Reverse current on BatteryProtect 48V-100A

[mburris]

I have been designing and now purchasing components for my RV system. I will have 3 separate 48v batteries. Each battery will be 16s x 3.2v x 180a. I was intending to purchase three Victron Battery Protect 48v-100a. These would be installed between each battery and the central bus. The BMS for each battery would be programmed to "trip" the battery protect in case of under voltage, over voltage, over temp, under temp, and cell imbalance.

The central bus would also have the charger/inverter connected to it. The documents from Victron state : "* The BatteryProtect is not designed for reverse currents from charging sources." Does this mean the current can not go back through the battery protect from the central buss to charge the batteries? If so, I don't understand the purpose of this device. I can't get my mind to wrap around an idea of being connected to a system for a discharge scenario, but not for charging. Unless you start including massive diodes.

I am also looking for recommendations on a quality BMS that will meet these parameters for each battery.

 

[Justin Laureltec]

The BatteryProtect has a very specialized niche and is very useful in this niche; outside of the niche, it is not useful. You are correct that you must not use the BatteryProtects as you are currently planning; they will overheat, they will fail, and they will potentially cause severe damage to themselves and/or other components on your system. Absolutely positively do not purchase them for this purpose.

EDIT:
For reference and a more in-depth discussion of the actual design purpose of the BatteryProtect, see this thread and also this one, and really several others on this forum... Bottom line, though, is that questioning the reasons for the limitation is rather fruitless - just know that you'll need a different device to do what you're intending to do.

 

[mburris]

Thank you for keeping me from wasting my money.

1. Do you have anything else you recommend?

2. Just what are the Victron battery protect used for? They seem kind of useless.

 

[Justin Laureltec]

Thank you for keeping me from wasting my money.

1. Do you have anything else you recommend?

2. Just what are the Victron battery protect used for? They seem kind of useless.

You're welcome!
1. No, unfortunately. For many use cases I recommend the Sterling ProLatch-R instead, but it cannot be externally triggered by your BMS and it's only good to 24v, so it's not applicable for you. I only deal with a very select group of Tier-1 components, though, so my knowledge of other products is limited - I'm sure others here will have some input.

2. The BatteryProtect is generally used to disconnect non-critical DC loads before battery failure... see the thread links that I added above (in my edit) for some in-depth background of the use-cases for which they are designed.

 

[mburris]

Thank you again. I missed the thread references when I first read your reply. That explains it. Seems like an a pretty expensive component for what it does.

This really is really not a "battery protection" device designed to remove a battery from parallel or service. It would be more properly labelled as a load shedding device.

 

[Justin Laureltec]

Thank you again. I missed the thread references when I first read your reply. That explains it. Seems like an a pretty expensive component for what it does.

This really is really not a "battery protection" device designed to remove a battery from parallel or service. It would be more properly labelled as a load shedding device.

LOL, well I think "Victron Smart Load Shedding Device" doesn't quite roll off the tongue as easily And it does protect the battery... by removing non-critical loads before they discharge the battery beyond recovery. As with most things in the world, there isn't a simple solution to every possible problem... gotta take the problems one at a time and address them as best as possible. Your BMS should be taking a battery offline if necessary, and in the Victron world all non-critical DC loads will be disconnected by the BatteryProtect and critical loads will continue as long as possible until disconnected by the Victron inverter or inverter/charger and, as a last resort, by the BMS.

In a fully Victron environment, this component combination works perfectly; in a non-Victron environment there are holes in the functionality, since the devices are in a standalone configuration and can't interact with each other like they normally would. Some might fault Victron for this, but eh... it's a bit unreasonable to expect a single company to provide for an infinite number of component combinations and solve all the possible problems.
Victron's stance is, basically, why would anyone ever design a non-Victron environment... and, if budget isn't an issue, I fully agree.