amp rating and has shown a sustained 120 amp draw. I don't recall seeing any results like that for the 16s version, but it's worth sending him an email asking about it. He is responsive to email.

I wouldn't hesitate putting that load on my two paralleled 4s BMS.

 

[Gauranga108]

@ hrtkd Thanks i will shoot him a message. Also to move forward i noticed you mentions the necessity of a shunt between the bms and common bus on the negative side and fuses on the positive side. Considering my system with two bms and 16s2p bank like I drew above what brand and size shunt and fuses would all of you recommend. Or please send link to another thread that describes sizing shunts and fuses. Thanks again for your insight.

 

[HRTKD]

I have the Victron BMV-712, which comes with a 500 amp shunt. Higher rated shunts are available from Victron. They also offer a Smart Shunt that is the same thing, but without the wall display.

The fuse rating depends on your loads and charge amps. I am using a Class T 225 amp fuse with my 560 Ah of battery capacity. I was not expecting to use my LiFePO4 bank to start my generator, but I may give that a try. If I do that, the 225 amp fuse is marginal. The surge amps from the generator can exceed 225 amps based on what I've read of other's readings.