Help if pos, smart charge issues for my circumstances..

[t0mb0]

2000w only use now and then for off grid microwave and also the travel kettle...

Hmm, even your alternator isn't going to run that alone then. I think you only have two real options (or three if you include give up and use gas for cooking!):

1) Invest in some monster lithium setup, likely not very cost effective for now and then usage.
2) Basically go back to the setup you had before, buy an AGM leisure battery to match your starter and use a simple split charge relay as your T5 had. This has some downsides, your leisure generally won't charge past 80% and charge will swing around between your starter and your leisure when driving depending on what's charged up the most. However, with the engine running your inverter will effectively be able to pull from two AGM batteries (starter and leisure) and the alternator in parallel which is basically what you had before. Make absolutely sure all your wiring and fusing it up to it though, that's a lot of current flowing around!

 

[t0mb0]

Hmm, even your alternator isn't going to run that alone then. I think you only have two real options (or three if you include give up and use gas for cooking!):

1) Invest in some monster lithium setup, likely not very cost effective for now and then usage.
2) Basically go back to the setup you had before, buy an AGM leisure battery to match your starter and use a simple split charge relay as your T5 had. This has some downsides, your leisure generally won't charge past 80% and charge will swing around between your starter and your leisure when driving depending on what's charged up the most. However, with the engine running your inverter will effectively be able to pull from two AGM batteries (starter and leisure) and the alternator in parallel which is basically what you had before. Make absolutely sure all your wiring and fusing it up to it though, that's a lot of current flowing around!

Or a kind of hybrid option, as @Pauly suggested above, which is to link the batteries with a manual switch when you want to use the inverter. This has the advantage that your leisure battery will benefit from the DC-DC charger when driving, but the batteries will equalise charge when you join them - also you'll have to be careful about the order of the switching, if you link them and the start the engine then presumably it'll start the engine partially with the leisure battery and maybe blow some fuses.

 

[Deaky]

What about connecting the inverter to the starter battery and running the engine whilst using it?

 

[t0mb0]

What about connecting the inverter to the starter battery and running the engine whilst using it?

Yeah, that was my original suggestion but I got a bit concerned when a 2000w inverter was mentioned! It would work but you’d have to be careful with your usage that you didn’t flatten the starter as the inverter itself is rated above what the alternator alone can provide.

 

[T6DSGChris]

Think microwave is 700w and need to check kettle but wonders if 1000w invertor would do ok? I just went biggest that would fit previously

 

[t0mb0]

Think microwave is 700w and need to check kettle but wonders if 1000w invertor would do ok? I just went biggest that would fit previously

Ah ok, maybe check the kettle then?

 

[Dellmassive]

2000w inverter = 200A (quick maths)

But thats full load.

AGM battery's can not provide that power for any duration as they will just volt sag.

In you old setup it would have been the alternator providing current via the 140A @ 13.8v, relay plus some power from the old AGM (same setup as me in my previous T5.1)

..


I'm still sticking with twin lithium 100ah battery s and a 50A dc-dc charger as your best, cheapest option.

Or the Roamer 230Ah seatbase battery.

Both options will run a 2000w inverter and give you about 2400wh of power.

Just get the right thing from the off.... Or you might end up like and spend £ks on trying to make it work with relays and twin AGMs etc etc etc..... Been there - done that.


...


The fact is that 2000w on a 12v system will take loads of power.


If you are sure you want to stick with AGMs, then your best best is to stack them in series to make a 24v system.... But then you will need a new 24v inverter and 24v charger..... So again will cost £££££.

 

[t0mb0]

2000w inverter = 200A (quick maths)

But thats full load.

AGM battery's can not provide that power for any duration as they will just volt sag.

In you old setup it would have been the alternator providing current via the 140A @ 13.8v, relay plus some power from the old AGM (same setup as me in my previous T5.1)

..


I'm still sticking with twin lithium 100ah battery s and a 50A dc-dc charger as your best, cheapest option.

Or the Roamer 230Ah seatbase battery.

Both options will run a 2000w inverter and give you about 2400wh of power.

Just get the right thing from the off.... Or you might end up like and spend £ks on trying to make it work with relays and twin AGMs etc etc etc..... Been there - done that.


...


The fact is that 2000w on a 12v system will take loads of power.


If you are sure you want to stick with AGMs, then your best best is to stack them in series to make a 24v system.... But then you will need a new 24v inverter and 24v charger..... So again will cost £££££.

I agree if you chuck enough money at it you can spec a lithium system to do it, but not everyone wants to do that, different people have different spending priorities. The fact remains that the OP was already achieving what he wanted using an old T5 with a cheap battery so I think it’s worth taking some care to see whether we can basically recreate that approach whilst working around the T6 system. We know we basically can by hooking the inverter up to the starter/alternator but we just need to assess the actual current draw carefully to make sure there’s no danger of flattening the starter - to do this we need the wattage of the kettle.

 

[mmi]

the smartpass is im told forcing another 120amps in to the rear...so will prematurely kill rear battery life.

No, the Smartpass does not force 120 Amps charging current into a battery. The Smartpass just could provide maximum of 120 Amps if battery (or a consumer) would accept that kind of current. It's the battery's charge acceptance which limits and regulates the current. Thus second battery would get actually the same charging treatment as starter battery.

Neither none of the DC-DC chargers force (their advertised maximum) current into the battery. It's the battery which decides how much to draw.

The Smartpass is not a charger as such - it's basically just a smart split charge relay. Thus the second battery is effectively in parallel with starter battery (and alternator) - when engine is running and charging.

An example of a battery's charge (current) acceptance behaviour - T6 starter battery immediately after engine cranking and then ticking over. Starter battery draw (green) peaks at 89 Amps but already after 20 seconds has dropped to 40 Amps - in spite of voltage staying at 14.7 Volts (red).

 

[T6DSGChris]

kettle wattage is...550-650w

according to mmi's theorem (word of the day).... the smartpass should sort this... but then many "experts" say not...
so hard work sorting this....
i do not like the idea of going crazy on cost due to it used to work for a 20 quid relay, i think thats what annoys me.
I oculd go crazy and if i know...fixed i dont mind... rather not spend a grand on a battery for a 5 thousand mile 18 plate if im honest..
spends more time parked up..

 

[mmi]

it used to work for a 20 quid relay,

Well, you could use the relay also on T6 - if you have Climatic AC and...

keep the blower at 2 or higher setting. This effectively disables the smart charging keeping alternator's charging voltage at 13.4 Volts or higher (regenerative braking, freezing temperatures) - thus keeping starter battery fully charged.

 

[Salty Spuds]

I had a T5.1 non smart alternator with a factory 2nd battery. It was my work van & I kitted it out with kettle/microwave & 1600W inverter fed from the 2nd battery. All great in theory, however, best laid plans & all that. I found that the voltage drop from the 2nd battery caused the inverter to shut down. No problem, run the engine, this cured the under voltage, but, the problem now was the alternator was feeding in at 14V+, so nothing was being drawn from the 2nd battery, the alternator was supplying the whole load to the inverter. This meant that 150A+ was flowing down the cable from the alternator to the 2nd battery. The main 90A fuse popped and the insulation was starting to melt on the supply cable. The solution was to fit a B2B (Sterling 1230) in order to limit the current from the alternator & force the 2nd battery to supply the current to the inverter. I still had to run the engine in order to get the voltage up & supplement the battery current.
Just food for thought.