Take 2: Please critique my LifePO4 + Solar upgrade plans

[herrakonna]

Based on all of the great feedback and suggestions I received from my previous plan, I have revised my installation plan as shown below.

Is there anything else I should still do differently / add / remove / whatever?

Thanks.

 

[mikefitz]

Over current fusing could be improved. Class T 100A near to the positive battery post, within 15 cm. More ideal would be a fuse for each battery before the parallel conection. Could use MRBF fuses here with Blue Sea fuse holders.
Fuses for the feed from the DCC50, fuse for charger, fuse ( not shown ) for fuse box feed , say 40A, fuse for feed to the CBE DS300 ( not shown) say 40 A. All these need to be close to the positive junction point, ( a buss bar would be ideal) to protect the cable runs.
Fuse for the starter battery needs to be close to the battery.
Both the fuse box and the CBE DS 300 are not designed for currents over about 40 amps

Regarding the CBE system, this has chargers for the house and starter battery and a ' combiner' that connects starter and house battery, I assume you are taking steps to integrate the CBE units with the additional components.

Mike

 

[MisterSandals]

Connecting the charge/load leads to a single battery instead of + to one battery and - to the other battery will result in battery imbalance. The battery with the connections will send/receive more current as its the path of least resistance.

 

[herrakonna]

Over current fusing could be improved. Class T 100A near to the positive battery post, within 15 cm.

The distance from the positive battery post to the Class T fuse would be around 20cm

More ideal would be a fuse for each battery before the parallel conection. Could use MRBF fuses here with Blue Sea fuse holders.

Changed single Class T to dual MRBF fuses, thanks.

Fuses for the feed from the DCC50, f

Added a 60A ANL from the DCC50S

use for charger, fuse ( not shown ) for fuse box feed , say 40A, fuse for feed to the CBE DS300 ( not shown) say 40 A. All these need to be close to the positive junction point, ( a buss bar would be ideal) to protect the cable runs.

Added a 50A ANL to the DS 300 (the CBE manual shows a 50A fuse between the battery bank and the distribution box)

Fuse for the starter battery needs to be close to the battery.

There is already a fuse near the starter battery, part of the original RV manufacturer build. The 60A ANL at the charger input end is extra, but added the starter end fuse to the diagram for clarity

Both the fuse box and the CBE DS 300 are not designed for currents over about 40 amps

The fuse box is rated at 100A total, 30A max per individual blade fuse, and since each positive connection from the box will be individually fused and I can ensure the total rating of all blade fuses in the box are at most 100A, I presume no separate dedicated fuse for the box is needed.

Regarding the CBE system, this has chargers for the house and starter battery and a ' combiner' that connects starter and house battery, I assume you are taking steps to integrate the CBE units with the additional components.

Yes, the starter battery connection will be removed from the DS 300 entirely. The only downside to removingn it is that the starter battery voltage will not be available for display on the CBE info panel, but I have other means to monitor the starter battery voltage, via the Webasto system.

The DCC50S will then provide trickle charging of the starter battery (rather than the DS 300) from solar if/when needed, when the house bank is fully charged.

Mike

Thanks for the input. Attached is an updated diagram with the suggested changes:

 

[herrakonna]

(deleted)

 

[herrakonna]

Connecting the charge/load leads to a single battery instead of + to one battery and - to the other battery will result in battery imbalance. The battery with the connections will send/receive more current as its the path of least resistance.

View attachment 176192

That's actually how my current SLA bank is connected and how I've had AGM banks connected in the past; however, the configuration in my diagram follows the official Renogy guide video for configuring two 100Ah smart batteries in parallel, which instructs to connect the charger(s) and load(s) to the last battery in the parallel bank.

C.f.

Connecting the load to Pos/Neg posts on different batteries in the bank perhaps is only be relevant to traditional battery types and not smart LifePO4 batteries (?) as the smart batteries in the bank will all communicate with each other to balance the bank, etc.

Also, given the high discharge rate of these LifePO4 batteries and their chemistry, it would seem that "overworking" one battery in the bank over another is not a concern as it would be with other battery chemistries.

But I'm quite happy to be educated about this -- and I suppose connecting the bank from the positive of one battery and negative of the other can't hurt, regardless, so that's probably what I will do.

 

[herrakonna]

Updated plan:

 

[MisterSandals]

Connecting the load to Pos/Neg posts on different batteries in the bank perhaps is only be relevant to traditional battery types and not smart LifePO4 batteries (?) as the smart batteries in the bank will all communicate with each other to balance the bank, etc.

If the 2 batteries have different load and charge currents they will charge and discharge differently regardless of battery type.

So how exactly does the balancing happen? Its either active balancing where "something" pulls from one battery and charges the other, or passive balancing where the higher battery has a load that discharges it. I see neither of these mechanisms in your diagram. Please correct me if i am wrong.

 

[herrakonna]

If the 2 batteries have different load and charge currents they will charge and discharge differently regardless of battery type.

So how exactly does the balancing happen? Its either active balancing where "something" pulls from one battery and charges the other, or passive balancing where the higher battery has a load that discharges it. I see neither of these mechanisms in your diagram. Please correct me if i am wrong.

The two batteries in the bank are identical in every way (capacity, chemistry, manufacturer, model). I don' t know exactly how the balancing occurs, but the documentation says that the RS-485 connected batteries balance themselves and it is managed by the BMS's

 

[mikefitz]

The fuse box is rated at 100A total,

Yes but the feed cable is not rated for 100A.

documentation says that the RS-485 connected batteries balance themselves and it is managed by the BMS's

This is a Renogy system that has been known to produce unexpected issues. You may wish not to use this feature.

will be removed from the DS 300 entirely

You may/will loose some features, step control, fridge control

 

[herrakonna]

Yes but the feed cable is not rated for 100A.

Ah, right. I will use 4 AWG for those short connections and may also consider adding a dedicated ANL fuse as well. Thanks.

This is a Renogy system that has been known to produce unexpected issues. You may wish not to use this feature.

My installation doesn't rely on that feature, though I will look into what those issues might be. Any links?

You may/will loose some features, step control, fridge control

Yes, I am expecting to have to connect the step autoretract trigger wire to the vehicle AUX+

I also will no longer see the starter battery voltage in the CBE panel, but have other ways to monitor starter battery health

I will have to see if/how the fridge is affected, and can rewire it separately from the DS300 if needed. I never use the AC or DC option, only propane, and in the near future will be replacing the current 3-way fridge with a 12V DC compressor fridge, so no worries there

 

[mikefitz]

I will look into what those issues might be. Any links?

There was a report on this forum, perhaps a search will find. I seem to remember the situation, with the batteries linked, was an inability to deliver full battery current . By removing the link the batteries behaved as expected.
Renogy have bizarre 'shelf' mode where the battery will shut down if no significant charge/discharge takes place, again this has been discussed on this forum.

Epever MPPT charger confused by Renogy battery inactivity?

Hi, I put a new 200Ah Renogy bluetooth battery in an existing van. The van has a Victron DC/DC charger, and an Epever MPPT solar charger. Both the Victron and the Epever MPPT have been working, and I have also seen them working on the Renogy battery. Also the Renogy battery itself works fine, it...

diysolarforum.com

Another issue that sometimes appears on the forum, ,(applies to many low cost batteries), is that a high charge voltage, 14.4 volts, causes the battery BMS to shutdown the charge path , ( due to cell inbalance causing the BMS to enter protection mode). This may have undesired effects on the system voltage as the charger may be slow to respond. Renogy technical help suggested lowering the charge voltage, ( down as far as 13.8 volts if necessary), not all chargers have this option. It's not usually a serious issue and over time the battery becomes more balanced.

 

[herrakonna]

There was a report on this forum, perhaps a search will find. I seem to remember the situation, with the batteries linked, was an inability to deliver full battery current . By removing the link the batteries behaved as expected.
Renogy have bizarre 'shelf' mode where the battery will shut down if no significant charge/discharge takes place, again this has been discussed on this forum.

Epever MPPT charger confused by Renogy battery inactivity?

Hi, I put a new 200Ah Renogy bluetooth battery in an existing van. The van has a Victron DC/DC charger, and an Epever MPPT solar charger. Both the Victron and the Epever MPPT have been working, and I have also seen them working on the Renogy battery. Also the Renogy battery itself works fine, it...

diysolarforum.com

Another issue that sometimes appears on the forum, ,(applies to many low cost batteries), is that a high charge voltage, 14.4 volts, causes the battery BMS to shutdown the charge path , ( due to cell inbalance causing the BMS to enter protection mode). This may have undesired effects on the system voltage as the charger may be slow to respond. Renogy technical help suggested lowering the charge voltage, ( down as far as 13.8 volts if necessary), not all chargers have this option. It's not usually a serious issue and over time the battery becomes more balanced.

Thanks, fortunately both of the chargers are Renogy chargers and are able to wake Renogy batteries if/as needed.