What invertor?

[Jinglyjangly]

I’m doing up a 1993 vw t4 Autotrail Cherokee , inc replacing the entire electrical system.
I had planned on using an 20 amp dc to dc charger and 2 x 100 lithium batteries with 450 w solar and 2000w inverter.
However Black Friday and see Renology has 3000w inverters at a good price, what sort of input would I need into a 3000w inverter?
Could I run 12v ? Don’t think the old alternator which is around 65 amp output would handle any more than an 20 amp dc to dc charger?

 

[Pudsey Bear]

No exspurt but that sound like a decent enough system for the warmer months, and in winter if you uprated the alternator, it's largely down to how much of the 3kw you would actually use, and how often you drive the van, maybe fit a small one for smaller work like charging phones etc, although some MPPT controllers have a couple of USB sockets fed from the load terminal

 

[Pudsey Bear]

uprated alternator for a 1993 VW T4 - Google Search

 

[Exwindsurfer]

I’m doing up a 1993 vw t4 Autotrail Cherokee , inc replacing the entire electrical system.
I had planned on using an 20 amp dc to dc charger and 2 x 100 lithium batteries with 450 w solar and 2000w inverter.
However Black Friday and see Renology has 3000w inverters at a good price, what sort of input would I need into a 3000w inverter?
Could I run 12v ? Don’t think the old alternator which is around 65 amp output would handle any more than an 20 amp dc to dc charger?

I've ran my van for over 12 years with out a dc to dc charger or mains charger just the alternator + solar and never had a prob.
I've got 400amps of lithium + 600watts of solar.
+ what advantage is a dc to dc charger ?

 

[wildebus]

I've ran my van for over 12 years with out a dc to dc charger or mains charger just the alternator + solar and never had a prob.
I've got 400amps of lithium + 600watts of solar.

+ what advantage is a dc to dc charger ?

DC-DC charger will provide a regulated voltage to the battery and limit the current pulled fom the alternator. potential danger with lithium is it can easily take more current than the Alternator is happy to provide and kill it. And on a 1993 Van, it is a wise precuation (IMO) to avoid overstressing the original parts. Who knows what output the alternator can provide on that age of van? The OP says 65A but that was when it was new 30 years ago! I have had a Transporter Alternator fail when I fitted a split-charge relay to run to a standard 100Ah Lead Acid Leisure Battery - the extra load caused it to fail. Customer not that happy, but that's what can happen (not that unusual at all, and why current limiting can be a good idea).

I’m doing up a 1993 vw t4 Autotrail Cherokee , inc replacing the entire electrical system.
I had planned on using an 20 amp dc to dc charger and 2 x 100 lithium batteries with 450 w solar and 2000w inverter.
However Black Friday and see Renology has 3000w inverters at a good price, what sort of input would I need into a 3000w inverter?
Could I run 12v ? Don’t think the old alternator which is around 65 amp output would handle any more than an 20 amp dc to dc charger?

Be mindful that the bigger the inverter, the more overhead it consumes. So with those products, bigger is NOT better unless you really do need the high output as it is just wasteful.
Also, you should check the batteries and see what they are rated at for continuous current. That will be one hard limit that you cannot exceed.
Take the number, multiply it by two as you have two batteries, then multiply by say 12.8 (approx voltage for lithium) and that will give you a maximum output power for EVERYTHING. so if the batteries are rated at 100A continuous current say, you can draw no more than 100 [A] x 2 [batteries] x 12.8 [V] = 2560Watts without the battery bank disconnecting and you loosing all power. With this example, I would not get anything bigger than a 2000W inverter and in reality it is pretty unlikely you will need more.
Doing well to get 450W of solar on a T4 based motorhome as well.

 

[nabsim]

May, (or may not) be of interest but I watched a video other day where they guy said he was moving away from solar altogether and just using engine/B2B charging. Cant think who it was at the moment but will update if it comes back to me. Big B2B you need big (or multiple) alternators

 

[Jinglyjangly]

Everything is going to be doubled up , so gas oven (existing oven hardly used) and hob and fire ,(One gas fire already but will be replaced but will use chimney already installed from new) diesel heater backup, heaviest use of inverter will be air fryer and microwave and fridge, although I may splash out and get a 3 way fridge as well.

DC-DC charger will provide a regulated voltage to the battery and limit the current pulled fom the alternator. potential danger with lithium is it can easily take more current than the Alternator is happy to provide and kill it. And on a 1993 Van, it is a wise precuation (IMO) to avoid overstressing the original parts. Who knows what output the alternator can provide on that age of van? The OP says 65A but that was when it was new 30 years ago! I have had a Transporter Alternator fail when I fitted a split-charge relay to run to a standard 100Ah Lead Acid Leisure Battery - the extra load caused it to fail. Customer not that happy, but that's what can happen (not that unusual at all, and why current limiting can be a good idea).


Be mindful that the bigger the inverter, the more overhead it consumes. So with those products, bigger is NOT better unless you really do need the high output as it is just wasteful.
Also, you should check the batteries and see what they are rated at for continuous current. That will be one hard limit that you cannot exceed.
Take the number, multiply it by two as you have two batteries, then multiply by say 12.8 (approx voltage for lithium) and that will give you a maximum output power for EVERYTHING. so if the batteries are rated at 100A continuous current say, you can draw no more than 100 [A] x 2 [batteries] x 12.8 [V] = 2560Watts without the battery bank disconnecting and you loosing all power. With this example, I would not get anything bigger than a 2000W inverter and in reality it is pretty unlikely you will need more.
Doing well to get 450W of solar on a T4 based motorhome as well.

its not a standard t4 body, coach built 6 metres of roof. , I’m doing away with skylight at middle and will have room for 3x 150w panels.

 

[Exwindsurfer]

I've a renogy 2000 watt inverter and it runs my airfryer ,induction hod ,1200watt kettle and toaster mind you not all at the same time lolol + I had to upgrade the cables to 70mm as the 35 mm where getting warm.

 

[wildebus]

May, (or may not) be of interest but I watched a video other day where they guy said he was moving away from solar altogether and just using engine/B2B charging. Cant think who it was at the moment but will update if it comes back to me. Big B2B you need big (or multiple) alternators

Your mate Mel looked at the Bluetti "charger 1" (think that is the name?) and said he saw a bunch of folk on-line saying "solar is dead, moving to alternator charging" as if using the Alternator to charge the battery is a novel thing!
I have this feeling that Bluetti have sent these chargers out to some Youtubers and they haven't really understood when you might want charging via the engine (call it alternator charging, B2B charging or split-charging) and when you might want Solar charging.

Most modern alternators will charge at a decent lick. I have 60A of B2B running by default and another 30A kicks in if the voltage gets above a certain point (which will be when the engine is running faster so vehicle is moving faster and alternator is getting more cooling).

 

[wildebus]

Everything is going to be doubled up , so gas oven (existing oven hardly used) and hob and fire ,(One gas fire already but will be replaced but will use chimney already installed from new) diesel heater backup, heaviest use of inverter will be air fryer and microwave and fridge, although I may splash out and get a 3 way fridge as well.

You mention using the Inverter with the Fridge? Is this a 240V compressor fridge? if it is any other kind of Fridge apart from a compressor type, such as the mentioned 3-way fridge, then I would pretty well forget running that on the battery except when it is very sunny in the summer - they are very inefficient electrically.

its not a standard t4 body, coach built 6 metres of roof. , I’m doing away with skylight at middle and will have room for 3x 150w panels.

I did know that Dumping the skylight will be the key for the larger array for that type of array.
Not sure personally if that is the way to go, but each to their own. My approach is to get "in-fill" panels to make the most of the gaps that regular panels won't fit. Doing this I've got 450W of solar on my 4 metres of available roof space while still keeping the large centre skylight, 2 more opening vents and a satellite dish .

 

[merl]

Personally I'd go for the larger inverter. Running power electronics close to their maximum power ratings will shorten their lifespan and if a decent headroom hasn't been allowed in the components it'll probably kill it fairly quickly, better to have a unit idling rather than flogging it's self IMHO.
Standing current will vary between makers, I've measured a 800W inverter at 1.3A standing current which is higher than the 3kW unit I've got at the moment which is just 750mA.
If you're switching the inverter on and off as required then standing current isn't an issue, only if you're having to leave it running continuously to power the fridge would standing current be something to consider.
Modding the fridge thermostat to turn the inverter on only when needed would be a nice hack.

 

[merl]

I've ran my van for over 12 years with out a dc to dc charger or mains charger just the alternator + solar and never had a prob.
I've got 400amps of lithium + 600watts of solar.
+ what advantage is a dc to dc charger ?

Nice to see someone doing the alternator/ lithium thing successfully. Have you measured the alternator charging current? If so, how much does it vary with SOC?

 

[Jinglyjangly]

You mention using the Inverter with the Fridge? Is this a 240V compressor fridge? if it is any other kind of Fridge apart from a compressor type, such as the mentioned 3-way fridge, then I would pretty well forget running that on the battery except when it is very sunny in the summer - they are very inefficient electrically.


I did know that Dumping the skylight will be the key for the larger array for that type of array.
Not sure personally if that is the way to go, but each to their own. My approach is to get "in-fill" panels to make the most of the gaps that regular panels won't fit. Doing this I've got 450W of solar on my 4 metres of available roof space while still keeping the large centre skylight, 2 more opening vents and a satellite dish .

Might have a look at getting infill panels, never heard of them before

 

[Jinglyjangly]

You mention using the Inverter with the Fridge? Is this a 240V compressor fridge? if it is any other kind of Fridge apart from a compressor type, such as the mentioned 3-way fridge, then I would pretty well forget running that on the battery except when it is very sunny in the summer - they are very inefficient electrically.


I did know that Dumping the skylight will be the key for the larger array for that type of array.
Not sure personally if that is the way to go, but each to their own. My approach is to get "in-fill" panels to make the most of the gaps that regular panels won't fit. Doing this I've got 450W of solar on my 4 metres of available roof space while still keeping the large centre skylight, 2 more opening vents and a satellite dish .

Re fridge depends on how much money I have left if skint compressor type if not 3 way

 

[nabsim]

Nice to see someone doing the alternator/ lithium thing successfully. Have you measured the alternator charging current? If so, how much does it vary with SOC?

I am on a USA Sprinter forum and a lot of the people over there just use alternator dumping everything into the battery bank. A lot have something to limit the initial start up.

Bet Jeff never gets battery low enough for it to be a problem lol

 

[wildebus]

I am on a USA Sprinter forum and a lot of the people over there just use alternator dumping everything into the battery bank. A lot have something to limit the initial start up.

Bet Jeff never gets battery low enough for it to be a problem lol

I am just wary of the risk of hurting the alternator (especially if I am fitting kit to someone else's van!)

FWIW, in my own Motorhome, I have my B2Bs configured (3 in total) so they come in (and go off) in a staggered way to avoid a sudden stress on the Alternator.

 

[wildebus]

Re fridge depends on how much money I have left if skint compressor type if not 3 way

very different animals and rarely chosen based on price

Best value by far is 240V Compressor Fridge. Works well in a MH with a bit of a mod to secure the door for travelling.
The 12V Compressor versions are significantly more expensive and are are comparable in price to 3-way fridges. If you do a price-check for a given size of a Thetford or Dometic, you will see only around 10% difference between compressor and 3-way.
You need the battery setup to run a compressor, but installation of a gas fridge is much more involved and more expensive than getting a bigger battery to run the electric one