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choosing the right bms ?! 48v 280ah system

sprinter99

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Oct 29, 2020
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Hi everybody,

I am in the process of starting the install of my 16 EVE cells to make a 48v 280ah bank for my electric propulsion sailboat. I am having a really hard time finding a good reliable bms that is 250a. The only one I can find is the Daly. Do you think it is reliable enough for a off grid (offshore sailing) main battery bank setup. I would choose the not smart bms. If you have any ideas please let me know.

Bonus question.....If I do decide to double my battery bank in the futur and end up with 48v 560ah with 2 250a daly bms, would my total bms power now by 500a ?

I am by no means an experienced lifepo4 diyer so any info will help thank you!
 
That would be a 1C discharge rate on those batteries. Do you need that large of a amps? (For a propulsion motor or large inverter?)

To get that size of amps you probably need to use a contactor. Batrium, Rec-Bms, and Orion are three bms’s that can handle any size of amp draw (depends on the contactor you choose). I used Batrium (and really like it) and used a kilovolt EV200AAANA contactor ( you will need a slightly different one for 48v).

You could also use a smaller 100a bms like overkill) and then use a contactor ( that is controlled by the bms) to control the large load.

Good luck
 
How much charge current will you have?
How much discharge current will you have?
 
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I am having a really hard time finding a good reliable bms that is 250a.
There are lots, but they cost more, and usually won't be easily found on Amazon/Ebay/Aliexpress etc, and usually won't list a current rating outright, because they are not "FET based" (i.e. not 'all in one' BMS's). They use external relays/contactors to control current, so to a degree the current rating is only limited by the external components which gives a lot of flexibility (and the ability to use much higher quality/conservatively spec'd disconnects than with many of the cheaper FET based BMS's. The FET based BMS's are the most popular due to price and simplicity of install/setup, but for high current or critical applications may not be the best choice.

Some examples of non-FET-based BMS's you could look into are:
REC
Orion
Batrium
123smartBMS
TInyBMS
Electrodacus SBMS0
Zeva

I would also suggest checking out two of the links in my signature that have a lot of marine specific discussion on designing lifepo4 systems for boats. The ones that begin with "marinehowto" and "nordkyn design" these are exceptional references and go into BMS selection better than I could.


The only one I can find is the Daly.
Do you think it is reliable enough for a off grid (offshore sailing) main battery bank setup. I would choose the not smart bms. If you have any ideas please let me know.
With the caveat that I haven't spend much time thinking it through, this would not be my choice. I haven't necessarily heard too many issues about Daly reliability and they are pretty popular so if they were failing frequently I think we would hear about it, but at the end of the day its a cheap, commodity, FET based BMS. If my safety depended on it to the extent that it seems like it would in an offshore marine context, I would either (A) shell out the money for something robust and proven, or (B) design your system with some fault tolerance built in (such as two parallel packs each capable of supplying enough power to get you back to shore if one fails, and oversize the BMS's by a good margin.

Bonus question.....If I do decide to double my battery bank in the futur and end up with 48v 560ah with 2 250a daly bms, would my total bms power now by 500a ?
Combine things in parallel and amperes increase, combine things in series and voltage increases. So yeah, 2 x 250A daly BMS's in parallel would be 500A assuming no overhead (not an assumption you should make) and assuming the load is shared equally. If it were me (and I've no direct experience with Daly) I would knock at least 20% off the rating. If you buy a 250A rated BMS, think of it as a 200A BMS or even a 150A BMS. Both because its always better not to be running at 100%, and also because spec inflation is a big concern with a lot of these cheap Chinese components. Daly has a pretty good reputation in that class of product, but still, better to err on the side of caution I think.

I am by no means an experienced lifepo4 diyer so any info will help thank you!
I am not either, and no marine experience, so take my suggestions/musings with a grain of salt.
 
I use a REC bms on my boat for the reasons stated by Dzl. Additionally, if you are in the US, ABYC requires provision for an alarm prior to discharge shutoff. Also, CANbus communication between inverters alternators(not in your case) and other system components and the BMS is really nice to have and in my case lets me sleep better at night knowing that everything is in sync and the BMS is running the show when it comes to charging and discharging. I also prefer an actual contractor to a FET.
 
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Hi everybody,

I am in the process of starting the install of my 16 EVE cells to make a 48v 280ah bank for my electric propulsion sailboat. I am having a really hard time finding a good reliable bms that is 250a. The only one I can find is the Daly. Do you think it is reliable enough for a off grid (offshore sailing) main battery bank setup. I would choose the not smart bms. If you have any ideas please let me know.

Bonus question.....If I do decide to double my battery bank in the futur and end up with 48v 560ah with 2 250a daly bms, would my total bms power now by 500a ?

I am by no means an experienced lifepo4 diyer so any info will help thank you!
What you want is the JBD 300a contactor bms


just made this assembling a pack with that bms

Also I am doing what you are doing, and going with "ENGIRO 205W 08011" 36kw water cooled motor for mine.
 
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