Correcting poor “professionally installed” system: 400ah 3000w inverter

TLDR: inverter wired to opposite terminals than rest of loads/inputs on a dual battery setup. Scream foul?

I have a long list of poor decisions I’ve inherited from a well-regarded van building company in a van I purchased from them back in July, and would love some help fixing them!

First off, something I cannot seem to find an answer for anywhere: the system has two li time 200ah batteries wired in parallel, with DC loads and charging inputs on positive of battery no.1 and negative of battery no.2, but the inverter is hooked up to negative of battery no.1 and positive of battery no.2

Is this a big no no? Or should it be fine? It certainly isn’t how I would’ve done it!

(For those curious, I’m still trying to work with company to try and fix the errors so I’ll refrain from naming them for now)

(Never mind the li time battery bms cannot support 3000w, that’s another issue that is hopefully getting solved by the van company by dropping in the ‘plus’ version of the battery with better bms. Oh and the breaker is too small, no bus bars, no battery monitor, undersized cables, no master switch, cheap breakers instead of fuses, unprotected wires, loose connections, wrong charging settings… nightmare fuel!)

Full equipment list:
2x li time 200ah batteries in parallel
3000w Renogy inverter
Renogy Rover Li MPPT
Renogy 40a DC to DC
400W of solar


thanks in advance and sorry for the long read!

If all the Positives are connected together and all the Negatives are connected together all should be working fine.

as far as the workmanship, accessories, breakers, fuses, wires, wire size, I can't really address that...

That is the correct method to wire two parallel batteries.


https://www.usbattery.com/configurations/

The fact that loads vs charging is opposite makes no difference.

Here is some math to the method:
http://www.smartgauge.co.uk/batt_con.html

Low resistance lithium actually makes the balance issue more critical.

Skiwi said:

First off, something I cannot seem to find an answer for anywhere: the system has two li time 200ah batteries wired in parallel, with DC loads and charging inputs on positive of battery no.1 and negative of battery no.2, but the inverter is hooked up to negative of battery no.1 and positive of battery no.2

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I don't think that would work. You would have had nice fireworks when the wires were connected. I suggest posting a pic of what you have.

DIYrich said:

I don't think that would work. You would have had nice fireworks when the wires were connected. I suggest posting a pic of what you have.

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It will work fine assuming it is positives to positives and negatives to negatives.

That is exactly how it's supposed to work so current flows evenly through both batteries.

Not sure why you want a master switch if you have breakers it provides both switched power and OCP.

Each battery bms provides half the load so combined they should be able to handle the breaker size.

You really need a shunt based battery monitor - which should mean all the negative wires go to the shunt - then out to the loads and chargers - preferably on a bus bar.

Also, since you have a 3000w inverter the main bus wires - from battery to shunt & class T fuse and to distribution bus bar and on to inverter should be 4/0 cables.

Also 400w may be a bit light for solar - can you fit any more?

Rocketman said:

Also 400w may be a bit light for solar - can you fit any more?

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On a van?

What loads are you using that need true 3000W continuous?

If you mean this:




It will work until you want to install a shunt. Once you do that, all (-) must be connected to the system side of the shunt.

Rocketman said:

You really need a shunt based battery monitor - which should mean all the negative wires go to the shunt - then out to the loads and chargers - preferably on a bus bar.

Also, since you have a 3000w inverter the main bus wires - from battery to shunt & class T fuse and to distribution bus bar and on to inverter should be 4/0 cables.

Also 400w may be a bit light for solar - can you fit any more?

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That all would be nice but not needed. He has a budget cheap renogy equipment so they installed what would work not what's best

Wow I turn my back for a second and all you lovely people have chimed in! Thank you!

My main thought process here was seeing if the installer of the system had really messed up the wiring of the inverter. Therefore I would have a case in asking them to put in the bus bars (or a lynx distributor) that I am going to need anyway in order to put in a shunt based battery monitor (looking at the victron solution for this). Seems like the way that it is currently is workable, although not mainstream. If this journey has taught me anything: if you want it done right, do it yourself! Don’t get me started on the leaky windows! I will be verifying the cable diameters between battery and inverter shortly, the fact that it is protected with a 200a breaker is not encouraging.

@sunshine_eggo : that’s exactly it.
@Rocketman : yep you got it, and unfortunately not much real estate to work with! In the winter the dc to dc charger becomes critical.
@henrys : we have a dual induction cooktop and hoping to add a 1800w air fryer, both limited in time of use but heavy draw while they’re on (separately of course). Friends setup with less ah/solar has similar draw and has served them well (although with victron gear).

Again thank you all for your input!

HighDesertOffgrid said:

On a van?

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Absolutely - 400 watt is really kind of a minimum for a van. It can work in good weather, but not in overcast.

Skiwi said:

Wow I turn my back for a second and all you lovely people have chimed in! Thank you!

My main thought process here was seeing if the installer of the system had really messed up the wiring of the inverter. Therefore I would have a case in asking them to put in the bus bars (or a lynx distributor) that I am going to need anyway in order to put in a shunt based battery monitor (looking at the victron solution for this). Seems like the way that it is currently is workable, although not mainstream. If this journey has taught me anything: if you want it done right, do it yourself! Don’t get me started on the leaky windows! I will be verifying the cable diameters between battery and inverter shortly, the fact that it is protected with a 200a breaker is not encouraging.

@sunshine_eggo : that’s exactly it.
@Rocketman : yep you got it, and unfortunately not much real estate to work with! In the winter the dc to dc charger becomes critical.
@henrys : we have a dual induction cooktop and hoping to add a 1800w air fryer, both limited in time of use but heavy draw while they’re on (separately of course). Friends setup with less ah/solar has similar draw and has served them well (although with victron gear).

Again thank you all for your input!

Click to expand...

Can you take a few photos of what you have and post the info?

Most people here are quite familiar with the items that you listed, but it might help us to really see what you are dealing with.

As a practical matter, it is common for people to install a larger inverter wattage than batteries can support in case you want to add more capacity in the future.

If you want 2 each batteries in that general size range that will really power that size inverter, the ones that come to mind are the battle born game changers. Not all that many others can do that. 4 each, 100 amp-hr batteries would be a better choice for actually pumping out the required amps if you want to go to another brand.

As far as LiFe batteries in a van in Maine in the winter - seems dicey unless you are going to always keep the van interior above 40 F with a fuel heater - 24 x 7. If you don't plan to keep the van interior warm in the winter, then skip the Li batteries and install some Lifeline AGMs or similar.

Skiwi said:

TLDR: inverter wired to opposite terminals than rest of loads/inputs on a dual battery setup. Scream foul?

I have a long list of poor decisions I’ve inherited from a well-regarded van building company in a van I purchased from them back in July, and would love some help fixing them!

First off, something I cannot seem to find an answer for anywhere: the system has two li time 200ah batteries wired in parallel, with DC loads and charging inputs on positive of battery no.1 and negative of battery no.2, but the inverter is hooked up to negative of battery no.1 and positive of battery no.2

Is this a big no no? Or should it be fine? It certainly isn’t how I would’ve done it!

(For those curious, I’m still trying to work with company to try and fix the errors so I’ll refrain from naming them for now)

(Never mind the li time battery bms cannot support 3000w, that’s another issue that is hopefully getting solved by the van company by dropping in the ‘plus’ version of the battery with better bms. Oh and the breaker is too small, no bus bars, no battery monitor, undersized cables, no master switch, cheap breakers instead of fuses, unprotected wires, loose connections, wrong charging settings… nightmare fuel!)

Full equipment list:
2x li time 200ah batteries in parallel
3000w Renogy inverter
Renogy Rover Li MPPT
Renogy 40a DC to DC
400W of solar


thanks in advance and sorry for the long read!

Click to expand...

This type of thing is very common in the RV industry. The last one we bought was mostly correct and only a few had to be fixed right.
Hope it works out for you.

HarryN said:

Can you take a few photos of what you have and post the info?

Most people here are quite familiar with the items that you listed, but it might help us to really see what you are dealing with.

As a practical matter, it is common for people to install a larger inverter wattage than batteries can support in case you want to add more capacity in the future.

If you want 2 each batteries in that general size range that will really power that size inverter, the ones that come to mind are the battle born game changers. Not all that many others can do that. 4 each, 100 amp-hr batteries would be a better choice for actually pumping out the required amps if you want to go to another brand.

As far as LiFe batteries in a van in Maine in the winter - seems dicey unless you are going to always keep the van interior above 40 F with a fuel heater - 24 x 7. If you don't plan to keep the van interior warm in the winter, then skip the Li batteries and install some Lifeline AGMs or similar.

Click to expand...

I’ll get some photos up tomorrow once there’s more light out! Although it’s not the tidiest layout, it might be better for me to draw up a quick wiring diagram.

Unfortunately it was enough of a struggle to get the company to agree to order and install the plus version of the batteries we have, which have a 200a bms each which should handle the approx 375a draw of the inverter at 3000w (all rough numbers, bear with me here!). I doubt they would consider getting us some game changers, despite how nice that would be!

As for the cold, our current approach has been running a diesel heater in the van 24/7, as we have an interior water system that also cannot freeze. This keeps the batteries above freezing, and we have managed to avoid any heater failures so far! On the plus side the upgraded li time (now called ampere time) batteries have a low temp charge protection also, as a fail safe. While it’s not battle born or victron, I was hoping this setup would get our foot in the door of vanlife!

Thank you for your time!

Also can I just say this forum has been critical in solving another issue I was having with this system: severely unbalanced cells and incorrect charge profile settings for both the Renogy rover and the dc to dc. Now that those issues have been resolved the system (although still a little flawed) has been working much better! So thanks ya’ll!

12v tank heater pads do wonders for keeping batteries warm. They have their own internal regulator so only turn on when you need them. Hookup to a switch and flip on at wintertime.

I have all 3 victron shunts. Don't get the lynx shunt just get the bmv or smartshunt.

justinm001 said:

12v tank heater pads do wonders for keeping batteries warm. They have their own internal regulator so only turn on when you need them. Hookup to a switch and flip on at wintertime.

I have all 3 victron shunts. Don't get the lynx shunt just get the bmv or smartshunt.

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I actually have a set of these heater pads I was going to install once I discovered the batteries had no low temp charge cutoff! I have held off as supposedly we’re getting new batteries that have a bms which includes a low temp cutoff.

Just put a Victron smartshunt on order! Along with two bus bars to sort out the wiring mess. Luckily I have access to all the correct crimping tools and large diameter wire

Skiwi said:

I actually have a set of these heater pads I was going to install once I discovered the batteries had no low temp charge cutoff! I have held off as supposedly we’re getting new batteries that have a bms which includes a low temp cutoff.

Just put a Victron smartshunt on order! Along with two bus bars to sort out the wiring mess. Luckily I have access to all the correct crimping tools and large diameter wire

Click to expand...

You should still put them on that way you don't need to worry about the temp cutoff and your battery draining.

This plus a Cerbogx and a ruuvi temp sensor on the battery if it's bms doesn't communicate with Victron. Then setup a rule to alert you if battery temp is under 37deg. Never have to think or worry about it unless it tells you. I use rack batteries and put one 67w tank heater sandwiched between 2 batteries and it heats them both. It's 26 out and both sets of my batteries are 44 (in different bays).