Hi guys I'm installing the above mentioned inverter in my camping trailer. 

*  Is 10mm² cable overkill (max 3.5m long)? 

*  Do I need to fuse the + close to battery? 

*  I have two 105ah batteries in parallel. Do I just connect + & - to one of the batteries or to + on one battery and - on the other?

Stay safe guys 

10mm2 is a good choice, unless you plan on running near 375W all the time, then you should go bigger and/or shorter distance. (10mm2 =~0.19V drop per 3.5m per leg at 375W)

You should definitely fuse close to the battery.

+ to +; - to -

Edited March 27, 20205 yr by P1000

19 minutes ago, P1000 said:

+ to +; - to -

In this game understanding parallel and series is essential, so I usually advise people to make sure they understand the basics... and to consider delegating the task if it seems a bit daunting 🙂

The next step is to explain the cross-take-off method to ensure balanced charging and discharging. That is, you connect the batteries negative to negative and positive to positive (parallel in other words), but then your inverter's negative cable connects to the negative of the first battery, but your inverter's positive able connects to the positive terminal of the OTHER battery. If you don't do that, then one of the batteries have a longer total cable length and will do less work and receive less charge current.

In this particular case I would earth the negative of the battery to the trailer and fuse the positive side close to the battery. If you don't earth the battery negative, then you must fuse both positive and negative of the battery to protect against double earth-fault conditions.

1 minute ago, plonkster said:

make sure they understand the basics

I remember when I was around 14 years old an older gentlemen helped us to jump-start a car. When it would not start, he said "we can give it 24V for a short time, just pull off the clamp the moment it starts!", and he walked around and started his big old Land Cruiser.

He was convinced that when the engine is running, the battery voltage doubles to 24V, and all we had to do to avoid damage is pull the clamp once the other car starts.

Thankfully smart-ass 14-year old me kept his mouth shut that day 🙂

39 minutes ago, plonkster said:

In this game understanding parallel and series is essential, so I usually advise people to make sure they understand the basics... and to consider delegating the task if it seems a bit daunting 🙂

The next step is to explain the cross-take-off method to ensure balanced charging and discharging. That is, you connect the batteries negative to negative and positive to positive (parallel in other words), but then your inverter's negative cable connects to the negative of the first battery, but your inverter's positive able connects to the positive terminal of the OTHER battery. If you don't do that, then one of the batteries have a longer total cable length and will do less work and receive less charge current.

In this particular case I would earth the negative of the battery to the trailer and fuse the positive side close to the battery. If you don't earth the battery negative, then you must fuse both positive and negative of the battery to protect against double earth-fault conditions.

Hi Plonkster. 

Thanks for your reply. My batteries in Trailer are connected positive to positive and negative to negative (parallel) then one battery positive and the other battery negative goes to my HCDP panel. 

I will connect inverter to one battery positive and negative to the other battery. 

One more question.... One of the battery's negative is grounded to trailer body. I want to connect inverter negative on the other battery (negative not grounded) due to lack space on the negative terminal of the battery that is grounded. Will this be OK? 

Oh and what size fuse do you recommend? 

Regards 

Edited March 27, 20205 yr by Peyper
Had to add more detail

1 hour ago, Peyper said:

Oh and what size fuse do you recommend? 

I would install a 35-40Amp fuse. 

 

2 hours ago, P1000 said:

10mm2 is a good choice, unless you plan on running near 375W all the time, then you should go bigger and/or shorter distance. (10mm2 =~0.19V drop per 3.5m per leg at 375W)

I dont understand this. The max draw will be  31.25 amp. Over 3.5 meter the volt drop on a 10mm cable will be .167V or 1.39%. SANS allow for 5% volt drop and in Solar/DC we aim to keep it below 3%. This is way within spects. The max allowed constant amperage through a 10mm is 50A. 

Why would he need a bigger cable for this inverter if he runs it close to max rating?

1 hour ago, Peyper said:

One of the battery's negative is grounded to trailer body

That's fine. The ground strap just needs to be sized to handle as much current as it would take for the fuse on the positive side to blow.

Thanks Guys.

 

Stay safe! 

On 2020/03/27 at 10:22 AM, plonkster said:

In this game understanding parallel and series is essential, so I usually advise people to make sure they understand the basics... and to consider delegating the task if it seems a bit daunting 🙂

The next step is to explain the cross-take-off method to ensure balanced charging and discharging. That is, you connect the batteries negative to negative and positive to positive (parallel in other words), but then your inverter's negative cable connects to the negative of the first battery, but your inverter's positive able connects to the positive terminal of the OTHER battery. If you don't do that, then one of the batteries have a longer total cable length and will do less work and receive less charge current.

In this particular case I would earth the negative of the battery to the trailer and fuse the positive side close to the battery. If you don't earth the battery negative, then you must fuse both positive and negative of the battery to protect against double earth-fault conditions.

Hi Plonkster. 

Thanks for your reply. My batteries in Trailer are connected positive to positive and negative to negative (parallel) then one battery positive and the other battery negative goes to my HCDP panel. 

I will connect inverter to one battery positive and negative to the other battery. 

One more question.... One of the battery's negative is grounded to trailer body. I want to connect inverter negative on the other battery (negative not grounded) due to lack space on the negative terminal of the battery that is grounded. Will this be OK? 

 

Regards