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

[DIYrich]

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

He said the opposite.

 

[littleharbor2]

Stacking lugs on a battery terminal is not the best thing to do. Possibly there's not enough threads to properly bolt multiple lugs down so he went to the opposite corners. A better approach would be to install a set of bus bars and separate the batteries while you're at it.

 

[mikefitz]

3000w Renogy inverter
Renogy Rover Li MPPT
Renogy 40a DC to DC

If possible get the installer to replace with better performing devices that will cause less grief, as a minimum replace the Renogy Rover MPPT with a Victron Smart MPPT.

‘plus’ version of the battery

The Li Time plus has no low temperature charge disable built into the BMS, according to available data.


Thus all the chargers will need the ability to monitor battery temperature and charge appropriately.
An alternative would be batteries with self heating option, these divert charge power into built In heaters when the battery is under charge.

 

[henrys]

I would test your batteries with your expected loads before spending a lot of $ changing them out. Hobotech did a pretty thorough test of that battery and was able to sustain 150ah discharge for 5 minutes. In theory to support 3000W each battery needs to support 125A which will probably be fine.

 

[justinm001]

Stacking lugs on a battery terminal is not the best thing to do. Possibly there's not enough threads to properly bolt multiple lugs down so he went to the opposite corners. A better approach would be to install a set of bus bars and separate the batteries while you're at it.

Yes but stacking lugs does work and is perfectly OK. Guys got a budget rig so they cut corners to save money. All still is perfectly safe and works fine provided there's enough room to properly tighten down the bolt on the lugs. Even using both sets of lugs is fine.

Just because it isn't done the best and most expensive way doesn't mean it's wrong.

 

[Texas-Mark]

He said the opposite.

No, he said this:
"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"

There is nothing wrong with that setup, and nothing to indicate anything was actually connected reverse polarity. As already noted, connecting across parallel batteries (i.e. positive to one battery and negative to the other) is actually the prefered way. In this case they just connected the inverter to the opposite ends. Again, nothing wrong with doing that way, and could actually be better for balancing the load to charge (i.e. voltages seen by either).

 

[DIYrich]

He said the opposite.

Nevermind. I re-read and realized he was specifying charger and inverter hookup. I originally read it as one pole of the inverter, and the other pole of the inverter.

 

[littleharbor2]

Yes but stacking lugs does work and is perfectly OK. Guys got a budget rig so they cut corners to save money. All still is perfectly safe and works fine provided there's enough room to properly tighten down the bolt on the lugs. Even using both sets of lugs is fine.

Just because it isn't done the best and most expensive way doesn't mean it's wrong.

Your opinion. I've seen some butt ugly stacks of lugs and terminals. If care isn't taken to prioritize the "stack" it can and will become dangerous. A set of bus bars could be as cheap as two 1 foot pieces of copper pipe and some time fabricating it if the real thing isn't in the budget.

 

[justinm001]

Your opinion. I've seen some butt ugly stacks of lugs and terminals. If care isn't taken to prioritize the "stack" it can and will become dangerous. A set of bus bars could be as cheap as two 1 foot pieces of copper pipe and some time fabricating it if the real thing isn't in the budget.

How can it become dangerous? As long as the lugs have enough surface area and its properly torqued down it doesn't matter how many lugs you have provided you're not overloading the gauge of the terminal.... but then you have the same issue as a bussbar.

I'd suspect proper lugs would actually be better than a bussbar because you have more copper surface area since there'd be lugs above and below. Even my lynx distribution busses only have a small bolt above with a thin washer so it's relying on the power only at the bottom.

It's very normal to see bunches of stacked lugs on even luxury vehicles for common ground

 

[littleharbor2]

It becomes dangerous when an inexperienced person doesn't take your points into consideration and stack smaller flimsy terminal ends UNDER a high current lug like a 4000 watt 12 volt inverter. Not everybody understands the danger.

 

[justinm001]

It becomes dangerous when an inexperienced person doesn't take your points into consideration and stack smaller flimsy terminal ends UNDER a high current lug like a 4000 watt 12 volt inverter. Not everybody understands the danger.

OP is complaining that the van company said they're professionals so I assumed they weren't inexperienced.

Also the dangers of an inexperienced person is the same even with a buss bar and putting a small washer on either side... maybe a zinc or other material that isn't as conductive.

 

[LakeHouse]

I'd suspect proper lugs would actually be better than a bussbar because you have more copper surface area since there'd be lugs above and below.

No. The bolt is not intended to be part of the electrical path. Good bolts (and the washers you should use with them) are made of materials that are not great conductors.
So your electrical path from the the lug to the battery is one direction only, and having other lugs in the way adds resistance to that path. Stacking lugs might be ok in some cases, but it's not going to be better than bus bars.

 

[justinm001]

No. The bolt is not intended to be part of the electrical path. Good bolts (and the washers you should use with them) are made of materials that are not great conductors.
So your electrical path from the the lug to the battery is one direction only, and having other lugs in the way adds resistance to that path. Stacking lugs might be ok in some cases, but it's not going to be better than bus bars.

Take something like a smartshunt though. Isn't the bolt material the same?
In every battery with screw terminals it all appears to be the same material and usually the same piece of metal.

I can see your point in lfp batteries that use screws which seem to be steel

 

[LakeHouse]

Take something like a smartshunt though. Isn't the bolt material the same?

I couldn't say with any certainty. Just because the material looks the same doesn't mean it is the same; a hardened steel or stainless steel bolt could be electroplated or otherwise coated for corrosion resistance and it would still be a lousy conductor.
But even if the material was the same, the path from the backside of a lug to the battery still has (at least) three contact surfaces that current would have to flow through: lug-washer, washer-bolt, bolt-terminal. Whereas the connection from the bottom of the lug to the terminal has only one (edit ---->), unless there are other lugs in the way.

 

[Skiwi]

Again thank ya’ll for your input! As @justinm001 put it correctly, this is a budget rig, and before I went the route of finding a van builder I had designed a very robust victron system to put in a DIY build, but such is life! As the system is set up currently, it cannot sustain more than 1500w before the inverter goes into low voltage cutoff, my guess is because the li time bms can’t supply the required amps. Hence the move to upgrade the bms. @mikefitz if you get on li time’s site, they have a 230ah 200a bms with low temp cutoff, and I wish upgrading everything to victron or similar was an option but for now I’m interested in making do with what I have. Low temp charge cutoff makes sense for my application as the batteries should never get to freezing as that means our entire water system would also be freezing, so that feature is merely a back up in case our heater fails (which I’m sure it will one day!)

For those following: two bus bars and a victron smart shunt are on the way, so at least I can have an idea of SOC instead of relying on the downright miserable Renogy mppt for SOC guesstimates.

I understand I’d have a better performing and more reliable system if the components were to be upgraded, but it’s simply not in the scope of this van. The next van however…

Thanks again everyone! May your watts be flowing!

 

[justinm001]

Again thank ya’ll for your input! As @justinm001 put it correctly, this is a budget rig, and before I went the route of finding a van builder I had designed a very robust victron system to put in a DIY build, but such is life! As the system is set up currently, it cannot sustain more than 1500w before the inverter goes into low voltage cutoff, my guess is because the li time bms can’t supply the required amps. Hence the move to upgrade the bms. @mikefitz if you get on li time’s site, they have a 230ah 200a bms with low temp cutoff, and I wish upgrading everything to victron or similar was an option but for now I’m interested in making do with what I have. Low temp charge cutoff makes sense for my application as the batteries should never get to freezing as that means our entire water system would also be freezing, so that feature is merely a back up in case our heater fails (which I’m sure it will one day!)

For those following: two bus bars and a victron smart shunt are on the way, so at least I can have an idea of SOC instead of relying on the downright miserable Renogy mppt for SOC guesstimates.

I understand I’d have a better performing and more reliable system if the components were to be upgraded, but it’s simply not in the scope of this van. The next van however…

Thanks again everyone! May your watts be flowing!

If youre getting low voltage at the inverter under loads it sounds like wiring issue. Bms should just shut off the batteries

 

[Skiwi]

If youre getting low voltage at the inverter under loads it sounds like wiring issue. Bms should just shut off the batteries

Surely the 200a breaker should pop before wiring issues? Although now I’m saying that, I haven’t checked the connections so that could also be a culprit. Regardless, 3000w draw through the inverter would still be more than what the batteries would be able to supply (I seem to remember needing approximately 375a, where the 2x 100a output of the current batteries wouldn’t fill). However the more I think about it the more it makes sense that it’s a wiring/connections issue resulting in a low voltage cut off. Then again, wouldn’t the inverter see a bms shut off as low voltage anyway?

 

[justinm001]

Surely the 200a breaker should pop before wiring issues? Although now I’m saying that, I haven’t checked the connections so that could also be a culprit. Regardless, 3000w draw through the inverter would still be more than what the batteries would be able to supply (I seem to remember needing approximately 375a, where the 2x 100a output of the current batteries wouldn’t fill). However the more I think about it the more it makes sense that it’s a wiring/connections issue resulting in a low voltage cut off. Then again, wouldn’t the inverter see a bms shut off as low voltage anyway?

1500w at 13v is just over 100a so a 200a breaker isn't close to blowing, even the low voltage would have to be like 5v which likely the cutoff is at 10v.

3000w/13v=230a so a 200a breaker makes sense as the inverter is rated for 3000VA which for induction loads could be as low as 80% so 2600w which at 13v is exactly 200a.

This all makes sense for a budget build. They oversized the inverter to handle AC startup but rated the whole thing at 200a

 

[Skiwi]

1500w at 13v is just over 100a so a 200a breaker isn't close to blowing, even the low voltage would have to be like 5v which likely the cutoff is at 10v.

3000w/13v=230a so a 200a breaker makes sense as the inverter is rated for 3000VA which for induction loads could be as low as 80% so 2600w which at 13v is exactly 200a.

This all makes sense for a budget build. They oversized the inverter to handle AC startup but rated the whole thing at 200a

Thanks for the detailed reply! Makes me feel a little better about the setup, my trust for the build quality of this van has been steadily eroded everywhere I look so at least they appear to have got something (mostly) right. Checking wires and connections just jumped way up on the priority list!

 

[Boomerweps]

I wired my 4 100AH batteries in a similar manner. My 3000 watt inverter draws a lot of power through some thick cables, 2/0 IIRC, with a 200A CB. The other ends of the battery bank connect to my buss bars. Everything else connects via the bus bars, solar controller & the TT 12vdc supply lines. Part of the reason for this was limited lug space on the battery terminals. Two really thick large lugs on one battery terminal. Even still I had to get longer terminal screws.
I read an extended study on battery bank connections and the extra wire connecting to each battery results in various tiny resistances to flow. When you connect only to one end battery, that battery gets the power pulled from first and the flow from the other batteries is less, resulting in unbalanced batteries over time.
By pulling positive and negative from opposite battery bank ends, the different resistance from the connecting cables is somewhat equalized. Similarly when charging.
Www.smartgauge.co.uk/batt.con.html Interconnecting multiple batteries to form one large bank