question

gypsy freedom avatar image

can the smart battery protect be run in parallel to provide higher continuous amperage

i have a 3000 watt inverter running off a 660 amphour 12 volt battery bank. i occasionally will pull close to 300 amps for several minutes from the battery bank. this seam like it would exceed the amp rating on the 220a smart battery protect unit. could i run 2 of these units in parallel to provide the amperage capacity? or is there another similar product. my primary desire is adjustable/programmable low voltage cut off protection.

amps
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

3 Answers
kai avatar image
kai answered ·

Maybe... until Murphy says hi? Your proposed arrangement wasn't likely on the product design team's mind. With two in parallel you're effectively current sharing across the two devices and assuming the internals of the smart BP-220 have similar resistance you would remain under the 220A on each leg for most of the "overload" period. I would assume that simultaneous switching is not going to favour you, but as you noted the 600A surge rating should protect the late switcher. On the other hand, if you try to surge the inverter when the battery bank is being charged up (and only 1 SBP is active due to mismatch in the reconnect threshold) that SBP will carry all the surge current. There's nothing on the datasheet that talks about high current disconnect so if the surge persists > 30seconds, you're operating equipment outside of spec (and presumably warranty).

Bottom line is, you're looking at using equipment outside of design intent and need to carry all the associated risks if you want to pursue this solution.


There are other viable solutions:

1) A VSR that is rated for your current (i.e. inbuilt contactor) - e.g. gigavac MXSL15

2) roll your own with a suitable contactor and interface a low power sensing circuit (which may be a low power VSR or something else) to the contactor. e.g. redarc VS12 -> gigavac GV240

** Not product or system recommendations, just examples. BYO due diligence.

3) Tweak your system design to reduce the surge current.

In all cases ensure that the voltage detection part has some hysteresis to stop contactor bouncing at the switch threshold.

1 comment Share
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Don't forget a pre-charge circuit, or your contactor will be damaged quickly.

gypsy freedom avatar image
gypsy freedom answered ·

i am sorry but while the info you provide is accurate, it in no way answers my question.


can the battery protect units be run in parallel or does victron offer some other device for higher amperage. or lastly does someone know of another product from another company that can provide adjustable/programmable LVD protection, preferably with many of the other benefits of these victron BP-220 units


just so you dont think i am being a jerk, inverter is non-configurable and the built in shut down is no where near the desired set point. also ALL load go through the inverter. just the way it is


i know by the basic laws of electricity i could technically run 2 of them in parallel for higher amperage capacity but i dont know if there are any drawback or problems that may come up with 2 working side by side. like perhaps what if each units calibration is slightly off and 1 unit shuts off before the other. then for a short time all current would be going through just one unit. these units have a 30 second surge ratting and perhaps that would cover something like that. maybe there are other issues i have not thought of as to why it would not work. but i would rather here from someone that knows rather than have people tell to just do things different


so if someone can answer my original question it would be much appreciated

1 comment Share
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

To ad another thing you don't want to hear: the battery protect is not suitable for switching loads like inverters due to the big inrush current (to charge the capacitors inside the inverter)

So if you do want to use it, you'll need a pre-charge circuit also.

Sorry for not answering the original question. I think it will be difficult, indeed because how to switch at the same time (might use external input from a battery monitor?)

btw, doesn't the inverter have a remote switch? usually there is a connection that is bridged with a wire, where you can wire in an external switch.

Boekel avatar image
Boekel answered ·

With high Current circuits, you want as little resistance / voltage drop as possible.

So if possible: connect Inverter directly behind the (main) fuse, configure inverter to stop at a safe voltage for the batteries.

The battery protect you can use for other (DC) loads to protect the battery.

Share
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.