Chargery BMS now with Low Temp Cutoff

[jaffadog]

I’ve ordered the Chargery BMS8T from Jason, the BlueSea 7713, and a few SSRs including the optocoupler @Will Prowse recently demonstrated. When the gear arrives I’ll do some testing and post back with my observations.

I’m considering a similar arrangement. But the Chargery wants to drive separate charge and discharge disconnect relays, and these Blue Sea 7713 relays are wicked expensive. Are you planning to use a small SSR to combine those signals into one as @DW SD did? I’m looking at the BMS as purely safety gear. I’m not expecting it to ever fire its protections routinely/operationally. So I’d be willing to put up with the consequences of a single relay that just takes the whole battery offline. Note the 7713 has a built in manual override knob, so in emergencies or recovery scenarios, you still have the option to override the BMS.

 

[greyghost]

@jaffadog In my case, this as my first foray into LFP aboard my boat. I'm planing to try this set-up as a battery bank for operating my bow thruster and anchor windlass. The remainder of the boat is AGM for now, so I will cross the twin 7713 bridge when I migrate to more complete use of LFPs aboard. For now, I will use a Victron DC-DC charger to keep this battery topped up. Their charger has terminals for an on/off switch. I plan to use an opto coupler to open/close the charge circuit and another optocoupler to open/close the 7713 discharge circuit. I will look at the single relay option you mention but, offhand, it seems like a reasonable way to proceed if you are OK with the possibility of having to manually reset on occasion. Is your charger tolerant of instantly losing its load?

 

[Craig]

I’m considering a similar arrangement. But the Chargery wants to drive separate charge and discharge disconnect relays, and these Blue Sea 7713 relays are wicked expensive. Are you planning to use a small SSR to combine those signals into one as @DW SD did? I’m looking at the BMS as purely safety gear. I’m not expecting it to ever fire its protections routinely/operationally. So I’d be willing to put up with the consequences of a single relay that just takes the whole battery offline. Note the 7713 has a built in manual override knob, so in emergencies or recovery scenarios, you still have the option to override the BMS.

Somehow you just need to figure out a way so that if either chargery relay controll line goes off the whole thing shuts down I do not know if it is as simple as putting them in series (Im afraid that might cook the chargery)

 

[jaffadog]

@greyghost I'm also putting together a new electrical system for my boat. Small boat. 28' BCC. First foray as well. I have purchased 8 100 AH Fortune cells for the house bank which will be 12v 2P4S - replacing AGMs. I'll keep a dedicated AGM engine start battery. I'm planning on using an isolator like the Victron Argo FET to split the alternator between the two banks. It will be safe from BMS disconnects as the AGM will always be there. I could put all charge sources through that if need be (shore power and solar) to keep them happy during BMS disconnect events.

 

[jaffadog]

Somehow you just need to figure out a way so that if either chargery relay controll line goes off the whole thing shuts down I do not know if it is as simple as putting them in series (Im afraid that might cook the chargery)

Yeah, I don't think you can put the Chargery charge/discharge lines in series. Each one of these is supplying current. They are not simply switching a circuit.

 

[grizzzman]

Yeah, I don't think you can put the Chargery charge/discharge lines in series. Each one of these is supplying current. They are not simply switching a circuit.

This is "NOT" correct information. It will work just fine. I am testing with a 500 amp Kilvac EV200 and a jomall JOSSR-120 DD SSR. (Using this at 37 amps had an unacceptable voltage drop) It now switches the Kilovac during an overvoltage event. The Kilovac disconnects during a low voltage event. If you want to see how the circuit is set up, look at DW SD post 262 on page 14 of this thread. This set up pulls less then .25 amps an hour.

 

[BiduleOhm]

Even if it works I would put diodes to do a basic OR gate and isolate outputs from each other. Just a good practice costing only a few cents.

 

[grizzzman]

Great advice. There on the bench ready for install.

 

[DW SD]

Series is acceptable.
If they are in series, which effectively the way I wired mine is, there are corner cases where the battery will be offline entirely when only either load or charge should be disrupted but not both. For example, below freezing temps the load circuit should be active but charging not. There would be other examples.

hopefully each system would be setup so the disconnects are extreme anomalies.
I have my LFP in parallel with AGM so as to avoid a scenario where the alternator or SCC doesn’t “see” a battery. And then the AGM would take over at <20% SOC.

Yeah, I don't think you can put the Chargery charge/discharge lines in series. Each one of these is supplying current. They are not simply switching a circuit.

 

[jaffadog]

@DW SD 's #262 diagram is not a simple series circuit. He has his bosch relay in there. I mean you can't simply daisy chain the Chargery charge and discharge relay control ports.

Personally, I'm all good with any BMS protection taking the battery offline - for both charge and discharge loads combined (e.g. common port behavior). I don't plan on the BMS tripping protections for operational conditions. Just whacky unforeseen departures from normal. I plan on adding an high amperage BMS bypass switch so that I can override BMS logic if needed - either because it's an emergency or that's whats required to recover from the anomaly (like charging a severely discharged battery).

 

[DW SD]

Do you know Boolean logic?
This circuit is an OR operation for the BMS load and charge.
so...... Any condition which interrupts either charge or discharge interrupts the battery entirely.
Like I said there are corner cases where the battery doesn’t need to be disconnected for protection but might. I chose this to save costs on another $130 contactor.

You could map them out for your application.
I don’t camp in freezing weather. And in hot weather it might disconnect. But then id expect to have hookup for AC and then the AGM bank would operate just fine.

I’m comfortable with my use case and parameters.
Hope this doesn’t seem argumentative. Decide what works for you and then go from there.

 

[Bob B]

Not getting much attention in the thread I started. So I thought I would LINK TO IT HERE

Wondering about the Chargery charger.

 

[tim0shel]

On your Charge relay shouldn't it only be as big as your charger? Like if I have an 75 amp charger running a 85ish amp relay. If you are only going to charge at 25 then running a 40 amp relay etc. Then your main one be 200 or 300 amp relay

 

[Steve_S]

On your Charge relay shouldn't it only be as big as your charger? Like if I have an 75 amp charger running a 85ish amp relay. If you are only going to charge at 25 then running a 40 amp relay etc. Then your main one be 200 or 300 amp relay

If using a "Common Port" configuration, then the Discharge & Charge relays need to accommodate the highest Amperage expected to be seen, so the highest Amp draw from the Inverter possible. If the Charge relay was only up to 100A and you pulled 150A through it, it would NOT be pretty.

If using a "Separate Port" configuration, then the Discharge Relay has to accommodate the Max Load potential, while the Charge Relay only needs to handle that Max Amperage inbound from the Charging Device(s).

 

[jaffadog]

On your Charge relay shouldn't it only be as big as your charger? Like if I have an 75 amp charger running a 85ish amp relay. If you are only going to charge at 25 then running a 40 amp relay etc. Then your main one be 200 or 300 amp relay

There is no harm in having a relay whose capacity far exceeds your max expected load.

 

[tim0shel]

There is no harm in having a relay whose capacity far exceeds your max expected load.

I completely agree with this. Thats why i've gone with the 200amp relay but on my charge size there is no reason to have this size if going with SSR.

 

[DW SD]

@Steve_S
In your SSR testing, if you turn up a very low power solution to plug and play replace my Bosch cube relay in my "Common Port" design, please update. I'd spend $20 to save some power. I only have 900W of solar and decent steady state draws, so every bit helps. Then again, we're only talking a few Ah per day.
Cheers, Doug

 

[Steve_S]

@Steve_S
In your SSR testing, if you turn up a very low power solution to plug and play replace my Bosch cube relay in my "Common Port" design, please update. I'd spend $20 to save some power. I only have 900W of solar and decent steady state draws, so every bit helps. Then again, we're only talking a few Ah per day.
Cheers, Doug

Craig is doing the serious Heavy Lifting on SSR Testing & Evaluation. I will be doing my own determination tests on a few SSR's and for some new specialised SSR's being cooked up right now (in development & prototyping now) which hopefully I'll get my hands on in about 3 weeks but again, in my case, this will be real time in a production environment and a bit limited in that respect. I can very safely say that NONE will be $20 or even $40.

 

[DW SD]

Craig is doing the serious Heavy Lifting on SSR Testing & Evaluation. I will be doing my own determination tests on a few SSR's and for some new specialised SSR's being cooked up right now (in development & prototyping now) which hopefully I'll get my hands on in about 3 weeks but again, in my case, this will be real time in a production environment and a bit limited in that respect. I can very safely say that NONE will be $20 or even $40.

If you identify SSR that will save some power over the Bosch cube in the common port design (1.5Watts) please post.
I considered buying the SSR Will Prowse linked to. https://www.amazon.com/Opto-22-Cont...15aa5b6c5beed4bd547eeae07b42e2&language=en_US

But it wasn't clear the power consumption. If I could shave by a factor of 10, it'd be worth the reliability and power save for $20.
Seems like @Craig 's thread is about heavy duty loads to replace the contactors (which I understand is what he and you want).

Cheers,

Doug

 

[Craig]

If you identify SSR that will save some power over the Bosch cube in the common port design (1.5Watts) please post.
I considered buying the SSR Will Prowse linked to. https://www.amazon.com/Opto-22-Cont...15aa5b6c5beed4bd547eeae07b42e2&language=en_US

But it wasn't clear the power consumption. If I could shave by a factor of 10, it'd be worth the reliability and power save for $20.
Seems like @Craig 's thread is about heavy duty loads to replace the contactors (which I understand is what he and you want).

Cheers,

Doug

The relays I tried draw about .01 amps at 12V so thats 2.9 Watts per day for each relay.
The relays work very well but the terminals do get hot after 15 minutes of a 150Amp load.
If you have less than a 50Amp load they will work just fine and not even get warm.

The relay manufacturer I am working with is making me new relays with larger terminals for testing. They are basically tripling the surface area of the terminals. The one I am using right now daily with standard terminals works perfect but I never have more than a 20 Amp load normally. If I do go higher it is to run a saw or something and the time is relatively short.