Why isn’t the Victron Battery Protect usable with a solar system?

Hello and thanks for looking...

Will has stated to no longer use a Victron Battery Protect.

I am wondering why and is there an alternative or is leaving that to the BMS good enough?

Thanks.
Shay

It is usable just not in the charge current path.
IMO generally speaking the low voltage cutoff for a commodity BMS is too low to be useful.
For lifepo4 4s setups I want the cutoff to be no lower than 12.0 volts. x2 for 8s and x4 for 16s.

I am guessing the OP is talking about , I was wondering the same thing. It is hard to find the forum post Will is referring to in his comment and I actually still haven't found it, just some references to it in other forums posts. As far as I can tell the problem is that Victron has stated that connecting an inverter (which typically has large capacitors that need to be charged so a big inrush when the battery protector closes again) might damage the battery protector. If anyone has details about the Victron source I am interested. The workaround seems to consist of connect the invertor directly to the battery, and somehow hack the on/off 'switch' of the invertor to go to off when the battery gets too low. See eg https://diysolarforum.com/threads/w...rter-off-instead-of-using-a-relay.3460/page-2

So not related to being in the charge current path. (though smoothJoey is correct that this is also a restriction, current is only allowed to flow in one direction through the BP)

(Another problem with original video of Will is that his setup still disconnects the MPPT charger when the BMS sees something it does not like, he mentions it is a problem but he then ignores it. I still need to look into the updated schematic to see if he fixes it there.)

Acording to the Victron distributor the BP is only for use with DC loads such as lights and pumps it is not and was never intended for use with an inverter. Seems they never thought of using it that way.
Your best bet now is to hack the switch of the inverter or use a relay to cut off the AC loads on the AC side of things this is what I have decided to do.

That's about it. Victron was seeing quite a few BPs being blown up by out of spec current draw when people dead connect inverters. If you have a charge controller that has a switched output load terminal that can be used to control the inverter via a relay if the inverter has a relay contact on/off or the like. Those with a single soft off / on button can be controlled with a little more effort, such as an Arduino board with a simple program, or even a simple cheap PLC. Even if that aspect isn't possible a high current contactor could be slaved to the SCC via a relay to cut DC to the inverter.

Thanks for the info.

For the other problem I don't see any solution on what should be the 'updated design' page (https://www.mobile-solarpower.com/design-your-own-12v-lifepo4-system.html). It advertises to use the Victron MPPT charger, but it lets the BMS disconnect the MPPT charger from the battery in case the BMS sees something wonky. That might damage the Victron charge controller as it is still connected to the solar panels .

I think the only good solutions are:
- Disconnect the Victron 's solar connection with a relay (maybe that unused victron BP )
- Hook into the communication port of the victron and tell it to stop charging when the BMS detects a problem with the cells (I am guessing such a command exist or another way to trick it into stopping loading by playing with threshold voltages).
(in normal conditions the Victron will stop charging out of itself and you can connect it directly to the battery, it is just in extreme corner cases when a cell goes bad that it matters)

Unless I am missing something.

BramEPC said:

Thanks for the info.

For the other problem I don't see any solution on what should be the 'updated design' page (https://www.mobile-solarpower.com/design-your-own-12v-lifepo4-system.html). It advertises to use the Victron MPPT charger, but it lets the BMS disconnect the MPPT charger from the battery in case the BMS sees something wonky. That might damage the Victron charge controller as it is still connected to the solar panels .

I think the only good solutions are:
- Disconnect the Victron 's solar connection with a relay (maybe that unused victron BP )
- Hook into the communication port of the victron and tell it to stop charging when the BMS detects a problem with the cells (I am guessing such a command exist or another way to trick it into stopping loading by playing with threshold voltages).
(in normal conditions the Victron will stop charging out of itself and you can connect it directly to the battery, it is just in extreme corner cases when a cell goes bad that it matters)

Unless I am missing something.

Click to expand...

I have no experience with it, but some threads suggest the solar panel connection maybe isn't that big of a concern with most SCC's.

As for the Victron battery protect, certainly people have and are still using it with inverters? Anyone? Have they all blown up?

Obviously Victron has good reason for saying no to inverters, but can you just maintain best practice while hooking it up and be OK? Is it the initial hook up charge that's the danger, or is it in jeopardy every time the inverter goes on and off?

shaymcquaid said:

Hello and thanks for looking...

Will has stated to no longer use a Victron Battery Protect.

I am wondering why and is there an alternative or is leaving that to the BMS good enough?

Thanks.
Shay

Click to expand...

Hey Shay, I recognize your name from over at skoolie.net. Just read one of your posts actually.

I can shed some light on the Victron Battery Protect.

First a little history:
The Victron BP and SBP were designed to plug the last gap in control within Victron's ecosystem. Victron's chargers and inverters have programmable low/high voltage disconnect built in. The last gap was DC loads which normally run straight off the battery, the BP/SBP were introduced to allow these loads to be controlled as well.

What it isn't designed to do:
Handle reverse current, the BP is a one way street
Handle 'loads with capacitors on their input like an inverter'

What it can do:
Control DC loads
Control An inverter Indirectly
Be used purposely in the opposite direction to control charging

Places this is explained in more detail:
1. The manual
2. This post (actually the whole thread, but this post in particular)
3. This post

See also:
1. This thread
2. These search results (Battery Protect + User:Justin Laureltec)

BramEPC said:

Thanks for the info.

For the other problem I don't see any solution on what should be the 'updated design' page (https://www.mobile-solarpower.com/design-your-own-12v-lifepo4-system.html). It advertises to use the Victron MPPT charger, but it lets the BMS disconnect the MPPT charger from the battery in case the BMS sees something wonky. That might damage the Victron charge controller as it is still connected to the solar panels .

I think the only good solutions are:
- Disconnect the Victron 's solar connection with a relay (maybe that unused victron BP )
- Hook into the communication port of the victron and tell it to stop charging when the BMS detects a problem with the cells (I am guessing such a command exist or another way to trick it into stopping loading by playing with threshold voltages).
(in normal conditions the Victron will stop charging out of itself and you can connect it directly to the battery, it is just in extreme corner cases when a cell goes bad that it matters)

Unless I am missing something.

Click to expand...

Coincidentally I addressed both of these concerns in another post a while back and just came across that old comment a few minutes ago. See here

Short answer, official word from Victron is there is no problem disconnecting the charge controller from the battery while connected to PV

I have a BP connected directly to my inverter. Not had a problem in over 4 years. TBF the instruction do not say you must not connect them directly to inverters at all, whilst it does say :-
3. The SBP is designed to allow current to flow from IN (battery) to OUT (load) terminals only. Reverse currents from OUT to IN terminals are strictly forbidden, and will damage the device. If you wish to use the SBP as a disconnection for a charge source, you must orient the unit in the system so that the current is flowing in the intended direction, IN to OUT.

so that's a nono.

4. The short circuit protection of the SBP will be activated if you try to directly connect loads with capacitors on their input (eg inverters). For that use case, please use the SBP to control the remote on/off switch on the inverter, instead of disconnecting the higher power DC line.

Does not say anything about blowing anything up - or invalidating warranty or that it is forbidden to connect in this manner. It is purely advisory.

But for me the bigger issue is the fact that it wont disconnect at any higher than 12V. 12V for an AGM is 80% depleted. I don't want to go lower than 50% so now I have new AGM batteries the BP is useless.

Umpa said:

I have a BP connected directly to my inverter. Not had a problem in over 4 years. TBF the instruction do not say you must not connect them directly to inverters at all, whilst it does say :-
3. The SBP is designed to allow current to flow from IN (battery) to OUT (load) terminals only. Reverse currents from OUT to IN terminals are strictly forbidden, and will damage the device. If you wish to use the SBP as a disconnection for a charge source, you must orient the unit in the system so that the current is flowing in the intended direction, IN to OUT.

so that's a nono.

4. The short circuit protection of the SBP will be activated if you try to directly connect loads with capacitors on their input (eg inverters). For that use case, please use the SBP to control the remote on/off switch on the inverter, instead of disconnecting the higher power DC line.

Does not say anything about blowing anything up - or invalidating warranty or that it is forbidden to connect in this manner. It is purely advisory.

But for me the bigger issue is the fact that it wont disconnect at any higher than 12V. 12V for an AGM is 80% depleted. I don't want to go lower than 50% so now I have new AGM batteries the BP is useless.

Click to expand...

I agree with you that their language on the inverter point is much less strong and more vague. But here is what @Justin Laureltec , a Victron Product Expert, and moderator in the Victron Tech Support forum has said on the matter:

Another note is that Victron does NOT support the use of a BatteryProtect between a battery and an inverter. The inrush current of an inverter turning on can far exceed the BatteryProtect's rating and, again, fry the FETs. I know there are diagrams on this forum showing them connected this way, and that's an issue I'm addressing on a case-by-case basis... but please stop using them this way. Any reputable inverter has its own low-voltage disconnect, and does not need this device. The BatteryProtect is primarily designed to hook to a set of small loads only, such as fans, lights, refrigerators, and the like, and provide low-voltage disconnection to those items that do not already have this protection built in.

Click to expand...

To everyone else on this thread: yes, you can use a BP as a charge disconnect only or a load disconnect only (one device cannot perform both functions at the same time). To use it as a charge disconnect, the BP must be connected in reverse - that is, the charge source must be connected to the "in" post and the battery must be connected to the "out" post.
There are a total of two things that you cannot do with a BatteryProtect:
1. Permit reverse current through it (vOut>vIn).
2. Disconnect the main DC line of an inverter. If your inverter has a remote disconnect, you may use the BP to trigger the remote disconnect; if it does not, you could use the BP to trigger an external relay that disconnects the DC line... But you can't use the BP to disconnect the DC line directly.

Click to expand...

And explained in more detail here

@Dzl
They can't apply new rules retrospectively, despite their efforts otherwise. It is what it is.
If I buy one/or get one under warranty - then sure I have to follow any NEW instructions that comes with the product - as is I go with the instructions I already have. That's the way I see it. If I had known they were going to move the goal posts on how to install it then I might have looked for another solution.

TBF, I think it only has a years warranty with it anyway - so mine are well out - and I am not changing my set up now. I might fit it in a metal box just in case of a fire but other than that - meh!

It all sounds like a damage limitation exercise to me on behalf of Victron to me.
Don't get me wrong if I were them that's exactly what I would be doing, but I am not sure how much weight an update on a forum or website has legally. I bet they are still liable regardless of what they say afterwards.

Just my thoughts - I should add to my sig 'I am also not a solicitor' - lol

Umpa said:

@Dzl
They can't apply new rules retrospectively, despite their efforts otherwise. It is what it is.
If I buy one/or get one under warranty - then sure I have to follow any NEW instructions that comes with the product - as is I go with the instructions I already have. That's the way I see it. If I had known they were going to move the goal posts on how to install it then I might have looked for another solution.

TBF, I think it only has a years warranty with it anyway - so mine are well out - and I am not changing my set up now. I might fit it in a metal box just in case of a fire but other than that - meh!

Click to expand...

That is your prerogative. Its up to you to decide how you want to use your equipment based on the information you have the risks you want to take, etc. I can understand you wanting to continue using it the way you have been, since if hasn't been a problem yet, even though its not recommended and may eventually lead to failure. Personally I wouldn't, but I can understand your desire to.

The liability/warranty side isn't my concern here, though I don't share your optimism that you would be covered. I just want to understand how it can and can't / should and shouldn't be used and why and convey that information to others who come across this thread.

I think its prudent to follow the manufacturer recommendations and the advice of tech professionals in most cases (including this one). But my opinion doesn't really matter, I just want to make clear to others what the guidance from Victron, and Victron Product Experts is. Do with it what you will.